[Show abstract][Hide abstract] ABSTRACT: A two-component light-harvesting organogel containing a naphthalimide-based gelator () as a donor and a phosphorescent Ir(iii) complex [Ir(bt)2(acac)] (bt = 2-phenylbenzothiazole and acac = acetylacetone) () as an acceptor was used to produce white-light-emitting organogels. The addition of complex to the gel had a certain effect on the self-assembly behaviour of molecule , but did not affect the gelation ability, mechanical strength and structure surface wettability of the gel. The optical properties of the two-component gel could be tuned via high intermolecular energy transfer efficiency between and complex , which was confirmed by geometry optimizations and harmonic vibrational analyses. The white-light-emitting organogel was obtained with the molar ratio of complex in the range of 0.3-1.0. In particular, the gel with the addition of 0.5 equivalent of could emit white-light with the Commission Internationale de L' eclairage (CIE) coordinates of 0.33 and 0.31 under the excitation of 374 nm light.
Full-text · Article · Nov 2015 · Physical Chemistry Chemical Physics
[Show abstract][Hide abstract] ABSTRACT: Acquiring high-quality integrated nanographene sheets (nGs) and mitigating their self-aggregation are highly essential to achieving their full potential in energy related applications. The insertion of enthetic spacers into nGs layers can relieve the stacking problems but always results in a change in the intrinsic properties of the nGs and/or the introduction of complexity at the interfaces. In this work, a facile and scalable strategy is used to construct highly integrated, intrinsically coupled, N, S-doped 3D nanographene sheets trapped within carbon nanotubes (nGs@CNTs) through a modified counterion intercalation. The as-obtained nGs@CNTs are composed of two building blocks, in which large amounts of integrated unzipped nanoscale graphene sheets are tightly attached to the intact inner walls of the CNTs. The remaining CNTs serve as inherent spacers to prevent the self-stacking of nGs. Benefiting from the permanent and robust column bracing frameworks, the resultant 3D aerogels are expected to act as effective electrode materials for lithium-ion batteries with superior cyclic performance, delivering a reversible capacity as high as 1089 mAh g-1 at a current density of 2 A g-1 even after 300 cycles. The good lithium-ion storage performance is attributed to the hierarchical porous feature, the intrinsically unstacked bridged structure, and the synergistic effects between the N and S. This promising strategy represents a new concept for mitigating the self-aggregation of nGs by using autologous spacers.
No preview · Article · Oct 2015 · Chemistry of Materials
[Show abstract][Hide abstract] ABSTRACT: Two large conjugated naphthalimide derivatives with or without three-methane-bridged thiazole orange (TO3; i.e., compounds 1 a and 2 a, respectively) were designed and synthesized. The fluorescence of the naphthalimide group in compound 1 a at λ=532 nm initially decreased and that for the TO3 group at λ=655 nm increased sequentially upon adding Salmon testes (St) DNA. In contrast, without the TO3 group, the fluorescence intensity of compound 2 a monotonously decreased in response to the addition of DNA. The non-monotonic change in the fluorescence for compound 1 a could be divided into two linear sections with two different wavelengths in the range of 0<Rb/1 a <1.2 and 1.2 <Rb/1 a <6.0 (Rb/1 a =[base pair]/[1 a]). Thus, compound 1 a can be regarded as a programmed responding molecule for DNA, which can semi-quantitatively determine the concentration of DNA over a large concentration range from the standard fluorescence curve of compound 1 a at different wavelengths when bound with DNA. Furthermore, the binding modes of compounds 1 a and 2 a with StDNA were studied by using CD spectroscopy and melting temperature (Tm ) testing. The results showed that compound 1 a interacts with StDNA through multi-interactions including weak intercalation, weak minor groove binding, and inter-dye interactions, whereas compound 2 a bound with DNA through simultaneous intercalation and minor groove binding.
