Surface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable ...challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO
units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions.
Dry reforming of methane (DRM) is an attractive route to utilize CO
as a chemical feedstock with which to convert CH
into valuable syngas and simultaneously mitigate both greenhouse gases. Ni-based ...DRM catalysts are promising due to their high activity and low cost, but suffer from poor stability due to coke formation which has hindered their commercialization. Herein, we report that atomically dispersed Ni single atoms, stabilized by interaction with Ce-doped hydroxyapatite, are highly active and coke-resistant catalytic sites for DRM. Experimental and computational studies reveal that isolated Ni atoms are intrinsically coke-resistant due to their unique ability to only activate the first C-H bond in CH
, thus avoiding methane deep decomposition into carbon. This discovery offers new opportunities to develop large-scale DRM processes using earth abundant catalysts.
Recently, various titanium dioxide (TiO2) nanostructures have received increasing attention in the fields of energy conversion and storage owing to their electrochemical properties. However, these ...particulate nanomaterials exclusively exist in the powder form, which may cause health risks and environmental hazards. Herein we report a novel, highly elastic bulk form of TiO2 for safe use and easy recycling. Specifically, TiO2 nanofibrous aerogels (NAs) consisting of resiliently bonded, flexible TiO2 nanofibers are constructed, which have an ultralow bulk density, ultrahigh porosity, and excellent elasticity. To promote charge transfer, they are subjected to lithium reduction to generate abundant oxygen vacancies, which can modulate the electronic structure of TiO2, resulting in a conductivity up to 38.2 mS cm−1. As a proof‐of‐concept demonstration, the conductive and elastic TiO2 NAs serve as a new type of self‐supported electrocatalyst for ambient nitrogen fixation, achieving an ammonia yield of 4.19×10−10 mol s−1 cm−2 and a Faradaic efficiency of 20.3 %. The origin of the electrocatalytic activity is revealed by DFT calculations.
Conductive and elastic TiO2 nanofibrous aerogels (NAs), with a hierarchically ordered, cellular architecture consisting of resiliently bonded nanofibers, can be prepared. As a proof‐of‐concept demonstration, the TiO2 NAs serve as a new type of self‐supported electrocatalysts with high activity and durability for ambient nitrogen fixation.
Homogeneous catalysts generally possess superior catalytic performance compared to heterogeneous catalysts. However, the issue of catalyst separation and recycling severely limits their use in ...practical applications. Single‐atom catalysts have the advantages of both homogeneous catalysts, such as “isolated sites”, and heterogeneous catalysts, such as stability and reusability, and thus would be a promising alternative to traditional homogeneous catalysts. In the hydroformylation of olefins, single‐atom Rh catalysts supported on ZnO nanowires demonstrate similar efficiency (TON≈40000) compared to that of homogeneous Wilkinson's catalyst (TON≈19000). HAADF‐STEM and infrared CO chemisorption experiments identified isolated Rh atoms on the support. XPS and XANES spectra indicate that the electronic state of Rh is almost metallic. The catalysts are about one or two orders of magnitude more active than most reported heterogeneous catalysts and can be reused four times without an obvious decline in activity.
Rhodium single‐atom catalysts supported on ZnO nanowires display olefin hydroformylation efficiency comparable to that of homogeneous Wilkinson's catalyst.
Organic heterostructures (OHSs) integrating the intrinsic heterostructure characters as well as the organic semiconductor properties have attracted intensive attention in material chemistry. However, ...the precise bottom-up synthesis of OHSs is still challenging owing to the general occurrence of homogeneous-nucleation and the difficult manipulation of noncovalent interactions. Herein, we present the rational synthesis of the longitudinally/horizontally-epitaxial growth of one-dimensional OHSs including triblock and core/shell nanowires with quantitatively-manipulated microstructure via a hierarchical self-assembly method by regulating the noncovalent interactions: hydrogen bond (-15.66 kcal mol
) > halogen bond (-4.90 kcal mol
) > π-π interaction (-0.09 kcal mol
). In the facet-selective epitaxial growth strategy, the lattice-matching and the surface-interface energy balance respectively facilitate the realization of triblock and core/shell heterostructures. This hierarchical self-assembly approach opens up avenues to the fine synthesis of OHSs. We foresee application possibilities in integrated optoelectronics, such as the nanoscale multiple input/out optical logic gate with high-fidelity signal.
