Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.     

Synthesis and study of Np(V) sesquioxalates

Neptunium(V) at its relatively high concentrations in oxalate solutions forms, along with the mono-and bioxalate complexes, the intermediate binuclear anion (NpO₂)₂(C₂O₄) ₃ ^4? . This anion gradually crystallizes from cold aqueous-ethanol solutions in the form of the compound Na₄(NpO₂)₂(C₂O₄)₃ · 6H₂O, and from hot aqueous-ethanol solutions, in the form of a lower hydrate, Na₄(NpO₂)₂(C₂O₄)₃ · 2H₂O. Both compounds were characterized by powder X-ray diffraction and by electronic absorption and IR spectra. The thermal behavior of the hexahydrate in air was studied. Attempts to prepare the related crystalline compounds M₄(NpO₂)₂(C₂O₄)₃ · nH₂O with M = Li or NH₄ failed.     

Growth and properties of Cu<Subscript>2</Subscript>ZnSnS<Subscript>4</Subscript> thin films prepared by multiple metallic layer stacks as a function of sulfurization time

In this paper, we report the two stage growth of Cu₂ZnSnS₄ (CZTS) thin films as a function of sulfurization time. First, magnetron sputtered metallic precursors were deposited sequentially (Zn/Cu/Sn/Cu) over rotating glass substrates held at 230?°C. Later, the sputtered precursors were heat treated at 500?°C in the ambiance of sulfur for various time durations in the range, 10–120 min. The sulfur treated samples were examined using various analytical tools to understand the role of sulfurization time on the CZTS growth and properties. From composition and structural analysis, Zn/Cu/Sn/Cu precursors sulfurized for shorter duration (10 and 20 min) revealed severe deficiency of sulfur that resulted in several metallic, bi-metallic and metal sulfide phases. With the increase of sulfurization time to 30 min, sulfur incorporation was enhanced and reached stoichiometric ratio (~50% S) for CZTS growth, however, samples were poorly crystalline in nature and consisted of prominent Cu_2?xS phase as well. The Zn/Cu/Sn/Cu precursors sulfurized for 60 min exhibited prominent CZTS phase without Cu_2?xS phase. Further, rise in sulfurization time to 120 min enabled drastic improvement in crystallinity of CZTS phase. Raman mapping over 60 µm × 60 µm for these films confirmed the homogeneous phase growth of CZTS. XPS study revealed the oxidation states of Cu¹⁺, Zn²⁺, Sn⁴⁺ and S^2? in CZTS films. The optimized films showed high absorption coefficient of 10⁵ cm^?1 with an optical band gap of 1.51 eV. These films showed leaf like grain morphology with high mobility and low resistivity of 18.2 cm²/V-s and 0.7 Ω-cm, respectively.     

Synthesis of Cu2ZnSnS4 films from sequentially electrodeposited Cu–Sn–Zn precursors and their structural and optical properties

The Cu₂ZnSnS₄ (CZTS) films are successfully prepared using a process of sequentially electrodeposited Cu–Sn–Zn precursors by a novel electrolyte formula and optimized parameters on Mo substrate, succeeded by annealing in saturated sulfur atmosphere. The results show that the Cu/Sn/Zn precursor sequence is strict, and optimized electro-deposition parameters are as follows: ?0.6 V, 5 min for Cu, ?1.2 V, 2 min for Sn, and ?1.35 V, 10 min for Zn. Layered precursors firstly alloy into Cu₆Sn₅ and CuZn binary phases under low annealing temperature. Then Cu₆Sn₅ and CuZn alloys decompose in sulfur atmosphere, and form CuS, SnS and ZnS binary phases. Cu₂SnS₃ ternary phase forms through reaction between CuS and SnS with increasing the temperature. Finally, the CZTS film is synthesized through reaction among binary and ternary sulfides. The photoluminescence peak from the CZTS films synthesized at 550 °C for 1 h is about at 1.49 eV.     

