Optical Spectra and Morphology of Photochemically Produced Ag/Au Bimetallic Clusters
The Ag-Au alloy and core-shell bimetallic nanoparticles (BMNP) in colloids can be successfully prepared by photoinduced reduction of corresponding salts in the presence of SiO2/BPads (silica film with adsorbed Benzophenone) photocatalyst in water-IPA solution as a source of ketyl radicals and BP anionradicals as the reductive agents, and CTAB as a stabilizer. Generation of BMNP during the photochemical process happens right away of UV-irradiation. The ageing of bimetallic colloids related with formation and stabilization of the alloy-to-core-shell structure occurs with time (from hours to days) and depends on the order of metal ions photoreduction, viz simultaneous or successive UV irradiation of silver and gold ions in solution, and varying of Ag/Au mole ratio. Ageing of photoproduced colloid nanocomposites accompanied by the change of structure from alloy to core-shell what is proved with UV-vis absorption spectra. Optical spectra demonstrate formation of core-shell structures, where the shell is enriched with the core atoms. For now, first conclusion should be that BMNP Ag:Au 1:1 in colloids are formed mainly with Au NP’s in the shell. Photochemically produced and stabilized within pores of silica film Ag/Au BMNPs are formed as separate Ag and Au NP’s, together with the big aggregates.
KeywordsPhotoinduced reduction silver gold bimetallic nanoparticles core-shell alloy UV-spectra TEM SEM
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