title: Surface-enhanced Raman scattering of perchlorate on cationic-modified silver nanofilms - Effect of inorganic anions.
abstract: 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 adsorption of ClO4(-) ions. In the solutions with multiple anions present, the 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 ClO4(-) in the matrix.
authors.affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA; Agiltron Inc., 15 Presidential Way, Woburn, MA 01801, USA.
authors.forename: Jumin
authors.initials: J
authors.lastname: Hao
authors.affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. Electronic address: jhao@stevens.edu.
authors.forename: Mei-Juan
authors.initials: MJ
authors.lastname: Han
authors.affiliation: Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Meng
authors.affiliation: Agiltron Inc., 15 Presidential Way, Woburn, MA 01801, USA.
authors.forename: Wayne
authors.initials: W
authors.lastname: Weimer
authors.affiliation: Agiltron Inc., 15 Presidential Way, Woburn, MA 01801, USA.
authors.forename: Qingwu K
authors.initials: QK
authors.lastname: Wang
keywords: Cationic thiol; Competitive adsorption; Inorganic anions; Perchlorate detection; Silver nanofilm; Surface-enhanced Raman scattering (SERS)