Influence of buried oxide layers of nanostructured SOI surfaces on matrix-free LDI-MS performances

In this paper, we report on the nanostructuration of the silicon crystalline top layer of different "home-made" SOI substrates presenting various buried oxide (BOx) layer thicknesses. The nanostructuration was achieved via a one-step metal assisted chemical etching (MACE) procedure. The etched N-SOI substrate surfaces were then characterized by AFM, SEM and photoluminescence. To investigate their laser desorption/ionization mass spectrometry performances, the different surfaces have been assessed towards peptide mixtures. We have shown that the matrix-free LDI process occurred from surface heating after laser irradiation and was fostered by thermal confinement in the thin nanostructured Si surface layer. This thermal confinement was enhanced with the increase of the buried oxide layer thickness until an optimal thickness of 200 nm for which the best results in terms of signal intensities, peptide discrimination and spot to spot and surface to surface variations were found.