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Published by Wiley-VCH Verlag
Online ISSN: 1613-6829
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Article
The relaxor-type behavior, electrical polarization buildup, and switching in 0.92Pb(Zn(1/3)Nb(2/3))O(3)-0.08PbTiO(3) nanostructured ceramics with a grain size of approximately 20 nm is reported for the first time. This composition presents the highest-known piezoelectric coefficients, yet phase stability is an issue. Ceramics can only be obtained by the combination of mechanosynthesis and spark-plasma sintering. The results raise the possibility of using nanoscale, perovskite-relaxor-based morphotropic-phase-boundary materials for sensing and actuation in nanoelectromechanical systems.
 
Article
A new kind of multifunctional Co0.85 Se-Fe3 O4 nanocomposites is synthesized by loading Fe3 O4 nanoparticles (NPs) with a size of about 5 nm on the surface of Co0.85 Se nanosheets under hydrothermal conditions without using any surfactant or structure-directing agents. The Co0.85 Se-Fe3 O4 nanocomposite exhibits remarkable catalytic performance for hydrogenation of p-nitrophenol (4-NP) at room temperature and good adsorption behavior for methylene blue trihydrate in water. This nanocomposite also shows a high specific surface area and magnetic separation capability for recyclable utilization. The enhanced performances both in catalysis and adsorption are better than either individual component of Co0.85 Se nanosheets or Fe3 O4 nanoparticles, demonstrating the possibility for designing new multifunctional nanocomposites with improved performances for catalysis, adsorbents, and other applications.
 
Article
Fabrication of a high-temperature deep-ultraviolet photodetector working in the solar-blind spectrum range (190-280 nm) is a challenge due to the degradation in the dark current and photoresponse properties. Herein, β-Ga2 O3 multi-layered nanobelts with (l00) facet-oriented were synthesized, and were demonstrated for the first time to possess excellent mechanical, electrical properties and stability at a high temperature inside a TEM studies. As-fabricated DUV solar-blind photodetectors using (l00) facet-oriented β-Ga2 O3 multi-layered nanobelts demonstrated enhanced photodetective performances, that is, high sensitivity, high signal-to-noise ratio, high spectral selectivity, high speed, and high stability, importantly, at a temperature as high as 433 K, which are comparable to other reported semiconducting nanomaterial photodetectors. In particular, the characteristics of the photoresponsivity of the β-Ga2 O3 nanobelt devices include a high photoexcited current (>21 nA), an ultralow dark current (below the detection limit of 10(-14) A), a fast time response (<0.3 s), a high Rλ (≈851 A/W), and a high EQE (∼4.2 × 10(3) ). The present fabricated facet-oriented β-Ga2 O3 multi-layered nanobelt based devices will find practical applications in photodetectors or optical switches for high-temperature environment.
 
Article
The successful covalent functionalization of quartz and n-type 6H-SiC with organosilanes and benzo[ghi]perylene-1,2-dicarboxylic dye is demonstrated. In particular, wet-chemically processed self-assembled layers of aminopropyltriethoxysilane (APTES) and benzo[ghi]perylene-1,2-dicarboxylic anhydride are investigated. The structural and chemical properties of these layers are studied by contact angle measurements, attenuated total reflection infrared (ATR-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The optical properties are measured by confocal microscopy. The wetting angles observed for the organic layers are α = 68° for the APTES-functionalized surface, while angles of α = 85° and 78° are determined for dye-functionalized quartz and 6H-SiC surfaces, respectively. However, not all amino groups of the APTES-functionalized surfaces react to bind dye molecules. Further dye functionalization is not uniform throughout the surface, showing different island sizes of the dye and including different chemical environments. The quartz surface exhibits a higher packing density of dyes than the 6H-SiC surface. The fluorescence lifetimes of the surface-attached dye show double exponential decays of about 1.4 and 4.2 ns, largely independent of the substrates.
 
Article
For the first time, a facile, one-pot hydrofluoric acid vapor-phase hydrothermal (HF-VPH) method is demonstrated to directly grow single-crystalline anatase TiO(2) nanosheets with 98.2% of exposed {001} faceted surfaces on the Ti substrate via a distinctive two-stage formation mechanism. The first stage produces a new intermediate crystal (orthorhombic HTiOF(3) ) that is transformed into anatase TiO(2) nanosheets during the second stage. The findings reveal that the HF-VPH reaction environment is unique and differs remarkably from that of liquid-phase hydrothermal processes. The uniqueness of the HF-VPH conditions can be readily used to effectively control the nanostructure growth.
 
