In Situ Transmission Electron Microscopy of Cadmium Selenide Nanorod Sublimation

Abstract

In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. We propose a mechanism that accounts for the observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

Thermal Stability and Anisotropic Sublimation of Two-Dimensional Colloidal Bi2Te3 and Bi2Se3 Nanocrystals

“…Crystallographically anisotropic phase transitions involving melting and sublimation have been observed before 29,31,40,56−59 and are theoretically predicted by the Lindemann’s criterion. 60 This usually indicates anisotropy in the surface free energies of the different crystallographic planes.…”

Automated analysis of evolving interfaces during in situ electron microscopy

“…Production of radiolytic species by the electron beam, as described in Schneider et al [20], causes the Au nanorods to either grow or dissolve. During dissolution, we hypothesize that the radicals produced during water irradiation react with the CTAB, whose role is to stabilize the nanorods; in the absence of CTAB, nanorods are known to be unstable and dissolve [49,50]. Analysis of morphology and growth dynamics at specific facets provides information about the atomic level processes that control shape [51].…”

The New Youth of the In Situ Transmission Electron Microscopy

“…In fact, while colloidal synthesis is a well-known route to synthesize and fine-tune NPs with well-defined crystal structure, shape and size [29,30], in situ annealing TEM represents a useful tool not only to investigate (at atomic level and in real time) the properties and stability of promising nanomaterials [31][32][33][34][35][36][37] but also to trigger extensive modifications in nano-materials of technological interest.…”

“…In this context, the studies by Hellebusch et al [34] and Hudak et al [35] represent perfect examples of basic research of immediate applicative interest, since both present stability tests for materials that are already being used as building blocks in a vast range of applications. In particular, Hellebusch et al [34] investigated the in situ sublimation of CdSe NRs in order to understand if the sublimation could influence their facet stability and the possible role of surface ligands. While the sublimation was always anisotropic, a temperature-dependent effect was observed: the mass loss occurred either noncontinuously from both ends of the NRs at lower temperatures or continuously from one end at higher temperatures ( Figure 3A).…”