The formation of small metallic particles has been intensively investigated in the last few decades because of the unique properties that they exhibit on the nanometer scale. A handful of reliable and straightforward synthetic procedures are used routinely for their manufacture. The most widely applied procedures are variations of the Turkevich–Frens citrate reduction route that allow the manufacture of water–soluble, relatively monodisperse particles in the c.a. 5 to 50 nm range, or the Brust–Shiffrin method that leads, after reduction of a gold precursor in a two phases liquid/liquid system, to the formation of hydrophobic nanoparticles in the c.a. 3 to 8 nm. However, the controlled manufacture of well–defined water–soluble particles in the sub 5 nm scale is still challenging, and most of the reported methods for their preparation involve multip–step preparation or cumbersome size separation procedure, adding costly and time consuming stages to the synthesis. Thus, a simple, robust protocol for the gramscale preparation of uniform colloidal gold below 5 nm is of broad practical value. Herein, the synthesis of near monodisperse gold nanoparticles using series of watersoluble polymeric ligands containing a thiol and/or a thioether is described. The size of the so–formed particles can be adjusted between one and five nanometres by varying the polymer/gold ratio and the colloidal suspensions are stable in aqueous conditions because of the nature of their polymeric protective monolayer. Those polymeric structures have been optimized to control the growth of the particles, leading to an unprecedented narrow size distribution. The near monodispersity of the particles, their stability in aqueous conditions, and their one–pot synthesis all make this method an attractive and versatile synthetic route. Furthermore, in extending the size–range tunability of some of those polymer stabilized gold nanoparticles to the sub 2 nm range, a transition between non–fluorescent and fluorescent nanoparticles is observed. This photophysical property is clearly size–dependant and fluorescence switching is detected for polymer-stabilized gold clusters below 1.7 nm in size. Detailed characterization indicates that the most fluorescent nanomaterial has a 3% quantum yield and is related to the presence of 1.1 nm gold core and a 6.9 nm hydrodynamic radius gold clusters and is not due to a polymer effect, or to the formation of a gold(I) complex.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:530932 |
| Date | January 2010 |
| Creators | Schaeffer, Nicolas |
| Contributors | Cooper, Andrew I. ; Levy, Raphael |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/1355/ |
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