title: Light-induced aggregation of colloidal gold nanoparticles capped by thymine derivatives.
abstract: The colloid stability of thymine-coated gold nanoparticles under light irradiation as a function of particle size, surface charge, and exposure time was investigated in alkaline, aqueous solutions as well as in a 0.5 vol % of DMF in H(2)O mixture. With increasing exposure to light irradiation at 280 nm, more and more particles coagulated. Light-induced aggregation of colloidal gold nanoparticles was attributed to reorientation of thymine terminal groups tethered on gold particle surfaces. A smaller particle size and negatively charged surface reduced the rate of photodimerization or even inhibited the photoreaction. UV-vis and FTIR spectroscopy confirmed the photodimerization of terminal thymine molecules under 280 nm light irradiation. The reaction kinetics of thymine photodimerization appears to be a combination of first-order reactions, each having different rates, reflecting the inhomogeneity and high curvature of the gold nanoparticle surfaces.
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, South Australia 5095.
authors.forename: Jingfang
authors.initials: J
authors.lastname: Zhou
authors.forename: Rossen
authors.initials: R
authors.lastname: Sedev
authors.forename: David
authors.initials: D
authors.lastname: Beattie
authors.forename: John
authors.initials: J
authors.lastname: Ralston
mesh_terms: D017979:Gold Colloid / Q000737:chemistry*; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D013053:Spectrophotometry; D013941:Thymine / Q000737:chemistry*
chemical_list: D017979:Gold Colloid; D013941:Thymine