Synthesis and stability analysis of papain-functionalized gold nanoparticles (P-AuNPs) for the colorimetric detection of mercury in milk

To detect mercury in dairy cow milk by colorimetric techniques, papain-functionalized gold nanoparticles (P-AuNPs) were synthesised. Papain-functionalized gold nanoparticles aggregated when mercury ions were introduced, causing their absorption peak to shift from 525 to 575 nm. Dynamic light scattering and transmission electron microscopy determined that aggregated P-AuNPs average sizes were 26.60 nm and 15.17-18.23 nm, respectively, with monodispersed. The detection limit of P-AuNPs for mercury in milk samples was 1.0 ppm with high recovery. This sensor showed relatively high selectivity and sensitivity towards Hg2+ ions in milk. This method shows utility in developing countries for monitoring the concentration of Hg2+ in water, milk and food items for safety purposes.