Article
The properties of InAs quantum dot formation on GaAs(001) using STM within a MBE growth chamber were described. InAs deposited onto an As-terminated GaAs(001) initially forms a two-dimensional (2D) wetting layer (WL). The overall morphology revealed by STMBE is very similar to the results of quenched mode STM. It was shown that it is possible to estimate the additional surface coverage as a function of InAs deposited by comparing the step-terrace-island structures of images in the same location.
 
Article
An efficient homotype Ag3 PO4 /BiVO4 heterojunction photocatalyst is described. Ag3 PO4 nanoparticles preferentially deposit on the highly active BiVO4 (040) facets by means of heterojunction construction together with morphology engineering. The Ag3 PO4 /BiVO4 photocatalyst shows high charge separation efficiency as well as enhanced visible-light response ability and thus possesses superior visible light photocatalytic activity.
 
Article
Visible-light photocatalysis that can directly harvest energy from incoming solar energy offers a desirable way to solve energy and environment issues. On page 3951, J. L. Gong and co-workers report the preparation of an efficient homotype Ag3PO4 /BiVO4 heterojunction photocatalyst via rational structure design. The Ag3PO4 nanoparticles are preferentially deposited on the highlyactive BiVO4 (040) facets via a surfactantmediated mechanism. The Ag3PO4 /BiVO4 photocatalyst shows high charge separation efficiency as well as an enhanced visiblelight response and thus possesses excellent visible light photocatalytic activity. The capability of synthesizing a highly visible light active and stable heterojunction photocatalyst is useful for other solar conversion applications, such as PEC water splitting, dye-sensitized solar cells and photovoltaic devices.
 
Article
The dimension-controlled synthesis of CdS nanocrystals in the strong quantum confinement regime is reported. Zero-, one-, and two-dimensional CdS nanocrystals are selectively synthesized via low-temperature reactions using alkylamines as surface-capping ligands. The shape of the nanocrystals is controlled systematically by using different amines and reaction conditions. The 2D nanoplates have a uniform thickness as low as 1.2 nm. Furthermore, their optical absorption and emission spectra show very narrow peaks indicating extremely uniform thickness. It is demonstrated that 2D nanoplates are generated by 2D assembly of CdS magic-sized clusters formed at the nucleation stage, and subsequent attachment of the clusters. The stability of magic-sized clusters in amine solvent strongly influences the final shapes of the nanocrystals. The thickness of the nanoplates increases in a stepwise manner while retaining their uniformity, similar to the growth behavior of inorganic clusters. The 2D CdS nanoplates are a new type of quantum well with novel nanoscale properties in the strong quantum confinement regime.
 
Article
The synthesis of 1,18-nucleotide-appended bolaamphiphiles (1, 2, 4, and 6) is reported, in which a 3'-phosphorylated guanidine, adenosine, thymidine, or cytidine is connected to each end of an octadecamethylene chain. Single-component self-assemblies and binary self-assemblies with the complementary oligonucleotides dC(20), dT(20), dA(20), and dG(20) are studied by atomic force microscopy, powder X-ray diffraction analysis, temperature-dependent UV absorption, circular dichroism, and attenuated total-reflection Fourier-transform infrared spectroscopy. The single-component self-assembly of 1 forms a two-dimensional sheet, whereas the binary self-assembly 1/dC(20) gives helical nanofibers. Non-helical nanofibers are observed for the single-component self-assemblies of 2 and 4, and helical nanofibers form from the binary self-assembly 2/dT(20). Interestingly, helical nanorod structures are obtained from the binary self-assembly 4/dA(20), and the aligned nanorods form a nematic phase. The single-component and binary self-assemblies from 6 give unilamellar vesicles owing to a lack of stacking interaction between the cytosine moieties.
 
Article
The influence of molecular structure on the mechanical properties of self-assembled 1,3,5-benzenetrisamide nanofibers is investigated. Three compounds with different amide connectivity and different alkyl substituents are compared. All the trisamides form well-defined fibers and exhibit significant differences in diameters of up to one order of magnitude. Using nanomechanical bending experiments, the rigidity of the nanofibers shows a difference of up to three orders of magnitude. Calculation of Young's modulus reveals that these differences are a size effect and that the moduli of all systems are similar and in the lower GPa range. This demonstrates that variation of the molecular structure allows changing of the fibers' morphology, whereas it has a minor influence on their modulus. Consequently, the stiffness of the self-assembled nanofibers can be tuned over a wide range--a crucial property for applications as versatile nano- and micromechanical components.
 
