Uncovering the reason for structure-dependent thermoelectric performance still remains a big challenge. A low-temperature and easily scalable strategy for synthesizing Bi₂Te₃ nanostring hierarchical structures through solution-phase reactions, during which there is the conversion of “homo–hetero–homo” in Bi₂Te₃ heteroepitaxial growth, is reported. Bi₂Te₃ nanostrings are obtained through the transformation from pure Bi₂Te₃ hexagonal nanosheets followed by TeBi₂Te₃ “nanotop” heterostructures to Bi₂Te₃ nanostrings. The growth of Bi₂Te₃ nanostrings appears to be a self-assembly process through a wavy competition process generated from Te and Bi³⁺. The conversion of homo–hetero–homo opens up new platforms to investigate the wet chemistry of Bi₂Te₃ nanomaterials. Furthermore, to study the effect of morphologies and hetero/homo structures, especially with the same origin and uniform conditions on their thermoelectric properties, the thermoelectric properties of Bi₂Te₃ nanostrings and TeBi₂Te₃ heterostructured pellets fabricated by spark plasma sintering have been investigated separately.

Ionic liquids (ILs) possess effective functions in controlling the phase and morphology of nanomaterials. However, it is still unclear how ILs affect the morphology control and what the origin of adsorption selectivity of ILs is on different crystal facets. It is a challenge to develop a simple method to select the suitable kinds of ILs for achieving the controllable synthesis of nanomaterials with designable shape. Herein, density functional theory (DFT) calculations were combined with experiment to study the interaction mechanism between ILs and crystal facets. An important relationship is proposed, named as the geometric matching principle, in which the adsorption site of substrate should not only need to meet the space requirement for interionic stacking of ILs, but also needs to maximize the interaction between adsorbed ILs and substrate. This new finding is meaningful for prediction of the adsorption selectivity of ILs and clarification of their shape-controlled chemistry.

Well-dispersed ammonium aluminum carbonate hydroxide (NH₄-Dw) and γ-AlOOH nanostructures with controlled morphologies have been synthesized by employing an ionic-liquid-assisted hydrothermal process. The basic strategies that were used in this work were: 1) A controllable phase transition from NH₄-Dw to γ-AlOOH could be realized by increasing the reaction temperature and 2) the morphological evolution of NH₄-Dw and γ-AlOOH nanostructures could be influenced by the concentration of the ionic liquid. Based on these experimental results, the main objective of this work was to clarify the effect models of the ionic liquids on the synthesis of NH₄-Dw and γ-AlOOH nanostructures, which could be divided into cationic- or anionic-dominant effect models, as determined by the different surface structures of the targets. Specifically, under the cationic-dominant regime, the ionic liquids mainly showed dispersion effects for the NH₄-Dw nanostructures, whereas the anionic-dominant model could induce the self-assembly of the γ-AlOOH particles to form hierarchical structures. Under the guidance of the proposed models, the effect of the ionic liquids would be optimized by an appropriate choice of cations or anions, as well as by considering the different effect models with the substrate surface. We expect that such effect models between ionic liquids and the target products will be helpful for understanding and designing rational ionic liquids that contain specific functional groups, thus open up new opportunities for the synthesis of inorganic nanomaterials with new morphologies and improved properties. In addition, these as-prepared NH₄-Dw and γ-AlOOH nanostructures were converted into porous γ-Al₂O₃ nanostructures by thermal decomposition, whilst preserving the same morphology. By using HRTEM and nitrogen-adsorption analysis, the obtained γ-Al₂O₃ samples were found to have excellent porous properties and, hence, may have applications in catalysis and adsorption.

In the work presented here, well-dispersed ferric giniite microcrystals with controlled sizes and shapes are solvothermally synthesized from ionic-liquid precursors by using 1-n-butyl-3-methylimidazolium dihydrogenphosphate ([Bmim][H₂PO₄]) as phosphate source. The success of this synthesis relies on the concentration and composition of the ionic-liquid precursors. By adjusting the molar ratios of Fe(NO₃)₃⋅9H₂O to [Bmim][H₂PO₄] as well as the composition of ionic-liquid precursors, we obtained uniform microstructures such as bipyramids exposing {111} facets, plates exposing {001} facets, hollow spheres, tetragonal hexadecahedron exposing {441} and {111} facets, and truncated bipyamids with carved {001} facets. The crystalline structure of the ferric giniite microcrystals is disclosed by various characterization techniques. It was revealed that [Bmim][H₂PO₄] played an important role in stabilizing the {111} facets of ferric giniite crystals, leading to the different morphologies in the presence of ionic-liquid precursors with different compositions. Furthermore, since these ferric giniite crystals were characterized by different facets, they could serve as model Fenton-like catalysts to uncover the correlation between the surface and the catalytic performance for the photodegradation of organic dyes under visible-light irradiation. Our measurements indicate that the photocatalytic activity of as-prepared Fenton-like catalysts is highly dependent on the exposed facets, and the surface area has essentially no obvious effect on the photocatalytic degradation of organic dyes in the present study. It is highly expected that these findings are useful in understanding the photocatalytic activity of Fenton-like catalysts with different morphologies, and suggest a promising new strategy for crystal-facet engineering of photocatalysts for wastewater treatment based on heterogeneous Fenton-like process.

