In situ liquid cell TEM observation of solution-mediated interaction behaviour of Au/CdS nanoclusters

Abstract

Gold (Au)–cadmium sulfide (CdS) nanocomposites have attracted widespread attention for semiconductor-based photocatalysis applications. Understanding the dynamic behaviours of Au–CdS nanoclusters (NCs) in liquid solution is critical for fine control of the Au–CdS composite structure, and helps the design and development of future materials with improved catalytic properties. Here, we report the direct observation of the dynamic behaviours of Au and CdS NCs in water and in N,N-dimethylformamide (DMF) aqueous solution by in situ liquid cell transmission electron microscopy (LC-TEM). Electron beam induced liquid motion/bubble formation is found to be effective in guiding the NCs’ motion and interaction behaviours. The Au and CdS NCs combined better with each other in the DMF aqueous solution than in pure water. Around a thicker DMF solution region, liquid droplets keep growing, and show an overlap-like phenomenon in the TEM images due to their 3-D morphologies. The proceeding liquid solution front can further facilitate the lighter CdS to dynamically approach and connect with the heavier Au NCs. On the other hand, in the thinner DMF solution regions, electron beam irradiation not only caused bubble formation and growth, but also induced dissolution of the CdS in the composite. These results can provide in-depth understanding of nanoscale liquid–solid interactions for the development of future semiconductor–metal composite structures.