浓硝酸处理碳纳米管对4-硝基苯酚的吸附性能研究

本文采用浓硝酸氧化法来改性多壁碳纳米管,用Raman光谱、SEM和分光光度计对改性前后的多壁碳纳米管对4-硝基苯酚溶液的吸附能力进行了比较研究。Raman光谱和SEM分析表明浓硝酸处理使碳纳米管端口打开,管变短,并且在表面引入了羟基、羧基等酸性官能团。采用分光光度计测定溶液浓度,计算出浓硝酸处理前后多壁碳纳米管对不同浓度4-硝基苯酚的吸附效率,实验结果表明经浓硝酸处理后的多壁碳纳米管的吸附效率有较大的提高。     

银离子络合物萃取DHA乙酯的络合机理研究

旨在通过测定二十二碳六烯酸DHA乙酯及其与银离子络合物的紫外光谱,研究络合前后光谱特征峰的移动规律,并用分子轨道理论对DHA乙酯－银离子的配位键作出解释,以揭示DHA乙酯与银离子络合物的结构和络合反应机理。研究表明,由于DHA乙酯与银离子发生了络合作用,使得络合物的紫外特征峰蓝移,相对于络合前而言,DHA乙酯与银离子络合物的最高占据轨道HOMO与最低空轨道LUMO之间的相对能量差加大,络合物外层价电子跃迁的两个能级间距离增大,电子跃迁需要更高的能量。     

并五苯分子光谱和激发态的密度泛函理论研究

采用密度泛函理论对并五苯分子做理论研究.在几何结构优化的基础上,对其进行频率分析得到了分子的红外光谱和喇曼光谱,并对谱线中的各峰值做了具体指认,同时也得到了分子的最高占据轨道和最低空轨道能隙为2.17 eV.利用含时密度泛函理论对其激发态计算,得到最低十个跃迁允许的单激发态.对前线分子轨道最高占据轨道和最低空轨道分析得到,C-C原子之间形成离域π键.结果表明：并五苯是一种良好的有机半导体材料,并具有很好的发光性能.     

单壁碳纳米管吸附联苯类有机物的荧光光谱分析

利用芳香族化合物对单壁碳纳米管进行了化学修饰,并利用荧光光谱以及时间分辨光谱对修饰后的单壁碳纳米管进行了表征分析.实验发现吸附对三联苯后有1个荧光峰位置发生了蓝移,这说明吸附过程使对三联苯的一些能级分布发生了变化.测量吸附前后对三联苯和蒽甲醇的荧光寿命,发现吸附后的荧光衰减曲线下降趋势更加明显,对曲线进行多指数拟合得出的荧光寿命及其数目发生了变化,分析了可能导致该现象的原因.     

单壁碳纳米管吸附酞菁类有机物的研究

利用苯氧基酞菁修饰单壁碳纳米管,并利用透射电子显微镜、紫外可见吸收光谱、荧光光谱以及拉曼光谱进行了表征分析.在透射电镜下观察到结合物呈现糖葫芦状,吸附后吸收光谱以及荧光光谱中峰的强度明显下降说明单壁碳纳米管吸附了大量的苯氧基酞菁,通过拉曼光谱发现吸附后单壁碳纳米管的拉曼光谱中主要峰的位置向长波数方向移动,原因是单壁碳纳米管吸附苯氧基酞菁前后状态的改变导致的.     

7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子的光谱和激发态的密度泛函理论研究

采用密度泛函理论(DFT)对7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素分子做理论研究。用B3LYP/6-31G(d,p)对其几何结构进行优化,得到其最稳定构型及能量。在优化结构的基础上,对其进行频率分析得到了分子的红外光谱和拉曼光谱,并对谱线中的各峰值做了具体指认,同时也得到了分子的最高占据轨道(HOMO)和最低空轨道(LUMO)能隙为2.150eV。利用含时密度泛函理论(TDDFT)对该分子的激发态进行计算,得到最低十个跃迁允许的单激发态。对前线分子轨道最高占据轨道和最低空轨道分析得到,C-C原子之间形成了离域π键。研究结果表明:7-(3,6-二硝基-N-p-乙烯基苯基咔唑)香豆素是一种良好的有机半导体材料,并具有很好的发光性能。     

