The hollow cavities of nanotubes serve as templates for the growth of size- and shape-confined functional nanostructures, giving rise to novel materials and properties. In this work, considering their potential application as MRI contrast agents, gadolinium halides are encapsulated within the hollow cavities of WS2 nanotubes by capillary filling to obtain GdX3@WS2 nanotubes (where X = Cl, Br or I and @ means encapsulated in). Aberration corrected scanning/transmission electron microscopy (S/TEM) and spectroscopy is employed to understand the morphology and composition of the GdI3@WS2 nanotubes. The three dimensional morphology is studied with STEM tomography but understanding the compositional information is non-trivial due to the presence of multiple high atomic number elements. Therefore, energy dispersive X-ray spectroscopy (EDS) tomography was employed revealing the three dimensional chemical composition. Molecular dynamics simulations of the filling procedure shed light into the mechanics behind the formation of the confined gadolinium halide crystals. The quasi-1D system employed here serves as an example of a TEM-based chemical nanotomography method that could be extended to other materials, including beam-sensitive soft materials.

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Misfit-layered compounds (MLCs) are formed by the combination of different lattices and exhibit intriguing structural and morphological characteristics. MLC Sr x La1− x S–TaS2 nanotubes with varying Sr composition (10, 20, 40, and 60 Sr atom %, corresponding to x = 0.1, 0.2, 0.4 and 0.6, respectively) were prepared in the present study and systematically investigated using a combination of high-resolution electron microscopy and spectroscopy. These studies enable detailed insight into the structural aspects of these phases to be gained at the atomic scale. The addition of Sr had a significant impact on the formation of the nanotubes with higher Sr content, leading to a decrease in the yield of the nanotubes. This trend can be attributed to the reduced charge transfer between the rare earth/S unit (La x Sr1− x S) and the TaS2 layer in the MLC which destabilizes the MLC lattice. The influence of varying the Sr content in the nanotubes was systematically studied using Raman spectroscopy. Density functional theory calculations were carried out to support the experimental observations.

The hollow interiors of nanotubes could host the growth or filling of foreign elements/compounds to obtain hetero‐structures. The growth of these materials in the confined one dimensional space lead to novel properties. Capillary filling serves as a method to enable filling of carbon nanotubes and inorganic nanotubes including those of BN and WS 2 . 1, 2 In this work, considering the biocompatibility of WS 2 and paramagnetic property of gadolinium (III) compounds, capillary filling is employed to obtain GdX 3 @WS 2 nanotubes (X=Cl, Br, I). The precise determination of the structure and composition is detrimental in its further application. Thus in the present study the morphology, structure and chemical composition of the synthesized GdI 3 filled WS 2 is investigated using aberration corrected scanning/transmission electron microscopy and associated spectroscopic techniques (EELS and EDS). The three‐dimensional morphology is investigated using HAADF‐STEM tomography but obtaining three dimensional composition information is non‐trivial due to the presence of multiple high atomic number elements. Therefore, EDS‐STEM tomography is employed in the present study to map the chemical composition in three dimensions. 3 In order to reduce the beam induced effects on the specimen, tomography experiments were carried out at 80 kV in the present case. In view of the long duration of electron beam exposure necessary to perform EDS‐STEM tomography, additional electron irradiation studies were carried out to optimize the EDS‐STEM tomography conditions.