Preparation of stimulus-responsive,polyfluorene-wrapped carbon nanotubes via palladium cross coupling

Decoration of carbon nanotube surfaces without damaging nanotube optoelectronic properties is an ongoing challenge. Here, we utilize Sonogashira coupling chemistry to decorate the nanotube surface without perturbing optoelectronic properties. Reactive, noncovalently functionalized polymer–nanotube complexes were prepared using a polyfluorene with aryl iodide groups in its side chains. The aryl iodides enable Pd cross coupling between polymer–nanotube complexes and small molecules or polymers derivatized with an alkyne. Modestly efficient coupling was found to occur under dilute conditions at elevated temperatures. Successful coupling between aryl iodide and alkyne partners was observed using infrared spectroscopy via the appearance of carbonyl stretches that originate from covalently linked, carbonyl-containing alkynes, and thermogravimetric analysis was used to measure reaction conversion under various conditions. Grafting of the hydrophobic polymer–nanotube complex with poly(ethylene glycol) enabled the dispersion to be transferred from organic to aqueous solution. This chemistry resulted in no damage to the nanotube sidewall, as evidenced by Raman spectroscopy. The aryl iodide-containing polyfluorene–nanotube complex was also coupled to a photoswitchable alkyne-containing spiropyran moiety and it was found that the photoswitch retained its functionality after coupling to the polymer–nanotube complex. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2723–2729     

Functionalized carbon nanotubes containing isocyanate groups

Functionalized carbon nanotubes containing isocyanate groups can extend the nanotube chemistry, and may promote their many potential applications such as in polymer composites and coatings. This paper describes a facile method to prepare functionalized carbon nanotubes containing highly reactive isocyanate groups on its surface via the reaction between toluene 2,4-diisocyanate and carboxylated carbon nanotubes. Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed that reactive isocyanate groups were covalently attached to carbon nanotubes. The content of isocyanate groups were determined by chemical titration and thermogravimetric analysis (TGA).     

电弧放电法制备大面积高纯单壁碳纳米管薄膜

介绍了一种制备大面积高纯度单壁碳纳米管(SWCNT)薄膜的新方法. 利用改进的电弧放电法, 在真空放电室内分别安装两枚石墨极板, 使之形成一个球冠型电容器. 使用这种新型装置, 可以在两枚球冠型石墨极板之间产生一个合适的附加电场和成膜基板, 通过控制放电时间, 可在阴极的球冠型石墨极板上制备出厚度从数微米至1毫米不等的SWCNT薄膜. 场发射扫描电子显微镜(FESEM)、高分辨透射电子显微镜(HRTEM)、拉曼光谱和热重分析(TGA)的表征结果表明, 这个方法可以高效地制备具有高纯度的SWCNT薄膜.     

Amphoteric doping of carbon nanotubes by encapsulation of organic molecules: electronic properties and quantum conductance

In order to investigate and optimize the electronic transport processes in carbon nanotubes doped with organic molecules, we have performed large-scale quantum electronic structure calculations coupled with a Green's function formulation for determining the quantum conductance. Our approach is based on an original scheme where quantum chemistry calculations on finite systems are recast to infinite, non-periodic (i.e., open) systems, therefore mimicking actual working devices. Results from these calculations clearly suggest that the electronic structure of a carbon nanotube can be easily manipulated by encapsulating appropriate organic molecules. Charge transfer processes induced by encapsulated organic molecules lead to efficient n- and p-type doping of the carbon nanotube. Even though a molecule can induce p and n doping, it is shown to have a minor effect on the transport properties of the nanotube as compared to a pristine tube. This type of doping therefore preserves the intrinsic properties of the pristine tube as a ballistic conductor. In addition, the efficient process of charge transfer between the organic molecules and the nanotube is shown to substantially reduce the susceptibility of the pi electrons of the nanotube to modification by oxygen while maintaining stable doping (i.e., no dedoping) at room temperature.     

One-pot triple functionalization of carbon nanotubes

Carbon nanotubes (CNTs) are very promising as carriers for the delivery of bioactive molecules. The multifunctionalization of CNTs is necessary to impart multimodalities for the development of future CNT-based multipotent therapeutic constructs. In this context, we report the first example of covalent trifunctionalization of different types of CNTs. Our strategy is a simple and efficient methodology based on the simultaneous functionalization of the nanotube surface with three different active groups. The reaction is performed in one step by arylation with diazonium salts generated in situ. The CNTs are functionalized with benzylamine moieties blocked with three different protecting groups that can be selectively removed under specific conditions. The trifunctionalized CNTs were characterized by TEM, thermogravimetric analysis, and Raman and UV/Vis/NIR spectroscopy, while the amine loading was determined by using the Kaiser test. The sequential removal of the protecting groups of the amine functions allows the grafting of the molecules of interest on the nanotube surface to be controlled.     

