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Advanced Functional Materials

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Online ISSN: 1616-3028
Discipline: Materials Science
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Firmly established as a top-tier materials science journal, Advanced Functional Materials reports breakthrough research in all aspects of materials science, including nanotechnology, chemistry, physics, and biology every week.

Advanced Functional Materials is known for its rapid and fair peer review, quality content, and high impact, making it the first choice of the international materials science community.

 

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a) The chemical structure of MTTCM with D, π, and A motifs. b) Absorption (black) and photoluminescence (bule) spectra of MTTCM in tetrahydrofuran (THF). c) Fluorescence decay profiles of MTTCM in solid state. d) Plots of the relative emission intensity (I/I0) of MTTCM versus water fraction. e) Size distributions of MTTCM nanoparticles (NPs) measured with dynamic laser scattering (DLS; Insert: transmission electron microscope (TEM) image of MTTCM NPs, scale bar: 200 nm, DPI: Polymer dispersity index). f) Absorption (black line) and photoluminescence (blue line) spectra of MTTCM NPs in water.
3‐photon excitation properties of MTTCM nanoparticles (NPs). a) Measured fluorescence signals vs. excitation power on the sample (circles) plotted on the log scale, at excitation wavelengths of 1600, 1700, and 1800 nm. Solid lines are linear fits to the experimental data. b) Measured wavelength‐dependent 3‐photon action cross‐section (ησ3) for MTTCM NPs covering the NIR‐III. c) Measured normalized 3‐photon emission spectrum (red) and one‐photon emission spectrum (black) for MTTCM NPs. d) 3‐photon fluorescence image of the blood vessel labeled by MTTCM NPs. e) Zoomed‐in area in part d for measuring the 3‐photon emission spectrum. f) Measured 3‐photon emission spectrum of MBBTD NPs corresponding to part e in the circulating blood (red) and in PBS in vitro (black).
a) 3PM images and 3‐dimensional (3D) reconstruction of the mouse brain vasculature through a cranial window. Red: brain vasculature labeled by MTTCM nanoparticles (NPs); green: third‐harmonic‐generation (THG) signals from white matter (WM) layer. Expanded 3D stacks showed the relative position for the white matter. b–e) 2D images of the brain vasculature at the depths of 900 µm (b, in the WM), 1200 µm (c, in the hippocampus), 1500 µm (d, in the hippocampus) and 1800 µm (e, in the hippocampus). f–i) Profiles and signal‐to‐background ratio (SBR) analysis of the brain vessels marked in (b–e) displayed on semi‐log scales. Scale bars: 50 µm.
a) 3‐photon microscopy (3PM) images and 3‐dimensional (3D) reconstruction of a mouse brain vasculature through the intact skull. Red: brain vasculature labeled by MTTCM nanoparticles (NPs); Green: third‐harmonic‐generation (THG) signals from skull layer. Expanded 3D stacks showed the thickness of the skull. 2D images of the brain vasculature at the depths of b) 465 µm, c) 765 µm, d) 975 µm, and e) 1030 µm beneath the skull. f–i) Profiles and signal‐to‐background ratio (SBR) analysis of the brain vessels marked in (b–e) displayed in logarithmic plots. Scale bars: 50 µm.
In vivo 3‐photon fluorescence imaging of a mouse brain blood vessels through the intact skull for blood flow speed measurement. 2D images of brain blood vessels at imaging depth of a) 360 µm and d) 752 µm beneath the skull (scale bar: 50 µm). b,e) 2D image of the selected blood vessel (in a and d) under 5× magnification (scale bar: 10 µm). c,f) Line scan image along the dashed line corresponding to part b and part e for measuring blood flow speed ν (ν = ∆x/∆t, ∆x: x pixel × 54 µm/512 pixel, ∆t: t line × 2 ms line⁻¹, scale bar: 10 µm). Pixel size: 512 × 512.
Article
Fluorophores lay the material basis for tissue labeling and fluorescence imaging, especially for deep‐brain multiphoton microscopy (MPM) in animal models. Among various fluorescent materials, those with aggregation‐induced emission (AIE) characteristics, i.e., AIEgens, have excellent optical properties and biocompatibility and thus have found widespread applications in biomedical imaging. However, their application to deep‐brain MPM has so far been limited in imaging depth, which undoubtedly poses a hindrance to neurological research aiming to probe the deeper brain. In order to address the issue, here a novel bright AIEgen, namely MTTCM, is designed and synthesized via facile reactions routes. The self‐assembled MTTCM nanoparticles (NPs) with their water‐dispersible feature, have good biocompatibility and good photostability. Furthermore, they are spectrally advantageous for deep‐brain MPM: their emission lies in the NIR‐I region, they generate 3‐photon fluorescence with NIR‐III excitation and show only a slight blue‐shift in the emitted 3‐photon fluorescence in vivo. From a fundamental photochemical perspective, it is also confrimed that MTTCM NPs obey Kasha's rule since the measured 3‐photon and 1‐photon fluorescence spectra overlap. All these merits make MTTCM NPs the enabling fluorophores for record depth in brain imaging in vivo: 1905 µm after craniotomy and 1100 µm through an intact skull, excited at 1660 nm. Furthermore, a record 752 µm hemodynamic imaging depth before craniotomy is demonstrated, from which the blood flow speed can be measured. MTTCM NPs are thus promising fluorophores for deep‐brain 3‐photon imaging in vivo.
 
Illustration of the chiral‐sensing operating mechanism via an upconverting chiral metamaterial. a) Chiral selective upconversion photoluminescence (UCPL) excited upon LCP and RCP near‐infrared excitation. Two enantiomers are identified by comparing the intensity of UCPL, where the intensity difference stems from the different circular dichroisms of each enantiomer at the wavelength of 980 nm. b) Schematic illustration of the core–shell–shell upconversion nanoparticles, which are embedded in the chiral meta‐structure. The upconversion nanoparticles convert the near‐infrared light to visible light through multiphoton absorption. c) Schematics of chirality transfer and the chiral interaction mechanism. The transferred chirality from the chiral molecule to the plasmonic platform further interacts with the intrinsic chirality of the chiral metamaterial. The total CD of the system is modified due to the chiral‐chiral interactions. d) Illustrations of the CD difference of the UCMM device, which are produced by the chiral interactions.
Design and numerical calculation of the UCMM. a) Schematic illustration of the UCMM device overlaid with the relative orientations of the normalized electric (p, blue arrow) and magnetic (m, red arrow) dipole moments upon excitation with RCP light at a wavelength of 980 nm. Geometrical parameters: P = 400 nm, JL = 195 nm, JR = 230 nm, JB = 270 nm, and JW = 70 nm. b) Calculated CD spectrum of the metamaterial from the differential absorption (black) and interaction of both dipole moments (red) of LCP and RCP light. c) Field profile of the electric field enhancement (top) and chiroptical field enhancement (bottom) under RCP/LCP light at a wavelength of 980 nm. The chiral metamaterial design possesses a strong enhancement for both the electric field and chiroptical field under RCP excitation. d) Schematic illustration of the UCMM device and the chiral molecule that are represented by the electric and magnetic dipoles. The chiral interaction between the transferred chirality and intrinsic chirality of chiral metamaterial forms the net dipole moments. e) Numerical estimation of the UCMM device with D‐ or L‐type chiral molecules. The imaginary κ was used to capture the circular dichroism of the system.
Experimental demonstration and optical characterization of the UCMM device. a) Scanning electron microscope image of the UCMM device. The scale bar represents 250 nm. b,c) Measured and calculated linear spectral responses of the UCMM device. A strong CD response was exhibited around a wavelength of 980 nm. d) Transmission electron microscopy image of core‐shell–shell upconversion nanoparticles which are embedded in the chiral metamaterials. The scale bar represents 50 nm. e) Upconversion photoluminescence spectrum of the UCMM device under 980 nm light excitation of 40 W cm⁻². The intensity of the spectrum was acquired by subtracting the photoluminescence intensity of the LCP excitation from the RCP excitation. f) Excitation power density dependence of 657 nm (red), 545 (green), and 452 (blue) emission of the upconverting chiral metamaterials. Below the power density of 40 W/cm² is defined as the nonlinear regime as it requires multi‐photon absorptions (n > 1) to emit the upconverted light, while above the power density of 40 W cm⁻² is defined as the linear regime (n < 1) as the single‐photon excitation dominates the upconversion process.
Enantiomer‐selective molecular sensing. a) Characterized CD of the chiral molecule/metamaterial hybrid system. The inset shows a zoom‐in around the wavelength of 980 nm. b) CD difference between the D‐ and L‐Glucose in the hybrid system, while varying the molecular concentration of the chiral solution. c) Characterized upconversion response of the chiral molecule/metamaterial hybrid system by varying the excitation power density. The ∆UCPL‐CD was defined by the difference in the UCPL intensity of each hybrid system (D‐/L‐) and the averaged intensity of both UCPL intensity. d) ∆UCPL‐CD at the emission wavelength of 657 nm of the hybrid system. The error bars indicate the standard deviation.
Molarity survey at the nonlinear (40 W cm⁻²) and the linear (160 W cm⁻²) region. a) Characterized upconversion response of the chiral molecule/metamaterial hybrid system in the nonlinear regime by varying the molar concentration of the chiral solutions. b) The ∆UCPL‐CD at the emission wavelength of 657 nm of the hybrid system in the nonlinear regime. c) Characterized upconversion response of the chiral molecule/metamaterial hybrid system in the linear regime by varying the molar concentration of the chiral solutions. d) The ∆UCPL‐CD at the emission wavelength of 657 nm when characterized in the linear region.
Article
Enantiomers are chiral isomers in which the isomer's structure itself and its mirror image cannot be superimposed on each other. Enantiomer selective sensing is critical as enantiomers exhibit distinct functionalities to their mirror image. Discriminating between enantiomers by optical methods has been widely used as these techniques provide nondestructive characterization, however, they are constrained by the intrinsically small chirality of the molecules. Here, a method to effectively discriminate chiral analytes in the nonlinear regime is demonstrated, which is facilitated by an upconverting chiral plasmonic metamaterial. The different handedness of the chiral molecules interacts with the chiral metamaterial platform, which leads to a change in the circular dichroism of the chiral metamaterial in the near‐infrared region. The contrast of the circular dichroism is identified by the upconverted signal in the visible region.
 
Article
Different therapeutic nucleic acids (TNAs) can be unified in a single structure by their elongation with short oligonucleotides designed to self‐assemble into nucleic acid nanoparticles (NANPs). With this approach, therapeutic cocktails with precisely controlled composition and stoichiometry of active ingredients can be delivered to the same diseased cells for enhancing pharmaceutical action. In this work, an additional nanotechnology‐based therapeutic option that enlists a biocompatible NANP‐encoded platform for their controlled patient‐specific immunorecognition is explored. For this, a set of representative functional NANPs is extensively characterized in vitro, ex vivo, and in vivo and then further analyzed for immunostimulation of human peripheral blood mononuclear cells freshly collected from healthy donor volunteers. The results of the study present the advancement of the current TNA approach toward personalized medicine and offer a new strategy to potentially address top public health challenges related to drug overdose and safety through the biodegradable nature of the functional platform with immunostimulatory regulation.
 
Article
Bacterial biofilms are composed of a consortium of bacteria that communicate with each other through quorum sensing. Therefore, bacteria can form an extracellular matrix, which is a mucus composed of exopolysaccharides, peptidoglycans, and extracellular DNA, through these communication molecules. The matrix protects the community of bacteria from the adverse effects of the external environment, including antibiotics, biocides, and eradicating agents. Self‐propelled functional microrobots offer great promises in the biomedical field. The self‐propelled microrobots represent an innovative platform in microrobotic research, aiming to have an important role in the biomedical field. One of the potential applications is removal of bacterial biofilms. Herein, the specific design of multifunctional microrobots is demonstrated using antimicrobial‐designed peptides for eradication of methicillin‐resistant Staphylococcus aureus (MRSA)‐produced biofilms. The designed microrobots can perform various tasks, including autonomous navigation toward bacterial cells, mechanical entry into bacterial biofilms, and blockage of the replication of bacterial DNA by indolicidin peptides. The implemented design extends the microrobot applications not only to the removal of biological aggregates but also to the delivery and release of drugs or even target manipulation, demonstrating their great potential for use in biomedical research.
 
Article
Cutaneous melanoma is the deadliest malignant skin cancer due to its poor prognosis, rapid local growth, and high metastasis. Transdermal administration for local drug delivery would be one of the most appropriate therapy regimens. However, promoting drug penetration into deep tumor tissue and maintaining the balance of redox homeostasis during the antitumor treatment to inhibit melanoma progression remains a great challenge in melanoma treatment. Herein, non‐invasive transdermal delivery systems are reported for melanoma treatment, which is composed of biocompatible hydrogel and penetrating nanocarriers. Highly penetrating nanocarriers can co‐deliver paclitaxel and coenzyme Q10 for inhibiting melanoma and reducing side effects, which are attributed to drug encapsulation, deep tissue penetration, high cellular uptake, and organelle targeting. More importantly, biocompatible hydrogels serve as nanocarriers platforms for melanoma location and transdermal delivery. This hierarchical nanoparticle‐hydrogel system achieves high‐efficiency non‐invasive transdermal delivery for inhibiting melanoma, blocking adverse effects, and restraining melanoma development.
 
Article
The development of organic thermosensitive fluorophores for use in heat‐resistant organic light emitting diodes (OLEDs) and large‐area and flexible high‐temperature sensing remains challenging due to the susceptibility of such materials to thermally facilitated nonradiative decay. A series of “hot exciton” materials (“C1” and “C2”) based on pyrrole‐substituted triarylphosphine oxides that exhibit high heat resistance have been developed. At a temperature of 260 °C, the films retain 42% (C1) and 29% (C2) of their room temperature fluorescence. This is thanks to thermally facilitated reverse intersystem crossing (RISC) from a high‐lying triplet to a singlet state. By combining the novel fluorophores with a yellow emitter with an extremely large Stokes shift, flexible and large‐area ratiometric film thermometers are fabricated that demonstrate naked‐eye high‐temperature sensing. The relative sensitivity, Sr, of the film thermometer is higher than 1% K–1 in the high‐temperature region (393 to 470 K), with the maximum Sr reaching 1.26% K⁻¹ at 430 K. Using these blue emitters, heat‐resistant cyan and white OLEDs are also fabricated. With thermally populated singlets and nearly 100% exciton harvesting via fast RISC, the C1‐based cyan OLED exhibits a nearly 12‐fold enhancement in electroluminescence on heating from room temperature to 530 K, while the corresponding white OLED displays a 5.7‐fold electroluminescence enhancement.
 
