Optimized recipe for sol-gel-based SERS substrates

The aim of this study was to develop further surface-enhanced Raman scatter ing (SERS) substrates appropriate for the in situ. environmental determinat ion of chemicals in sea-water important for global environmental problems. By encapsulating silver colloids in a sol-gel-derived xerogel, SEWS-active coatings were produced with the high mechanical and chemical stability requ ired for underwater field measurements, A flow-through system was used whic h simulates measurements under real how conditions. Substrates were optimiz ed regarding sensitivity to different analytes and long-term stability by v arying solvent type, pH and sol-gel precursors. The substrates were charact erized by their SEWS activity and calibration functions of the Langmuir iso therm type were found for a variety of aromatic hydrocarbons. Limits of det ection as low as 9 ppb for phenylacetylene and 135 ppb for biphenyl were ac hieved. Detailed tests on long-term stability in sea-water yielded a substr ate half-life of 13 days, which resulted in a substrate lifetime of at leas t 5 weeks. Copyright (C) 2000 John Wiley & Sons, Ltd.