Highly selective and sensitive paper-based colorimetric sensor using thiosulfate catalytic etching of silver nanoplates for trace determination of copper ions

Abstract

A novel, highly selective and sensitive paper-based colorimetric sensor for trace determination of copper (Cu2+) ions was developed. The measurement is based on the catalytic etching of silver nanoplates (AgNPls) by thiosulfate (S2O32-). Upon the addition of Cu2+ to the ammonium buffer at pH 11, the absorption peak intensity of AuNPls/S2O32- at 522nm decreased and the pinkish violet AuNPls became clear in color as visible to the naked eye. This assay provides highly sensitive and selective detection of Cu2+ over other metal ions (K+, Cr3+, Cd2+, Zn2+, As3+, Mn2+, Co2+, Pb2+, Al3+, Ni2+, Fe3+, Mg2+, Hg2+ and Bi3+). A paper-based colorimetric sensor was then developed for the simple and rapid determination of Cu2+ using the catalytic etching of AgNPls. Under optimized conditions, the modified AgNPls coated at the test zone of the devices immediately changes in color in the presence of Cu2+. The limit of detection (LOD) was found to be 1.0ngmL-1 by visual detection. For semi-quantitative measurement with image processing, the method detected Cu2+ in the range of 0.5-200ngmL-1(R2=0.9974) with an LOD of 0.3ngmL-1. The proposed method was successfully applied to detect Cu2+ in the wide range of real samples including water, food, and blood. The results were in good agreement according to a paired t-test with results from inductively coupled plasma-optical emission spectrometry (ICP-OES). © 2015 Elsevier B.V.