A specific colorimetric probe for phosphate detection based on anti-aggregation of gold nanoparticles

A simple, highly sensitive and selective colorimetric strategy for phosphate (Pi) detection is proposed based on anti-aggregation of gold nanoparticles (AuNPs) via competition reaction between Pi and carboxylate group-modified AuNPs for Eu3+ ions. In the presence of Eu3+, MA-AuNPs underwent an aggregation process due to the coordination of Eu3+ with neighboring carboxylate groups, revealing a color change from wine red to blue. Once Eu3+ ions were pre-mixed with Pi and then introduced into MA-AuNPs, the coordination of carboxylate groups with Eu3+ would be significantly interrupted due to the higher binding affinity of Eu3+ for Pi. Accordingly, the solution color of MA-AuNPs changed from blue to red with increasing the concentration of Pi. The anti-aggregation effect of Pi on AuNPs was seen by the naked eye and monitored by UV–vis extinction spectra. The linear range of the colorimetric sensor for Pi is from 5.0 × 10−7 M to 3.0 × 10−5 M with a low detection limit of 76 nM. The as-established colorimetric strategy opened a new avenue for Pi determination.