氧化铝模板上定向纳米碳管的快速生长及超声切短

在阳极氧化铝（AAO）模板上电沉积催化剂,快速生长了定向纳米碳管,纳米碳管以顶部生长模式生长.采用了超声的方法来切短露头于AAO模板的纳米碳管,增加纳米碳管膜的定向性.结果显示随着超声时间的增加,纳米碳管的定向性增加.位于纳米碳管膜顶部的催化剂在碳管切短的同时被去除,得到了顶部开口的纳米碳管.解释了纳米碳管被超声切短的机理.     

Fe2O3/Al2O3二元气凝胶合成高质量单壁纳米碳管

通过溶胶和超临界干燥方法制得了Fe₂O₃/Al₂O₃二元气凝胶，其比表面积和孔隙体积分别为246 m²·g^-1和1.89 cm³·g^-1，并具有较宽的孔径分布。以Fe₂O₃/Al₂O₃二元气凝胶作催化剂，通过甲烷催化裂解成功地合成了高质量的单壁纳米碳管。利用FESEM、TEM和HRTEM、Raman光谱等分析手段研究了反应温度对单壁纳米碳管生长的影响。结果表明在900 ℃时合成单壁纳米碳管的质量较高，并且合成的炭产物为毡状，该炭产物主要为高质量的单壁纳米碳管。     

Y2O3/纳米碳管复合粒子的结构及其对高氯酸铵热分解性能的研究

采用溶胶-凝胶法制备了Y₂O₃/纳米碳管复合粒子, 并用SEM, XPS, FT-IR和XRD对Y₂O₃/纳米碳管复合粒子的形貌和微观结构进行了表征. 结果表明, 纳米碳管有效承载了Y₂O₃, Y₂O₃连续均匀地负载在纳米碳管的表面, 负载量为19.53%. FT-IR 和XPS证明了Y₂O₃粒子和纳米碳管表面之间发生了化学键合. 用三种方法将相同比例的Y₂O₃/纳米碳管复合粒子与高氯酸胺(AP)进行混合, 采用差热分析(DTA)研究了三种混合样品中Y₂O₃/纳米碳管复合粒子对高氯酸铵热分解的催化性能. 结果表明, 三种混合样品中的Y₂O₃/纳米碳管复合粒子都能催化高氯酸铵的热分解, 其中通过水溶剂混合的样品中Y₂O₃/纳米碳管复合粒子的催化效果优于另外两种. 与纯高氯酸铵相比, 其样品中高氯酸铵的高温分解峰温降低了168.5 ℃, 表观分解热由371 J•g^－1提高到1410 J•g^－1. 并用不同样品中高氯酸铵热分解动力学参数对所得结果进行了理论分析.     

Y2O3/纳米碳管复合粒子的结构及其对高氯酸铵热分解性能的研究

采用溶胶-凝胶法制备了Y₂O₃/纳米碳管复合粒子, 并用SEM, XPS, FT-IR和XRD对Y₂O₃/纳米碳管复合粒子的形貌和微观结构进行了表征. 结果表明, 纳米碳管有效承载了Y₂O₃, Y₂O₃连续均匀地负载在纳米碳管的表面, 负载量为19.53%. FT-IR 和XPS证明了Y₂O₃粒子和纳米碳管表面之间发生了化学键合. 用三种方法将相同比例的Y₂O₃/纳米碳管复合粒子与高氯酸胺(AP)进行混合, 采用差热分析(DTA)研究了三种混合样品中Y₂O₃/纳米碳管复合粒子对高氯酸铵热分解的催化性能. 结果表明, 三种混合样品中的Y₂O₃/纳米碳管复合粒子都能催化高氯酸铵的热分解, 其中通过水溶剂混合的样品中Y₂O₃/纳米碳管复合粒子的催化效果优于另外两种. 与纯高氯酸铵相比, 其样品中高氯酸铵的高温分解峰温降低了168.5 ℃, 表观分解热由371 J•g^－1提高到1410 J•g^－1. 并用不同样品中高氯酸铵热分解动力学参数对所得结果进行了理论分析.     

