Colorimetric detection of Fe(III) ions using label-free gold nanoparticles and acidic thiourea mixture

We report colorimetric, label-free, and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Fe(III) ions in aqueous environments. This detection scheme relies on the ability of Fe(III) ions to catalyze the leaching of gold at room temperature in the presence of thiourea species and hydrochloric acid. The catalytic leaching of the AuNP probes results in rapid and remarkable damping of the surface Plasmon band and hence induces a visible color change which can be easily detected through naked eye. This simple and cost-effective probe provides rapid detection of Fe(III) ions at concentrations as low as 50 ppm and expected to be effective to design efficient environmental and biological sensor.