动力学分光光度法同时测定微量磷、硅、砷

依据磷、硅、砷和钼酸盐形成的杂多酸被还原剂还原的反应速率不同,建立了同时测定此3个元素的动力学分光光度法.本法成功地应用于生铁样中微量磷、砷、硅的同时测定,结果满意.     

杂多钼酸盐中心原子(P,As)对催化氧化性能的影响

合成了具有不同中心原子Keggin阴离子结构的杂多钼酸盐M₃(XMo₁₂O₄₀)(M=K⁺,NH₄⁺,X=P,As)。利用FTIR、TPD、ESR和CV等手段考查了各化合物的氧化还原性质和酸性。比较两种不同中心原子的杂多钼酸盐,其中砷为中心原子的更容易被还原及有较低的酸强度,这类催化剂对异丁醛氧化脱氢活性较低,而对异丁醛氧化为甲基丙烯酸有较高的选择性,中心原子对活性和选择性的影响分别与它们氧化还原电位的升高关联,也与更易给出轿式氧有关。     

流动注射速差动力学化学发光分析Ⅱ微量磷的快速测定

本文根据磷钼杂多酸可直接氧化Ｌｕｍｉｎｏｌ产生化学发光的特性，建立了磷的流动注射化学发光分析方法。利用磷钼杂多酸、硅钼杂多酸、砷钼杂多酸形成速率的差异，在磷、硅、砷共存时，可不经任何分离，实现对水样和钢样中磷的快速测定。该法检出限为３．６×１０－５ｇ／Ｌ，线性范围２．０×１０－４～１．０×１０－２ｇ／Ｌ，相对标准偏差为１．８％（磷浓度１．０×１０－３ｇ／Ｌ；ｎ＝１１次）。采样频率４５样／ｈ。     

磷、砷、硅钼杂多酸-罗丹明6G荧光猝灭法连续测定磷、砷、硅的研究

本文报道了在非离子表面活性剂PVA存在下,磷、硅、砷钼杂多酸-罗丹明6G形成离子缔合物,使罗丹明6G荧光猝灭。研究了罗丹明6G-磷、砷、硅钼杂多酸体系荧光光谱,形成条件和配合物组成。试验了共存离子的干扰。应用此方法对铜合金中磷、砷、硅进行同时测定,结果满意。     

卡尔曼滤波分光光度法同时测定钢样中的硅、磷、砷

研究了在聚乙烯醇存在下,硅、磷、砷钼杂多酸与罗丹明6G形成离子缔合物的反应,建立了能同时测定硅、磷、砷的卡尔曼滤波分光光度法。用于钢样中微量硅、磷、砷的同时测定,操作简便快速,相对误差小于8％。     

含钼四元杂多磷钨酸盐的电化学研究

含钼四元杂多磷钨酸盐的电化学研究张恒彬，齐兴义，郑军伟，李树家（吉林大学化学系，长春，１３００２３）关键词磷钨杂多酸，氧化还原，电催化，循环伏安Ｋｅｇｇｉｎ结构钼或钨的杂多酸有良好的氧化还原性质和电催化作用［１～３］．其中钼或钨被其它过渡金属元素取代...     

岩石矿物中磷的快速光度测定——混合试剂显色法

磷钼蓝光度法已广泛用于地质试样中磷的测定。但发色速度受温度的影响颇大,一般需加热,显色酸度也较严,稍不注意,游离的钼酸盐被还原而造成测定失败。本文采用抗坏血酸-锑-钼酸盐-酸羟胺组成的混合试剂作为磷的显色剂,可在室温下使磷迅速发色,而且显色后96小时内络合物的吸光度不变。由于在显色剂中引入了较多的盐酸羟胺,有效地抑制了游离钼酸盐的还原,故磷钼蓝的颜色纯且稳定。     

甲酸在钼青铜修饰铂电极上的催化氧化

应用循环伏安法和双电位阶跃法研究了不同浓度硫酸中钼酸盐在多晶铂电极上的电化学行为 .在硫酸溶液中 ,当电位负向扫描时 ,钼酸盐即于铂电极上还原形成钼青铜 ,吸附在电极表面 ;电位正向扫描时钼青铜将再被氧化 ,氧化机理受硫酸浓度的影响 .铂电极因钼酸盐的还原和钼青铜的氧化而得到修饰 .在硫酸钠溶液中以此修饰的铂电极对甲酸氧化有明显的催化作用 ,其氧化峰电流接近未修饰铂电极上的 2倍 .钼青铜对铂的不完全修饰或过分修饰均会减弱甲酸氧化的催化作用     

