聚苯胺的电化学现场ESR-电导同步测量

本论文工作通过设计新型的电解池 ,首次实现了导电聚合物的电化学现场ESR_电导同步测量 .从获得的聚苯胺ESR信号及膜电阻随电极电势变化的精细图象看出 ,极化子晶格的形成与消亡决定了聚苯胺的导电行为 .从不同电势下聚苯胺的ESR饱和行为也得到Curie自旋与Pauli自旋相互转化的新证据 .     

掺杂聚苯胺能带结构和导电机理的研究

用EHMO-CO方法对质子掺杂聚苯胺进行了模型化理论计算,得到与吸收光谱实验数据一致的能带结构,研究表明,掺杂苯胺中的载流子是极化子,能满意地解释掺杂聚苯胺的导电机制。     

电子定域化函数的含义与函数形式

电子定域化函数(ELF)是研究电子结构的重要工具.本文介绍了电子定域性的概念,从电子对密度和动能密度两个角度详细讨论了ELF的物理意义与其函数形式的联系,并将ELF推广到自旋极化形式.通过实例分析,指出了参考项在ELF 中起到了关键性作用.对两种自旋极化形式的ELF 的比较发现:CheckDen 和TopMoD程序中使用的形式并不合理,明显低估了单电子区域的定域性.最后指出了一些文献由于对ELF函数的错误理解而在引用时出现的错误.     

自旋标记法研究STVPh/PEO共混体系的链运动

利用自旋标记法将氮氧自由基连接在聚氧化乙烯分子末端,测得其与不同羟基含量的苯乙烯-4-乙烯基苯酚共聚物组成高分子共混体系的ESR波谱,研究了各组分的分子链运动.自旋标记聚氧化乙烯的ESR谱图在整个温度范围内只显示快运动或慢运动的一种运动成分,表明氮氧自由基处于单一的环境中.高分子共混体系的ESR谱在一定温度范围内同时存在快运动和慢运动的两种运动成分,且两成分相对比例随温度的变化而变化,表明体系中氮氧自由基处于不同的微相环境中.由ESR谱得到的T_5mT,τ_c,E_a的值都随着体系中羟基含量的增加而变大,显示标记分子的链运动在共混体系中的活动逐步受阻.与此同时,随着该共混物中酚羟基和醚氧基间氢键相互作用强度的增大,共混物的相容性得到逐步改善.     

电纺聚苯胺涂层表面浸润性和表面荷电对微生物附着的影响

材料表面浸润性和表面荷电对微生物在材料表面的附着有着非常重要的影响.本文采用静电纺丝法在不锈钢电极表面分别制备了疏水和亲水的聚苯胺纤维涂层,利用电化学阻抗谱监测大肠杆菌在两种聚苯胺纤维涂层表面的附着情况.结果表明,亲水表面有利于抑制大肠杆菌的附着.通过电化学极化使亲水表面分别带正电荷和负电荷,利用平板涂布计数法研究了不同极化时间下两种荷电表面的抑菌率,发现无论正电荷还是负电荷都有利于抑制微生物附着,而且二者没有明显差异.在相同的阴极极化条件下,亲水和疏水的聚苯胺纤维涂层抑菌性能相差不大,说明对于电纺聚苯胺涂层抑制细菌附着而言,电化学极化的影响大于表面浸润性的影响.     

苯封四聚苯胺/TiO2/ITO薄膜电极光致界面电荷转移

采用水解胶溶法和旋转涂膜法分别制备出TiO2纳米粒子溶胶和TiO2/ITO薄膜, 采用浸泡法制备出苯封四聚苯胺(聚苯胺)/TiO2/ITO薄膜电极. 利用表面光电压谱、光致循环伏安和光电流作用谱测定了TiO2的禁带宽度和表面态能级、聚苯胺的 HOMO-LUMO能级宽度和双极化子能级, 确定了聚苯胺/TiO2/ITO薄膜电极能带结构. 进一步分析了聚苯胺/TiO2/ITO薄膜电极的光电转换特性及光致界面电荷转移的机理.     

