A novel silane coupling agent with peroxy groups used as an initiator in the graft polymerization of AN or MMA on nano-TiO<Subscript>2</Subscript>

A novel peroxy group-containing silane coupling agent was synthesized and anchored on the surface of titanium dioxide nanoparticles (nano-TiO₂) to form an immobilized-initiator-modified nano-TiO₂ species. In this study, the kinetic parameters of the peroxy group-containing silane were tested and assessed using DSC. The pre-exponential factor (A_d) was 8.973?×?10⁸ and the activation energy (E_a) was 80.736 kJ mol^?1. Moreover, the empirical Arrhenius equation was determined to be ln K_d?=???80.736/RT?+?ln(8.973?×?10⁸). To obtain continuous polymers, acrylonitrile (AN) and methyl methacrylate (MMA) were polymerized using the novel peroxy group-containing silane and FeSO₄ as an initiator system. The number average molecular weights (M_n of PAN?=?3×10⁴ and M_n of PMMA?=?1.4?×?10⁵) and polydispersity indexes (PDI of PAN?=?2.76 and PDI of PMMA?=?1.65) were determined by GPC. It was suggested that the redox initiation system can generate highly reactive species on the surfaces of inorganic nanoparticles. The nano-TiO₂-grafted polymers were successfully obtained.     

大气丙酮碳同位素组成测定方法的研究

利用气相色谱/燃烧/同位素比值质谱(GC/C/IRMS)分析技术,研究了具有不同碳同位素组成的丙酮与衍生剂2,4-二硝基苯肼(DNPH)的液相反应及其相应的气相反应实验过程中的碳同位素效应,探讨了以该方法测定大气丙酮碳同位素组成的可行性。研究结果表明,在衍生化过程中不会产生碳同位素分馏。本实验通过测定衍生剂DNPH与相应的衍生物的碳同位素值,大气中丙酮碳同位素组成通过质量平衡方程计算而求得。采用该方法对大气丙酮碳同位素组成的初步测定结果表明,具有相同排放源的大气丙酮碳同位素比值基本不变。本方法实验重现性好,测定精度高,可以用于分析大气丙酮的排放源研究。     

Reversible Switching CuII/CuI Single Sites Catalyze High-rate and Selective CO2 Photoreduction

Herein, we first design a model of reversible redox-switching metal–organic framework single-unit-cell sheets, where the abundant metal single sites benefit for highly selective CO₂ reduction, while the reversible redox-switching metal sites can effectively activate CO₂ molecules. Taking the synthetic Cu-MOF single-unit-cell sheets as an example, synchrotron-radiation quasi in situ X-ray photoelectron spectra unravel the reversible switching Cu^II/Cu^I single sites initially accept photoexcited electrons and then donate them to CO₂ molecules, which favors the rate-liming activation into CO₂^δ−, verified by in situ FTIR spectra and Gibbs free energy calculations. As an outcome, Cu-MOF single-unit-cell sheets achieve near 100 % selectivity for CO₂ photoreduction to CO with a high rate of 860 μmol g⁻¹ h⁻¹ without any sacrifice reagent or photosensitizer, where both the activity and selectivity outperform previously reported photocatalysts evaluated under similar conditions.     

Mechanism of N-octadecyl-N1-maleoyl-L-phenylalanine self-assembled into supramolecular structures

N-Octadecyl-N1-maleoyl-L-phenylalanine （ODMA-L-Phe） was synthesized through the condensation, deprotection and acid- ylation reaction of BOC-L-phenylalanine, octadecylamine and maleic anhydride. ODMA-L-Phe can self-assemble in some organic solvents and turned them into thermally reversible physical supramolecular organogels. The morphology of ODMA-L-Phe aggregates was characterized by polarized optical microscopy （POM） and field emission scanning electron microscope （FE-SEM）. The aggregates of ODMA-L-Phe were needle-like fibrils with diameters of approximately 100-200 nm. The mechanism of ODMA- L-Phe self-assembly in organic solvents was investigated using XH NMR and circular dichroism （CD）. The results indicated that hydrogen bonding was one of the main driving forces for the self-assembly of ODMA-L-Phe.     

Differential and Integral Isoconversional Non‐linear Methods and Their Application to Energetic Materials. III. Non‐isothermal Decomposition Reaction Kinetics of Benzotrifuroxan

The thermal behaviour and decomposition reaction kinetics of benzotrifuroxan (BTF) were determined by TG and DSC techniques. The kinetic parameters of the exothermic decomposition reaction in a temperature programmed mode (the apparent activation energy Ea and pre-exponential factor A) were calculated by a single non-isothermal DSC curve. The E values calculated using the Kissinger and Flynn-Wall-Ozawa equations and integral isoconversional non-linear equations were used to check the validity of activation energy by a single non-isothermal DSC curve. The results show that the kinetic model function in integral form and the values of Ea and A of the decomposition reaction of BTFare , 109.95 kJ•mol－1 and 108.16 s－1, respectively. The values of ∆S≠, ∆H≠ and ∆G≠ of this reaction are －93.15 J•mol－1•K－1, 150.72 kJ•mol－1 and 153.15 kJ•mol－1, respectively. The critical temperature of thermal explosion of BTF is 257.33 ℃.     

Trends in speciation analysis of vanadium in environmental samples and biological fluids--a review

A comprehensive review is presented addressing recent trends in the speciation and determination of vanadium in environmental and biological sample matrices, including important analytical aspects such as sample clean up, pre-concentration and method development. Methodology based on both separation and spectroscopic techniques for the determination of vanadium speciation is discussed. A brief outline of analytical principles, together with an overview of the recent developments and applications of vanadium speciation determination is included. The newer methods for detecting metal ions including hyphenated spectroscopic techniques and sample preparation schemes are also discussed.     

Coordination mechanism,characterization, and photoluminescence properties of spinel ZnAl<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles prepared by a modified polyacrylamide gel route

Single-phase ZnAl₂O₄ nanoparticles with the spinel structure were successfully synthesized using a modified polyacrylamide gel method according to the atomic ratio of Zn to Al = 1: 1.8. The as-prepared samples were characterized by means of X-ray powder diffraction (XRD), thermogravimetric analysis (TG), differential scanning calorimetry analysis (DSC), field-emission scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) spectra. XRD patterns show that the pure phase of ZnAl₂O₄ is obtained after heating the xerogel at 900°C for 5 h in air. The SEM images reveal that the ZnAl₂O₄ nanoparticles have a narrow particle size distribution and the average particle size is around 45 nm. Photoluminescence (PL) spectra demonstrate the single phase ZnAl₂O₄ nanoparticles have an emission peak located at 469 nm when excited by 350 nm light. The phase structure, coordination mechanism, and luminescence properties have been discussed on the basis of the experimental results.