Article
With the rapid progress in nanomaterials and biochemistry, there has been an explosion of interest in biomolecule‐modified quantum dots (QDs) for biomedical applications. Metal chalcogenide quantum dots (MCQDs), as the most widely studied QDs, have attracted tremendous attention in the biomedical field on account of their unique and excellent optical properties and the ease of biomolecular modifications. Herein, important advances in MCQDs over recent years are reviewed, from materials design to biomedical applications. Especially, this review focuses on the challenges encountered in the applications of MCQDs in biomedical fields and how these problems can be solved by rational design of synthesis methods and modifications, which have opened a universal route to develop the functionalized MCQDs. Moreover, recent processes in bioimaging, biosensing, and cancer therapy based on MCQDs are examined, including the rapid detection and diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). This review provides broad insights into MCQDs in the biomedical field and will inspire material researchers to develop MCQDs in the future.
 
Article
Persistent bacteria, such as intracellular and biofilm bacteria, are critical challenges in clinic treatment because they are refractory to antibiotics management under the shelter of cytomembrane and biofilm. Conventional strategies to combat intracellular bacteria are using high doses of antibiotics, which may bring the risk of drug resistance, and debridement of the biofilm increases patients’ pain and economic burden. Currently, the use of antibiotics is irreplaceable and it is necessary to develop new strategies to enable common antibiotics to penetrate the cytomembrane and biofilm, and then kill the bacteria. Hence, a nanoscale gallium‐based metal–organic framework (GaMOF) nanoparticles that can stride across cell membranes as antibiotics carriers, disable the biofilm via disrupting bacteria Fe metabolism, and enhance the antibiotic potency for the two intractable germs is constructed. The synthesized GaMOF exhibits a high BET surface area of up to 1299.53 m² g⁻¹, uniform particle size of ≈100 nm, monodispersed spherical morphology with virus‐like surfaces, and good biosafety. The nano MOF structure and Ga intrinsic inhibiting bacteria activity armored antibiotics as “super‐penetrating bombs” to eradicate the two types of elusive bacteria. Moreover, intracellular bacteria‐induced pyroptosis and associated inflammation in vivo are alleviated by GaMOF and cured by GaMOF united with antibiotics treatment.
 
Article
Side chain engineering is a widely explored strategy in the molecular design for non‐fullerene acceptors (NFAs). Although the relationship between side chain structures and optoelectronic properties of NFAs is well clarified, the effect of side chain structures on the stability of NFAs and their corresponding organic solar cells (OSCs) is rarely reported. Herein, a series of Y‐family NFAs with varying side‐chains are studied to investigate their degradation upon multiple stresses including water, oxygen from ambient, chemical environment from ZnO electron transport layer, temperature, and ultraviolet light. The results show that all of these Y‐family NFAs are highly stable against water and oxygen in ambient dark condition, while their photochemical and thermal stabilities decrease with the increasing side chain length. NFAs with shorter side chains are not only more resistant to photo‐oxidation and photocatalytic reactions, but also can hamper the formation of large phase‐separated NFA domains upon storage in both glovebox and ambient conditions. As such, the PM6:NFA OSC with short side‐chain NFA also exhibits superior operational stability, associating with a higher T80 lifetime. This study demonstrates that the side chains must be considered to obtain stable OSCs.
 
Article
The exceptional stiffness and toughness of double‐network hydrogels (DNHs) offer the possibility to mimic even complex biomaterials, such as cartilage. The latter has a limited regenerative capacity and thus needs to be substituted with an artificial material. DNHs composed of cross‐linked poly(2‐oxazoline)s (POx) and poly(acrylic acid) (PAA) are synthesized by free radical polymerization in a two‐step process. The resulting DNHs are stabilized by hydrogen bridges even at pH 7.4 (physiological PBS buffer) due to the pKa‐shifting effect of POx on PAA. DNHs based on poly(2‐methyl‐2‐oxazoline), which have a water content (WC) of around 66 wt% and are not cytotoxic, show biomechanical properties that match those of cartilage in terms of WC, stiffness, toughness, coefficient of friction, compression in body relevant stress conditions and viscoelastic behavior. This material also has high strength in PBS pH 7.4 and in egg white as synovial liquid substitute. In particular, a compression strength of up to 60 MPa makes this material superior.
 
Morphology and composition characterization of the 6‐HENs/PC (PtFeCoNiCuZn) sample. a,b) TEM images, c) high‐angle annular dark‐field (HAADF)‐STEM image, d) size distribution histogram, e) HRTEM images; f) HAADF‐STEM image and the corresponding EDS mappings of elemental Pt, Ni, Fe, Cu, Co, and Zn.
Physical characterization of the 6‐HENs/PC (PtFeCoNiCuZn) and Pt/C samples. a) XRD patterns; b) Pt 4f XPS spectra; c–e) N2 adsorption–desorption isotherms, pore‐size distribution plots, and pore parameters. The insets in (b) and (d) are the amplification of the regions circled by yellow. * For commercial Pt/C, its mesopores size is determined from the pore size distribution plot and macropores size is acquired from the TEM image.
TEM images and EDS elemental mappings of a) 7‐HENs/PC (PtRuIrFeCoNiCu), b) 8‐HENs/PC (PtRuIrFeCoNiCuZn), and c) 10‐HENs/PC (PtRuIrRhFeCoNiCuZnSn). d) The involved elements in HENs and their different physiochemical properties.
Electrocatalysis of ORR by alloy catalysts and commercial Pt/C. a) CV curves; b) ORR polarization curves measured from 0 to 1.1 V; c) mass activities and specific activities; d–f) ORR polarization curves and mass/specific activity before and after 5000 cycles between 0.6 and 1.1 V; g) HAADF‐STEM image of 6‐HENs/PC after 5000 cycles test and the corresponding EDX mappings. Particularly, the Pt loading on the rotating disk electrode is 6.9 µgPt cm–2 for all catalysts.
Schematic illustration of the HENs–carbon interfaces made by a) physical mixing and b) anchoring‐carbonization strategy.
Article
Immobilizing ultrafine high‐entropy Pt alloy nanocrystals (HENs) in porous carbon (PC) with strong interface interaction, which is crucial to efficient and durable oxygen reduction reaction (ORR), remains a challenge. In this work, an anchoring‐carbonization strategy for strongly bonding sub‐3 nm HENs in ordered mesoporous carbon is reported. When heating the orderly assembled composites containing hydrophobic organometallic precursors, structure directing agent F127, and hydrophilic resol, F127 is first removed at moderate temperature region, leading to reduced metallic species directly anchored on partially carbonized resol framework. Then along further temperature increase, in situ carbonization of resol around the HENs, enables more effective plane bonding rather than a single point contact of HENs with carbon. It not only enhances the anchor strength, but also inhibits migration and size growth of HENs along the subsequent high‐temperature carbonization. As a result, senary, septenary, octonary, and denary Pt‐based HENs with average nanocrystal sizes of 2.2, 2.6, 2.9, and 2.8 nm, respectively, are successfully imbedded into porous carbon. In electrocatalytic ORR, porous carbon‐supported senary Pt‐based HENs (6‐HENs/PC) exhibit superior activity and durability, representing a promising electrocatalyst. This strategy allows for the preparation of a range of ultrafine HENs strongly loaded on porous carbon for wide applications.
 
Article
Ferroelectric semiconductors represent an exciting branch of new‐generation optoelectronic devices. However, regarding severe polarization deterioration caused by leakage current, it is challenging to couple ferroelectricity and semiconductive properties in a single‐phase material. The first quadrilayered ferroelectric semiconductor of 2D homologous perovskites, IA2Cs3Pb4Br13 (IA = isoamylammonium), showing distinctive ferroelectric characteristics of symmetry breaking at 351 K and large polarization of 4.2 µC cm‐2 is presented here. The design strategy of increasing layer‐number endows higher Curie temperature and superior semiconductor merits than other lower‐layered members (IA2Csn‐1PbnBr3n+1, n = 1–3). Bulk photovoltaic effects in IA2Cs3Pb4Br13 result in a notable dichroism up to ≈1.2 for self‐driven polarized‐light detection. This unprecedented work opens an avenue toward the targeted performance optimization of electric‐ordered functional materials.
 
Schematic of the stereo U‐pillar and the corresponding simulated results. a) Schematic of the proposed all‐gold U‐pillar. b,c) Simulated amplitude reflection spectra |rxx| and |ryy| under the x‐LP and y‐LP normal incidences. d) Simulated phase difference spectra Δφ = φyy ‐ φxx. e,f) Simulated phase shift spectra φxx and φyy under the x‐LP and y‐LP normal incidences. The former and latter subscripts represent the detected and incident polarizations. The same hereinafter.
Simulated electric field distributions and CMT fitting parameters. ab) Simulated electric field and surface current distributions of the sole periodic unit structure at the resonance frequencies of 0.53 and 1.37 THz under the x‐LP incidence with d = 70 µm, in the planes of y = 0 µm, z = 147 µm, and z = 53.5 µm. c) Theoretically fitted parameters γ1, γ2, and g as a function of d under the x‐LP normal incidence using the CMT.
Simulated and measured results of the U‐pillar metasurface with half‐wave plate feature. a,b) Simulated reflection amplitude and phase spectra of the U‐pillar metasurface with half‐wave plate feature under the x‐LP and y‐LP normal incidences. c,d) Simulated reflectance and PCR spectra under the CP normal incidences. e–h) Corresponding measured results with respect to (a)–(d). The inset in e) shows the partial SEM image of the fabricated metasurface.
Performance of the U‐pillar half‐wave plate metasurface under oblique incidences. a) Schematic of the oblique incidence of the U‐pillar half‐wave plate metasurface. b–e) Simulated reflection amplitude spectra |r++|, |r−+|, |r+−| and |r−−| as the incident angle β varies from 0° to 85° in the ϕ = 45° plane, respectively. f–i) Corresponding measured results as the incident angle β varies from 15° to 85°.
PB phase control and meta‐grating. a) Schematic of the rotating U‐pillar. b,c) Simulated amplitude reflection |r++| and phase shift φ++ spectra under normal incidences at different θ. d) Partial SEM image of the fabricated meta‐grating for spin decomposition. e,f) Measured |r++| and |r−−| as a function of deflection angle η from −80° to −20° and 20° to 80°, respectively. The inset dashed lines are calculated results based on the generalized Snell's law.
Article
Efficient and flexible manipulation of terahertz (THz) polarization in a broadband manner using metasurfaces has attracted continuous attention in recent years. Previous studies have commonly applied multilayer metallic resonators or bonded dielectric structures as the basic units, which are affected by the spacer loss or bonding difficulty and stability. Here, a new design scheme is proposed based on an all‐metal stereo U‐shaped meta‐atom working in a reflection configuration. The stereo metasurface functions as an efficient and broadband THz waveplate with tailorable birefringence simply controlled by the sunken depth. Such an intriguing property is experimentally verified by a reflection‐type THz half‐waveplate. The polarization conversion ratio is higher than 90%, with 69% relative bandwidth and over 85° angle tolerance for incidence. Furthermore, an efficient and broadband meta‐grating based on the Pancharatnam–Berry phase method is also experimentally demonstrated. The proposed strategy enriches the design degrees of freedom of polarization‐related metasurfaces and may find broad applications in realizing various functional devices.
 
Article
Soft robotic devices containing multiple actuating elements have successfully recapitulated complex biological motion, leading to their utility in biomedical applications. However, there are inherent nonlinear mechanics associated with soft composite materials where soft actuators are embedded in elastomeric matrices. Predicting their overall behavior prior to fabrication and subsequent experimental characterization can therefore present a hurdle in the design process and in efficiently satisfying functional requirements and specifications. In this work, a computational design framework for optimizing the motion and function of biomimetic soft robotic composites is demonstrated by conducting a design case study of soft robotic cardiac muscle (myocardium) with a particular focus on applications including replicating and assisting cardiac motion and function. A finite element model of a soft robotic myocardium is built, in which actuators are prescribed with anisotropic strain to simulate local deformation, and various design parameters are investigated by evaluating the performance of each configuration in terms of ventricular twist, volumetric output, and pressure generation. Then, an optimized design is proposed that recapitulates the physiological motion and hemodynamics of the heart, and its thrombogenicity is further explored using a fluid‐structure interaction model. This framework has broader utility in predicting the performance of other soft robotic embedded composites.
 
Article
Due to the inherent brittleness and low mechanical strength, it is still a challenge for calcium phosphate (Ca‐P) ceramics to be used in load‐bearing bone defect repair. To achieve a good balance between mechanical strength and osteogenic activity, hollow‐tube‐whisker‐modified biphasic calcium phosphate (BCP) ceramics (BCP‐HW) are successfully fabricated by an in situ growth process in the present study. Compared to the initial BCP ceramics (BCP‐C) and those with solid whiskers, BCP‐HW exhibits larger specific surface area (3.9 times vs BCP‐C) and higher mechanical strength (3.4 times vs BCP‐C), endowing it with stronger stimulation on adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells. In an intramuscular implantation model of canine, BCP‐HW shows excellent osteoinductivity and promotes the maturation of new bone, and the resultant compressive strength of the implant increases to ≈12 MPa at 3 months postoperatively. In another critical‐sized segmental bone defect model of rabbit femur, BCP‐HW has the best repairing effect. After implantation for 6 months, much more new bone ingrowth and higher bending load are observed in BCP‐HW than BCP‐C. Collectively, these findings suggest that the in situ hollow‐tube whisker construction possesses immense potential in expanding the applications of Ca‐P ceramics to load‐bearing bone defect repair.
 
