Surface-enhanced Raman scattering of perchlorate on cationic-modified silver nanofilms - Effect of inorganic anions

(Graph Presented). Surface-enhanced Raman scattering (SERS) has emerged as one of the most sensitive spectroscopic analysis methods for the detection of environmental contaminants in water, including perchlorate (ClO₄^-). However, as with other commonly used analytical techniques, analysis of realistic environmental samples by SERS presents a challenge due to complex chemical components coexisting in the samples. In this work, we investigated the influence of inorganic anions (particularly oxyanions) on SERS spectra of ClO₄^- using a cationic thiol modified silver nanofilm substrate (Cys-Ag/rCu). The results show that the anions present in the samples did not shift the ClO₄^- characteristic band positions, but did decrease signal intensities due to their competitive binding with the -NH₃⁺ groups of cationic thiol molecules immobilized on the substrates. The pH changes caused by both the dissociation of H₂PO₄^- and the hydrolysis of HCO₃^- may also play a non-negligible role. The selectivity of the Cys-Ag/rCu substrate towards these anions was determined to be in the following order: ClO₄^- > SO₄^2- > HCO₃^-, NO₃^- > Cl^- > H₂PO₄^-, indicating preferential ions. In the solutions with multiple anions present, the ClO₄^- adsorption of ClO₄^- SERS spectra were affected simultaneously by all the coexisting anions. Calibration curves with very good linear relationships were successfully obtained, demonstrating the great potential of quantitative detection of aqueous in the matrix.