Study of gold nanoparticle synthesis by synchrotron x-ray diffraction and fluorescence*

Gold nanoparticles have a wide range of potential applications, including therapeutic agent delivery, catalysis, and electronics. Recently a new process of hollow nanoparticle synthesis was reported, the mechanism of which was hypothesized to involve electroless deposition around electrochemically evolved hydrogen bubbles. However, the growth mechanism still needs experimental evidence. We report investigation of this synthesis process using synchrotron x-ray diffraction and fluorescence measurements performed at beamline 2-ID-D of the Advanced Photon Source (APS). A series of gold nanoparticle samples with different synthesis time (50-1200 seconds) were deposited using a mixture electrolyte solution of Na$_{\mathrm{3}}$Au(SO$_{\mathrm{3}})_{\mathrm{2}}$ and H$_{\mathrm{4}}$N$_{\mathrm{2}}$NiO$_{\mathrm{6}}$S$_{\mathrm{2}}$ on anodic aluminum oxide (AAO) membranes. The 2D mapping of fluorescence intensity and comparison of x-ray diffraction peaks of the samples have provided valuable information on the growth mechanism.