Deposition method for preparing SERS-active gold nanoparticle substrates

Surface-enhanced Raman scattering or SERS, discovered some 20 years ago, has recently become a promising tool for routine biofluid assays in a clinical setting. Many attempts have been made to produce cheap and reproducible SERS-active substrates. In this study, we report on the fabrication of SERS-active substrates through the convective assembly of gold (An) particles on electrostatically charged glass slides. We show that, by a proper control of the initial particle concentration in an evaporating Au suspension droplet, it is possible to obtain a closely packed colloidal film capable of generating SERS activity. Finally, AFM and SERS measurements of the resulting films reveal comparability in performance with previous silane-immobilized An colloidal films. The minimum electromagnetic enhancement factor of our films is estimated to be about 2 x 10(4).