现场时间分辨拉曼光谱研究不同pH值溶液中聚吡咯电极的氧化还…

对不同ｐＨ值溶液中聚吡咯的电化学氧化原行为进行了现场时间分辨拉曼光谱研究，结果表明，采用拉曼－循环伏安图可以克服充电电流给聚吡咯氧化还原峰电位的确定带来的困难。本文讨论了拉曼－循环伏安图中峰电位相对于常规循环伏安图中的氧化还原峰电位发生负移的原因。在酸性溶液中氧化还原时会出现与一定氧化程度的，质子化的聚吡咯链段有关的不稳定中间产物，这是常规拉曼光谱所不能获得的，体现了电化学现场的时间分辨拉曼光谱方     

现场时间分辨拉曼光谱研究不同pH值溶液中聚吡咯电极的氧化还原和降解

对不同ｐＨ值溶液中聚毗咯的电化学氧化还原行为进行了现场时间分辨拉曼光谱研究。结果表明，采用拉曼－循环伏安图可以克服充电电流给聚吡咯氧化还原峰电位的确定带来的困难。本文讨论了拉曼－循环伏安图中峰电位相对于常规循环伏安图中的氧化还原峰电位发生负移的原因。在酸性溶液中氧化还原时会出现与一定氧化程度的、质子化的聚吡咯链段有关的不稳定中间产物，这是常规拉曼光谱所不能获得的，体现了电化学现场时间分辨拉曼光谱方法的优越性。     

变温拉曼光谱研究电化学合成聚吡咯膜

在含有四氟化硼四丁基铵的乙氰溶液中电化学氧化吡咯制得聚吡咯膜,并在-195到150℃温度范围内研究了该聚合物膜的变温拉曼光谱。在升温过程中,与氧化态相关的拉曼光谱谱带渐渐消失,这主要是由于空气中氧气和水分子的作用。在冷冻过程中,聚合物链从无规线团状态转变成棒状构象,从而增加了导电高分子的共轭链长。由于拉曼的共振效应,在冷冻过程中与氧化态链段相关的谱带得到了增强。     

PPy/Nafion复合膜的制备及性能表征

用0.5mol.L-1的FeCl3溶液作引发剂,采用原位化学聚合法将吡咯单体聚合在Nafion117膜基体中。复合膜的红外光谱图中出现明显聚吡咯（PPy）的特征吸收峰,说明吡咯单体聚合在Nafion117膜中。机械性能测试表明复合膜的拉伸强度比Nafion117膜提高了。热重测试表明复合膜具有更高的热稳定性能。对复合膜进行了甲醇渗透性能的测试,结果表明复合膜具有明显的阻醇作用,PPy/NF-3膜的甲醇渗透率值是5.9×10^-7cm^2.s^-1,和Nafion117膜相比降低了53%。     

电化学法制备高密度导电聚吡咯的性能研究

系统地研究了溶剂、温度和聚合电流密度对电化学制备本征导电聚吡咯 (PPy)膜密度的影响,分别用四探针法和热失重(TG)法研究了不同密度的PPy膜的电导率和热稳定性.用循环伏安法(CV)和电化学阻抗谱(EIS)法比较了不同密度的PPy膜的电化学性能.研究表明,在室温下,在乙氰/水(AN/H₂O, 99/1)溶液比在水溶液中容易得到高密度的PPy膜.高聚合电流密度(如10mA/cm²)可以进一步提高PPy膜的密度,用X射线光电子能谱(XPS)对其结构进行了分析.在AN/H₂O(99/1)溶液中用小电流密度(0.1mA/cm²)聚合时,低温(-20℃)有利于提高PPy膜的密度;然而在高电流密度(10mA/cm²)时, 低温(-20℃)不利于提高PPy膜的密度.高密度的PPy膜(1.42g/cm³)用电流密度10mA/cm²在0℃的AN/H₂O(99/1)溶液中制得.该合成方法和常用的低温低电流密度方法制备高密度的PPy膜相比, 合成时间短,条件易实现,更利于实用化.更重要的是,高密度的PPy膜不仅具有高电导率(～220S/cm)和高热稳定性,还具有低的电化学活性.因此,高密度的PPy膜不仅是一种优异的电子导电的电极材料,而且是一种潜在的优异的防腐材料. 关键词： 聚吡咯膜 密度 电导率 热稳定性     