The size- and shape-controlled synthesis of Sb₂S₃ nanostructures has been successfully realized by a facile hydrothermal route. A range of dimensional nanostructures, such as one-dimensional nanorods, two-dimensional nanowire bundles, three dimensional sheaf-like superstructures, dumbbell-shaped superstructures, and urchin-like microspheres, could be obtained through introducing different organic complex reagents or ionic liquids to the reaction system. The formation mechanisms of various Sb₂S₃ nanostructures have been rationally proposed based on the crystal structure and the nature of the complex reagents and the ionic liquid. The effects of experimental parameters on the final product are also discussed in detail. In addition, electrochemical measurements demonstrate that the as-synthesized Sb₂S₃ nanostructures have higher initial Li intercalation capacity and excellent cyclic performances, which indicates that the as-synthesized Sb₂S₃ nanostructures could have potential applications in commercial batteries.

Zn(OH)F nanofibers were successfully synthesized from Zn₅(OH)₈(NO₃)₂·2H₂O by microwave irradiation in the presence of the ionic liquid [Tmim][BF₄] (1,2,3-trimethylimidazolium tetrafluoroborate). The structure and morphology of the resulting Zn(OH)F nanofibers were investigated by XRD, SEM, and XPS, and the results indicate that the Zn(OH)F fibers are 80–200 nm in diameter and several micrometers in length. A hydrogen bonding π–π stacking mechanism is responsible for the 1D feature of Zn(OH)F. This method may be developed into a general way to synthesize other metal hydroxyfluoride nanostructures.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Polychloro-alkanes, including dichloromethane (CH₂Cl₂), chloroform (CHCl₃) and tetrachloromethane (CCl₄), were first introduced to synthesize trigonal selenium (t-Se) microrods as a new kind of coordinating solvent, which played two important roles in the formation of Se nuclei and templated effect of Se microrods. The possible formation mechanism of t-Se microrods was proposed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Reactions have been designed to verify the reversibility of butylamine intercalation–deintercalation in the layered perovskite-type oxide KCa₂Nb₃O₁₀. The reactions include ion exchange to form HCa₂Nb₃O₁₀·1.5H₂O, butylamine intercalation for producing C₄H₉NH₃Ca₂Nb₃O₁₀, transformation of C₄H₉NH₃Ca₂Nb₃O₁₀ into HCONH₃Ca₂Nb₃O₁₀ by formamide substitution and conversion of HCONH₃Ca₂Nb₃O₁₀ into HCa₂Nb₃O₁₀·1.5H₂O again by ion exchange. The complete reaction cycles were monitored by XRD, Raman spectroscopy, thermogravimetric (TG) and elemental analysis, and the resulting information was used to propose the structure evolution and to determine the organic components of the products. The well-matched powder X-ray diffraction (XRD) patterns and Raman spectra between the initial and recovered protonated materials confirmed that they have identical structural features of a protonated triple-layered perovskite. The C, H and N elemental analysis results and TG data indicate that the regenerated layered perovskite-type oxides also have a high capacity for alkylamine intercalation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A facile and convenient chemical precipitation route has been developed for the controlled growth of selenium nanowires and hierarchical microspheres at room temperature, with Na₂SeO₃ and hydrazine hydrate as starting materials in the presence of 1,2,3-trimethylimidazolium tetrafluoroborate (tmimBF₄). The surface morphology of microspheres can be tuned by adjusting the reaction media. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). Possible formation mechanisms of selenium nanowires and microspheres are proposed, respectively. The influences of the nature of reaction media, agitation and tmimBF₄ on the morphologies development were experimentally investigated and it was found that these factors were of great importance for the formation of Se morphologies. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)