Toward a Reusable Surface-Enhanced Raman Spectroscopy (SERS) Substrate by Soft-Landing Ion Mobility

Soft-landing ion mobility has been applied to the development of a reusable surface-enhanced Raman spectroscopic substrate. Sections of silicon wafers were cleaved and modified with 3-(mercaptopropyl) triethoxysilane. After modification, gold was deposited using a soft-landing ion mobility system at thermal kinetic energies. It was found that 30 min of deposition provided the optimal feature size for surface-enhanced Raman scattering, and thus deposition was completed in a pressure-dependent fashion. After gold deposition, caffeine was deposited from the solution phase and checked for Raman activity. The Raman spectroscopic signature for caffeine increased as an inverse function of pressure pertaining to surface coverage of captured Au particles. After Raman spectroscopic confirmation of caffeine, the 1 Torr surface was ultrasonically cleaned in deionized water and respotted with sodium bicarbonate solution. There was no interference on the sodium bicarbonate solution from residual caffeine on the surface.