Detection of Lead Contamination in Water Using Fluorescence of Functionalized Gold Nanoparticles

The goal of this research was to determine whether functionalized gold nanoparticles can be useful as a sensitive residential fluorescent sensor for lead contamination in drinking water. In the future, such nanoparticles could be dispersed into a membrane visible through a window inside a household tap filter. A large body of work exists in the literature concerning use of gold nanoparticles to detect lead. Almost all of these depend on a visible color shift, which is less sensitive compared to fluorescence and can confuse the consumer. The 5 nm diameter gold nanoparticles (GNPs) were functionalized with 11-mercaptoundecanoic (MUA) acid. Controls and MUA-GNPs were exposed to lead ion/water concentrations as low as the EPA drinking water limit, 15 ppb. The fluorescent response was tested using excitation/emission matrix spectroscopy (EEMS). Corrections were performed on the data for inner filtering and Raman and Rayleigh scattering of water. The GNPs were shown to detect lead at varying concentrations, enhancing the fluorescent intensities of fluorophores at some concentrations and quenching at others. This result is possible if the lead ion was changing the state of aggregation of the colloidal solution in a concentration-dependent manner for the ranges tested and concentration therefore affected the distance at which the ion was adsorbed/spaced from the GNP surface