Rational Design and Engineering of Conducting Polymers for Chemical Enhancement in Raman Scattering

Abstract

Raman scattering is characterized by the inherently weak inelastic scattering of photons, influenced by molecular vibrations or rotations. Recent advances have shifted from traditional electromagnetic enhancement methods to chemically enhanced Raman scattering, offering significant advantages. However, these advancements have typically depended on indirect and empirical models. This article introduces a systematic method for the rational design and engineering of chemical enhancement to Raman scattering. This method involves identifying promising Raman enhancers and optimizing their morphology and composition by elucidating their photochemical properties and mapping their charge-transfer pathways with target molecules using transient absorption spectroscopy (TAS), cyclic voltammetry (CV), and density functional theory (DFT) calculations. Employing this method, this work has developed a series of rationally designed Raman enhancers made from conducting polymers (CPs), such as poly(3,4-ethylenedioxythiophene) (PEDOT), with optimized morphological traits and compositions. These enhancers significantly improve surface-enhanced Raman spectroscopy (SERS), achieving a reproducible enhancement factor of up to 10⁶, and boost Raman lasing, with a remarkable 40-fold increase in energy conversion efficiency.