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

Overview & Synopsis

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.