“先核后壳”和“先壳后核”的简便途径制备M@SiO_2(M=Ag,Au,Pt)纳米核壳结构及其催化活性

Synthesis and catalytic activity of M@SiO_2 (M = Ag, Au, and Pt) nanostructures via “core to shell” and “shell then core” approaches

采用简便的"先核后壳"和"先壳后核"途径制备了M@SiO2(M=Ag,Au,Pt)核壳结构.采用"先核后壳"途径时,金属内核可以控制在6–9 nm,粒径分布均匀,SiO2壳层织构可调.该途径制备过程简便,无需高速离心分离,可有效节约制备成本.由该途径制得的Au@mSiO2中纳米Au的热稳定性高,经550 C空气焙烧后仍能保持高的CO氧化性能(T100=235 C).由"先壳后核"途径制得的核壳结构内核金属粒子也可以控制在<10 nm,粒径分布均匀,且SiO2壳层孔隙率可以预调,即使在液相中也可有效消除对硝基苯酚反应物分子的扩散限制,并于室温下将其还原为对氨基苯酚.两种途径所得的核壳结构均呈高单分散态.使用含有不同有机官能团的硅源可对介孔SiO2壳层进行进一步改性,拓展应用领域,因而具有很好的潜在应用前景.

M@SiO2 (M = Ag,Au,and Pt) core-shell nanostructures were prepared by the 'core to shell' and 'shell then core' approaches.In the former,the metal core size could be controlled in the 6–9 nm range with a narrow size distribution,and the shell porosity was tunable.The preparation was straightforward and efficient, without requiring specialized high-speed centrifugation. Au@SiO2 containing mesoporous SiO2 shells(Au@meso-SiO2) exhibited good thermal stability and high CO oxidation activity(T100 = 235 °C) even after being subjected to calcination in air at 550 °C.In the latter approach,the core size could be controlled at &lt; 10 nm with a narrow size distribution,and the shell porosity was tunable to a fine degree.4-Nitrophenol was readily reduced at room temperature in the presence of Au@meso-SiO2 obtained through the 'shell then core' approach.The SiO2 shell mesoporosity minimized the diffusion limitation of 4-nitrophenol.The core-shell structures from both approaches were uniformly dispersed.Employing Si sources with differing functionality al- lowed the SiO2 shell and metal core properties to be modified in these approaches,which is benefi- cial for application.