Schematic of the graft on‐a‐chip platform, fabrication, and generation of test (coated) surfaces. a) Graft on‐a‐chip platform with blood perfusion. b) Expanded diagram of the platform showing (top to bottom): inlets, PEG‐coated PMMA, pre‐cut PSA channels, coatings applied to substrate (test surfaces), and vascular prosthesis (substrate). c) Illustration of the fabrication protocol. d) Shear tolerance of the graft‐chip device bonded to 6 clinically relevant materials: poly (methyl methacrylate) (PMMA), polyethylene (PE), ePTFE, polyvinyl chloride (PVC), nylon, silicone used in catheters, stents, grafts, hemofilter, and heart valves.[37,38] e) Common grafting sites with wall shear stress and in vivo grafting conditions on the graft‐chip device. f) Illustration of graft thrombosis, antithrombogenic graft surfaces, and application of test surfaces in the graft on‐a‐chip device. Uncoated surface with adherence of red blood cells and fibrin, CD34 antibody LIS with endothelial cells and fibrin, LIS with reduced surface adhesion of blood and endothelial cells.
Application of graft on‐a‐chip platform for testing the thrombogenicity of ePTFE and LIS ePTFE graft surfaces. a) Illustration of the device cross section with testing surfaces and channel geometry and physiological WSS inspiration (lower extremity arterial bypass). b) Perfusion set‐up with a syringe pump, reservoir, and fluorescent microscope. c) Qualitative assessment of thrombogenicity at 3 time points: 0 (left), 8 (middle), 20 min (right). Fluorescent labels: fibrin(ogen) (AlexaFluor488 in green λ488nm), thrombin activity with Boc‐Val‐Pro‐Arg‐AMC (blue λ350nm). d) Appearance of occluded channel(s) both with and without fluorescence. e‐i) Quantification of adherent fibrin(ogen) post‐occlusion and e‐ii) Boc‐Arg (AMC) fluorescent intensity during perfusion. Area under the curve (AUC) was tabulated in (e‐ii). f) SEM images of post‐perfusion surfaces with the presence of activated platelets (PLT), red blood cells (RBC), and leukocyte/white blood cells (WBC) present on the control surface. Means of 4 samples ±SD with * p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 computed with unpaired, 2‐tailed t‐test, CI 95%.
a) Representative images of immunofluorescence staining of RFP ECs for VE‐cadherin (CD‐144, red λ647nm), f‐actin (green, λ488nm) on ePTFE, LIS coated, and CD34 LIS coated test surfaces. EC nuclei are stained with Hoescht 33342 (blue, λ350nm). Magnified insets showing VE‐cadherin (EC junctions) on test surfaces (scale bar 20 µm). (b) Brightfield images of each test surface at 20×. c) Graft‐chip test channels and surfaces during blood perfusion with human hand to scale. d) Observed cell density on the 3 test surfaces. Means of 4 samples ± SD with * p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 computed with unpaired, 2‐tailed t‐test, CI 95%.
Application of graft on‐a‐chip platform for testing the thrombogenicity of endothelialized ePTFE, LIS ePTFE, and CD34 LIS ePTFE graft surfaces. a) Illustration of the device cross section with testing surfaces and channel geometry and physiological WSS inspiration (arterial anastomosis). b) Qualitative assessment of thrombogenicity at 3 time points: 0 (left), 8 (middle), 20 minutes (right). Fluorescent labels include fibrin(ogen) (AlexaFluor488 in green λ488nm), thrombin activity with Boc‐Val‐Pro‐Arg‐AMC (blue λ350nm), endothelial cells (RFP HUVEC in orange λ544nm). (c) Representative image of channels at occlusion. d‐i) quantification of adherent fibrin(ogen) post‐occlusion and d‐ii) Boc‐Arg (AMC) fluorescent intensity during perfusion. Area under the curve (AUC) was tabulated in (d‐ii). e) SEM images of surfaces post perfusion with the presence of red blood cells, fibrin, activated and resting platelets (top‐bottom). Means of 4 samples ± SD with *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001 computed with unpaired, 2‐tailed t‐test, CI 95%.
Article
Vascular grafts are essential for the management of cardiovascular disease. However, the lifesaving potential of these devices is undermined by thrombosis arising from material and flow interactions on the blood contacting surface. To combat this issue, antithrombogenic coatings have emerged as a promising strategy for modulating blood and graft interaction in vivo. Although an important determinant of graft performance, hemodynamics are frequently overlooked for in vitro testing of coatings and their translatability remains poorly understood. Herein, this limitation is addressed with a microscale graft on‐a‐chip platform incorporating vascular prosthesis and coatings with tuneable flow and surface conditions in vitro. As a proof of concept, the platform is used to test the thrombogenicity of a novel class of lubricant‐infused surface (LIS) and antibody lubricant‐infused (anti‐CD34 LIS) coated expanded polytetrafluoroethylene (ePTFE) vascular grafts in the presence of arterial wall shear stress with and without endothelial cells. The findings suggest LIS ePTFE is thromboresistant under flow with significantly reduced fibrin(ogen) deposition, thrombin activity, and blood cell adhesion compared to uncoated controls. It is moreover apparent that the microscale properties of the device are advantageous for the testing and translation of novel antithrombogenic coatings and blood‐contacting materials in general.
 
a) Optimized geometric structures of the (phen2N2)FeCl molecule (left) and the (phen2N2)FeCl monolayer in a (√2 × √2) supercell (right). The dashed rectangle marks a unit cell of the monolayer, and the terms a and b denote lattice vectors. The gray, blue, purple, white, and green balls indicate C, N, Fe, H, and Cl atoms, respectively. b) Calculated ORR free energy diagram at zero potential. c) Geometric structures of the transition state (TS) of the involved electrochemical steps.
Electronic density of states of the (phen2N2)FeCl monolayer: a) neutral state (zero system charge), b) U = 0 V, c) U = –1.23 V, and d) U = 1.23 V versus SHE.
a,b) Free energy changes for ORR of the (phen2N2)FeCl monolayer at (a) pH = 1 and (b) pH = 13 as a function of potential. c,d) Free energy changes for OER of the (phen2N2)FeCl monolayer at (c) pH = 1 and (d) pH = 13 as a function of potential. e) Calculated ORR/OER overpotentials at pH = 1 and pH = 13. f) The binding energy of Cl* as a function of potential at pH = 1. The blue and orange lines represent Cl* bind on the (phen2N2)Fe monolayer and the (phen2N2)FeCl monolayer, respectively.
a) Kinetic barriers (ΔG‡) of the ORR steps of the (phen2N2)FeCl monolayer as a function of potential at pH = 1. b) Simulated ORR/OER polarization curves based on the constant‐potential results. c) 2D map of the adsorption energy of OH* as a function of potential and pH. d) Calculated charge transfer values of ORR intermediates as a function of pH. Insert is charge density difference of OH*.
Free energy changes of the ORR (upper) and OER (bottom) steps of a,d) (phen2N2)MnCl monolayer, b,e) (phen2N2)CoCl monolayer, and c,f) (phen2N2)NiCl monolayer (pH = 1) as a function of electrode potential.
Article
Achieving efficient bifunctional oxygen reduction and evolution reactions (ORR/OER) on non‐noble metal catalysts is desirable but remains a significant challenge. Herein, inspired by the experimentally synthesized (phen2N2)FeCl molecule, a stable 2D organometallic framework, namely (phen2N2)FeCl monolayer, is proposed as a qualified candidate by means of constant‐potential first‐principles computations. Unlike most 2D organometallic frameworks that feature pyrrolic coordination, the (phen2N2)FeCl monolayer exhibits a pyridinic‐type FeN4 ligation environment. The unique structure of the monolayer enables a high single‐atom Fe loading in a heterogeneous system, superior to the typical FeNC materials. Constant‐potential energy analysis and microkinetic modeling demonstrate that the monolayer holds great potential for facilitating bifunctional ORR/OER in both the acidic and alkaline conditions, showing theoretical activity higher than the FeNC materials, (phen2N2)FeCl molecule, and Pt/IrO2. Moreover, (phen2N2)MCl monolayers (M = Mn, Co, and Ni) are explored, and the (phen2N2)MnCl monolayer is also identified to have excellent bifunctional activity. This work highlights the rational design of local coordination environments for boosting the electrocatalytic performance of 2D organometallic frameworks. This work presents a novel 2D organometallic framework featuring pyridinic‐type FeN4 ligation environment, namely (phen2N2)FeCl monolayer, which is different from most 2D organometallic frameworks. Constant‐potential first‐principles computations and microkinetic modeling show that the monolayer holds great potential for facilitating oxygen reduction and evolution reactions in both acidic and alkaline conditions.
 
Article
Atomic layer deposition (ALD) is a suitable technology for conformally depositing thin films on nanometer‐scale 3D structures. RuO2 is a promising diffusion barrier for Ru interconnects owing to its compatibility with Ru ALD and its remarkable diffusion barrier properties. Herein, a RuO2 diffusion barrier using an ALD process is developed. The highly reactive Ru precursor [tricarbonyl(trimethylenemethane)ruthenium] and improved O2 supply enable RuO2 deposition. The optimal process conditions [pulsing time ratio (tO2/tRu): 10, process pressure: 1 Torr, temperature: 180 °C] are established for the RuO2 growth. Growth parameters, such as the growth rate (0.56 Å cycle–1), nucleation delay (incubation period: 6 cycles), and conformality (step coverage: 100%), are also confirmed on the SiO2 substrate. The structural and electrical properties of the Ru/RuO2/Si multilayer are investigated to explore the diffusion barrier performance of the ALD‐RuO2 film. The formation of Ru silicide does not occur without the conductivity degradation of the Ru/RuO2/Si multilayer with an increase in the annealing temperature up to 850 °C, thus demonstrating that interdiffusion of Ru and Si is completely suppressed by a thin (5 nm) ALD‐RuO2 film. Consequently, the practical growth behavior and diffusion barrier performance of RuO2 can serve as a potential diffusion barrier for Ru interconnects. The Ru interconnect is a next‐generation technology that can cope with the extreme reduction of the technology node for semiconductor chip fabrication. RuO2 as a diffusion barrier is successfully grown using atomic layer deposition (ALD). A continuous ALD of RuO2 and Ru ALD process realizes the Ru/RuO2/Si structure to suppress the interdiffusion of Ru and Si at the interface.
 
Article
The development of high‐quality and strongly Au conjugated upconversion nanoparticles (UCNPs) is time‐consuming and requires specific chemicals. Therefore, a one‐pot hydrothermal method is adopted for novel in situ preparation of UCNP@Au composites using a binary functional ethylenediaminetetraacetic salt, which is employed as a surfactant and reducing agent. The composites are electrostatically conjugated with metal‐coordinated Prussian blue (PB) to yield UCNP@Au+PB nanocomposites (NCs), which demonstrate 21‐fold upconversion emission quenching by fluorescence resonance energy transfer compared to UCNPs. Additionally, the PB, UCNP@Au, and NCs demonstrate a synergistically reduced trap (α ≈ 0.85) and enhance ultrasensitive broadband (432–980 nm) photodetection. The NCs‐based gate‐free epitaxial graphene device demonstrates excellent high photoresponsivity (5.9 × 10⁵ A W–1), detectivity (2.17 × 10¹⁴ cmHZ W−1${\rm{cm}}\sqrt {{{\rm{H}}_{{\rm{Z}}}}} {{\rm{W}}^{{\bm{ - }}1}}$), and normalized gain (2.06 × 10⁻⁴ m² V–1) at 318 nW cm–2 (532 nm) and a bias voltage of 1 V. The Au plasmons enhance the one‐photon‐enabled visible absorption of Er³⁺ ions, and PB exhibits broad absorption and enhances the carrier density of the device, resulting in an ultrahigh photoresponse. The obtained device performance is the highest to date among their class of nanohybrids. Also, these NCs can readily detect polychromatic light and signals from daily‐use appliances, indicating their potential for applications in consumer electronics.
 
a,b) The chemical structure of the prospective TADF emitters. c–f) CV traces were recorded on the TADF compounds as a neat thin film c,d) and as dissolved in CH2Cl2 (oxidation) or DMF (reduction) solution in a concentration of ≈1 g L–1 e,f). The vertical dashed lines indicate the derived onset potentials for the redox reactions.
a) The normalized absorption and PL spectra of neat TADF films. b) The normalized steady‐state EL spectra of the guest‐only LECs, with a schematic of the device structure displayed in the inset. c,d) The temporal evolution of the luminance and the voltage of the guest‐only TADF‐LECs during constant‐current driving with 7.7 mA cm–2, and with the TADF emitter being (c) CZ‐TRZ and (d) 4CZ‐BN. The mass concentration of the THABF4 electrolyte is 6.3%.
a,b) The chemical structure of the two host compounds. c–f) CV traces were recorded on the host compounds as a neat thin film (c,d) and as dissolved in CH2Cl2 solution e,f). g) A comparison of the CV traces of neat thin films of the two host compounds and the blend‐host. The vertical dashed lines in (c–f) mark the derived onset potentials for the redox reactions. h) The PL spectra of thin films of the two host compounds and the blend‐host, with the energy‐level diagram of the blend host presented in the inset.
a) The energy‐level diagram of the blend‐host:guest LECs. b) The current efficacy as a function of guest concentration for the blend‐host:guest LECs during constant current‐density driving by j = 7.7 mA cm–2. c,d) The temporal evolution of the luminance and the voltage for blend‐host‐guest TADF‐LEC, with the guest selection identified in the insets. e) The external quantum efficiency of the blend‐host:guest TADF‐LECs as a function of peak luminance. f) The EL spectrum of the two blend‐host:guest LECs. g,h) The PL transients of the blend‐host:guest active material with the guest being: CZ‐TRZ (g) 4CZ‐BN (h).
Article
Light‐emitting electrochemical cells (LECs) comprising metal‐free molecules that emit by the process of thermally activated delayed fluorescence (TADF) can be both sustainable and low cost. However, the blue emission performance of current TADF‐LECs is unfortunately poor, which effectively prohibits their utilization in important applications, such as illumination and full‐color displays. Here, this drawback is addressed through the development of a TADF‐LEC, which delivers blue light emission (peak wavelength = 475 nm) with a high external quantum efficiency of 5.0%, corresponding to a current efficacy of 9.6 cd A‐1. It is notable that this high efficiency is attained at bright luminance of 740 cd m‐2, and that the device turn‐on is very fast. It is demonstrated that this accomplishment is enabled by the blending of a carbazole‐based 9‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)‐2‐methylphenyl)‐3,6‐dimethyl‐9H‐carbazole guest emitter with a compatible carbazole‐based tris(4‐carbazoyl‐9‐ylphenyl)amine:2,6‐bis(3‐(carbazol‐9‐yl)phenyl)pyridine blend‐host for the attainment of bipolar electrochemical doping, balanced electron/hole transport, and exciplex‐effectuated host‐to‐guest energy transfer.
 
