花状TiO2分级结构的可控合成与其光催化性能

采用水热法可控合成了花状TiO₂分级结构材料,运用扫描电镜、透射电镜、X射线衍射、N₂物理吸附-脱附等手段,对其进行了表征,系统研究了NaOH用量、H₂O₂浓度、HNO₃浓度、反应温度及时间等因素对所得样品形貌的影响,并评价了它们的光催化性能.结果表明,花状TiO₂分级结构为锐钛矿相,颗粒大小均一;随制备条件的变化,构成花状TiO₂分级结构的基元结构分别为纳米线、纳米片,纳米线直径约25nm,纳米片厚度不足10nm;该样品具有较高的比表面积,表现出良好的单次光催化活性与重复使用性能.     

A new phosphor with flower-like structure and luminescent properties of Sr<Subscript>2</Subscript>MgSi<Subscript>2</Subscript>O<Subscript>7</Subscript>: Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript> long afterglow materials by sol–gel method

The flower-like phosphors of Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ with high brightness and long afterglow were obtained by sol–gel method. X-ray diffraction pattern (XRD) shows that single-phased Sr₂MgSi₂O₇ phosphor is prepared by sol–gel method under 1250 °C. Scanning electron microscope (SEM) indicates that the phosphor consists of nano-sized whiskers which are detected for the first time in Eu²⁺ and Dy³⁺ co-doped long-lasting phosphorescence silicates. Furthermore, the investigation on the mechanism indicates that the internal structure and gas, liquid and solid phase effect play important roles in the formation of flower-like Sr₂MgSi₂O₇: Eu²⁺, Dy³⁺ nanostructure. Finally, the optical properties of flower-like Sr₂MgSi₂O₇ nanostructure have been characterized by photoluminescence (PL) spectra.     

α-Fe2O3 nanoflowers: synthesis,characterization, electrochemical sensing and photocatalytic property

Nanoflower structured α-Fe₂O₃ was synthesized by adding hexamine to an aqueous solution of ferrous sulphate followed by drying and annealing at 600 °C for 6 h. X-ray diffraction analysis, Fourier-transformed infrared spectroscopy, Raman and DRS UV–visible absorption spectroscopy showed the formation of α-Fe₂O₃ with good crystalline nature. Field emission-scanning electron microscopy investigation revealed that the α-Fe₂O₃ has flower-like morphology, which is composed of nanorods. Cyclic voltammetry and chronoamperometry were used to investigate their electrochemical sensing property towards uric acid (UA). α-Fe₂O₃ exhibited enhanced sensing behavior with respect to that of bare GCE. Additionally, the α-Fe₂O₃ nanoflowers exhibit better photocatalytic activity of up to 71.7 % against rhodamine B (RhB) in short time of 60 min under visible light irradiation. It is found that the smaller crystallite size and flower-like morphology play a vital role in allowing an interaction between α-Fe₂O₃ and UA or RhB dye which enhances both the electrochemical sensing and photocatalytic activity.     

非晶态镍硼酸盐结构的EXAFS研究

由摩尔比分别为1:2和1:8的NiCl₂·6H₂O和Na₂B₄O₇·10H₂O作为反应物, 合成两种非晶态镍硼酸盐, 同时通过水热法合成β-Ni(OH)₂. 化学分析和热重-微商热重法(TG-DTG)分析结果确定两种非晶态镍硼酸盐的分子组成分别为NiO·0.8B₂O₃·4.5H₂O和NiO·B₂O₃·3H₂O. 激光拉曼(Raman)实验结果表明镍硼酸盐样品中主要存在的硼氧阴离子为B₃O₃(OH)₅^2-和B₂O(OH)₆^2-. 同步辐射扩展X射线吸收精细结构(EXAFS)方法对样品进行结构解析, 通过数据拟合给出样品中Ni 原子周围近邻配位原子种类、配位数以及原子间距离. 用不同晶体结构作为标准对两种非晶态镍硼酸盐进行拟合的结果表明, 样品中Ni 原子周围局域结构与Ni₃B₂O₆晶体(ICSD No.31387)中的吻合较好. Ni 原子周围配位原子为O、B和Ni, 对于NiO·0.8B₂O₃·4.5H₂O, 配位数分别为5.7、3.8和3.8, 配位距离分别为0.208、0.263 和0.311 nm; 对于NiO·B₂O₃·3H₂O, 配位数分别为6.0、4.0 和4.0, 配位距离分别为0.207、0.262和0.310 nm.     

