Development of near infrared responsive material based on silica encapsulated gold nanoparticles

Abstract

In this research, the silica encapsulated gold nanoparticles with optical resonance located in 700-850 nm spectral region were synthesized by combining gold core and the silica shell. The synthesized composite particles can be potentially used in biological fields, due to the biocompatibility of gold, silica and biopolymers. Nano-gold, which can act a raw material of composite particles, was fabricated by stand citrate reduction method. Then, the polyvinyl pyrrolidone (PVP) and (3-mercaptopropyl)trimethoxysilane (MPTMS) are added to deposit silica shell and control particle size. Finally, a complete silica nanoshell was formed on the gold surface by the one-step method, without a repeated coating process. The controllable absorption wavelength of nano-composite particles can be easily controlled by the concentration ratio of PVP and MPTMS. Transmission electron microscopy (TEM) images and optical absorption spectra clearly showed that silica was successfully deposited onto the gold surface by this novel method. As the decreasing aggregation of gold core by adding PVP, the optical plasmon peaks became blue-shifted, but the optical plasmon resonance became red-shifted and the absorption spectra were functions of addition ratios by MPTMS. We expect to extend these functional nanoparticles for real sample applications in the near future. © 2009 IOP Publishing Ltd.