An exclusive deposition method of silver nanoparticles on TiO2 particles via low-temperature decomposition of silver-alkyldiamine complexes in aqueous media

Abstract

An exclusive deposition method of Ag nanoparticles (NPs) on TiO₂ particles has been developed. Ag NPs supported on TiO₂ particles, Ag_x/TiO₂, with various Ag weight ratios versus total weights of Ag and TiO₂ between x = 2 and 16 wt% are prepared via low-temperature thermal decomposition of Ag(I)–alkyldiamine complexes generated by a reaction between AgNO₃ and N,N-dimethyl-1,3-propanediamine (dmpda) in an aqueous medium suspending TiO₂ particles. The thermal decomposition of the Ag(I)–alkyldiamine complexes is accelerated by TiO₂ particles in the dark, indicating that the reaction catalytically occurs on the TiO₂ surfaces. Under optimised reaction conditions, the thermal decomposition of the complex precursors is completed within 3 hours at 70 °C, and Ag NPs are almost exclusively deposited on TiO₂ particles with high conversion efficiencies (≥95%) of the precursor complexes. The thermal decomposition rates of the precursor complexes are strongly influenced by the chemical structure of a family of water-soluble dmpda analogues, and dmpda with both primary and tertiary amino groups is adopted as a suitable candidate for the exclusive deposition method. The number-averaged particle sizes of the Ag NPs are 6.4, 8.4, 11.8 and 15.2 nm in the cases of Ag_x/TiO₂, x = 2, 4, 8 and 16, respectively. To the best of our knowledge, the as-prepared Ag_x/TiO₂ samples show one of the highest catalytic abilities for the hydrogenation reduction of 4-nitrophenol into 4-aminophenol as a model reaction catalysed by Ag NPs.