Voltammetric determination of vitamin B<Subscript>6</Subscript> (pyridoxine) at a graphite screen-printed electrode modified with graphene oxide/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> nanocomposite

The preparation and study of electrochemical properties of a graphite screen-printed electrode (SPE) modified with the GO/Fe₃O₄@SiO₂ (GO is graphene oxide) nanocomposites are described. The morphologies of the GO/Fe₃O₄@SiO₂ nanocomposites were examined by scanning electron microscopy. The electrochemical oxidation of vitamin B₆ (pyridoxine) on SPE modified with the GO/Fe₃O₄@SiO₂ nanocomposite was investigated by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. Under optimum conditions (pH 7.0), the vitamin B₆ oxidation at the surface of the modified SPE occurs at a potential about 190 mV less positive than that at the unmodified SPE. A linear voltammetric response for vitamin B₆ was obtained in the concentration range 1.0?10 ⁶—9.0?10 ⁴ mol L^–1 with a detection limit of 5.2?10 ⁷ mol L^–1 using differential pulse voltammetry. The developed sensor was also successfully applied for determination of trace level of vitamin B₆ in both the standard vitamin B₆ sample and biological samples (urine).     

Preparation and characterization of carbon-coated Li[Ni1/3Co1/3Mn1/3]O2 cathode material for lithium-ion batteries

The carbon-coated Li[Ni_1/3Co_1/3Mn_1/3]O₂ was synthesized from the porous Li[Ni_1/3Co_1/3Mn_1/3]O₂ precursor using citric acid as the carbon source. The electrochemical results showed that both cycling performance and rate capability were improved by the carbon-coating of the Li[Ni_1/3Co_1/3Mn_1/3]O₂ materials. It is proposed that the enhanced electrochemical properties by the carbon-coating are attributed to the increased electronic conductivity because the carbon distributed among the surfaces of spherical Li[Ni_1/3Co_1/3Mn_1/3]O₂ powders favored the transference of electron and reduced cell polarization.     

Ionic liquid-assisted electrochemical determination of pyrimethanil using reduced graphene oxide conjugated to flower-like NiCo2O4

The novel hierarchical flower-like superstructure NiCo₂O₄/reduced graphene oxide (rGO) hybrids have been successfully synthesized with a facile one-step hydrothermal process for the determination of fungicide pyrimethanil (PMT). For comparison, various structures of NiCo₂O₄/rGO including hexagonal nanoplates and nanorods were also synthesized. Among them, three-dimensional (3D) flower-like NiCo₂O₄/rGO exhibited the highest electrocatalytic activity for the oxidation of PMT. With the synergistic effect of [OMIM]PF₆ ionic liquid (IL), the electrochemical sensor film (NiCo₂O₄/rGO/IL) further facilitated interfacial electron transfer and enhanced electrocatalytic activity for the oxidation of PMT. Under the optimum conditions, the electrochemical sensor exhibited two linear ranges of 0.1–10.0 μmol/L and 20.0–140 μmol/L for PMT with a low detection concentration of 11.0 nmol/L. Besides, the interference, repeatability, reproducibility and stability measurements were also evaluated. The proposed method was successfully applied to the detection of PMT in water, seawater, fruits and vegetables with good recovery ranging from 93% to 105%, and possessed potential applications in the analysis of real samples.     

3D flower-like heterostructured TiO2@Ni(OH)2 microspheres for solar photocatalytic hydrogen production

TiO₂@Ni(OH)₂ core-shell microspheres were synthesized by a facile strategy to obtain a perfect 3D flower-like nanostructure with well-arranged Ni(OH)₂ nanoflakes on the surfaces of TiO₂ microspheres; this arrangement led to a six-fold enhancement in photocatalytic hydrogen evolution. The unique p-n type heterostructure not only promotes the separation and transfer of photogenerated charge carriers significantly, but also offers more active sites for photocatalytic hydrogen production. A photocatalytic mechanism is proposed based on the results of electrochemical measurements and X-ray photoelectron spectroscopy.     

