title: Rationally designed ligands that inhibit the aggregation of large gold nanoparticles in solution.
abstract: Hexadecanethiol (n-C16), 2,2-dimethylhexadecane-1-thiol (DMC16), and the multidentate thiol-based ligands 2-tetradecylpropane-1,3-dithiol (C16C2), 2-methyl-2-tetradecylpropane-1,3-dithiol (C16C3), and 1,1,1-tris(mercaptomethyl)pentadecane (t-C16) were evaluated for their ability to stabilize large gold nanoparticles (>15 nm) in organic solution. Citrate-stabilized gold nanoparticles (20-50 nm) treated with the ligands were extracted from aqueous solution and dispersed into toluene. The degree of aggregation of the gold nanoparticles was monitored visually and further confirmed by UV-vis spectroscopy and dynamic light scattering (DLS). The bidentate ligands (C16C2 and C16C3) and particularly the tridentate ligand (t-C16) showed enhanced abilities to inhibit the aggregation of large gold nanoparticles in organic solution. For gold nanoparticles modified with these multidentate ligands, bound thiolate (S2p3/2 binding energy of 162 eV) was the predominant sulfur species (>85%) as evaluated by X-ray photoelectron spectroscopy (XPS). Although an entropy-based resistance to ordering of the loosely packed surfactant layers was initially considered to be a plausible mechanism for the enhanced stabilization afforded by the multidentate ligands, when taken as a whole, the data presented here support a model in which the enhanced stabilization arises largely (if not solely) from the multidentate chelate effect.
authors: Departments of Chemistry and Chemical Engineering, University of Houston, 4800 Calhoun Road, Houston, Texas 77204-5003, USA.
authors: Shishan
authors: S
authors: Zhang
authors: Gyu
authors: G
authors: Leem
authors: La-Ongnuan
authors: LO
authors: Srisombat
authors: T Randall
authors: TR
authors: Lee
mesh_terms: D006046:Gold; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D012995:Solubility; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000737:chemistry
chemical_list: D008024:Ligands; D012996:Solutions; D013438:Sulfhydryl Compounds; D006046:Gold