In Situ Probing the Kinetics of Gold Nanoparticle Thermal Sintering in Liquids: Implications for Ink-Jet Printing

Understanding the sintering kinetics of nanoparticles is important for their applications, such as printable nanoinks and wearable devices. However, it is challenging to in situ study the sintering process at nanoscale in a liquid environment. In this work, in situ investigation of the thermal sintering of gold nanoparticles is performed using liquid cell transmission electron microscopy. We have observed the unique sintering process of two nanoparticles in the liquid phase. By heating the gold nanoparticle solution in a liquid cell, a neck formed between the two nanoparticles at the initial sintering stage, followed by a rapid increase of neck size accompanied by a more rounded surface, and finally, the as-formed gold dimer shrank to a short nanorod. The sintering observations are dominated by two different surface diffusion paths and grain boundary diffusion. Furthermore, the high surface energy of small nanoparticles results in a higher shrinkage ratio in sintering. This insight of the kinetics of nanoparticle sintering provided by in situ characterization offers guidance for the future applications such as ink-jet printing.