Microwave monitoring of silver nanoparticle sintering for surface-enhanced Raman scattering substrates

One of the most widely used methods for surface‐enhanced Raman scattering (SERS) employs silver or gold nanoparticles either in colloidal suspension or in the dry‐drop form. In such substrates the SERS amplification factors depend critically on the interparticle distances. Here, we report that microwave absorption as a function of temperature in dry‐drop substrates can be used as a probe to demarcate temperature regions for thermal annealing to produce SERS substrates with very high amplification factors. Copyright © 2011 John Wiley & Sons, Ltd. The signal amplification observed in surface‐enhanced Raman scattering is highly influenced by the interparticle separation in metallic colloidal‐based substrates. Microwave absorption is shown to be a sensitive probe to monitor silver nanoparticle sintering as a function of temperature. Because the microwave losses occur predominantly at the weak electrical links between nanoparticles, microwave absorption monitoring can serve as a guide in determining thermal annealing treatments to optimize surface‐enhanced Raman scattering substrate performance.