Direct Observation of Growth and Self-assembly of Pt Nanoclusters in Water with the Aid of a Triblock Polymer Using in situ Liquid Cell Transmission Electron Microscopy (TEM)

摘要

Triblock copolymers are playing important roles in nanomaterial synthesis,and the nanomaterial forming mechanisms need to be studied in detail.In situ liquid cell transmission electron microscopy (TEM) is a powerful tool for real time observation of the dynamic growth behavior of nanomaterials in liquid with high resolution,and could be used for the above task.Here we report the observation of the growth and self-assembly of Pt nanoclusters with the aid of an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer (PEO-PPO-PEO) F 127 using in situ liquid cell TEM,with the nanocluster growth and formation procedures being tracked.Nano objects were seen to appear,drift and rotate with time,and then form into certain shaped nanoclusters under the electron beam irradiation.Further interestingly,in the thicker liquid layer region,the nanoclusters appeared to be fluffy,with average size keeping increase with time,while in the thinner region,the clusters were thinner,and got densified with time.The difference in precursor availability due to liquid layer thickness and charging effects is attributed to such a phenomenon.