二元合金团簇CoGe-n(n=1~12)的结构和稳定性

用密度泛函(DFT)方法与反射式飞行时间质谱及光电子能谱的实验结果相结合, 研究了二元合金团簇负离子CoGe-n(n=1~12)的结合能、几何结构与电子结构. 理论计算得到的电子亲和势(EA)光电子能谱测量的结果符合得较好. 通过分态密度(PDOS)分析了s, p和d轨道电子的相互作用规律. 讨论了团簇的稳定性, 认为CoGe-10具有幻数团簇的性质.     

PETN基PBX结合能和力学性能的理论研究

PETN(季戊四醇四硝酸酯)是著名的硝酸酯类猛炸药,用量子力学(QM)、分子力学(MM)和分子动力学(MD)方法,计算模拟其与高聚物组成的PBX(高聚物粘结炸药)的结合能和力学性能.以AM1-MO法和MM方法取PETN与系列高聚物的尺寸匹配原子簇模型,经几何全优化计算,发现两种方法求得的结合能彼此线性相关.对PETN超晶胞及其与系列氟聚物组成的双组分PBX,实施COMPASS力场下的分子动力学(MD)周期性模拟,求得其弹性系数、拉伸模量、体模量、剪切模量和泊松比,发现添加少量高聚物确能有效改善炸药的力学性能.     

碘乙醇在Ni(100)表面的吸附和热分解-碳氢化合物氧化的中间产物：羟乙基和氧金属环

利用热脱附(TPD)实验和X射线光电子能谱(XPS)研究了碘乙醇在Ni(100)表面的吸附和热反应过程. 实验结果表明碘乙醇在100 K时以两种分子的形式吸附在Ni(100)的表面, 即: 以碘原子端吸附在表面或以碘原子端和羟基端同时吸附在表面. 由于两种吸附形式的分子的一致分解和吸附分子的不均匀性, 在140 K引起了较复杂的化学反应, 伴有少量的乙烯和水产生. 碘乙醇在150 K经过C—I键断裂, 有80%碘乙醇生成—O(H)CH2CH2—中间产物, 20%的碘乙醇生成羟乙基中间产物. 羟乙基在160 K的转化过程中包括两个互相竞争的化学反应: 与表面的氢原子进行还原反应生成乙醇, 或失去一个β-H原子生成表面乙烯醇. 另外, 在相同的温度下—O(H)CH2CH2—中间产物经过脱氢反应产生—OCH2CH2—氧金属环. 羟乙基和氧金属环都会发生异构, 分别在210 K和250 K生成乙醛, 这些乙醛一部分从表面脱出, 其余的部分发生分解反应产生氢气、水和一氧化碳. 在实验基础上, 进一步探讨了这种化学过程在催化中的作用和指导意义.     

碘乙醇在Ni(100)表面的化学热反应

利用热脱附(TPD)实验和X射线光电子能谱(XPS)研究了碘乙醇在Ni(100)表面的吸附和热反应过程. 实验结果表明, 碘乙醇在100 K温度下以两种分子的形式吸附在Ni(100)的表面, 既有碘原子端的吸附也有碘原子端和羟基端同时吸附在表面. 热分解反应发生在140 K, 伴有少量的乙烯和水产生. 碘乙醇在150 K经过C—I键断裂形成−O(H)CH2CH2−和羟乙基两种中间产物. 在160 K温度下−O(H)CH2CH2−脱去氢形成−OCH2CH2−氧金属环. 中间产物经过进一步分解氧化反应分别在210和250 K产生乙醛, 一部分乙醛从表面脱出, 而其余的则分解成氢气、水和CO.     

链状Salen型高分子席夫碱金属配合物的合成及表征

以对苯二甲酰氯为交联剂,利用界面聚合法合成了链状Salen型高分子席夫碱金属配合物PLSBM(M:CoⅡ,MnⅡ,ZnⅡ,CuⅡ),通过元素分析、红外光谱(FT-IR)、扫描电镜(SEM)、电感耦合等离子原子发射光谱(ICP-AES)和X射线光电子能谱(XPS)对结构进行了表征,发现PLSBM呈不规则的链状结构,配位金属离子与配体形成了稳定的配合物后金属离子的结合能增加了0.5～2.1eV。     

多壁碳纳米管的掺氮改性及场效应管特性研究

以二茂铁为前驱体, 提供催化剂与部分碳源, 三聚氰提供氮源与另外一部分碳源, 在硅基底上制备出了碳纳米管阵列. 碳纳米管为多壁结构, 单根碳纳米管的平均直径为50 nm. 碳纳米管的X射线光电子谱(XPS)在398.4 eV处出现特征峰, 表明为氮掺杂的碳纳米管. 用其制备的场效应管在室温大气环境下稳定地表现为n型场效应特性, 并且具有非常低的关闭状态电流(off-state current)以及良好的负门电压对漏极电流的抑制作用, 单位源漏偏压下漏极电流为100 pA量级. 实验中采用了源/漏电极不对称的绝缘层结构, 使得门电压对源漏两极的电场调制也不对称, 从而实现了对漏电极的门电压调制.     