Article
The development of inorganic hole‐transporting materials (HTMs) is one of the most reliable ways to improve the stability of perovskite solar cells (PSCs). However, the un‐optimal buried interfacial contacts and the defects located at the inorganic HTMs/perovskite interface restricted the device's performance. Herein, a phase‐pure CuScO2 has been synthesized and further employed as mesoporous HTM in inverted PSCs. Surprisingly, a facile pretreatment of the hole‐transport layer by a formamidine salt compensates the I⁻ vacancy of the buried perovskite film, thus regulating the interfacial band energy alignment between the HTM and perovskite. This ion compensation strategy can not only in situ repair the ion loss and improve the built‐in electric field, but also decrease the charge injection barrier and suppress the non‐radiative interfacial recombination. Benefiting from these merits, the resulting methylammonium‐free (MA), Cs/FA‐based PSCs displays a power conversion efficiency (PCE) of 22.42% along with excellent thermal and light stability. Moreover, the pre‐buried treatment strategy can be extended to MA‐containing CsFAMA triple‐cation perovskite film, and a champion inverted device delivers a PCE of 23.11%. This study offers a new avenue to the rational design of HTMs for highly efficient and stable PSCs.
 
Structural characterization of self‐assembled betulin particles. SEM images of: A) betulin needle crystals; B) ordered‐stacked layers of betulin needle crystals; C) betulin needle crystal growth along the axis; and D) betulin supraparticles observed under different magnifications. E,F) SEM images of hedgehog suprastructures formed by betulin under the effect of sonication and TEM images of the betulin supraparticles highlighting the: G) external and H) internal features.
A) Betulin chemical structure. B) ¹H NMR spectrum (CDCl3) of betulin crystal. C) TGA and DTG profiles of betulin crystals. D) Powder X‐ray diffraction profile of betulin crystals and supraparticles.
A) Space fill structure of betulin molecules. B) Hydrogen bond pattern between the betulin crystal asymmetric unit, hydrogen‐bonded betulin molecule, and 2‐propanol molecule. C) 2‐Dimensional network structure in betulin‐2‐propanol solvate. D) Schematic illustration of the molecular packing of betulin single‐crystal cell.
SEM images of betulin particles morphology following increased sonication time: A) 30 s, B) 5 min, C) 10 min, D) 20 min, and E) 30 min. F) Schematic illustration of the mechanism of supraparticle transformation with sonication time.
A) Morphology of the superhydrophobic betulin supraparticles/PDMS coating (SEM), with details. B) Topography of betulin supraparticles/PDMS coating, embedding with static water contact angle at the relative surface. C) Dynamic water contact angle (advancing and receding angle) detected on betulin supraparticles/PDMS coating. D) Simplified wetting model of micro–nano hierarchical rough structures. E) Changes of water contact angle with different cycles of peeling off test. F) Pendant drop of a betulin solution in dichloromethane immersed in water. The crystallization of betulin was observed after 10 min.
Article
Betulin is introduced as a building block of supramolecular structures that form by noncovalent interactions. Betulin, an abundant triterpene, is first extracted from birch bark to self‐assemble into hierarchical crystalline structures. Following a direct bottom‐up process, solvatomorphs of betulin‐2‐propanol form high axial aspect microparticles, 100–300 µm in length, and lateral sizes in the 15–40 µm range. Under sonication, the microparticles evolve into 3D hedgehog suprastructures (15–30 µm in size) comprising a core (3–5 µm diameter) with connected spines (200–300 nm in width). Depending on the intensity of the delivered energy, the associated morphogenesis starts with metastable aggregates that undergo dislocation, solvent migration, and radial growth. The authors find that the formed spherulite‐like, hedgehog structures are a consequence of residual solvent diffusion, leading to crystallites with oriented attachment on specific planes. These results add to the design of structures from natural building blocks, which are expected to deliver functions encoded in the respective morphology. Owing to the unique features of betulin supraparticles, they develop surface architectures, for instance, in superhydrophobic coatings, which are shown to exhibit exceptional repellency and surface mechanical strength, as tested on various substrates.
 
Article
The uncontrollable lithium (Li) dendrite growth and unstable solid electrolyte interfaces (SEI) hinder the practical application of Li metal batteries (LMBs). Herein, a PAN/CNTs‐based SiO2‐modified vertical‐cavity film (PCS‐VCF) with a network structure is prepared by a simple spin‐coating process to address these challenges. This new current collector with a polar lithiophilic network stabilizes the Li metal anodes by regulating the chemical environment in carbonate electrolytes. The dipole interaction between the CN groups and the CO groups reduces the high reactivity of the carbonates in the electrolyte, forming an SEI layer with higher inorganic components and enhancing the stability of the electrode/electrolyte interface. The special vertical‐cavity network structure inside the current collector can decrease local current density and suppress the huge volume expansion of Li metal during the cycling process. Consequently, a high‐performance Li metal anode with dendrite‐free morphology is achieved (over 1500 cycles with low overpotential at 20 mA cm⁻² in symmetric cells). Furthermore, full cell with the LiNi0.8Co0.1Mn0.1O2 cathode delivers a stable capacity of 164.5 mA h g⁻¹ for 500 cycles at 5 C, with a capacity decay rate of 0.077% per cycle.
 
The effect of ligand additive on ZnO nanocrystals. a) Schematic synthesis diagram of the D‐ZnO colloidal nanocrystals solution. XPS spectra of b) N 1s, c) Br 3d, d) Zn 2p, and e) O 1s core levels of the ZnO and D‐ZnO films. f) PL spectra of ZnO and D‐ZnO films. g) Schematic diagram of nonradiative recombination at the interface between the ETL and pure‐blue perovskite QDs.
Effect of colloidal ZnO solution on the perovskite QDs films. a) PL spectra b) TRPL spectra of the QDs film, QDs‐Et film, and QDs‐Et+L film, respectively. XPS spectra of c) Pb 4f, d) Br 3d, and e) N 1s core levels of the QDs film, QDs‐Et film, and QDs‐Et+L film. f) Statistical Br/Pb and N/Pb atomic ratios of the QDs film, QDs‐Et film, and QDs‐Et+L film.
Luminance and stability of PeLEDs. a) The structure image of the PeLEDs. b) EL spectra of PeLEDs (Illustration: The digital photo of the PeLEDs operated under current density of 60.5 mA cm–2). c) CIE color coordinates, d) J–V–L curve, and e) L–J curve of PeLEDs. f) The half‐lifetime of PeLEDs at an initial luminance of 100 cd m–2. g) The EL spectra of the PeLEDs when performing stability test. h) The hysteresis of PeLEDs. i) Current of the PeLEDs as a function of time under constant voltage of 5 V.
Performance of the ETL for PeLEDs. a) I–V curve of the device with the structure of ITO/ZnO or D‐ZnO/Ag. b) UPS spectra of the ZnO and D‐ZnO films. c) The energy level image of PeLEDs. d) I–V curve of the EOD with the structure of ITO/ZnO/perovskite QDs/ZnO or D‐ZnO/Ag and I–V curve of the HOD with the structure of ITO/PEDOT:PSS/PVK/perovskite QDs/MoO3/Ag. e) The EQE of the champion PeLEDs based on ZnO and D‐ZnO ETL. f) Histograms of the EQE of the PeLEDs based on ZnO and D‐ZnO ETL (The sample size n = 15, P‐values are calculated using one‐way ANOVA with Bonferroni correction, *P < 0.05.)
Article
Solution‐processed light‐emitting diodes (LEDs) show great potential for low‐cost fabrication of large‐area display panels, but the efficient perovskite LEDs (PeLEDs) cannot be achieved by all solution process, because the perovskite emitter is easily destroyed by subsequent solution. In particular, the solution‐processed PeLEDs with blue emission wavelength in 460–470 nm (pure‐blue, meeting Rec. 2020 standards) still is inferior. Here, highly efficient and stable pure‐blue PeLEDs are achieved by all solution process based on colloidal perovskite quantum dots and difunctional ZnO (D‐ZnO) nanocrystals. The D‐ZnO nanocrystals are obtained by a ligand strategy of phenethylammonium bromide, which not only repairs the perovskite surface destroyed by the solvent of the D‐ZnO solution, but also enables the balanced charge injection to suppress Auger recombination. The PeLED presented pure‐blue emitting at 470 nm wavelength, a maximum luminance of 11 100 cd m‐2, and external quantum efficiency of 8.7% (record efficiency for pure‐blue emission). The device also showed a continuous operation half‐lifetime of 35 h at luminance of 100 cd m‐2.
 
Article
Yellow‐phase formamidinium lead iodide (δ‐FAPbI3) as a degradation product of black perovskite phase is usually unwelcome in perovskite solar cells (PSCs). However, it also shows high potential in passivating defects and protecting perovskite films from moisture intrusion due to its water‐stable nature. Herein, the utilization of δ‐FAPbI3 to construct a yellow/black heterophase bilayer is reported, in which the perovskite layer is shielded by in situ formed δ‐FAPbI3 species on the surface, for PSCs with enhanced efficiency and stability. It is found that the δ‐FAPbI3 layer with a broader bandgap than the black‐phase perovskite can efficiently suppress the charge recombination at the interface, offering a high PSC efficiency of 23.10%. More importantly, the δ‐FAPbI3‐modified devices exhibit preferable stability against various external stresses to that of the control ones. Compared to those using the disliked δ‐FAPbI3 in the literature, the strategy, which maximizes its merits in reducing the interfacial charge recombination and stabilizing the perovskite structure, is more simple yet effective to realize highly efficient and stable PSCs.
 
Article
Electrocatalysts play a vital role in electroreduction of N2 to NH3 (NRR); however, large‐scale industrial application of electrochemical NRR is still limited by low selectivity and poor activity, owing to the sluggish reaction kinetics. Herein, a high‐performance NRR catalyst consisting of atomically dispersed iron single site embedded in porous nitrogen‐doped carbon nanofibers with abundant carbon defects (D‐FeN/C) is reported. The D‐FeN/C catalyst achieves a remarkably high NH3 yield rate of ≈24.8 µg h⁻¹ mgcat⁻¹ and Faradaic efficiency of 15.8% at −0.4 V in alkaline electrolyte, which outperforms almost all reported Fe‐based NRR catalysts. Structural characterization manifests that the isolated Fe center is coordinated with four N atoms and assisted by extra carbon defects. In situ attenuated total reflectance‐Fourier transform infrared results and kinetics isotope effects demonstrate that the intrinsic carbon defects dramatically enhance the water dissociation process and accelerate the protonation kinetics of D‐FeN/C for NRR. Theoretical investigations unveil atomic Fe‐N4 catalytic sites together with intrinsic carbon defects synergistically reduce the energy barrier of the protonation process and promote the proton‐coupled reaction kinetics, thus boosting the whole NRR catalytic performance.
 
Article
Exosomes, a form of small extracellular vesicles, play a crucial role in the metastasis of cancers and thus are investigated as potential biomarkers for cancer diagnosis. However, conventional detection methods like immune‐based assay and microRNA analyses are expensive and require tedious pretreatments and lengthy analysis time. Since exosomes related to cancers are reported to exist in tears, a poly(2‐hydroxyethyl methacrylate) contact lens embedded with antibody‐conjugated signaling microchambers (ACSM‐PCL) capable of detecting tear exosomes is reported. The ACSM‐PCL exhibits high optical transparency and mechanical properties, along with extraordinary biocompatibility and good sensitivity to exosomes. A gold nanoparticle colorimetric assay is employed to visualize captured exosomes. The ACSM‐PCL can detect exosomes in the pH range of 6.5–7.4 (similar to the human tear pH) and have a strong recovery yield in bovine serum albumin solutions. In particular, the ACSM‐PCL can detect exosomes in various solutions, including regular buffer, cell culture media from various cell lines, and human tears. Finally, the ACSM‐PCL can differentiate expression of exosome surface proteins hypothesized as cancer biomarkers. With these encouraging results, this ACSM‐PCL is promised to be the next generation smart contact lens as an easy‐to‐use, rapid, noninvasive monitoring platform of cancer pre‐screening and supportive diagnosis.
 
Article
Physically intelligent micro‐robotic systems exploit information embedded in micro‐robots, their colloidal cargo, and their milieu to interact, assemble, and form functional structures. Nonlinear anisotropic fluids such as nematic liquid crystals (NLCs) provide untapped opportunities to embed interactions via their topological defects, complex elastic responses, and ability to dramatically restructure in dynamic settings. Here a four‐armed ferromagnetic micro‐robot is designed and fabricated to embed and dynamically reconfigure information in the nematic director field, generating a suite of physical interactions for cargo manipulation. The micro‐robot shape and surface chemistry are designed to generate a nemato‐elastic energy landscape in the domain that defines multiple modes of emergent, bottom‐up interactions with passive colloids. Micro‐robot rotation expands the ability to sculpt interactions; the energy landscape around a rotating micro‐robot is dynamically reconfigured by complex far‐from‐equilibrium dynamics of the micro‐robot's companion topological defect. These defect dynamics allow transient information to be programmed into the domain and exploited. Robust micro‐robotic manipulation strategies are demonstrated that exploit these diverse modes of nemato‐elastic interaction to achieve cargo docking, transport, release, and assembly of complex reconfigurable structures at multi‐stable sites. Such structures are of great interest to future developments of LC‐based advanced optical device and micro‐manufacturing in anisotropic environments.
 
