A colorimetric probe for the detection of aluminum ions based on 11-mercaptoundecanoic acid functionalized gold nanoparticles

An easy, simple and selective colorimetric method for aluminum ions has been developed using 11-mercaptoundecanoic acid functionalized gold nanoparticles (MUA-AuNPs). The MUA-AuNPs could be induced to aggregate in the presence of Al3+ ions according to the chelation effect between the carboxyl group and Al3+, and a color change from red to purple with increasing Al3+ ion concentration was observed. The plasmon absorbance of the MUA-AuNPs allows the quantitative detection of Al3+ ions. A sensitive linear correlation existed between the ratio of absorbance at 650 nm to that at 520 nm and the Al3+ ion concentration ranging from 10(-6) M to 10(-4) M. The detection limit was 5.7 x 10(-7) M, which is below the maximum recommended contamination level of the World Health Organization (WHO) for the aluminum content (7.4 mu M) in drinking water. The MUA-AuNPs chelated with Al3+ showed excellent selectivity in the presence of EDTA compared to other metal ions (Ag+, Ba2+, Ca2+, Cd2+, Cr3+, Cu2+, Fe2+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+ and Zn2+). The proposed method can offer the additional advantage of the efficient determination of Al3+ ions in drinking water, and the recovery was in the range of 98.5-101.6% with a relative standard deviation below 2%.