基于概念转变对“离子反应”教学的研究

“离子反应”作为高中化学知识体系的重要知识点,对元素化合物的学习起指导作用,也是后续学习化学反应原理的基础,而在教学实践过程中发现,学生对“离子反应”这节课存在多种与科学概念不符的模糊甚至错误概念。本文主要通过对电解质的概念、离子方程式的书写等的探查、分析和探究,来帮助学生更好地认识“离子反应”。

PLC干预下的全日制化学教育硕士PCK发展的个案研究——以“离子反应”教学实践为例

通过工具性个案研究,旨在探查不同阶段的教师专业学习共同体(professional learning community,PLC)干预下职前全日制化学教育硕士的PCK发展,并在此基础上探讨所构建的PLC干预模式的合理性。对1位全日制教育硕士在教育实践过程中的多种数据类型进行收集,采用帕克等人所构建的PCK结构模型进行特征分析和比较,发现全日制教育硕士的PCK结构在经过PLC干预后有显著改善,尤其是各个要素之间的整合更加紧密;不同干预阶段对全日制教育硕士PCK发展作用方式和影响程度不尽相同。PLC干预模式能够促进职前全日制化学教育硕士的PCK发展,然而,其机理及其带来的PCK改变的持久性和稳定性还有待进一步研究。

“离子反应实验”的商酌及改进

一、存在的问题 现行高一化学教材"离子反应"的演示实验,我个人认为存在以下不足:一是影响对CuSO4溶液的蓝色干扰生成的BaSO4白色沉淀的观察;二是过滤操作需要15分钟以上,采用减压抽滤在一般教室中无法完成;采用离心沉降取清液,也影响对溶液的蓝色干扰生成的AgCl白色沉淀的观察.

A carbon material doped with both porous FeO_(x) and N as an efficient catalyst for oxygen reduction reactions

To replace precious metal oxygen reduction reaction(ORR)electrocatalysts,many transition metals and N-doped car-bon composites have been proposed in the last decade resulting in their rapid development as promising non-precious metal catalysts.We used Ketjenblack carbon as the precursor and mixed it with a polymeric ionic liquid(PIL)of[Hvim]NO_(3) and Fe(NO_(3))_(3),which was thermally calcined at 900℃ to produce a porous FeO_(x),N co-doped carbon material denoted FeO_(x)-N/C.Because the PIL of[Hvim]NO_(3) strongly combines with and disperses Fe^(3+)ions,and NO_(3)−is thermally pyrolyzed to form the porous structure,the FeO_(x)-N/C catalyst has a high electrocatalytic activity for the ORR in both 0.1 mol L^(−1) KOH and 0.5 mol L^(−1) H_(2)SO_(4) electrolytes.It was used as the catalyst to assemble a zinc-air battery,which had a peak power density of 185 mW·cm^(−2).Its superior electrocatalytic activity,wide pH range,and easy preparation make FeO_(x)-N/C a promising electrocatalyst for fuel cells and metal-air batteries.

Cation effects in electrocatalytic reduction reactions:Recent advances

Electrocatalytic reduction reactions,powered by clean energy sources such as solar energy and wind,offer a sustainable method for converting inexpensive feedstocks(e.g.,CO_(2),N_(2)/NO_(x),organics,and O_(2))into high-value-added chemicals or fuels.The design and modification of electrocatalysts have been widely implemented to improve their performance in these reactions.However,bottle-necks are encountered,making it challenging to further improve performance through catalyst development alone.Recently,cations in the electrolyte have emerged as critical factors for tuning both the activity and product selectivity of reduction reactions.This review summarizes recent advances in understanding the role of cation effects in electrocatalytic reduction reactions.First,we introduce the mechanisms underlying cation effects.We then provide a comprehensive overview of their application in electroreduction reactions.Characterization techniques and theoretical calcula-tion methods for studying cation effects are also discussed.Finally,we address remaining challeng-es and future perspectives in this field.We hope that this review offers fundamental insights and design guidance for utilizing cation effects,thereby advancing their development.