Optical and thermal characteristics of glasses based on TeO 2

Glass samples have been synthesized in quaternary system based on TeO ₂–oxide within composition, 85TeO ₂–5Nb ₂O ₅–5ZnO–5Ag ₂O, 68TeO ₂–5Nb ₂O ₅–20ZnO–7Na ₂O and [(75?x)TeO ₂–5Nb ₂O ₅–20ZnO–xPbO, x = 7, 18 mol%]. Structural characterization of the glasses was studied with respect to their thermal stability, refractive indices, third order nonlinear optical susceptibility, IR spectra and Vickers hardness. For four different prepared glasses, density in the range from 5·3744 to 6·0731 g· cm ^???1, the glass transition temperature (T _g) in the range from 326 to 350 °C and refractive indices, n, in the range from 2·1273 to 2·2123 at 435 nm and Vickers hardness, H _v, in the range from 2·91 to 3·44 GPa were determined. The value of third order nonlinear optical susceptibilities ${\vert} {\chi}^{\text{(3)}}{\vert} {\approx} $ 17·9 ·10^{??? 13} esu of glass within composition, 68TeO ₂–5Nb ₂O ₅–20ZnO–7PbO, was measured by using degenerate four-wave mixing (DFWM).     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: V. Crystal Structure of [Co(NH3)6][PuO2(C2O4)2] · 3H2O

The compound [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O was studied by single crystal X-ray diffraction. The structure contains dimeric complex anions [PuO₂(C₂O₄)₂] ₂ ⁶⁻ in which the coordination polyhedra of the Pu atoms are distorted pentagonal bipyramids sharing a common equatorial edge. In going from [Co(NH₃)₆] · [NpO₂(C₂O₄)₂] · 3H₂O to [Co(NH₃)₆][PuO₂(C₂O₄)₂] · 3H₂O, the An-O distances, both axial (in the actinyl group) and equatorial, decrease virtually isotropically. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 419–422. Original Russian Text Copyright ? 2005 by Grigor'ev, Antipin, Krot, Bessonov.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: III. Synthesis and Study of NaPuO2C2O4·nH2O with n = 3, 1, and 0

NaPuO₂C₂O₄·3H₂O was isolated from a freshly prepared oxalate solution of Pu(VI) by reduction with a stoichiometric amount of hydrazine hydrate. Heating of the compound results in its stepwise dehydration with successive formation of the monohydrate and anhydrous salt. According to powder X-ray patterns, NaPuO₂C₂O₄·nH₂O (n = 3, 4) is isostructural to the corresponding analogs NaNpO₂C₂O₄·nH₂O. The unit cell parameters of NaNpO₂C₂O₄·H₂O and NaPuO₂C₂O₄·nH₂O (n = 3, 1) were determined. The results of the X-ray analysis and the electronic and IR spectra of the neptunyl(V) and plutonyl(V) crystalline compounds suggest the presence of cation-cation bonds in NaPuO₂C₂O₄·nH₂O (n = 1, 0). __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 105–109. Original Russian Text Copyright ? 2005 by Krot, Bessonov, Grigor’ev, Charushnikova, Makarenkov.     

Phase diagram of the Na2CO3 · 10H2O-Na2S2O3 · 5H2O system

Using thermal analysis, we have constructed the phase diagram of the crystalline hydrate system Na₂CO₃ · 10H₂O-Na₂S₂O₃ · 5H₂O, which has been shown to have eutectic phase relationships. The eutectic composition is 27 wt % Na₂CO₃ · 10H₂O + 73 wt % Na₂S₂O₃ · 5H₂O, and the eutectic temperature is T _e = ?0.92°C. We have determined the enthalpy of fusion of the alloys in this system and evaluated the activities of their components both at the liquidus temperatures and in metastable regions. The composition dependences of the above thermodynamic characteristics are shown to correlate with each other and to have extreme values at the eutectic composition. The results obtained lead us to recommend the eutectic mixture of the crystalline hydrates in this system as a heat storage material.     

Evolution and temperature dependence of ZnO formation by high power sonication

The sonochemical reaction between varying concentrations of zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (C₆H₁₂N₄) in a 150 W dual transducer sonicator resulted in different phases of zinc compounds. Single phase zinc oxide (ZnO) was exclusively obtained in the case of 0.05 M. By tracking the products synthesized at 50 °C, zinc hydroxide (Zn(OH)₂) was formed in the first 40 min and replaced by ZnO after prolonged sonication. Zn(OH)₂ was also present in a mixed phase with ZnO when the reagent concentration was reduced to 0.01 M. The increase in the synthesis temperature up to 80 °C reduced defects and free radicals but introduced zinc hydroxide nitrate hydrate (Zn₅(OH)₈(NO₃)₂(H₂O)₂) which is a dominant phase from the reaction between highly concentrated reagents (0.1 M). High temperature and sonication power in this system tend to cause agglomerations into irregular microparticles.     

