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 (Cr 3+ and Cr 6+ ) 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 Cr 3+ and Cr 6+ 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   μM Cr 3+ , 1   μM Cr 6+ , or 10   μM 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 Cr 3+ ), 2.90   nM (Cr 6+ ) and 0.69   nM (mixed chromium ions) respectively, which were all below the guideline value set by World Health Organization (0.962   μM). The practical applicability of the SH-AuNPs was also verified by the detection of chromium ions in natural lake water samples.