Progress in Solid State Chemistry最新文献

Fullerene derivatives with amino acids, peptides and proteins have wide perspectives in biomedical applications. Thus, development and up-scaling of synthesis procedures, as well as investigation of the physico-chemical and biological properties of these derivatives, are extremely important. The present paper systematizes the current literature data on synthesis, physico-chemical properties and application of fullerene derivatives with amino acids, peptides and proteins in biomedicine. Experimental and theoretical data presented in the review give a comprehensive overview of these substances and can be valuable for specialists in the fields of nanotechnology, nanomaterials and bionanomedicine.

A comprehensive structural comparison of 56 Te⁶⁺-, Mo⁶⁺-, and W⁶⁺-containing oxides with the double perovskite stoichiometry (A₂BB′O₆) is presented. This work shows that much like d⁰ Mo⁶⁺- and W⁶⁺-containing perovskites, p⁰ Te⁶⁺-containing compositions are strongly affected by the tolerance factor and identities of the A- and B-cations. To make this comparison more complete, the ambient temperature crystal structures of five A₂BTeO₆ (A = Ca²⁺, Sr²⁺, or Ba²⁺; B = Zn²⁺ or Cd²⁺) perovskites were determined via powder diffraction and their vibronic and electronic structures were probed via infrared and diffuse reflectance spectroscopy. The new structural information reported here coupled with a thorough review of relevant literature demonstrates that Te⁶⁺, with its sigma bonding preference and lack of allowed orbital mixing gives rise to additional structure types that are not commonly observed in the Mo⁶⁺ or W⁶⁺ analogues. Analysis of double perovskites containing the hexavalent cations comparing the tolerance factor to the difference in ionic radii of the cations with octahedral coordination is presented. Additionally, examination of the Coulombic repulsions between the B and Te⁶⁺ cations plotted as a function of difference in the twelve- and seven-coordinate ionic radii for the A- and B-cations respectively provides new insight on why A₂BTeO₆ and A₂BWO₆ (A = B = Sr²⁺ or Ba²⁺) adopt perovskite structures with non-cooperative octahedral tilting distortions, while cooperative octahedral distortions are observed when the A and B sites are occupied by smaller cations like Ca²⁺ and Cd²⁺.

The stereochemistry of 5s² (E) lone pair of divalent Sn (Sn^II designated by M*) and the lone pair triplet around the fluorine ions are examined complementarily with stereo-chemical approach and ab initio quantum investigations focusing on the electron localization and pertaining electronic structure properties, obtained within Density Functional Theory (DFT) and derived Electron Localization Function (ELF) mapping. The review completes a series of former ones focusing on the stereochemical role played by electron lone pairs LP. We start by examining LP-free Sn^IVF₄ then develop on Sn^IIF₂E in its three crystal varieties (α, β, γ). The investigation then extends to study two mixed-valence fluorides: Sn₂^IISn^IVF₆E₂ and Sn^IISn^IVF₆E. The lone pair presence is readily detected in the crystalline network by its sphere of influence characterized by a radius rE, and M*-E directions; all distances are also detailed and assessed. The observations point to significant modifications of the structure which are also analyzed with the electronic density of states DOS projected over the different atomic constituents. Within the selected fluorides details of Sn^II various coordination numbers (CN) generally indicate one-sided coordination; specifically: CN = 4 + 1 SnF₄E triangular bipyramid, CN = 5 + 1 SnF₅E distorted octahedron (square pyramid with E roughly symmetric of its F apex) and CN = 6 octahedron [SnE]F₆. In the latter, the rotation speed of E (which increases with Z number due to relativistic effects) and the size of the F polyhedron make it favorable enough to E rotating around Sn²⁺ with the particularity of its transformation into a large cation [SnE]²⁺ with a size comparable to Ca²⁺, Sr²⁺ or Ba²⁺.