Article
An experiment was conducted to show that very small nanoparticles (NP) can be translocated through the air/blood barrier of the respiratory tract in significant amounts, whereas 18-nm particles are almost trapped in the lungs. Au55 (Ph2PC6H4SO3Na) 12Cl6 and Au NPs were synthesized. Both NPs were activated by neutron activation. These NPs were sealed in quartz tubes either in solid form or in aqueous suspensions and activated at a neutron flux of 10 14 cm-2s-1 at the research reactor of the Hahn-Meitner, Germany. The Np suspension was visually checked for precipitates, and also checked by examination of the UV absorption peak at 523 nm, prior to the administration to rats. The rats were sacrificed by exsanguinations under deep anesthesia through the prepared abdominal aorta 24h after NP administration. Subsequent cytotoxicity investigations with various human tumor cell lines indicated that the cytotoxicity of this compound is unexpectedly high.
 
Article
Gold nanoparticles (AuNPs) are generally considered nontoxic, similar to bulk gold, which is inert and biocompatible. AuNPs of diameter 1.4 nm capped with triphenylphosphine monosulfonate (TPPMS), Au1.4MS, are much more cytotoxic than 15-nm nanoparticles (Au15MS) of similar chemical composition. Here, major cell-death pathways are studied and it is determined that the cytotoxicity is caused by oxidative stress. Indicators of oxidative stress, reactive oxygen species (ROS), mitochondrial potential and integrity, and mitochondrial substrate reduction are all compromised. Genome-wide expression profiling using DNA gene arrays indicates robust upregulation of stress-related genes after 6 and 12 h of incubation with a 2 x IC50 concentration of Au1.4MS but not with Au15MS nanoparticles. The caspase inhibitor Z-VAD-fmk does not rescue the cells, which suggests that necrosis, not apoptosis, is the predominant pathway at this concentration. Pretreatment of the nanoparticles with reducing agents/antioxidants N-acetylcysteine, glutathione, and TPPMS reduces the toxicity of Au1.4MS. AuNPs of similar size but capped with glutathione (Au1.1GSH) likewise do not induce oxidative stress. Besides the size dependency of AuNP toxicity, ligand chemistry is a critical parameter determining the degree of cytotoxicity. AuNP exposure most likely causes oxidative stress that is amplified by mitochondrial damage. Au1.4MS nanoparticle cytotoxicity is associated with oxidative stress, endogenous ROS production, and depletion of the intracellular antioxidant pool.
 
Article
The cover image illustrates how target polymerase chain reaction (PCR) products shield the peroxidase mimicking activity of magnetic nanoparticles (MNPs), leading to a significantly reduced colorimetric signal as compared to the intense colorimetric response by the normal peroxidase activity of MNPs. In the case where PCR products are not formed because a target DNA is absent, MNPs display their normal peroxidase activity generating the red color. On the other hand, peroxidase activity is significantly reduced in the presence of target DNA because the resulting PCR products greatly diminish the accessibility of the colorimetric substrate, o-phenylenediamine. In addition, DNA directly adsorbs onto the surface of MNPs, leading to significant inhibition of the substrate binding to the MNPs, which is required for the peroxidaselike reaction. As a result, the colorimetric substrate is not converted to a red product, retaining its original yellow color. For more information, please read the Communication “Label-Free Colorimetric Detection of Nucleic Acids Based on Target-Induced Shielding Against the Peroxidase-Mimicking Activity of Magnetic Nanoparticles” by H. G. Park and co-workers, beginning on page 1521.
 
Article
Rectangle-and triangle-shaped microscale graphene films are grown on epitaxial Co films deposited on single-crystal MgO substrates with (001) and (111) planes, respectively. A thin film of Co or Ni metal is epitaxially deposited on a MgO substrate by sputtering while heating the substrate. Thermal decomposition of polystyrene over this epitaxial metal film in vacuum gives rectangular or triangular pit structures whose orientation and shape are strongly dependent on the crystallographic orientation of the MgO substrate. Raman mapping measurements indicate preferential formation of few-layer graphene films inside these pits. The rectangular graphene films are transferred onto a SiO 2 /Si substrate while maintaining the original shape and field-effect transistors are fabricated using the transferred films. These findings on the formation of rectangular/triangular graphene give new insights on the formation mechanism of graphene and can be applied for more advanced/controlled graphene growth.
 
Article
The exocytosis of mesoporous silica nanoparticles (MSNs) from mammalian cells is demonstrated for the first time. The differences in the degree of exocytosis of MSNs between healthy and cancer cells are shown to be responsible for the asymmetric transfer of the particles between both cell types. The exocytosis of highly adsorbent magnetic MSNs proves to be useful as a means for harvesting biomolecules from living cells.
 
