Mechanoluminescence of terbium and cerium sulfates in a noble-gas atmosphere

Lines of Ne (3p-3s, 550–800 nm) and Xe (6p-6s, 800–1050 nm; 7p-6s, 475 nm) have been detected in the mechanoluminescence spectrum of terbium and cerium sulfate crystallohydrates. The luminescence of noble gas is observed jointly with the known bands of Ce³⁺ and Tb³⁺ ions and N*₂ lines. The lines corresponding to excited Xe⁺ ions (500–550 nm), indicative of achievement of electric-field strengths on the order of 10⁷ V/cm during mechanoluminescence, are also observed. It is established that, during mechanoluminescence of Tb₂(SO₄)₃ · 8D₂O in an argon atmosphere under a pressure of 1.3 atm, mechanochemical reactions of decomposition of crystallization water (D₂O) molecules cause luminescence of OD radicals; this luminescence is initiated by electron impact occurring during electrization and in discharges in crystals during destruction.     

Mechanistic and kinetics study of the gas phase reactions of methyltrifluoroacetate with OH radical and Cl atom

Theoretical investigations are carried out on the title reactions by means of ab initio and DFT methods. The optimized geometries, frequencies and minimum energy path are obtained at MPWB1K/6-31+G(d,p) level. Single point energy calculations are performed at MP2 and QCISD(T) levels of theory. Energetics were further refined by calculating the energy of the species with a high level G2(MP2) method. The rate constant of the two reactions are calculated at 298?K and 1?atm using Canonical Transition State Theory (CTST) utilizing the ab initio data obtained during the present study. The rate constant values are found to be 5.5?×?10^?14 and 5.9?×?10^?14?cm³ molecule^?1 s^?1, respectively which are in good agreement with the experimental data.     

大气压射流等离子体中O及OH自由基的发射光谱在线诊断

OH自由基及氧原子在大气化学、表面处理及化学污染物分解等方面有着重要的作用。利用发射光谱技术在线测量了大气压射流等离子体中OH自由基紫外波段与O自由基777,844 nm波段的发射光谱。研究了OH自由基与氧原子光谱强度随放电功率及放电体系中所加入的氧浓度的变化。将实验测得的OH自由基光谱图与用Lifbase数据库模拟光谱图进行比较,估算了OH自由基的转动温度。结果表明：OH自由基的转动温度随放电功率的增加而增加,随工作气体流速的增加而减小。     

Synthesis and characterization of TiO2/Ag/polymer ternary nanoparticles via surface-initiated atom transfer radical polymerization

We report on the novel ternary hybrid materials consisting of semiconductor (TiO₂), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO₂ nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO₂-POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF₃SO₃ precursor and a NaBH₄ aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO₂ nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the CO groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic-organic nanomaterials.     

Quartz crystal microbalance measurements of O/Ti and CO/Ti atom ratios on very thin Ti films

The adsorption of O₂ and CO on Ti films with thicknesses in the range 0–200 Å was investigated by quartz crystal microbalance (QCM) measurements. The O/Ti and CO/Ti ratios in the limit of zero film thickness was determined to be 1.5 and 0.5 respectively using the film thickness as a parameter. This result suggests that the oxide formed is Ti₂O₃. The Ti + O₂ results are discussed in a model where the thinnest metal films are assumed to consist of metal islands. From the model an “oxidation depth” of ≈10 Å is estimated.     

The production of hydroxyl radical in HRP-NADH-H2O/O2 systems and its application in chlorobenzene removal