外电场下L-茶氨酸分子的结构特征与光谱性质

L-茶氨酸(N-乙基-L-谷氨酰胺)是一类具有降压、抗氧化的非蛋白氨基酸,研究外场下它的结构和光谱特征有助于人们更好地认识L-茶氨酸分子的性质.基于密度泛函理论,利用B3LYP方法,在6-311g(d,p)基组水平上对L-茶氨酸分子进行几何构型优化,在此基础上计算L-茶氨酸分子在不同外电场下(0～0.0125 a.u.)的分子各键长与振动频率,得到对应的红外光谱.同时,在相同的基组下采用含时密度泛函方法(TD-DFT)计算外电场对分子的激发态、前线轨道和能隙的影响.结果表明:分子结构及其紫外、红外光谱都随外电场强度发生变化.随外电场的增加,伸缩振动频率红移,弯曲振动频率蓝移;最高占据轨道的能量(E_(HOMO))与最低空轨道的能量(E_(LUMO))发生改变,前线轨道能隙先小幅增加后随电场减小,分子活性先减小后增强;紫外吸收光谱先蓝移后红移.本研究对L-茶氨酸分子的检测、合成及其生物活性的研究可提供理论依据.     

不同激发波长下单壁碳纳米管与多壁碳纳米管的拉曼光谱比较

对不同激发波长下单壁和多壁碳纳米管的激光拉曼光谱进行了比较。发现单壁碳纳米管D峰强度和G峰强度的比值(ID/IG)几乎不随激发光子能量的改变而变化,多壁碳纳米管ID/IG值随着激发光子能量的增加以斜率0 3/eV减小。并对此现象进行了初步的分析。此外,还发现在1064nm激发波长下,单壁和多壁碳纳米管2500-3500cm-1之间拉曼峰的相对强度随着入射激光功率的增加而增加。     

自旋轨道耦合作用对碳纳米管电子能带结构的影响

本文考虑自旋轨道耦合作用的情况下,采用紧束缚近似螺旋对称模型计算了单壁碳纳米管的电子能带结构.研究发现:对于Armchair型单壁碳纳米管,自旋轨道耦合作用和弯曲效应共同导致了费米面Dirac点附近电子能带结构的能隙;对于Zigzag型和手性单壁碳纳米管,自旋轨道耦合作用使得电子最高占据态和最低未占据态产生能级劈裂,能级劈裂的大小不但与碳纳米管的直径和手性角密切相关,而且相对于费米面是不对称的;根据指数(n,m)可以将Zigzag型和手性单壁碳纳米管分为金属性碳纳米管(ν=0) 关键词： 单壁碳纳米管 自旋轨道耦合 紧束缚近似螺旋对称模型     

一氟二氯乙烷分子在外电场中的光谱特征和解离特性

利用密度泛函理论在B3LYP/6-311+G(d, p)水平上研究不同外加电场下(-0.05～0.05 a.u.)一氟二氯乙烷分子的光谱特征和解离特性,其中包括该分子基态结构、总能量、偶极矩、最高占据轨道能级、最低空轨道能级、能隙、红外光谱、拉曼光谱、紫外可见光吸收光谱及C原子与Cl原子间势能曲线等数据在电场下的变化趋势。在y轴方向上,随着负向电场的增强,C原子与Cl原子核间距增长、最高占据轨道能级减小,体系总能量、最低未占据轨道能级、能隙先增大后减小,偶极矩先减小后增加。外加电场会影响一氟二氯乙烷分子红外光谱、拉曼光谱与紫外可见光吸收光谱的吸收强度和吸收峰频率,红外光谱、拉曼光谱与紫外可见光吸收光谱随着电场变化出现红移或蓝移现象。C原子与Cl原子间势垒随着负向电场增加逐渐减小,并在电场达到-0.05 a.u.时C原子与其中一个Cl原子发生断裂,当分子中一个C—Cl键断裂后,施加强度为-0.04 a.u.的电场时另外一个C—Cl键发生断裂,分子在电场下发生逐步解离,研究结果完善了一氟二氯乙烷分子受外电场影响的理论数据。     

