A simple and rapid colorimetric method for the determination of Mn2+ based on pyrophosphate modified silver nanoparticles

A simple, and reliable colorimetric detection method for manganese ion (Mn2+) based on pyrophosphate capped silver nanoparticles (P2O74--AgNPs) is developed. The P2O74--AgNPs was synthesized by wet chemical method. The P2O74--AgNPs solution shows a yellow color and the maximum absorption at 403 nm can be observed. After the addition of Mn2+, the absorption intensity of the P2O74--AgNPs solution decreased drastically, which associated with the changes of solution color from yellow to purple. The observed changes can be attributed to the aggregation of AgNPs induced by Mn2+ because of the ion-templated chelating reaction. The absorption intensity of P2O74--AgNPs at 403 nm is found to be proportional to the concentration of Mn2+ in the range of 0.03-20 mu M, and the detection limit for Mn2+ is as low as 0.03 mu M (S/N = 3). Due to high affinity toward Mn2+, the P2O74--AgNPs as a colorimetric sensor displays an excellent selectivity for Mn2+ detection. More important, the proposed method was successfully applied in the determination of Mn2+ in real environmental samples. (C) 2015 Elsevier B.V. All rights reserved.