posted on 2022-01-13, 15:11authored byLei Shi, Longbing He, Lei Shangguan, Yilong Zhou, Binjie Wang, Lei Zhang, Yufeng Yang, Chunyu Teng, Litao Sun
Gas-phase
synthesized binary nanoparticles (NPs) possess ultraclean
surfaces, which benefit versatile uses in sensors and catalysts. However,
precise control of their configuration and properties is still a big
challenge because the growth mechanism and phase evolution dynamics
in these NPs are very hard to unveil. Here, we report a strategy to
investigate the phase evolution dynamics in binary NPs by using e-beam
assisted ultrafast local heating and cooling inside a transmission
electron microscope. With this strategy, the phase segregation and
corresponding shape evolution of PbBi NPs are in situ revealed. It is found that the as-prepared PbBi alloy NPs will transform
into heterostructures under e-beam stimulated structural relaxation,
leading to the formation of featured Janus configurations with faceted
Bi polyhedron parts and intermetallic hemisphere parts. During phase
segregation, Pb1Bi1 and Pb7Bi3 phases are captured and identified, and a model of phase
and shape evolution of PbBi nanoalloys is developed and contrasted
with that of their bulk counterparts. These findings benefit the understanding
of the phase dynamics of binary NPs and can provide in-depth information
for engineering their structures for practical applications.