Preparation of w–cu nano-composite powders with high copper content using a chemical co-deposition technique

A novel chemical co-precipitation was used to produce W-70%Cu nanocomposite powders with coating structure. The precursors consisting of CuC₂O₄·xH₂O and WO₃·2H₂O were first synthesized using copper nitrate, ammonium metatungstate(AMT) and oxalic acid as the raw materials at 80?°C for 1.5?h when the concentrations of the reactants were 0.8?mol/L and the hydrogen ion concentration was 1.2?mol/L. The precursors were calcined to produce the powders with different phase components and microstructure at various temperatures. The CuWO₄ and CuO nano-powders were obtained at 300?°C, which is colder than the traditional reaction temperature (1000?°C) of CuO?+?WO₃ = CuWO₄. However, the cubic Cu₂O and Cu₂WO₄ could be formed when the calcining temperature was 600?°C. The hydrogen reduction results show that the calcined powder is reduced to obtain W-Cu composite powder at 750?°C and 800?°C. In reduction process, volatile WO₂(OH)₂ through chemical vapor transport(CVT) continuously spreads to the copper surface and is reduced to form W and the coated particle is eventually formed. This particle is Cu particle coated by W phase and the interface between W and Cu phases is semi-coherent. It is found that the average particle size of the reduced powder is 30–50?nm observed by TEM images.     

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B₂O₃·H₂O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn₄B₂O₇·H₂O (4ZnO·B₂O₃·H₂O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B₂O₃·H₂O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B₂O₃·H₂O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm^?2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm^?2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm^?2 after 10 h for direct comparison with the coated samples.     

Customizing Metal-Organic Frameworks by Lego-Brick Strategy for One-Step Purification of Ethylene from a Quaternary Gas Mixture

One-step purification of ethylene (C₂H₄) from a quaternary gas mixture of C₂H₆/C₂H₄/C₂H₂/CO₂ by adsorption is a promising separation process, yet developing adsorbents that synergistically capture various gas impurities remains challenging. Herein, a Lego-brick strategy is proposed to customize pore chemistry in a unified framework material. The ethane-selective MOF platform is further modified with customized binding sites to specifically adsorb acetylene and carbon dioxide, thus one-step purification of C₂H₄ with high productivity of polymer-grade product (134 mol kg⁻¹) is achieved on the assembly of porous coordination polymer-2,5-furandicarboxylic acid (PCP-FDCA) and PCP-5-aminoisophthalic acid (IPA-NH₂). Computational studies verify that the low-polarity surface of this MOFs-based platform provides a delicate environment for C₂H₆ recognition, and the specific binding sites (FDCA and IPA-NH₂) exhibit favorable trapping of C₂H₂ and CO₂ via C H^δ+···O^δ− and C^δ+···N^δ− electrostatic interactions, respectively. The proposed Lego-brick strategy to customize binding sites within the MOFs structure provides new ideas for the design of adsorbents for compounded separation tasks.     

Magnetic Nanocrystalline Mg0.5Zn0.5Fe2O4: Preparation, Morphology Evolution, and Kinetics of Thermal Decomposition of Precursor

Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O was synthesized by solid-state reaction at low heating temperatures using MgSO₄?7H₂O, ZnSO₄?7H₂O, FeSO₄?7H₂O, and Na₂C₂O₄ as raw materials. The spinel Mg_0.5Zn_0.5Fe₂O₄ was obtained via calcining Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O above 400 °C for 1 h in air. The Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The results showed that Mg_0.5Zn_0.5Fe₂O₄ obtained at 400 °C had a specific saturation magnetization of 27.3 emu?g^?1. The thermal process of Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O experienced three steps, which are: first, the dehydration of water of crystallization and decomposition of Mg_0.5Zn_0.5C₂O₄ into MgO and ZnO, then the reaction of Fe₂(C₂O₄)₃ with MgO and ZnO into amorphous Mg_0.5Zn_0.5Fe₂O₄, and at last the crystallization of Mg_0.5Zn_0.5Fe₂O₄. Based on the KAS equation and the OFW equation, the values of the activation energies associated with the thermal process of Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O were determined to be 69±11 and 71±9 kJ?mol^?1 for the first and second thermal process steps, respectively.     