Bond relaxation from one equilibrium to another under perturbation matters uniquely the performance of a substance and thus it has enormous impact to materials science and engineering. However, the basic rules for the perturbation-bond-property correlation and efficient probing strategies for high-resolution detection stay yet great challenge. This treatise features recent progress in this regard with focus on the multifield bond oscillation notion and the theory-enabled phonon spectrometrics. From the perspective of Fourier transformation and the Taylor series of the potentials, we correlate the phonon spectral signatures directly to the transition of the characteristic bonds in terms of stiffness (frequency shift), number fraction (integral of the differential spectral peak), structure fluctuation (linewidth), and the macroscopic properties of the substance. A systematic examination of the spectral feature evolution for group IV, III-V, II-VI crystals, layered graphene nanoribbons, black phosphor, (W, Mo)(S₂, Se₂) flakes, typical nanocrystals, and liquid water and aqueous solutions under perturbation has enabled the ever-unexpected information on the perturbation-bond-property regulations. Consistency between predictions and measurements of the crystal size-resolved phonon frequency shift clarifies that atomic dimer oscillation dictates the vibration modes showing blueshift while the collective vibration of oscillators formed between a certain atom and its nearest neighbors governs the modes of redshift when the sample size is reduced. Theoretical matching to the phonon frequency shift due to atomic undercoordination, mechanical and thermal activation, and aqueous charge injection by solvation has been realized. The reproduction of experimental measurements has turned out quantitative information of bond length, bond energy, single bond force constant, binding energy density, vibration mode activation energy, Debye temperature, elastic modulus, and the number and stiffness transition of bonds from the mode of references to the conditioned upon perturbation. Findings prove not only the essentiality of the multifield lattice oscillating dynamics but also the immense power of the phonon spectrometrics in revealing the bond-phonon-property correlation of solid and liquid substance.

Band gap engineering of TiO₂ has attracted many researchers looking to extend its applicability as a functional material. Although TiO₂ has been commercialised in applications that utilise its special properties, its band gap should be modified to improve its performance, especially as an active photo catalyst. Reduction of TiO₂ under a hydrogen atmosphere is a promising method which can increase the visible-light absorption efficiency of TiO₂ and enhance its electrochemical and other properties related to electronic band structure. In this second review paper, the production and influence of O vacancies $\left(V_O\right)$ and other defects, such as interstitial cations, under vacuum and hydrogen are reviewed for the common phases of TiO₂. The particular modification TiO_2–x in which O is randomly removed from the crystal structure is considered in detail. Despite early evidence that hydrogen is absorbed into the bulk of TiO₂, the action of hydrogen has become controversial in recent years, with claims that surface disorder is responsible for the enhanced photoactivity induced by exposure to hydrogen. The many published experimental and density-functional-theory modelling studies are surveyed with the aims of determining what is agreed or contested, and relating defect structure to band structure. It is concluded that further work is needed to clarify the mechanisms of defect production and defect diffusion, as well as the origins of the numerous sample colours observed following treatment in vacuum or hydrogen.

Chalcogenide lone pair semiconducting materials are important materials due to their prospective applications in thermoelectrics, phase change memories, topological insulators etc. Investigating these lone pair semiconductors for versatile applications, different electronic properties were studied by researchers world-wide. Analyses of these semiconducting materials in bulk and thin films for electronic properties like dark and photo-conductivity, photosensitivity, carrier concentration, carrier type, relaxation time and thermopower are the major constituents while accepting them for applications. This review stresses on the electronic properties of several binary, ternary and quaternary lone pair chalcogenide systems. The electronic properties are generally discussed on the basis of chemical ordering in system. A brief discussion on some theoretical background of conduction mechanism has also been incorporated for new researchers in this field. Potential applications of chalcogenide semiconducting materials have been outlined.

