The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs

Summary HRTEM and HAADF STEM of 1DTbBrx@SWCNT meta‐nanotubes reveal three structural modifications of 1D nanocrystals within single wall carbon nanotube channels attributed to a different stoichiometry of the guest crystal. For SWCNTs with diameters Dm > 1.4 nm a most complete tetragonal unit cell is observed. When crystallization occurs inside SWCNT with Dm < 1.4 nm 1D TbBrx crystal deforms a nanotube to elliptical shape in cross section. In this case the 1D crystal unit cell becomes monoclinic, with possible loss of a part of bromine atoms. Two modifications of a monoclinic unit cell appear. One of them is characterized by single or pair vacancies in the structure of the 1D crystal. Another structure is explained by peripheral and central bromine atoms loss. An appearance of such modifications can be stimulated by electron irradiation. The loss of bromine atoms is in agreement with chemical analysis data. Electronic properties of obtained meta‐nanotubes are investigated using optical absorption and Raman spectroscopy. It is shown that intercalation of terbium bromide into SWCNTs leads to acceptor doping of SWCNTs. According to local EDX analysis and elemental mapping this doping can arise from significant stoichiometry change in 1D nanocrystal indicating an average Tb:Br atomic ratio of 1:2.8 ± 0.1. Lay description The investigated nanocomposite is a 1D crystal of TbBrx salt, synthesized inside a single‐walled carbon nanotube (meta‐nanotube). The structure is studied by high resolution transmission electron microscopy (HRTEM) in bright‐field mode with spherical aberration corrector and HAADF scanning transmission electron microscopy with probe aberration corrector in a JEOL ARM 200F and a FEI Titan 80–300. Electron microscopy revealed a few structural modifications of 1D crystal depending on various bromine atoms content per unit cell. The existence of the structural variety for 1D TbBrx crystals as a part of meta‐nanotubes can be explained by a different oxidation degree of Tb atoms as well as by irradiation damage. The most complete structure is characterized by a tetrahedral unit cell. One‐dimensional crystal gradually loses bromine anions starting from pair vacancies up to the complete destruction of the structure. In this study a ball and stick model, computer models and image simulations for different stages of destruction are proposed. Five types of the structures are represented. A gradual decrease of Tb:Br ratio of atoms, that is a change in the