Gold nanoparticles based colorimetric probe for Cr(III) and Cr(VI) detection

A simple and highly practical colorimetric method has been proposed for detection of chromium ions (Cr3+ and Cr6+) synchronously by sodium hyaluronate functionalized gold nanoparticles (SH-AuNPs). The SH-AuNPs were synthesized and characterized by UV-vis spectra and transmission electron microscopy (TEM). The colorimetric response of Cr3+ and Cr6+ can be performed simultaneously by the same probe SH-AuNPs, based on the property of special localized surface plasmon resonance (LSPR). The interaction between chromium ions and sodium hyaluronate causes rapid aggregation of the SH-AuNPs conjugates and a concurrent color conversion from wine red to blue gray which is clearly detectable by the naked eye. By using SH-AuNPs as colorimetric probe, the color change with 3 mu M Cr3+, 1 mu M Cr6+, or 10 mu M mixed chromium ions can be recognized easily by naked eye with highly selectivity. The detection limit calculated by the linear relationship of LSPR were at 0.78 nM (for Cr3+), 2.90 nM (Cr6+) and 0.69 nM (mixed chromium ions) respectively, which were all below the guideline value set by World Health Organization (0.962 mu M). The practical applicability of the SH-AuNPs was also verified by the detection of chromium ions in natural lake water samples.