One-step fabrication of dopamine-inspired Au for SERS sensing of Cd2+ and polycyclic aromatic hydrocarbons

Abstract

We report the development of a versatile surface-enhanced Raman scattering (SERS) sensor based on the use of multifunctional polymer-coated Au colloids. Our results demonstrated that dopamine (DA) serves as a reducing agent for the facile one-pot synthesis of Au nanoparticles (NPs). Under Au reductive conditions, DA was subsequently oxidized to dopamine quinone (DQ), 5,6-dihydroxyindole (DHI), and polydopamine (PDA) via classical Raper–Mason mechanism. HPLC-MS, FTIR, and SERS analysis verified the effect of initial DA concentration on its oxidation products. The universal adhesion of DA, DQ, DHI, and PDA on Au surface allows for customized synthesis of multi-sized and multifunctional Au NPs containing different mussel polymer shells. The PDA on Au exhibited a reactive scaffold to exclusively lock PAHs into the hotspots for SERS sensing. More interestingly, the two-dimensional correlation spectroscopy showed that DQ modified Au exhibited a strong binding ability towards Cd2+, yielding SERS vibrational profiles that allowed the qualitative determination of Cd2+ with a detection limit of 10−8 mol L−1. The systematic investigation reported herein fills significant gaps in the understanding of the DA-mediated Au reduction mechanism, and provides a reliable working basis that allows for the formation of melanin-like polymer coatings on the Au surface. Remarkably, this simple method provides high SERS sensitivity and selectivity in a high-throughput fashion without the requirement for complex pretreatment methods and complicated instruments.