Thermal decomposition and electron microscopy studies of single-walled carbon nanotubes

Thermoanalytical and electron microscopic methods were used as characterisation tools for the determination of the composition of single walled carbon nanotube samples. Acid purification method of single-walled carbon nanotubes (SWCN) proved to be effective, resulting in a three fold increase in the percentage of SWNTs present in the purified product as determined by thermogravimetric analysis. In this work we report the thermogravimetric analysis by conventional and high resolution methods of the raw SWNTs and purified SWNTs.     

Cetyltrimethylammonium bromide-coated titanate nanotubes for solid-phase extraction of phthalate esters from natural waters prior to high-performance liquid chromatography analysis

As a novel nanomaterial, titanate nanotube has attracted considerable attention recently. However, most of the research work is focused on the preparation of this nanomaterial, and there is lack of information about its application in the fields of environmental monitoring and analytical chemistry. The purpose of our study is to investigate the feasibility of titanate nanotubes as an adsorbent for solid-phase extraction of several phthalate esters. The titanate nanotubes in this study were prepared by alkaline hydrothermal method. The cationic surfactant cetyltrimethylammonium bromide (CTAB)-titanate nanotube system was adopted based on hemimicelles/admicelles formed on the mineral oxide surface. It was shown in the batch experiment that the highest adsorption of phthalate esters onto the CTAB-titania and -titanate nanotube system occurred when the CTAB was varied from 100 to 200mgg(-1) titania or 80 to 300mgg(-1) titanate nanotube separately. According to the fluorescent spectra of a molecular probe, N-phenyl-1-naphthylamine, and the binding constant of solute in CTAB admicelles, the CTAB-titanate nanotube admicelles was more hydrophobic than CTAB-titania admicelles. Consequently, CTAB-titanate nanotube admicelles system was suitable for concentrating phthalates esters in water. An admicelle column was prepared with 100mg of titanate nanotubes by passing through 100mgg(-1) titanate nanotube of CTAB. And excellent collection yields were obtained for all the analytes when the sample volume was up to 1000mL. Under the optimal conditions, the detection limits found for di-n-propyl-phthalate, di-n-butyl-phthalate, di-cyclohexyl-phthalate, and di-n-octyl-phthalate were 39, 19, 35 and 20ngL(-1), respectively. The developed method was successfully applied to the analysis of several real water samples and satisfactory recoveries were achieved. All the results indicated the application potential of titanate nanotubes as solid-phase extraction adsorbents to pre-treat water samples.     

Statistical sampling of carbon nanotube populations by thermogravimetric analysis

Carbon nanotubes are one of the most promising nanomaterials available with applications in electronics devices, sensing, batteries, composites and medicine. Strict control of the carbon nanotube chemistry and properties is necessary as the applications proceed into more specialized areas. Thermogravimetric analysis (TGA) is one analytical method currently utilized for the characterization of carbon nanotubes. Though TGA can provide quantitative measurements of the composition of a sample, many researchers do not ensure the variance of the sample is properly captured. This research demonstrates for four single-wall carbon nanotube (SWCNT) samples how to statistically evaluate the material with TGA to ensure that the variance within the material is represented. SEM results are used to help reach conclusions about purity of the material by providing a visual means for inspection. This data is used to select the SWCNT material with the lowest variability and highest quality, as evaluated by composition and reproducibility.     

碳纳米管在分析化学领域的研究进展

综述了碳纳米管自发现以来在分析化学领域中的一些研究成果，重点介绍了碳纳米管的制备、纯化、修饰以及作为一种新材料在分析化学中的应用前景。参考文献40篇。     

Light‐driven atom transfer radical polymerization on supramolecular complexes of conjugated polymers and single‐walled carbon nanotubes

