Heterostructured Bi2Se3 nanowires with periodic phase boundaries

Single and multijunction nanowires with diameters of 10-40 nm were synthesized by an electrically assisted sonochemical method in aqueous solution at room temperature. By properly controlling the reaction conditions and reactants, this method opens a new strategy towards the fabrication of one-dimensional superlattices in nanowires under ambient conditions. Such a chemical approach provides a promising and simple way to synthesize high-performance building blocks for device applications.     

Synthesis of single crystal Sn-doped In(2)O(3) nanowires: size-dependent conductive characteristics

Single crystalline Sn doped In(2)O(3) (ITO) NWs (nanowires) were synthesized via an Au-catalyzed VLS (vapor-liquid-solid) method at 600 °C. The different sizes (～20, ～40, ～80 nm) of the Au NPs (nanoparticles) provided the controllable diameters for ITO NWs during growth. Phase and microstructures confirmed by high-resolution transmission electron microscope images (HRTEM) and X-ray diffraction (XRD) spectra indicated that the phase of In(2)O(3) NWs had a growth direction of [100]. X-ray photoelectron spectroscopy (XPS) was employed to obtain the chemical compositions of the ITO NWs as well as the ratio of Sn/In and oxygen concentrations. The findings indicated that low resistivity was found for ITO NWs with smaller diameters due to higher concentrations of oxygen vacancies and less incorporation of Sn atoms inside the NWs. The resistivity of NWs increases with increasing diameter due to more Sn atoms being incorporated into the NW and their reduction of the amount of oxygen vacancies. Low resistivity NWs could be achieved again due to excess Sn atoms doped into the large diameter NWs. Therefore, by optimizing the well-controlled growth of the NW diameter and interface states, we are able to tune the electrical properties of Sn-doped ITO NWs.     

In-situ Synthesis of the Thinnest In2Se3/In2S3/In2Se3 Sandwich-Like Heterojunction for Photoelectrocatalytic Water Splitting

The efficient utilization of solar energy for photoelectrocatalytic (PEC) water splitting is a feasible solution for developing clean energy and alleviating environmental issues. However, as the core of PEC technology, the existing photoanode catalysts have disadvantages such as poor photoelectrocatalytic conversion efficiency, low conductivity of photogenerated carriers, and instability. Here, we report the ultrathin two-dimensional sandwich-like (SW) heterojunction of In₂Se₃/In₂S₃/In₂Se₃ (SW In₂S₃@In₂Se₃) for the first time for PEC water splitting. Our findings identify the efficient separation of electrons and holes by constructing SW In₂S₃@In₂Se₃ heterojunction. The in situ synthesis of ultrathin nanosheet arrays by using surface substitution of Se atom to epitaxially grow cell In₂Se₃ maximizes the contact area of heterogeneous interface and accelerates the transmission of charge carrier. Benefitting from the unique structure and composition characteristic, SW In₂S₃@In₂Se₃ displays excellent performance in PEC water splitting. The photocurrent density of SW In₂S₃@In₂Se₃ reaches 8.43 mA cm⁻² at 1.23 V_RHE. Compared with In₂S₃, the SW In₂S₃@In₂Se₃ photoanode has nearly 12 times higher PEC performance, which represents the best performance among the In₂S₃-based photoanode heterojunction reported so far. The evolution rate of O₂ reaches 78.8 μmol cm⁻² h⁻¹, and the photocurrent has no apparent variety within 24 h.     

Synthesis of crystalline umangite phase of copper selenide (Cu3Se2) for TiO2 photoanode-based solar cell application

Journal of Solid State Electrochemistry - This study deals with the sensitization of the porous titanium oxide (TiO2) films deposited on fluorine doped tin oxide with copper selenide (Cu3Se2). The...     

Short-period superlattice structure of Sn-doped In(2)O(3)(ZnO)(4) and In(2)O(3)(ZnO)(5) nanowires

Two longitudinal superlattice structures of In(2)O(3)(ZnO)(4) and In(2)O(3)(ZnO)(5) nanowires were exclusively produced by a thermal evaporation method. The diameter is periodically modulated in the range of 50-90 nm. The nanowires consist of one In-O layer and five (or six) layered Zn-O slabs stacked alternately perpendicular to the long axis, with a modulation period of 1.65 (or 1.9) nm. These superlattice nanowires were doped with 6-8% Sn. The X-ray diffraction pattern reveals the structural defects of wurtzite ZnO crystals due to the In/Sn incorporation. The high-resolution X-ray photoelectron spectrum suggests that In and Sn withdraw the electrons from Zn and enhance the number of dangling-bond O 2p states, resulting in the reduction of the band gap. Photoluminescence and cathodoluminescence exhibit the peak shift of near band edge emission to the lower energy and the enhancement of green emission as the In/Sn content increases.     