Advances in the device fabrication in all emerging fields with promising features and improved control on material properties provide a strong motivation for researchers to reveal, recognize the potential of existing materials and to develop new ones with excellent properties by scheme a low cost syntheses method. Since the discovery of abundant, inorganic mayenite electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄ (thereafter, C12A7:e⁻) (2003), it has attracted much attention due to its unique and unconventional properties such as high electron concentration (∼2.3–7 × 10²¹ cm⁻³) and low work function (WF∼2.4 eV), which are comparable value with alkali metals, but is chemically inert in an ambient atmosphere. Furthermore, a severe reducing environment enables us to substitute electrons almost completely for anions in the cages, forming a stable inorganic electride, C12A7:e⁻. Finally, the formation of these active anions in this material has potential application as a catalyst support in the NH₃ synthesis/decomposition, CO₂ dissociation and specially recently introduced by our group as electrocatalyst in fuel cell. To further boost these applications the important thing was to synthesize high specific surface area, nanosized C12A7:e⁻ powder with enhanced conductivity, that can be done by cation doping. Over the last decade, experimental studies supported by theoretical calculations have demonstrated that cation elements doping can further boost its electrical properties. Therefore, our group studied doping with more suitable cations, Si, Sn, Ga, V etc in C12A7:e⁻ and we will explain each in detail. In this review we are going to describe progress in the synthesis of C12A7:e⁻ especially in nanosized powder material, and about most important recent challenges towards the suitable cations doping in C12A7:e⁻ electride and finally its industrial important applications as a catalyst.

Spin glass state originating from the magnetic frustration due to the geometric arrangement or cation disorder is an interesting topic of research. FeNbO₄, exhibiting multifarious applications, crystallizes mainly in three different polymorphic forms with cation ordered and disordered structures. Despite their antiferromagnetic nature, the orthorhombic (o-FeNbO₄) and monoclinic FeNbO₄ (m-FeNbO₄) polymorphs exhibit a difference in their magnetic properties at low temperatures. Here, we report our observation of spin glass behaviour of o-FeNbO₄ with a cation disordered structure. Our work is a combined experimental and theoretical study of structure-magnetic property relations of the antiferromagnetic o- and m-FeNbO₄ with the Néel temperatures of 30 and 46 K, respectively. o-FeNbO₄ contrasted itself from m-FeNbO₄ as a spin glass by exhibiting field-dependent bifurcation in ZFC and FC magnetization, frequency-dependent AC susceptibility, memory effect, thermoremanence, and anamoly in the heat capacity. The presence of antiphase domains and boundaries due to cation order/disorder in both the structural polymorphs was evidenced from the electron diffraction analyses that account for the observed low temperature magnetic interactions. Further, modeling the structures with varying amounts of cation disorder using first principles calculations revealed the structural stability and competing spin interactions that support our experimentally observed spin glass behaviour of o-FeNbO₄.

Ternary transition metal nitrides (TTMNs) have acquired substantial attention due to the ability to offer for tuning properties. Furthermore efforts to develop new TTMNs have resulted in the development of new syntheses approaches. In this review, recent progress made regarding investigations on electronic structure, stoichiometry, crystal structures, synthesis and applications are reviewed. Intermediate bonding in these solids exist in the structure types revealed so far. Bonding in these systems are an intriguing mix of ionic (oxide-like) and covalent (carbide-like). This enhances the possibilities of finding unique structures (i.e. anti-fluorite analogous [1]). A good case in point is the Delafosite types and η-nitrides structures found commonly in TTMNs which are typically associated with ABO_x type oxides and carbides. Due to the rich structural chemistry associated with TTMNs, their study is considered a growing area in solid state and applied chemistry. Advancement made in the synthesis of powder and thin film materials of TTMNs are discussed. The powder methods involve the following methods: solid state, high-pressure-high temperature, solvothermal method, ammonothermal method, sol-gel method, Pechini method, temperature-programmed reduction, thermal degradation of metal complex, solid-state metal oxide-organic reaction, solid state ion exchange reaction, and electrodeposition replacement method. On the other hand, the TTMN thin film fabrication is based on two types of methods; physical vapor deposition (PVD) and chemical vapor deposition (CVD) method. The PVD involve deposition using different ways using laser or plasma based approaches (eg. pulsed laser deposition (PLD)) and magnetron sputtering. Chemical vapor deposition methods involve electrodeposition reaction method. Among all synthesis methods, the sol-gel process following the ammonolysis is considered comparatively better for large scale production owing to the simple apparatus setup. Different synthesis methods are deployable based on the application at hand. Applications can be range from electrocatalysts in ORR reaction [2,3], electrocatalysts as sensor [4], supercapacitors [2,3,5], solar cell [6], magnetic, superconducting [7], hard coating materials [8] e.g. protective, functional, conductive, wear-resistance and decorative coating, NH₃ synthesis [9], and hydrogenation process in hydrocarbon reactions [10].