Effects and mechanisms of water matrix on surface-enhanced Raman scattering analysis of arsenite on silver nanofilm

Abstract

Abstract Ag nanofilm was synthesized using a modified mirror reaction and used as surface-enhanced Raman scattering (SERS) substrate for analysis of arsenite (As(III)). The SERS substrate can detect 20 and 50 μg L −1 As(III) spiked in aged tap water and groundwater respectively. The effect of nine common ions (Na + , K + , Ca 2+ , Mg 2+ , NO 3 − , CO 3 2− , HPO 4 2− , SO 4 2− and Cl − ) in natural water on SERS of 0.5 mg L −1 As(III) was investigated. Na + and K + (100 mg L −1 ) had no obvious negative effects on the SERS intensity of 0.5 mg L −1 As(III), but Ca 2+ and Mg 2+ significantly decreased that of 0.5 mg L −1 As(III) as their concentrations increased to 1 and 10 mg L −1 respectively. NO 3 − , SO 4 2− and CO 3 2− (HPO 4 2− ) had negligible, medium and significant inhibition on the SERS of As(III) respectively. The inhibition effect of Ca 2+ might be through the formation of surface complexes with As(III) on SERS substrate. The inhibition effect of CO 3 2− , HPO 4 2− and SO 4 2− could be explained by the competitive adsorption of anions with As(III) for adsorption sites of Ag nanofilm. It was confirmed that Cl − can activate the SERS of As(III) alone and in the presence of Ca 2+ , CO 3 2− , HPO 4 2− and SO 4 2− . The activation effect of Cl − on SERS of As(III) could be attributed to charge transfer (CE) mechanism.