BSA-Protected Gold Nanoclusters for Detection of Pb(II) in Water

Lead (Pb) is among the top most common contaminants in drinking water, generally in its divalent oxidation state (Pb²⁺), arising from several industrial processes including lead-based pipes or solders in water supply systems, gasoline and paint. It’s toxicological manifestations on humans include severe damage to central and peripheral nervous system, anemia and other renal, cardiovascular and reproductive effects. A recent report revealed that approximately 18 million people in the U.S. live in communities where the water systems are in violation of the EPA’s action level of 0.015 mg/L. Up to date, however, there is no easy-to-use and cost-effective technology for detection and quantification of Pb²⁺ in water for household usage. Gold nanoclusters (Au NCs) with sizes < 2 nm display intense photoluminescence due to strong quantum confinement and thus hold incredible promise for optical sensor applications. In this work, bovine serum albumin (BSA) was used to stabilize Au NCs in a simple one-pot and “green” chemical synthesis. First, Au³⁺ ions were reduced in the presence of BSA to form BSA-Au ion complexes. Second, upon addition of NaOH, the complexes were further reduced and aggregated into clusters consisting of 25 gold atoms (Au₂₅). The resulting material is highly luminescent and red-emitting when excited at a wavelength of 470 nm. The BSA-Au NCs were further demonstrated as a “turn-off” sensor in the presence of Pb²⁺ with the potential to enable rapid at-home detection of lead in drinking water.