违反Hund规则的情况——自旋极化效应

自旋极化效应能够导致违反Hund规则的情况,特别是对于单重态和三重态成对出现的组态。在具有一个以上未成对电子的体系中,我们注意到动态自旋极化决定于未成对电子的相对自旋方向,并且在开壳层的单重态和三重态中动态自旋极化效应是不同的,对于这两种状态的自旋极化效应可用CI-型波函数来描述。     

锂嵌碳的磁共振研究

本文综述了十数年来电子自旋共振(ESR)和7Li核磁共振(7Li-NMR)技术用于锂嵌碳研究的进展.ESR研究发现锂嵌碳材料中存在两种电子自旋.一种来自碳材料中的载流子电子,称为Pauli自旋.从Pauli自旋的ESR强度可推算给定锂嵌碳样品的电子态密度曲线,并进而计算能带模型机理对该样品嵌锂容量的贡献.另一种来自局域化自旋,即Curie自旋,其与嵌锂位置的关系尚不清楚.7Li-NMR测试已发现几个不同的谱峰,其峰位和强度随碳样品性质和嵌锂深度而异.一般认为,45±5×10-6(即ppm,下同)处的NMR谱线源于深度嵌锂(在LixC6中x=0.5～1)石墨化结构中的Li+,属于Knight位移;而明显小于45×10-6的谱峰则可能是来自碳材料中石墨化微结构中低浓度Li+的Knight位移,也可能是于无序微结构中共价结合的Li的化学位移.ESR与7Li-NMR在研究锂嵌碳方面有很强的互补性,联合应用此两技术可望对深入认识锂嵌碳材料的构效关系作出新贡献.     

自旋标记法研究STVPh／PE0共混体系的链运动

利用自旋标记法将氮氧自由基连接在聚氧化乙烯分子末端，测得其与不同羟基含量的苯乙烯-4-乙烯基苯酚共聚物组成高分子共混体系的ESR波谱，研究了各组分的分子链运动．自旋标记聚氧化乙烯的ESR谱图在整个温度范围内只显示快运动或慢运动的一种运动成分。表明氮氧自由基处于单一的环境中．高分子共混体系的ESR谱在一定温度范围内同时存在快运动和慢运动的两种运动成分。且两成分相对比例随温度的变化而变化，表明体系中氮氧自由基处于不同的微相环境中．由ESR谱得到的T5mT．τc，En的值都随着体系中羟基含量的增加而变大，显示标记分子的链运动在共混体系中的活动逐步受阻．与此同时，随着该共混物中酚羟基和醚氧基间氢键相互作用强度的增大，共混物的相容性得到逐步改善．     

γ射线辐照的多晶态嘧啶核苷类中自旋捕捉自由基的ESR研究——Ⅱ.胸苷和脱氧胞苷盐酸盐

本文以NtB(亚硝基特丁烷)为捕捉剂,利用自旋捕捉(Spin Trapping)和ESR方法,研究了γ射线辐照的多晶态胸苷和脱氧胞苷盐酸盐中产生的室温自由基。对它们分别确定了三种类型与两种类型的碱基自由基,此与单晶ESR研究结果完全一致,从而获得它们R·自旋加合物的标准ESR波谱。此外,对脱氧胞苷盐酸盐还确定了在单晶ESR研究中未被鉴别的核糖自由基HO(5′)HC(4′)H<及由其演变而成的—(5′)H_2自由基。     

Polyaniline: evidence of oxygen–polarons interactions to explain the high selectivity values in oxygen/nitrogen gas permeation experiments

High selectivity between oxygen and nitrogen has been found by gas permeation with doped polyaniline. Because of the small difference in kinetic diameters, solubility rather than diffusion may explain the preferential oxygen permeation. Electron spin resonance (ESR) measurements have been performed to check whether interactions of oxygen with polarons in polyaniline exist. A tenfold decrease in the spin number was observed when the polymer was in the presence of oxygen rather than nitrogen. This result was interpreted as being due to interactions between oxygen triplet states and polarons of polyaniline.     

