Quantitative analysis of chromate (Cr VI ) by normal Raman spectroscopy and surface-enhanced Raman spectroscopy using poly(diallyldimethylammonium) chloride-capped gold nanoparticles

Chromate (Cr VI ) 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. Normal Raman scattering (NRS) spectroscopy with a detection limit of Cr VI at concentrations of 0.2 g/L was attached. And surface-enhanced Raman scattering (SERS) spectroscopy technique was found to be capable of detecting Cr VI at concentrations as low as 2.5 mg/L using poly(diallyldimethylammonium) chloride modified gold nanoparticles (PDDA-AuNPs) as a substrate. The SERS substrate was successfully fabricated by combining the selfassembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium) chloride (PDDA) as the reducing and stabilizing agents. With the 520 cm −1 band of silicon as internal standard, band intensity ratios of Cr VI to silicon, that is I 902 / I 520 , were found to have a quantitative relationship with a large concentration range of Cr VI from 0.2 to 20.0 g/L for NRS ( R 2 = 0.994) and from 2.5 to 25.0 mg/L for SERS ( R 2 = 0.980), respectively. Besides, the SERS methodology was reproducible, and susceptible to the interference of pH value. The optimum pH for Cr VI detection by SERS was 3.38. The application of NRS and SERS showed high practical potential for rapid screening and routine analysis of Cr VI in environmental samples.