磁场辅助热处理金属化碳纳米管场发射性能

利用化学镀方法对多壁碳纳米管(multi-walled carbon nanotubes,MWNTs)表面金属化镀镍(MWNTs/Ni),采用丝网印刷制备MWNTs/Ni场发射阴极,并在磁场辅助下热处理所得阴极,研究磁场辅助热处理对MWNTs/Ni阴极的场发射性能的影响,经300mT磁场辅助热处理的MWNTs/Ni的场发射阴极开启场强约为0.80V·μm~(-1),场增强因子β约为16068,对单根MWNTs/Ni在磁场中的受力情况进行建模分析,实验结果表明:磁场辅助热处理有助于提高MWNTs/Ni在阴极表面的直立分布,提高了MWNTs/Ni的场发射性能。     

Broadband optical limiting performance of polymer-wrapped carbon nanotubes in the orange-NIR region

Soluble multi-walled carbon nanotubes (MWNTs) have been obtained by noncovalent modification with poly [2-methoxy,5-(2′-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV). For the composite MWNT/MEH-PPV, there is π-π interaction between the MEH-PPV and MWNTs in addition to the wrapping of the polymer. The nonlinear optical transmittance was measured using a nanosecond optical parametric oscillator pumped with a Nd:YAG system. Excellent optical limiting performance of the composite MWNT/MEH-PPV was observed both in the visible region of 590-680 nm and at the wavelength of 1064 nm. By means of time-correlated single-photon counting fluorescence measurement, an explanation based on the nonlinear absorption of MWNT dominated by the intermolecular energy transfer was proposed.     

Functional multi-walled carbon nanotube/polyaniline composite films as supports of platinum for formic acid electrooxidation

Embedding of carbon nanotubes in conducting polymeric matrices for various nanocomposites material is now a popular area. In this article, a concise chemical method has been described for the preparation of homogeneous nanocomposite of multi-walled carbon nanotube (MWNT)/polyaniline (PANI) by electrochemical codeposition. For this we functionalized the MWNTs via the diazotization reaction. This helped to disperse the nanotubes in aniline. The composite films were dispersed Pt by electrodeposition technique. The presence of MWNTs and platinum in the composite films was confirmed by XRD analysis and transmission electron microscopy (TEM). Four-point probe investigations revealed that the MWNT/PANI composite films exhibited a good conductivity. Cyclic voltammograms (CV) showed that Pt-modified MWNT/PANI composite films perform higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formic acid oxidation. The results imply that the MWNT/PANI composite films as a promising support material improves the electrocatalytic activity for formic acid oxidation greatly.     

Electron field emission from magnetic nanomaterial encapsulated multi-walled carbon nanotubes

The present work describes the field emission characteristics of nanoscale magnetic nanomaterial encapsulated multi-walled carbon nanotubes (MWNTs) fabricated over flexible graphitized carbon cloth. Ni/MWNTs, NiFe/MWNTs and NiFeCo/MWNTs have been synthesized by catalytic chemical vapor decomposition of methane over Mischmetal (Mm)-based AB₃ (MmNi₃, MmFe_1.5Ni_1.5 and MmFeCoNi) alloy hydride catalysts. Metal-encapsulated MWNTs exhibited superior field emission performance than pure MWNT-based field emitters over the same substrate. The results indicate that a Ni-filled MWNT field emitter is a promising material for practical field emission application with a lowest turn-on field of 0.6 V/μm and a high emission current density of 0.3 mA/cm² at 0.9 V/μm.     

Dynamic column buckling of multi-walled carbon nanotubes under axial impact load

This paper studies the dynamic column buckling of multi-walled carbon nanotubes (MWNTs) under axial impact load. The analysis is based on the continuum mechanics model and a simplified model for the van der Waals forces between adjacent layers. By introducing initial imperfections for MWNTs and applying the method of preferred mode, a buckling condition is derived for the buckling load and associated buckling mode. In particular, explicit expressions are obtained for double-walled carbon nanotubes (DWNTs). Finally, numerical calculations are worked out for a DWNT and a five-layer MWNT with different length-to-radius ratios.     