PP/PP-g-MAH与铝板粘接界面相的XPS研究

用X射线光电子能谱(XPS)研究铝板/聚丙烯层状复合材料的粘接界面相，提出了粘接界面的化学反应机制.研究发现,聚丙烯(PP)中加入马来酸酐接枝聚丙烯(PP-g-MAH)时，铝板面上Al 2p、O 1s谱线明显向高结合能端移动，表明PP-g-MAH与铝板表面发生了化学反应，形成Al－O－C配位键.配位键的形成使界面粘接强度明显提高. PP中不含PP-g-MAH时，铝板面上Al 2p、O 1s谱线处于低结合能端，聚丙烯未与铝板表面形成化学配位作用.     

TATB基PBX结合能的分子动力学模拟

用分子动力学（MD）方法, 模拟计算了四种氟聚合物(聚偏二氟乙烯（PVDF）、聚三氟氯乙烯（PCTFE）、氟橡胶（F₂₃₁₁)、氟树脂(F₂₃₁₄))与TATB(1,3,5- 三氨基- 2,4,6- 三硝基苯)晶体的相互作用. 结果发现, 四种氟聚物与TATB的结合能大小排序为PVDF>F₂₃₁₁>F₂₃₁₄>PCTFE, 各氟聚物在TATB不同晶面上的结合能大小排序为(001)>(010)>(100), 结合能主要由分子间氢键决定.     

聚酰胺-胺树状分子接枝到方法修饰多壁碳纳米管

采用聚酰胺-胺树状分子(PAMAM)“接枝到”这一温和而简单易行的方法修饰多壁碳纳米管(MWCNTs),制备了一种树状分子/碳纳米管(MWCNTs-g-PAMAM)纳米复合材料。在水、甲醇和乙醇等极性溶剂中,该复合材料具有很好的分散性。通过傅立叶变换红外光谱(FTIR)、X-射线光电子能谱(XPS)、热重分析(TGA)和透射电子显微镜(TEM)等对MWCNTs-g-PAMAM纳米复合材料进行了表征。FTIR表明接枝修饰是PAMAM与MWCNTs的共价键结合,TGA数据表明PAMAM成功修饰于MWCNTs侧壁,且接枝到MWCNTs上PAMAM的量随其代数(G1.0～G4.0)的不同而不同,具体顺序为G2.0＞G1.0≈G3.0＞G4.0.     

含时波包法研究RbI光电子能谱的脉冲延迟效应

利用含时波包方法模拟不同泵浦-探测延迟时间下RbI分子1+3多光子电离时间分辨光电子能谱(TRPES). 模拟过程同时考虑了三光子电离过程和自电离过程. 计算结果表明, 泵浦-探测延迟时间的改变会影响光电子能谱(PES)的形状, 而这种影响实质上是由于强场的存在改变了相关势能面的位置以及势能面之间的交叉所导致的.     

Pd/SWNTs负载型催化剂的制备及其催化性能

利用单壁碳纳米管(SWNTs)自身的还原性, 将PdCl2溶液中的Pd2+直接还原成金属Pd负载在SWNTs表面上, 制备了具有良好催化性能的Pd/SWNTs负载型催化剂. 通过透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和热重分析(TG)对Pd/SWNTs 进行了表征, 并利用Suzuki反应对Pd/SWNTs的催化性能进行了测试. 实验结果表明, 用SWNTs与12 mmol·L-1的PdCl2的水溶液直接作用, 得到Pd/SWNTs催化材料的Pd负载量达到14.13%(w, 质量分数), 颗粒分散均匀, 粒径小(2 nm左右), 与SWNTs结合紧密; 用经过H2还原的Pd/SWNTs作催化剂, 在90 ℃下进行Suzuki反应, 30 min后反应就基本完成, 其联苯的产率达到98.10%, 催化活性较高, 可望广泛用于有机合成反应.     