No preview · Article · Sep 2015 · Chemistry - A European Journal
[Show abstract][Hide abstract] ABSTRACT: It is important to detect hydrogen peroxide (H2O2) near mitochondrial DNA (mtDNA) because mtDNA is more prone to oxidative attack than nuclear DNA (nDNA). In this study, a mitochondria-targeted fluorescence probe, pep3-NP1, has been designed and synthesized. The probe contains a DNA-binding peptide, a H2O2 fluorescence reporter and a positively-charged red emissive styryl dye to facilitate accumulation in mitochondria. Due to groove binding of the peptide with DNA, the styryl dye of pep3-NP1 intercalated into the bases of DNA, leading to an increase in red fluorescence intensity (centered at 646 nm) and quantum yield. In this case, pep3-NP1 was a turn-on probe for labeling DNA. Subcellular locations of pep3-NP1 and MitoTracker suggested that pep3-NP1 mostly accumulated in the mitochondria of live cells. Namely, as an intracellular DNA marker, pep3-NP1 bound to mtDNA. In the presence of H2O2, pep3-NP1 emitted green fluorescence (centered at 555 nm). Thus, the ratio of green with red fluorescence of pep3-NP1 was suitable to reflect the change of the H2O2 level near mtDNA in living cells. The detecting limit for H2O2 was estimated at 2.9 and 5.0 μM in vitro and in cultured cells, respectively. The development of pep3-NP1 could help in studies to protect mtDNA from oxidative stress.
No preview · Article · Sep 2015 · Analytical Chemistry
[Show abstract][Hide abstract] ABSTRACT: A sugar functionalized naphthalimide derivative (H1) self-assembles into supramolecular nanotubes
(25 nm pore diameter) by the reaction of 4-N-ethylaminenaphthalimide-N-propinyl and deltagluconolactone in refluxed ethanol. The suspension of the tube assembly in water can directly form
hydrogels when triggered by sonication, without change in morphology or molecular aggregates in the
pH range of 5–8. Modified with aminocarproic acid,H2with more hydrogen bonding sites can form pH
tolerant hydrogels in the widest range of pH values from 1–14 accelerated by sonication. The gelation
mechanism was studied in detail. To the best of our knowledge, this is the first paradigm wherein hydrogels
were constructed from naphthalimide derivatives. Finally, the potential of the hydrogel as a drug delivery
and release system for hydrophilic medicine was explored.
Full-text · Article · Aug 2015 · Journal of Materials Chemistry B
[Show abstract][Hide abstract] ABSTRACT: A highly solid-emissive boron-difluoride dye exhibiting polymorph-dependent and mechanochromic luminescence has been synthesized. Three single crystal X-ray structures of the polymorphic dye molecule, having different fluorescence emissions, are elucidated. Each polymorph displays different stacking orientations among the chromophore moieties and several different intermolecular interactions, which could be related to their different crystal emissions. The molecule displays piezochromic characteristics, with the fluorescence and quantum yield of both the solid powder and two kinds of crystals being reversibly adaptable to mechanical force and heating. The conversion between monomer and π-π stacking-induced aggregate has been proposed as the mechanism behind mechanochromism, according to X-ray diffraction measurements and differential scanning calorimetry analyses.
[Show abstract][Hide abstract] ABSTRACT: Large-scale manipulation of the density (from 2.5 to 1327 mg cm-3) and wettability of carbon-based aerogels have been realized by delicately modulating the gelation, drying and post treatment processes. An unexpected “Janus face” effect of pyrrole was revealed in the fabricating process. Pyrrole acts as a “spacer” at relatively low concentrations (< ca. 5 vol%), resulting in a decrease of the aerogel density; however, “linker” behaviour appears at higher concentrations (> ca. 5 vol%), leading to an increase of the aerogel density. By systematic studies, the oil adsorption capacity of aerogels has been correlated to the aerogel density and surface wettability, which can guide the production of highly efficient sorbents. For example, polydimethylsiloxane modified graphene nanoribbons aerogel with a density of 2.5 mg cm-3 was prepared and showed a remarkable adsorption capacity of up to 302 times for phenixin and 121 times for n-hexane its own weight, much higher than that of most carbonaceous sorbents previously reported. Furthermore, a proof-of-concept aerogel-based floating-type densitometer has also been proposed to expand the potential applications of aerogels.
