The advances of DIOS-MS since its earliest work promise the reliable measurement of low-molecular weight species in tandem with, and possibly without,
MALDI-MS. Additionally, the well-established integration of devices upon silicon
chips offer the ability to fashion samples capable of supporting multiple analyses
in series or parallel, confining all characterizations of biological or chemical species to a lone substrate. It is clear that surface termination and bound functionalities are important not only for analysis but also for recycling the porous silicon
chip for multiple uses.
Fig. 16.21. (A) Contact angle goniometry of
porous silicon substrates stored in dry air and
methanol for 1 day and 6 days. Solvents used
for goniometry range from 0–75% methanol in
ultrapure water (x-axis). On average, silicon
substrates stored for longer periods exhibited
lower contact angles, representative for
hydrophilic surfaces. (B) DIOS-MS spectra of a
three-peptide mixture (same as that analyzed
in Figure 16.20) from porous silicon substrates
stored for 6 days. (Reprinted with permission
from [135]. Copyright 2001 American Chemical
Society. J. V. Sweedler is also thanked for
permission to reprint this figure.)
16.4 Chemical Applications Based on Porous Silicon 545