二次掺杂聚吡咯/聚噻吩膜的制备及其光电性能

为了研究磷酸锌二次掺杂聚吡咯/聚噻吩膜的光电及防腐蚀性能,采用直接接触氧化技术在磷酸锌溶液中制备出掺杂聚吡咯/聚噻吩,再用磷酸锌在脱掺杂聚吡咯的基础上制备出性能优良的二次掺杂聚吡咯/聚噻吩膜。采用循环伏安曲线、扫描电镜和动电位极化曲线测试了二次掺杂聚吡咯/聚噻吩/磷酸锌复合材料的微观形貌及光电性能,并与一次掺杂及未掺杂的聚吡咯/聚噻吩进行了对比。测试结果表明:不锈钢表面覆盖掺杂的聚吡咯/聚噻吩膜都有较好的光电性能,以二次掺杂聚吡咯/聚噻吩膜性能为最好。与未掺杂的聚吡咯/聚噻吩高分子膜相比,二次掺杂聚吡咯膜的腐蚀电位比纯聚苯胺膜提高了约0.989 V,自腐蚀电流降低了约2个数量级。     

PPy/Nafion(R)复合膜的制备及性能表征

用0.5mol·L-1的FeCl3溶液作引发剂,采用原位化学聚合法将吡咯单体聚合在Nafion(R)117膜基体中.复合膜的红外光谱图中出现明显聚吡咯(PPy)的特征吸收峰,说明吡咯单体聚合在Nafion(R)117膜中.机械性能测试表明复合膜的拉伸强度比Nafion(R)117膜提高了.热重测试表明复合膜具有更高的热稳定性能.对复合膜进行了甲醇渗透性能的测试,结果表明复合膜具有明显的阻醇作用,PPy/NF-3膜的甲醇渗透率值是5.9×10-7cm2·s-1,和Nafion(R)117膜相比降低了53%.     

导电性聚合物复合材料的制法及应用

一般来说,金属是电的良导体,而有机聚合物(如塑料、纤维、橡胶等)是电的绝缘体.然而,近年来,能够导电的、具有大共轭双键结构的高分子电荷转移复合物引起了人们广泛的兴趣,世界各国纷纷进行研究和开发.在这一大类导电聚合物中,聚吡咯又有其特别的意义,因为它热稳定性好,容易掺杂,便于制备,导电性能可以通过控制制备条件来改变.可是,已有的各种方法大多是用电化学聚合法,得到的聚吡咯不是粉末,就是附在金属电极表面上的膜.因为聚吡咯不溶不熔,这些产物难以加工成各种形状的制品,这就大大限制了它的使用范围.怎样才能把聚吡咯做成具有使用形状…     

拉曼光谱研究聚噻吩微米/纳米管

分别具有 2 0 0nm和 2 0nm管径的聚噻吩微米 /纳米管通过用微孔氧化铝过滤膜作为模板在三氟化硼乙醚溶液中电解聚合噻吩制得。在一张厚度约为 2 0nm的金箔上这些具有单分散长度的微米管能很好平行站立起来形成阵列 ,而纳米管则相互粘附不能形成很好的阵列。用 6 3 3nm激发的拉曼光谱研究表明 :微米管具有较高的掺杂程度 ,而纳米管的掺杂程度很低。这主要是由于两种管子的壁厚不同引起的     

拉曼光谱研究聚噻吩微米/纳米管

分别具有 2 0 0nm和 2 0nm管径的聚噻吩微米 /纳米管通过用微孔氧化铝过滤膜作为模板在三氟化硼乙醚溶液中电解聚合噻吩制得。在一张厚度约为 2 0nm的金箔上这些具有单分散长度的微米管能很好平行站立起来形成阵列 ,而纳米管则相互粘附不能形成很好的阵列。用 6 3 3nm激发的拉曼光谱研究表明 :微米管具有较高的掺杂程度 ,而纳米管的掺杂程度很低。这主要是由于两种管子的壁厚不同引起的     

Photoluminescence spectra of doped GaAs films

We have studied the dependence of the photoluminescence (PL) spectrum on the doping level and the film thickness of n-GaAs thin films, both experimentally and theoretically. It has been shown theoretically that modification of the PL spectrum of p-type material by p-type doping is very small due to the large valence-band hole effective mass. The PL spectrum of n-type material is affected by two factors: (1) the electron concentration which determines the Fermi level in the material; (2) the thickness of the film due to re-absorption of the PL signal. For the n-type GaAs thin films under current investigation, the doping level as well as the film thickness can be very well calibrated by the PL spectrum when the doping level is less than 2×10¹⁸ cm^-3 and the film thickness is in the range of the penetration length of the PL excitation laser. PACS 78.20.-e; 78.55.Cr; 78.66.Fd     

