Kinetic studies of the decomposition reaction of adducts of dinuclear Fe(Ⅱ)/O2

Kinetic studies of the decomposition reaction of dinuclear Fe(Ⅱ) adducts [Fe₂(N-Et-HPTB){O₂P(OPh)₂}](Cl- O₄)₂ (1) and [Fe₂(N-Et-HPTB) {O₂P(Ph)₂}] (ClO₄)₂ (2) with O₂ have been carried out at low temperature using UV-vis spectra. The decomposition reaction of Fe(Ⅱ)/O₂ adducts was first-order in the experimental conditions, and the activation parameters were obtained. ?H^¹ = 85.62 kJ·mol^-1, ?S¹ = 19.43 J·mol^-1·K^-1 for compound (1) and ?H^¹ = 97.97 kJ·mol^-1, ?S^¹ = 55.68 J·mol^-1·K^-1 for compound (2). These results are similar to those of dioxygen adducts of other metals complexes and natural enzymes such as methane mono- oxygenase (MMOH).     

Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

Electrodeposition and characterization of thermoelectric Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films

Bi₂Se₃ thin films were electrochemically deposited on Ti and indium tin oxide-coated glass substrates, respectively, at room temperature, using Bi(NO₃)₃·5H₂O and SeO₂ as starting materials in diluted HNO₃ solution. A conventional three-electrode cell was used with a platinum sheet as a counter electrode, and a saturated calomel electrode was used as a reference electrode. The films were annealed in argon atmosphere. The influence of cold isostatic pressing before annealing on the microstructure and thermoelectric properties of the films was investigated. X-ray diffraction analysis indicates that the film grown on the indium tin oxide-coated glass substrate is pure rhombohedral Bi₂Se₃, and the film grown on the Ti substrate consists of both rhombohedral and orthorhombic Bi₂Se₃.     

Giant magneto-optical faraday effect of nanometer Fe-In<Subscript>2</Subscript>O<Subscript>3</Subscript> granular films

The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-ln2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation angle θF value of the granular film samples with Fe volume fraction x = 35% is of the order of 10^5（°）/cm at room temperature. Temperature dependence of the Faraday rotation angle θF of Fe0.35（In2O3）0.65 granular films shows that θF value below 10 K increases rapidly with the decrease of the temperature, and when T= 4.2 K, θF value is 106（°）/cm. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that when the temperature decreases to a critical point Tp = 10 K, the transformation of state from ferro-agnetic to spin-glass-like occurs in Fe0.35（In2O3）0.65 granular films. The remarkable increase of the Faraday rotation angle θF value of Fe0.35（In2O3）0.65 granular films below 10 K seems to arise from the sp-d exchange interaction of the granular film samples in the spin-glass-like state.     

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO<Subscript>2</Subscript> electrodes

The ZnO-modified TiO₂ electrode was prepared by adding Zn(CH₃COO)₂·2H₂O to the TiO₂ colloid during the sol-gel production process, and was used in dye-sensitized solar cells (DSCs). The open circuit voltage (V _OC) and fill factor (ff) of the cells were improved significantly. The performances of the ZnO-modified TiO₂ electrode such as dark current, transient photocurrent, impedance, absorption spectra, and flat band potential (V _fb) were investigated. It is found that the interface charge recombination impedance increases and V _fb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO₂ film.     

Supermolecular layered double hydroxides

Research progresses in the layered double hydroxides [M _(1-x ^)/2+ M _x ³⁺ (OH)₂] ^x+ A _x ^n/n− ·mH₂O intercalated with metal coordinate ions or oxometalates in the last ten years are reviewed. These layered double hydroxides are mainly intercalated with polyoxometalate (POM) ions, a LiAl-LDH photochemical assembly containing TiO₂ and CH₃(CH₂)₁₂COO⁻ anions, together with Zn(TPPC) (porphyrin derivate) and macrocyclic ligand-containing porphyrin derivate anions. Emphasis is put on the synthesis methods for intercalation of the anions into the interlayer regions, the characterization techniques and structures for the layered compounds and the newest research progress in the fields such as catalysis. The review also forecasts the prospects of the field.     

