氧化还原树脂的合成及其氧化还原性能

本文主要叙述了以国产717强碱性阴离子交换树脂为基体,采用甲醛与对苯二酚、邻苯二酚、连苯三酚和2,7-萘二酚等聚合生成氧化还原树脂,它们的氧化还原容量分别为5.3,5.4和5.2meq/g-干树脂.文中还介绍了本类树脂的氧化还原电位测定方法,并据此研究和测定了对苯二酚、邻苯二酚和连苯三酚型树脂的氧化还原电位,这些电位的测定结果与其氧化还原实验事实相符.也研究了多种氧化剂和还原剂与自制树脂的交换性能,讨论了这些树脂容量与交换性能的关系.应用所合成的新树脂进行了从硝酸银废液中回收银和对硫化氢试行氧化脱硫处理试验,效果良好.     

基于文献分析的“氧化还原反应”概念教学逻辑

以15篇有关“氧化还原反应”的课例研究文献为研究对象,基于内容分析法归纳出4种主要的教学逻辑：“分类标准直给型”“分类标准批判型”“反应本质揭示型”“知识演绎批判型”。从“知识是什么”“知识是如何被理解的”2个维度对4种教学逻辑进行评析,以反思氧化还原反应教学研究的发展及其局限。     

蔗糖燃烧实验的创新改进*

现行教材采用蔗糖和小苏打为原料进行“燃糖成蛇”实验,存在“蛇”生长长度较短和生长速率较慢等问题,降低了该实验的趣味性和可观赏性。在分析小苏打的作用基础上,系统探究了析氧物质替代小苏打进行“燃糖成蛇”实验的创新改进。结果表明,以高锰酸钾和氯酸钠混合物替代小苏打进行实验,“蛇”的长度和生长速率大大提高。改进后的实验,实验现象更加明显,趣味性、可观赏性和探究性增强。     

高中化学“电负性”的项目式教学*——甲醛的危害与去除

电负性是高中化学选择性必修课程“物质结构与性质”模块的重要概念。本课例采用“项目式教学”的方式,在对“甲醛的危害与去除”的分析、讨论与实验过程中,加深对电负性概念的理解,同时尝试利用电负性分析与预测物质的化学性质,体会电负性概念的使用价值。     

高中化学“氧化还原反应的应用”项目式教学——设计过氧化氢使用注意事项标签

以“设计过氧化氢使用注意事项标签”为项目主题,开展高中化学“氧化还原反应的应用”教学。学生通过说明书对比发现问题,完成“探究过氧化氢能否与氧化性物质混用”“探究过氧化氢为何不能与还原性物质混用”“探究过氧化氢起消毒作用原理”等3个主项目任务及“寻找日常生活中常见消毒剂”的拓展任务,完成过氧化氢性质的预测及验证,在探究过程中建构并应用价性模型,形成从化合价角度认识物质氧化性或还原性的思路方法,认识氧化还原反应的重要意义。本教学设计为单课时微项目,学生思维的开放度稍弱,可以适当延长课时。     

“乙醛溶液的电解”课堂演示实验研究

针对中学化学实验教学中电解有机物的空白现状,应用Schiff试剂定性检测电解液中乙醛浓度的方法,开发了一个电解乙醛的课堂演示实验。该实验将有机化学中的氧化还原反应与电解过程相结合,以此发展学生对电解池工作原理以及有机化学反应机理的认识。通过实验探究,培育学生“科学探究与创新意识”和“科学态度与社会责任”的学科素养。     

环金属钌配合物的合成、结构多样性及氧化还原调控

环金属钌配合物具有良好的氧化还原和光物理性质,在诸多光电领域如染料敏化太阳能电池、电致变色、电子转移等方面具有重要应用。环金属钌配合物的合成方法主要包括“后期金属化”、“前期金属化”、“转金属化”三种方法。环金属配合物具有丰富的结构多样性。环金属配合物由环金属配体和辅基配体与金属螯合形成。环金属配体包括N^∧C、N^∧N^∧C、N^∧C^∧N和C^∧C^∧C-类型多齿配体。辅基配体主要包括吡啶、咪唑、三唑、嘧啶等杂环。碳-金属键的引入大大降低了钌配合物的氧化还原电位。通过改变环金属配体和辅基配体的结构,可以对金属的氧化还原电位进行有效调控。金属钌配合物的氧化还原电位对敏化电池的性能以及电子转移的过程具有重要的影响。     

