Chemically Enhanced Raman Scattering Enabled by Organic Semiconductor Molecules with Deep Lowest Unoccupied Molecular Orbitals.

Abstract

Organic semiconductor materials (OSMs) have emerged as innovative platforms for surface-enhanced Raman scattering (SERS). For now, SERS activity has been established in only a few materials like thiophene-based derivatives, and the potential of the broader OSM library is largely untapped. Systematic exploration of energy level alignment between analytes and the OSM substrates is highly desirable for further material screening and optimization. We introduce a strategy utilizing OSMs with the deep lowest unoccupied molecular orbital (LUMO) levels, exemplified by TCNQ and HATCN, as novel SERS active platforms realizing efficient detection of multiple organic dyes otherwise undetectable under low-energy incident laser irradiation at 785 nm. Our study showcases selective SERS enhancement for analytes with diverse highest occupied molecular orbital levels, highlighting the pivotal role of LUMO levels in both SERS activity and molecular sensitivity. This work elucidates the molecular structure-SERS activity correlation, facilitating the development of novel SERS substrates via the strategy of LUMO level tuning.