Approaches to Uniform-Morphology: Polymer-Based SERS Substrates

Polymer-nano-metallic-particle composites have demonstrated technological potential due to their unique optical and electrical properties. We report on composites prepared via physical vapor deposition of silver and gold onto pliable polydimethlysiloxane (PDMS) polymer. Rapid metal diffusion and nano-metallic-particle formation in a phase-separated surface layer of the PDMS creates unique sub-surface-based composites that vary in properties based on rate of deposition and average metal thickness. In addition, nano-metallicparticle spacing can be altered with fair reproducibility and reversibility by physically manipulating the composite. A practical technological characteristic of these composite materials arises from their potential to be molded into functional devices. Surface enhanced Raman scattering (SERS) substrate selectivity and the analytical figures of merit, such as reproducibility and dynamic range have limited the general acceptance of the technique for routine analytical applications. Herein, we explore the potential approaches to fabricate polymerbased substrates with uniform morphology by electron beam lithography, imprinting, and casting. The objective is to produce a homogeneous analyte environments that will address the issues associated with the figures of merit.The optical properties of the materials are studied by visible wavelength optical extinction spectrometry and SERS. DC conductivity measurements were made during depositions to study percolation conditions for the materials. Depth-profiling was performed by X-Ray Photoelectron Spectrometry.