SERS-based detection of an organochlorine pesticide through surface plasmon-induced C–C coupling

Abstract

Palladium-catalyzed Suzuki–Miyaura cross-coupling is among the most widely used processes for C–C bond formation by coupling between C-halide compounds and boronic acids. The modification of nanoparticles (NPs) with 4-mercaptophenylboronic acid (4-MPBA) opens up the possibility for the SERS analysis of organochlorine pesticides (OPs) through C–C bond formation. Herein, the SERS-based detection of OPs was achieved through surface plasmon-induced Suzuki–Miyaura C–C cross-coupling, catalyzed by 4-MPBA-functionalized AgNPs with varying Pd loading (AgPd_{x mol%}NPs). The results showed that the catalytic activity increases linearly as a function of the Pd loading, due to the efficient injection of surface plasmon-generated hot electrons into surface Pd atoms in close contact with Ag atoms and consequent delay of the deboronation side reaction; while the SERS activity diminishes exponentially as a function of Pd content, due to the damping of surface plasmon resonance arising from Ag. Optimized reaction parameters considering the base concentration in the reaction mixture, the incoming laser power density, and the Pd content in AgPd_{x mol%}NPs were employed for SERS detection of an OP via cross-coupling at micromolar levels. This work provides a viable methodology for the SERS-based detection of halogenated pesticide residues and related compounds in water samples.