Synthesis, characterization, and optical properties of In2O3 semiconductor nanowires

In2O3 semiconductor nanowires were synthesized by the chemical vapor deposition method through carbon thermal reduction at 900 degrees C with 95% Ar and 5% O2 gas flow. The In2O3 nanowires were characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence spectroscopy (PL). For the first time, we observed the formation of corundum-type h-In2O3 nanowires and branched In2O3 nanowires. The PL spectra of In2O3 nanowires show strong visible red emission at 1.85 eV (670 nm) at low temperature, possibly caused by a small amount of oxygen vacancies in the nanowire crystal structure.     

Synthesis and transformation of 2-aminobenzimidazoles (review)

A review of papers published after 1965 that deals with methods for the synthesis of 2-aminobenzimidazoles and their properties is given.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–887, July, 1979.     

Pyridineselenolate Complexes of Copper and Indium: Precursors to CuSe(x)() and In(2)Se(3)

The pyridineselenolate (2-Se-NC(5)H(4), (SePy)) and the 3-(trimethylsilyl)pyridineselenolate (3-Me(3)Si-2-Se-NC(5)H(4) (SePy)) ligands form air-stable homoleptic coordination compounds of Cu(I) { [Cu(SePy)](4) (1) and [Cu(SePy)](4) (2)} and In(III) {In(SePy)(3) (3) and In(SePy)(3) (4)}. Mass spectroscopic characterization of the Cu(I) compounds indicated a tetrametallic core, and this was confirmed with a single-crystal X-ray structural characterization of crystalline 1 and 2, which both contain a tetrametallic cluster of Cu(I) ions bound to two doubly bridging Se atoms and a pyridine nitrogen. The Cu coordination sphere is completed with two strong Cu-Cu bonds and one weaker Cu-Cu interaction. The indium compounds 3 and 4 are each distorted fac-octahedral molecules with chelating SePy ligands. These compounds are useful low-temperature precursors to the binary selenides. Both 3 and 4 sublime intact; 3 thermally decomposes to give In(2)Se(3). The Cu clusters do not sublime intact but still decompose to give metal selenide phases: 2 decomposes to give pure alpha-CuSe at low temperatures and increasing amounts of Cu(2)(-)(x)()Se at elevated temperatures, while 3 decomposes to give a mixture of CuSe phases at all temperatures. Crystal data (Mo Kalpha: 1, 153(5) K; 2-4, 293(2) K) are as follows: 1, monoclinic space group C2/c, a = 20.643(5) ?, b = 16.967(2) ?, c = 16.025(2) ?, beta = 114.16(2) degrees, Z = 8; 2, tetragonal space group I4(1)/a, a = 14.756(3) ?, c = 19.925(3) ?, Z = 4; 3, trigonal space group P&thremacr;c1, a = 13.352(2) ?, c = 13.526(2) ?, Z = 4; 4, monoclinic space group P2(1)/c, a = 9.793(1) ?, b = 20.828(6) ?, c = 16.505(1) ?, beta = 96.69(1) degrees, Z = 4.     

Soluble precursors for CuInSe2, CuIn(1-x)Ga(x)Se2, and Cu2ZnSn(S,Se)4 based on colloidal nanocrystals and molecular metal chalcogenide surface ligands

We report a new platform for design of soluble precursors for CuInSe(2) (CIS), Cu(In(1-x)Ga(x))Se(2) (CIGS), and Cu(2)ZnSn(S,Se)(4) (CZTS) phases for thin-film potovoltaics. To form these complex phases, we used colloidal nanocrystals (NCs) with metal chalcogenide complexes (MCCs) as surface ligands. The MCC ligands both provided colloidal stability and represented essential components of target phase. To obtain soluble precursors for CuInSe(2), we used Cu(2-x)Se NCs capped with In(2)Se(4)(2-) MCC surface ligands or CuInSe(2) NCs capped with {In(2)Cu(2)Se(4)S(3)}(3-) MCCs. A mixture of Cu(2-x)Se and ZnS NCs, both capped with Sn(2)S(6)(4-) or Sn(2)Se(6)(4-) ligands was used for solution deposition of CZTS films. Upon thermal annealing, the inorganic ligands reacted with NC cores forming well-crystallized pure ternary and quaternary phases. Solution-processed CIS and CZTS films featured large grain size and high phase purity, confirming the prospects of this approach for practical applications.     

Pressure-induced cubic to monoclinic phase transformation in erbium sesquioxide Er(2)O(3)

Cubic Er(2)O(3) was compressed in a symmetric diamond anvil cell at room temperature and studied in situ using energy-dispersive X-ray diffraction. A transition to a monoclinic phase began at 9.9 GPa and was complete at 16.3 GPa and was accompanied by a approximately 9% volume decrease. The monoclinic phase was stable up to at least 30 GPa and could be quenched to ambient conditions. The normalized lattice parameter compression data for both phases were fit to linear equations, and the volume compression data were fit to third-order Birch-Murnaghan equations of state. The zero-pressure isothermal bulk moduli (B(0)) and the first-pressure derivatives (B(0)') for the cubic and monoclinic phases were 200(6) GPa and 8.4 and also 202(2) GPa and 1.0, respectively. Ab initio density functional theory calculations were performed to determine optimized lattice parameters and atom positions for the cubic, monoclinic, and hexagonal phases of Er(2)O(3). The calculated X-ray spectra and predicted transition pressure are in good qualitative agreement with the experimental results.     