Enhanced non-enzymatic glucose sensing of Cu–BTC-derived porous copper@carbon agglomerate

Porous copper@carbon agglomerate (PCCA) is prepared by pyrolysis of Cu₃(BTC)₂·3H₂O (Cu–BTC, BTC = 1,3,5-benzenetricarboxylic acid) in 5% H₂–N₂ mixture atmosphere. The phase and morphology evolution are thoroughly examined by XRD, Raman, BET, TG, XPS, SEM and TEM, respectively. The results show that PCCA is formed at 400 °C and maintains the cubic morphology of the original Cu–BTC crystal. PCCA is composed by round-shaped copper nanoparticles that covered outside by thin layer of carbon. The non-enzymatic glucose sensing properties of PCCA-modified glassy carbon electrode (Cu/GCE) are characterized by cyclic voltammetry. The sensor shows high sensitivity of 614.3 µA mM^?1 to glucose oxidation and negligible responses toward interference from uric acid, ascorbic acid, dopamine and l-cysteine at the level of their physiological concentrations. The sensor also exhibits rapid response (< 6 s), wide linear range (up to 3.33 mM) and low detection limit (0.29 µM at signal/noise ratio (S/N) = 3). Finally, the good stability, reproducibility and repeatability to glucose detection make PCCA a promising catalyst for non-enzymatic glucose sensor.     

Synthesis and characterisation of infinite coordination networks with 1,6-bis(4-pyridyl)hexane and copper nitrate

Crystallisation of 1,6-bis(4-pyridyl)hexane (Py₂C₆H₁₂) with copper nitrate gives two different phases. Phase 1 of composition [Cu(Py₂C₆H₁₂)₃(NO₃)₂]·2[Cu(Py₂C₆H₁₂)₂(H₂O)(NO₃)]·2(NO₃)·EtOH consists of two different infinite chains in a 1:2 ratio that are interlocked. Hydrogen bonds link chains I to II and chains II to II. In contrast phase 2 of composition [Cu₂(Py₂C₆H₁₂)₄(H₂O)₂]·(NO₃)₄·(Py₂C₆H₁₂)·(EtOH)·2(H₂O) is based upon an infinite 3D framework. It consists of four interpenetrating 3D networks that are crystallographically equivalent.     

Phase- and size-controllable synthesis with efficient photocatalytic activity of ZnS nanoparticles

We report a simple solution-based method to synthesize phase- and size-controllable ZnS nanoparticles at low temperature. Cubic ZnS (c-ZnS) and hexagonal ZnS nanoparticles (h-ZnS) were obtained by heating an aqueous solution of Zn(NO₃)₂·6H₂O and Na₂S₂O₃·5H₂O at different temperatures. When the system was heated at 65 °C for 24 h, hexagonal crystal structure of ZnS nanoparticles, with size of 50–350 nm, was obtained, as confirmed by X-ray diffraction and selected-area electron diffraction. When the reaction temperature was 100 °C under hydrothermal condition, c-ZnS nanoparticles were obtained and exhibited monodisperse nanoparticles with average size of 4 nm. Proper rate of S releasing tuned by the variation of pH value is believed to be critical to stabilize the hexagonal ZnS nanoparticles. Compared with large size of h-ZnS nanoparticles, c-ZnS nanoparticles show higher photocatalytic activity in degrading methyl orange (MO). The degradation efficiency of c-ZnS nanoparticles reaches 97% under UV irradiation for 120 min. The good ultraviolet absorbing ability, charge separation property, and large surface area of c-ZnS nanoparticles are believed to have a positive impact on improving the degradation rate and degradation efficiency of MO.     