[Show abstract][Hide abstract] ABSTRACT: A naphthalimide-based fluorescent gelator (N1) containing an alkenyl group has been designed and characterized. This material is able to gelate alcohols via a precipitate-to-gel transformation when triggered with ultrasound for less than 2 min (S-gel). The gelation process in n-propanol was studied by means of absorption, fluorescence and IR spectra, SEM images and XRD patterns. The fluorescence intensity of N1 decreased during the gelation process in a linear relationship with sonication time. The S-gel of N1 could be used to sense aliphatic and aromatic amines by measuring the change in signal output. For example, the addition of propylamine to the S-gel of N1 resulted in a dramatic enhancement of fluorescence intensity, accompanied by a gel-to-sol transition. On the contrary, when the S-gel of N1 was treated with aromatic amines such as aniline, fluorescence was quenched and there was no gel collapse. The sensing mechanisms were studied by 1HNMR, small angle X-ray scattering, SEM and spectroscopic experiments. It is proposed that isomerization of the alkenyl group of N1 from the trans to cis form occurs when the S-gel is treated with propylamine, resulting in a gel-sol transition. However, the aromatic aniline molecules prefer to insert into the gel networks of N1 via hydrogen bonding and charge transfer interactions, maintaining the gel state. As potential applications, testing strips of N1 were prepared to detect aniline.
[Show abstract][Hide abstract] ABSTRACT: In this chapter, supramolecular gel networks containing hydrogen bonding are discussed to demonstrate the importance of complementary hydrogen bonding for the formation of gels and the resulting behavior. The catalogs of the low molecular mass organogelators (LMOGs) for the formation of hydrogen bonding based gels are summarized. Some of the gels show dynamic and reversible properties controlled by the stimuli. Upon stimulation, the gelators supply instant and in situ gelation for organic solvents or water with different modes and outcomes of self-assembly. These supramolecular gels offer a wide range of applications in the fields such as smart and adaptive materials, switches, drug control and release, and tissue engineering.
[Show abstract][Hide abstract] ABSTRACT: A real-time reversible fusion pathway from vesicles to fibres, passing through several types of intermediates such as fused vesicles, short and long tubes, was followed in a cholesterol-based assembly. The mechanism of the structural evolution via gelation process was studied by means of electronic microscopy, small-angle X-ray scattering and powder X-ray diffraction. The fibres of the gel tissue could be switched by sonication and mechanical shaking to tubes and broken fibres, respectively, and reversed by thermal treatment or aging for a certain period via fusion process. The destroyed fibres could match with each other in the healing process, performing self-healing and self-correcting character of the self-assembly. This complete investigation of the reversible vesicle–tube–ribbon transition is of great significance in design and synthesis of new nano/microstructures, especially stimulus-responsive aggregates through a “bottom-up” strategy.
[Show abstract][Hide abstract] ABSTRACT: Photochromism in a diarylethene derivative (1O) can be gated by a host–guest interaction where the thiazole orange groups are bound into the hydrophobic cavity of CB in water. The closed-ring isomer (1C), which cannot be obtained freely in aqueous solution, survives even when the complex is dissociated by displacement from CB with 1-adamantanamine hydrochloride.
No preview · Article · Mar 2015 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: The application of conventional nanostructure carbon-based materials (such as graphene and carbon nanotubes (CNTs)) as catalysts for the oxygen reduction reaction always suffers from inferior conductivity and low surface area because both graphene and CNTs easily aggregate to form networks with many boundaries. Here, to solve those problems, we have rationally developed “carbon nanoleaf” networks for the oxygen reduction reaction of fuel cells. The “carbon nanoleaf” networks are constructed by nitrogen-doped CNTs bridged with graphene nanoribbons (GNRs) aerogels by using CNTs as a single precursor. In these carbon nanoleaves, large amounts of unzipped nanoscale GNRs tightly attach to the intact inner walls of the CNTs and thus allow intrinsically good electrical contact. Self-assembly of the carbon nanoleaves into three-dimensional porous aerogel networks with large surface areas guarantees the ultrafast and sufficient mass transfer in the catalytic process. Moreover, the “carbon nanoleaf” networks restrain the aggregation of adjacent CNTs or GNRs, which is inevitable in other 3D CNTs and/or GNs/GNRs networks, to reduce the possibility of the formation of boundaries. Accordingly, the prepared 3D carbon nanoleaf architectures possesses a large surface area (380~497 m2/ g) and an excellent conductivity (up to 112 S/ m), much higher than other reported 3D carbon-based architectures. The “carbon nanoleaf” networks can thus act as newly developed ORR electrocatalysts with a positive onset potential, ultra-low hydrogen peroxide production and excellent durability that are comparable to or better than those of commercial Pt/C catalysts both in alkaline and acidic solutions.