“蓝瓶子”实验再探究*

利用SPSS 25.0统计软件对“蓝瓶子”实验进行正交实验设计,通过统计学分析得出最佳实验条件。利用氧化还原传感器(ORP)对“蓝瓶子”振荡体系的电极电势变化曲线进行分析,并针对蓝色的产生和消失过程设计3组对比实验深入探究,阐明其反应原理,意在引导学生深刻理解趣味实验现象背后的微观反应本质。     

“铜元素化合物”的高三线上主题式复习*

以高三复习课“铜元素化合物”的教学为例,基于主题教学思想,从“价类二维图”出发,引导学生从物质类别、氧化还原和化学平衡等多角度认识元素化合物间的相互转化,实现了主题内容的关联与进阶,促进了学生思维能力的提升和学科观念的建构。本节课是网络直播课,采用“腾讯课堂”平台,学生可以连麦回答问题,学生设计的实验方案发布在班级微信上,由教师共享屏幕,则所有学生可见。     

趣味化学实验“点火成蛇”的探究*

通过多年的实验探究发现,趣味化学实验“点火成蛇”,可以不用催化剂,直接点燃蔗糖和碳酸氢钠的混合物,就可以得到实验结果。以前所说的“催化剂”,实际上只起了一个吸附酒精集中加热反应物的作用,使实验现象更加明显,而对化学反应并没有“催化”作用。建议普通实验室用沙子或细黄土在铁架台底座上进行这个实验。     

Snake-cage redox polyelectrolytes based on anion-exchange resins

Redox polyelectrolytes are described where the polyphenols hydroquinone, pyrogallol, and catechol were absorbed as counterions by a strong base anion-exchange resin in the hydroxide form, and then polymerized by refluxing in 1:1 mole ratio with formaldehyde in aqueous solution, thus producing a “snake-cage” configuration. The redox capacities of the resins were determined by oxidation with iodine/iodide solution, and found to approach theoretical at between 5.1 and 5.4 meq/g. The rate of oxidation was found to be controlled by diffusion within the particles. Fe³⁺ was unsatisfactory as an oxidant, owing to the exclusion effect by the fixed positive charges in the resin matrix. At low pH the resin beads were light to reddish brown in the reduced form, black in the oxidized form. The resins, especially that based on catechol, showed much greater stability in 1N NaOH solution than simple polyphenol–formaldehyde condensation polymers.     

Immobilization of tyrosinase on poly(indole-5-carboxylic acid) evidenced by electrochemical and spectroscopic methods

A conducting, polymeric film of poly(indole-5 carboxylic acid) has been prepared by electrochemical polymerization for covalent immobilization of an enzyme belonging to the family of phenoloxidases-tyrosinase. The polymer was characterized by cyclic voltammetry, UV-VIS and Raman spectroscopy in a buffer solution. As the polymer contains pendant carboxylic groups one-step carbodiimide method was used to immobilize tyrosinase on the polymer matrix. Immobilization of tyrosinase was confirmed by surface enhanced resonance Raman scattering spectra (SERRS) and by cyclic voltammetry as well. Tyrosinase was shown to retain its biological activity when being immobilized on the polymer surface. As proved by the electrochemical and spectroelectrochemical (UV-VIS) experiments, tyrosinase covalently bonded to the polymer matrix effectively catalyzes oxidation of catechol. The reduction current of o-quinones was measured as a function of catechol concentration. The linear dependence was found to be 15 microM of catechol with sensitivity of 250 mA/M cm2.     

Electrochemical oxidation of catechol at poly(indole-5-carboxylic acid) electrode

In this work we examined the electrochemical properties of poly(indole-5-carboxylic acid), PIn₅COOH. The polymer was produced by electrochemical polymerisation using cyclic voltammetry (CV). It was shown that PIn₅COOH is electroactive in aqueous solutions showing two redox processes in acidic solution and one redox process in solutions with pH > 4. The oxidation of catechol (CT) on Pt/In₅COOH modified electrodes was investigated by cyclic voltammetry (CV) and rotating disc electrode (RDE) voltammetry. It was established that CT was oxidised only after the oxidation of polymer film was initiated and that polymer significantly enhanced the oxidation and reduction peak currents in comparison with bare Pt electrode. The variation of peak currents (i _pa, i _pc) as a function of CT concentration was found to be linear up to 6 mM. Experiments with a rotating disk electrode show that the oxidation reaction of catechol occures not only at the polymer/electrolyte interface but also in the polymer film.     

