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Factors Affecting the Sorption of Model Environmental Pollutants onto Silver Polydimethylsiloxane Nanocomposite Raman Substrates

Volume 58, Number 10 (Oct. 2004) Page 1157-1164

De Jesús, M.A.; Giesfeldt, K.S.; Sepaniak, M.J.

The presence of aromatic compounds in water is an important topic in environmental sciences. Silver-polydimethylsiloxane nanocomposites (Ag-PDMS) have recently been demonstrated as promising substrates for the detection of model environmental pollutants via surface-enhanced Raman spectroscopy (SERS). This work discusses how different variables such as pH and matrix composition can affect the sorption and SERS activity of these chemicals. The results show that the conjugate base of weak acids can interact more efficiently with the substrate, leading to an increased signal at higher pH, while amino-aromatic compounds interact more efficiently at a lower pH. The sorption of these chemicals is an essential step in the process and has been attributed to the absorption of the analyte into the PDMS followed by its adsorption to the metallic surface. In addition, the presence of moderate concentrations (1 × 10-4 M) of a supporting electrolyte such as nitrate or fluoride can improve the sorption of 4-hydroxybenzoic acid to the Ag-PDMS nanoparticles. Other ions such as phosphate and chloride cause rapid oxidation of the substrates even at concentrations as low as 1 × 10-5 M. The effect of these variables in the analysis of real samples is presented. The potential use of liquid chromatography for isolating the model pollutants from detrimental matrix components in nat- ural waters is also shown.