Gold nanoparticles can be used in medicine, sensors, diagnostics, etc. As the use of gold nanoparticles increase so does the risk that they can contaminate the environment. Humic acid is a naturally occurring acid produced from decaying organic matter. Using fluorescence quenching, the bond strength between the gold nanoparticles and humic acid was investigated. The nanoparticles were synthesized using two methods: 1) electrolysis of pure gold wire and stabilized with polyvinylpyrrolidone (PVP) and 2) reflux reaction with stabilization by trisodium citrate. The nanoparticles were purified by centrifugation. The humic acid fluorescence was quenched with the addition of the gold nanoparticles and then Stern-Volmer plots were constructed. The quenching experiment was repeated at temperatures from 20 °C to 35 °C and then the slopes were used to determine that static quenching was occurring. A van’t Hoff plot was produced and the slope was used to determine Δ<i>H</i> = 5.85 ± 20 kJ/mol for binding of the humic acid to the gold nanoparticles for the PVP-stabilized nanoparticles and Δ<i>H</i> = 7.83 ± 35 kJ/mol for citrate stabilized nanoparticles. The large standard deviation is likely due to uncertainty in the bond site of the nanoparticles to humic acid and possible decomposition of the nanoparticles. The small bond strength between gold nanoparticles and humic acid indicates that dispersion forces are holding them together. Given that the bond energy is small it is hypothesized that the gold nanoparticles will be more easily transported throughout the environment and more bioavailable.

Exploring the effects of gold nanoparticles binding to humic acid via fluorescence quenching

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.