A new rapid colorimetric detection method of Al3+ with high sensitivity and excellent selectivity based on a new mechanism of aggregation of smaller etched silver nanoparticles

As a pathogenic factor of the Alzheimer׳s disease, aluminum has been associated with the damage of the central nervous system in humans. In this study, we propose a new facile and rapid colorimetric detection method of Al3+ with excellent selectivity and high sensitivity based on silver nanoparticles (AgNPs) stabilized by reduced glutathione (GSH) in the presence of l-cysteine (Cys). The new mechanism of our Al3+ detection system based on GSH-AgNPs, i.e., aggregation of smaller etched GSH-AgNPs, are confirmed by TEM, EDS and DLS. The aggregation of smaller etched GSH-AgNPs results in obvious color change of the nanoparticle dispersion from yellow to reddish brown, and red shift and intensity decrease of the surface plasmon resonance (SPR) absorption. The GSH concentration, Cys concentration and pH value of the GSH-AgNPRs-based detection system are respectively optimized to be 10.0 mM, 50.0 mM and 6.0 according to the sensing effect of Al3+. At the optimized conditions, the selectivity of the GSH-AgNPs detection system for Al3+ is excellent compared with other ions including K+, Mg2+, Fe3+, Co2+, Mn2+, Zn2+, Cd2+, Pb2+, Ca2+, Ba2+, Cu2+, Cr3+, Hg2+, Ni2+, Cr 2 O 7 2 − , SO 4 2 − , C 2 O 4 2 − , PO 4 3 − and CO 3 2 − . Furthermore, this detection system is very sensitive for Al3+. The limit of detection (LOD) is 1.2 µM by the naked eyes and 0.16 µM by UV–vis spectra, which are both much lower than the national drinking water standards (7.4 µM). Furthermore, the UV–vis detection offers a good linear detection range from 0.4 to 4.0 µM (R2=0.9924), which indicates that our developed detection system can also be used for the quantitative analysis of Al3+. The detection results of real water samples indicate that this method can be used for real water detection.