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At the first co-precipitation stage, with urea as precipitator, the nanosheet was formed by self-assembly due to the synergistic effect between surfactant (sodium dodecyl sulfate, SDS) and inorganic cobalt salt. During the following hydrothermal process, the nanosheet gradually curled into nanotube, which was cobalt compound nanotube with porous and multilayered structure. [Display omitted] • A two-step way for preparing one-dimensional cobalt compound nanotubes was successfully exploited. • The synthesis conditions for the cobalt compound nanotubes were thoroughly investigated. • The formation process of cobalt compound nanotube involves the self-assembly of nanosheets and sheets curling into nanotubes. • The cobalt compound nanotubes with porous and multilayered structure show great pseudo capacitance performance in CV test. Under the synergistic effect between surfactant (sodium dodecyl sulfate, SDS) and inorganic cobalt salt, the ultra-thin nanosheets were firstly formed by self-assembly with urea as precipitant. In the following hydrothermal treatment, these sheets gradually curled into tubes, and finally the cobalt compound nanotube with porous and multilayered structure was obtained. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier infrared transform spectroscopy (FT-IR), N 2 sorption and thermogravimetric analysis (TGA) were employed to characterize the samples, and the results showed that the cobalt compound with layered and tubular nanostructure could be obtained by adjusting the SDS concentration, solvent, hydrothermal time and temperature. The cobalt compound nanotube with multilayered and porous structure has high specific surface area, which provides great high efficiency for electron-transfer and results in high pseudo capacitance in cyclic voltammetry tests. [ABSTRACT FROM AUTHOR]

The magnetic and structural parameters of the well-characterized cobalt(II) compound Co 3 (OH) 2 (C 4 O 4 ) 2 ·3H 2 O ( 2 , 3 ) change significantly when the compound is mechanically ground. These parameters are also dependent on the storage conditions of the polycrystalline material before grinding. When the material is stored in an anhydrous (desiccators) environment ( 2 ), the structural properties of the ground sample ( 4 ) agree with the polycrystalline material although the magnetic properties differ somewhat. When storing the material under ambient conditions ( 3 ), the material undergoes a structural transformation after grinding ( 5 ) that is accompanied by changes in magnetic properties. The synthetic precursor ( 1 ) to 2 and 3 also shows magnetic properties that are not observed in 2 , 3 . The powder XRD of 1 suggests that the dominant species in the mixture is Co(C 4 O 4 )(H 2 O) 2 , which provides a new synthetic pathway for 2 and 3 . The synthesis of 1 was performed unprotected from the atmosphere, and therefore the room temperature effective magnetic moment of 1 was well below the other materials studied. The room temperature effective magnetic moment of 1 , 4 , and 5 (per cobalt center) are 4.0, 5.1, and 5.0 μ B . Dynamic magnetic susceptibility of 1 , 4 , and 5 confirm that 1 and the ground derivatives 4 and 5 are not isostructural with the polycrystalline materials. The dynamic susceptibility of 1 is too complex to analyze quantitatively. It contains two peaks and two shoulders that are within 11 K of one another, and a peak at 14 K dominates the rest of the features. 4 and 5 have features that can be analyzed and compared with 2 , 3 . The frequency independent out-of-phase peak associated with 2 , 3 becomes frequency dependent in 4 . The Arrhenius fit to the frequency dependence suggests spin-glass behavior based on the small pre-exponential time of 9.59 × 10 12 s and the physically unreasonable activation barrier of 99 K, which is well above the activation barrier observed for known single-chain magnets. A second frequency-dependent out-of-phase peak is observed for 4 and 5 at 11 K that is not present in 2 , 3 . This peak is analyzed with the Vogel–Fulcher function, and is attributed to cluster spin-glass interactions. [ABSTRACT FROM AUTHOR]