Ag decorated sea urchin-MoO3 based hierarchical micro-nano structures as surface - enhanced Raman spectroscopy substrates for the detection of a nitrosamine industrial pollutant

Abstract

Sea urchin MoO3 with low loading of silver (Ag/SUMoO3) forming hierarchical micro-nano structures are explored as surface-enhanced Raman scattering (SERS) substrates. Owing to the high concentration of oxygen defects and consequently, Mo+5 states, possessing unique morphology of sea urchins, SUMoO3 are beneficial for achieving superior SERS properties. Silver nanoparticles are decorated on SUMoO3 by photoreduction, achieving an excellent Ag-MoO3 interface without the use of any coupling agents and the underlying scaffold prevents the silver from aggregation and oxidation. Ag/SUMoO3 substrate shows a high enhancement factor of 9.2 × 109 and a detection limit of 1 nM for 4-mercaptobenzoic acid. The synergetic effect of charge transfer enhancement from defect-rich SUMoO3 coupled with electromagnetic enhancement from silver nanoparticles is responsible for the high enhancement factor. Further, the detection of an environmental pollutant and a potent carcinogenic, N-nitrosodiphenylamine (NDPhA) up to 10−5 M is demonstrated using Ag/SUMoO3 as a SERS substrate for the first time. Antibacterial testing reveals the higher zone of inhibition achieved for Ag/SUMoO3 against E. coli than for bulk MoO3-Ag revealing the superior role of the unique morphology and composition of Ag/SUMoO3.