Colorimetric detection of Cd(II) ions based on di-(1H-pyrrol-2-yl)methanethione functionalized gold nanoparticles

A sensitive and selective colorimetric Cd2+ detection method was developed using di-(1H-pyrrol-2-yl)methanethione functionalized gold nanoparticles (DP-AuNPs). Aggregation of DP-AuNPs was induced immediately in the presence of Cd2+, yielding a color change from red to blue. This Cd2+-induced aggregation of DP-AuNPs was monitored using the naked eye and UV-vis spectroscopy. The SPR absorbance (635 nm) of the reaction between DP-AuNPs and Cd2+ shows a good linearity in the Cd2+ concentration range of 0.5-16 μM and a low detection limit 16.6 nM (S/N = 3). The DP-AuNPs showed excellent selectivity toward Cd2+ compared to other metal ions Ag+, Al3+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+, and Zn2+. Optimal detection of Cd2+ was achieved over a pH range from 4 to 9.5. Furthermore, DP-AuNPs were applied to detect Cd2+ in lake water, showing low interference.