Oligothiophene bipyridine alternate copolymers and their ruthenium metalated analogues: in situ ESR and UV-vis investigations of metal-chain interactions

In situ electron spin resonance (ESR) and UV-vis spectro-electrochemical studies have been performed on two copolymers consisting of alternating subunits of regioregular head to tail (HT) coupled 3-octylthiophene tetramer and 2,2'-bipyridine subunits (P4) or 3-octylthiophene hexamer subunits of the same regioregularity and 2,2'-bipyridine subunits (P6). Both P4 and P6 have been investigated in their metal-free form as well as in the ruthenium(II) metalated form (P4-Ru and P6-Ru). P4 and P6 in the p-doped state exhibit a clear ESR signal characteristic of the presence of polarons in the oligothienylene subunits. In the case of P4, no recombination of polarons into bipolarons is observed, whereas the recombination process takes place in P6. The formation of bipolarons is well-rationalized in terms of the conjugation length, and it seems clear that the higher length of the oligothiophene subunit in P6( )()stabilizes bipolarons(.)() The same effect, is induced by the coordination of -Ru(bpy)(2)(2+) to the bipyridine unit in the metalated form of both polymers, which results in an increase of the conjugation length. Important information is gained from the analysis of the ESR spectra of both nonmetalated and metalated in the oxidized (p-doped) and reduced (n-doped) forms. In the p-doped state both nonmetalated and metalated polymers reveal the presence of a narrow ESR line characteristic of the mobile spin carriers in the polymer matrix. The oxidation of the metal center occurs at higher potentials and leads to an irreversible destruction of the system. To the contrary, in the reduced (n-doped) state the ESR lines of the nonmetalated and metalated polymers markedly differ. A significant line broadening with simultaneous change of the g-value is caused by spin-orbit coupling phenomenon induced by the presence of the coordinating metal. Finally, the observation of a clear polaronic band in the UV-vis spectrum of p-doped P4 and its strong dependence on the applied potential can be clearly correlated with the potential induced changes in the ESR spin density. The same applies to P4-Ru, where the changes in the polaronic and bipolaronic bands can also be correlated with the ESR spin density changes.     

Effect of dioxygen on ESR spectra of polyaniline

The effect of dioxygen on the width of ESR lines of powders and films of polyaniline was studied at 15–300 K. It was found that the line broadening can decrease or increase, which corresponds to strong or weak exchange, respectively. For dry polyaniline powders and films, maxdimum broadening was observed at 240 K. The findings were explained by spin exchange during collisions of a mobile polaron with immobile O₂ molecules bound to the polymer. The values of exchange interaction between the O₂ molecule and the polaron and the mobility of the polarons along the polymer chain were found. The mobility of polarons along the polymer chains decreases in the presence of H₂O, and dioxygen predominantly adds to the imine N atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2293–2297, December, 1999.     

Raman spectroelectrochemical study of sodium intercalation into poly(p-phenylene)

The structural defects formed along the polymer chain during the electrochemical intercalation of sodium into polyparaphenylene (PPP) were investigated by in situ FT Raman measurements with an excitation wavelength of 1064 nm. Our Raman data are compared with those obtained for PPP and its oligomers intercalated with Na(+) ions by chemical ways. The coexistence of polarons and bipolarons is observed in the early stages of the intercalation process. When the doping level increases polarons are transformed to bipolarons, then in the highly intercalated sample (corresponding to a composition close to Na(0.5)(C(6)H(4))), bipolarons are the main structural defects. This evolution, which is reversible, is in accordance with the electron spin resonance (ESR) data of PPP intercalated with sodium ions in the same experimental conditions.     

可溶性聚[3-(2,2,3,3-四氟丙氧基)噻吩]的光谱性质

研究了中性和经FeCI3掺杂后聚[3-(2, 2, 3, 3-四氟丙氧基)噻吩](P3FT)溶液的光谱性质。中性P3FT具有特殊的溶剂色效应, 其甲醇 溶液的溶剂化吸收带强度随P3FT浓度增大而增强, 该吸收带是高分子链与链之间的相互作用(即聚合物的聚集态结构)的反映。用电子光谱跟踪FeCI3掺杂P3FT的过程, 结果表明, P3DT随着掺杂程度的增大, 载流子由极化子转变成双极化子, 且双极化子的能级位于禁带中间, 与孤子相似。     