Minimizing analyte electrolysis in electrospray ionization mass spectrometry using a redox buffer coated emitter electrode

An emitter electrode with an electroactive poly(pyrrole) (PPy) polymer film coating was constructed for use in electrospray ionization mass spectrometry (ESI‐MS). The PPy film acted as a surface‐attached redox buffer limiting the interfacial potential of the emitter electrode. While extensive oxidation of selected analytes (reserpine and amodiaquine) was observed in positive ion mode ESI using a bare metal (gold) emitter electrode, the oxidation was suppressed for these same analytes when using the PPy‐coated electrode. A semi‐quantitative relationship between the rate of oxidation observed and the interfacial potential of the emitter electrode was shown. The redox buffer capacity, and therefore the lifetime of the redox buffering effect, correlated with the oxidation potential of the analyte and with the magnitude of the film charge capacity. Online reduction of the PPy polymer layer using negative ion mode ESI between analyte injections was shown to successfully restore the redox buffering capacity of the polymer film to its initial state. Published in 2010 by John Wiley & Sons, Ltd.     

Switchable Nonlinear Optical Properties of η(5)-Monocyclopentadienylmetal Complexes: A DFT Approach

Density functional theory (DFT) calculations have been carried out to investigate the switching of the second-order nonlinear optical (NLO) properties of η(5)-monocyclopentadienyliron(II) and ruthenium(II) model complexes presenting 5-(3-(thiophen-2-yl)benzo[c]thiophen-1-yl)thiophene-2-carbonitrile as a ligand. The switching properties were induced by redox means. Both oxidation and reduction stimulus have been considered, and calculations have been performed both for the complexes and for the free benzo[c]thiophene derivative ligand in order to elucidate the role played by the organometallic fragment on the second-order NLO properties of these complexes. B3LYP, CAM-B3LYP, and M06 functionals were used for our calculations. The results show some important structural changes upon oxidation/reduction that are accompanied by significant differences on the corresponding second-order NLO properties. TD-DFT calculations show that these differences on the second-order NLO response upon oxidation/reduction are due to a change in the charge transfer pattern, in which the organometallic iron and ruthenium moieties play an important role. The calculated static hyperpolarizabilities were found to be strongly functional dependent. CAM-B3LYP, however, seems to predict more reliable structural and optical data as well as hyperpolarizabilities when compared to experimental data. The use of this functional predicts that the studied complexes can be viewed as acting as redox second-order NLO switches, in particular using oxidation stimulus. The β(tot) value of one-electron oxidized species is at least ～8.3 times (for Ru complex) and ～5.5 times (for Fe complex) as large as that of its nonoxidized counterparts.     

Voltammetric and waveguide spectroelectrochemical characterization of ultrathin poly(aniline)/poly(acrylic acid) films self-assembled on indium-tin oxide

We report on the spectroelectrochemical characterization of conducting polymer (CP) films, composed of alternating layers of poly(aniline) (PANI) and poly(acrylic acid) (PAA), deposited on ITO-coated, planar glass substrates using layer-by-layer self-assembly. Absorbance changes associated with voltammetrically induced redox changes in ultrathin films composed of only two bilayers (ITO/PANI/PAA/PANI/PAA) were monitored in real time using a unique multiple reflection, broadband attenuated total reflection (ATR) spectrometer. CP films in contact with pH 7 buffer undergo a single oxidation/reduction process, with ca. 12.5% of the aniline centers in the film being oxidized and reduced. The ATR spectra indicate that during an anodic sweep, the leucoemeraldine form of PANI in these films is oxidized to generate both the emeraldine and pernigraniline forms simultaneously. A comparison of the behavior observed during anodic and cathodic sweeps suggests that the rate of oxidation is limited by structural changes in the polymer film originating in electrostatic repulsion between positively charged PANI chains.     