The mechanism of radical generation in HRP-NADH-O2/H2O2 systems and state-change of horseradish peroxidase (HRP) was investigated by using ESR and UV measurements, and the novel enzyme-coenzymatic systems were performed to degrade chlorobenzene as a non-phenolic persistent organic pollutants. The UV results showed that compound III was produced from HRP oxidized by hydrogen peroxide with the catalysis of NADH, which would generate hydroxyl radical. The ESR results demonstrated the production of *OH and O2-. in enzyme-coenzymatic system in the presence of O2 or H2O2 with DMPO and POBN as spin-trappers, respectively. In HRP-NADH-H2O2 system, compound III was the main state of HRP in the initial 10 min, and then converted to HRP with generating hydroxyl radical; and after the addition of oxygen, the production of hydroxyl radical was promoted rapidly, as 4 times as that of the system in absence of oxygen. The addition of SOD(Zn-Cu) decreased the production of hydroxyl radical significantly, resulting from that SOD eliminated O2 reduction to O2-. by NADH and then inhibited *OH formation. The results showed that NADH could improve by about 20% enzyme activity of HRP for phenol removal. The removal of chlorobenzene with HRP-NADH-H2O2 and HRP-NADH-H2O2-O2 systems reached 24.6% and 48.2%, respectively, which was much higher than that with traditional enzymatic system (1.42%), showing a promising prospect in proposal     

Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35–80 °C. The activation energy for growth of CeO₂ nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO₂ particles in narrow size range. CeO₂ nanocrystals precipitated at 35 °C were further annealed at temperatures in the range 300–700 °C. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.     

Product polarization distribution: Stereodynamics of the reaction of atom H and radical NH

The product angular momentum polarization of the reaction of H+NH is calculated via the quasiclassical trajectory method (QCT) based on the extended London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES) at a collision energy of 5.1 kcal/mol. The calculated results of the vector correlations are denoted by using the angular distribution functions. The polarization-dependent differential cross sections (PDDCSs) demonstrate that the rotational angular momentum of the product H₂ is aligned and oriented along the direction perpendicular to the scattering plane. Vector correlation shows that the angular momentum of the product H₂ is aligned in the plane perpendicular to the velocity vector. It suggests that the reaction proceeds preferentially when the reactant velocity vector lies in a plane containing all three atoms. The orientation and alignment of the product angular momentum affects the scattering direction of the product molecules. The polarization-dependent differential cross sections (PDD-CSs) reveal that scattering is predominantly in the backward hemisphere.     

Product polarization distribution: Stereodynamics of the reaction of atom H and radical NH

The product angular momentum polarization of the reaction of H+NH is calculated via the quasiclassical trajectory method (QCT) based on the extended London-Eyring-Polanyi-Sato (LEPS) potential energy surface (PES) at a collision energy of 5.1 kcal/mol. The calculated results of the vector correlations are denoted by using the angular distribution functions. The polarization-dependent differential cross sections (PDDCSs) demonstrate that the rotational angular momentum of the product H2 is aligned and oriented along the direction perpendicular to the scattering plane. Vector correlation shows that the angular momentum of the product H₂ is aligned in the plane perpendicular to the velocity vector. It suggests that the reaction proceeds preferentially when the reactant velocity vector lies in a plane containing all three atoms. The orientation and alignment of the product angular momentum affects the scattering direction of the product molecules. The polarization-dependent differential cross sections (PDDCSs) reveal that scattering is predominantly in the backward hemisphere.      

Cu(In,Ga)Se2 thin-film solar cells with ZnS(O,OH), Zn-Cd-S(O,OH), and CdS buffer layers

Cu(In,Ga)Se₂ (CIGS) solar cell junctions prepared by chemical-bath-deposited (CBD) ZnS(O,OH), Zn-Cd-S(O,OH), and CdS buffer layers are discussed in this paper. The device performances are compared by applying CBD ZnS(O,OH), CBD Zn-Cd-S(O,OH), and CBD CdS buffer layers on similar CIGS absorbers. The CN impurities in CBD ZnS(O,OH) are identified with Fourier transform infrared spectroscopy (FTIR) techniques. The impurities containing carbon-nitrogen bonds are most likely cyanamide (NCN²⁻) or thiocyanate (SCN⁻), which resulted from the chemical reaction of thiourea and ammonia.     

LIPS技术探测CH4/空气火焰中的OH自由基

论述了激光诱导偏振光谱技术的基本原理,实验方法及其对燃烧场的测量结果.利用光谱扫描方法获得了A2∑ -X2Ⅱ(0,0)跃迁带系列吸收谱线及P1(2)谱线的线型轮廓.测量了CH4/空气预混火焰不同化学配比、不同空间位置OH自由基的相对分布.实验中通过设计精密旋转调节装置有效提高了信噪比.     