Gold nanoparticles on carcinoma cell membranes. Two-photon imaging of A431 cells incubated with a) anti-EGFR-coated gold nanoparticles, b) no nanoparticles, and c) PEG-coated gold nanoparticles. Scale bars in a–c represent 30 μm. d) Scanning electron microscopy of a cell membrane targeted by anti-EGFR gold nanoparticles. e) Scanning electron microscopy using the back scattering detector reveals bright reflections indicative of gold particles (marked by arrows). Scale bars in d and e represent 100 nm.
Damaging carcinoma cells using anti-EGFR-coated nanoparticles and resonance femtosecond pulse irradiation. a) Gold-nanoparticle-conjugated cells irradiated by 16 pulses. b) Nonconjugated cells, 16 pulses. c) Conjugated cells irradiated by 4 pulses. d) Nonconjugated cells, 4 pulses. e) Conjugated cells irradiated by 1 pulse. f) Nonconjugated cells, 1 pulse. Multi-nucleated cells margins are marked by dashed white curves in (c). Scale bars represent 50 μm. Red nuclei indicate necrotic cells. Green stain indicates apoptosis. Panels a–d show cells 5 h after irradiation. Panels e,f show cells 23 h after irradiation.
Percentage of cells undergoing necrosis (red bars), fusion (blue bars), and apoptosis (green bars) as a function of the number of irradiating pulses.
Effect of resonance pulse irradiation on necrosis and fusion of specifically targeted lymphoma B cells. a) Fluorescence images of propidium iodide (indicating necrotic cells) distribution superimposed on phase contrast images, 15 h following irradiation by sequences of 1, 4, and 16 pulses. Scale bars represent 70 μm. b) Bar chart summarizing the percentage of necrotic cells in (a). c) Bar chart summarizing the percentage of necrotic and fused lymphoma BJAB cells irradiated by 16 pulses, as a function of increasing pulse fluence. The numbers of necrotic cells and fused cells were evaluated 15 h and 1 h post-irradiation, respectively. GNP refers to gold nanoparticles.
Induction of cell fusion. a) Time sequence of fluorescence images of fusing B (BJAB) cells superimposed on phase contrast images, following irradiation by 5 pulses in the presence of nonspecific gold nanoparticles. Plasma membranes were labeled green. Nuclei were labeled either blue or red. b) Formation of a hybridoma cell. Time sequence of fluorescence images of human B (BJAB) cells (red nuclei) and murine myeloma (NSO) cells (blue nuclei) superimposed on phase contrast images, following irradiation by 5 pulses in the presence of nonspecific gold nanoparticles. Scale bars represent 10 μm.
Article
Specifically targeting and manipulating living cells is a key challenge in biomedicine and in cancer research in particular. Several studies have shown that nanoparticles irradiated by intense lasers are capable of conveying damage to nearby cells for various therapeutic and biological applications. In this work ultrashort laser pulses and gold nanospheres are used for the generation of localized, nanometric disruptions on the membranes of specifically targeted cells. The high structural stability of the nanospheres and the resonance pulse irradiation allow effective means for controlling the induced nanometric effects. The technique is demonstrated by inducing desired death mechanisms in epidermoid carcinoma and Burkitt lymphoma cells, and initiating efficient cell fusion between various cell types. Main advantages of the presented approach include low toxicity, high specificity, and high flexibility in the regulation of cell damage and cell fusion, which would allow it to play an important role in various future clinical and scientific applications.
 
Article
Graphene is an important material with unique electronic properties. Aiming to obtain high quality samples at a large scale, graphene growth on metal surfaces has been widely studied. An important topic in these studies is the atomic scale growth mechanism, which is the precondition for a rational optimization of growth conditions. Theoretical studies have provided useful insights for understanding graphene growth mechanisms, which are reviewed in this article. On the mostly used Cu substrate, graphene growth is found to be more complicated than a simple adsorption-dehydrogenation-growth model. Growth on Ni surface is precipitation dominated. On surfaces with a large lattice mismatch to graphene, epitaxial geometry determin a robust nonlinear growth behavior. Further progresses in understanding graphene growth mechanisms is expected with intense theoretical studies using advanced simulation techniques, which will make a guided design of growth protocols practical.
 
Article
A cooperative therapeutic system combining doxorubicin-induced chemotherapy and chlorine 6-triggered photodynamic therapy (PDT) based on upconverting nanoparticles (UCNPs) is designed on page 1929. In this system, the therapeutic efficacy is manageable since the doxorubicin release is sensitive to the environmental pH values and the PDT efficiency can be fine-tuned by the incident near-infrared irradiation. Importantly, the combinational therapeutic system exhibits a greatly enhanced efficacy relative to the individual cancer therapies.
 
Article
A highly ordered hierarchical periodic structure with a large area is fabricated to support surface plasmon (SP) and surface-enhanced Raman scattering (SERS). This novel metallic submicro-nano structure described on page 1895 exhibits a complex honeycomb-like geometry, which is confirmed in experiments to support both PSPs and LSPs. Multiple modes of SPs are expected to have co-enhanced Raman scattering, heralding a further development of more sophisticated hybrid surface plasmonic nanodevices.
 
