基于聚吡咯纳米线修饰玻碳电极的硝酸根电流型传感器研究

在玻碳电极表面,采用电聚合方法一步制备聚吡咯纳米线。由于聚吡咯的电化学氧化还原过程伴随有硝酸根的掺杂/脱掺杂,基于此构建了硝酸根电流型传感器。详细探讨了电聚合溶液的pH值、电聚合电位、电聚合时间、富集电位和富集时间对聚吡咯纳米线形貌,以及对硝酸根在修饰电极表面电化学响应的影响。在最佳条件下,构建的硝酸根传感器的线性范围为1.0×10-3～4.0×10-3 mol/L,检出限(S/N=3)达到2.2×10-4 mol/L,且具有良好的稳定性、重现性以及抗干扰能力。     

导电聚吡咯纳米线的电化学无模板法可控合成与表征

以β-萘磺酸(NSA)为掺杂剂,采用电化学无模板法制备了聚吡咯(PPy)纳米线.研究了NSA浓度、吡咯(Py)单体浓度及反应温度对PPy纳米线形貌的影响.分别采用场发射扫描电子显微镜(FE-SEM)和拉曼光谱对PPy纳米线的结构形貌和化学结构进行了表征.结果表明,利用电化学无模板法可得到中空的PPy纳米线;NSA浓度会影响PPy纳米线的取向性;增大Py单体浓度,可制得圆锥状PPy纳米线;低温有利于合成形状细长、紧密堆积的PPy纳米线.PPy纳米线形貌受游离Py浓度及Py-NSA胶束数量影响,通过调节NSA浓度、Py浓度及反应温度改变游离Py浓度及Py-NSA胶束数量,可制得不同形貌的PPy纳米线.     

电解质溶液对聚吡咯电聚合中过氧化行为的影响

分别以硫酸/水和高氯酸锂/乙腈为电解质溶液, 采用循环伏安法在铂基底电极上电聚合制备了聚吡咯, 研究了电解质溶液对聚吡咯电聚合过程中过氧化行为的影响. 与硫酸/水溶液相比, 在高氯酸锂/乙腈溶液中电聚合制备的聚吡咯发生过氧化的峰电位正移了0.42 V. 采用原位傅里叶变换红外(in situ FTIR)光谱技术检测, 结果表明, 电聚合制备的聚吡咯在2种电解质溶液中均发生了过氧化反应, 其β-C经氧化生成C-OH或CO. 在硫酸/水溶液中, 部分聚吡咯发生电氧化降解生成CO₂, 致使其共轭结构被破坏, 电导率迅速下降. 而在高氯酸锂/乙腈溶液中, 在更高的电位范围内, 聚吡咯并没有氧化降解成CO₂.     

水介质中吡咯的电化学聚合反应

研究了扫描电位上限对循环伏安法制备聚吡咯膜性能的影响，吡咯在水溶液中于玻碳电极表面化学聚合的起始电位为0．58V，在聚吡咯（Ppy）修饰电极表面聚合的起始电位为0．55V，当聚合电位上限在0．80V以上时，Ppy的氧化还原反应可逆性变差，同时，氧化电位过高将导致Ppy膜导电性能下降；研究了聚合介质对循环伏安法制备导电聚吡咯膜的影响，实时观察了吡咯（Py）聚合过程溶液中质子含量的动态变化，发现Py聚合伴随有质掺杂←→释放过程；结合Ppy膜的元素分析、ESR分析和IR光谱分析，总结出了水介质中电化学聚合高导电性聚吡咯膜的条件。     

聚吡咯纳米颗粒的静态法合成及表征

在无模板、无表面活性剂条件下,采用静态化学氧化聚合法合成了高聚合产率(93%)聚吡咯纳米颗粒.以红外光谱、广角X射线衍射、四探针仪、扫描电子电镜和透射电子显微镜对聚吡咯的结构、电性能和形貌进行了表征.并研究了搅拌条件、氧化剂种类、过硫酸铵/吡咯摩尔比、聚合反应温度和反应介质对聚吡咯纳米颗粒的粒径、形貌的影响.结果发现,聚吡咯纳米颗粒的尺寸随聚合反应条件的变化而改变.在静态条件下,以过硫酸铵为氧化剂、过硫酸铵/吡咯摩尔比为0.25,于0℃冰水浴中有利于获得聚吡咯纳米颗粒.透射电子显微镜的结果表明以过硫酸铵/吡咯摩尔比为0.25,于0℃下1.0mol/LHCl水溶液介质中可以聚合得到直径为43nm、颗粒大小均匀的球形聚吡咯纳米颗粒.盐酸掺杂聚吡咯纳米颗粒的室温电导率可达5.5S/cm.     