Previous approaches used to decorate latently reactive conjugated polymer‐coated carbon nanotube complexes have utilized “grafting‐to” strategies. Here, we coat the carbon nanotube surface with a conjugated polymer whose side chains contain the radical initiator, α‐bromoisobutyrate, which enables atom transfer radical polymerization (ATRP) from the polymer–nanotube surface. Using light to generate Cu(I) in situ, ATRP is used to grow narrow dispersity polymer chains from the polymer–nanotube surface. We confirm the successful polymerization of (meth)acrylates from the polymer–nanotube surface using a combination of gel permeation chromatography and infrared spectroscopy. Strikingly, we demonstrate that nanotube optoelectronic properties are preserved after radical‐mediated polymer grafting using Raman spectroscopy and photoluminescence mapping. Overall, this work elucidates a method to grow narrow dispersity polymer chains from the polymer–nanotube surface using light‐driven radical chemistry, with concurrent preservation of nanotube optoelectronic properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2015–2020     

Influence of high vacuum annealing treatment on some properties of carbon nanotubes

Carbon nanotubes (CNTs) were synthesized using a chemical vapour deposition (CVD) method. The properties of CNTs before and after vacuum annealing treatment were studied using scanning electron microscopy (SEM), scanning tunneling microscopy/spectroscopy (STM/STS) and thermogravimetric analysis (TG). Field emission characteristics of the raw and vacuum heated (up to 650°C) carbon nanotube films (CNTFs) were measured in a diode system. Emissive properties of the CNTFs depend on an annealing process during which structural changes in the nanotube walls take place. The structural changes, related to saturation of dangling bonds, influence a rate of oxidation process and also improve the emissive field properties.     

Facile decoration of functionalized single-wall carbon nanotubes with phthalocyanines via "click chemistry"

We describe the functionalization of single-wall carbon nanotubes (SWNTs) with 4-(2-trimethylsilyl)ethynylaniline and the subsequent attachment of a zinc-phthalocyanine (ZnPc) derivative using the reliable Huisgen 1,3-dipolar cycloaddition. The motivation of this study was the preparation of a nanotube-based platform which allows the facile fabrication of more complex functional nanometer-scale structures, such as a SWNT-ZnPc hybrid. The nanotube derivatives described here were fully characterized by a combination of analytical techniques such as Raman, absorption and emission spectroscopy, atomic force and scanning electron microscopy (AFM and SEM), and thermogravimetric analysis (TGA). The SWNT-ZnPc nanoconjugate was also investigated with a series of steady-state and time-resolved spectroscopy experiments, and a photoinduced communication between the two photoactive components (i.e., SWNT and ZnPc) was identified. Such beneficial features lead to monochromatic internal photoconversion efficiencies of 17.3% when the SWNT-ZnPc hybrid material was tested as photoactive material in an ITO photoanode.     

JACOB: An enterprise framework for computational chemistry

Here, we present just a collection of beans (JACOB): an integrated batch‐based framework designed for the rapid development of computational chemistry applications. The framework expedites developer productivity by handling the generic infrastructure tier, and can be easily extended by user‐specific scientific code. Paradigms from enterprise software engineering were rigorously applied to create a scalable, testable, secure, and robust framework. A centralized web application is used to configure and control the operation of the framework. The application‐programming interface provides a set of generic tools for processing large‐scale noninteractive jobs (e.g., systematic studies), or for coordinating systems integration (e.g., complex workflows). The code for the JACOB framework is open sourced and is available at: www.wallerlab.org/jacob . © 2013 Wiley Periodicals, Inc.     

Thermogravimetric analysis of synthesis variation effects on CVD generated multiwalled carbon nanotubes

Changes in the thermogravimetrically determined oxidation behaviors of CVD-grown multiwalled carbon nanotubes with varying synthesis conditions are examined. Catalyst type and synthesis temperature are found to have a measurable impact upon nanotube stability, suggesting differing levels of crystalline perfection in the resulting nanotubes. The results provide evidence showing the catalytic effects of nanotube catalyst particles and their oxides upon the oxidation of nanotube carbon and graphite. The significance of thermogravimetric analysis as a characterization tool for carbon nanotubes is discussed.     

HPLC study of chlorin e6 and its molecular complex with polyvinylpyrrolidone

Several HPLC methods with UV detection were developed for qualitative and quantitative analysis of chlorin e(6) and photosensitizer Photolon either in the free form or upon pre-derivatization (methylation) under reversed- and normal-phase conditions. Optimum analysis conditions providing the best resolution of analytes were found at acidic pH where polar groups are completely protonated. The separation was performed by gradient elution with mobile phases of 0.08% trifluoroacetic acid and acetonitrile on an XTerra RP(18) column. The method was specific, accurate and precise, allowing the analysis of chlorin e(6) in the presence of numerous degradation products useful in the manufacturing process and quality control of chlorin e(6) and Photolon.     

