【作者】 杨亚杰；

【导师】 蒋亚东；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2007， 博士

【摘要】 近年来,导电聚合物纳米结构由于具有优异的光、电、气敏性能而成为研究的热点。本论文以新型导电聚合物聚（3,4—乙烯二氧噻吩）（PEDOT）为主体材料,从材料的合成出发,采用不同的方法制备了不同形态的PEDOT纳米结构,并用多种方法对制备的纳米结构进行表征,深入研究了PEDOT纳米结构的光、电、气体敏感性等特性,并进一步将导电聚合物纳米结构应用于有机电子器件,改善了器件的性能。其主要内容归纳如下:1.采用聚合和掺杂同时进行的反向胶束体系制备了粒径分散小的PEDOT纳米粒子,并用紫外—可见光光谱（UV-Vis）、傅立叶红外光谱（FT-IR）、X射线光电子能谱（XPS）、X射线衍射（XRD）、扫描电子显微镜（SEM）等分析方法对纳米粒子进行了表征。实验结果发现氧化剂用量、超声处理、聚合温度及掺杂程度对PEDOT纳米粒子的形貌、电性能及气敏性能有不同程度的影响;PEDOT纳米粒子在聚合过程中被甲基苯磺酸有效掺杂,当掺杂剂浓度在0.17 M左右时,PEDOT链的取向最为规则,在6.7°、12.7°、25°出现衍射峰;热失重法（TG）分析表明PEDOT纳米粒子的热稳定性好于普通块材,掺杂剂浓度对纳米粒子的热稳定性有一定程度影响,这是由于掺杂剂影响分子链取向而导致纳米粒子热稳定性发生变化;首次研究了PEDOT纳米粒子对HCl气体的敏感性能,发现沉积有纳米粒子的QCM器件对20 ppm气体响应时间为20 S,且具有较好的响应恢复特性,并能够有效探测较低浓度（5 ppm）的HCl气体,气敏特性明显优于普通PEDOT粒子。这是由于纳米粒子具有较大的表面积,为气体分子提供了较好的吸附和脱附条件。2.采用单体聚合—溶液浸润—聚合物成管同时进行的方法在氧化铝多孔模板（AAO）中制备了PEDOT纳米管。形貌分析表明合成的PEDOT纳米管管径为400～500 nm,复制了模板孔道的形状和尺寸,孔径的大小和孔道的形状对PEDOT纳米管形状进行调节;推断PEDOT纳米管在孔道中的生长包括两个过程:首先是聚合物溶液浸润整个孔道。其次,聚合过程中生成的阳离子自由基和掺杂态的PEDOT由于带正电荷而在孔道壁产生“钉扎”效应;XRD分析显示在孔道内生成的PEDOT分子链具有一定的取向性,进一步研究表明聚合物的吸附及单体聚合后的吸附在模板壁导致不同的分子链排列,使PEDOT纳米管分子排列有序性受到影响;采用四探针和扫描隧道显微镜（STM）方法研究了纳米管电性能,发现单根PEDOT纳米管的电导率较圆片值大,从5.5 S/cm到17.6 S/cm变化,这可能是由于压制成块后纳米管间的接触电阻大而导致圆片电阻较大:气体敏感性测试发现纳米管对多种挥发性有机气体有不同敏感性能,尤其对挥发性醇类,如甲醇、乙醇表现出比普通块材好得多的敏感性。测试结果表明PEDOT纳米管对1000 ppm甲醇气体的响应时间约为10～20 S,测试可重复性超过15次,说明PEDOT纳米管不仅提供了较大表面积供气体分子吸附,而且管中分子链取向一致,从而体现出较好的敏感性能。3.采用LB诱导沉积方法制备了不同层数的聚（3,4—乙烯二氧噻吩）/聚苯乙烯磺酸（PEDOT-PSS）导电复合膜。首次研究了十八胺（ODA）和十八胺/硬脂酸（SA）离子化单分子膜在PEDOT-PSS纳米粒子亚相及ODA/PEDOT-PSS组装体在纯水亚相上的成膜行为。实验结果发现PEDOT-PSS纳米粒子对单分子膜具有包裹作用,形成了稳定的复合单分子膜,在ODA和SA摩尔比2:1、亚相温度23℃、PEDOT-PSS浓度1×10^-3 M、压膜速率5 mm/min、拉膜速率1 mm/min的条件下薄膜具有较好的成膜性能;二次离子质谱（SIMS）和小角X射线反射（XRR）分析表明ODA/PEDOT-PSS组装体形成的多层复合膜具有较好的层状结构,单层厚度约为23 nm,这与纳米粒子的尺寸相当;设计了不同的测试结构,测量了复合膜的垂直电导率和水平电导率,研究了薄膜的直流电流-电压特性,采用变程跳跃模型（VRH）对结果进行了拟合,结果表明三维变程跳跃模型（3D-VRH）可以较好的解释多层膜中载流子的迁移;首次制备了以PEDOT-PSS复合LB膜作为空穴缓冲层的OLED器件,发现LB膜改善了器件的载流子注入效率,但进一步的研究表明薄膜的结构稳定性还有待提高。4.首次采用修饰LB膜法以二十烷酸（AA）LB膜为模板,通过3,4—乙烯二氧噻吩（EDOT）单体在LB膜亲水基团间聚合,制备了AA/PEDOT复合LB膜。UV-Vis、FT-IR和XPS分析表明EDOT在多层膜中有效聚合,生成了PEDOT导电聚合物;XRR和SIMS分析表明薄膜具有较好的层状有序结构,进一步研究发现EDOT在AA多层膜中的聚合破坏了原有LB膜的有序性,这可能与聚合过程对层状结构产生的破坏作用有关:采用四探针仪及半导体测试仪研究了薄膜导电性能,发现AA/PEDOT多层膜的电导率随处理时间的变化产生突变,这与多层膜中导电通道的“渝渗”有关,在有效导电网络连通后电导率发生了突变。测试结果还表明AA/PEDOT膜导电性明显优于PEDOT旋涂膜和ODA-SA/PEDOT-PSS复合膜,这是由于原位制备的PEDOT共轭度较高,且薄膜具有很好的层状有序结构;采用垂直拉膜方式在叉指电极上制备了不同层数的AA/PEDOT膜,测量了薄膜对HCl气体的敏感性能。结果表明膜厚、处理温度、拉膜膜压对AA/PEDOT复合LB膜的气体敏感性能有不同程度的影响。发现在较小气体浓度范围（20～60 ppm）,AA/PEDOT多层有序膜对气体表现出非线性响应特性,而在较高浓度范围表现出线性响应特性,其敏感机理可解释为电子在PEDOT共轭系统和氧化性气体间的转移;HCl气体在AA/PEDOT复合LB膜中的动力学过程包括气体的扩散和吸附,采用扩散理论和能带吸附理论对这一过程进行了阐述。更多还原

【Abstract】 In recent years,conducting polymer nanostructure has been attracted more attentions due to their excellent optic,electric and gas sensitivity performances.Based on a new type of conducting polymer poly（3,4-ethylenedioxythiophene）（PEDOT）,this paper focused on the preparation and characterization of PEDOT nanostructure with different method.The deep and detailed investigation on optical,electrical and gas sensitivity of PEDOT nanostructure was carried out.Furthermore,the application of