硅钼蓝分光光度法测定磷铁合金中硅

硅钼蓝光度法测定硅在冶金领域中已有广泛应用[1-3],但大都是应用于低磷合金,然而对于磷铁合金(磷质量分数高达30%)中硅含量的测定通常采用氟硅酸钾滴定法[4],也有文献报道采用十二烷基硫酸钠作保护剂,用硅钼蓝光度法测定[5]。本工作采用草酸破坏磷钼、砷钼杂多酸,在高酸度下消除磷干扰,用硅钼蓝光度法测定硅的含量。1试验部分1.1仪器与试剂721型分光光度计。无水亚硫酸钠溶液:30g·L-1。     

流动注射示差动力学化学发光法测定微量硅

根据硅钼杂多酸氧化Ｌｕｍｉｎｏｌ产生化学发光的性质，以及硅钼杂多酸与磷钼杂多酸形成速度的差异，采用停流技术，在硅磷共存时，不经分离，实现了对和钢样中硅的选择性测定。该法检出限为２．０×１０＾－８ｇ／ｍＬ，线性范围１．０×１０＾－７－１．０×１０＾－５ｇ／ｍＬ，相对标准偏差为２．８％。     

氧化还原活性碳纤维的研究进展

就氧化还原碳纤维的制备及其结构、影响氧化还原容量的因素、氧化还原机理等方面进行了综述，并做了研究前景展望。     

Redox equilibria of iron oxides in aqueous-based magnetite dispersions: effect of pH and redox potential

The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.     

A study of redox properties of hydralazine hydrochloride,an antihypertensive drug

Hydralazine hydrochloride itself is a reducing agent and its redox properties like other reducing agents vary as the oxidizing agent and applied conditions vary. The redox properties of hydralazine were studied by spectrophotometric method. Formal redox potential of hydralazine was calculated and effect of pH was observed on redox properties of hydralazine.     

A Comprehensive Outlook of Synthetic Strategies and Applications of Redox‐Responsive Nanogels in Drug Delivery

Increasing recognition of the role of oxidative stress in the pathogenesis of many clinical conditions and the existence of defined redox potential in healthy tissues has led to extensive research in the development of redox‐responsive materials for biomedical applications. Especially, considerable growth has been seen in the fabrication of polymeric nanogel–based drug delivery carriers utilizing redox‐responsive cross‐linkers bearing a variety of functional groups via various synthetic strategies. Redox‐responsive polymeric nanogels provide an advantage of facile chemical modification post synthesis and exhibit a remarkable response to biological redox stimuli. Due to the interdisciplinary nature of the subject, a more profound combined conceptual knowledge from a chemical and biological point of view is imperative for the rational design of redox‐responsive nanogels. The present review provides an insight into the design and fabrication of redox‐responsive nanogels with particular emphasis on synthetic strategies utilized for the development of redox‐responsive cross‐linkers, polymerization techniques being followed for nanogel development and biomedical applications. Cooperative effect of redox trigger with other stimuli such as pH and temperature in the evolution of dual and triple stimuli‐responsive nanogels is also discussed.     

Macroreticular redox polymers. III. Characterization of some hydroquinone–quinone redox polymers

A series of hydroquinone–quinone redox polymers on highly and lightly crosslinked macroreticular styrene–divinylbenzene matrices was characterized for redox capacity, reactivity, equilibria, and redox potential. The effects of cerium(IV), iron(III), and oxygen on determinations of redox capacity are described.     

