Multicomponent Direct Detection of Polycyclic Aromatic Hydrocarbons by Surface-Enhanced Raman Spectroscopy Using Silver Nanoparticles Functionalized with the Viologen Host Lucigenin

Silver nanoparticles (NPs) functionalized with the molecular assembler bis-acridinium dication lucigenin (LG) have been used as a chemical sensor system to detect a group of polycyclic aromatic hydrocarbon (PAH) pollutants in a multicomponent mixture by means of surface-enhanced raman scattering (SERS). The effectiveness of this system was checked for a group of PAHs with different numbers of fused benzene rings, namely anthracene, pyrene, triphenylene, benzocphenanthrene, chrysene, and coronene. In order to determine the host capacity of this sensor system, the self-assembly of the LG viologen on a metallic surface has been checked by analyzing SERS intensities of PAH bands at different LG concentrations. The NP-LG-analyte affinity is derived from the analysis of PAH band intensities at different concentrations of pollutants, the adsorption isotherm of each PAH on NP-LG cavities has been studied, and the corresponding adsorption constants have been evaluated. The limit of detection at trace-level concentration is confirmed by the presence of their characteristic fingerprint vibrational bands. The SERS spectra of PAH mixtures confirm that LG viologen dication shows a higher analytical selectivity to PAHs constituted by four fused benzene rings, mainly pyrene and benzocphenanthrene, in agreement with their higher affinity which is also related to their better fit into the intermolecular LG cavities. As a conclusion, SERS spectra recorded on modified NP-LG surfaces are a powerful chemical tool to detect organic pollutants.