Investigation of Interfacial Charge Transfer in a Ag/MBA/P3HT Sandwich System via Surface-Enhanced Raman Scattering

A silver/mercaptobenzoic acid/poly(3-hexylthiophene) (Ag/MBA/P3HT) composite system with a tunable concentration of P3HT was fabricated via layer-by-layer self-assembly for surface-enhanced Raman scattering (SERS) applications. Notably, the SERS intensity of MBA systematically increased and reached a maximum at a P3HT concentration of 10^-5 g/mL. Mechanistic studies revealed that the incorporation of P3HT significantly enhanced the electronic conjugation within the composite system through π-π interactions between P3HT and MBA molecules. The improved electron delocalization facilitated better matching between molecular vibrational excited states and charge transfer (CT) processes, thereby promoting the efficient transfer of electrons from the Ag substrate to MBA molecules. As the P3HT concentration further increased, the extended conjugation network enhanced the CT efficiency in the Ag/MBA/P3HT system, resulting in a strong positive correlation between the SERS intensity and P3HT concentration. This study provides valuable theoretical insights and practical strategies for developing high-performance SERS-active substrates.