Colorimetric detection of Cr(vi) using silver nanoparticles functionalized with PVP

As a priority pollutant in the environment, hexavalent chromium (Cr(vi)) has received increasing attention. In this work, a safe, simple, low-cost, effective and sensitive colorimetric strategy for the determination of Cr(vi) was introduced based on polyvinylpyrrolidone (PVP) functionalized silver nanoparticles (PVP-AgNPs). The prepared PVP-AgNPs had good dispersibility, and exhibited a state change from dispersed to aggregated when Cr(vi) was present in pH 5.5 PBS buffer due to the special and strong coordination between PVP and Cr(vi), accompanied by a color change from bright yellow to orange. Under the optimized conditions, the concentration of Cr(vi) in the range of 1.0 x 10(-7) M to 2.4 x 10(-6) M showed a good linear relationship with the ratio of the absorbance at 530 nm to that at 390 nm (A(530 nm)/A(390 nm)), and the limit of detection (LOD) was 34 nM. The method also showed good precision and high repeatability in determining Cr(vi) in real water samples such as pond water, tap water and river water. The recoveries ranged from 93.5% to 104.3%, indicating the method can be used for an extensive range of practical applications.