Gold nanoparticles generated by thermolysis of all-in-one gold(I) carboxylate complexes

Consecutive synthesis methodologies for the preparation of the gold(I) carboxylates [(Ph3P)-AuO2CCH2(OCH2CH2)(n)OCH3] (n = 0-6) (6a-g) are reported, whereby selective mono-alkylation of diols HO(CH2CH2O)(n)H (n = 0-6), Williamson ether synthesis and metal carboxylate (Ag, Au) formation are the key steps. Single crystal X-ray diffraction studies of 6a (n = 0) and 6b (n = 1) were carried out showing that the P-Au-O unit is essentially linear. These compounds were applied in the formation of gold nanoparticles (NP) by a thermally induced decomposition process and hence the addition of any further stabilizing and reducing reagents, respectively, is not required. The ethylene glycol functionalities, providing multiple donating capabilities, are able to stabilise the encapsulated gold colloids. The dependency of concentration, generation time and ethylene glycol chain lengths on the NP size and size distribution is discussed. Characterisation of the gold colloids was performed by TEM, UV/Vis spectroscopy and electron diffraction studies revealing that Au NP are formed with a size of 3.3 (+/- 0.6) to 6.5 (+/- 0.9) nm in p-xylene with a sharp size distribution. Additionally, a decomposition mechanism determined by TG-MS coupling experiments of the gold(I) precursors is reported showing that 1st decarboxylation occurs followed by the cleavage of the Au-PPh3 bond and finally release of ethylene glycol fragments to give Au-NP and the appropriate organics.