nanostructures of trigonal selenium (t-Se) were synthesized by the reduction of H 2 SeO 3 in different solvents with a sonochemical method. The 1D structure of t-Se was formed by the anisotropic growth of selenium crystalline, and the morphology of the products highly depends on the reaction conditions including ultrasonic mode (e.g., frequency, power, and time), aging time, and solvent. Single crystalline trigonal selenium nanotubes with diameters of less than 200 nm and nanowires with diameters of 20-50 nm have been synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive spectrometry (EDS), and Raman spectra were used to characterize the products. The formation process of t-Se nanotubes and nanowires were investigated. A sonication-induced directional growth mechanism was proposed for the formation of nanotubes. The further aging of tubes in solution leads to the collapse of the tubular structure and the formation of nanowires.

The formation of CdS nanotetrahedrons, pencil-shaped nanorods, tetrapods, prickly spheres, and high aspect-ratio hexagonal nanoprisms has been, respectively, achieved by adjusting the ratio of two solvents ethylenediamine and ethylene glycol under the solvothermal condition. None of the surfactants or other templates was needed in the process. The reaction time and temperature can be used as the additional means to control the size and morphology. By closely inspecting the growing process of the tetrapod structure and the crystallographic analysis of the products, we proposed that the lattice space match and the location match of ions at the interface of the zinc blende core and the wurtzite arms are two important structural factors to guide this furcate growth. Also, the anisotropic adsorption ability of ethylenediamine at the different surfaces of wurtzite CdS crystals results in the 1D growth of the arms. The possible growing mechanisms of CdS with other shapes were also discussed.

Hexagonal nickel‐organic framework (Ni‐MOF) [Ni(NO3)2·6H2O, 1,3,5‐benzenetricarboxylic acid, 4‐4′‐bipyridine] is fabricated through a one‐step solvothermal method. The {001} crystal plane is exposed to the largest hexagonal surface, which is an ideal structure for electron transport and ion diffusion. Compared with the surrounding rectangular crystal surface, the ion diffusion length through the {001} crystal plane is the shortest. In addition, the cross‐linked porous mesh structures growing on the {001} crystal plane strengthen the mixing with conductive carbon, inducing preferable conductivity, as well as increasing the area of ion contact and the number of active sites. These advantages enable the hexagonal Ni‐MOF to exhibit excellent electrochemical performance as supercapacitor electrode materials. In a three‐electrode cell, specific capacitance of hexagonal Ni‐MOF in the 3.0 m KOH electrolyte is 977.04 F g−1 and remains at the initial value of 92.34% after 5,000 cycles. When the hexagonal Ni‐MOF and activated carbon are assembled into aqueous devices, the electrochemical performance remains effective.

The ordered structures of nanomaterials have been attracting more and more attention recently due to their unusual physical properties. [1][2][3][4] There are mainly two routes to fabricate such structures. One method is preparing nanomaterials and then organizing them. 5 The two-and three-dimensional ordered structures of CdSe, 6 Ag 2 S, 7 Au, 8 Ag, 4,9 Pd, 10 and Co 11 have been fabricated through this method. The other method is the direct preparation of ordered structures from molecular or atomic precursors either physically or chemically. The solid-state methods for the fabrication of nanomaterials, such as physical and chemical vapor deposition (PVD 12 and CVD 1,13 ), molecular beam epitaxy (MBE), 14 and manipulation through scanning tunnel microscopy (STM), 15 often need harsh conditions, expensive equipment, and state-of-the-art techniques. 16 However, the solution chemistry methods can avoid the above limitations. 16 And if some ordered systems are adopted as templates in the synthesis process, the ordered structure of nanomaterials can be obtained. Braun et al. 17 reported the synthesis of semiconductor-organic superlattices based on cadmium sulfide and cadmium selenide templated by hexagonal liquid crystals. We have prepared the parallel nanowires of CdS 18 and ZnS 19 with the diameter as small as 3 nm templated, also by hexagonal liquid crystals. These kinds of template are known as "soft" ones. The "hard" templates of porous polymer membranes and anodic aluminum oxides (AAO) are widely applied in the synthesis of nanowires and nanoparticles. 20,21 The AAO template takes a great advantage of arranging cylindrical pores, of uniform diameter, in a hexagonal array. 20 This greatly benefits the fabrication of ordered nanowire arrays. The Martin group has reported the synthesis of nanoparticles, nanowires, and nanotubules of metals, semiconductors, and polymers by electrodeposition, 22 sol-gel deposition, 23 and polymerization 24 in AAO membranes. Routkevitch fabricated CdS nanowire arrays by electrochemical deposition into an AAO template. 25 In this paper, we study the synthesis of CdS nanowire arrays with a solution reaction method by injecting the reactants into the pores of the AAO membrane.Although Martin et al. 23 prepared several kinds of metal oxide nanofibrils and nanotubes through immersion of the AAO membranes into the corresponding sols and then calcination, there are few other reports about the synthesis of one-dimensional nanostructures in AAO membranes in aqueous solutions with methods other than electrodeposition. The reason usually is that the in situ formed nanoparticles hinder the dispersion of reactants into the inner part of the pores. We tried to prepare CdS nanowires in AAO with aqueous solutions of Cd 2+ and H 2 S or Na 2 S as the reactants, but only low aspect ratio nanoparticles were obtained. We adopted thioacetamide (TAA) as the precursor of H 2 S in this research. It can gradually liberate H 2 S in aqueous solution, and react with Cd 2+ slowly. It effectively eliminat...