Plasmonic nanoparticle-based colorimetric sensing has gained wide attention due to its advantages including rapidity, simplicity and expensive instrument-free characters. In the present study, Ag-Au bimetallic nanoparticles were proposed as novel optical probes to determine cobalt ion (Co2+) concentration. The sensing mechanism is based on the fact that Co2+can react with ethylenediamine (en) and S2O32−to form (en)2CoS2O3+on the nanoparticle surface, which can decrease the negative charge of the nanoparticle, reduce the repulsion between adjacent nanoparticles, and subsequently induce na...
