Brust synthesis

Two phase reduction (Brust synthesis) This method is usually employed to make organic soluble quantum clusters [8]. This method consists of two steps. The first is the transfer of AuCLi from aqueous to the organic layer by a phase transfer reagent such as tetraoctyl ammonium bromide (TOABr). The next step is the subsequent reduction of AuCU in the presence of suitably selected ligands such as thiols, phosphines, etc. 

M. Brust synthesis of thiol-stabilized gold nanoparticles... 

Brust M ef a/1994 Synthesis of thiol-derivatised gold nanopartioles in a two-phase liquid-liquid system J. Chem. Soc. Chem. Comm. 801... 

Brust, M., Walker, M., Bethell, D., Schiffrin, D.J. and Whyman, R. (1994) Synthesis of thiol-derivatized gold nanopartides in a 2-phase liquid—liquid system. Journal of the Chemical Society, Chemical Communications (7), 801—802. 

M. Brust, M. Walker, D. Bethell, D. J. Schiffrin, and R. Whyman, Synthesis of thiol-derivatised gold nanoparticles in a 2-phase liquid-liquid system, J. Chem. Soc.—Chem. Commun. 801-802 (1994). 

Brust M, Fink J, Bethell D, Schiffiin DJ, Kiely C. Synthesis and reactions of functionalized gold nanoparticles. J Chem Soc Chem Commun 1995 1655-1656. 

Figure3.9 Brust-Schiffrin method for the synthesis of monolayer protected gold clusters. Reproduced from reference [62] by permission of The Royal Society of Chemistry.

As mentioned above, the grafting to technique enables in a one-pot reaction the synthesis of Au NPs stabilized by sulfur-containing polymers, which bear functional groups such as dithioester, trithioester, thiol, thioether and disulfide at the end of a polymer chain or in the middle. This method leads to nanoparticles similar to those obtained by the Brust-Schiffrin method in which alkanethiol-protected Au NPs of small size are obtained. This grafting to technique leads to very stable nanomaterials that also present a high surface graft density of polymer brush on the Au NP surface. 

For example, Wuelfing et al. reported on the synthesis of Au NPs using the thiolated polymer, a-methoxy-co-mercapto-poly(ethylene glycol) (PEG-SH), as stabilizer in a modification of the Brust-Schiffrin method using a 1/12 polymer thiol/ AuC14 ratio. Transmission electron microscopy showed that the product had modestly polydisperse Au cores of average diameter 2.8 1 nm. This nanomaterial led to characteristics uniquely different from alkanethiolate MPCs, notably aqueous solubility, thermal and chemical stability, ligand footprint size, and ionic conductivity [66]. 

Scheme 1 The one- and two-phase Brust-Schiffrin method for the synthesis of thiol-capped gold nanoparticles, and the first step of the reaction prior to the reduction step with NaBIL [63]...

Figure 4.4 Schematic representation of the two phase AuNPs synthesis proposed by Brust and coworkers in 1994.134...

Brust, M. Walker, M. Bethel , D, Schiffrin, D. J, Whyman, R. Synthesis of Ttiol-Derivatised Gold Nanoparticles in a Two-Phase Liquid-Liquid System, J. Chem. See., Chem. Commun. 1994. 801-802,... 

Fig.1 a The Brust-Schiffrin solution phase gold nanoparticle synthesis, followed by b place exchange process developed by Murray... 

One year later, Brust and Schiffrin [28,29] published a method for AuNPs synthesis which has a considerable impact on the overall field in less than a decade because it allowed the facile synthesis of thermally stable and air-stable AuNPs of reduced dispersity and controlled size for the first time. In this method, the gold colloids are sterically stabilized by organic molecules having thiol, amide or acid groups in contrast to the citrate reduction method where the gold colloids are kinetically stabilized in aqueous solutions by an electrical double layer [28,29], The main advantage of the Brust method is that the gold particles behave in a way as chemical compounds. These AuNPs can be repeatedly isolated and... 

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