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

摘要

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 degrees 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.