Article
The cover illustration shows the use of ligand-patterned surfaces to study the spatio-temporal organization of integrins mediating cell adhesion on cells of the immune system. Micro-contact printing is used to fabricate large chemically confined areas containing the ligand ICAM-1. The dynamic organization of the integrin LFA-1 in living cells is monitored at the single-molecule level using total reflection microscopy. LFA-1 binding to its ligand ICAM-1 promotes the formation of nano- and microclustering on the cell surface that remains largely immobile. In contrast, in the absence of the ligand (free areas in the cover image), LFA-1 diffuses randomly without interaction with the cytoskeleton. This simple experimental approach allows the study of the intricate coupling between spatial organization, lateral diffusion, and conformational states of receptors orchestrating cell adhesion. For more information, please read the Communication “Dynamic Re-organization of Individual Adhesion Nanoclusters in Living Cells by Ligand-Patterned Surfaces” by M. F. Garcia-Parajo et al., beginning on page 1258.
 
Article
Creep in graphene platelet-epoxy nanocomposites is significantly slowed down relative to the unfilled epoxy case. This effect is observed primarily at elevated temperatures and when the material is subjected to higher stress. Carbon nanotube-epoxy composites prepared under similar conditions do not exhibit this phenomenon. Fracture surfaces of graphene platelet-epoxy samples, shown here, indicate that graphene flakes also retard the propagation of cracks, while fiber-like ligaments form during the separation process linking the two crack faces and enhancing the material toughness.
 
Article
A generalized approach to form hybrid organic-inorganic nanocomposite microparticles via the structural reorganization of Pickering emulsion templates is described by V. M. Rotello and co-workers on page 1302. Hydrophilic nanoparticles assembled at the oil/water interface react with a hydrophobic polymer, pulling the particles into the oil core. The combined self-assembly and in-situ covalent conjugation strategy provides a facile method to generate robust porous nanocomposites with excellent stability and high capacity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
 
Article
A method for forming efficient, ultrathin GaN light-emitting diodes (LEDs) and for their assembly onto foreign substances is reported. The LEDs have lateral dimensions ranging from ~1 mm × 1 mm to ~25 μm × 25 μm. Quantitative experimental and theoretical studies show the benefits of small device geometry on thermal management, for both continuous and pulsed-mode operation, the latter of which suggests the potential use of these technologies in bio-integrated contexts.
 
Article
The cover picture shows how single-stranded DNA can be effectively and promptly adsorbed onto functionalized graphene via hydrophobic and π-stacking interactions. Interestingly, the absorbed single-stranded DNA can be effectively protected from enzymatic cleavage, which is encouraging for potential graphene-based biomedical applications involving complex cellular and biofluids samples. Anisotropy, fluorescence, NMR, and CD studies suggest that single-stranded DNA adsorbed onto functionalized graphene forms strong molecular interactions that prevent DNase I from approaching the constrained DNA. Furthermore, constraining a single-stranded DNA probe on graphene improves the specificity of its response to a target sequence. The unique features of DNA–graphene interactions are promising traits that may be exploited to construct DNA–graphene nanobiosensors with facile design, excellent sensitivity, selectivity, and biostability. For more information, please read the Communication “Constraint of DNA on Functionalized Graphene Improves its Biostability and Specificity” by Y. Lin et al., beginning on page 1205.
 
Article
There is a growing interest in oxygen electrode catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), as they play a key role in a wide range of renewable energy technologies such as fuel cells, metal-air batteries, and water splitting. Nevertheless, the development of highly-active bifunctional catalysts at low cost for both ORR and OER still remains a huge challenge. Herein, we report a new N-doped graphene/single-walled carbon nanotube (SWCNT) hybrid (NGSH) material as an efficient noble-metal-free bifunctional electrocatalyst for both ORR and OER. NGSHs were fabricated by in situ doping during chemical vapor deposition growth on layered double hydroxide derived bifunctional catalysts. Our one-step approach not only provides simultaneous growth of graphene and SWCNTs, leading to the formation of three dimensional interconnected network, but also brings the intrinsic dispersion of graphene and carbon nanotubes and the dispersion of N-containing functional groups within a highly conductive scaffold. Thus, the NGSHs possess a large specific surface area of 812.9 m(2) g(-1) and high electrical conductivity of 53.8 S cm(-1) . Despite of relatively low nitrogen content (0.53 at%), the NGSHs demonstrate a high ORR activity, much superior to two constituent components and even comparable to the commercial 20 wt% Pt/C catalysts with much better durability and resistance to crossover effect. The same hybrid material also presents high catalytic activity towards OER, rendering them high-performance cheap catalysts for both ORR and OER. Our result opens up new avenues for energy conversion technologies based on earth-abundant, scalable, noble-metal-free catalysts.
 
