Inorganic chemistry in a nanoreactor: Au/TiO2 nanocomposites by photolysis of a single-source precursor in miniemulsion

Abstract

An original synthetic route, based on the combination of a single-source precursor, UV-photodegradation and inverse w/o miniemulsion, is used to prepare Au nanoparticles (NPs) dispersed on titania. The source of the nanocomposite materials is the photolabile single-source precursor AuCl4(NH4)7[Ti2(O2)2(cit)(Hcit)]2·12H2O, which is suspended in a w/o miniemulsion consisting of different surfactant/hydrocarbon/water formulations (surfactant: sodium dodecylsulfate (SDS) or Triton X-100) and subsequently irradiated with a UV lamp to promote its decomposition in the confined space of the droplets. Gold NPs that form at room temperature are found to be crystalline, while titanium dioxide occurs as an amorphous phase. Moreover, the average crystallite size of gold NPs ranges between 20 and 24 nm when using SDS and between 26 and 40 nm in the case of Triton X-100, after 4 and 8 hours of irradiation time, respectively. Scanning and transmission electron microscopies (SEM and TEM) are used to get information about the nanocomposite morphology and nanostructure, revealing that gold NPs are uniformly distributed on the titanium oxide surface. Furthermore, X-ray photoelectron spectroscopy (XPS) outcomes, besides confirming the formation of both metallic gold and titania, provide information about the high dispersion of Au NPs on the TiO2 surface. In fact, the Au : Ti atomic ratio is found to be 0.45-1.5 (1 : 2-1.5 : 1), which is higher than the value determined by starting from the precursor stoichiometry (0.25). Catalytic testing in the oxidation of 2-propanol shows that decomposition of the precursor in a miniemulsion provides a nanocomposite with enhanced activity compared to the decomposition in the aqueous phase.

Sustainable and Very-Low-Temperature Wet-Chemistry Routes for the Synthesis of Crystalline Inorganic Nanostructures

“…The nanoreactor concept can be also conveniently exploited to afford the controlled decomposition of tailored single-source to yield crystalline nanocomposites, for instance through decomposition processes triggered by light. An example in this framework is reported by our group [ 314 ]. The gold-containing titanium peroxo-complex AuCl 4 (NH 4 ) 7 [T i2 (O 2 ) 2 (Hcit) (cit)] 2 · 12H 2 O is a crystalline molecular single-source precursor of the composite Au/TiO 2 [ 315 ].…”

Gold-Based Nanoparticles on Amino-Functionalized Mesoporous Silica Supports as Nanozymes for Glucose Oxidation

“…Two minutes was allowed between the addition of THPC and that of chloroauric acid. The reaction mixture was stirred for 1 day at room temperature, protecting the mixture from light to prevent the photothermal decomposition of precursors [79]. Finally, the resulting colloid Au-NPs were stored in a refrigerator at 4 • C until further use.…”

Synthesis and characterization of new ferrocene, porphyrin and C60 triads, connected by triple bonds

“…Our results show that trinuclear copper(II) complexes are the major species observed in the range of 2:1 to 4:1 metal to ligand ratio. The Cu/ Aβ(1-16) dimer revealed a distinct Cu(II) coordination mode with respect to the Aβ (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) monomer. This finding may be of relevance considering the greater toxicity of lowmolecular-weight Aβ oligomers in AD.…”