Toward surface-enhanced Raman scattering using electroless substrate for trace arsenic detection and speciation

Description

Arsenic is one of the most toxic elements present in the environment, especially in water. The World Health Organization (WHO) recommends a maximum concentration of arsenic in drinkable water of 10 µg/L (10 ppb). Sensors implementing Surface Enhanced Raman Scattering (SERS) can detect chemical species at low concentrations. The aim of this study is to compare two kinds of silver-coated SERS substrates for detection and speciation of trace, trivalent and pentavalent, inorganic arsenic compounds. One type of substrates was prepared by a classical thermal evaporation technique, the second type by an electroless process. The thermally evaporated substrates allowed the detection of As(III) only, at a limit of detection (LOD) of approximately 50 mg/L, whereas As(V) could not be detected at any analyte concentration. The electroless substrates allow to differentiate As(III) and As(V) with a LOD 1 µg/L (1 ppb) equal for each valency, below WHO recommendation. The electroless substrates show a very large sensitivity across up to five orders of magnitude in terms of analyte concentration. Although the SERS intensity shows a nonlinear behaviour over this range of concentrations, these preliminary results are encouraging in the framework of the demonstration of trace As SERS sensors in drinkable water.

Abstract

International audience

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