Colorimetric assay for parallel detection of Cd2+, Ni2+ and Co2+ using peptide-modified gold nanoparticles

A colorimetric assay has been developed for parallel detection of Cd2+, Ni2+ and Co2+ utilizing peptide-modified gold nanoparticles (P-AuNPs) as a sensing element based on its unique surface plasmon resonance properties. The functional peptide ligand, CALNNDHHHHHH, was self-assembled on gold nanoparticles (AuNPs) to produce P-AuNPs probe. The P-AuNPs probe could be used to simultaneously detect and showed different responses to the three ions Cd2+, Ni2+ and Co2+ in an aqueous solution based on the aggregation-induced color change of AuNPs. The method showed good selectivity for Cd2+, Ni2+ and Co2+ over other metal ions, and detection limit as low as 0.05 mu M Cd2+, 0.3 mu M Ni2+ or 2 mu M Co2+. To simultaneously (or parallel) detect the three metal ions coexisting in a sample, EDTA and imidazole were applied to mask Co2+ and Ni2+ for detecting Cd2+, glutathione and EDTA were applied to mask Cd2+ and Co2+ for detecting Ni2+, and glutathione and imidazole were applied to mask Cd2+ and Ni2+ for detecting Co2+. Finally, the simple and cost-effective probe could be successfully applied for simultaneously detecting Cd2+, Ni2+, and Co2+ in river water. Because this novel P-AgNPs-based probe design offers many advantages, including simplicity of preparation and manipulation compared with other methods that employ specific strategies, the sensing system shows potential application in the developing region for monitoring water quality.