Pyridine-functionalized single-walled carbon nanotubes as gelators for poly(acrylic acid) hydrogels

Pyridine-functionalized single-walled carbon nanotubes (SWNTs) are prepared from the addition of a pyridine diazonium salt to nanotubes. The location and distribution of the functional groups is determined by atomic force microscopy using electrostatic interactions with gold nanoparticles. The pyridine-functionalized SWNTs are able to act as cross-linkers and hydrogen bond to poly(acrylic acid) to form SWNT hydrogels. The pyridine-functionalized SWNTs are further characterized using Raman, FTIR, UV/vis-NIR, and X-ray photoelectron spectroscopy and thermogravimetric analysis-mass spectrometry.     

Nanostructured biosensors built by layer-by-layer electrostatic assembly of enzyme-coated single-walled carbon nanotubes and redox polymers

In this study, we describe the construction of glucose biosensors based on an electrostatic layer-by-layer (LBL) technique. Gold electrodes were initially functionalized with negatively charged 11-mercaptoundecanoic acid followed by alternate immersion in solutions of a positively charged redox polymer, poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)], and a negatively charged enzyme, glucose oxidase (GOX), or a GOX solution containing single-walled carbon nanotubes (SWNTs). The LBL assembly of the multilayer films were characterized by UV-vis spectroscopy, ellipsometry, and cyclic voltammetry, while characterization of the single-walled nanotubes was performed with transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. When the GOX solution contained single-walled carbon nanotubes (GOX-SWNTs), the oxidation peak currents during cyclic voltammetry increased 1.4-4.0 times, as compared to films without SWNTs. Similarly the glucose electro-oxidation current also increased (6-17 times) when SWNTs were present. By varying the number of multilayers, the sensitivity of the sensors could be controlled.     

Noncovalent functionalization of DNA-wrapped single-walled carbon nanotubes with platinum-based DNA cross-linkers

A method for noncovalent functionalization of DNA-wrapped single-walled carbon nanotubes (SWNTs) using platinum-based DNA cross-linkers is investigated. In particular, cisplatin and potassium tetrachloroplatinate are shown to bind to DNA that encapsulates SWNTs in aqueous solution. The bound platinum salt can then be reduced to decorate the DNA-encapsulated SWNTs with platinum nanoparticles. The resulting SWNT/DNA/Pt hybrids are investigated by optical absorption spectroscopy, circular dichroism spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and atomic force microscopy. The unique combination of catalytic activity of nanoscale platinum, biological functionality of DNA, and optoelectronic properties of SWNTs suggests a myriad of applications including fuel cells, catalysts, biosensors, and electrochemical devices.     

高温煅烧Mo改性的Fe／MgO催化剂用于制备管径分布均一的单壁碳纳米管

研究了在以甲烷化学气相沉积法制备单壁碳纳米管的过程中高温煅烧预处理(900℃煅烧10h)对Mo改性Fe/MgO催化剂的作用.发现这种预处理有利于Fe在催化剂中的稳定和分散,从而制备出管径均一的单壁碳纳米管.采用能谱元素分析、高分辨透射电镜、X射线衍射、比表面积测量、拉曼光谱和热重分析对样品进行了表征.结果表明,在碳纳米管生长的过程中,铁元素在催化剂表面富集,单壁碳纳米管生长于富集铁的纳米颗粒上,并存在碳管直径与铁颗粒尺寸的依赖关系.Mo存在时可煅烧形成FeMoO4复合氧化物,后者比MgFe2O4相更加稳定.Mo/Fe比例对提高单壁碳纳米管的生长密度、纯度与管径均一性等均有明显影响.上述研究对进一步精确控制制备单壁碳纳米管有重要意义.     

Water-soluble full-length single-wall carbon nanotube polyelectrolytes: preparation and characterization

HiPco single-wall carbon nanotubes (SWNTs) have been noncovalently modified with ionic pyrene and naphthalene derivatives to prepare water-soluble SWNT polyelectrolytes (SWNT-PEs), which are analogous to polyanions and polycations. The modified nanotubes have been characterized with UV-vis-NIR, fluorescence, Raman and X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The nanotube-adsorbate interactions consist of pi-pi stacking interactions between the aromatic core of the adsorbate and the nanotube surface and specific contributions because of the substituents. The interaction between nanotubes and adsorbates also involves charge transfer from adsorbates to SWNTs, and with naphthalene sulfonates the role of a free amino group was important. The ionic surface charge density of the modified SWNTs is constant and probably controlled by electrostatic repulsion between like charges. The linear ionic charge density of the modified SWNTs is similar to that of common highly charged polyelectrolytes.     

