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Imaging transient melting of a nanocrystal using an X-ray laser

Clark, JN; Beitra, L; Xiong, G; Fritz, DM; Lemke, HT; Zhu, D; Chollet, M; ... Robinson, IK; + view all (2015) Imaging transient melting of a nanocrystal using an X-ray laser. Proceedings of the National Academy of Sciences of the United States of America , 112 (24) pp. 7444-7448. 10.1073/pnas.1417678112. Green open access

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Abstract

There is a fundamental interest in studying photoinduced dynamics in nanoparticles and nanostructures as it provides insight into their mechanical and thermal properties out of equilibrium and during phase transitions. Nanoparticles can display significantly different properties from the bulk, which is due to the interplay between their size, morphology, crystallinity, defect concentration, and surface properties. Particularly interesting scenarios arise when nanoparticles undergo phase transitions, such as melting induced by an optical laser. Current theoretical evidence suggests that nanoparticles can undergo reversible nonhomogenous melting with the formation of a core-shell structure consisting of a liquid outer layer. To date, studies from ensembles of nanoparticles have tentatively suggested that such mechanisms are present. Here we demonstrate imaging transient melting and softening of the acoustic phonon modes of an individual gold nanocrystal, using an X-ray free electron laser. The results demonstrate that the transient melting is reversible and nonhomogenous, consistent with a core-shell model of melting. The results have implications for understanding transient processes in nanoparticles and determining their elastic properties as they undergo phase transitions.

Type: Article
Title: Imaging transient melting of a nanocrystal using an X-ray laser
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1073/pnas.1417678112
Publisher version: http://dx.doi.org/10.1073/pnas.1417678112
Language: English
Keywords: X-ray laser, coherent diffraction, phase transition, pump-probe, ultrafast imaging
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/1487278
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