Article
Fibronectin (FN) is a well‐established hallmark of epithelial‐to‐mesenchymal transition, and may serve as an omnipresent cancer biomarker regardless of the origins of tumor cells. An ssDNA aptamer (ZY‐1) with highly selective binding affinity to mesenchymal stromal cells is previously developed, but the binding target of ZY‐1 on the cells and the underlying mechanism is yet to be understood. Here, the identification of FN as the target protein of aptamer ZY‐1 is reported for the first time and the mechanism of ZY‐1 binding to cFN is explored. The data indicate that ZY‐1 solely recognizes cellular fibronectin (cFN) rather than plasma fibronectin (pFN). The ZY‐1 binding to cFN is explored through computational modeling and the competition of heparin in binding cFN owing to steric hindrance is confirmed. The in vitro assay and noninvasive in vivo fluorescence imaging results validate the specificity of ZY‐1 in targeting cFN and sensitivity in detecting tumors. The ZY‐1‐mediated targeted cancer therapy using a proof‐of‐concept study with a ZY‐1‐based complex loaded with doxorubicin (Dox) is further proved. This study would facilitate more comprehensive studies of anti‐FN aptamers in the imaging and treatment of tumors and other FN‐associated diseases.
 
Article
The functions of covalent organic frameworks (COFs) can be tailored by covalently reticulating advanced molecular modules into well‐defined porous ordered materials. Herein, four COFs, USTB‐7–USTB‐10, are prepared from the solvothermal reaction of photoactive tetraaldehydes, 5,5″‐(benzo[c]‐[1,2,5]thiadiazole‐4,7‐diyl)diisophthalaldehyde and 5,5″‐(naphtho[2,3‐c][1,2,5]thiadiazole‐4,9‐diyl)diisophthalaldehyde, with p‐phenylenediamine and benzidine, respectively. Comprehensive studies of powder X‐ray diffraction, theoretical simulation, and pore size distribution disclose their isoreticular 2D dual porous structures. In contrast to benzo[c][1,2,5]thiadiazole‐based chromophore, employment of naphtho[2,3‐c][1,2,5]thiadiazole‐based tetraaldehyde enables enlarged conjugation systems for USTB‐9 and USTB‐10, rather than USTB‐7 and USTB‐8. This, in combination with the longer benzidine unit, endows USTB‐10 with a porous structure with bigger pore size than that of USTB‐9, resulting in the highest photocatalytic hydrogen production rate of 21.8 mmol g⁻¹ h⁻¹ with the help of a Pt cocatalyst. Experimental and theoretical studies reveal the outstanding photocatalytic activity for USTB‐10 among the four COFs associated with the narrowed bandgap and increased charge‐carrier separation efficiency.
 
Growth and device architecture of transparent MoS2 TFTs on glass. a) Schematic of the experimental setup of PECVD. b) Mechanism of layered MoS2 formation by PECVD and inset shows schematic illustration of the top and cross‐section view of layered MoS2 c) Comparison of with and without MoS2 on large‐area glass. d) Top‐gated TFT array on glass and schematic of the layer‐by‐layer architecture of the transparent TFT. e) Transparent TFT array through which the background image is captured.
Spectroscopic and microscopic characterization of MoS2. a) Raman spectra of MoS2 film grown at different temperatures under the assistance of plasma, inset show FWHM of E¹2g and peak positions of E¹2g and A1g versus growth temperature. b) PL spectra of MoS2. c) Comparison of the XPS spectra of MoS2 grown with and without plasma at 400 °C. d) HRTEM micrograph of MoS2 grown at 400 °C; inset shows the layered structure of MoS2. e,f) Raman mapping images of the intensities of the E¹2g and A1g vibration modes over an area of 20 × 20 µm².
Electrical characterization of MoS2. a) Schematic architecture of top‐gated MoS2 TFT (inset shows the optical microscopy image of a single TFT on glass). b) Ids–Vgs (transfer curve) curve of MoS2 TFT (in the log scale); inset shows the Ids–Vds curve (diode curve) on a linear scale. c) Ids–Vds curves (output curves) of MoS2 TFT in the Vgs range from −20 to 10 V at a step of 2.5 V. d) Transfer curve of 49 TFTs in the log scale; inset shows the optical microscopy image of the TFT array (49 devices). Statistics of e) Ion:Ioff and f) Vth from 49 TFTs. Average Ion/off and Vth are 4 × 10⁴ and −8.2 V, respectively.
Photoresponsive performance of MoS2 phototransistor. a) Schematic illustration of MoS2 phototransistor. b,c) Ids–Vgs curves of MoS2 phototransistor at Vds = 1 V under blue light (λ = 405 nm) and red light (λ = 638 nm) illumination with different incident power densities (0.42–83.3 mW cm⁻²). d–f) Comparison of responsivity, specific detectivity, and sensitivity under blue and red light illumination. Highest responsivities (R) of 27 and 10 A W⁻¹, specific detectivities of 3.5 × 10⁸ and 1.44 × 10⁸ at Pinc = 0.42 mW cm⁻², and sensitivities of 365 and 309 at 83.3 mW cm⁻² for blue and red light are observed, respectively. g,h) NBIS (Vgs = −25 V) and PBIS (Vgs = 15 V) were applied for 1, 10, 30, 60, and 90 min (with λ = 405 nm, Pinc = 41.7 mw cm⁻²) and the transfer curve was recorded with Vds = 1 V. i) Comparison of photo switching characteristics of the phototransistor under the pulse of blue and red light (f = 0.5 Hz, Pinc = 4.17 mA cm⁻²).
MoS2 phototransistor array for imaging. a,b) The array was illuminated with blue light and red light through an opaque shadow mask with S‐ and K‐shaped transparent patterns and the photocurrent was sequentially measured and mapped, respectively.
Article
MoS2‐based transparent electronics can revolutionize the state‐of‐the‐art display technology. The low‐temperature synthesis of MoS2 below the softening temperature of inexpensive glasses is an essential requirement, although it has remained a long persisting challenge. In this study, plasma‐enhanced chemical vapor deposition is utilized to grow large‐area MoS2 on a regular microscopic glass (area ≈27 cm²). To benefit from uniform MoS2, 7 × 7 arrays of top‐gated transparent (≈93% transparent at 550 nm) thin film transistors (TFTs) with Al2O3 dielectric that can operate between −15 and 15 V are fabricated. Additionally, the performance of TFTs is assessed under irradiation of visible light and estimated static performance parameters, such as photoresponsivity is found to be 27 A W⁻¹ (at λ = 405 nm and an incident power density of 0.42 mW cm⁻²). The stable and uniform photoresponse of transparent MoS2 TFTs can facilitate the fabrication of transparent image sensors in the field of optoelectronics.
 
Article
Messenger RNA (mRNA) is an emerging class of biotherapeutics for vaccine development and genome editing. Efficacious delivery and control of mRNA functionality selectively to disease cells remains the major challenge in developing mRNA therapeutics. Herein, reactive oxygen species (ROS)‐degradable lipid nanoparticles containing a thioketal (TK) moiety to deliver mRNA into cells are reported, selectively releasing mRNA in tumor cells for enhanced gene expression. By screening a library of parallelly synthesized ROS‐degradable lipids, it has been identified that BAmP‐TK‐12 delivers mRNA one‐fold more potent in tumor cells than in non‐cancerous cells. Furthermore, the delivery of mRNA encoding DUF5, a bacterial‐derived RAS protease using BAmP‐TK‐12 enables generic depletion of mutant RAS of tumor cells, showing a significantly improved antitumor effect than small molecule‐based RAS inhibitor. It has been believed that the strategy of tumor cell‐selective mRNA delivery using ROS‐degradable lipid nanoparticles can be expanded to the broad range of bacterial effectors for rewiring cancer cell signaling and developing advanced biotherapeutics.
 
Article
The large‐scale industrial applications of graphene highly depend on its mass production with efficiency (high‐yield, time‐saving, and low‐cost) and controllability (high‐quality, safe, and environmentally friendly). However, this requirement can hardly be satisfied by incumbent chemical exfoliation methods exploiting liquid–solid interactions. Recently, many studies have demonstrated that the usage of bubbling as a new tool makes a big difference in multiple aspects of graphene production. Benefiting from their unique properties, the bubbles can be employed as the driving force to cleave graphite layers for graphene preparation or as the favorite interface for graphene growth at a high temperature. Therefore, the bubble‐mediated technique represents a new strategy promising to achieve efficient and controllable preparation of graphene. Here, the formation and evolution of bubbles in liquid media are first analyzed. Then, two routes including “top‐down” and “bottom‐up” toward mass production of graphene with the assistance of bubbles are summarized and discussed. This review sheds light on the introduction of gas to realize the mass production of graphene for the development of graphene's applications on large scale.
 
Synthesis and characterization of photocatalysts. a) The procedure schematic of the formation of NiCo−TiO2. b) The TEM images of NiCo−TiO2. c) Cs‐corrected HAADF‐STEM image of Ru−TiO2. d) Statistical analysis of the single and dual sites and the Ru−Ru atom distance in (c). e) STEM‐EDS elemental mapping of NiCo−TiO2. f) Raman spectra of TiO2, Ni−TiO2, Co−TiO2, and NiCo−TiO2.
Chemical environment of photocatalysts. a) Ni K‐edge XANES spectra of Ni‐TiO2, NiCo−TiO2, Ni foil, and NiO. b) Ni K‐edge FT‐EXAFS spectra of Ni−TiO2, NiCo−TiO2, Ni foil, and NiO. c) Ni K‐edge FT‐EXAFS spectra and corresponding fitting curves of Ni−TiO2. d) Ni K‐edge FT‐EXAFS spectra and corresponding fitting curves of NiCo−TiO2. e) Co K‐edge XANES spectra of Co−TiO2, NiCo−TiO2, Co foil, and CoO. f) Co K‐edge FT‐EXAFS spectra of Co−TiO2, NiCo−TiO2, Co foil, and CoO. g) Co K‐edge FT‐EXAFS spectra and corresponding fitting curves of Co−TiO2. h) Co K‐edge FT‐EXAFS spectra and corresponding fitting curves of NiCo−TiO2. i–l) Wavelet transform of the k³‐weighted EXAFS data of Ni foil, NiO, Ni−TiO2, and NiCo−TiO2. m–p) Wavelet transform of the k³‐weighted EXAFS data of Co foil, CoO, Co−TiO2, and NiCo−TiO2.
Photocatalytic CO2RR activity. a) Yield of CH3COOH and the other products produced under UV–vis light irradiation. b) NMR spectra for liquid product obtained from NiCo−TiO2 CO2RR reaction. c) Photocatalytic cycle stability and longtime stability for CO2RR reaction for NiCo−TiO2, R is CH3COOH rate. d) Electrons yield of NiCo−TiO2, CoTiO2, Co−TiO2, and TiO2 for CO2RR reaction.
Chemical adsorption and transformation of CO2. a) CO2‐TPD spectra of NiCo−TiO2, Ni−TiO2, Co−TiO2, and TiO2. TCD, thermal conductivity detector. b) CO‐TPD spectra of NiCo−TiO2, Ni−TiO2, Co−TiO2, and TiO2. c) In situ infrared spectra in reactant gas of CO2 under different light irradiation times.
DFT calculation. a) The lattice structure and 3D contour plot of electronic distributions in NiCo−TiO2. Darkcyan balls = Ni, Magenta balls = Co, Grey balls = Ti, and Red balls = O. Blue isosurface = bonding orbitals and green isosurface = anti‐bonding orbitals. PDOS of b) NiCo−TiO2 and c) TiO2. Site‐dependent PDOS of d) Ni‐3d, e) Co‐3d, and f) Ti‐3d in NiCo−TiO2. g) The simulated absorption spectra comparison in the light wavelength from 400–1000 nm. h) The comparison of CO2 adsorption on NiCo−TiO2. i) The activation barrier for the C−C coupling in NiCo−TiO2, Ni−TiO2, and Co−TiO2. j) The CO2RR reaction pathway on NiCo−TiO2.
Article
Photocatalytic reduction of CO2 to value‐added liquid fuels is a promising approach to alleviate the global energy and environmental problems. However, highly selective production of C2+ products from CO2 reduction reaction (CO2RR) is very difficult because of the sluggish CC coupling reaction. An asymmetric coupled heteronuclear photocatalyst is designed to overcome this limitation. The new catalyst contains single atoms of nickel and cobalt loaded on titanium dioxide. It exhibits an impressive 71% selectivity for acetic acid. The experimental data and theoretical calculations reveal that the Ni and Co single atom sites not only significantly lower the energy barrier of electron transfer in photocatalysis but also efficiently promote the CC coupling toward CH3COOH. The high activity of such a heteronuclear catalyst system will shed light on the future development of effective materials for CO2RR.
 
Article
Although photodegradability is promising for on‐demand tuning of material properties, phototuned materials cannot be utilized under ambient light irradiation owing to their photoinstability. Herein, a novel photostable gel that photodegrades only in the presence of an acid is fabricated. The unique reactivity of a supramolecular platinum‐acetylide complex is uncovered to incorporate into poly(methyl methacrylate) gel as the cross‐linker to exhibit softening and swelling under simultaneous treatment with UV‐light and acid. Conversely, when the acid is removed, the gel reacquires its photostability. A cross‐linker amount of only 0.7 wt.% is sufficient to realize the material property. Notably, the unique cross‐linkers, which change phosphorescence to fluorescence via photocleaving of PtC bonds, enable a photoprocess of optical functions. The controllable optical properties can be applied to information hiding technology and in visualizing the locally modified elasticity of the material, because of the photostability in absence of the acid. A strategy to realize photostable material with transient photodegradability in the presence of an acidic additive is reported. A poly(methyl methacrylate) gel combined with a platinum‐acetylide cross‐linker exhibits softening under UV–irradiation in the presence of an acid. Conversely, when the acid is removed, the gel exhibits photostability, acting as an optically functional material even under UV irradiation.
 
Article
Adaptive Materials In article number 2204681, Mizuki Tenjimbayashi and Masanobu Naito develop a superhydrophobic nano-magnetite swarm that imitates a fire ant superorganism. The swarm at the liquid–air interface is transformed from a dispersed state into a 2D raft and a 3D bivouac by magnetic field gradient. The swarm can adaptively transport small objects irrespective of their state (gas/liquid/solid) by switching their state.
 
