Porous silicon as a versatile platform for laser desorption/ionization mass spectrometry

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) is a novel method for generating and analyzing gas-phase ions that employs direct laser vaporization. The structure and physicochemical properties of the porous silicon surfaces are crucial to DIGS-MS performance and are controlled by the selection of silicon and the electrochemical etching conditions. Porous silicon generation and DIGS signals were examined as a function of silicon crystal orientation, resistivity, etching solution, etching current density, etching time, and irradiation. Pre-and postetching conditions were also examined for their effect on DIGS signal as were chemical modifications to examine stability with respect to surface oxidation, Pore size and other physical characteristics were examined by scanning electron microscopy and Fourier transform infrared spectroscopy, and correlated with DIGS-MS signal. Porous silicon surfaces optimized for DIGS response were examined for their applicability to quantitative analysis, organic reaction monitoring, post-source decay mass spectrometry, and chromatography.