Synthesis of Densely Immobilized Gold-Assembled Silica Nanostructures

In this study, dense gold-assembled SiO(2) nanostructure (SiO(2)@Au) was successfully developed using the Au seed-mediated growth. First, SiO(2) (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO(2) surface. Then, Au NPs were grown on the prepared SiO(2)@Au seed by reducing chloroauric acid (HAuCl(4)) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO(2) surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO(2)@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO(2)@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH(3)), and a better peroxidase-like catalysis activity for 5,5′-Tetramethylbenzidine (TMB) and hydrogen peroxide (H(2)O(2)) reaction. The catalytic activity of SiO(2)@Au was two times better than that of HF-treated SiO(2)@Au. When SiO(2)@Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO(2)@Au was also stronger than that of HF-treated SiO(2)@Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.