Optical loss analysis for p‐MPSCs. a) The device structure schematic diagram of p‐MPSCs. b–c) Optical constant of each functional material in p‐MPSCs. n represents the refractive index and k represents the extinction coefficient. d) Optical losses and calculated current density losses in p‐MPSCs.
Preparation of SiO2 mesoporous films with different particle sizes. The schematic diagrams of a) the printable method for SiO2 mesoporous films and b) the antireflection of mesoporous films. c) The photographs of corresponding SiO2 slurries with different particle sizes. d) The transmittance curves of FTO glass without and with SiO2 mesoporous films. The insert images are the photographs of related samples.
Characterization of SiO2 mesoporous films with modulated porosity and thickness. a) The top‐view SEM images of mesoporous SiO2 films with different mass ratios of SiO2 to ethyl cellulose. b) The refractive index curves of SiO2 films with different porosities. c) The cross‐sectional SEM images of mesoporous SiO2 films with different thicknesses. d) The transmittance of FTO glass coated with mesoporous SiO2 films with different porosities. The insert images are the corresponding photographs, left to right: FTO glass, FTO glass coated with different SiO2 films. e) The transmittance of FTO glass coated with mesoporous SiO2 films with different thicknesses. Insert images are the corresponding photographs, left to right: FTO glass and FTO glass coated with SiO2 films made by slurries with decreased concentrations. f) The transmittance comparison of bare FTO glass and FTO glass coated with the optimized mesoporous SiO2 film.
Influence of the anti‐reflection coating on the device performance. a–d) The statistical photovoltaic parameters of p‐MPSCs without and with mesoporous SiO2 coatings. The symbols meaning: n: sample size, μ: averaged value, σ: standard deviation and p: calculated probability by two‐side t‐test. e) The J–V curves and photovoltaic parameters of champion devices. f) Corresponding IPCE and integrated current densities.
Optical loss analysis of p‐MPSCs after depositing SiO2 antireflection coatings and influence of the antireflection coatings on the reflectance of control and processed p‐MPSCs at different incident angles. a) Reflection curves of bare FTO glass, control, and processed p‐MPSCs at normal incidence. b) Optical loss analysis of processed p‐MPSCs. c) Reflection curves of control and processed p‐MPSCs at larger incident angles (30°, 50°, and 70°). d) Average reflectance values of control and processed p‐MPSCs at various incident angles.
Article
The power conversion efficiency (PCE) of single‐junction perovskite solar cells (PSCs) is being rapidly promoted towards their theoretical limit, with a certified value of 25.7%. Reducing optical loss will further contribute to PCE improvement. Here, the optical loss including reflection loss, absorption loss, and transmission loss in printable mesoscopic perovskite solar cells (p‐MPSCs) is analyzed. A printable mesoporous SiO2 antireflection coating for improving the transmittance of the fluorine‐doped tin oxide (FTO) glass substrate by reducing optical reflection at the air/glass interface is reported. With modulated porosity and thickness, the mesoporous SiO2 film constructs a graded refractive index interface and increases the transmittance of FTO glass by ≈2%–4% in the spectral range of 350–800 nm at normal incident angle with the highest transmittance improved from 85% to 89%. The SiO2 coating also exhibits wide‐angle and broadband antireflection properties. The coatings successfully help p‐MPSCs obtain about an average 3% enhancement in the short‐circuit current density (JSC) and PCE. This work demonstrates the necessity of optical management for efficient solar cells and provides a cost‐effective and scalable antireflection coating for the future realistic application of PSCs.
 
Structural degrees of freedom in ReO3‐type coordination polymers. a) In inorganic ReO3‐type materials and inorganic perovskites Glazer‐type octahedral tilts can occur. The use of molecular X‐site anions in molecular perovskites makes unconventional octahedral tilts and shifts accessible, and A²⁺ cations such as [H2dabco]²⁺ in [H2dabco]Mn2(H2PO2)6 introduce the possibility of various A‐site vacancy order pattern. In this work, A²⁺‐site cations with separated charges are used to form AB2X6‐type materials, adding a new structural degree of freedom related to their spatial orientation within the ReO3‐type network. b) The M2+$M_2^ + $ Glazer‐type tilt. c) An unconventional tilt (M5+$M_5^ + $) and shift (X5+$X_5^ + $). d) The crystal structure of [H2dabco]Mn2(H2PO2)6 is shown with emphasis on the empty voids within the [Mn(H2PO2)3]⁻ network. Note, for describing the distortion modes of the ReO3‐type network the Bradley–Cracknel notation (k#±$k_\# ^ \pm $) is used and that phosphorus and hydrogen atoms are omitted in the structure of [H2dabco]Mn2(H2PO2)6 for clarity; color code: gray: C, light blue: N.
Crystal structures and A²⁺ cation order pattern in AB2X6 materials. Shown are a) a structural diagram of the molecules employed on the A‐site and b) the crystal structures of [TPC4TP]Mn2(C2N3)6 and d) [TPC5TP]Mn2(C2N3)6 with emphasis on how the divalent A‐site cations bridge two pseudocubic Mn(C2N3)3 networks. c,e) For both materials a 2D order pattern of A²⁺ cations is observed. Depending on the separator length n of the [R3N(CnH2n)NR3]²⁺ cation, we observe a herringbone pattern (n = 4, c) or a head‐to‐tail pattern (n = 5, e). The hydrogen atoms are not shown for clarity. Color code for crystal structures: green/dark blue: A‐cation nitrogen, gray: carbon, light‐blue: X‐anion nitrogen, pink: manganese. For visualization purposes, the size of the A‐site atoms was increased.
Temperature and pressure dependent structural behavior of AB2X6 coordination polymers. Shown are the evolution of principal axes as a function of temperature and pressure. For A = TPC4TP²⁺, uniaxial NTE and NLC along X1 is observed, whilst for A = TPC5TP²⁺ uniaxial NTE and positive compressibilities are found. For temperature‐dependent data, filled and open symbols represent heating and cooling, respectively. e,f) show a 2 × 2 × 2 perovskite‐type unit with the particular direction of propagation for the principal axis X1 illustrated, respectively. Color code: green/dark blue: A‐cation N, pink: Mn. Note that the black lines are only a guide to the eye to indicate the perovskite‐type connectivity and do not represent real chemical bonds.
Article
Engineering the interplay of structural degrees of freedom that couple to external stimuli such as temperature and pressure is a powerful approach for material design. New structural degrees of freedom expand the potential of the concept, and coordination polymers as a chemically versatile material platform offer fascinating possibilities to address this challenge. Here, we report a new class of perovskite‐like AB2X6 coordination polymers based on a [BX3] ⁻ ReO3‐type host network ([Mn(C2N3)3] ⁻), in which the spatial orientation of divalent A²⁺ cations ([R3N(CH2)nNR3]²⁺) with separated charge centers that bridge adjacent ReO3‐cavities is introduced as a new geometric degree of freedom. Herringbone and head‐to‐tail order pattern of [R3N(CH2)nNR3]²⁺ cations are obtained by varying the separator length n and, together with distortions of the pseudocubic [BX3] ⁻ network, they determine the materials’ stimuli‐responsive behavior such as counterintuitive large negative compressibility and uniaxial negative thermal expansion. This new family of coordination polymers highlights the chemists’ capabilities of designing matter on a molecular level to address macroscopic material functionality and underpins the opportunities of the design of structural degrees of freedom as a conceptual framework for rational material synthesis in the future.
 
Article
Traumatic brain injury (TBI) is the main cause of death and disability in people of all ages worldwide. Neuroinflammation plays beneficial and harmful roles in secondary brain injury. Neutrophils play an important role in chemically mediated inflammatory responses through myeloperoxidase (MPO) and inflammation triggered by TBI. Herein, a nanodrug targeting neutrophils and MPO through chemical and biological functions after TBI is designed to enhance the retention and sustained release of drug cargos for improved TBI therapy. 5‐Hydroxytryptamide (5‐HT) is modified on nanoparticles (NPs) loaded with an anti‐inflammatory and antioxidant natural product, hesperetin, to obtain MPO‐ and neutrophil‐targeting NPs, denoted as T‐Hes. In a mouse TBI model, it is confirmed that neutrophil‐targeting NPs can quickly accumulate and remain in the brain tissue, reduce the secretion of inflammatory factors, and the level of microglia and astrocytes, subsequently inducing the transformation of microglia from pro‐inflammatory M1 to anti‐inflammatory M2 cells and promoting the infiltration of regulatory T cells (Tregs). T‐Hes significantly inhibits neuroinflammation and improves neurological deficits through the sustained release of hesperetin in the brain. The findings may open up new avenues for designing clinically translatable probes for TBI treatment.
 
Article
Blue phases (BPs) are soft and stimuli‐responsive photonic crystals that are interesting for sensing, display, and lasing applications. Polycrystallinity has, however, limited both the study and applicability of BPs. Continuum simulations, which lack molecule‐specific details, predict that striped chemical patterns, consisting of alternating homeotropic and planar regions, can be used to nucleate single crystals of BPs. Here it is experimentally demonstrated that, independent of the chemistry and complexity of the BP forming material, chemical patterns direct the self‐assembly of BPs; these results indicate that a general, thermodynamics‐based continuum description of BP self‐assembly is adequate for a broad range of materials. When the pattern periodicity equals the BPII unit cell size, single crystals with (100) orientation form for all studied materials. Chemical patterns also promote the growth of BPI crystals with (110) orientation. Importantly, the self‐assembly of a photopolymerizable BP is directed and thermally stable, UV‐polymerized single crystals are prepared. The ability to create arbitrarily large, polymeric photonic single crystals with uniform lattice orientation, may have broad implications for optical applications. Chemically patterned surfaces with alternating homeotropic and planar regions promote the growth of BP single crystals and monocrystals with different chemical composition. Pattern design is based on predictions of continuum simulations. By directing the assembly of different BPs, a colorful range of single crystals and monocrystals is obtained. The blue‐phase structure can be made thermally stable through photopolymerization.
 
Article
The application of nanotechnology in medicine aims at developing the precise theranostics of diseases by leveraging the extraordinary effects of engineered nanomedicines, materdicine, and biomaterials. However, finely controlling the biological behavior of nanomaterials in the complex living systems remains a great challenge in terms of accuracy and intelligence. Inspired by nature, biomimetics has become an attractive strategy based on the highly ordered natural biological structure for the development of clinically valuable materials and technologies, arising from the superior bioavailability. The rapid development of biomimetics in nanomedical applications prompts the authors to propose the concept of “nanobiomimetic medicine”, which is a considerable subdiscipline in nanomedicine and materdicine that applies the concept and strategies of biomimetics to facilitate and promote the disease theranostics. Herein, the authors aim to furnish a state‐of‐the‐art review on the latest progress in the field of nanobiomimetic medicine. The design strategies, structural features and biological properties of biomimetic materials are initially introduced to reveal the inherent bionic mechanism and the potential structure‐function relationships. Furthermore, advances with respect to the applications of diverse biomimetic materials are comprehensively summarized. Finally, the current challenges and future direction of nanobiomimetic medicine are discussed and prospected in order to stimulate more biomimetic fundamental and technological breakthroughs in nanomedicine. The rapid development of biomimetics in nanomedical applications prompts the authors to propose the concept of “nanobiomimetic medicine”. The latest progress in the field of nanobiomimetic medicine are comprehensively summarized in order to stimulate more biomimetic fundamental and technological breakthroughs in nanomedicine and materdicine.
 
Article
The regeneration and repair of complex structures, interfaces, and mechanical properties present in natural tissues remains a challenge. To move beyond simplified tissue engineered constructs, nature is a source of inspiration for complex, hierarchical scaffold designs. Recent advances in additive manufacturing allow for increasingly complex fabrication of architectures that better mimic the multiscale structure‐function relationship found in natural tissues. In this review, scaffold‐based and scaffold‐free approaches and the synergistic use of fabrication technologies (two things make a third) to produce more biomimetic implants are described. Recent advanced scaffold designs such as auxetic mechanical metamaterials and induced fibrillar alignment are highlighted. Next, the pre‐programmed assembly of spheroids, tissue strands, and other modular building blocks without the need for permanent exogenous scaffold support are discussed. Furthermore, the application of hybridized manufacturing processes to fabricate hierarchical functional constructs is outlined for the osteochondral unit, vascular grafts, and peripheral nerves.
 
Article
Over the past two decades, the unique features of ionic liquids (ILs) drive their exploration and exploitation in gel field and endow the gels with many excellent properties including thermal stability, antifreezing capability, mechanical strength, self‐healing, conductivity, and antibacterial performance. As promising functional materials, ionogels have attracted remarkable interest in various applications including flexible electronics, energy storage, and biomedical applications. This review aims to give a detailed overview of the recent advances in developing of IL‐based task‐specific ionogels. The effects of ILs on the ionogels’ formation and structure modification and their promotion on elevating these gel properties from the viewpoint of fundamental to the application are comprehensively discussed. The different interactions also discussed between ILs and other components in forming ionogels, such as hydrogen bond, electrostatic interaction, host–guest interaction, IL‐philic and IL‐phobic interaction, and introduced ILs’ dissolvability to biomass; and the unique capability of ionogels owing to ILs, such as conductivity, electrochemical stability, thermal stability, and antibacterial ability. Finally, the future challenges and perspectives of ionogels are outlooked.
 