Article
New Type of Gold Nanoparticle: A new class of fivefold stellate polyhedral gold nanoparticles (FSPAuNPs) with {110} facets have been synthesized by a seed-mediated growth method without adding surfactant. The size of FSPAuNPs can be simply adjusted from nanoscale to microscale by varying the amount of seeds, which results in a shift of the surface plasmon resonance peak from the visible to the NIR range.
 
Article
A well-ordered two-dimensional (2D) network consisting of two crossed Au silicide nanowire (NW) arrays is self-organized on a Si(110)-16 x 2 surface by the direct-current heating of approximately 1.5 monolayers of Au on the surface at 1100 K. Such a highly regular crossbar nanomesh exhibits both a perfect long-range spatial order and a high integration density over a mesoscopic area, and these two self-ordering crossed arrays of parallel-aligned NWs have distinctly different sizes and conductivities. NWs are fabricated with widths and pitches as small as approximately 2 and approximately 5 nm, respectively. The difference in the conductivities of two crossed-NW arrays opens up the possibility for their utilization in nanodevices of crossbar architecture. Scanning tunneling microscopy/spectroscopy studies show that the 2D self-organization of this perfect Au silicide nanomesh can be achieved through two different directional electromigrations of Au silicide NWs along different orientations of two nonorthogonal 16 x 2 domains, which are driven by the electrical field of direct-current heating. Prospects for this Au silicide nanomesh are also discussed.
 
Article
The atomic resolution of scanning tunneling microscope (STM) images is exploited to identify graphene on metal substrates. The growth of graphene on a Rh(111) substrate is examined under different growth conditions, and diverse surface characteristics and growth mechanisms are discovered. On page 1360, the versatile atomic structures and different stacking geometries of graphene on Rh(111) are described by Z. F. Liu and co-workers.
 
Article
The adsorption and coadsorption of cyanuric acid (CA) and melamine (M) molecules on a Au(111) surface using scanning tunneling microscopy (STM), and the energetics of the homo-and heteromolecular interactions of M and CA, were analyzed. novel stoichiometric phase (CA1M3) was also identified, which formed upon sequential deposition of M followed by CA. Both CA and M were deposited by thermal sublimation from molecular evaporators. Large well-ordered islands were observed in the adsorption structures formed upon deposition of CA or M individually on Au(111). The herring-bone reconstruction of Au(111) did not change upon molecular adsorption and did not affected the self-assembly patterns. The dimer formed from M molecules involved two hydrogen bonds between the NH donor and N acceptor groups, while the heterodimer formed through coupling on one M and one CA molecule involved one NH-N and two NH-O hydrogen bonds.
 
Article
A study was conducted to observe atomically resolved, delocalized two-dimensional charge redistribution associated with Ga nanocluster arrays on the Si(111)-7×7 surface. The study used the topographic scanning tunneling microscopy (STM) images and spatial maps of the differential tunneling conductance to measure the surface local density of states (LDOS) of the surface. The study found that the electronic properties of self-assembled Ga nanocluster array on the Si(111)-7×7 surface can be mapped with atomic-scale spatial resolution. The study found that differential tunneling conductance maps show regions of increased LDOS form an interconnected two-dimensional network of Ga nanoclusters. The study used a UHV STM system and imaging chambers operating at room temperature, and placed the Ga metal in an alumina-coated W wire boat.
 
Article
Self-assembly of organized molecular structures on insulators is technologically very relevant, but in general rather challenging to achieve due to the comparatively weak molecule-substrate interactions. Here the self-assembly of a bimolecular hydrogen-bonded network formed by melamine (M) and cyanuric acid (CA) on ultrathin NaCl films grown on a Au(111) surface is reported. Using scanning tunneling microscopy under ultrahigh-vacuum conditions it is demonstrated that it is possible to exploit strong intermolecular forces in the M-CA system, resulting from complementary triple hydrogen bonds, to grow 2D bimolecular networks on an ultrathin NaCl film that are stable at a relatively high temperature of approximately 160 K and at a coverage below saturation of the first molecular monolayer. These hydrogen-bonded structures on NaCl are identical to the self-assembled structures observed for the M-CA system on Au(111), which indicates that the molecular self-assembly is not significantly affected by the isolating NaCl substrate.
 
