Manufacture of glass nanoparticles by electrospraying

Glass substrates functionalized by biochemical substances and/or metal thin films have been used in a number of micro-total analysis systems (μTAS) and microelectromechanical systems (MEMS) devices. We propose a dry patterning process for glass nanoparticles (NPs) using an electrospray of the sol of tetraethyl orthosilicate (TEOS) containing hydrochloric acid as a catalyst. We experimentally found that the size of the glass NPs was controlled by the viscosity and feed rate of the TEOS sol, and the applied voltage. In order to verify the usefulness of these glass NPs, we deposited silver NPs on the glass NPs using a modified silver mirror reaction. Silver NPs are reported to enhance the Raman scattering, which is required for ultrasensitive biochemical sensing. Silver NPs on the glass NPs were experimentally found to exhibit greater surface-enhanced Raman scattering than those on a flat glass substrate. Silver NPs can be used in chemical sensors, such as surface-enhanced Raman scattering (SERS) and fluorescence spectroscopy, due to the enhanced electromagnetic field on the surface. Silver NPs are deposited on the glass NPs by the silver mirror reaction with dispersants, for application as ultrasensitive sensors. When silver NPs are formed sterically congested, the enhanced Raman spectrum from the silver NPs on the electrosprayed glass NPs shows an intensity three times that from silver NPs on a flat glass plate substrate. The glass NPs formed by electrospraying are thus proving to yield high performance substrates for chemical sensors.