Impacts that pH and metal ion concentration have on the synthesis of bimetallic and trimetallic nanorods from gold seeds

This paper describes the synthesis of Au-Ag bimetallic and Au-Ag-Hg trimetallic nanorods (NRs) from gold NRs, which acted as seeds, under alkaline conditions ( pH >= 8.0) and in the presence of hexadecyltrimethylammonium bromide ( CTAB), ascorbic acid, and other metal ions. The Hg2+, Fe3+, and Co2+ ions are stable at pH >= 8.5 in the presence of 200 mM glycine; these conditions allow investigations into their roles during the syntheses of the NRs. We prepared a number of differently colored NRs by controlling the pH and the nature and concentration of the metal ion. Mercury ions, which have a higher reduction potential and form a more stable complex with glycine, are reduced and deposited on the gold NRs to form Au-Ag-Hg trimetallic NRs; we confirmed this situation by performing inductively coupled plasma-mass spectrometry and energy dispersive X-ray measurements. In addition, we have demonstrated that the size and shape of the Au-Ag-Hg trimetallic NRs can be tuned by controlling the Hg2+ concentration.