自由软件R及其在化学中的应用

论述了在科学研究领域中推广自由软件的重要性,并就其中的典型代表———统计处理软件R在化学领域中的应用列举了三个实例:分子动力学数据的统计分析、物理化学实验数据处理及碳纳米管分子模型的构建,给出了详细操作步骤。除文中列举的实例外,R还可被应用于化学模式识别、图形制作等领域,是化学工作者处理实际问题的一大利器。     

扶手椅型单壁碳纳米管生长机理的理论研究

用Gaussian03程序中的AM1方法对扶手椅型单壁碳纳米管的生长机理进行了研究. 结果表明, 若碳纳米管生长的碳源是C2自由基, 则有一条反应途径可能是：C2自由基首先与碳纳米管的开口端形成一个中间体, 然后该中间体经过一个过渡状态, 形成产物；从(3, 3), (4, 4), (5, 5)到(6, 6), 其生长反应的活化能逐渐降低. 同时 研究发现, 活化能的高低与碳纳米管共轭程度的大小有关, 碳纳米管的共轭程度越大, 活化能越低；在靠近新形成的六元环的两侧, 碳纳米管可能优先继续生长.     

NH4F/H3PO4体系中阳极氧化法制备TiO2纳米管阵列

以价廉的Ni板代替常用的Pt片为阴极,纯钛为阳极,采用电化学阳极氧化法在NH4F-H3PO4体系中制备出TiO2纳米管阵列.详细研究了制备参数(溶液酸度、氟离子浓度、外加电压和氧化时间)对所获纳米管阵列形貌的影响.采用场发射扫描电镜(FE-SEM)和X射线衍射(XRD)对样品的形貌和晶相结构进行了表征.在最优化的条件下,可以获得形貌规整、表面干净、有序的TiO2纳米管阵列.纳米管阵列的平均管径为60 nm.管长约530 nm.采用阳极氧化法制备的纳米管阵列是非晶态的.经400℃热处理2 h后,可以转变为锐钛矿相.实验结果还发现,经过热处理后,纳米管阵列变得更为有序,管径扩大至约95 nm.     

Microwave-assisted extraction in closed vessel in food analysis

Microwave-assisted extraction (MAE) is an important technique in analytical chemistry. It offers several advantages over traditional extraction methods, such as improved extraction efficiency, shorter extraction times, reduced solvent consumption, and enhanced analyte recovery. Using microwaves, heat is directly applied to the sample, leading to rapid and efficient extraction of target compounds by enhancing the solubility and diffusion of the target compounds, thus requiring lower solvent volume. Therefore, MAE can be considered a more environmentally friendly and cost-effective option facilitating the transition toward greener and more sustainable analytical chemistry workflows. This contribution systematically reviews the application of MAE to a selection of target compounds/compounds classes of relevance for food quality and safety assessment. As inclusion criteria, MAE active temperature control and molecularly-resolved characterization of the extracts were considered. Contents include a brief introduction of the principles of operation, available systems characteristics, and key parameters influencing extraction efficiency and selectivity. The application section covers functional food components (e.g., phenols, diterpenes, and carotenoids), lipids, contaminants (e.g., polycyclic aromatic hydrocarbons and mineral oil hydrocarbons), pesticides, veterinary drug residues, and a selection of process contaminants and xenobiotics of relevance for food safety.     

Generic capillary electrophoresis conditions for chiral assay in early pharmaceutical development

Generic capillary electrophoresis (CE) conditions have been implemented for chiral separations in early pharmaceutical development. The chiral CE separations of several pharmaceutical samples at different stages of development, i.e., discovery, process chemistry, and investigative new drug application, have been obtained using sulfated beta-cyclodextrin (CD). Several sulfated beta-CDs have been screened to select an appropriate enantioselective agent. The use of a generic CE method allows for a convenient and rapid chiral recognition of different weak bases, with minimal or no method development. CE using sulfated beta-CD for the chiral separation of N-benzoyl methyl piperazine has been validated for linearity, precision, accuracy, limits of detection and quantitation (LOD, LOQ). Although less sensitive than a specific liquid chromatography method using a Chiralpak AD column, the overall performance of the chiral CE method was found comparable. Validation data demonstrate that a LOD of 0.1%, sufficient to fulfill regulatory requirements, is achievable by chiral CE.