Al3+ ion sensing at attomole level via surface-potential mapping of gold nanoparticle complexes

Abstract

Aluminum can be ionized in water by reacting with chlorides. Aluminum ions (Al3+) are believed to be very harmful to human health and are associated with Alzheimer's disease. The detection of Al3+ is extremely important, but conventional methods suffer from low sensitivity and cumbersome processes. Herein, we report ultra-sensitive and label-free detection of Al3+ using gold nanoparticles (AuNPs) and Kelvin probe force microscopy (KPFM). Al3+ was exposed on citrated AuNPs with different concentrations; Al3+/AuNP complexes were constructed via binding interactions between Al3+ and the citrates. By probing the Al3+/AuNP complexes, we quantified the degree of interactions between Al3+ and the citrated AuNPs using KPFM. As the Al3+ concentration decreased, KPFM succeeded in exhibiting ultra-sensitive detection as low as 2 amol (limit of detection 1 pM, single droplet 2 mu L). We tested real samples from a sheet of aluminum foil, and detected similar to 748 amol (similar to 374 pM, single droplet 2 mu L) Al3+. The results indicate that the combination of AuNPs and KPFM offers a robust, facile, and an ultra-sensitive platform technology for detecting Al3+. (C) 2017 Elsevier B.V. All rights reserved.