Electrochemistry of surface-grafted stimulus-responsive monolayers of poly(ferrocenyldimethylsilane) on gold

Poly(ferrocenyldimethylsilane)s with various degrees of polymerization and featuring a thiol end group were chemically end-grafted onto gold substrates by self-assembly, forming redox-active monolayers. The monolayers were characterized by contact angle measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Layer thickness values were determined by surface plasmon resonance spectroscopy and ellipsometry. The electrochemical properties of these films in aqueous NaClO(4) were studied using cyclic voltammetry (CV), differential pulse voltammetry, chronoamperometry, and chronocoulometry. Cyclic voltammograms showed two reversible redox peaks, indicating a stepwise oxidation of the electroactive sites. The first oxidation step showed reversible behavior at low scan rates and quasi-reversible behavior at higher scan rates. Peak currents (i(p)) plotted against the square root of scan rates (v(1/2)) for the first oxidation peak and for the corresponding reduction peak exhibited a linear dependence, indicating that the oxidation process in the first step is controlled by the diffusion of counterions into the polymer film. For the second oxidation peak and the corresponding reduction peak, i(p) varied linearly with v. This redox behavior is characteristic of surface-immobilized electroactive layers. The higher reversibility of the second oxidation and reduction waves in the CV experiments was explained from the solvation of the surface-grafted poly(ferrocenylsilane) (PFS) chains, which depends on the degree of oxidation. Oxidized PFS films are swollen in the aqueous electrolyte solutions, leading to a higher segmental mobility of the polymer chains and a much increased counterion mobility within the film. Kinetic parameters for the redox processes were obtained from chronocoulometry experiments.     

羧甲基壳聚糖/聚乙烯醇/甘油环氧树脂蛇笼型复合螯合膜的制备及对金属离子的吸附性能

以交联甘油环氧树脂交联的聚乙烯醇(PVA)为笼树脂，羧甲基壳聚糖(CCTS)为蛇树脂制备了具有蛇笼结构的复合螯合膜，研究了其对Cu^2 、Ni^2 、Pb^2 、Fe^3 、Zn^2 ，Hg”^2 、Cd^2 等金属离子的吸附性能，研究表明，该树脂对Cu^2 、Ni^2 、Pb^2 有较好的吸附性能，其中PVA是对Cu^2 的吸附的主要贡献者，而CCTS则是在对Ni^2 的吸附中起主要作用。该树脂可以用于含Cu^2 废水的处理。     

Modeling of oxidative development in PMR-15 resin

A multidisciplinary approach focused on models and processes to predict the performance and life expectancy of high-temperature polymer matrix composite (HTPMC) materials used in a variety of aerospace applications is being developed. Emphasis is on the implementation and extension of hierarchical models to represent the polymer behavior/properties as a function of the degradation state. Neat resin specimens of high-temperature polyimide PMR-15 have been evaluated for various aging conditions. Characterization of the properties of the polyimide is focused on development of a constitutive law for use in a micromechanical analysis to predict the behavior of PMR-15 reinforced composites. Thermo-oxidative aging is simulated with a diffusion-reaction model in which temperature, oxygen concentration and weight loss effects are considered. One-dimensional simulations illustrate oxidative layer growth for neat resin specimens. Comparisons and correlations with experimental observations of oxidation layer growth are presented.     

Spatially resolved Raman spectroelectrochemistry of solid-state polythiophene/viologen memory devices

A three terminal molecular memory device was monitored with in situ Raman spectroscopy during bias-induced switching between two metastable states having different conductivity. The device structure is similar to that of a polythiophene field effect transistor, but ethylviologen perchlorate was added to provide a redox counter-reaction to accompany polythiophene redox reactions. The conductivity of the polythiophene layer was reversibly switched between high and low conductance states with a "write/erase" (W/E) bias, while a separate readout circuit monitored the polymer conductance. Raman spectroscopy revealed reversible polythiophene oxidation to its polaron form accompanied by a one-electron viologen reduction. "Write", "read", and "erase" operations were repeatable, with only minor degradation of response after 200 W/E cycles. The devices exhibited switching immediately after fabrication and did not require an "electroforming" step required in many types of memory devices. Spatially resolved Raman spectroscopy revealed polaron formation throughout the polymer layer, even away from the electrodes in the channel and drain regions, indicating that thiophene oxidation "propagates" by growth of the conducting polaron form away from the source electrode. The results definitively demonstrate concurrent redox reactions of both polythiophene and viologen in solid-state devices and correlate such reactions with device conductivity. The mechanism deduced from spectroscopic and electronic monitoring should guide significant improvements in memory performance.