The Fabrication and SERS Performance of Multi-layer Hollow Au-Ag Alloy Nano Urchins Structure-based SERS Fiber Probe

Novel hollow Au Ag alloy nano urchins were synthesized via Ag seeds growth method,and self-assembly coated on the wall and end-tip of silica fiber for fiber probe fabrication.The nano urchins homogeneously distributed on fiber surface because of fiber silanization.The sizes and tip sharpness of the nano-urchins could be controlled by Ag seeds.The elements distribution analysis indicated there was high Ag content in tip-top for better surface enhance Raman scattering performance.The detectable concentration could be as low as 10-8 M using crystal violet molecules as analyte.Moreover,the fiber probes were stable in air,due to Au in the alloy.This fiber probe could be used for low content single molecular analysis.

Au-Ag alloy nanoparticles with tunable cavity for plasmon-enhanced photocatalytic H2 evolution

Au-Ag alloy nanoparticles with different cavity sizes have great potential for improving photocatalytic performance due to their tunable plasmon effect.In this study,galvanic replacement was combined with co-reduction with the reaction kinetics processes regulated to rapidly synthesize Au-Ag hollow alloy nanoparticles with tunable cavity sizes.The position of the localized surface plasmon resonance(LSPR)peak could be effectively adjusted between 490 nm and 713 nm by decreasing the cavity size of the Au-Ag hollow nanoparticles from 35 nm to 20 nm.The plasmon-enhanced photocatalytic H2 evolution of alloy nanoparticles with different cavity sizes was investigated.Compared with pure P25(TiO2),intact and thin-shelled Au-Ag hollow nanoparticles(HNPs)-supported photocatalyst exhibited an increase in the photocatalytic H2 evolution rate from 0.48μmol h^−1 to 4μmol h^−1 under full-spectrum irradiation.This improved photocatalytic performance was likely due to the plasmon-induced electromagnetic field effect,which caused strong photogenerated charge separation,rather than the generation of hot electrons.

Theoretical research on vacuum separation of Au-Ag alloy

To provide an accurate prediction of the product component dependence of temperature and pressure in vacuum distillation and give convenient and efficient guidance for the designing of the process parameters of industrial production, according to the molecular interaction volume model(MIVM), the separation coefficient(β) and vapor-liquid equilibrium composition of Au-Ag alloy at different temperatures are calculated. Combined with the vapor-liquid equilibrium(VLE) theory, the VLE phase diagrams, including the temperature-composition(T-x) and pressure-composition(p-x) diagrams of Au-Ag alloy in vacuum distillation are plotted. The triple points and condensation temperatures of gold and silver vapors are calculated as well. The results show that the β decreases and the contents of gold in vapor phase increase with the distillation temperature increasing. Low pressures have positive effect on the separation of Ag and Au. The difference between the condensation temperatures of gold and silver is about 450 K in the pressure range of 1-10 Pa.

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.

THE ROLE OF NIOBIUM IN NICKEL-BASED SUPERALLOYS AND CHARACTERIZATION OF PM ALLOY EP741NP

The role of niobium in nickel-based superalloys is reviewed. The importance of niobium as a strengthener is discussed. New developments in nickel-based superalloys are also briefly mentioned, including some results that show improved resistance to sulfidation by niobium. Research results from a current program on the role of niobium in the Russian powder metallurgy alloy EP741NP are presented. Future research plans on the role of niobium in superalloys are also discussed.

金银合金纳米颗粒的可控合成及其光催化性能

以果糖为还原剂和表面活性剂,可控合成了平均粒径小于14.6nm的金银(Au-Ag)合金纳米颗粒.基于一步法,改变合成时间(1~8min),Au-Ag合金纳米颗粒的成分及其表面等离子共振(SPR)波长被连续调控.采用UV-Vis、EDX、ICP、XPS、TEM、HR-TEM和SAED等分析手段对Au-Ag合金纳米颗粒进行表征,发现制备的合金纳米颗粒具有均匀的成分和合金结构.由于Au、Ag两元素的协同作用,Au-Ag合金纳米颗粒在4-硝基苯酚的光催化降解反应中表现出了优异的光催化活性和稳定性.除了改变Au-Ag合金纳米颗粒的添加量,光催化反应的动力学速率常数还可通过改变合金成分来线性调节.基于可控合成,动力学速率常数甚至可通过Au-Ag合金纳米颗粒的合成时间来线性调控.上述控制动力学速率常数的方法可为其他的光催化反应提供参考.