不同状态下聚吡咯膜的电化学阻抗

用恒电流法分别聚合了掺杂对甲苯磺酸根(pTS-)和十二烷基磺酸根(DS-)的聚吡咯膜(PPy/pTS和PPy/DS),通过循环伏安法(CV)和电化学阻抗法(EIS)测试了聚吡咯膜在NaCl溶液中‘过电位’电化学过程前后及不同电位下聚吡咯膜的电化学性能.同时,通过嵌入和脱出Na+和Cl-离子的聚吡咯膜在特定溶液中电化学阻抗图谱,研究了离子的嵌入对聚吡咯膜电化学性能的影响.结果表明‘过电位’现象可以提高聚吡咯膜的离子电导率和膜电容,Cl-离子的嵌入能提高PPy/pTS的电导率,而Na+离子的嵌入对聚吡咯膜的电导率影响不大.另外,嵌入离子对聚吡咯膜形貌的改变会对聚吡咯膜的离子传导率有一定影响,从而导致膜的电化学阻抗的变化.     

无纺布基聚吡咯柔性电极的储锂性能

高性能的柔性锂离子电池对可穿戴电子设备的发展具有重要意义。采用化学氧化法在聚对苯二甲酸乙二醇酯(PET)无纺布基材上原位聚合聚吡咯(PPy),并通过控制反应条件得到不同形貌的聚吡咯电极材料。当反应体系中剪切力较小时,得到纳米线状聚吡咯(PPy-NW/PET),反之,为纳米颗粒形貌的聚吡咯(PPy-NP/PET)。PPy纳米线的平均直径为460 nm,在包覆PET纤维的同时相互交叠,形成了三维网状导电通道。该PPy/PET可以直接作为无粘结剂的柔性电极材料。电化学测试结果表明,PPy-NW/PET电极材料的性能更优异,其首次放电和充电的比容量分别为124和98 mA[DK1]·h/g,且具有良好的柔性和稳定性。本文对柔性、轻质电极材料的制备及其在储能领域的应用提供了很好的思路。     

聚吡咯纳米阵列电极的光电化学

以多孔的铝阳极氧化膜(AAO)为模板制备了直径约为80 nm聚吡咯(PPy)纳米线的阵列电极, 并研究了它的光电化学响应. 结果表明, 在电极电位低于－0.1 V(vs Ag/AgCl)时出现的阴极光电流是由聚吡咯纳米线的p型半导体性质引起的, 其平带电位为－0.217 V. 聚吡咯纳米线的长度对光电流的影响较大, 最佳长度为42 nm. 这是因为在很短的聚吡咯纳米线阵列中PPy太少, 产生的光电流弱, 而在过长的聚吡咯纳米线阵列中光生电子在到达电极基底前易于与光生空穴复合而消失. 聚吡咯纳米线有可能作为纳米光电器件用于未来微器件系统.     

电化学制备有序聚苯胺纳米线阵列

以有序碳纳米管阵列电极为基底电极,在硫酸或高氯酸溶液中,分别探明不同电化学聚合方法以及苯胺单体浓度对聚苯胺形貌的影响. 结果表明：采用循环伏安法无法制备出聚苯胺纳米线;而应用恒电位法虽可制得聚苯胺纳米线,但纳米线不能形成有序阵列;只有应用恒电流方法,并且以高浓度苯胺的高氯酸溶液作为聚合溶液,方能制得有序聚苯胺纳米线阵列.     

聚吡咯/硫化镉核壳纳米线的制备及整流特性

以无机多孔氧化铝膜为模板,利用气相沉积和原位电化学沉积方法成功地制备了有机-无机杂化聚吡咯/硫化镉核壳纳米线;采用扫描电子显微镜和透射电子显微镜分析了聚吡咯/硫化镉核壳纳米线的表面形貌和微结构.结果表明,内部的聚吡咯纳米线紧紧依附在外部的硫化镉纳米管中,并且硫化镉纳米管被聚吡咯全部填充.与此同时,在聚吡咯/硫化镉核壳纳米线中,外部硫化镉壳与内部聚吡咯核之间存在电荷转移;聚吡咯和硫化镉之间形成有机-无机杂化的P-N界面,从而导致单根聚吡咯/硫化镉核壳纳米线显示出不同于外部壳和内部核的整流特性.     

