A simple method to fabricate silver colloid clusters for surface-enhanced Raman scattering

We have developed a simple method to fabricate silver colloid clusters for surface-enhanced Raman scattering (SERS). When colloid particles were immobilized on poly(4-vinyl pyridine) (PVP) films, most of them were immobilized individually. However, the formation of silver colloid particle clusters occurred following a three-step process: immobilizing colloid particles on PVP films, adsorbing target molecules (adsorbates) on the immobilized particles, and then immobilizing colloid particles again. The calculated enhancement factor was approximately 1 x 10(6), which is about 72 times higher than that measured without doing the second immobilization. Our method is relatively simple and inexpensive with respect to fabricating SERS substrates. (C) 2011 Elsevier B.V. All rights reserved.