Coverage Dependent Dissociative Adsorption of HCl on Au(111)

Dissociative adsorption of HCl on Au(111)has become one of unsolved puzzles in surface chemistry.Despite tremendous efforts in the past years,varioustheoretical models still greatly overestimate the zero-coverage initial sticking probabilities(So).To find the origin of the large experiment-theory discrepancy,we have revisited the dissociative adsorption of HCl on Au(111)with a newly designed molecular beam-surface apparatus.The zero-coverage So derived from Cl-coverage measurements with varying HCl doses agree well with previous ones.However,we notice a sharp change of the coverage/dose slope with the HCl dosage at the low coverage regime,which may result in some uncertainties to the fitted So value.This seems consistent with a coverage-dependence of the dissociation barrier predicted by density functional theory at low Cl-coverages.Our results reveal the potential inconsistency of utilizing simulations with finite coverage to compare against experimental data with zero coverage in this system,and provide guidance for improving both experiment and theory in this regard.

Separation of Ions from Volatile Organic Compounds Using High-Field Asymmetric Waveform Ion Mobility Spectrometry-Mass Spectrometer

A combination of high-field asymmetric waveform ion mobility spectrometry （FAIMS） with mass spectrometer （MS） was analyzed. FAIMS separates ions from the volatile organic compounds in the gas-phase as an ion-filter for MS. The sample ions were created at ambient pressure by ion source, which was equipped with a 10.6 eV UV discharge lamp （A=116.5 nm）. The drift tube of FAIMS is composed of two parallel planar electrodes and the dimension is 10 mm×8 mm×0.5 mm. FAIMS was investigated when driven by the high-filed rectangular asymmetric waveform with the peak-to-peak voltage of 1.36 kV at the frequency of 1 MHz and the duty cycle of 30%. The acetone, the butanone, and their mixture were adopted to characterize the FAIMS-MS. The mass spectra obtained from MS illustrate that there are ion-molecular reactions between the ions and the sample neutral molecular. And the proton transfer behavior in the mixture of the acetone and the butanone is also observed. With the compensation voltage tuned from -30 V to 10 V with a step size of 0.1 V, the ion pre-separation before MS is realized.

Electrochemical oxidation of aniline by a novel Ti/TiO_xH_y/Sb-SnO_2 electrode

Electrochemical oxidation of aniline in aqueous solution was investigated over a novel Ti/TiOxHy/Sb-SnO2 electrode prepared by the electrodeposition method.Scanning electron microscopy,X-ray diffraction,and electrochemical measurements were used to characterize its morphology,crystal structure,and electrochemical properties.Removal of aniline by the Ti/TiOxHy/Sb-SnO2electrode was investigated by ultraviolet-Visible spectroscopy and chemical oxygen demand（COD）analysis under different conditions,including current densities,initial concentrations of aniline,pH values,concentrations of chloride ions,and types of reactor.It was found that a higher current density,a lower initial concentration of aniline,an acidic solution,the presence of chloride ions（0.2wt%NaCl）,and a three-dimensional（3D） reactor promoted the removal efficiency of aniline.Electrochemical degradation of aniline followed pseudo-first-order kinetics.The aniline（200 mL of 100mg·L-（-1）） and COD removal efficiencies reached 100%and 73.5%,respectively,at a current density of 20 mA·cm-（-2）,pH of 7.0,and supporting electrolyte of 0.5 wt%Na2SO4 after 2 h electrolysis in a 3D reactor.These results show that aniline can be significantly removed on the Ti/TiOxHy/Sb-SnO2electrode,which provides an efficient way for elimination of aniline from aqueous solution.

Synthesis of α-Fe_2O_3@SnO_2 core-shell nanoparticles via low-temperature molten salt reaction route

A cost-effective carbon-free nanocoating strategy was developed for the synthesis of ultra-fine SnO2 coatingα-Fe2O3 core-shell nanoparticles. This strategy only involves a two-step molten salt reaction at low temperature of 300 °C. The as-preparedα-Fe2O3@SnO2 core-shell nanocomposites show enhanced electrochemical performances than the bareα-Fe2O3 nanoparticles. This involved metal oxide nanocoating method is easy to be carried out, and the heat treatment temperature is much lower than that of other traditional solid-state annealing method and many carbon or metal oxide nanocoating methods. The molten salt method may also be used to produce other metal oxides coating nanostructures as the electrode materials for lithium-ion batteries.

