Transformation of Gold Nanoparticles in Presence of Humic Substances

The interaction of biomedical imaging gold nanoparticles with environmental entities such as humic substances was investigated applying Dynamic light scattering (DLS). The increasing applications of gold nanoparticles in biomedical imaging and cancer therapy indicate potential for their subsequent release into surface waters. Therefore, it is primarily important to understand the interactions of gold nanoparticles with natural organic matter (humic substances), which will play a major role in the fate and transport of these particles in aquatic systems. The current study investigates the size changes taking place on citrate coated gold nanoparticles (core sizes 5 and 10 nm) in the presence of commercial humic acid having concentrations of 2 and 8 ppm. Humic acid controls at the same concentration exhibited micron sized aggregates based on volume- average size distributions, however the humic acid aggregates were absent when mixed with the citrate-coated gold nanoparticles. The size analysis data suggests that humic acid stabilizes gold nanoparticles and acts as a carrier.