TiO<Subscript>2</Subscript>@MgO core-shell film: Fabrication and application to dye-sensitized solar cells

In this study,TiO2@MgO core-shell film was obtained by using a simple chemical bath deposition method to coat a thin MgO film around TiO2 nanoparticles. The core-shell configuration was characterized by X-ray diffractometer (XRD),scanning elec-tron microscopy (SEM),energy dispersive X-ray spectroscopy (EDX),and high-resolution transmission electron microscopy (HRTEM). Lattice fringes were observed for the TiO2 particles,and the MgO shell showed an amorphous structure,revealing a clear distinction between the core and shell materials. Applying the core-shell film as photoanode to the dye-sensitized solar cells (DSSCs),it shows a superior performance compared to the pure TiO2 electrode. Under the illumination of simulated sunlight (75 mW-cm-2),the short circuit photocurrent (Jsc),the open circuit photovoltage (Voc),and the fill factor (fF) are 8.80 mA-cm-2,646 mV,and 0.69,respectively,and the conversion efficiency (η) in-creased by 21.8% (from 4.32% to 5.26%) when dipping for opti-mum condition.     

Synthesis, Characterization and Calorimetry of Ni（C4H8N2O3）2Cl2

A coordination complex was synthesized from NiCl2 and dipeptide glycylglycine（GG）. It was characterized by element analysis, NMR and TG methods, and then was determined to be Ni（C4HsN2O3）2Cl2. Using an isoperibolic reaction calorimeter, the standard molar enthalpy of formation of Ni（GG）2Cl2（solid） has been determined to be -（1 674.66±2.02） kJ · mol^-1 at 298.15 K.     

Inorganic-organic hybrids constructed of bis（undecatungstogerma- nate）lanthanates polyoxoanions and oxalate-bridged dinuclear copper complexes and their magnetic properties

A series of inorganic-organic hybrids K₂Na _m H_9−m [{Ln(GeW₁₁O₃₉)₂}{Cu₂(bpy)₂(μ-ox)}]·nH₂O (bpy = 2,2-bipyridine and ox = oxalate; Ln = La, Nd, Sm, Eu, Gd; n = 19, 17, 22, 20, 19; m = 4, 4, 4, 9, 2) were isolated after reacting in a potassium acetate buffer. X-ray structural analyses show that compounds 1–5 are isomorphic and consist of [Ln(GeW₁₁O₃₉)₂]¹³⁻ polyoxoanion building blocks and oxalate-bridged dinuclear copper metalorganic complex with a 1D chain structure. The 1D chain further connects into the 3D framework by π-π interactions with neighboring bpy groups. The magnetic susceptibility data indicate that antiferromagnetic coupling between the neighboring Cu²⁺ ions in the structure and the rare earth ions affects magnetic property of the structure.     

Investigation of the cross-reaction mechanism of C<Subscript>6</Subscript>H<Subscript>5</Subscript>F-HNO<Subscript>2</Subscript> aqueous solution irradiated at 355 nm by transient absorbance spectrum technique

The transient absorption spectrum technique was employed to investigate the cross-reaction mechanism of C6H5F-HNO2 aqueous solution irradiated at 355 nm. The characteristic and the kinetic parameters of transient species were also detected. Hydroxyl radical derived from the photolysis of HNO2 was added to monofluorobenzene with a second-order rate constant of （5.83±0.17）×10^9 L·mol^-1·s^-1 to form an adduct, C6H5F…OH, which was able to react with HNO2 as the main reaction pathway with a rate constant of （8.3±0.1）×10^7 L·mol^-1·s^-1. The C6F6…OH adduct can also be decayed by elimination of H2O to yield monofluorophenyl radical C6H4F-. By GC-MS technique, the final products were identified to be monofluorophenol, nitro-monofluorobenzene, nitro-monofluorophenol and para-fluorobiphenyl.     

