Strategy for improved analysis of peptides by surface-enhanced Raman spectroscopy (SERS) involving positively charged nanoparticles

A strategy for improved surface-enhanced Raman spectroscopy (SERS) measurements that extends the variety of analytes accessible to SERS analysis is developed. The strategy involves inducing aggregation by mixing positively charged nanoparticles which form SERS-active clusters when mixed with negatively charged silver nanoparticles fabricated using the Lee-Meisel process. To make positively charged nanoparticles, silver nanoparticles using the traditional Lee-Meisel process are fabricated and coated with a thin layer of silica and the silica modified with silane chemistry. Analytes with a significant amount of negative charge exhibit strong Raman bands when the strategy using these fabricated, positively charged nanoparticles for inducing cluster formation is used, enabling their detection and analysis. We envision the use of positively charged nanoparticles in cluster formation for expanding the range of analytes that can be detected using SERS and hence the range of applications SERS can play a role in. Copyright (C) 2008 John Wiley & Sons, Ltd.