White‐light‐emissive organic micro/nanostructures hold exotic potential applications in full‐color displays, on‐chip wavelength‐division multiplexing, and backlights of portable display devices, but ...are rarely realized in organic core/shell heterostructures. Herein, through regulating the noncovalent interactions between organic semiconductor molecules, a hierarchical self‐assembly approach of horizontal epitaxial‐growth is demonstrated for the fine synthesis of organic core/mono‐shell microwires with multicolor emission (red–green, red–blue, and green–blue) and especially organic core/double‐shell microwires with radial red–green–blue (RGB) emission, whose components are dibenzog,pchrysene (DgpC)‐based charge‐transfer (CT) complexes. In fact, the desired lattice mismatching (≈2%) and the excellent structure compatibility of these CT complexes facilitate the epitaxial‐growth process for the facile synthesis of organic core/shell microwires. With the RGB‐emissive substructures, these core/double‐shell organic microwires are microscale white‐light sources (CIE 0.34, 0.36). Besides, the white‐emissive core/double‐shell microwires demonstrate the fascinating full‐spectrum light transportation from 400 to 700 nm. This work indeed opens up a novel avenue for the accurate construction of organic core/shell heterostructures, which provides an attractive platform for the organic integrated optoelectronics.
Through regulating the noncovalent interactions between organic semiconductor molecules (|ECT, DgpC‐TCNB = −18.35 kcal mol−1| > |ECT, DgpC‐TFP = −13.45 kcal mol−1| > |Eπ–π, DgpC = −6.81 kcal mol−1|), a hierarchical self‐assembly approach of horizontal epitaxial‐growth is demonstrated for the precise synthesis of organic core/double‐shell microwires with radial red–green–blue (RGB) substructures for miniaturized white‐light sources (CIE 0.34, 0.36).
Anisotropic organic molecular construction and packing are crucial for the optoelectronic properties of organic crystals. Two‐dimensional (2D) organic crystals with regular morphology and good photon ...confinement are potentially suitable for a chip‐scale planar photonics system. Herein, through the bottom‐up process, 2D halogen‐bonded DPEpe‐F4DIB cocrystals were fabricated that exhibit an asymmetric optical waveguide with the optical‐loss coefficients of RBackward=0.0346 dB μm−1 and RForward=0.0894 dB μm−1 along the 010 crystal direction, which can be attributed to the unidirectional total internal reflection caused by the anisotropic molecular packing mode. Based on this crystal direction‐oriented asymmetric photon transport, these as‐prepared 2D cocrystals have been demonstrated as a microscale optical logic gate with multiple input/out channels, which will offer potential applications as the 2D optical component for the integrated organic photonics.
Guiding light: Through a bottom‐up process, 2D halogen‐bonded DPEpe‐F4DIB cocrystals were fabricated that act as an asymmetric optical waveguide with the optical‐loss coefficients of RBackward=0.0346 dB μm−1 and RForward=0.0894 dB μm−1 along the 010 crystal direction. This is further demonstrated in a microscale optical logic gate with multiple input/out channels.
With the development of new instruments and methodologies, the highly dynamic behaviors of nanoparticle at the liquid-solid interface have been studied. However, the dynamic nature of the ...electrochemical behavior of individual nanoparticles on the electrode interface is still poorly understood. Here, we generalize scaling relations to predict nanoparticle-electrode interactions by examining the adsorption energy of nanoparticles at an ultramicroelectrode interface. Based on the theoretical predictions, we investigate the interaction-modulated dynamic electrochemical behaviors for the oxidation of individual Ag nanoparticles. Typically, significantly distinct current traces are observed owing to the adsorption-mediated motion of Ag nanoparticles. Inspired by restraining the stochastic paths of particles in the vicinity of the electrode interface to produce surface-confined current traces, we successfully realize high-resolution size measurements of Ag nanoparticles in mixed-sample systems. This work offers a better understanding of dynamic interactions of nanoparticles at the electrochemical interface and displays highly valuable applications of single-entity electrochemistry.
Summarizing the status of drugs in the market and examining the trend of drug research and development is important in drug discovery. In this study, we compared the drug targets and the market sales ...of the new molecular entities approved by the U.S. Food and Drug Administration from January 2000 to December 2009. Two networks, namely, the target-target and drug-drug networks, have been set up using the network analysis tools. The multi-target drugs have much more potential, as shown by the network visualization and the market trends. We discussed the possible reasons and proposed the rational strategies for drug research and development in the future.
•Automatic diagnosis of skin cancer regions in medical images.•A unified deep learning framework for skin cancer detection.•A new meta-heuristic optimized convolutional neural networks (CNN/IWOA).
...Early detection of skin cancer is very important and can prevent some skin cancers, such as focal cell carcinoma and melanoma. Although there are several reasons that have bad impacts on the detection precision. Recently, the utilization of image processing and machine vision in medical applications is increasing. In this paper, a new image processing based method has been proposed for the early detection of skin cancer. The method utilizes an optimal Convolutional neural network (CNN) for this purpose. In this paper, improved whale optimization algorithm is utilized for optimizing the CNN. For evaluation of the proposed method, it is compared with some different methods on two different datasets. Simulation results show that the proposed method has superiority toward the other compared methods.
PDF
