Effects of humic acid and sunlight on the generation and aggregation state of aqu/C60 nanoparticles.
Aqueous suspensions of nanoscale C(60) aggregates (aqu/C(60)) were produced by stirring in water with Suwanee River Humic Acid (humic acid) and water from Call's Creek, a small stream near Athens, GA. Time course experiments were conducted to determine the effects of sunlight and solution chemistry on the mass of aqu/C(60) suspended, nanoparticle size, and ζ potential. For all treatments, sunlight had the greatest effect on the mass of aqu/C(60) suspended. The sunlight-exposed Call's Creek samples exhibited the greatest increase in mass suspended with aqu/C(60) concentrations 17 times greater than those of the dark controls, followed by the humic acid treatments, 8.1 times, and deionized water, 3.4 times. Asymmetric flow field-flow fractionation indicated that aqu/C(60) nanoparticles in humic acid were the smallest and their mass was evenly distributed in the 120-300 nm hydrodynamic diameter (D(h)) size range, whereas aqu/C(60) nanoparticles in Call's Creek water were the largest and were evenly distributed in the size range of 200-300 nm D(h). Aqu/C(60) in deionized water and humic acid treatments exposed to sunlight exhibited a trend of increasingly negative ζ potentials as suspension time increased; however, this trend was not observed for the Call's Creek treatment.
USEPA Office of Research and Development, National Exposure Research Laboratory, Athens, Georgia, USA.
Carl W
CW
Isaacson
Dermont C
DC
Bouchard
D002853:Chromatography, Liquid; D037741:Fullerenes / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D013058:Mass Spectrometry; D010316:Particle Size; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D037741:Fullerenes; D006812:Humic Substances; D014874:Water Pollutants, Chemical; C069837:fullerene C60