A Solvent Free Approach for the Preparation of Silver Modified Mesoporous Silica for Iodine Entrapment

Abstract

A green solvent-free approach, using a heating/grinding method, was employed to produce grey colored Ag functionalized mesoporous silica (here SBA-15). This material consisted of Ag0 nanoparticles with diameters of around 1.5 ± 0.45 nm inside the pores of SBA-15, and aggregated silver nanoparticles on the outside of the SiO2. Indeed due to a lack of a strong stabilizer the degree of particle aggregation is high. This easy to handle powder was then used to extract molecular Iodine. The resulting yellow powder was examined by Ultraviolet–Visible (UV–Vis) and Fourier-transform Infrared spectroscopies, X-rays diffraction, thermogravimetric analysis (TGA) and scanning and transmission electron microscopy (SEM/TEM). It was found that the aggregates of individual Ag nanoparticles disaggregate as AgI quantum dots are formed, explaining the high I2 capacity exhibited by these materials, almost 1:1 Ag to I. Despite numerous washing steps with a range of solvents (ranging from cyclohexane to water) no leaching was observed. Finally, TGA demonstrated an increased melting point for the AgI dots indicating a degree of protection from the silica support.