Untersuchungen zu Struktur und Schmelzverhalten von (C6H5)2As2Se3 und (CH3)3As3Se3

Investigations of the Structure and the Melting Behaviour of (C₆H₅)₂As₂Se₃ and (CH₃)₃As₃Se₃ The compounds (C₆H₅)₂As₂Se₃ and (CH₃)₃As₃Se₃ exist in a crystalline and a glass-like form. Both phases were investigated by the methods of mass, i.r., and u.v. spectroscopy and by DTA. The mass-spectroscopic fragmentation patterns are shown. The proposed structures of the crystalline forms are confirmed by these results. In the melts equilibria exist between the cyclic molecules of the crystalline forms and chains and other rings. On attempts to prepare the compound (C₆H₅)₃As₃Se₃, only (C₆H₅)₂As₂Se₃ was found. The possible reasons of the preferred stability of the five ring molecule are discussed.     

Synthesis and transformation of (N-substituted 2-methyl-5-methoxy-3-indolyl)succinic acids

The reaction of N-substituted 2-methyl-5-methoxyindoles with maleic anhydride gave the corresponding (2-methyl-5-methoxy-3-indolyl)succinic anhydrides, which were hydrolyzed to acids and converted to monoamides by reaction with primary or secondary amines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1525–1527, November, 1972.     

On the lamellar compounds CuBiP(2)Se(6), AgBiP(2)Se(6) and AgBiP(2)S(6). Antiferroelectric phase transitions due to cooperative Cu(+) and Bi(3+) ion motion

CuBiP(2)Se(6), AgBiP(2)Se(6), and AgBiP(2)S(6) were prepared from the corresponding elements. CuBiP(2)Se(6) and AgBiP(2)Se(6) crystallize in the space group R with a = 6.5532(16) A and c = 39.762(13) A for CuBiP(2)Se(6) and a = 6.6524(13) A and c = 39.615(15) A for AgBiP(2)Se(6). AgBiP(2)S(6) crystallizes in the triclinic space group P with a = 6.3833(13) A, b = 7.1439(14) A, c = 9.5366(19) A, alpha = 91.89(3) degrees , beta = 91.45(3) degrees , gamma = 94.05(3) degrees . CuBiP(2)Se(6) was found to exhibit a temperature-dependent antiferroelectric ordering of the Cu(+) and Bi(3+) ions in the lattice. An intermediate and a fully ordered structure were refined at 173 and 97 K, respectively. Electronic band and total energy calculations at the DFT level clearly suggest that the antiferroelectric model is energetically favored over the paraelectric and hypothetical ferrielectric models. This phase transition can be classified as a second-order Jahn-Teller distortion. The antiferroelectric state of CuBiP(2)Se(6) is an indirect gap semiconductor. The compounds were characterized with differential thermal analysis and solid-state UV/vis diffuse reflectance spectroscopy. Generalized implications regarding the expected ferroelectric behavior of compounds in the CuMP(2)Se(6) system (M = trivalent metal) are discussed.     

Synthesis and characterization of Cu(In(x)B(1-x))Se2 nanocrystals for low-cost thin film photovoltaics

Chalcopyrite quaternary semiconductor Cu(In(x)B(1-x))Se(2) nanocrystals have been successfully prepared via a relatively simple and convenient solvothermal route. The effect of different solvents on the formation of the product also indicates that diethylenetriamine is the optimal solvent for this reaction. The device parameters for a single junction Cu(In(x)B(1-x))Se(2) solar cell under AM1.5G are as follows: an open circuit voltage of 265 mV, a short-circuit current of 25.90 mA/cm(2), a fill factor of 34%, and a power conversion efficiency of 2.34%. Based on a series of comparative experiments under different reaction conditions, the probable formation mechanism of crystal Cu(In(x)B(1-x))Se(2) nanorods is proposed.     

Coordination chemistry of diselenophosphinate complexes: the X-ray single-crystal structures of [K(Se2PPh2)(THF)2]2 and [In(Se2PPh2)3].L (L = THF, PhMe)

Reaction of potassium diphenylphosphide with elemental selenium is shown to give [K(Se(2)PPh(2))(THF)(2)](2) 1, which further reacts with InCl(3) to yield [In(Se(2)PPh(2))(3)] 2. Crystallization of 2 from either THF or PhMe gave 2.THF or 2.PhMe, respectively, both of which form loosely linked dimers in the solid state via Se...Se intermolecular van der Waals interactions. Decomposition of 2 has been studied by TGA.