Ship-in-bottle synthesis of gold nanoparticles in amino-functionalized mesoporous silica thin films

Amino-functionalized mesoporous silica thin films with high content of -NH2 moieties have been directly dip-coated on silicon wafers by co-condensation of tetraethoxysilane and 3-aminopropyltriethoxysilane in the presence of C16H33(OCH2CH2)10OH under acidic condition. X-ray diffraction patterns show that it is a good strategy to remove the surfactant by ethanol extraction rather than calcinations. Using the amino-functionalized mesoporous silica thin films as templates, nanoparticles arrays of gold are formed well within the mesostructures. The isolated gold nanoparticles with size of 2.4-3.9 nm are released by dissolving the silica frameworks with the help of an ethanol solution of HF, showing that the gold nanoparticles have uniform size and spherical appearance. The Ultraviolet-visible spectra show that as the size of gold nanoparticles increase when the dipping time extended, the surface plasmon resonance absorption peak shifts to a longer wavelength.