碳纳米管/超支化重氮盐自组装膜的制备及性能研究

利用静电吸附自组装技术将酸化处理后的单壁碳纳米管(SWNTs)与超支化重氮盐(DAS)组装成多层膜.利用紫外光谱、椭偏仪、原子力显微镜、扫描电镜、拉曼光谱等对自组装膜的生长过程、膜厚增长、自组装膜表面形貌以及纳米管在膜中的存在状态等进行了检测,并利用纳米压痕仪测试了自组装膜的硬度和弹性模量.研究结果表明,SWNTs与DAS不仅发生了静电吸附,而且还发生了化学交联.同时碳纳米管均匀分散在自组装膜中.这两种因素的共同作用使得自组装膜表现出良好的纳米力学性能,硬度达到2.0GPa左右,弹性模量达到10.0GPa左右,而且可以从基底上剥离下来成为独立支撑膜.     

In situ Raman studies on lithiated single-wall carbon nanotubes in liquid ammonia

The charge transfer induced lithiation of single-wall carbon nanotubes (SWNTs) was investigated by in situ monitoring by Raman spectroscopy as lithium was added incrementally to a dispersion of SWNTs in liquid ammonia. Charge transfer from liquid ammonia solvated lithium to the SWNTs led to intercalation of lithium into the SWNT ropes, as well as to the semi-covalent lithiation of the SWNTs. Raman spectra of the SWNTs recorded as lithium was added showed a 30 wavenumber downshift of the G band (1594 cm⁻¹) with the concomitant appearance of a new peak at 1350 cm⁻¹ that was assigned as the signature of the lithiated SWNTs. Addition of 1-iodododecane to the lithiated SWNTs resulted in the covalent attachment of dodecyl groups. The intercalation of lithium throughout the SWNT ropes led to complete dodecylation of all individual SWNTs.     

Preferential growth of single-walled carbon nanotubes on silica spheres by chemical vapor deposition

The preferential growth of single-walled carbon nanotubes (SWNTs) on silica spheres with various diameters was realized for the first time by chemical vapor deposition (CVD) of methane. SWNTs tend to wrap the silica spheres to form a new superstructure of uniform SWNT nanoclaws when the diameters of the silica spheres are larger than 400 nm. The SWNTs obtained on silica spheres have highly graphitic tubular walls as characterized by Raman spectroscopy and HRTEM. This is a new method to obtain tunable uniform elastic deformation of SWNTs, which may act as the model for the study about the effect of delocalized bending on the properties of SWNTs. In addition, the combination of SWNTs with monodispersed silica spheres could conveniently integrate SWNTs into photonic crystals.     

Aqueous dispersion, surface thiolation, and direct self-assembly of carbon nanotubes on gold

We report the efficient aqueous dispersion of pristine HiPco single-walled carbon nanotubes (SWNTs) with ionic liquid (IL)-based surfactants 1-dodecyl-3-methylimidazolium bromide (1) and 1-(12-mercaptododecyl)-3-methylimidazolium bromide (2), the thiolation of nanotube sidewalls with 2, and the controlled self-assembly of positively charged SWNT-1,2 composites on gold. Optical absorption spectra and resonance Raman (RR) data of obtained aqueous SWNT-1,2 dispersions are consistent with debundled and noncovalently functionalized nanotubes whose electronic properties have not been disturbed. Additionally, the dispersion of pristine nanotube material with surfactants 1 and 2 leads to a high degree of purification from carbonaceous particles. The chiralities of the 14 smallest semiconducting HiPco SWNTs in resonance with Raman excitation at 1064 nm (1.165 eV) were determined in SWNT-2 aqueous dispersion using UV-vis-NIR and RR spectra. X-ray photoelectron spectroscopy (XPS) and surface-enhanced resonance Raman scattering (SERRS) spectroscopy of SWNT-2 submonolayers on gold verified the encapsulation of individualized SWNTs with IL surfactants, the cleavage of S-S disulfide bonds formed in aqueous SWNT-2 suspensions, and the direct chemisorption of the SWNT-2 composite on bare gold via the Au-S bond. Aqueous dispersions of SWNTs with IL-based surfactants add biofunctionality to carbon nanotubes by imparting the positive surface charge necessary for interactions with cell membranes. Our technique, which purifies pristine nanotube material and produces water-soluble, positively charged nanotubes with pendent surface-active thiol groups, may also be translated to other carbon nanotubes and carbon nanostructures. Self-assembled, positively charged submonolayers of SWNTs can be further used for applications in cell biology and sensor technology.