Chemical and photochemical formation of gold nanoparticles supported on viologen-functionalized SBA-15

Viologen-functionalized SBA-15 was successfully prepared and used for the chemical and photochemical formation of supported gold nanoparticles. The anion exchange properties of viologen moieties were explored and AuCl4− anion were adsorbed and retained by electrostatic interactions inside the substrate porous structure. Subsequently, the formation of gold nanoparticles was accomplished by two different routes: (i) by chemical reduction, using NaBH4 as reducing agent; (ii) photochemical reduction, utilizing the redox properties of the grafted viologen groups under UV irradiation. Diffuse reflectance measurements and TEM images revealed that the chemical reduction generated gold nanospheres dispersed inside the host mesopores, while photochemical reduction produced gold nanorods.