Synthesis of dendritic silver nanostructures and their application in hydrogen peroxide electroreduction

Well-defined silver (Ag) dendritic nanostructures were successfully synthesized by electrodeposition without the use of any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the as-prepared Ag nanomaterials. These dendrites are aggregates of Ag nanoparticles, which are highly crystalline in nature. The concentration of AgNO₃ affects the shape of the nanoparticles. In addition, the electrochemical properties of the Ag dendrite-modified glassy carbon electrode (Ag/GC) were characterized by cyclic voltammetry and chronoamperometry. Results indicated that the as-obtained Ag dendrites exhibited favorable electroreduction activity towards oxygen (O₂) and hydrogen peroxide (H₂O₂). When used as a sensor, the Ag/GC electrode exhibited a wide linear range of 0.005–12 mM H₂O₂, with a remarkable sensitivity of 7.39 μA/mM, a detection limit of 0.5 μM, estimated at a signal-to-noise ratio of 3, and a rapid response time (within 5 s). Moreover, the electrode showed good reproducibility, anti-interferant ability and long-term stability.     

Plasmonic-excitonic multi-hybrid glass-based nanocomposites incorporating Ag plus core-shell CdSe/CdS and alloyed CdSxSe1−x nanoparticles

Successful fabrication of glass-based hybrid nanocomposites (GHNCs) incorporating Ag, core-shell CdSe/CdS and CdS_xSe_1?x nanoparticles (NPs) is herein reported. Both metallic (Ag) and semiconductor (CdSe/CdS) NPs were pre-synthesized, suspended in colloids and added into the sol-gel reaction medium which was used to fabricate the GHNCs. During fabrication of the nanocomposites a fraction (20–60%) of core-shell CdSe/CdS NPs was alloyed into CdS_xSe_1?x (0.20 < x < 0.35) NPs without changing morphology. Modulation of in situ alloying is possible via the relative content of organics added into the sol-gel protocol. Within colloids Ag (core-shell CdSe/CdS) NPs presented average diameter and polydispersity index of 49.5 nm (4.2 nm) and 0.41 (0.21), respectively. On the other hand, the Ag (core-shell CdSe/CdS) NPs’ average diameter and polydispersity index assessed from the GHNCs were respectively 51.5 nm (4.1 nm) and 0.43 (0.25), revealing negligible aggregation of the nanophases within the glass template. The new GHNCs herein introduced presented two independent excitonic transitions associated to homogenously dispersed semiconductor NPs, peaking around 420 nm (core-shell CdSe/CdS) and 650 nm (CdS_xSe_1?x) and matching the plasmonic resonance (Ag NPs) in the 400–500 nm range. We envisage that the new GHNCs represent very promising candidates for superior light manipulation while illuminated with multiple laser beams in quantum interference-based devices.     

铬银共掺杂改性纳米TiO2光催化剂及其光催化性能研究

以钛酸四丁酯为原料,利用溶胶凝胶法制备了Cr/Ag共掺杂的TiO2纳米材料.采用XRD、SEM、EDS等测试分析技术对掺杂纳米TiO2粉体进行了表征;以甲基橙为降解物,在太阳光照射条件下研究了掺杂对光催化活性的影响.研究结果表明:掺杂后的纳米TiO2的光催化性能明显提高,优于纯TiO2.当共掺杂的比例为Cr 1.0%/Ag 0.5%时,样品的效果最佳,对甲基橙的3h降解率达到97.63%.     

Ag担载介孔Bi2WO6的制备及其太阳光催化性能

采用硬模板法及液相沉淀法制备了介孔Bi2WO6(m-Bi2WO6)光催化剂,通过光还原沉积贵金属的方法制备了银担载的m-Bi2WO6复合纳米粒子(Ag/m-Bi2WO6),并利用氮气吸附脱附、XRD、XPS、DRS等测试技术对样品进行了表征。以RhB染料为目标降解物,考察了样品的光催化活性。结果表明,介孔结构能够提高Bi2WO6光催化剂的光催化性能;担载金属银,使得m-Bi2WO6催化剂的光催化性能得到了提高。     

Synthesis of Chelating Resin PETU and Its Adsorption to Ag(I)

A novel chelating resin (PETU) with thiourea groups in its main chain was synthesized by the reaction of O,O'-butane-1,4-diyl dicarbonisothiocyanatidate and triethylene tetraamine. The adsorption of Ag(I) on PETU was investigated by batch tests. The results showed that adsorption data fitted Boyd's diffusion equation of liquid film and the adsorption was controlled by liquid film diffusion. Under the temperatures between 15～60 ℃, the adsorption capacity decreased with the increase of temperature, and increased with the increase of initial concentration of Ag(I). The experimental data fitted Langmuir and Freundlich equations, and the correlation coefficients for Langmuir equation were between 0.9965～0.9998, and those for Freundlich equation were between 0.8211～0.9810, and increased with the adsorption temperature. △H, △G and △S calculated by thermodynamic formulae were all negative, which meant that the adsorption process was exothermic and spontaneous, and the entropy decreased during the process. XPS results showed that N, S and O atoms were the electron donors to coordinate with Ag.     