Theoretical design (a–d) and experimental development (e) of lead‐free relaxor‐ferroelectric piezoceramics with large strains and low hysteresis over a broad temperature range. a) Microstructural evolution of the BNT‐based system with x = 0.01, 0.02, 0.03, and 0.04, at different temperatures, upon cooling, as assessed using phase‐field simulations. The gray color encodes the paraelectric state, while the other colors capture ferroelectric domains, with arrows showing the polarization direction. The system becomes more relaxor‐like with increasing doping and/or temperature, while low doping and/or temperature can induce the ferroelectric phase. b) Calculated P–E and S–E loops at 15 °C for a range of doping concentrations (i.e., x = 0.01, 0.02, 0.03, and 0.04). c) Amplified views into the microstructure evolution of the BNT‐based system with x = 0.03, upon cooling. The color contour represents the domain size, while the arrows’ length captures the polarization magnitude. d) Unipolar S–E loops, for the BNT‐based system with x = 0.03, for temperatures in the 15–125 °C range. e) Electric field‐induced strains versus temperature and their corresponding strain hysteresis, for our BNBT‐KNLNS3 (tested at 55 kV cm⁻¹) and the state‐of‐the‐art lead‐free piezoceramics reported in the literature, including NBKLST‐SBSZN (tested at 60 kV cm⁻¹),[³⁷] BNT‐BT (tested at 60 kV cm⁻¹),[⁷] BF‐BT (tested at 40 kV cm⁻¹),[³⁸] BFS‐BT‐BZH (tested at 60 kV cm⁻¹),[³⁹] KNN‐CZ (tested at 40 kV cm⁻¹),[⁸] and KNLN‐BZ‐BNT (tested at 30 kV cm⁻¹).[⁴⁰] The bubble size represents the degree of hysteresis.
High‐performance BNBT‐KNLNS3 with large strain and low hysteresis over a broad temperature range. a) Bipolar P–E and b) S–E curves of BNBT‐KNLNS100x (x = 0.01, 0.02, 0.03, and 0.04), respectively, measured at 25 °C and 1 Hz. Ceramic pellets (thickness, 0.8 mm; diameter, 8 mm) were tested for all electrical properties. c) Unipolar S–E curves of the BNBT‐KNLNS3 ceramic, for temperatures in the 25–125 °C range. d) Evolution of the Smax/Emax ratio and hysteresis as a function of temperature, for BNBT‐KNLNS3 (hysteresis was defined as ΔSmax/Smax). e) Comparison of the Smax/Emax ratio, Smax, and hysteresis for our BNBT‐KNLNS3 with those for the state‐of‐the‐art lead‐free piezoceramics (including KNN‐CZ,[⁸] BNT‐BT,[⁷] and NBKLST‐SBSZN[³⁷]) at 125 °C.
BNBT‐KNLNS3 with the MPB structure. a) Neutron diffraction refinement for BNBT‐KNLNS3 at 25 °C, demonstrating a good fit between the final refinement profile and experimental data. The insets show the crystal structure (rhombohedral and tetragonal) of BNBT‐KNLNS3, constructed based on their refined data. b) The content percentage of rhombohedral (R) and tetragonal (T) phases in the BNBT‐KNLNS3 ceramic, based on the refined results. c) Schematic of the BNBT‐KNLNS3 unit cell. The B‐site displacement vector along the diagonal direction in the xy plane, and c (out‐of‐plane) and a (in‐plane) lattice parameters are marked. d) Atomic‐resolution HAADF‐STEM image of BNBT‐KNLNS3 along the [010] zone axis. Scale bar = 2 nm. e) The B‐site atom displacement vector maps based on (d). The purple arrows represent the direction of the B‐site atom shift, and the arrows’ length denotes the magnitude of the B‐site atom displacement. The regions encircled by red and blue suggest rhombohedral and tetragonal symmetries, respectively. f) Tetragonality (c/a) mapping of BNBT‐KNLNS3, obtained by calculating the corresponding atomic positions in (d); this demonstrates the coexistence of rhombohedral and tetragonal symmetries.
Temperature dependence of the BNBT‐KNLNS3 structure. a) Temperature dependence of dielectric permittivity (ε´) and loss (tanδ) of the BNBT‐KNLNS3 ceramic measured at 1, 10, and 100 kHz. b) The content percentage of the rhombohedral (R) and tetragonal (T) phases in BNBT‐KNLNS3 as a function of temperature, based on the refined results of in situ XRD (Figure S8, Supporting Information). c) Raman spectra fitted by Lorentzian peak functions, for the BNBT‐KNLRNS3 ceramic at 30, 80, and 130 °C. d) Raman spectra mapping at 470–640 cm⁻¹ for the BNBT‐KNLNS3 ceramic, for temperatures in the 30–130 °C range. e–g) In situ TEM images of the BNBT‐KNLNS3 ceramic upon heating at 25 °C (e), 125 °C (f), and 300 °C (g), and their corresponding selected area electron diffraction patterns (collected at the black dotted circle in TEM images). The 1/2{ooo} (red circle) and 1/2{ooe} (blue square) superlattice diffraction spots, representing the presence of the rhombohedral (R) and tetragonal (T) phases, respectively.
Origin of low‐hysteresis large strains over a broad range of temperatures, as revealed by in situ PFM. a) PFM amplitude images (imaged area: 2 µm × 2 µm) of BNBT‐KNLNS3 at 30, 70, and 115 °C. b) Triangular‐waveform voltage applied to the BNBT‐KNLNS3. For reference, the macroscopic unipolar S–E curve of the BNBT‐KNLNS3 at 125 °C is shown in the inset. c) Averaged local hysteresis loops for the ferroelectric and ergodic relaxor states of BNBT‐KNLNS3, measured at 30 °C. d) Temperature dependence of the ferroelectric and ergodic relaxor states of BNBT‐KNLNS3. e–g) Band‐excitation switching spectroscopy amplitude images of BNBT‐KNLNS3 at steps 0 (e), 16 (f), and 32 (g) (marked in Figure 5b), measured at 115 °C.
Article
Bismuth sodium titanate (BNT)‐based lead‐free piezoceramics are promising for replacing lead‐based piezoceramics in piezoelectric actuators due to their large strains. However, achieving low‐hysteresis large‐strain BNT‐based ceramics over a broad temperature range is challenging, owing to the complexity of the composition design and phase transformation. Herein, a lead‐free relaxor‐ferroelectric (1−x)Bi0.47Na0.47Ba0.06TiO3‐xK0.47Na0.47Li0.06Nb0.99Sb0.01O2.99 system (BNBT‐KNLNS) near the morphotropic phase boundary (MPB), achieved by phase‐field simulations and rational composition design (i.e., BNBT with the MPB as the base and the ferroelectric phase of KNLNS as the dopant) is reported. This ceramic exhibits large strains (0.32–0.51%) and low strain hysteresis (11.1–59.9%) over a wide temperature range (25–125 °C), outperforming many state‐of‐the‐art lead‐free piezoceramics. A small fraction of ferroelectric states embedded in the relaxor matrix is experimentally observed, where these states act as seeds, facilitating the reversible relaxor‐to‐ferroelectric transition. In addition, the MPB composition with low energy barriers yields large strain responses, owing to the easy polarization reversal and extension. Consequently, low‐hysteresis large strains are obtained over a broad temperature range. This work provides a novel design route for discovering high‐performance piezoceramics for actuator applications.
 
Article
It is of great challenge to design transition multimetallic carbonate hydroxides with delicate hollow features and defects for efficient electrolytic oxygen evolution reaction (OER). Here, a sequential self‐templating method to synthesize CoNiFe trimetallic carbonate hydroxide hierarchical hollow microflowers (CN‐xFe HMs) with oxygen vacancies (VO) is reported. The synergistic merits of hollow structure, Fe substitution, and VO endow the CN‐xFe HMs with high active‐site exposure density and increased electrical conductivity. Specially, the optimized CN‐xFe HMs validate the excellent OER performance with an overpotential of 258 mV to drive 10 mA cm⁻² and a Tafel slope of 48.7 mV dec⁻¹. Theoretical calculations reveal that Fe substitution and VO can synergistically regulate the electronic states to achieve near‐ideal adsorption/desorption capacity for oxygenated intermediates. Moreover, the successful synthesis of other six metals substituted CoNiM (M = Cu, Zn, Cr, Mo, Er and La) carbonate hydroxides provides a universal protocol to construct transition multimetallic electrocatalysts with hollow structures for gaining highly efficient energy conversion reactions.
 
Article
Reversible silver electrodeposition (RSE) can dynamically modulate visible light and infrared radiation through the reversible electrodeposition and dissolution of silver layer. However, the RSE device with bistability better than 2 h has not been reported, because the deposited silver layer may dissolve automatically without driving voltage. Here, a variable infrared emissivity device based on RSE with 24 h excellent bistability is demonstrated. A silver layer fixed at the counter electrode is used as the charge mediator, which reforms the electrochemical reactions of the counter electrode and is the key for obtaining bistability. Effects of electrolyte composition and driving voltage on the bistability are studied, and the driving voltage affects the bistability of RSE devices. This RSE device can be enlarged to 5 × 5 cm² with uniform emissivity change of 0.48 in 2.5–25 µm using silicon wafer as the infrared transparent working electrode substrate, and display discontinuous thermal patterns through incorporating a dielectric pattern layer. The cyclability and device failure mechanism is analyzed. With the excellent bistability, the proposed RSE devices provide great application prospects in the fields of dynamic infrared information display, adaptive infrared camouflage, and smart thermal management.
 
Article
The human health is still threatened by refractory keratitis and diabetic foot ulcers caused by bacterial infections, hypoxia, and chronic inflammation, so that patients are exposed to the risk of amputation, vision loss, and even death. Herein, an oxygen‐producing double‐layered hydrogel is developed that can visualize bacterial infections and supply oxygen to enhance antimicrobial photodynamic therapy (PDT) and inflammation alleviation for diabetic wounds healing. The inner layer hydrogel (containing oxidized sodium alginate/carboxymethyl chitosan [CMCS] via Schiff‐base) is incorporated with a photodynamic metal–organic framework (PCN‐224) and a pH indicator (bromothymol blue). The outer layer hydrogel (containing agarose and CMCS) loads photosynthetic cyanobacteria that continuously generate oxygen to relieve hypoxia of tissue and enhance antimicrobial PDT efficiency. Meanwhile, some unique advantages are reflected by continuous oxygen supply under natural light, such as cell migration acceleration, inflammation relief, promotion of skin capillary formation, and wound tissue recovery. Therefore, the self‐oxygenated double‐layered hydrogel offers tremendous benefits in the synergistic treatment of refractory anaerobe wounds from timely infection monitoring to tissue repair.
 
A) Schematic overview of the system. A glass substrate was treated with (3‐aminopropyl) triethoxysilane (APTES) or Sigmacote to increase surface hydrophobicity and allow the development of more stable and denser biofilms. Then, an L. lactis biofilm was developed on the silanized surface. Human bone marrow‐derived mesenchymal stem cells were cocultured with the L. lactis biofilm for variable amounts of time. B) L. lactis NZ9020 were electrotransformed with plasmids carrying ORFs for human CXCL12, TPO, VCAM1, and FN III7–10. Each bacterial population was engineered to produce a single recombinant protein. TPO and CXCL12 were secreted extracellularly using the lactococcal usp45 secretion peptide. VCAM1 and FN III7–10 were cloned upstream the S. aureus protein A domain that contains the LPETG motif, that allows for a covalent linking to the peptidoglycan cell wall of the bacteria, effectively displaying the proteins in the bacterial cell wall. C) Schematic of the plasmid constructs. All proteins were placed under the control of the strong constitutive lactococcal P1 promoter followed by the phage T7 gene 10 5'‐UTR and RBS. Usp45sp was used as a secretion signal, followed by the gene of interest and the C‐terminal end (residues 268–457) of S. aureus protein A for cell wall binding. D) Protein expression levels were measured using a competitive ELISA against the 6xHis tag present in the CXCL12, TPO, and VCAM1 plasmids. M17, the L. lactis culture medium, supplemented with 0.5% glucose, was used as a negative control. FN was not included in this graph because its expression level was determined in a previous work—fully developed biofilms expressed FN at a concentration of 6.32 ng cm–2.[¹⁰]
Biofilm characterization. A,B) Viability of the biofilms used in the coculture experiments, produced by combining CXCL12 (C), TPO (T), and VCAM1 (V) at different ratios and the control strain, were determined after 5 or 10 d using the FilmTracer viability kit. Viability values don not show a statistically significant difference (p ≥ 0.05) between the different strains and time points. Panel (A) shows representative images showing biofilms’ viability on the different tested surfaces and culture media. In this case, the C/T biofilm is depicted and GM17 and DMEM were used to compare the different culture conditions and their effect on the bacterial biofilm. No statistically significant differences were found (p ≥ 0.05) between the different time points or conditions. C) Biofilm area density, here shown L. lactis‐CXCL12, as in percentage of area covered by the bacterial biofilm, was determined for the same conditions used in panels (B) and (C) at the same time points. Surfaces treated with Sigmacote kept a higher biofilm density compared to APTES, and DMEM showed the higher values. Panel (D) shows biofilms’ viability on the different tested surfaces and culture media. In this case, GM17 and DMEM were used to compare the different culture conditions and their effect on the bacterial biofilm. No statistically significant differences were found (p ≥ 0.05) between the different time points or conditions. We acknowledge a reduced viability value on days 5 and 9 for GM17 in Sigmacote but no statistically significant difference was found with the available data and this trend could be attributed to leaving the L. lactis cells in GM17, which reaches a pH around ≈5 and has a detrimental effect on cell viability. Longer term cultures have been done in DMEM at a physiological pH of 7.4, which has a less detrimental effect as seen in the graph. A representative phase contrast image of a biofilm cultured in Sigmacote‐DMEM for 9 d is shown in the image on the right. Results were obtained by counting the number of live bacteria per field of view, in three biological replicates, and three individual experiments. The displayed data represent mean ± S.E.M. and was analyzed with a Student's t‐test.
A) Cell area of hMSCs cultured on biofilms expressing CXCL12, TPO, VCAM1, and FN (note this is FN IIII7–10) was measured by image analysis and was compared to an EMPTY biofilm as well as hMSCs grown on FN‐coated and bare glass coverslips. Cells grown on CXCL12, TPO, VCAM1, and EMPTY biofilms were significantly smaller in size compared to cells grown on the FN‐expressing biofilm and the two glass coverslip conditions (A minimum of 15 cells per biological replicate and per condition were analyzed) after a one‐way nonparametric ANOVA with Kruskal‐Wallis post hoc test (α = 0.05, **** p < 0.001). Data presented as mean ± SD. B) Actin‐stained hMSCs cultured on the different biofilms. C) hMSC viability on L. lactis biofilms. Representative images of the live/dead assay are shown for each condition. Viable hMSCs are displayed in green, while no nonviable hMSCs were recorded (red channel). This might be due to dead cells being washed away to prepare the staining, a known limitation of this technique. hMSC viability of cells cultured on CXCL12, TPO, FN, VCAM1 for 3 and 5 d was determined with a mammalian viability kit (Thermofisher). No nonviable (red‐stained) cells were found. Thus, we infer that there were only a limited number of nonviable cells across the different tested conditions. ANOVA; analysis of variance, SD; standard deviation.
Motility experiments and cell speed and trajectories. Human MSCs were seeded on L. lactis biofilms in either 2D or 2.5D conditions and were tracked at different time points. A) The cells were initially tracked for 24 h, with 5 min intervals after an initial overnight incubation to allow cells to adhere to the substrate. The average speed by cell was recorded and comparisons were drawn between the cells incubated with and without the presence of a hydrogel and between the different biofilm conditions. B–D) Cells were incubated on top of L. lactis biofilms in the presence of either a nondegradable (PEG) or a degradable (VPM) hydrogel. Cell speed was measured after tracking for 1 h with 2 min intervals on days 3, 5, and 7 of the cocultures. Data presented as mean ± SD and analyzed with ANOVA with a Tukey post hoc test. A minimum of 15 cells were measured per condition, in three independent experiments. Significance levels are ∗p < 0.05, ** p< 0.01, *** p < 0.001, **** p < 0.0001; ANOVA, analysis of variance; SD, standard deviation.
hMSC were phenotyped using in‐cell Western to analyze relative expression of ALCAM, nestin, Stro1, osteopontin, and osterix. Analysis was performed after a 14 d coculture with the biofilms depicted in the graphs, namely CXCL12, TPO, VCAM1, FN, osteogenic medium (OSTEO), and glass‐only control (hMSCs). The results were normalized against beta actin and are displayed as the relative expression of each marker against the housekeeping gene. A–C) No statistical difference was observed between the stemness markers expressed by the control hMSCs and the stem cells cultured on L. lactis. D–E) Interestingly, increased expression of osteogenic differentiation markers osteopontin and osterix was not observed in any of the conditions except for the osteogenic medium, (*** p < 0.001) compared to the rest of the conditions (two‐way ANOVA with Tukey post hoc test) and in the OSX graph (* p < 0.05, ** p< 0.01, *** p < 0.001 compared to the reference condition, osteo, labeled as #). F) Assessment of the hMSC expression of Pref‐1 after 14 d of culture also suggests that the stem cells cultured on the biofilms expressing TPO, VCAM1, and FN do not display a trend toward adipogenic differentiation. G,H) The maintenance of the differentiation potential of hMSCs cocultured with L. lactis was evaluated after 14 d. No statistical difference was observed between the hMSCs and osteogenic control, suggesting the maintenance of the capacity of the stem cells to differentiate after long term cultures on the biofilms. A minimum of 15 cells were measured per condition, in three independent experiments. Data presented as mean ± SD and analyzed with ANOVA with a Tukey post hoc test. These data suggest a possible influence of the L. lactis biofilms in keeping an hMSC‐like phenotype for up to 14 d in coculture without committing to the osteogenic lineage. SD; standard deviation.
Article
Living interfaces are established as a novel class of active materials that aim to provide an alternative to traditional static cell culture methods by enabling users to accurately control cell behaviour in a precise, dynamic, and reliable system‐internal manner. To this day, the only reported biointerface has been a coculture between a biofilm of nonpathogenic genetically engineered bacteria and mammalian cells, where the recombinant proteins produced by the bacteria directly influence cell behaviour. In this work, a biointerface is presented between Lactococcus lactis (L. lactis) and human mesenchymal stem cells (hMSCs). L. lactis have been engineered to produce human C‐X‐C motif chemokine ligand 12, thrombopoietin, vascular cell adhesion protein 1, and the 7th–10th type III domains of human fibronectin, with the aim of recreating the native bone marrow conditions ex vivo. This active microenvironment has been shown to maintain key hMSC stemness markers, preventing their osteogenic and adipogenic differentiation, and maintaining high stem cell viability and physiological cell‐to‐substrate adhesion dynamics. This work presents proof of concept data that hMSC stemness can be regulated by living materials, using a system based on the symbiotic interaction between different engineered bacteria and mammalian cells.
 