Fluorescent Polypyrrole Nanospheres – Synthesis and Properties of “Wireless” Redox Probes

In this work a novel concept of monitoring of occurrence of redox reactions between conducting polymer nanospheres and redox species in a solution is proposed. The redox process is monitored in the emission mode (without wiring of the probe to an electrochemical measuring set‐up) as a change in emission spectrum of a dye (not participating in the redox process itself) but reporting the alteration of properties of highly sensitive conducting polymer nanoparticles. This approach is possible due to applied unique method of synthesis of conducting polymers nanospheres of highly active, unblocked surface. Thus the nanospheres redox state is affected by the solution redox potential, leading to change of their properties. If solvatochromic probe of sufficiently high brightness (pyrene) is present in nanospheres, a redox reaction between the conducting polymer and solution can be observed as change of emission spectrum of the probe. Thus a localized redox potential optical probe can be obtained. The emission properties of the dye incorporated were preserved in the nanospheres, moreover, the emission spectrum of the probe was affected by the change in redox potential of the solution, thus influencing the redox state and ultimately the properties of the conducting polymer. The emission changes observed were dependent on ion‐exchange properties of polypyrrole, i.e. depending on the dopant ions present in the polymer, the sensitivity of the optical probe can be tuned.     

Measurement of the concentration of Mn2+ and Mn3+ in the manganese-catalyzed 1,4-cyclohexanedione-acid-bromate reaction using redox-triggered magnetic resonance spectroscopy

A new nuclear magnetic resonance (NMR) experiment is reported, where the spectrometer is triggered using the output from a combination redox electrode. This technique was used to probe redox oscillations in the 1,4-cyclohexanedione-acid-bromate reaction. Manganese(III) acetate or manganese(II) sulfate was used as the catalyst, and the periodic change in concentration of Mn2+/Mn3+ ions was determined as a function of redox potential. The concentration of Mn3+ ions was at a maximum at high redox potential and at a minimum at low redox potential. Also, redox potentials were found to not be dominated by the Mn2+/Mn3+ couple.     

Number of surface redox sites of V-Sb-O catalysts

The NARP technique was applied for the measurement of surface redox sites of V-Sb-oxide catalysts. The profile of produced nitrogen in the NARP measurement was composed of two parts; the initial sharp peak and the tailing part, those represented the contribution of surface redox sites and regeneration step of the redox sites with lattice oxygen, respectively. The surface concentration of redox sites determined from the initial sharp peak was almost equivalent to the surface concentration of vanadium ions above surface Sb/V ratio of 1.0. The role of V-O-Sb sites on VSbO₄ surface as redox sites was suggested. The tailing part was broader than that of V₂O₅ at the same temperature range because of the faster regeneration step relative to that in V₂O₅. The surface concentration and the regeneration of redox sites strongly depend on the preparation method.     

Scanning electrochemical microscopy of living cells: Part 2. Imaging redox and acid/basic reactivities

Amperometric feedback and potentiometric modes of the scanning electrochemical microscope (SECM) have been used to image the topography and map redox and acid–base activities in single mammalian cells. The topographic images of cells were obtained using hydrophilic redox mediators, which cannot penetrate the cell membrane. In contrast, with a hydrophobic mediator one can map redox reactivity with a micrometer or submicrometer spatial resolution. The images obtained with oxygen used as a redox mediator show the distribution of the diffusion rate of oxygen in the cell membrane and inside the cell. The acid release by the cell was imaged with a Sb tip in a potentiometric mode, and the possibility of redox and pH imaging of the same cell with same tip is demonstrated. Significant differences were detected in the redox and pH images of normal human breast epithelial cells and metastatic breast cancer cells.     

Synthesis of crowded triarylphosphines carrying functional sites

4,4′-Diphosphinobiaryls and 1,3- and 1,4-borylphosphinobenzenes carrying crowded triarylphosphine moieties were synthesized by reaction of the corresponding diarylchlorophosphine with an arylcopper(I) reagent. Intramolecular interaction of the phosphorus redox center with the other phosphorus or the boron redox center was investigated by cyclic voltammetry. 4,4′-Diphosphinobiaryls displayed two-step reversible redox waves with slight differences of the oxidation potentials due to weak interaction between two phosphorus redox centers across 4,4′-biarylene linkage. Borylphosphinobenzenes showed two step redox waves corresponding to oxidation at the phosphorus and reduction at the boron. Although significant interaction between the phosphorus and boron redox centers was not observed in the cyclic voltammograms due to large difference of the redox potentials between phosphorus and boron redox centers, an absorption due to weakly interacting phosphorus and boron was observed in the UV-Vis spectrum of the 1,4-borylphosphinobenzene.