钼掺杂氧化锌薄膜的结构、光学和表面等离子体特性研究

室温下,通过直流磁控反应溅射在石英衬底上制备一系列钼掺杂氧化锌薄膜。分别采用X射线衍射(XRD)、原子力显微镜(AFM)、分光光度计及拉曼光谱仪研究了钼掺杂浓度对氧化锌薄膜结构、表面形貌、光学性能和表面等离子体特性的影响。XRD测试结果表明,零掺杂氧化锌薄膜结晶良好,呈c轴择优取向,掺杂后薄膜缺陷增多,结晶质量下降,当掺杂浓度达到3.93 Wt%时,薄膜由c轴择优取向的晶态转变为非晶态。AFM测试结果表明非晶态掺钼氧化锌薄膜表面光滑,粗糙度最低可达489 pm。透射光谱表明所有薄膜样品在可见光范围(400～760 nm)平均透过率均达到80%,禁带宽度随着掺杂浓度的提高从3.28 eV单调增加至3.60 eV。吸收光谱表明氧化锌薄膜表面等离子体共振吸收峰随钼掺杂量的增大发生蓝移,而拉曼光谱表明Mo重掺杂时ZnO薄膜表面拉曼散射信号强度显著降低。通过Mo掺杂获得非晶态氧化锌薄膜,拓宽了氧化锌薄膜材料的应用领域,同时研究了Mo掺杂浓度对氧化锌薄膜表面等离子体的调控作用,这对制备氧化锌基光子器件具有重要参考价值。     

Effect of Al Doping on Properties of SiC Films

Undoped and Al-doped 3C-SiC films are deposited on Si（100） substrates by low-pressure chemical vapour deposition. Effects of aluminium incorporation on crystallinity, strain stress, surface morphology and growth rate of SiC films have been investigated. The x-ray diffraction patterns and rocking curves indicate that the crystallinity is improved with aluminium doping. Raman scatting patterns also demonstrate that the strain stress in SiC films is released due to the incorporation of Al ions and the increase of film thickness. Furthermore, due to the catalysis of surface reaction which is induced by trimethylaluminium, the growth rate is increased greatly and the growth process varies from three-dimensional island-growth mode to step-flow growth mode.     

Effects of metal doping on the physical properties of ZnTe thin films

Zinc telluride (ZnTe) thin films were sublimated on a glass substrate using closed space sublimation (CSS) technique. ZnTe thin films of same thickness were tailored with copper (Cu) & silver (Ag) doping, considered for comparative study. X-ray diffraction (XRD) patterns of as-deposited ZnTe thin film and doped ZnTe samples exhibited polycrystalline behavior. The preferred orientation of (111) having cubic phase was observed. XRD patterns indicated that the crystallite size had increased after silver and copper immersion in as-deposited ZnTe thin films. Scanning electron microscopy (SEM) was used to observe the change of as-deposited and doped sample's grains sizes. EDX confirmed the presence of Cu and Ag in the ZnTe thin films after doping respectively. The optical studies showed the decreasing trend in energy band gap after Cu and Ag-doping. Transmission also decreased after doping. Resistivity of as-deposited ZnTe thin film was about 10⁶ Ω cm. The resistivity was reduced to 68.97 Ω cm after Cu immersion, and 10⁴ Ω cm after Ag immersion. Raman spectra were used to check the crystallinity of as-deposited, Cu and Ag-doped ZnTe thin film samples.     