a) Thermovoltage Uth versus temperature difference ΔT across the solid polymer electrolyte measured for a LiTFSI salt concentration of cLiTFSI = 0.2 mol kg⁻¹ (sample SPE2) at room temperature. The slope of the linear fit to the data yields a Seebeck coefficient of S = (− 0.96 ± 0.01) mV K⁻¹. The data has been corrected for parasitic offset voltages. b) Seebeck coefficient S as a function of device temperature for different concentrations cLiTFSI = 0.0 mol kg⁻¹ (SPE0, teal pentagons), cLiTFSI = 0.2 mol kg⁻¹ (SPE2, blue diamonds) and cLiTFSI = 0.5 mol kg⁻¹ (SPE5, green dots), respectively. For each sample, a temperature TS,max can be identified where |S| reaches a maximum, indicating a balance between thermal activation and repulsive interaction of mobile ions for a given concentration, and decreases with increasing concentration cLiTFSI. TS,max for the respective sample is indicated by arrows.
a) Temperature dependent Nyquist plots of a symmetrical Cu/solid polymer electrolyte/Cu cell. Measurements performed on a sample with cLiTFSI = 0.1 mol kg⁻¹. Black dashed lines display the respective fits according to the electrical equivalent circuit shown in (b). Here, the sample is described by the dielectric capacitance CD and a double layer capacitance CDL connected in series with the bulk resistance Ri, which is related to the ionic conductivity σ for the given cell geometry. A resistance RS was added in order to account for possible series resistances. c) Ionic conductivities in the polymer matrix derived from impedance spectra (blue dots). The thermal activation behavior can be described by a Vogel– Fulcher– Tammann (VFT) ansatz (green solid line) which yields an activation energy of EA = (42 ± 5)meV and a Vogel temperature of TV = (196 ± 7)K.
a) Nyquist plots of impedance data measured at 273, 293, 323, and 353 K for sample SPE0CNT (cLiTFSI = 0.0 mol kg⁻¹ and 0.4 wt% carbon nanotubes). The spectra clearly deviate from those before as the semi‐circle and broad arc feature at low frequencies are characterized by an increase in conductivity by more than two orders of magnitude. b) Applying Tikhonov regularization, the DRT shows two clearly distinguishable agglomeration points. The first one, between τ = 10⁻⁶ to 10⁻⁵ s, shows a distinct temperature dependence. The second, smeared‐out group at around τ = 10⁻¹ s refers to a diffusive charge transport behavior. c) Conductivities derived from the first semi‐circle of the impedance data (see also Figure S5, Supporting Information) plotted as a function of inverse temperature. The temperature dependent total conductivity σ (blue bullet points) can be modeled by overlapping Vogel– Fulcher– Tammann (green line) and Arrhenius type (gray line) transport models (σ = σVFT + σArr., yellow line), with VFT becoming dominant for higher temperatures. Fit results for the VFT contribution (Ea = (22 ± 14) meV, Tv = (249 ± 40) K) are in good agreement to the polymer‐only sample (SPE0) without carbon nanotubes added. Obviously, a change in the dominant transport mechanism is evident at around Tc = 300 K. The Arrhenius type transport can be described by an activation energy of Ea = (42 ± 28) meV.
Seebeck coefficient S versus the bulk conductivity displayed in a symlog‐log‐plot. The y‐axis is a symmetrical logarithmic axis with an axis break around zero thus allowing to display positive and negative values on a logarithmic scale. Gray dashed lines indicate iso‐powerfactors as key parameter for TE application. Different samples are indicated by the respective shape of the data points; the temperature range for measurements (263–363 K) is color coded. Samples SPE0CNT and SPE2CNT, both containing carbon nanotubes, show a change in sign.
a) Scheme of the mixed electronic and ionic thermoelectric generator built as proof‐of‐concept device. A temperature difference of ΔT is applied across the two legs. The SPE leg contains a polymer blend with a concentration of cLiTFSI = 0.2 mol kg⁻¹ and 0.4 wt% of carbon nanotubes exhibiting a negative thermovoltage above Tc = 303 K, and a positive one below. The second PEDOT:PSS polymer leg shows a positive Seebeck coefficient. b) The power output characteristics for a temperature gradient of ΔT = 10 K at different temperatures Tmed = 283, 313, and 343 K is shown. To estimate the power output of the TEG various load resistances RL have been connected in series and the occurring current flow has been measured and integrated for a duration of 60 s. The dashed lines are guide‐to‐the‐eyes and indicate the trend in the data around Tmed. The observed behavior corroborates an operational mode where the TEG can be switched on/off at Tmed.
Article
Thermoelectric materials utilizing ionic transport open‐up entirely new possibilities for the recuperation of waste heat. Remarkably, solid state electrolytes which have entered the focus of battery research in recent years turn‐out to be promising candidates also for ionic thermoelectrics. Here, the dynamics of ionic transport and thermoelectric properties of a methacrylate based polymer blend in combination with a lithium salt is analyzed. Impedance spectroscopy data indicates the presence of just one transport mechanism irrespective of lithium salt concentration. In contrast, the temperature dependent ionic conductivity increases with salt concentration and can be ascribed to a Vogel–Fulcher–Tammann (VFT) behavior. The obtained Seebeck coefficients of 2 mV K⁻¹ allow for high power outputs while the polymer matrix maintains the temperature gradient by its low thermal conductivity. Adding multi‐walled carbon nanotubes to the polymer matrix allows for variation of the Seebeck coefficient as well as the ionic and electronic conductivities. As a result, a transition between a high temperature VFT regime and a low temperature Arrhenius regime appears at a critical temperature, Tc, shifting upon addition of salt. The observed polarity change in Seebeck voltage at Tc suggests a new mode of thermoelectric operation, which is demonstrated by a proof‐of‐concept mixed electronic‐ionic‐thermoelectric generator.
 
a) Schematic diagram depicting the preparation and function of MXene‐GF separator. b) Digital photos of bare GF and MXene‐GF. The inks used for printing with different concentrations are displayed as the insets. The marked number represents x mg mL⁻¹, x = 0, 1, 3, and 5. c) Schematic illustration of the polarized charge distribution within different separators. d) Digital photo of a MXene‐GF sheet with a diameter of 11 cm.
a) AFM image of Ti3C2Tx MXene flakes, showing a typical thickness of 2 nm. b) TEM and c) HRTEM image of a Ti3C2Tx MXene flake. d) Top‐view SEM image of MXene‐GF. e) High‐resolution XPS C 1s spectrum of MXene‐GF. f) XRD patterns of MXene‐GF and GF. g) Digital photos showing the contact angles of water dropped over GF and MXene‐GF. h) Polarization‐electric field (P‐E) loops of GF and MXene‐GF.
a) Comparison of cycling performances of symmetric cells based on different MXene‐GF separators at 5 mA cm⁻² with a capacity of 5 mA h cm⁻². b) Cycling performances of symmetric cells based on MXene‐GF and GF at 1 mA cm⁻² with a capacity of 1 mA h cm⁻². c) Rate performance of symmetric cells based on MXene‐GF and GF. Top‐view SEM images of d) bare Zn and e) protected Zn after 20 cycles under 1 mA cm⁻²/1 mA h cm⁻². f) Coulombic efficiencies tested based on Ti–Zn cells affording MXene‐GF and GF separators at 2 mA cm⁻²/0.5 mA h cm⁻². g) XRD patterns of cycled Zn with/without the protection of MXene‐GF. h) Tafel curves for GF and MXene‐GF in symmetric cell configurations.
Nyquist plots at different temperatures of a) MXene‐GF and b) GF. c) Corresponding fitted Arrhenius curves. d) In situ OM visualization of Zn plating with/without MXene‐GF at 5 mA cm⁻². Scale bars: 100 µm. e) CA curve of MXene‐GF with the potential of 10 mV. Inset: Corresponding Nyquist plots before and after CA test. Simulated electrical field distribution for f) GF and g) MXene‐GF. h) Galvanostatic cyclic performances of symmetric cells based on GF and MXene‐GF under 1 mA cm⁻²/1 mA h cm⁻² using 0.01 m ZnSO4 electrolyte.
Electrochemical performances of AZIB full cells equipped with MXene‐GF separators. a) Schematic representation of AZIB full cells equipped with GF or MXene‐GF as separators. b) CV curves at a scan rate of 0.1 mV s⁻¹. c) CV profiles of full cell affording MXene‐GF at different scan rates. d) Linear curves of the fitted b values. e) Rate performances of full cells based on GF and MXene‐GF. f) Long‐term cycling performances at 5.0 A g⁻¹ for 1000 cycles. g) Digital photos showing the pouch‐type cells with MXene‐GF as the separator to power an electronic timer at different bending states.
Article
Separator modification has recently blossomed as an effective strategy to enable dendrite‐free Zn metal anodes. Nonetheless, the explored avenues are not conducive to mass production by far, and little attention is paid to the essence of separator regulation. Herein, a scalable Ti3C2Tx MXene‐decorated Janus separator is designed by spray‐printing MXene nanosheets over one side of commercial glass fibre (GF). The thus‐derived MXene‐GF separator affords abundant surface polar groups, good electrolyte wettability, and high ionic conductivity, which is beneficial to homogenizing local current distribution and promoting Zn nucleation kinetics. It is noted that MXene‐GF displays adjustable dielectric constants with an optimized value of 53.5, offering a directional electrical field to expedite Zn‐ion flux and repel anions. Accordingly, dendrite‐free Zn anode equipped within symmetric cells can be achieved with MXene‐GF, enabling a stable cycling for 1180 h at 1 mA cm⁻² and 1200 h at 5 mA cm⁻². More impressively, the assembled aqueous Zn‐ion battery full cell with Janus MXene‐GF separator realizes a favorable capacity retention ratio (77.9%) upon cycling for 1000 cycles at 5.0 A g⁻¹. This strategy with scalability and effectiveness offers a new insight into high‐performance metal anodes.
 
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6 days
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18%
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$5,100 / £3,850 / €4,450
APC
19.924 (2021)
Journal Impact Factor™
26.6 (2021)
CiteScore
Top-cited authors
J.C. Hummelen
  • University of Groningen
Christoph J. Brabec
  • Friedrich-Alexander-University of Erlangen-Nürnberg
Zhong Lin Wang
  • Georgia Institute of Technology
Hui-Ming Cheng
  • Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Chinese Academy of Sciences
Yang Yang
  • China National Rice Research Institute