Gold Nanoparticles-Based Dual-Channel Colorimetric Array Sensors for Discrimination of Metal Ions

This report describes dual-channel colorimetric array sensors for rapid distinction of metal ions. This dual-channel sensing array is built based upon gold nanoparticles (AuNPs)-catalyzed two colorimetric reactions [3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 as channel 1 and HAuCl4 and NH2OH as channel 2]. Different metal ions show diverse interactions toward AuNPs, producing differential variations of AuNPs' catalytic ability and yielding distinct colorimetric response modes (channel 1). Different metal ions show different affinities toward the DNA absorbed on the AuNP surface, and the decrease of the amount of DNA entangled on the AuNPs changes the catalytic ability of the AuNPs to varying degrees, generating varying visual response modes (channel 2). These signal modes as "fingerprints" are typical for each metal ion and are analyzed by linear discriminant analysis (LDA). The results display clear discrimination of each analyte on a LDA plot, and 10 kinds of metal ions are well identified at a low concentration (20 nM).