Article
Two molecular phases of the DNA base adenine (A) on a Au(111) surface are observed by using STM under ultrahigh-vacuum conditions. One of these phases is reported for the first time. A systematic approach that considers all possible gas-phase two-dimensional arrangements of A molecules connected by double hydrogen bonds with each other and subsequent ab initio DFT calculations are used to characterize and identify the two phases. The influence of the gold surface on the structure of A assemblies is also discussed. DFT is found to predict a smooth corrugation potential of the gold surface that will enable A molecules to move freely across the surface at room temperature. This conclusion remains unchanged if van der Waals interaction between A and gold is also approximately taken into account. DFT calculations of the A pairs on the Au(111) surface show its negligible effect on the hydrogen bonding between the molecules. These results justify the gas-phase analysis of possible assemblies on flat metal surfaces. Nevertheless, the fact that it is not the most stable gas-phase monolayer that is actually observed on the gold surface indicates that the surface still plays a subtle role, which needs to be properly addressed.
 
Article
The unique anisotropic wet-etching mechanism of a (111) silicon wafer facilitates the highly controllable top-down fabrication of silicon nanowires (SiNWs) with conventional microfabrication technology. The fabrication process is compatible with the surface manufacturing technique, which is employed to build a nanowire-based field-effect transistor structure on the fabricated SiNW.
 
Article
A simple method for preparing monolayers with terminal amine functionality is demonstrated. A gas-phase photochemical reaction of 1,3-diaminopropane with a H-terminated Si(111) surface results in the molecules covalently attaching to the surface, primarily through the formation of a Si--N bond. These monolayers are characterized by scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS). The reactivity of the terminal amine is confirmed by exposing the monolayer to benzaldehyde, resulting in the formation of an imine link and the grafting of phenyl rings onto the surface. For short irradiation times, this reaction leads to the formation of isolated amine groups on an otherwise pristine H-terminated surface. STM and HREELS studies of the benzaldehyde reaction on these low-coverage surfaces (less than 0.005 monolayers) indicate that the reaction is restricted to the reactive amine groups, leaving the remainder of the surface unaffected. This simple approach for a sequential coupling reaction is expected to facilitate attachment of more complex molecules (molecular switches, biomolecules) for single-molecule STM studies.
 
Article
A study was conducted to demonstrate the successful nanostructuring of an Au(111) electrode surface with Fe clusters in a 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMI-BF4) ionic liquid, which provides the basis for the studies of new nanoscopic effects of Fe, for investigating the electrochemical properties of nanoscalic Fe. Complex patterns and large-scale ordered arrays of Fe nanoclusters, several monolayers in height, have been fabricated with high precision and high electrochemical stability. The present work provides the basis for surface engineering with Fe nanoclusters by electrochemical means and with a variety of possibilities. The magnetic Fe or Fe oxide nanoclusters may be used as templates for constructing other magnetic nanoparticles. Extending Fe nanostructuring onto surfaces such as Pt and Cu provides systems even more interesting for catalysis and surface science.
 
Article
A systematic investigation of the Au catalyst-assisted growth of epitaxial InAs nanowires (NW) on GaAs substrates was presented. Scanning electron microscopy (SEM) images of InAs NWs with different growth times show no vertical NWs in the sample with 1 min growth of InAs. High resolution transmission electron microscopy (HRTEM) investigations performed at the trace/substrate interface to determine the strain status show many misfit dislocations at the InAs/GaAs interface. The interfacial energy of InAs/Au is found to be higher than that of GaAs/Au, and these energetic considerations result in the Au catalysts retaining contact with GaAs. Vertical NWs initiate at trace intersections where the Au catalysts can not retain interfaces with the GaAs substrate. HRTEM image showing the junction between the base and InAs trace clearly present the epitaxially grown base on the InAs trace.
 
Article
Roberto Otero is acknowledged for stimulating discussion. We acknowledge the financial support from the Danish Ministry for Science, Technology, and Innovation for the iNANO Center, from the Danish Research Councils, and from the Carlsberg Foundation. H.G acknowledges the Marie Curie-Intra-European Fellowship (MEIF-CT-2004-010038). We would also like to acknowledge the computer time on the HPCx supercomputer provided via the Materials Chemistry Consortium. R.E.A.K. is also grateful to the EPSRC for financial support (grant GR/P01427/01).
 
Article
Graphene grown on the same substrate but under different growth conditions may evolve diverse characteristics and disparate growth mechanisms. To explore this issue, graphene is prepared on Rh(111) by both ultrahigh vacuum and ambient-pressure chemical vapor deposition methods and the different growth behaviors, the atomic-scale structures, and the stacking geometry are analysed, mainly by virtue of scanning tunneling microscope. Interestingly, with ultrahigh vacuum chemical vapor deposition growth at 600 °C, a template growth of graphene by the Rh(111) lattice is obtained, reflected with the formation of a uniform graphene moiré. In comparison, with the ambient-pressure chemical vapor deposition at 1000 °C by different quenching processes, monolayer and randomly stacked few-layer polycrystalline graphene is achieved, probably directed by combined surface catalysis and segregation mechanisms. In this case, strong and weak interactions between graphene and Rh substrates are suggested, with the samples prepared under vacuum and ambient-pressure conditions, respectively. This work is expected to contribute greatly to the exploration of interactions between graphene and a substrate, as well as the segregation mechanism of graphene growth on polycrystalline transitional metal substrates.
 