Surface micro/nanostructure evolution of Au-Ag alloy nanoplates： Synthesis, simulation, plasmonic photothermal and surface-enhanced Raman scattering applications

This study reports the controllable surface roughening of Au-Ag alloy nanoplates via the galvanic replacement reaction between single-crystalline triangular Ag nanoplates and HAuC14 in an aqueous medium. With a combination of experimental evidence and finite element method （FEM） simulations, improved electromagnetic field （E-field） enhancement around the surface-roughened Au- Ag nanoplates and tunable light absorption in the near-infrared （NIR） region （-800-1,400 nm） are achieved by the synergistic effects of the localized surface plasmon resonance （LSPR） from the maintained triangular shape, the controllable Au-Ag alloy composition, and the increased surface roughness. The NIR light extinction enables an active photothermal effect as well as a high photothermal conversion efficiency （78.5%）. The well-maintained triangular shape, surface- roughened evolutions of both micro- and nanostructures, and tunable NIR surface plasmon resonance effect enable potential applications of the Au-Ag alloy nanoplates in surface-enhanced Raman spectroscopic detection of biomolecules through 785-nm laser excitation.

Effective fabrication of porous Au-Ag alloy nanorods for in situ Raman monitoring catalytic oxidation and reduction reactions

Porous metal nanostructures exhibit excellent catalytic properties due to their high surface-to-volume ratios and abundant catalytic active sites. However, it is still challenging to control nanopores density and structural features in a facile route and the preparation of porous alloy nanorods for catalytic application has not been well explored. In this work, we demonstrate a synthetic strategy to fabricate highly porous Au–Ag alloy nanorods(P-Au Ag NRs) by critically dealloying Ag atoms from homogeneous solid Au–Ag alloy nanorods(Au Ag NRs). Combining the merits of the tunable plasmonic properties of noble metal nanorods, excellent stabilities of alloys, and superior catalytic activities of porous structures, we use the P-Au Ag NRs as a Raman probe for the in situ monitoring of the catalytic oxidation of 3,3',5,5' tetramethylbenzidine(TMB) and reduction of 4-nitrothiophenol(4-NTP). We also compare their compositiondependent catalytic activities. The results show that P-Au Ag NRs possess superior chemical stability and higher catalytic activity than those of core-shell structures due to synergistic structural and chemical mechanisms. This strategy provides a predictive design approach for the next-generation alloy catalysts with high-performance.

壬基酚聚氧乙烯醚接枝改性顺丁橡胶的研究

采用过氧化二苯甲酰为引发剂，用溶液接枝法使壬基酚聚氧乙烯醚接枝在顺丁橡胶上，通过正交实验确定了橡胶、引发剂、壬其酚聚氧乙烯醚的最佳用量及最佳的反应时间，并通过红外光谱对接枝共聚物进行了表征.

高熵合金纳米电催化剂的合成

相较于单金属和双金属催化剂,高熵合金(HEAs)催化剂因具有多种活性位点而表现出优异的协同效应和催化活性,当其粒径细化至纳米尺度时,纳米尺寸效应与多元活性位点赋予了高熵合金纳米颗粒(np-HEAs)催化剂较低的过电位,近年来在电化学领域逐渐成为研究热点。目前,np-HEAs催化剂的合成方法有脱合金法、热冲击法、低温液相共还原法、机械合金法、激光烧蚀法及溅射沉积法等。综述了近年来np-HEAs催化剂合成的研究现状,总结了提高其催化活性的策略及措施,并展望了np-HEAs催化剂的未来发展方向。

Cu-optimized long-range interaction between Co nanoparticles and Co single atoms:Improved Fenton-like reaction activity

