Real-Time Probing of the Synthesis of Colloidal Silver Nanocubes with Time-Resolved High-Energy Synchrotron X-ray Diffraction

Understanding of the nucleation and growth mechanism of colloidal nanoparticles is of key importance for better design and synthesis of nanomaterials with precisely tailored properties. Such mechanistic studies require in situ techniques that probe the complex chemical and physical events involved in the formation of nanoparticles in real time. Here, we report the use of high-energy synchrotron X-ray beam as a unique probe to monitor the nanophase evolution involved in the synthesis of colloidal Ag nanocubes. Time-resolved X-ray diffraction (XRD) reveals that at least three nucleation and growth processes occur sequentially: the formation of AgCl nanocrystals, the formation of multiple-twinned Ag nanocrystals, and the solid-phase transition of the AgCl nanocrystals to single-crystalline Ag ones. In addition, quantitative analysis of the XRD patterns advances the understanding of reaction kinetics involved in these nucleation and growth processes. This time-resolved in situ technique can be applied to a great variety of solution-phase reactions for the synthesis of colloidal nanoparticles.