The thermal property of alkaline earth diphosphates made by a wet process

Alkaline earth diphosphates [K₂Mg₃(P₂O₇)₂·6H₂0, 2Mg₂P₂O₇·15H₂O, Sr₂P₂O₇·3H₂O, and Ba₂P₂O₇·2H₂O] were made by mixing solutions of tetrapotassium diphosphate and alkaline earth dichlorides. These diphosphates showed the following thermal reactions when they were heated up to 1000 °C:

1. dehydration M₄P₂O₇·nH₂O → M₄P₂O₇·(n?x)H₂O + xH₂O (0
2. degradation M₄P₂O₇ + H₂O → 2M₂HPO₄
3. disproportionation or metathesis 2M₂HPO₄ → M₃PO₄ + MH₂PO₄
4. polymerization 2M₂HPO₄ + nMH₂PO₄ → M_n+4P_n+2O_3n+7 + (n+1)H₂O
5. reorganization or degradation to diphosphate M_n+2P_nO_3n+1 + (n?2)M₃PO₄ → (n?1)M₄P₂O₇
6. reorganization or degradation to tri- and/or diphosphates (for only Ba₂P₂O₇·2H₂O) M_n+2P_nO_3n+1 + 1/2 (n?3)M₃PO₄ → 1/2 (n?1)M₅P₃O₁₀ (n?3) M_n+2P_nO_3n+1 + (n?3)M₃PO₄ → M₅P₃O₁₀ + (2n?4)M₄P₂O₇ (n?3) where M stands for K and/or 1/2Mg, 1/2Sr, or 1/2Ba.

     

Contribution a l'etude des tetraoxalatolanthanidates III

Guanidinium tetra-oxalatolanthanidates III of general formula (CN₃H₆)₅ M(C₂O₄)₄, nH₂O have been prepared in highly cristalline solide state (M = Nd, Ho, Er, Tm et Sc, Y).Formation constants of corresponding ionic species in aqueous solution M(C₂O₄)₄^5? (M = Ho et Er) were determined by spectrometric investigation using M(C₂O₄)₄^5?- Y^4? system with formation of a mixed complex M C₂O₄ Y^3? (Y = ethylenediaminetetracetate ion): logβ₄^Ho = 16,8±0,2 and β₄^Er = 16,9±0,3 at an ionic strength of 2.5.     

Framework materials containing polyoxovanadates as building units: synthesis and characterization of (N2H5)2[M3(H2O)12V18O42(EO4)]·24H2O (M = Mg,Ca) and Li6[Mn3(H2O)12V18O42(EO4)]·24H2O (E = V,S)

The reaction of an aqueous solution of lithium vanadate with hydrazinium sulfate results in a dark-colored solution that reacts with magnesium sulfate heptahydrate, calcium sulfate dihydrate, and manganese(II) chloride tetrahydrate to yield single crystals of (N₂H₅)₂[M₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (M = Mg, Ca) and Li₆[Mn₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (E = V, S), respectively. The crystal structures of the new solids consist of interpenetrating three-dimensional networks of {V₁₈O₄₂(EO₄)} clusters interlinked via bridging {M(H₂O)₄} (M = Mg, Ca, Mn) groups. The voids in these structures are occupied by lattice water and ion exchangeable cations.     

Sulfurization time effects on the growth of Cu2ZnSnS4 thin films by solution method

Cu₂ZnSnS₄ (CZTS) films were obtained by sulfurizing (Cu, Sn) S/ZnS structured precursors prepared by a combination of the successive ionic layer absorption and reaction method and the chemical bath deposition method, respectively. The effect of sulfurization time on structure, composition and optical properties of these CZTS thin films was studied. The results of energy dispersive spectroscopy indicate that the annealed CZTS thin films are of Cu-poor and Zn-rich states. The X-ray diffraction studies reveal that Cu_2?x S phase exists in the annealed CZTS thin film prepared by sulfurization for 20 min, while the Raman spectroscopy analysis shows that there is a small Cu₂SnS₃ phase existing in those by sulfurization for 20 and 40 min. The band gap (E _g ) of the annealed CZTS thin films, which are determined by reflection spectroscopy, varies from 1.49 to 1.56 eV depending on sulfurization time. The best CZTS thin film is the one prepared by sulfurization for 80 min, exhibiting a single kesterite structure, dense morphology, ideal band gap (E _g  = 1.55 eV) and high optical absorption coefficient (>10⁴ cm^?1).