Scheme 1. Preparation of cyclic RGD-PEGylated-AuNP probes with radioactive iodine-125 labels.
a) TEM image of cRGD-PEG-modifi ed AuNPs. Scale bar indicates 50 nm. b) Effi cient 125 I labeling of AuNPs in PBS solution. 125 I was liberated in DTT solution. c,d) Stability test of 125 I-cRP-AuNPs in high salt concentration and acidic and basic solutions. e,f) Stability tests of 125 I-cRPAuNPs and 125 I-mPEG-AuNPs over a 24 h incubation in different pH conditions (e) and different serum (f) conditions.
TEM images of cellular uptake after treated with 125I-cRP-AuNPs: a) U87MG cells and b) MCF-7 cells were incubated with 125I-cRP-AuNPs (300 μg/mL) for 30 min. Arrows indicate cellular uptake of 125I-cRP-AuNPs. Only U87MG cells show strong uptake of 125I-cRP-AuNPs in cells. c) RT-PCR analysis. Expressions of αv and β3 in U87MG and MCF7 cells were determined by RT-PCR. The 319-bp fragments indicate the expression of αv mRNA, and 301-bp fragments indicate the expression of β3 mRNA in U87MG cells. β-actin was used as an internal loading control. d) MTT proliferation assay: U87MG and MCF7 cells were treated with different amounts of 125I-cRP-AuNPs and incubated for 24, 48, and 72 h. The results are presented as percentage absorbance relative to control cells incubated in a probe-free medium. Data are expressed as means±(standard deviations (SD)) of three independent experiments.
Inhibition of 125 I-echistatin (integrin α v β 3 -specifi c) binding to α v β 3 integrin on U87MG and MCF7 cells by cRGD peptide, mPEG-AuNPs, and cRGD-PEG-AuNPs (number of samples, n = 3, mean ± SD), respectively. The IC 50 values for the cRGD peptide and cRGD-PEGAuNPs are 51.34 and 0.337 n M , respectively. Experiment was repeated twice in triplicate.
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XPS studies showing chlorine present at the surface of the treated samples. a) Cl 2p XPS of CdTe before chloride treatment (black line) and after chloride treatment (red line). b) Schematic diagram illustrating the regions of a spherical CQD (green) surrounded by an organic layer (grey) sampled by photoelectrons at normal emission for different X-ray photon energies. c) Variation of Cl/Cd and N/Cd ratios measured in XPS as a function of photoelectron kinetic energy and hence sampling depth. The data are normalized to the photoelectron fl ux and the relevant photoionization cross sections; a further experimentally- determined correction has been applied for kinetic energies (KEs) around the Cd MNN Auger energy. 
Comparison of QY and PL lifetimes before and after chloride treatment. a) PL spectra for untreated CdTe (black line) and treated CdTe (red line) with the same optical density showing a 20 fold increase in PL intensity upon treatment. b) Histogram showing QYs of ten samples before (grey blocks) and after treatment (red blocks). c) PL decay trace showing multi-exponential decay of a sample before treatment (black points) and the mono-exponential decay of the same sample after treatment (red points). d) Histogram showing the PL lifetimes for samples before treatment (grey blocks) and the increased PL lifetimes after treatment (red blocks).
Stability of untreated and treated samples on air-exposure. PL spectra a) before and b) after treatment when exposed to air. c) Decay of QY of untreated (red points) and treated (black points) upon air exposure. d) Transient PL decay traces showing little change upon oxygen exposure for the treated sample (unexposed – green line, 1 hour exposure – blue line) and the formation of rapid non-radiative decay paths upon air exposure for the untreated sample (unexposed – black line, 1 hour exposure – red line). 
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Nanocrystals of CdTe with a zinc blende structure are described by D. J. Binks and co-workers. The surface of each is passivated by a combination of oleylamine ligands and a varying number of chloride ions, shown in the cover image as yellow spheres, that result from the treatment described on page 1548, and which results in near-unity photoluminesence quantum yields. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
 
Top-cited authors
Hua Zhang
  • Shanghai Institute of Technology
Zongyou Yin
  • Australian National University
Xiao Huang
  • Nanjing Tech University, China
Qiyuan He
  • City University of Hong Kong
Catherine Murphy
  • University of Illinois, Urbana-Champaign