Size Dependent Properties of Hollow Gold Nanoparticles: A Theoretical Investigation

Abstract

A new kind of nanostructures with the negative curvature defined as the hollow ones have recently used in biomedical applications. In this work, an analytic model was developed to compute the size-dependent properties of spherical hollow gold nanoparticles in shell-core-shell configuration. This model has established to calculate the cohesive energies based on the surface energy consideration depending on sizes of inner and outer surfaces of hollow nanoparticles. The size and geometry of the model particles have been obtained by using the stability diagram and the collapsing mechanism was studied by molecular dynamics simulations. The model has been also applied to the hollow particles within unstable and half stable geometry. The predicted results have been compared with each other and those obtained by solid ones. The theoretically predicted size dependent properties are consistent with experimental observations and the hollow quantum dot calculations. Thus, an atomistic insight into the size effect on the cohesive energies of hollow nanoparticles has been presented.

Understanding the Stability of Hollow Nanoparticles with Polycrystalline Shells

“…To understand how the polycrystalline shell affects the structural stability, we can note that the grain boundary structure is often a route of hardening for polycrystalline systems. , However, at smaller grain sizes ( d ≤ 10 nm), the grain boundary acts as stress accumulation sites, favoring dislocations, and the fault mechanism associated. We note that our results are quite different from those observed in the literature. ,, For single-crystal Au hNPs, it is noticed that a shell thickness of a few lattice parameters is necessary to stabilize hNPs. In experiments, the obtained thicknesses of Au hNPs are far from those sizes, ,, suggesting that the preexistence of defects or grain boundaries might introduce an alternative mechanism for hNP instability and collapse.…”

“…The stability of polycrystalline Au hNPs was investigated through MD simulations. While shell thickness and radius are commonly referenced as the relevant parameters to characterize hNPs, ,,,,− the presented simulations allow us to conclude that the grain boundary structure also plays a dominant role in their structural stability. In particular, it was found an inverse dependence on the stable/half-stable transition with the grain size reduction.…”

“…We note that our results are quite different from those observed in the literature. 24,28,29 For single-crystal Au hNPs, it is noticed that a shell thickness of a few lattice parameters is necessary to stabilize hNPs. In experiments, the obtained thicknesses of Au hNPs are far from those sizes, 38,57,58 suggesting that the preexistence of defects or grain boundaries might introduce an alternative mechanism for hNP instability and collapse.…”

“…We note that to obtain ultrathin hNPs, several methods and post-synthesis techniques have been conducted. ,,, The minimum shell thicknesses reported by experiments − are often larger than those reported from MD simulations ,, of single-crystal hNPs; however, MD predicts thickness of a few lattice parameters, with a well-defined failure mechanism . The major differences would be on the preexistence of defects, which are commonly observed during the synthesis process.…”

“…To the best of our knowledge, all the available atomistic studies of thermal and mechanical stability ,,− consider single-crystal hNPs, something difficult to obtain under realistic experimental conditions. In fact, for single-crystal hNPs, the failure is triggered by the slips of preferential planes due to surface stresses, , in the absence of other plasticity sources, and the stability of pristine samples can be idealized.…”