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

Jumin Hao; Mei-Juan Han; Xiaoguang Meng; Wayne Weimer; Qingwu K Wang

doi:10.1016/j.saa.2014.10.052

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

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Feb 5:136 Pt C:1593-9. doi: 10.1016/j.saa.2014.10.052. Epub 2014 Oct 24.

Authors

Jumin Hao¹, Mei-Juan Han², Xiaoguang Meng³, Wayne Weimer⁴, Qingwu K Wang⁴

Affiliations

¹ Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA; Agiltron Inc., 15 Presidential Way, Woburn, MA 01801, USA.
² Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA. Electronic address: jhao@stevens.edu.
³ Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
⁴ Agiltron Inc., 15 Presidential Way, Woburn, MA 01801, USA.

PMID: 25459720
DOI: 10.1016/j.saa.2014.10.052

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.

Keywords: Cationic thiol; Competitive adsorption; Inorganic anions; Perchlorate detection; Silver nanofilm; Surface-enhanced Raman scattering (SERS).