聚吡咯纳米线凝胶的模板制备及储能与电化学传感性能

以配位聚合物凝胶为模板, 构筑均一的聚吡咯纳米线网络, 聚合后经简单处理除去模板, 得到性能优异的聚吡咯凝胶. 结果表明, 模板法合成的聚吡咯凝胶为由均一纳米线组成的三维网络结构, 具有良好的力学性能、 较大的比表面积及优异的电化学特性, 在0.28 A/g电流密度下, 比电容可达450 F/g, 在2.8 A/g电流密度下充放电1000次, 比电容仍可保持88.6%. 聚吡咯纳米线网络凝胶经葡萄糖氧化酶负载后得到柔性传感电极, 对低浓度(0.2 mmol/L)的葡萄糖具有快速响应性能, 有望用于超级电容器及生物电化学传感器等领域.     

Reactive Template Synthesis of Polypyrrole Nanotubes for Fabricating Metal/Conducting Polymer Nanocomposites

Unique nanocomposites of polypyrrole/Au and polypyrrole/Pt hybrid nanotubes are synthesized employing polypyrrole (PPy) nanotubes as an advanced support by solution reduction. The conducting polymer PPy nanotubes are fabricated by using pre‐prepared MnO₂ nanowires as the reactive templates. MnO₂ nanowires induce the 1D polymerization of pyrrole monomers and the simultaneous dissolution of the templates affords the hollow tube‐like structure. The loading content of metal nanoparticles in the nanocomposites could be adjusted by simply changing the amount of metal precursors. This work provides an efficient approach to fabricate an important kind of metal/conducting polymer hybrid nanotubes that are potentially useful for electrocatalyst and sensor materials.     

Relationship between chain length, disorder, and resistivity in polypyrrole films

The effects of the polymerization temperature and of voltammetric cycling on the chain length and the resistivity of polypyrrole films are investigated. The studies provide further proof for the existence of at least two different types of polypyrrole, the so-called PPy I and PPy II. As the electropolymerization of conjugated systems in contrast to normal polymerization reactions is a fully activated process, the generation of these different types of PPy depends on experimental parameters such as temperature or formation potentials. UV-vis measurements demonstrate that PPy II comprises significantly shorter chains than PPy I (8-12 vs 32-64 units); moreover, film conductivity is found to increase with the fraction of PPy II. This fraction is changed via the polymerization temperature as well as by cyclic voltammetry, both of which can induce a metal-insulator transition. The counter-intuitive relationship between resistivity and chain length is interpreted in terms of disorder-dominated transport, in which the shorter chains of PPy II support the formation of delocalized electronic states, thereby increasing the localization length. Thus, our results are in agreement with recent broadband reflectivity measurements.     

微电极研究: 吡咯在微电极上的聚合及膜的生长过程

研究NaNo3介质中吡咯在Pt微电极(r=10μm)上的聚合及聚吡咯膜的生长过程。利用微电极的快速传质特性证实了在聚合物生长过程中有可溶性低聚物中间体形成。研究表明聚吡咯膜的生长不仅是吡咯单体氧化偶联在聚合物的链端使链增长, 而且更主要的是溶液中低聚物的连续沉积形成新的聚合中心, 随后在Pt微电极上低聚物发生沉积而形成聚吡咯膜。     

Metal‐Free Electrocatalyst for Oxygen Reduction: Synthesis‐Controlled Density of Catalytic Centers and Impact on ORR

This work demonstrates a rapid and scalable route for the preparation of N‐doped carbon spheres of 80–120 nm via pyrolysis of polypyrrole as the only carbon and nitrogen source. The resulting porous catalyst has a nitrogen doping level of 6–8 at%. Electrochemical studies show that N‐doped C is very active toward oxygen reduction in alkaline electrolyte and the mechanism of ORR process is controlled by the surface concentration of catalytic active sites that promote either a direct four‐electron or two‐electron process. An interesting observation is that we can generate precursors for the N‐doped carbon with desirable particle size, shape and with the preferential structure (linear polypyrrole from the α? α coupling during slow polymerization or cross‐linked polypyrrole from α? β coupling during fast polymerization) that promotes the formation of favorable catalytic sites for O₂ reduction. The XPS analysis in conjunction with RDE voltammetry highlights the effect of polymer precursor synthesis on the chemical structure and a resulting electrochemical activity of the N‐doped carbon materials.     