可溶性高聚物-多壁碳纳米管复合物的吸收光谱和光限幅性能研究

合成了三种可溶性高聚物嫁接的多壁碳纳米管复合物,包括聚乙烯基咔唑-多壁碳纳米管复合物(MWNTs-PVK),聚苯乙烯-多壁碳纳米管复合物(MWNTs-PSt)和聚甲基丙烯酸甲酯-多壁碳纳米管复合物(MWNTs-PMMA)。合成样品的TEM图显示出高聚物成功地包裹在碳纳米管外。样品的氯仿溶液UV-Vis吸收谱显示,复合物的紫外区与纯的多壁碳纳米管不同,有一些复杂的特征吸收峰,反映了高聚物与碳纳米管共价连接的作用。利用Z扫描技术通过527nm的纳秒激光脉冲激发研究了这三种复合物的非线性光学性质和光限幅性能。这三种复合物的氯仿溶液的光限幅性能很相似,并且优于纯多壁碳纳米管氯仿悬浮液和C60甲苯溶液。为解释观察到的结果,研究了样品的非线性折射,非线性吸收和非线性散射机制。结果显示,非线性吸收是引起样品光限幅的主要机制。     

Covalent attachment of polystyrene on multi-walled carbon nanotubes via nitroxide mediated polymerization

A new method to attach polymers on carbon nanotubes has been studied. We used nitroxide mediated polymerization (NMP) to graft polystyrene from multi-walled carbon nanotubes (MWNTs). Carboxyl groups on MWNTs were activated with thionyl chloride (SOCl₂) to give acyl chloride derivative (MWNT-COCl). NMP initiator was introduced to MWNT by esterification of 1-hydroxy-2-phenyl-2-(2′,2′, 6′, 6′-tetramethyl-1′-piperidinyloxy)ethane (HO-PE-TEMPO) with acyl chloride groups of MWNTs. The obtained MWNT-PE-TEMPO was used for initiation of bulk polymerization of styrene, yielding polystyrene-grafted MWNTs (MWNT-g-pSt). The resulting composites of MWNT-g-pSt were analyzed by TEM, SEM, FT-IR and TGA.     

Preparation of Pt–CeO2/MWNT nano-composites by reverse micellar method for methanol oxidation

We report the preparation of Pt–CeO₂ nanoparticles on the multi-walled carbon nanotubes (MWNTs) by a reverse micellar method. Transmission electron microscopy (TEM) analysis indicated that well-dispersed small Pt–CeO₂ nanoparticles were formed on the MWCNTs. X-ray diffraction (XRD) analysis confirmed the formation of the Pt–CeO₂ nanoparticles on the MWNTs. Cyclic voltammetry (CV) results demonstrated that the Pt–CeO₂/MWNT exhibited a higher methanol oxidation than did the Pt/MWNT catalyst. The CO stripping test showed that CeO₂ can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation.     

1,5-萘二胺衍生物的光谱分析及发光性能研究

合成了一种纯度较高的1,5-萘二胺衍生物(NPN),制备了NPN薄膜.利用紫外-可见吸收光谱和荧光发射光谱研究了NPN的发光行为,并结合电化学循环伏安法研究了其电子能级结构.结果表明,NPN的荧光光谱表现出明显的溶剂效应,认为其发生了从电子给体N原子到电子受体芳环之间的分子内电子转移,形成分子内电子转移络合物;从NPN薄膜与其溶液的吸收光谱峰值比较中看出吸收峰红移,认为薄膜中分子形成"J-聚集体";NPN的HOMO能级为-5.74 eV,光学禁带为2.79 eV;在365 nm紫外光的激发下,产生发光峰在448.6 nm附近、谱线带宽为72.6 nm的蓝光发射,发光亮度高,色纯度高.