Effect of CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O on gasification dissolution and deep reaction of coke

To more comprehensively analyze the effect of CO₂ and H₂O on the gasification dissolution reaction and deep reaction of coke, the reactions of coke with CO₂ and H₂O using high temperature gas-solid reaction apparatus over the range of 950-1250℃ were studied, and the thermodynamic and kinetic analyses were also performed. The results show that the average reaction rate of coke with H₂O is about 1.3-6.5 times that with CO₂ in the experimental temperature range. At the same temperature, the endothermic effect of coke with H₂O is less than that with CO₂. As the pressure increases, the gasification dissolution reaction of coke shifts to the high-temperature zone. The use of hydrogen-rich fuels is conducive to decreasing the energy consumed inside the blast furnace, and a corresponding high-pressure operation will help to suppress the gasification dissolution reaction of coke and reduce its deterioration. The interfacial chemical reaction is the main rate-limiting step over the experimental temperature range. The activation energies of the reaction of coke with CO₂ and H₂O are 169.23 kJ·mol-1 and 87.13 kJ·mol-1, respectively. Additionally, water vapor is more likely to diffuse into the coke interior at a lower temperature and thus aggravates the deterioration of coke in the middle upper part of blast furnace.     

Doping effect on thermoelectric properties of nonstoichiometric AgSbTe<Subscript>2</Subscript> compounds

Nonstoichiometric ternary thermoelectric materials Ag_0.84Sb_1.15M_0.01Te_2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag₂Te to α-Ag₂Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×10⁴ to 2.5×10⁴ and 2.3×10⁴ S·m⁻¹, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.     

Iron fractions in the apoplast of intact root tips of Zea mays L. seedlings affected by nitrogen form

The effects of ammonium (NH₄⁺-N ) and nitrate ( NO₃^--N ) were examined on Fe fractions and FeCN (ferricyanide) reductase activity in intact root tips (0—3 cm) of young maize (Zea mays L. cv. Lenz) in solution culture by using short-term experiment under controlled Fe deficiency conditions (containing high HCO₃^- concentration in preculture solution). The results showed that Fe(Ⅱ) concentrations in root tip apoplast of maize were only 20—40 nmol/g FW which accounted for 7%—13% of total Fe. Most of Fe in root tips existed as Fe(Ⅲ) compounds. Imposition of the roots to NH₄⁺-N or NO₃^--N for 60 min led to an increase of Fe(Ⅱ) in root tip apoplast. NH₄⁺-N led to an increased concentration of Fe(Ⅱ) and exchangeable Fe (Fe(Ⅱ) and Fe (Ⅲ)) in root tips, while NO₃^--N increased FeCN reductase activity. The relationship between pH and Fe fractions, FeCN reductase activity was also discussed.     

Layered Fe（Ⅲ） doped TiO2 thin-film electrodes for the photoelectrocatalytic oxidation of glucose and potassium hydrogen phthalate

Four types of TiO 2 thin-film electrodes were fabricated from TiO 2 and Fe(III) doped TiO 2 sols using a layer-by-layer dip-coating technique. Electrodes fabricated were TF (pure TiO 2 surface, Fe(III)-TiO 2 bottom layer), FT (Fe(III)-TiO 2 surface, pure TiO 2 bottom layer), TT (both layers pure TiO 2 ) and FF (both layers Fe(III)-TiO 2 ). The photoelectrochemical behavior of these electrodes was characterized using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and steady-state photocurrent measurements in aqueous 0.1 mol L –1 NaNO 3 containing varying concentrations of glucose or potassium hydrogen phthalate (KHP). EIS and LSV results revealed that exciton separation efficiency followed the sequence of TF﹥TT﹥FT > FF. Under a constant potential of +0.3 V, steady-state photocurrent profiles were recorded with varying organic compound concentrations. The TF electrode possessed the greatest photocatalytic capacity for oxidizing glucose and KHP, and possessed a KHP anti-poisoning effect. Enhanced photoelectrochemical performance of the TF electrode was attributed to effective exciton separation because of the layered TF structure.     

Dissolution of Al<Subscript>2</Subscript>TiO<Subscript>5</Subscript> inclusions in CaO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> slags at 1823 K

Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al₂TiO₅ inclusion was immersed in a CaO-SiO₂-Al₂O₃ molten slag for different durations at 1823 K. The Al₂TiO₅ dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO₂ diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/w(SiO₂) value in the reaction region. A liquid product (containing 0.7–1.2 w(CaO)/w(SiO₂), 15wt%–20wt% Al₂O₃, and 5wt%–15wt% TiO₂) forms on the inclusion surface when Al₂TiO₅ is dissolved in the slag. Al₂TiO₅ initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al₂TiO₅ dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.     