THE ROTATION BARRIER OF ELECTRON SPIN PROBE IN THE STUDY OF POLYMER SYSTEM

In the study of molecular motion of polymer by means of ESR in combination with spin probe, owing to that the ESR spectrum depicts only the behavior of spin probe, the information obtained is of indirect nature. Hence the relationship between them must first be investigated before any conclusion could be drawn. In this paper, two parameters T_R and C_R are introduced to characterize the changing of tumbling rate of spin probe, and the concept of rotation barrier of spin probe is proposed. It is considered that the magnitude of the rotation barrier is determined by the internal cavity size and distribution in polymer. When the temperature is raised, the size and distribution of the cavities change accordingly, thus the tumbling of spin probe changes gradually from a slower to a higher rate.     

Observation of bi-polarons in blends of conjugated copolymers and fullerene derivatives

From a fundamental and application point of view it is of importance to understand how charge carrier generation and transport in a conjugated polymer (CP):fullerene blend are affected by the blend morphology. In this work light-induced electron spin resonance (LESR) spectra and transient ESR response signals are recorded on non-annealed and annealed blend layers consisting of alkyl substituted thieno[3,2-b]thiophene copolymers (pATBT) and the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) at temperatures ranging from 10 to 180 K. Annealing of the blend sample leads to a reduction of the steady state concentration of light-induced PCBM anions within the blend at low temperatures (T = 10 K) and continuous illumination. This is explained on the basis of the reducing interfacial area of the blend composite on annealing, and the high activation energy for electron diffusion in PCBM blends leading to trapped electrons near the interface with the CP. As a consequence, these trapped electrons block consecutive electron transfer from an exciton on a CP to the PCBM domain, resulting in a relatively low concentration charge carriers in the annealed blend. Analysis of the transient ESR data allows us to conclude that in annealed samples diamagnetic bi-polaronic states on the CPs are generated at low temperature. The formation of these states is related to the generation and interaction of multiple positive polarons in the large crystalline polymer domains present in the annealed sample.     

Reversible photoinduced electron transfer in a ruthenium poly(2-methoxyaniline-5-sulfonic acid) composite film

In situ electron spin resonance (ESR) studies have been performed on composite films consisting of a ruthenium tris(bipyridyl) complex and an inherently conducting polymer, poly(2-methoxyaniline-5-sulfonic acid) (PMAS). The composites were investigated under white light irradiation and potential control conditions to probe photoinduced electron transfer between the ruthenium metal center and the conducting polymer. PMAS exhibited a clear ESR signal, characteristic of the presence of mobile single spin polarons within the polymer structure. Irradiation of the PMAS in the presence of the ruthenium metal center resulted in the photo-oxidation of the Ru (2+) to the Ru (3+) state, as a result of which the PMAS ESR signal was replaced by a response typical of the Ru (3+) salt. Upon removal of the illumination, reversible photo switching occurred. This reversibility makes these novel composites promising for applications in areas such as chemical sensors, light switching, and light harvesting devices.     

Magnetism of spin polymers prepared by the oxidative polyrecombination of captodative compounds

Magnetism of hydroanilino ladder polymer and indigo polymer which were prepared by the oxidative polyrecombination of captodative substituted methane and indoxyl, respectively, was studied by ESR spectroscopy and magnetic susceptibility measurement. It was found that both spin polymers contained domains with high spin state in their structures and their spins were much more ordered with decreasing temperature.     

Electrochemical synthesis and characterization of polydiphenylamine

Electrochemical oxidation of diphenylamine(DPA)in acetonitrile solution producedan adhesive conducting polydiphenylamine(PDPA)film on the electrode,which exhibited multiplecolour variation in a wide range of potential.The polymer was characterized by cyclic voltam-merry,FTIR and ESR.The results indicate that the electropolymerization of diphenylamine per-forms via the 4,4＇C—C phenyl-phenyl coupling mechanism.FTIR,ESR and conductivity mea-surements for the different states of PDPA show that polydiphenylamine can be reversibly dopedand dedoped either chemically or electrochemically.It is evidenced also that there are paramagneticspecies—polarons in PDPA supposed to be the current carrier.