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, Pb 1 Bi 1 and Pb 7 Bi 3 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.

Manipulation of nano-objects is fascinating as it not only facilitates the understanding of the essential properties of nanomaterials but also enlightens the design of future nano-devices beyond current micro-electromechanical systems. In this paper, a piston-cylinder-configured nano-motor prototype is designed and fabricated, in which nanometer-sized Te segments are electrically controlled to reciprocate inside the carbon cylinder serving as nanopistons. The nano-motor prototype has a length of ∼550 nm, an outer diameter of ∼150 nm, and a piston diameter of ∼30 nm. Electronwind and thermal expansion are two reciprocal forces that create a dynamic equilibrium on the Te pistons and enable the circulating motions. With bias control, a circulating rate of 0−4.3 counts per second has been achieved. This prototype is the smallest pistoncylinder-type nano-motor that has ever been reported and can provide new insights into investment casting-assisted nanoelectromechanical device fabrication.

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Binary metallic nanocrystals are attractive as they offer an extra degree of freedom for structure and phase modulation to generate synergistic effects and extraordinary properties. However, whether the binary structures...

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