Developments of cation-exchange by in situ electron microscopy

Figures & data

Figure 1. (a) Tip of an in situ heating furnace-based holder. The dark ring is the furnace, and the hole at its center is the slot where the TEM grid should be inserted and clamped; (b) Graphical representation of a typical heating MEMS. Panels with increasing magnification are used to highlight the position of the small electron-transparent zones. Adapted with permission from [7].

Figure 2. (a, b) Au-decorated CdSe nanorods before (a) and after (b) thermal annealing; (c-f) Isolated and interconnected Au-decorated CdSe nanorods before (c, e) and after (d, f) thermal annealing. CdSe nanorods are connected through Au domains located at the nanorods’ tips; (g, h) CdSe nanorods and Au nanocrystals before (g) and after (h) thermal annealing. After annealing, new Au domains formed at the tip of the CdSe nanorods. Reprinted with permission from [28]. Copyright [2010] American Chemical Society.

Figure 3. Motion and coalescence of Au domains on CdSe nanorods during annealing between 170 and 190ºC. White arrows (a-c) indicate the cluster diffusion and coalescence of two Au domains, black arrows (d) indicate the presence of flat Au/CdSe interfaces at the tip of the nanorods after annealing. Reprinted with permission from [28]. Copyright [2010] American Chemical Society.

Figure 4. Figure 4 (a) ZL image and corresponding EFTEM map (inset) of Janus-like Cu-Cu₃P nanoparticles. The presence of Cu and P in the EFTEM map are indicated in red and green, respectively; (b,c) HRTEM images of Janus-like Cu-Cu₃P nanoparticles characterized by two different epitaxial relationships between the Cu and Cu₃P domains. Adapted with permission from [29]. Copyright [2012] American Chemical Society.

Figure 5. Effects of thermal annealing on the Janus-like nanoparticles. (a) Image of a group of nanoparticles recorded at 450ºC. Dark grey domains indicate the presence of Cu, lighter grey domains are constituted by Cu₃P; (b) Image of the same group of nanoparticles after 10 min of annealing at 500ºC. No difference in tone indicating the presence of different domains can be observed; (c) HRTEM image of a Janus-like Cu-Cu₃P nanoparticle annealed at 150ºC, with both domains exhibiting fcc crystal structure. Reprinted with permission from [29]. Copyright [2012] American Chemical Society.

Figure 6. (a) HRTEM image of packed CdSe/Cu₃P/CdSe nano-sandwiches. The [0001] stacking of Cu₃P and CdSe (individuated by the variation in electron contrast) is clearly visible; (b) EDS line profile over a HAADF-STEM image of a single nano-sandwich, showing the elemental distribution across its width; (c) HRTEM image showing the epitaxial relationship between CdSe and Cu₃P at the interface of the nano-sandwich; (d) 2D-FFT patterns of the sole Cu₃P and CdSe phases (labeled in red and blue, respectively) and of both phases. The combined FFT pattern highlights the structural correspondence between phases.   Reprinted with permission from [30]. Copyright [2013] American Chemical Society.

Figure 7. HRTEM images showing the thermal evolution of a single CdSe/Cu₃P/CdSe nano-sandwich upon thermal annealing. (a) The initial structure is maintained from RT to 300ºC; (b) at 350ºC the CdSe cannot be observed anymore in the lateral domains and is substituted by Cu₂Se domains; (c) at 400ºC even Cu₃P cannot be observed anymore in the central domain and the sole Cu₂Se phase can be observed in the newly formed single crystal. Scale bars correspond to 5 nm. Reprinted with permission from [30]. Copyright [2013] American Chemical Society.

Figure 8. ZL images and EFTEM elemental maps of a group of nano-sandwiches recorded during a thermal annealing from RT to 400ºC and showing the progressive disappearance of P and Cd and the concomitant expansion of Cu. Scale bars correspond to 100 nm. Reprinted with permission from [30]. Copyright [2013] American Chemical Society.

Figure 9. (a, b) HRTEM images of a single Cu₂Se nanoparticle at RT (a) and after thermal annealing (b). The slight variation observed in d-spacing indicates the lattice shrinking caused by thermal-activated release of Cu atoms; (c) integrated ED patterns of a Cu₂Se nanoparticles at RT (magenta) and after thermal annealing (orange). The upward shift of the diffraction peaks confirms the lattice shrinking caused by the partial Cu depletion; (d) STEM image showing a group of Cu_2-xSe nanoparticles. The blue rectangle indicates the area investigated by HREELS; (e, f) HREEL spectra of the area indicated in (d). No features can be observed in the spectrum recorded at RT (e), while a low-energy peak caused by a low-energy plasmon appears in the spectrum recorded after annealing; (g) DFT simulation of HREEL spectra of stoichiometric (black) and depleted (red) Cu₂Se nanoparticles. The red (depleted) spectrum features a peak at the same energy as the experimental peak observed after annealing (f). Reprinted with permission from [31]. Copyright [2016] American Chemical Society.

Figure 10. (a-d) HAADF-STEM images and EFTEM maps of Cu₂Se nanospheres and CdSe nanorods at RT (a, b) and after annealing at 400ºC (c, d). Cu and Cd are indicated in green and red, respectively; (e) HRTEM image and corresponding 2D-FFT pattern of a representative hcp CdSe nanorod at RT; (f) HRTEM image and corresponding 2D-FFT pattern of the same nanorod after annealing to 400ºC. Its length is slightly diminished and its crystal structure has changed to fcc. Adapted with permission from [31]. Copyright [2016] American Chemical Society.

Figure 11. ZL images, corresponding EFTEM elemental maps (Cu and Cd are indicated in green and red, respectively) and HRTEM images of Cu_2−xSe nanoparticles and CdSe nanowires recorded at RT (a-c), 350ºC (d-f) and after annealing to 400ºC (g-i). No variation can be observed in the ZL images (a, d, g), while the diffusion of Cu and the ongoing Cu-to-Cd CE are evident from EFTEM maps (b, e, h). HRTEM images of a CdSe nanowire show its structural evolution from a hcp structure (c, RT) to a defective ((f), 350ºC) and well-defined fcc structure ((i), 400ºC). Reprinted with permission from [31]. Copyright [2016] American Chemical Society.

Casu A, Sogne E, Genovese A, et al. The new youth of the in situ transmission electron microscopy. In: Stanciu SG, editor. Microscopy and analysis. ISBN 978-953-51-2579-2, InTech Editions; 2016. DOI:10.5772/63269

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