I-doping of anodized TiO<Subscript>2</Subscript> nanotubes using an electrochemical method

In order to obtain TiO2 with high photocatalytic activity, a cathode reduction was used to dope I⁷⁺ and I⁵⁺ into TiO₂ nanotubes of anodized Ti in C₂H₂O₄•2H₂O + NH₄F electrolyte. SEM images show that the anodization method integrated the preparation with the doping process, which for nonmetals-doping is advantageous to maintain the morphological integrity of TiO₂ nanotubes. I⁷⁺-I⁵⁺-doping enhances the UV response of TiO₂ and result in a red-shift. Under UV/visible irradiation, a I⁷⁺-I⁵⁺-doped sample (400°C) showed the highest I_ph and photocatalytic efficiency. A part of I^– in the I⁷⁺-I⁵⁺-doped sample is involved in the UV response, the red-shift and the higher I_ph.     

Single-crystal structure of coordination polymer [Nd2(C8H5NO4)3·4H2O]∞

Rapid progress is now being made in the design and synthesis of coordination polymers with unique topological structures[17]. Lots of interesting topological structures such as chain-like[4], ladder-like[8], grid-like[9], brick- like[10], comb-like structures[11], etc., have been reported. In recent years, preliminary applications of coordination polymers to chemistry and material science, such as molecular sieve, catalysis, nonlinear optical properties, magnetic materials, biotic sensors, etc…     

Synthesis and structure determination of ruthenium and osmium complexes with 2,6-bis-(diphenylphosphinomethyl) pyridine

2,6-Bis (diphenylphosphinomethyl) pyridine (PNP) reaction with Na₂OsCl₆ · 6H₂O to give the five coordinated, sixteen-electron complex Os (PNP)Cl₂. In the presence of formaldehyde, the reaction between Na₂OsCl₆· 6H₂O and PNP proceeds rapidly in boiling ethanol to give the coordinately saturated Os(PNP)Cl₂(CO). The IR spectrum of Os(PNP)Cl₂(CO) shows a strong absorption band at 1 970 cm⁻¹ assignable tov _∞ stretch. PNP reacts with RuCl₂(PPh₃)₃ and RuCl₂(DMSO)₄ (DMSO=dimethyl sulfoxide) to give Ru(PNP)Cl₂ (PPh₃) and Ru(PNP)Cl₂ (DMSO) respectively. The average Ru−Cl, Ru−P and Ru−N bond distance in Ru(PNP)Cl₂(PPh₃) determineby X-ray crystallography are 0.242, 0.236 and 0.216 nm, respectively. Li Zhaoying: born in July 1949, associate professor     

Effect of CO<Subscript>2</Subscript> concentrations on the activity of photosynthetic CO<Subscript>2</Subscript> fixation and extracelluar carbonic anhydrase in the marine diatom <Emphasis Type="Italic">Skeletonema costatum</Emphasis>

The growth and activity of photosynthetic CO2 uptake and extracellular carbonic anhydrase (CAext) of the marine diatom Skeletonema costatum were investigated while cultured at different levels of CO2 in order to see its physio-logical response to different CO2 concentrations under either a low (30 靘ol·m-2·s-1) or high (210 靘ol·m-2·s-1) irradiance. The changes in CO2 concentrations (4—31 靘ol/L) affected the growth and net photosynthesis to a greater extent under the low than under the high light re-gime. CAext was detected in the cells grown at 4 mol/L CO2 but not at 31 and 12 靘ol/L CO2, with its activity being about 2.5-fold higher at the high than at the low irradiance. Photo- synthetic CO2 affinity (1/ K1/2(CO2)) of the cells de-creased with increased CO2 concentrations in culture. The cells cultured under the high-light show significantly higher photosynthetic CO2 affinity than those grown at the low-light level. It is concluded that the regulations of CAext activity and photosynthetic CO2 affinity are dependent not only on CO2 concentration but also on light availability, and that the de-velopment of higher CAext activity and CO2 affinity under higher light level could sufficiently support the photosyn-thetic demand for CO2 even at low level of CO2.     

The giant magnetocaloric effect in Gd<Subscript>5</Subscript>Si<Subscript>2</Subscript>Ge<Subscript>2</Subscript> with low purity gadolinium

The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200℃ for 1h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J· kg^-1· K^-1 under a magnetic field change of 0-5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si4-type to the monoclinic Gd5Si2Ge2-type after high temperature heat-treatment.