Selective enhancement of Raman or fluorescence spectra of biomolecules using specifically annealed thick gold films

Annealing of "thick" metal films deposited onto a smooth dielectric substra te leads to high-order self-organization of metal clusters on the film surf ace. This work presents the first experimental evidence that the "thick" go ld film (TGF) may be specifically annealed to serve as a substrate for surf ace-enhanced fluorescence or surface-enhanced Raman scattering (SERS) spect roscopy of the same molecule. High-resolved SERS spectra of mitoxantrone (m itox) were recorded on the TGF annealed at 340 degrees C whereas no Raman e nhancement but an increase of miter fluorescence signal were detected on th e TGF annealed at 240 degrees C. The miter fluorescence was further enhance d by deposition of monolayers of pentanethiol or poly-L-lysine on the surfa ce of annealed TGF. The maximal fluorescence enhancement factor per miter m olecule of approximately 50 that was obtained on the annealed TGF covered w ith poly-L-lysine makes the system promising for applications in immunofluo rescence assays and in microspectrofluorescence analysis. (C) 2000 John Wil ey & Sons, Inc.