Experimental and Theoretical Study of Hydrogen Atom Abstraction from C2H6 and C4H10 by Zirconium Oxide Clusters Anions

The reactions of anionic zirconium oxide clusters ZrxOy- with C2H6 and C4H10 are investi-gated by a time of flight mass spectrometer coupled with a laser vaporization cluster source.Hydrogen containing products Zr2O5H- and Zr3O7H- are observed after the reaction. Den-sity functional theory calculations indicate that the hydrogen abstraction is favorable in the reaction of Zr2O5- with C2H6, which supports that the observed Zr2O5H- and Zr3O7H- are due to hydrogen atom abstraction from the alkane molecules. This work shows a newpossible pathway in the reaction of zirconium oxide cluster anions with alkane molecules.

Optimization of Plasma Etching Parameters and Mask for Silica Optical Waveguides

Optical waveguides in silica-on-silicon are one of the key elements in optical communications.The processes of deep etching silica waveguides using resist and metal masks in RIE plasma are investigated.The etching responses,including etching rate and selectivity as functions of variation of parameters,are modeled with a 3D neural network.A novel resist/metal combined mask that can overcome the single-layer masks’ limitations is developed for enhancing the waveguides deep etching and low-loss optical waveguides are fabricated at last.

Electron Attachment Studies for CHCl3 Using Ion Mobility Spectrometry

The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry （CD-IMS）. The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/（molecules s） to 8.24×10-9 cm3/（molecules s） as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region, the attachment rate constants are also detected at different sample concentration. The ionmolecule reaction rate constants for the further reaction between Cl^- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS.

Mechanistic Investigation on the Reaction of O- with CH3CN Using Density Functional Theory

The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and transition states involved in this reaction have been optimized at the （U）B3LYP/6-31＋G（d,p） level, and then their accurate relative energies have been improved using the G3MP2B3 method. The potential energy profile is confirmed via intrinsic reaction coordinate calculations of transition states. Four possible production channels are examined respectively, as H＋ transfer, H-atom transfer, H2＋ transfer, and bi- molecular nucleophilic substitution （SN2） reaction pathways. Based on present calculations, the H2＋ transfer reaction is major among these four channels, which agrees with previous experimental conclusions.

C-S Activation of CS2 by Nb＋ in Gas Phase

The reaction of Nb＋ with CS2, producing cationic transition-metal sulfide and CS, was taken as a representative example to elucidate the overall mechanism of reactions of second- row early transition metal ions with CS2. The reactions in both triplet and quintet state were studied by using the UB3LYP density functional method with the Stuttgart pseudo potentials and corresponding basis sets for Nb＋ and the standard 6-311＋G（2d） basis sets for C and S. The geometries for reactants, the transition states, and the products were completely optimized. All the transition states were verified by vibrational analysis and intrinsic reaction coordinate calculations. The results show that the reaction mechanism between niobium ion and CS2 is an insertion-elimination mechanism. Intersystem crossing may occur in the reaction Nb＋ with CS2 and a minimum energy crossing point was found.

Fabrication of Ultra Deep Electrical Isolation Trenches with High Aspect Ratio Using DRIE and Dielectric Refill

A novel technique to fabricate ultra deep high aspect ratio electrical isolation trenches with DRIE and dielectric refill is presented.The relationship between trench profile and DRIE parameters is discussed.By optimizing DRIE parameters and RIE etching the trenches’ opening,the ideal trench profile is obtained to ensure that the trenches are fully refilled without voids.The electrical isolation trenches are 5μm wide and 92μm deep with 0.5μm thick oxide layers on the sidewall as isolation material.The measured I-V result shows that the trench structure has good electrical isolation performance:the average resistance in the range of 0～100V is more than 10 11Ω and no breakdown appears under 100V.This isolation trench structure has been used in fabrication of the bulk integrated micromachined gyroscope,which shows high performance.

Triangular Au-Ag framework nanostructures prepared by multi-stage replacement and their spectral properties

Triangular Au-Ag framework nanostructures （TFN） were synthesized via a multi-step galvanic replacement reaction （MGRR） of single-crystalline triangular silver nanoplates in a chlorauric acid （HAuCl4） solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy（TEM）, energy-dispersive X-ray spectrometry （EDX）, and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance （SPR） absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering （SERS）.

