Simple Method for Controlling Gold Nanocluster Size in Mesoporous Silica: SBA-11.

Mesoporous silica containing Au nanoclusters has been widely used in various fields owing to its desirable properties and functionality. This work introduces a facile method to control the size of Au nanoclusters within silica hosts. This was achieved by applying a reducing gas at a controlled temperature to obtain a narrow or broad Au cluster size distribution inside the silica host. The Au nanoclusters and their silica hosts were characterized through X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible spectroscopy, N₂ sorption analysis, and X-ray photoelectron spectroscopy. The average size of the Au nanoclusters was 1.3 nm in the narrow-distribution sample. In comparison, the wide-distribution sample exhibited two cluster populations: 1-2 nm inside the pores and 5-30 nm outside the pores. Methylene blue (M.B.) photocatalysis was conducted under direct sunlight to evaluate the catalytic activity of these materials. Sample 1-Au-SBA-11, containing Au clusters averaging 1.3 nm, achieved substantial M.B. degradation within 90 min-half the time required by the 2-Au-SBA-11 sample. Such Au clusters of different size ranges have potential applications across diverse fields.