The interplay between multi-atom assembly configurations and single atoms(SAs)has been gaining attention in research.However,the effect of long-term range interactions between SAs and multi-atom assemblies on the orbital filling characteristics has yet to be investigated.In this context,we introduced copper(Cu)doping to strengthen the interaction between cobalt(Co)nanoparticles(NPs)and Co SAs by promoting the spontaneous formation of Co-Cu alloy NPs that tends toward aggregation owing to its negative cohesive energy(-0.06454),instead of forming Cu SAs.The incorporation of Cu within the Co-Cu alloy NPs,compared to the pure Co NPs,significantly expedites the kinetics of peroxymonosulfate(PMS)oxidation processes on Co SAs.Unlike Co NPs,Co-Cu NPs facilitate electron rearrangement in the d orbitals(especially dz^(2)and dxz)near the Fermi level in Co SAs,thereby optimizing the dz^(2)-O(PMS)and dxz-O(SO_(5)^(-))orbital interaction.Eventually,the Co-Cu alloy NPs embedded in nitrogen-doped carbon(CC@CNC)catalysts rapidly eliminated 80.67% of 20 mg L^(-1)carbamazepine(CBZ)within 5 min.This performance significantly surpasses that of catalysts consisting solely of Co NPs in a similar matrix(C@CNC),which achieved a 58.99% reduction in 5 min.The quasi in situ characterization suggested that PMS acts as an electron donor and will transfer electrons to Co SAs,generating^(1)O_(2)for contaminant abatement.This study offers valuable insights into the mechanisms by which composite active sites formed through multi-atom assembly interact at the atomic orbital level to achieve high-efficiency PMS-based advanced oxidation processes at the atomic orbital level.

Immobilizing ultrafine bimetallic PtAg alloy onto uniform MnO_(2) microsphere as a highly active catalyst for CO oxidation

Herein,a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements.Experimental studies reveal that the ultrafine Pt Ag alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO_(2)microsphere,which remarkably enhances the catalytic performances for CO oxidation.Importantly,quasi in-situ X-ray photoelectron spectroscopy(XPS)result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O_(2)molecules,and the oxygen vacancy sites could be replenished and excited by gas-phase O_(2).

Tuning the near room temperature oxidation behavior of highentropy alloy nanoparticles

Understanding the oxidation behavior of high-entropy alloys(HEAs)is essential to their practical applications.Here we conducted in situ environmental transmission electron microscopy(E-TEM)observations of dynamic oxidation processes in CrMnFeCoNi and CrFeCoNiPd nanoparticles(NPs)near room temperature.During the oxidation of CrMnFeCoNi NPs,a favorable oxidation product was MnCr_(2)O_(4)with the spinel structure.The surface nanoislands of MnCr_(2)O_(4)underwent dynamic reconstruction,resulting in the thickened oxide layer with less crystallinity.In CrFeCoNiPd NPs,the reactive element Mn was replaced by the inert element Pd.As a result,a favorable oxide product was CrO_(2)with the rutile structure.CrO_(2)formed on the NP surface and was a result of Cr outward diffusion through the oxide layer.In addition,FeO nanocrystals formed at the oxide/metal interface and were a result of O inward diffusion through the oxide layer.We also performed first principles calculations to provide insights into the energetics and diffusion rates related to oxide formation.These results reveal the non-equilibrium processes of oxidation in HEA NPs that can be strongly influenced by small particle sizes and large surface areas.This work underscores the high tunability of oxidation behavior in nanoscale HEAs by changing their constituent alloying elements.

Enzyme-amplified SERS immunoassay with Ag-Au bimetallic SERS hot spots

Surface-enhanced Raman scattering(SERS)enables rapid detection of single molecules with high specificity.However,quantitative and sensitive SERS analysis has been a challenge due to the lack of reliable SERS-active materials.In this study,we developed a quantitative SERS-based immunoassay using enzyme-guided Ag growth on Raman labeling compound(RLC)-immobilized gold nanoparticle(Au NP)-assembled silica NPs(SiO2@Au-RLC@Ag).The enzyme amplified Ag+reduction as well as Ag growth on the RLC-immobilized Au NP-assembled silica NPs(SiO2@Au-RLC),which resulted in a significant increase in SERS signal.In the presence of target antigens such as immunoglobulinG(IgG)or prostate-specific antigen(PSA),Ab1-Antigen-Ab2 immune complex with alkaline phosphatase triggered an enzyme-catalyzed reaction to convert 2-phospho-L-ascorbic acid(2-phospho-L-AA)to ascorbic acid(AA).As produced AA reduced Ag+to Ag,forming an Ag hot spot on the surface of SiO2@Au-RLC,which enhanced the SERS signal of SiO2@Au-RLC@Ag in a solution with a target antigen concentration.The plasmonic immunoassay for IgG detection showed a high linearity of SERS intensity in the range of 0.6 to 9.0 ng/mL with a detection limit(LOD)of 0.09 ng/mL,while an LOD of 0.006 ng/mL was obtained for PSA.The results indicate that the sensitivity of our novel SERS-based immunoassay is higher than that of conventional enzyme-based colorimetric immunoassays.