厚度对未掺杂ZnO薄膜光谱性能的影响

X射线衍射光谱、拉曼光谱和紫外可见透射光谱技术是薄膜材料检测的重要技术手段。通过对薄膜材料光谱性能的分析,可以获得薄膜材料的物相、晶体结构和透光性能等信息。为了解厚度对未掺杂ZnO薄膜的X射线衍射光谱、拉曼光谱和紫外可见透射光谱性能的影响,利用溶胶-凝胶法在石英衬底上旋涂制备了不同厚度的未掺杂ZnO薄膜样品,并对薄膜样品进行了X射线衍射光谱、拉曼光谱和紫外可见透射光谱的检测。首先,通过X射线衍射光谱检测发现,薄膜样品呈现出（002）晶面的衍射峰,ZnO薄膜为六角纤锌矿结构,均沿着C轴择优取向生长,且随着薄膜厚度的增加,衍射峰明显增强,ZnO薄膜的晶粒尺寸随着膜厚的增加而长大。利用扫描电子显微镜对薄膜样品的表面形貌分析显示,薄膜表面致密均匀,具有纳米晶体的结构,其晶粒具有明显的六角形状。通过拉曼光谱检测发现,薄膜样品均出现了437 cm-1的拉曼峰,这是ZnO纤锌矿结构的特征峰,且随着薄膜厚度的增加,其特征拉曼峰强度也增加,进一步说明了随着ZnO薄膜厚度的增加,ZnO薄膜晶化得到了加强。最后,通过紫外可见透射光谱测试发现,随着膜厚的增加,薄膜的吸收边发生一定红移,薄膜样品在可见光区域内的透过率随着膜厚度增加而略有降低,但平均透过率都超过90%。通过对薄膜样品的紫外-可见透射光谱进一步分析,估算了薄膜样品的折射率,定量计算了薄膜样品的光学禁带宽度,计算结果表明：厚度的改变对薄膜样品的折射率影响不大,但其禁带宽度随着薄膜厚度的增加而变窄,且均大于未掺杂ZnO禁带宽度的理论值3.37 eV。进一步分析表明,ZnO薄膜厚度的变化与ZnO晶粒尺寸的变化呈正相关,本质上,吸收边或光学禁带宽度的变化是由于ZnO晶粒尺寸变化引起的。     

Corrosion protection by sonoelectrodeposited organic films on zinc coated steel

A variety of coatings based on electrosynthesized polypyrrole were deposited on zinc coated steel in presence or absence of ultrasound, and studied in terms of corrosion protection. Cr III and Cr VI commercial passivation were used as references. Depth profiling showed a homogeneous deposit for Cr III, while SEM imaging revealed good surface homogeneity for Cr VI layers. These chromium-based passivations ensured good protection against corrosion. Polypyrrole (PPy) was also electrochemically deposited on zinc coated steel with and without high frequency ultrasound irradiation in aqueous sodium tartrate-molybdate solution. Such PPy coatings act as a physical barrier against corrosive species. PPy electrosynthesized in silent conditions exhibits similar properties to Cr VI passivation with respect to corrosion protection. Ultrasound leads to more compact and more homogeneous surface structures for PPy, as well as to more homogeneous distribution of doping molybdate anions within the film. Far better corrosion protection is exhibited for such sonicated films.     

Raman fingerprint of doping due to metal adsorbates on graphene

The properties of single-layer graphene are strongly affected by metal adsorbates and clusters on graphene. Here, we study the effect of a thin layer of chromium (Cr) and titanium (Ti) metals on chemical vapor deposition (CVD)-grown graphene by using Raman spectroscopy and transport measurements. The Raman spectra and transport measurements show that both Cr and Ti metals affect the structure as well as the electronic properties of the CVD-grown graphene. The shift of peak frequencies, intensities and widths of the Raman bands are analyzed after the deposition of metal films of different thickness on CVD-grown graphene. The shifts in G and 2D peak positions indicate the doping effect of graphene by Cr and Ti metals. While p-type doping was observed for Cr-coated graphene, n-type doping was observed for Ti-coated graphene. The doping effect is also confirmed by measuring the gate voltage dependent resistivity of graphene. We have also found that annealing in Ar atmosphere induces a p-type doping effect on Cr- or Ti-coated CVD-grown graphene.     

掺杂和未掺杂氧化锌薄膜的拉曼光谱

利用拉曼光谱分别对不同衬底上,未掺杂和掺杂以及掺杂浓度不同的ZnO薄膜进行了系统的分析研究。其中ZnO薄膜均由溶胶-凝胶法制得,掺杂源为LiCl。测得的拉曼光谱显示,Pt/Ti/SiO2/Si衬底上生长的ZnO薄膜的拉曼特征峰(437cm-1)的强度明显高于SiO2/Si衬底上ZnO薄膜的拉曼特征峰的强度,说明Pt/Ti/SiO2/Si衬底上ZnO的晶化程度比SiO2/Si上ZnO的晶化程度高;但ZnO拉曼特征峰的位置和半高宽并没有发生变化,说明两种衬底上ZnO薄膜中应力大小没有发生变化。掺Li+后,580cm-1处的峰位向高频方向移动,且掺杂浓度越大频移量越大,说明掺杂已经在不同程度上引起了ZnO晶体中自由载流子浓度的变化。此外,还分析了掺Li+未在很大程度上引起ZnO晶格畸变的原因。