有机氯对乙烯环氧化反应性能的影响

考察有机氯作为抑制剂对乙烯环氧化性能的影响,并且对抑制剂作用机理进行研究。结果表明,氯元素含量为0.25×10^(-6)时的作用效果最佳。相同氯含量条件下,四氯乙烯作为抑制剂的作用效果优于氯乙烷和1,2-二氯乙烷。在乙烯环氧化制环氧乙烷反应条件下,1,2-二氯乙烷的分解为可逆反应,氯乙烷和四氯乙烯的分解为不可逆反应。     

Surface chemistry of SnO2 nanowires on Ag-catalyst-covered Si substrate studied using XPS and TDS methods

In this paper we investigate the surface chemistry, including surface contaminations, of SnO₂ nanowires deposited on Ag-covered Si substrate by vapor phase deposition (VPD), thanks to x-ray photoelectron spectroscopy (XPS) in combination with thermal desorption spectroscopy (TDS). Air-exposed SnO₂ nanowires are slightly non-stoichiometric, and a huge amount of C contaminations is observed at their surface. After the thermal physical desorption (TPD) process, SnO₂ nanowires become almost stoichiometric without any surface C contaminations. This is probably related to the fact that C contaminations, as well as residual gases from air, are weakly bounded to the crystalline SnO₂ nanowires and can be easily removed from their surface. The obtained results gave us insight on the interpretation of the aging effect of SnO₂ nanowires that is of great importance for their potential application in the development of novel chemical nanosensor devices.     

Microwave-assisted green synthesis of Ag/reduced graphene oxide nanocomposite as a surface-enhanced Raman scattering substrate with high uniformity

A nanocomposite of silver nanoparticles/reduced graphene oxide (Ag/rGO) has been fabricated as a surface-enhanced Raman scattering (SERS) substrate owing to the large surface area and two-dimensional nanosheet structure of rGO. A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles and the reduction of graphene oxide simultaneously with L-arginine as the reducing agent. By increasing the cycle number of microwave irradiation from 1 and 4 to 8, the mean diameters of Ag nanoparticles deposited on the surface of rGO increased from 10.3 ± 4.6 and 21.4 ± 10.5 to 41.1 ± 12.6 nm. The SERS performance of Ag/rGO nanocomposite was examined using the common Raman reporter molecule 4-aminothiophenol (4-ATP). It was found that the Raman intensity of 4-ATP could be significantly enhanced by increasing the size and content of silver nanoparticles deposited on rGO. Although the Raman intensities of D-band and G-band of rGO were also enhanced simultaneously by the deposited Ag nanoparticles which limited the further improvement of SERS detection sensitivity, the detectable concentration of 4-ATP with Ag/rGO nanocomposite as the SERS substrate still could be lowered to be 10⁻¹⁰ M and the enhancement factor could be increased to 1.27 × 10¹⁰. Furthermore, it was also achievable to lower the relative standard deviation (RSD) values of the Raman intensities to below 5%. This revealed that the Ag/rGO nanocomposite obtained in this work could be used as a SERS substrate with high sensitivity and homogeneity.     

Potential instabilities of lead silver alloy anodes in acidic sulfate electrolytes

The kinetic behaviour of lead and lead–silver anodes, polarized under galvanostatic conditions in a H2SO4ZnSO4MnSO4 electrolyte, has been studied. Whereas the potential of the lead anode stabilizes during electrolysis, the potential of the lead–silver alloy anode oscillates between two limits after an induction time. Both silver on the anode surface and manganese in the electrolyte are required for the potential oscillations to appear. With increasing time the potential oscillations change in shape and period. From impedance data obtained earlier, at the beginning of, and during the potential oscillations, it is shown that the potential instabilities originate from electrode coverage by a silver salt adsorbate.     

光辅助原位清洁制备Ag/AgCl纳米颗粒

以Ag NO3和反渗透水(RO)中的Cl–为原料,在波长为395 nm的紫外光源(20 W)下原位合成Ag/Ag Cl纳米颗粒。通过透射电子显微镜(TEM)、高分辨率的透射电镜(HRTEM)和动态光散射(DLS)表征了样品的形貌和尺寸分布,用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见吸收光谱(UV-Vis)和荧光光谱分别对复合材料的晶体结构和元素价态以及光催化性能进行了测试。结果表明:Ag/AgCl复合材料是球形颗粒,平均粒径为100 nm。AgNO₃溶液形成复合纳米颗粒的过程能有效降解罗丹明6G,银离子溶液在光照3 min时罗丹明6G的降解率和猝灭率分别可达96.5%和95%。