辛烷基苯酚聚氧乙烯醚与正癸醇层状液晶的有序性及层状结构

研究了层状液晶的层状结构及有序性,用偏振光显微镜法确定了辛烷基苯酚聚氧乙烯醚(TritonX 100)与正癸醇体系25℃时层状液晶的区域,绘制了部分相图,并用核磁共振氢谱法(2H NMR)进一步验证;用自旋标记电子自旋共振法测定了层状液晶分子排列的有序参数,研究结果显示,不同组分TritonX 100 /n C10H21OH/H2O体系层状液晶的超精细偶合常数基本相同,表明层状液晶中的微极性是一致的.而有序参数随着TritonX 100含量的增加而增加,随着层状液晶中水含量的增加而减少;用小角度X射线衍射方法测定了层状液晶的层间距离,并计算了水分子在层状液晶中的渗透率,其渗透率约为50%.     

Comments OH the Definitions of the Terms Sensitivity and Detection Limit

Although we agree with the general discussion concerning the definitions of the terms sensitivity and detection limit made by de Galan⁽¹⁾, we must strongly suggest that to define sensitivity as the slope of the analytical curve is not entirely practical. Moreover, we would point out that Professor de Galan is apparently guilty of the charge he has made against Willis and west⁽¹⁾, i.e., he has failed to consult all of the pertinent literature. Specifically, he omitted reference to tlie definition of sensitivity presented by Mandel and Stiehler.^(2,3) in 1954, two years prior to the first of a succession of papers on this topic by Kaiser^(4–6). Therefore, to call attention to a very practical definition of sensitivity and to clarify some pertinent related points we offer the following comments.     

Wet chemical synthesis and characterization of pure and cerium doped Dy2O3 nanoparticles

Pure and cerium doped Dy₂O₃ nanoparticles were prepared by wet chemical synthesis route. The particles were subjected to thermal, structural, morphological and optical property studies. The calcination temperature was chosen based on the decomposition of the samples revealed by TG studies. EDS and FTIR results confirmed the presence of cerium in the Dy₂O₃ system. The particle size calculated from Williamson-Hall plot was consistent with TEM results. The effect of cerium as a dopant on the UV–vis absorption and photoluminescence intensity has been studied. XRD and PL analyses demonstrate that the cerium ions uniformly substitute dysprosium sites in Dy₂O₃ lattice and hence influence the optical properties.     

掺铈YVO4晶体的发光特性及铈离子的价态分析

采用中频感应单晶炉和提拉法生长了高质量的掺Ce的YVO4晶体，并采用了两种不同的方式进行掺杂，即分别在YVO4晶体掺入了Ce2（CO3）3和CeO2，两种不同方式的掺杂浓度均为2at％．使用XRD测试了这两种晶体的物相，发现样品主要以YVO4相存在．吸收谱、荧光光谱和激发光谱的测试发现，这两种不同掺杂方式所得到的样品具有相似的光谱特性，即使用325nm的紫外线激发时，两种样品均可发出以44Onm为中心的宽带蓝光，这是来自Ce3＋离子的5d→4f的特征发射；而在46Onm的激发下，两种样品又均可发出以620nm为中心的宽带红光．通过X射线光电子能谱（XPS）对样品中的各个元素进行的测试分析，发现氧元素的1s峰分裂为529．8eV和531．8eV,这说明晶体中存在两种配位氧离子，一种是正常配位的氧离子（O2-），另一种是带空穴的配位氧离子（O-）．由ce的XPS测试结果中展现的5个5d峰推断，样品中的铈是以Ce3＋和Ce4＋两种形式共存，这种共存与两种配位氧离子的存在密切相关．我们认为，Ce：YVO4晶体的宽带红光发射来自Ce4＋-O2-的电荷迁移发光，并且它有可能因此而成为一种新型的用于白光LED的红色荧光粉．