稀碱溶液中水热法制备柔性TiO2纳米须薄膜的生长机制及表征

以柔性不锈钢基底上经磁控溅射沉积的钛膜为钛源, 在1 mol·L^-1的低浓度NaOH溶液中水热法制备了朝基底上方取向生长的大长径比柔性TiO₂纳米须薄膜, 考察了钛膜沉积条件对纳米须薄膜的影响, 系统研究了水热反应条件对薄膜生长过程的影响及TiO₂纳米须薄膜的形成机制. 通过场发射扫描电镜(FESEM)、X射线能谱仪(EDS)、高分辨透射电子显微镜(HRTEM)、X射线衍射仪(XRD)等对样品进行了表征. 结果表明, 与室温沉积的钛膜相比, 600 ℃下沉积的钛膜水热后得到的纳米线薄膜与基底的附着力更好. 所得TiO₂纳米须为单晶锐钛矿, 经由Na₂Ti₂O₄(OH)₂、H₂Ti₂O₅·H₂O转变而来. 纳米须形成于水热阶段, 平行于Na₂Ti₂O₄(OH)₂的(100)晶面择优取向生长, 纳米须经历了纳米片→纳米线束→纳米线的裂解生长过程. 朝基底上方取向生长的纳米须薄膜的形成是低浓度NaOH溶液与较高水热温度(220 ℃)协同作用的结果. 进一步在Na₂SO₄溶液中研究了薄膜电极的光电化学性能, 结果表明, TiO₂纳米须薄膜的光电性能明显优于零维纳米颗粒薄膜和二维纳米片薄膜, 显示了良好的应用前景.     

AgPd双金属纳米空心球的合成及其催化性能

以Ag纳米颗粒为牺牲模板,H₂PdCl₄为前驱体,抗坏血酸为还原剂,聚乙烯吡咯烷酮为表面活性剂,在70 ℃下采用电偶置换法结合还原法制备出AgPd双金属纳米空心球。采用紫外可见光谱、粉末X射线衍射、透射电镜结合能量色散等手段对由不同体积的0.01 mol·L^-1 H₂PdCl₄溶液制备的产物进行结构表征。结果表明,随着H₂PdCl₄溶液体积的增加,产物的空心化程度逐渐升高,晶粒的尺寸逐渐增大。当 H₂PdCl₄溶液体积为 120 μL时,合成的 AgPd双金属纳米空心球组成和结构较为均匀,其粒径约为 25 nm,壳层厚度 2~3 nm。双金属中,由于 Ag 和 Pd 电负性的差异,电子从 Ag 转移到了 Pd,使 Pd 表面出现电子富集区,显著提高了其催化效率。将所合成的AgPd双金属以及纯金属Ag和Pd作为催化剂,分别用于硼氢化钠催化还原4-硝基苯酚的反应,发现AgPd双金属的催化性能远高于纯金属Ag和Pd,其中AgPd-120纳米空心球(H₂PdCl₄溶液体积120 μL)作催化剂时的反应速率常数最高,是同等尺寸纯Ag纳米球的24.0倍,纯Pd纳米立方体的14.7倍。     

氟离子与磺化反应改性多壁纳米碳管催化剂的制备、表征及催化酯化反应合成油酸甲酯性能

通过高温浸渍法,对多壁纳米碳管进行了氟离子与浓硫酸磺化反应修饰改性处理,制备了一种新型Lewis酸型催化剂F^--SO₄^2-/MWCNTs,并通过透射电镜、拉曼光谱、X射线光电子能谱、吡啶吸附红外光谱、X射线荧光光谱、X射线衍射和NH₃程序升温脱附等表征手段对其的物理化学性能进行了表征分析,进而对多壁纳米碳管经F-与浓硫酸磺化反应修饰改性后所出现的结构与催化性能变化的内在影响规律进行了探索。以F^--SO₄^2-/MWCNTs为催化剂,以甲醇和油酸为原料,对其在应用于催化酯化反应合成油酸甲酯过程中的活性进行了研究。结果表明：当反应温度为65℃、醇油物质的量之比为12：1、催化剂质量占反应物总质量的0.9%、反应时间为6 h,油酸的转化率最高,达到了90%。高催化活性可归因于随着氟元素的加入,提高了SO₄^2-的插层作用效果,从而增加了酸性活性位的数量;此外,S=O键具有电子诱导效应,而F-有强负电性,两者之间发生强烈的相互作用后形成了F-S键,使S=O的吸电子效应大幅度增强,从而加剧了F^--SO₄^2-/MWCNTs催化剂的体系电荷不平衡趋势,导致催化剂中的正电荷过剩,使催化剂中的酸性活性位以Lewis酸为主,有效的避免了单纯磺化反应作用所生成的催化剂的酸性活性位以Brönsted酸型为主,而易在富含水的反应介质中发生水合作用而降低,甚至失去催化活性的现象发生。     

WC/纳米碳管复合材料制备及其电化学性能

碳化钨具有类铂催化性能和较强的抗中毒能力, 但其催化活性远低于铂等贵金属催化剂. 如何提高其催化活性是碳化钨应用研究所面临的主要难点与热点之一. 为寻找改善碳化钨催化性能的技术方法, 本文将表面修饰与原位还原碳化技术相结合, 成功制备了碳化钨/纳米碳管复合材料, 采用XRD, HRTEM等手段对其形貌和晶相组成进行了表征, 并应用粉末微电极对其电催化性能进行了评价. 实验结果表明, 样品由碳化钨颗粒和纳米碳管组成, 碳化钨为形态不规则纳米颗粒, 均匀地生长于纳米碳管的外表面; 在碱性溶液中, 复合材料对对硝基苯酚的电催化性能明显强于具有介孔结构的纯碳化钨样品. 这说明将碳化钨复合到纳米碳管的外表面是提高碳化钨电催化活性的有效技术方法之一.     