Preparation of 2CaO·3B2O3·H2O nanomaterials and evaluation of their flame retardant properties by a thermal analysis method

Different morphologies of calcium borate 2CaO·3B₂O₃·H₂O, nanoribbon, bundle-like nanostructure and fan-shaped non-nanostructure, have been prepared under hydrothermal conditions, which were characterized by XRD, FT-IR, TGA and SEM. Their flame retardant properties to the polypropylene were investigated by thermal analysis method (including TG, DSC and non-isothermal decomposition kinetics) and oxygen index method. With the decrease in TG mass loss, the increase in heat absorption for DSC in N₂ atmosphere, the increase in LOI values, and the increase in apparent activation energy E_a, the flame retardant properties of prepared 2CaO·3B₂O₃·H₂O samples increased gradually from non-nanostructure to bundle-like nanostructure and then to nanoribbon. This trend may be ascribed to their sizes being decreased accordingly. The flame retarding mechanism has been proposed. The mechanical property of polypropylene/2CaO·3B₂O₃·H₂O composite material has also been evaluated. It can be predicted that 2CaO·3B₂O₃·H₂O nanoribbon could serve as an excellent flame retardant.

     

Synthesis of Li[Li0.2Ni0.2Mn0.6]O2 by radiated polymer gel method and impact of deficient Li on its structure and electrochemical properties

Layered Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li[Li_0.2Ni_0.2Mn_0.6]O₂ compounds were successfully synthesized by radiated polymer gel (RPG) method. The effect of deficient Li on the structure and electrochemical performance was investigated by means of X-ray diffraction, X-ray absorption near-edge spectroscopy and electrochemical cell cycling. The reduced Ni valence in Li[Li_0.16Ni_0.21Mn_0.63]O₂ leads to a higher capacity owing to faster Li⁺ chemical diffusivity relative to the baseline composition Li[Li_0.2Ni_0.2Mn_0.6]O₂. Cyclic voltammograms (CV) and a simultaneous direct current (DC) resistance measurement were also performed on Li/Li[Li_0.16Ni_0.21Mn_0.63]O₂ and Li/Li[Li_0.2Ni_0.2Mn_0.6]O₂ cells. Li[Li_0.16Ni_0.21Mn_0.63]O₂ shows better electrochemical performance with a reversible capacity of 158 mA hg⁻¹ at 1C rate at 20 °C.     

NiII36-Containing 54-Tungsto-6-Silicate: Synthesis,Structure, Magnetic and Electrochemical Studies

The 36-Ni^II-containing 54-tungsto-6-silicate, [Ni₃₆(OH)₁₈(H₂O)₃₆(SiW₉O₃₄)₆]⁶⁻ ( Ni₃₆ ) was synthesized by a simple one-pot reaction of the Ni₂-pivalate complex [Ni₂(μ-OH₂)(O₂CCMe₃)₄(HO₂CCMe₃)₄] with the trilacunary [SiW₉O₃₄]¹⁰⁻ polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single-crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni₃₆ comprises six equivalent {Ni^II₆SiW₉} units which are linked by Ni−O−W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni₆} building blocks in Ni₃₆ remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni₆} units. Electrochemical studies indicate that the first reduction is reversible and associated with the W^VI/V couple, whereas the second reduction is irreversible attributed to the Ni^II/0 couple.     

Crystal-field calculation of the 3d multiplets of the binuclear Ni(II) monothiocarboxylates

The electronic spectra of the dimers (Ni(RCOS)₂)₂ and (Ni(RCOS)₂)₂ · C₂H₅OH are calculated by crystal-field theory in terms of different polyhedra of coordination around the two Ni²⁺ ions. The necessary radial parameters are taken from other clusters of Ni²⁺ after a detailed study of their intercluster transferability. The calculations are organized in two blocks. In the first one, the Ni²⁺Ni²⁺ interaction is neglected and the clusters Ni^AS₄, Ni^BO₄, and Ni^BO₅ are considered. In the second block, this interaction is explicitly taken into account as a point-charge perturbation produced by one of the two metal ions on the 3d states of the other one. Accordingly, we deal with the Ni^AS₄Ni^B, in which the Ni^B acts as a pointlike ligand of charge q, and with the Ni^BO₄Ni^A and the Ni^BO₅Ni^A, where the Ni^A is the punctual ligand. The calculation shows that the optical spectra and magnetic moments of these dimers can be best reproduced if $\text{q ? 0}$, i.e., when the metal-metal electrostatic interaction is negligible. The agreement with the experiments quickly disappears as q grows. This calculation supports the interpretation of Melson et al. (Inorg. Chem.9, 1116 (1970)) according to which the 3d electronic distribution of the Ni²⁺ ions in these dimers is probably controlled by their nearest neighbors rather than by the metal-metal interaction.     