[Show abstract][Hide abstract] ABSTRACT: Two fluorescent switchable diarylethene derivatives which exhibit high affinity toward amyloid-β aggregates with the increase of fluorescence intensity were reported. Moreover, the probes show excellent photochromic and anti-photobleaching properties both in vitro and in vivo.
No preview · Article · Nov 2014 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: A highly conductive, ultralight, neat and versatile nitrogen-doped GNRs aerogel has been fabricated by a new hydrothermal method for the first time. The newly developed aerogel shows a very promising performance when used as a novel ORR catalyst in both alkaline and acidic solutions.
[Show abstract][Hide abstract] ABSTRACT: Two low-molecular-weight gelators containing 4-ethynyl-1, 8 - naphthalimide groups with a large conjugated structure and different alkyl chain lengths were synthesized and fully characterized. The gelation properties, structural characteristics and fluorescence of the gels were investigated using scanning electron microscopy, X-ray diffraction and spectral studies. The gelators exhibit high fluorescence quantum yields in both the solution and solid state. Interestingly, the wavelength of the fluorescent emission from the reversible sol-gel transition process of the gels exhibited a large red shift of 80 nm in DMF, which has not been previously reported for 1, 8 - naphthalimide derivatives in the literature. The intermolecular π-π stacking between naphthalimide is proposed to be the primary driving force for the gel formation and fluorescent variation based on a temperature-dependent 1H NMR study and theoretical calculations.
[Show abstract][Hide abstract] ABSTRACT: As a marker for oxidative stress and a second messenger in signal transduction, hydrogen peroxide (H2O2) plays an important role in living systems. It is thus critical to monitor the changes in H2O2 in cells and tissues. Here, we developed a highly sensitive and versatile ratiometric H2O2 fluorescent probe (NP1) based on 1, 8-naphthalimide and boric acid ester. In response to H2O2, the ratio of its fluorescent intensities at 555 and 403 nm changed 1020 fold within two hours. The detecting limit of NP1 towards H2O2 is estimated as 0.17 μM. It was capable of imaging endogenous H2O2 generated in live RAW 264.7 macrophages as a cellular inflammation response and especially, it was able to detect H2O2 produced as a signalling molecule in A431 human epidermoid carcinoma cells through stimulation by epidermal growth factor. This probe contains an azide group and thus has the potential to be linked to various molecules via the click reaction. After binding to a Nuclear Localization Signal peptide, the peptide-based combination probe (pep-NP1) was successfully targeted to nuclei and was capable of ratiometrically detecting nuclear H2O2 in living cells. These results indicated that NP1 was a highly sensitive ratiometric H2O2 dye with promising biological applications.
No preview · Article · Sep 2014 · Analytical Chemistry
[Show abstract][Hide abstract] ABSTRACT: Three alkynylplatinum (II) bipyridyl complexes in which two cholesterol groups are combined with a bipyridyl group via alkyl chains and amido bonds were designed and synthesized. The complexes have different lengths of ethylene glycol chains at the para-position of 1-phenylethyne. All three complexes can self-assemble to gel networks in DMSO, while only the morphology of 1a without an ether chain shows well-defined right-handed helical structures with layer packing mode. However, 1c with long ethylene glycol chains forms perfect regular left-handed helical structures in aqueous ethanol solution while the volume percentage of water is less than 5% (v/v). As the ratio of water increases, the chirality changes from a left-handed helix to a right-handed helix and the packing mode alters from the monolayer structure to the hexagonal structure. As the ratio of water further increases to greater than 50% (v/v), the structure of the assembly finally transforms to bilayer vesicles. The process of the morphology transition is traced by circular dichroism spectra, powder X-ray diffraction, SEM and TEM images. The result indicates that a polar solvent (water) acts as a trigger to change the self-assembly of the chiral structures of the complex due to the strong hydrophobic interaction between cholesterol groups and the balance of the hydrophobicity and hydrophilicity of the solvent environment.
[Show abstract][Hide abstract] ABSTRACT: Different luminescent single crystals of 2-(anthracen-9-yl)-4,5-diphenyl-1H-imidazole (ADPI) were obtained through the construction of different stacking modes with the aid of intermolecular interactions. Both the fluorescence and the stacking mode of the crystals can be reversibly tuned by mechanical and thermal forces to render ADPI piezochromic, which represents a unique example of reversibly controlled solid emission. The regulation of π–π stacking between the anthracene planes by mechanical and thermal forces is suggested to be the main driving force for the piezochromic character of ADPI.