Photoinduced self-assembly of Au-Ag-Hg trimetallic nanoparticles during their synthesis from gold seeds in glycine solution.

This paper describes how irradiation with light influences the preparation of Au-Ag-Hg trimetallic nanoparticles (NPs) from gold nanorods (AuNRs) in glycine solutions (pH 8.5-10.5). Silver, gold, and mercury ions were reduced by ascorbic acid and deposited on AuNRs to form Au-Ag-Hg trimetallic NPs of different sizes and shapes. In addition to the amounts of ascorbic acid, Au seeds, and glycine, others parameters such as pH, irradiation, and the concentrations of Ag, Au, and Hg ions are important for the preparation of these Au-Ag-Hg trimetallic NPs. Transmission electron and dark-field microscopy images indicated that irradiation with light induced the self-assembly of the thus-prepared Au-Ag-Hg trimetallic NPs, in addition to slightly affecting their shapes, but suggested no photoreduction effect during their formation. At pH 10.5, the Au-Ag-Hg trimetallic NPs possessed dumbbell- and millet-like shapes, having the sizes of 51 +/- 3 and 48 +/- 4 nm, respectively, when synthesized in the dark and under illumination, respectively. Time-evolution UV-Vis extinction spectroscopy and inductively coupled plasma mass spectrometry data obtained from solutions at various periods during the formation of the Au-Ag-Hg trimetallic NPs reveal that reduction of the Au and Ag ions occurred prior to reduction of the Hg ions. To the best of our knowledge, this study presents the first example of the light-induced self-assembly of Au-Ag-Hg trimetallic NPs in a liquid phase.