Copper Nanoflowers on Carbon Cloth as a Flexible Electrode Toward Both Enzymeless Electrocatalytic Glucose and H2O2

Herein, a novel electrochemical sensor for glucose and hydrogen peroxide (H₂O₂) detection was successfully developed through the use of Cu nanoflowers (CuNFs) combined with flexible carbon cloth (CC) substrate. The 3D flower-like CuNFs in size uniformly and firmly grow on CC substrate by a facile, scalable, one-step hydrothermal strategy. Morphology, size and surface property of the prepared CuNFs/CC were examined by SEM, EDS and TEM, respectively. The electrochemical mechanism of CuNFs/CC for glucose and H₂O₂ detection was investigated by cyclic voltammetry. High electrochemical performances were displayed with amperometric i-t curves including a wide linear range from 1.0 nM to 6.0 mM for glucose and from 1.0 μM to 36.66 mM for H₂O₂, respectively. Good sensitivity, repeatability, and stability, as well as anti-interference ability, the carbon cloth-supported CuNFs will be the promising materials for fabricating practical non-enzymatic glucose and H₂O₂ sensors.     

Preparation and electrochemical characterization of Ruddlesden–Popper oxide La4Ni3O10 cathode for IT-SOFCs by sol–gel method

La₄Ni₃O₁₀ oxide was synthesized as a cathode material for intermediate-temperature solid oxide fuel cells by a facile sol–gel method using a nonionic surfactant (EO)106(PO)70(EO)106 tri-block copolymer (F127) as the chelating agent. The crystal structure, electrical conductivity, and electrochemical properties of La₄Ni₃O₁₀ were investigated by X-ray diffraction, DC four-probe method, electrochemical impedance spectra, and I–V measurements. The La₄Ni₃O₁₀ cathode showed a significantly low polarization resistance (0.26 Ω cm²) and cathodic overpotential value (0.037 V at the current density of 0.1 A cm^?2) at 750 °C. The results measured suggest that the diffusion process was the rate-limiting step for the oxygen reduction reaction. The La₄Ni₃O₁₀ cathode revealed a high exchange current density value of 62.4 mA cm^?2 at 750 °C. Furthermore, an anode-supported single cell with La₄Ni₃O₁₀ cathode was fabricated and tested from 650 to 800 °C with humidified hydrogen (～3 vol% H₂O) as the fuel and the static air as the oxidant. The maximum power density of 900 mW cm^?2 was achieved at 750 °C.     

Comparison of corn starch-assisted sol–gel and combustion methods to prepare LiMn x Co y Ni z O2 compounds

In a novel attempt to exploit corn starch as gelling agent (in sol–gel method) and combustible fuel (in solution-assisted combustion method), high-capacity LiMn_0.4Ni_0.4Co_0.2O₂ and LiMn_1/3Ni_1/3Co_1/3O₂ cathode materials have been prepared and a comparison of electrochemical performance of the same has been made. Among the two compounds chosen for the study, LiMn_1/3Ni_1/3Co_1/3O₂ exhibits better physical and electrochemical properties. Particularly, LiMn_1/3Ni_1/3Co_1/3O₂ cathode synthesized using corn starch-assisted combustion method exhibits an appreciable capacity of 176 mAh g^?1, excellent capacity retention of 93 % up to 100 cycles and susceptible to rate capability test up to 1 C rate, thus qualifying the same for high-capacity and high-rate lithium battery applications. The study demonstrates the possibility of exploiting corn starch as gelling agent and as a combustible fuel in synthesizing lithium intercalating oxide compounds with improved electrochemical behaviour.     

Improved pechini sol-gel fabrication of Li2B4O7/NiO/Ni3(BO3)2 nanocomposites to advanced photocatalytic performance

In current research, nano-scaled Li₂B₄O₇/NiO/Ni₃(BO₃)₂ (LiBNi) composites were fabricated through improved pechini sol–gel method for advanced photocatalytic applications to remove dye contaminations of drinking water under UV/Visible irradiation. To optimize LiBNi nanocomposites properties, different complexing agents including ethylenediaminetetraacetic acid (EDTA), citric acid, tannic acid, tartaric acid and phthalic acid were utilized in pechini sol–gel process. Various sizes and morphologies of Li₂B₄O₇/NiO/Ni₃(BO₃)₂ nanocomposites obtained that were characterized by SEM and TEM techniques. Also, to confirm crystalline and structural features of nano-sized LiBNi samples, analyses of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX) were performed. By consideration of UV–Vis data, band-gap of LiBNi nanocomposites premeditated is 3.35 eV. Moreover, photocatalytic degradation of Li₂B₄O₇/NiO/Ni₃(BO₃)₂ nanocomposites was examined via UV/visible waves in aqueous solution for degradation acid red 88 pollutant after 90 min. Some operative factors such as nanocatalyst concentration and irradiation type for optimized LiBNi nanocomposites were assessed for removal of drinking water contaminant.     

