title: A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions.
abstract: Reducing dilute aqueous HAuCl4 with sodium thiocyanate (NaSCN) under alkaline conditions produces 2 to 3 nm diameter nanoparticles. Stable grape-like oligomeric clusters of these yellow nanoparticles of narrow size distribution are synthesized under ambient conditions via two methods. The delay-time method controls the number of subunits in the oligoclusters by varying the time between the addition of HAuCl₄ to alkaline solution and the subsequent addition of reducing agent, NaSCN. The yellow oligoclusters produced range in size from ~3 to ~25 nm. This size range can be further extended by an add-on method utilizing hydroxylated gold chloride (Na(+)[Au(OH₄-x)Clx](-)) to auto-catalytically increase the number of subunits in the as-synthesized oligocluster nanoparticles, providing a total range of 3 nm to 70 nm. The crude oligocluster preparations display narrow size distributions and do not require further fractionation for most purposes. The oligoclusters formed can be concentrated >300 fold without aggregation and the crude reaction mixtures remain stable for weeks without further processing. Because these oligomeric clusters can be concentrated before derivatization they allow expensive derivatizing agents to be used economically. In addition, we present two models by which predictions of particle size can be made with great accuracy.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill; law4@email.unc.edu.
authors.forename: Marlon
authors.initials: M
authors.lastname: Lawrence
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill.
authors.forename: Anze
authors.initials: A
authors.lastname: Testen
authors.affiliation: Condensed Matter Physics Department, Laboratory of Biophysics, Jozef Stefan Institute; tilen.koklic@ijs.si.
authors.forename: Tilen
authors.initials: T
authors.lastname: Koklic
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill; oliver_smithies@med.unc.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Smithies
mesh_terms: D002384:Catalysis; D002712:Chlorides / Q000138:chemical synthesis*; D006046:Gold / Q000737:chemistry*; D017612:Gold Compounds / Q000138:chemical synthesis*; D053758:Nanoparticles; D010316:Particle Size; D012996:Solutions; D013861:Thiocyanates / Q000138:chemical synthesis*
chemical_list: D002712:Chlorides; D017612:Gold Compounds; D012996:Solutions; D013861:Thiocyanates; C024553:sodium thiocyanate; D006046:Gold; C024568:gold tetrachloride, acid