Colorimetric detection of Al3+ ions using triazole-ether functionalized gold nanoparticles

A sensitive, selective colorimetric Al(3+) detection method has been developed by using triazole-ether functionalized gold nanoparticles (TTP-AuNPs). Gold nanoparticles were prepared by reducing HAuCl4 with sodium borohydride in the presence of 5-(1,2-dithiolan-3-yl)-N-(prop-2-yn-1-yl)pentanamide (TP). The azide part of 2-[2-(2-azidoethoxy)ethoxy]ethanol and the acetylene part of TP were combined to form a triazole structure through a click reaction. Aggregation of TTP-AuNPs was induced immediately in the presence of Al(3+) ions, yielding a color change from red to blue. This Al(3+)-induced aggregation of TTP-AuNPs was monitored first with the naked eye and then UV-vis spectroscopy with a detection limit of 18.0 nM. The TTP-AuNPs showed excellent selectivity for Al(3+), compared to other metal ions (Ag(+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Fe(2+), Fe(3+), Hg(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), and Zn(2+)). In addition, TTP-AuNPs were used to detect Al(3+) in sea water samples, with low interference.