Perchlorate (ClO<sub>4</sub><sup>−</sup>) has emerged as a widespread environmental contaminant found in groundwater and surface water and there is a great need for rapid detection and monitoring of this contaminant. Surface-enhanced Raman scattering (SERS) spectroscopy was found to be capable of detecting ClO<sub>4</sub><sup>−</sup> at concentrations as low as 25 μg/L using poly(diallyldimethylammonium chloride)-modified gold nanoparticles (PDDA-AuNPs) as a substrate. The substrate was successfully fabricated by combining the self-assembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium chloride) (PDDA) as the reducing and stabilizing agents. With the 520 cm<sup>−1</sup> band of silicon as external standard, band intensity ratios of perchlorate to silicon, (i.e., <i>I</i><sub>931</sub>/<i>I</i><sub>520</sub>) were found to have a quantitative relationship with a large concentration range of perchlorate between 25 μg/L and 50 mg/L. The methodology was also reproducible and not susceptible to the interference of other anions such as sulfate, carbonate, nitrate, and chloride at concentrations of 1 mM, making it potentially suitable for rapid screening and routine analysis of perchlorate in environmental samples.
Jun Xiao, Ting Zhang, Rui Li, Yaoyong Meng, and Wei Wen, "Surface-Enhanced Raman Scattering for Quantitative Analysis of Perchlorate Using Poly(diallyldimethylammonium chloride) Capped Gold Nanoparticles," Appl. Spectrosc. 66, 1027-1033 (2012)