Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media

Ammonia borane is widely used in most areas including fuel cell applications.The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles.The glassy carbon electrode was firstly covered with polymeric film electrochemically and then,Au,Ag,and Au–Ag nanoparticles were deposited on the polymeric film,respectively.The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy,transmission electron microscopy,electrochemical impedance spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.It was found that alloyed Au–Ag bimetallic nanoparticles are formed.Electrochemical measurements indicate that the developed electrode modified by Au–Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media.The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane.Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions.

ZnO nanorod decorated by Au-Ag alloy with greatly increased activity for photocatalytic ethylene oxidation

In recent years, the preservation of fruits and vegetables in cold storage has become an issue of increasing concern, ethylene plays a leading role among them. We found ZnO has the effect of degrading gaseous ethylene, however its effect is not particularly satisfactory. Therefore, we used simple photo-deposition procedure and low-temperature calcination method to synthesize Au, Ag, and Au Ag alloy supported ZnO to improve the photocatalytic efficiency. Satisfactorily, after ZnO loaded with sole Au or Ag particles, the efficiency of ethylene degradation was 17.5 and 26.8 times than that of pure ZnO, showing a large increase in photocatalytic activity. However, the photocatalytic stability of Ag/ZnO was very poor, because Ag can be easily photooxidized to Ag2O. Surprisingly, when ZnO was successfully loaded with the Au Ag alloy, not only the photocatalytic activity was further improved to 94.8 times than that of pure ZnO, but also the photocatalytic stability was very good after 10 times of cycles. Characterization results explained that the Au-Ag alloy NPs modified ZnO showed great visible-light absorption because of the surface plasmon resonance(SPR) effect. Meanwhile, the higher photocurrent density showed the effective carrier separation ability in Au Ag/ZnO. Therefore, the cooperative action of plasmonic Au Ag bimetallic alloy NPs and efficient carrier separation capability result in the outstanding photoactivity of ethylene oxidation. At the same time, the formation of the alloy produced a new crystal structure different from Au and Ag, which overcomes the problem of poor stability of Ag/ZnO, and finally obtains Au Ag/ZnO photocatalyst with high activity and high stability. This work proposes a new concept of using metal alloys to remove ethylene in actual production.

Feasibility of Integrating Bimetallic Au-Ag Non-Alloys Nanoparticles Embedded in Reduced Graphene Oxide Photodetector

To coordinate the resonant wavelength of the plasmonic nanoparticles(NPs),the emission band of the reduced graphene oxide(rGO)photodetector at the NIR-region is crucial for the optimal plasmon-enhanced luminescence in the device.In contrast to monometallic NPs,where limits the dimensions and extended resonant wavelength,we integrated an Au-Ag bimetallic NPs(BMNPs)to enable resonance tuning at the longer wavelength at the excitation source of 785 nm.These features showed an increase in radiative recombination rates as well as the quantum yield efficiency of the device.The BMNPs were produced from the dewetting process of 600℃and 500℃,both at 1 min after the deposition thickness layer of Au(8 nm)and Ag(10 nm)on the Si substrate using the electron-beam evaporation process.Our BMNPs-rGO photodetector exhibited the responsivity of 2.25 A·W^(–1),Jones of specific detectivity of 2.45×10^(11)Jones,and external quantum efficiency(EQE)of 356%.The rise time and fall time for the photodetector were 32 ns and 186 ns,respectively.This work provided an essential information to enable the versatile plasmon-enhanced application in 2-dimensional(2D)material optoelectronic devices.

First Principle Calculation on AunAg2 （n = 1 - 4） Clusters

The first-principles method based on density-functional theory is used to investigate the geometries of the lowest-lying isomers of AunAg2 （n = 1 - 4） clusters. Several low-lying isomers are determined, and many of them in electronic configurations with a high spin multiplicity. The stability trend of Ag-doped Aun dusters is compared to that of pure Aun clusters. Our results indicate that the inclusion of two Ag atoms in the clusters lowers the cluster stability, indicating higher stability as the structures grow in size. The bigger energy difference between the Aun and AunAg2 curves as the structures grows in size. This information will be useful to understanding the enhanced catalytic activity and selectivity gained by using silver-doped gold catalyst.

金银双金属纳米壳层结构的SERS活性研究

利用磁控溅射技术在组装整齐的微球表面依次镀上银、金薄膜,获得双金属纳米壳层结构。以对巯基苯胺(p-ATP)为探针分子,研究了该壳层结构在不同激发线下SERS增强差异。测试结果表明,金银双金属纳米壳层结构在780nm激光下具有很好的SERS增强效果,并随着外层金膜厚度的减小而逐渐增强。对各个基底的增强因子进行计算可知,基底的表面等离子体共振(SPR)峰与激发线的匹配程度越好,其增强因子越大。由于金的高稳定性和良好的生物相容性,该基底在SERS生物传感方面具有很大应用潜力。