PEDOT nanostructure to improve orangic electric device performance was also included.The main results are as follows:1.Based on reversed micelle method,small-sized PEDOT nanoparticles was prepared and different methods were utilized to characterize this nanoparticles,such as ultraviolet/visible（UV-Vis） spectroscopy,Fourier-transform infrared（FT-IR） spectrum,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy （SEM） and so on.The results showed that the amount of oxidizer,ultrasonic treatment,polymerizing temperature and doping degree has different influence on morphology,electrical ability and gas sensitivity of PEDOT nanoparticles.The bragg peak of nanoparticles at 6.7°、12.7°、25°was observed by XRD and this well orientation of molecular chain was due to the effective doping of toluene-p-sulfonic acid,which also resulted in an enhancement of thermal stability of nanoparticles than conventional PEDOT.A firstly investigation of gas sensitivity of PEDOT nanoparticles to HCl gas was carried out,and it has been found that the response time of PEDOT nanoparticles deposited QCM to 20 ppm HCl gas was about 20 S and well reproducible sensitivity of QCM device was achieved.Furthermore,the nanoparticles exhibited well detecting ability to lower gas concentration（5 ppm） than conventional one and we ascribed this phenomenon to a larger surface area of nanoparticles,which provid good condition for the adsorption and desorption of analyte gas.2.PEDOT nanotube was fabricated by a template synthesis method.The diameter of this nanotube was about 400～500 nm,which was accordance to the size of porous AAO template,which indicated that size and shape of the obtained PEDOT nanotube can be adjusted by the template.It was presumed that two processes happen successively during the formation of nanotube.The first step was the soaking of polymerizing solution into porous template,and the second step was the adsorption of free charged cationic group and doped PEDOT onto the negative charged template surface.A XRD investigation showed well orientation of PEDOT chain in tube was formed during the synthesis process and it was also found that different arranging of molecular chain reduce the ordered structure of PEDOT nanotube.The single nanotube exhibited a conductivity about 5.5～17.6 S/cm,which was higher than a nanotube pellet due to the high contact resistance between adjacent nanotube.This nanotube showed different sensitivity to varied volatilization gas,and especially showed fast response to the methanol and ethanol than conventional bulk material.The response time of PEDOT nanotube to 1000 ppm methanol was 10～20 S and the reproducing time of tests was more than 15, which due to the larger surface area and better orientation of PEDOT molecular chain in nanotube.3.A Langmuir-Blodgett（LB） inducing method was firstly used to prepare single layer and multilayer conducting composite PEDOT-PSS film.The film-forming ability of ionization ODA and ODA-SA monolayer spread on PEDOT-PSS nanoparticles subphase and the