The selective detection of Fe3+ ions using citrate-capped gold nanoparticles.

Citrate is a ubiquitous biological molecule that functions as Fe3+ chelators in some bacteria and the blood plasma of humans. Inspired by the strong affinity between citrate and Fe3+, a colorimetric Fe3+ probe based on citrate-capped AuNPs without any additional modification was designed. Citrate-capped AuNPs with a diameter of 22 nm were applied to detect Fe3+ without other reagents' assistance. This easily-prepared and low-cost colorimetric sensor exhibited good selectivity towards Fe3+ among common metal ions, a good linear relationship in the range of 0.1-0.8 µM of Fe3+ and quick response time of 10 min.