磁性普鲁士蓝纳米颗粒的合成及其化学修饰电极的制作

利用FeSO₄与FeCl₃合成了超细磁性Fe₃O₄纳米颗粒, 并进一步利用该纳米颗粒与铁氰酸钾在酸性溶液(pH～2)中的化学反应成功制备了一种新型的磁性普鲁士蓝纳米颗粒; 研究了该磁性颗粒的磁学性能, 通过磁力将其修饰于固体石蜡碳糊电极表面制成了化学修饰电极, 考察了该电极对过氧化氢的电催化还原及对水合肼的电催化氧化特性. 该化学修饰电极可对过氧化氢和水合肼进行测定, 线性范围分别为过氧化氢2×10^－6～5×10^－3 mol/L, 水合肼7.2×10^－7～3.6×10^－4 mol/L. 利用磁性普鲁士蓝纳米颗粒制得的修饰电极具有催化性能高、稳定性好、表面易更新等优点.     

纳米碳管表面羧基化及其电还原性能

应用红外吸收光谱、扫描电子显微镜分别对纳米碳管和硝化后的纳米碳管进行表征,将其制备成粉末微电极,并在碱性溶液中测试它对对硝基苯酚的电还原性能.实验表明:经硝化处理后,碳管表面修饰了羰基,其电还原性能明显提高.依据实验结果探讨了硝化后纳米碳管于对硝基苯酚电还原过程中的反应机理.     

Growth Mechanism of Vertically Aligned Carbon Nanotube Arrays

Vertically aligned multi-walled carbon nanotube arrays grown on quartz substrate are obtained by co-pyrolysis of xylene and ferrocene at 850 oC in a tube furnace. Raman spectroscopy and high resolution transmission electron microscopy measurements show that the single-walled carbon nanotubes are only present on top of vertically aligned multi-walled carbon nanotube arrays. It has been revealed that isolated single-walled carbon nanotubes are only present in those floating catalyst generated materials. It thus suggests that the single-walled carbon nanotubes here are also generated by floating catalyst. Vertically alignedcarbon nanotube arrays on the quartz substrate have shown good orientation and good graphitization. Meanwhile, to investigate the growth mechanism, two bi-layers carbon nan-otube films with di erent thickness have been synthesized and analyzed by Raman spectroscopy. The results show that the two-layer vertically aligned carbon nanotube films grow “bottom-up”. There are distinguished Raman scattering signals for the second layer itself, surface of the first layer, interface between the first and second layer, side wall and bottom surface. It indicates that the obtained carbon nanotubes follow the base-growth mechanism, and the single-walled carbon nanotubes grow from their base at the growth beginning when iron catalyst particles have small size. Those carbon nanotubes with few walls (typically <5 walls) have similar properties, which also agree with the base-growth mechanism.     

Asymmetric end-functionalization of multi-walled carbon nanotubes

Asymmetric end-functionalization of carbon nanotubes was achieved by sequentially floating a substrate-free aligned carbon nanotube film on two different photoreactive solutions with only one side of the nanotube film being contacted with the photoreactive solution and exposed to UV light each time. The resultant nanotubes with different chemical reagents attached onto their opposite tube-ends should be very useful for site-selective self-assembling of carbon nanotubes into many novel functional structures for various potential applications.     

多壁碳纳米管阵列电极的循环伏安行为

用化学气相沉积法在多孔氧化铝模板中沉积有序碳纳米管阵列并制成电极.由循环伏安法实验得知,扩散控制电位下的电活性离子难以常规的扩散速度到达碳纳米管的内壁深处,绝大部分的碳纳米管内壁面积在这样的实验条件下未能充分利用,但临近管口处的一部分内壁对扩散有一定的贡献.对于电极/电解质界面的双电层电容而言,碳纳米管的所有内壁都有所贡献,其电容量可达68.7mF*cm-2(表观面积),表明碳纳米管电极具有制作超级电容器的重要应用价值.     