Gold nanowire assembling architecture for H2O2 electrochemical sensor

Morphological control of nanomaterials is of great interest due to their size and shape-dependent chemical and physical properties and very important applications in many fields such as biomedicine, sensors, electronics and others. In this paper, we reported a simple strategy for synthesizing gold nanowire assembling architecture at room temperature. It is found that two important factors, the proper volume ratio of ethanol to water and poly(vinyl pyrrolidone) (PVP), will play important roles in synthesizing flower-like short gold nanowire assembling spheres. Furthermore, the obtained flower-like gold assembling spheres with high surface-to-volume ratio have been employed as enhancing materials for electrochemical sensing H₂O₂. The present electrochemical sensing platform exhibited good electrocatalytic activity towards the reduction of H₂O₂. The detection limit for H₂O₂ was found to be 1.2 μM, which was lower than certain enzyme-based biosensors.     

Darstellung,Kristallstruktur und magnetische Eigenschaften von In2Ni21B6

Preparation, Crystal Structure, and Magnetic Properties of In₂Ni₂₁B₆ In₂Ni₂₁B₆ was prepared by solid state reaction of the elements at 1223 K. The single‐crystals, obtained for the first time, exhibit metallic luster and crystallize in space group Fm 3 m (a = 1059.11(2) pm; Z = 4; 128 symmetry independent reflections; R1 = 0.027; wR2 = 0.125). In₂Ni₂₁B₆ is related to the Cr₂₃C₆‐structure and belongs to the structural family of τ‐borides. The compound melts at 1426 K. Polycrystalline samples of In₂Ni₂₁B₆ are ferromagnetic with a Curie‐Temperature of T_C = 596 K and show metallic conductivity in the range from 12 K to 320 K.     

氧化钛包覆对LiCo0.2Ni0.4Mn0.4O2结构和性能的影响

采用SEM、 XRD、 XPS、恒电流充放电等方法研究了不同量的氧化钛包覆对LiCo_0.2Ni_0.4Mn_0.4O₂结构和电化学性能的影响。结果表明，0.3mol%氧化钛包覆能显著改善LiCo_0.2Ni_0.4Mn_0.4O₂的循环性能、倍率放电能力及高截止电压(3.0～4.5 V)下的循环性。XPS数据表明氧化钛包覆能明显的抑制样品表面的氧化活性，从而减少了电极材料表面与电解液的反应，改善了LiCo_0.2Ni_0.4Mn_0.4O₂的电化学性能。     

Preparation and properties of nickel site doped material Ni1-yXyCo2O4 as supercapacitor materials by in-situ growth method

Although NiCo₂O₄ has been widely applied in supercapacitors, its actual capacity has been limited by the low conductivity and reactivity. Due to the relationship between the performance of the spinel-structured NiCo₂O₄ electrode material and its microstructure, in this paper, in order to modify the nanostructure of NiCo₂O₄ to improve its electrochemical performance, hydrothermal method is adopted to synthesize Ni_0.98X_0.02Co₂O₄(X = Fe, Cu, Mg, V, Ag, Mn, Mo, Ti) grown on nickel foam. After the synthesis, the physical morphology of the selected Ni_0.98Mg_0.02Co₂O₄ and Ni_0.98Mn_0.02Co₂O₄ are tested and analyzed by XRD, SEM, XPS and FT-IR. According to the characterization results, it can be found that different kinds of metals are doped in the nickel site of NiCo₂O₄, and the microscopic morphology of materials is different. It can be seen from the SEM figure that Ni_0.98Mg_0.02Co₂O₄ is a small nano-scale particle, while Ni_0.98Mn_0.02Co₂O₄ presents rod-like braided structure, and doping at the nickel site does not affect the main structure of the material. It can be seen from EDS data that the atomic ratio and weight ratio of nickel and cobalt elements are consistent with the molecular formula. The XPS spectra of the corresponding elements showed that Ni, Co and O elements were corresponding to NiCo₂O₄ materials. In conclusion, the result of physical morphology characterization analysis shows that the material is still in standard NiCo₂O₄ spinel structure.