Nanosized Spinel Li4Ti5O12 Anode Material Prepared by Gel-polymer Method using Furfuryl Alcohol as Polymerizable Solvent

Nanosized Li4Ti5O12 powders are synthesized by a polymerization-based method using ti- tanium butoxide and lithium nitrate as precursors and furfuryl alcohol as a polymerizable solvent. The prepared samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Braunauer-Emmett-Teller （BET） analysis. The electrochemical performances of these Li4Ti5O12 powders are also studied. The effect of different surfactants including citric acid, polyvinylpyrrolidone, and cetyltrimethyl ammonium bromide on the structure and properties is also investigated. It is found that pure spinel phase of Li4Ti5O12 is obtained at an annealing temperature of 700 ℃ or higher. The use of surfactants can improve the powder morphology of nanosized particles with less agglomeration. With suitable annealing temperature and the addition of surfaetant, Li4Ti5O12 powders with high BET surface area and favorable electrochemical performance can be obtained.

Experimental Study on the Footing Effect for SOG Structures Using DRIE

This paper experimentally studies the effects of the conductivity of a silicon wafer and the gap height between silicon structures and glass substrate on the footing effect for silicon on glass （SOG） structures in the deep reactive ion etching （DRIE） process. Experiments with gap heights of 5,20, and 50μm were carried out for performance comparison of the footing effect. Also,two kinds of silicon wafers with resistivity of 2-4 and 0.01-0. 0312Ω· cm were used for the exploration. The results show that structures with resistivity of 0.01 - 0. 0312Ω· cm have better topography than those with resistivity of 2-4Ω· cm; and structures with 50μm-high gaps between silicon structures and glass substrate suffer some- what less of a footing effect than those with 20μm-high gaps,and much less than those with Stem-high gaps. Our theoretical analysis indicates that either the higher conductivity of the silicon wafer or a larger gap height between silicon structures and glass substrate can suppress footing effects. The results can contribute to the choice of silicon type and optimum design for many microsensors.

Ionic palladium complex as an efficient and recyclable catalyst for the carbonylative Sonogashira reaction

The neutral palladium（Ⅱ） complex bis-[1-（5＇-diphenylphosphinothiazol-2＇-yl）-imidazolyl]dichloropalladium（Ⅱ）（1A） ligated by thiazolylimidazolyl-based phosphine（L1） in which thiazolylimidazolyl acted as an S- and N-donor provider with weak coordinating nature,and the ionic complex bis-[1-（5＇-diphenylphosphinothiazol-2＇-yl）-3-methylimidazolium]dichloropalladium（Ⅱ） trifluoromethanesulfonate（2A） ligated by thiazolylimidazolium-based phosphine（L2） after quaternization of L1 using methyl trifluoromethanesulphonate were synthesized.It was found that the introduced positive charges and strong electron-withdrawing effect in 2A not only led to changes in the configuration and structural stability of the complex,but also lowered its catalytic performance in carbonylative Sonogashira reactions.These effects reveal the important role of the N-donor in 1A.In addition,as an ionic palladium complex,2A combined with the room-temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate could be recycled eight times as the catalyst in carbonylative Sonogashira reactions without detectable metal leaching.

Predicting Rate Constants for Nucleophilic Reactions of Amines with Diarylcarbenium Ions Using an ONIOM Method

The rate constants of the nucleophilic reactions between amines and benzhydrylium ions were calculated using first-principles theoretical methods. Solvation models including PCM, CPCM, and COSMORS, as well as different types of atomic radii including UA0, UAKS, UAHF, Bondi, and UFF, and several single-point energy calculation methods （B3LYP, B3P86, B3PW91, BHANDH, PBEPBE, BMK, M06, MP2, and ONIOM method） were examined. By comparing the correlation between experimental rate constants and the calculated values, the ONIOM（CCSD（T）/6-311＋＋G（2df,2p）：B3LYP/6-311＋＋G（2df,2p））//B3LYP/6- 31G（d）/PCM/UFF） method was found to perform the best. This method was then employed to calculate the rate constants of the reactions between diverse amines and diarylcarbenium ions. The calculated rate constants for 65 reactions of amines with diarylcarbenium ions are in agreement with the experimental values, indicating that it is feasible to predict the rate constant of a reaction between an amine and a diarylcarbenium ion through ab initio calculation.