Catalytically active CNT–polymer-membrane assemblies: From synthesis to application

A new membrane electrode assembly set up for catalytic processes containing carbon nanotubes has been developed. The process includes the nanotube synthesis, sputter deposition of platinum as catalyst and the membrane casting. Aligned nanotube carpets were grown from toluene/ferrocene solutions and sputtered with platinum. Subsequently the assembly was investigated using cyclic voltammetry to confirm a sufficient catalyst activity. A procedure was developed to embed the carbon nanotubes doped with catalyst into SPEEK membranes, while preserving the aligned structure and keeping some surface area of the catalyst-doped nanotubes free of membrane material to allow for easy access to reactants. So far the best results were obtained using an aligned but somewhat loose nanotube structure and a deposition of 0.034 mg/cm² Pt, forming a combination of small catalyst clusters and a thin film. The assemblies are optimized in respect to application in fuel cells and functional membranes.     

碳纳米管阵列的气相沉积制备及场发射特性

运用酞菁铁热解法气相沉积制备了碳纳米管阵列.所得碳纳米管呈多壁结构.单根碳纳米管的平均直径约为25 nm，长度约4～5 μm，且具有很好的准直性.研究了碳纳米管阵列的平面场发射特性，相应的开启电压和阈值电压分别为1.28和2.3 V•μm－1，表明碳纳米管具有很强的场发射能力.利用场发射显微镜观察了碳纳米管阵列的场发射像，发现碳纳米管阵列的场发射主要集中在样品薄膜的边缘部位.这是由于碳纳米管密度过大而产生的屏蔽效应所致.     

Disposable Multiwalled Carbon Nanotube Printed Film Electrochemical Determination of Acetaminophen,Dopamine, and Uric Acid

A novel printed film consisting of multiwalled carbon nanotubes was fabricated on a polyethylene terephthalate substrate by means of a mass flexographic printing process. Potential applications of this film for electrochemical biosensing were examined through the oxidation of acetaminophen, dopamine, and uric acid in phosphate buffer (pH 7.0). The results demonstrate that the printed carbon nanotube film exhibits an enhanced electrochemical response toward these molecules. Dopamine and uric acid did not interfere with each other and, thus, their simultaneous determination may be performed. The results suggest the mass flexographic printing technique has potential application for the construction of low-cost, precise, and disposable multiwalled carbon nanotube films.     

Gold nanoparticle mediated formation of aligned nanotube composite films

We report on the formation of highly anisotropic nanotube composite materials, made by the attachment of gold nanoparticles to the surface of the single-walled carbon nanotubes, followed by preparation of an aligned composite film by compression in a Langmuir-Blodgett trough. The gold is attached in a one-step sonication procedure. The gold-modified nanotube material forms a stable suspension in toluene and has been characterized by atomic force and scanning force microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. The aligned films have highly anisotropic electrical properties, with a factor of approximately 3000 difference in the conductivity between the aligned and perpendicular directions.     

UV-light mediated decomposition of a polyester for enrichment and release of semiconducting carbon nanotubes

Purification of single-walled carbon nanotubes using conjugated polymers to selectively disperse either semiconducting or metallic nanotubes is effective and has received significant attention. However, the interaction between the conjugated polymer and the nanotube surface is very strong, making it difficult to remove the adsorbed polymer. Here, we report a poly(carbazole-co-terephthalate) polymer that is not only selective for semiconducting carbon nanotubes but can also be largely removed from the nanotube surface via irradiation with UV light. Irradiation of the polymer-nanotube dispersion causes degradation of ester linkages in the polymer backbone, effectively cutting the polymer into fragments that no longer bind strongly to the nanotube surface. Characterization of the electronic nature of the samples was carried out via the combination of absorption, Raman, and fluorescence spectroscopy. In addition, thermogravimetric analysis allowed determination of the amount of polymer left on the nanotube surface after irradiation and indicated that a large proportion of the polymer is removed. The reported methodology opens new possibilities for purification of semiconducting single-walled carbon nanotubes and their isolation from the polymeric dispersant.     

Achieving Direct Electrical Connection to Glucose Oxidase Using Aligned Single Walled Carbon Nanotube Arrays

Direct electron transfer between an electrode and the redox active centre of glucose oxidase, flavin adenine dinucleotide (FAD), is probed using carbon nanotube modified gold electrodes. Gold electrodes are first modified with a self‐assembled monolayer of cysteamine and then shortened single walled carbon nanotubes (SWNT) are aligned normal to the electrode surface by self‐assembly. The electrochemistry of these aligned nanotube electrode arrays is initially investigated using potassium ferricyanide which showed SWNT act as nanoelectrodes with the ends of the tubes more electrochemically active than the walls. Subsequently the nanotubes are plugged into the enzymes in one of two ways. In the first method, native glucose oxidase is covalently attached to the ends of the aligned tubes which allowed close approach to FAD and direct electron transfer to be observed with a rate constant of 0.3 s^?1. In the second strategy, FAD was attached to the ends of the tubes and the enzyme reconstituted around the surface immobilized FAD. This latter approach allowed more efficient electron transfer to the FAD with a rate constant of 9 s^?1.