behavior of ODA/PEDOT-PSS assembly particles on pure water were firstly investigated.The results indicate that nanoparaticles in suphase pack the ionization monolayer and stable complex Langmuir film was formed at air/water interface.It has been found that the best film-forming conditions for composite film were as follows:molar ration of ODA to SA was 2:1,suphase temperature was 23 centigrade,concentration of PEDOT-PSS in subphse was about 1×10^-3 M, compressing speed and deposition speed were 5 mm/min and 1 mm/min respectively. The SIMS and XRR investigation showed that this film exhibited well ordered layer structure.Distinct interface was formed between ODA and PEDOT-PSS layer and single layer thickness of PEDOT-PSS was about 23 nm,which was well accordance to the size of PEDOT-PSS nanoparticles.Different structures were designed to test the conductive ability of these composite films and a varible range hopping（VRH） model was used to explain the film conductive mechanism.The results indicated that a 3D-VRH model explained well of transferring of charge carrier in multilayer film.Furthermore,these conducting polymeric LB film were utilized to as the hole transfer layer in OLED device,and an efficiency enhancement of carrier injection was observed,which was ascribe to the ordered structure of these film.However,a further investigation showed that this PEDOT-PSS film had inferior structure ability.4.An arachidic acid（AA）/PEDOT multilayer LB film was firstly prepared through a modified LB film method.UV-Vis,FT-IR,XPS,XRR and SIMS investigation indicated that polymerization of EDOT monomer occurred in nanospace between hydrophilic groups of AA molecular and well ordered PEDOT multilayer film is formed.The reduced ordered structure happened during polymerization of EDOT, which may be caused by a deformation of ordered AA LB film.A four-probe method and semiconductor testing system were used to investigate conductive performance of LB film.Abrupt change of conductivity during the polymerization of EDOT in LB film was observed and this phenomenon may result from an instant connection of conducting channel.It also has been found that AA/PEDOT film exhitbited better conductive ability than ODA-SA/PEDOT-PSS film and spin-coating PEDOT/PSS film,which due to the higherπstructure of PEDOT structure and ordered film structure.The gas sensitivity of PEDOT LB film deposited interdigital electrode to HCl was tested.The results showed that film thickness,treating temperature,deposition speed had different influence on film gas sensitivity.The AA/PEDOT film deposited device exhibited nonlinear behavior to HCl gas at lower concentration（20～60 ppm） and linear response behavior at higher gas concentration was observed.The gas sensitivity mechanism of PEDOT multilayer film can be explained by the charge transfer betweenπsystem of PEDOT and oxidization HCl system,A pervasion theory and energy band theory were utilized to explain the process of adsorption and desorption between HCl molecule and LB film.更多还原