Highly sensitive SERS determination of chromium(VI) in water based on carbimazole functionalized alginate-protected silver nanoparticles

An easily manipulated method was developed to synthesize silver nanoparticles (AgNPs) by using sodium alginate (SA) to perform the dual role of reducing and protecting agent. Using SA-protected AgNPs as substrates, a simple and ultra-sensitive surface-enhanced Raman scattering (SERS) method was established for the determination of Cr(VI) in water. The method is based on redox reaction of carbimazole with Cr(VI). In the presence of Cr(VI), the SERS signal of carbimazole decreases with the increase of dichromate concentration, so as to achieve the purpose of indirect determination of Cr(VI). The volume of AgNPs, the acidity of the system and the concentration of NaCl solution were optimized. Under optimum conditions, a good linearity (r = 0.993) in the range of 1.71–171 × 10−9 mol L−1 was obtained and the limits of detection (LOD) is 1.01 × 10−9 mol L-1. The method was applied to the determination of Cr(VI) in water, with recoveries between 97.9–104.0% and with relative standard deviations of <4.0% (n = 5).