Institute of Nanotechnology, CNR-NANOTEC, via Orabona 4, 70126 Bari, Italy.
Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, Western Australia 6009, Australia.
Nat Mater. 2016 Sep;15(9):995-1002. doi: 10.1038/nmat4705. Epub 2016 Jul 25.
Gallium (Ga), a group III metal, is of fundamental interest due to its polymorphism and unusual phase transition behaviours. New solid phases have been observed when Ga is confined at the nanoscale. Herein, we demonstrate the stable coexistence, from 180 K to 800 K, of the unexpected solid γ-phase core and a liquid shell in substrate-supported Ga nanoparticles. We show that the support plays a fundamental role in determining Ga nanoparticle phases, with the driving forces for the nucleation of the γ-phase being the Laplace pressure in the nanoparticles and the epitaxial relationship of this phase to the substrate. We exploit the change in the amplitude of the evolving surface plasmon resonance of Ga nanoparticle ensembles during synthesis to reveal in real time the solid core formation in the liquid Ga nanoparticle. Finally, we provide a general framework for understanding how nanoscale confinement, interfacial and surface energies, and crystalline relationships to the substrate enable and stabilize the coexistence of unexpected phases.
镓（Ga）是一种 III 族金属，由于其多晶型性和异常的相变行为而具有重要的研究意义。当 Ga 在纳米尺度下被限制时，会观察到新的固态相。在此，我们证明了在基底支撑的 Ga 纳米颗粒中，出乎意料的固态 γ 相核和液态壳可以稳定共存，温度范围为 180K 至 800K。我们表明，支撑物在确定 Ga 纳米颗粒的相方面起着至关重要的作用，γ 相形核的驱动力是纳米颗粒中的拉普拉斯压力以及该相与基底的外延关系。我们利用 Ga 纳米颗粒体系在合成过程中表面等离子体共振的幅度变化，实时揭示液态 Ga 纳米颗粒中固态核的形成。最后，我们提供了一个通用框架，用于理解纳米尺度限制、界面和表面能以及与基底的晶体关系如何使意外相的共存成为可能并稳定下来。
