“先核后壳”和“先壳后核”的简便途径制备M@SiO2(M=Ag,Au,Pt)纳米核壳结构及其催化活性

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 nmm, 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 ℃空气焙烧后仍能保持高的CO氧化性能(T₁₀₀=235 ℃). 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 nmm, 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.

Synthesis and catalytic activity of M@SiO2 (M=Ag,Au, and Pt) nanostructures via “core to shell” and “shell then core” approaches

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 ℃) even after being subjected to calcination in air at 550 ℃. In the latter approach, the core size could be controlled at < 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 allowed the SiO₂ shell and metal core properties to be modified in these approaches, which is beneficial for application.