The strain effect on graphene-encapsulated Au nanoparticles is investigated. A finite-element calculation is performed to simulate the strain distribution and morphology of the monolayer and multilayer graphene-encapsulated Au nanoparticles, respectively. It can be found that the inhomogeneous strain and deformation are enhanced with the increasing shrinkage of the graphene shell. Moreover, the strain distribution and deformation are very sensitive to the layer number of the graphene shell. Especially, the inhomogeneous strain at the interface between the graphene shell and encapsulated Au nanoparticles is strongly tuned by the graphene thickness. For the mono- and bilayer graphene-encapsulated Au nanoparticles, the dramatic shape transformation can be observed. However, with increasing the graphene thickness further, there is hardly deformation for the encapsulated Au nanoparticles. These simulated results indicate that the strain and deformation can be designed by the graphene layer thickness, which provides an opportunity to engineer the structure and morphology of the graphene-encapsulated nanoparticles. 1. Introduction Metal nanoparticles have extensive technological applications in nanosensors, catalysis, and biomedical engineering [1–3]. The high surface-to-volume ratio, however, makes the naked metal nanoparticles sensitive to the ambient atmosphere and unstable. Therefore, encapsulated metal nanoparticles have attracted increasing attention as an alternative to the naked metal nanoparticles. It has been demonstrated that it is an efficient method to prevent the oxidation of the metal nanoparticles by encapsulating them with graphene shell [4, 5]. Moreover, the properties of the encapsulated nanoparticles can be significantly modified by the graphene shell due to the unique electronic, optical, and mechanical properties of graphene [6, 7]. Recently, there is a great interest in the preparation and investigation of the graphene-encapsulated nanoparticles. The high performance of the graphene-encapsulated nanoparticles has a promising potential application [8]. On the other hand, graphene-encapsulated nanoparticles can be compared to the core/shell nanostructures. The properties of this core/shell nanostructure strongly depend on the interplay between the core and shell layer [9, 10]. Especially, the atomic structure and morphology of the core and shell can be tailored. For example, the graphene shell has been illustrated to be used as compression cell to induce the transformation and reconstruction of the encapsulated nanoparticles by electron or
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