Coordinated organogel templated fabrication of silver/polypyrrole composite nanowires

A new method to fabricate metal/conducting polymer composite nanowires is presented by taking silver/polypyrrole composite nanowires as an example.A silver(Ⅰ)-coordinated organogel as template was prepared firstly,and redox-polymerization of pyrrole took place on the gel fiber,giving product of silver/polypyrrole nanowires.The silver/polypyrrole nanowires were characterized by multiple techniques.This strategy could be carried out in one-step procedure at room temperature,and it proves the utility of coordinated organogels in template synthesis of polymer nanostructures.     

Controllable synthesis of conducting polypyrrole nanostructures

Wire-, ribbon-, and sphere-like nanostructures of polypyrrole have been synthesized by solution chemistry methods in the presence of various surfactants (anionic, cationic, or nonionic surfactant) with various oxidizing agents [ammonium persulfate (APS) or ferric chloride (FeCl3), respectively]. The surfactants and oxidizing agents used in this study have played a key role in tailoring the nanostructures of polypyrrole during the polymerization. It is inferred that the lamellar structures of a mesophase are formed by self-assembly between the cations of a long chain cationic surfactant [cetyltrimethylammonium bromide (CTAB) or dodeyltrimethylammonium bromide (DTAB)] and anions of oxidizing agent APS. These layered mesostructures are presumed to act as templates for the formation of wire- and ribbon-like polypyrrole nanostructures. In contrast, if a short chain cationic surfactant octyltrimethylammonium bromide (OTAB) or nonionic surfactant poly(ethylene glycol) mono-p-nonylphenyl ether (Opi-10) is used, sphere-like polypyrrole nanostructures are obtained, whichever of the oxidizing agents mentioned above is used. In this case, micelles resulting from self-assembly among surfactant molecules are envisaged to serve as the templates while the polymerization happens. It is also noted that, if anionic surfactant sodium dodeyl surfate (SDS) is used, no characteristic nanostructures of polypyrrole were observed. This may be attributed to the doping effect of anionic surfactants into the resulting polypyrrole chains, and as a result, micelles self-assembled among surfactant molecules are broken down during the polymerization. The effects of monomer concentration, surfactant concentration, and surfactant chain length on the morphologies of the resulting polypyrrole have been investigated in detail. The molecular structures, composition, and electrical properties of the nanostructured polypyrrole have also been investigated in this study.     

Patterned Growth of Vertically Aligned Polypyrrole Nanowire Arrays

A facile strategy for preparing vertically aligned polypyrrole (PPy) nanoarrays with precisely controlled density and quantity is presented. The method involves two steps: (1) the fabrication of the patterned substrate via electron beam lithography and (2) the controlled growth of PPy nanowires via electrochemical polymerization on the patterned substrate. The electrical property of a single PPy nanowire is investigated via in situ conducting probe atomic force microscopy.     

Surface molecularly imprinted nanowires for biorecognition

Herein we present a novel method for preparation of surface molecularly imprinted size-monodisperse nanowires. The imprint molecule is immobilized on the pore walls of a silane-treated nanoporous alumina membrane. The nanopores are then filled with the monomer mixture, and the polymerization is initiated. The alumina membrane is subsequently removed by chemical dissolution, leaving behind polypyrrole nanowires with glutamic acid binding sites situated at the surface. These nanowires can be dissolved in aqueous media, and their applications therefore should be compatible with procedures in which biological antibodies might otherwise be used. For example, the analyte molecule can be tagged with various markers, such as fluorescence probes and enzymes, whereby the problem of steric hindrance is avoided. Furthermore, these surface-imprinted nanowires are likely suited for imprinting and recognition of large-molecular-weight peptides and proteins. Related work is currently being undertaken in our laboratory.     

Synthesis of ordered spiral and ring-like polypyrrole nanowires in cetyltrimethylammounium bromide crystalline suspension

Spiral dislocation morphology on the surface of cetyltrimethylammounium bromide (CTAB) crystallites has been discovered for the first time. By addition of ammonium peroxydisulfate into CTAB crystalline suspension, a drastic change in the morphology of result crystallites is observed from spiral to two dimensional (2D) islands. The spiral and 2D-island structures of these crystallites could be use as the templates for the synthesis of spiral and ring-like polypyrrole (PPy) nanowires, respectively, via direct chemical oxidative polymerization of pyrrole due to the oxidation reaction occurring preferentially at the steps of these crystallites. The mechanism of adsorption of pyrrole oligomers on the steps of these crystallites is proposed for the growth of PPy spiral and ring-like nanowires.