Controllable‐Nitrogen Doped Carbon Layer Surrounding Carbon Nanotubes as Novel Carbon Support for Oxygen Reduction Reaction

Novel nitrogen‐doped carbon layer surrounding carbon nanotubes composite (NC‐CNT) (N/C ratio 3.3–14.3 wt.%) as catalyst support has been prepared using aniline as a dispersant to carbon nanotubes (CNTs) and as a source for both carbon and nitrogen coated on the surface of the CNTs, where the amount of doped nitrogen is controllable. The NC‐CNT so obtained were characterized with scanning electron microscopy (SEM), Raman spectroscopy, X‐ray photoelectron spectroscopy (XPS), and nitrogen adsorption and desorption isotherms. A uniform dispersion of Pt nanoparticles (ca. 1.5–2.0 nm) was then anchored on the surface of NC‐CNT by using aromatic amine as a stabilizer. For these Pt/NC‐CNTs, cyclic voltammogram measurements show a high electrochemical activity surface area (up to 103.7 m² g^–1) compared to the commercial E‐TEK catalyst (55.3 m² g^–1). In single cell test, Pt/NC‐CNT catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, resulting in an enhancement of ca. 37% in mass activity compared with that of E‐TEK.     

Structural Modification in Carbon Nanotubes by Boron Incorporation

We have synthesized boron-incorporated carbon nanotubes (CNTs) by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm⁻¹ in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds.     

Activity of Nitrogen Containing Carbon Nanotubes in Base Catalyzed Knoevenagel Condensation

The catalytic activity of Nitrogen containing Carbon Nanotubes (NCNT), grown from acetonitrile or pyridine over supported Fe-, Co or Ni catalysts at various conditions, were tested for the base catalyzed Knoevenagel condensation of benzaldehyde and ethylcyanoacetate. All NCNT displayed activity for the reaction with initial turn over frequencies between 9 × 10⁻³ and 5 × 10⁻² s⁻¹ which is comparable with to those of activated basic carbons and a rehydrated hydrotalcite. Furthermore, the initial activity per gram of catalyst of NCNT was related to the amount of pyridinic type nitrogen in the NCNT. However, the reaction rate decreased with time on stream which was explained by competitive adsorption of reactant and product. The reaction rate can be described using Langmuir–Hinshelwood type kinetics including product adsorption.     

Cell Creeping and Controlled Migration by Magnetic Carbon Nanotubes

Carbon nanotubes (CNTs) are tubular nanostructures that exhibit magnetic properties due to the metal catalyst impurities entrapped at their extremities during fabrication. When mammalian cells are cultured in a CNT-containing medium, the nanotubes interact with the cells, as a result of which, on exposure to a magnetic field, they are able to move cells towards the magnetic source. In the present paper, we report on a model that describes the dynamics of this mammalian cell movement in a magnetic field consequent on CNT attachment. The model is based on Bell’s theory of unbinding dynamics of receptor-ligand bonds modified and validated by experimental data of the movement dynamics of mammalian cells cultured with nanotubes and exposed to a magnetic field, generated by a permanent magnet, in the vicinity of the cell culture wells. We demonstrate that when the applied magnetic force is below a critical value (about F _c ≈ 10⁻¹¹ N), the cell ‘creeps’ very slowly on the culture dish at a very low velocity (10–20 nm/s) but becomes detached from the substrate when this critical magnetic force is exceeded and then move towards the magnetic source.     

Catalytic Routes Towards Single Wall Carbon Nanotubes

Single wall carbon nanotubes (SWCNT) have become a strategic material in the area of nanotechnologies nowadays, and catalytic chemical vapor deposition seems to be the most promising technique in view of an industrial-scale production. However, the selective catalytic production of single wall carbon nanotubes is still a challenge, since catalytic systems performances both in terms of selectivity and activity are still relatively low. One of the main challenges for the catalytic growth of SWCNT is the control of the catalyst nanoparticles size distribution along the high temperatures required by the process. This article provides a comprehensive overview of the state of the art of the strategies that have been followed to selectively grow single wall carbon nanotubes. It focuses on catalysts preparation and activity/selectivity and on the growth mechanism of these nanostructures. Particular attention is given to the identification of the parameters that control the selectivity of the reaction, such as the choice of the metal/support couple, the particle's sizes, and the chemical vapor deposition conditions.     

Folate Functionalized Boron Nitride Nanotubes and their Selective Uptake by Glioblastoma Multiforme Cells: Implications for their Use as Boron Carriers in Clinical Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is increasingly being used in the treatment of several aggressive cancers, including cerebral glioblastoma multiforme. The main requirement for this therapy is selective targeting of tumor cells by sufficient quantities of ¹⁰B atoms required for their capture/irradiation with low-energy thermal neutrons. The low content of boron targeting species in glioblastoma multiforme accounts for the difficulty in selective targeting of this very malignant cerebral tumor by this radiation modality. In the present study, we have used for the first time boron nitride nanotubes as carriers of boron atoms to overcome this problem and enhance the selective targeting and ablative efficacy of BNCT for these tumors. Following their dispersion in aqueous solution by noncovalent coating with biocompatible poly-l-lysine solutions, boron nitride nanotubes were functionalized with a fluorescent probe (quantum dots) to enable their tracking and with folic acid as selective tumor targeting ligand. Initial in vitro studies have confirmed substantive and selective uptake of these nanovectors by glioblastoma multiforme cells, an observation which confirms their potential clinical application for BNCT therapy for these malignant cerebral tumors.     

Catalytic Routes Towards Single Wall Carbon Nanotubes

Single wall carbon nanotubes (SWCNT) have become a strategic material in the area of nanotechnologies nowadays, and catalytic chemical vapor deposition seems to be the most promising technique in view of an industrial‐scale production. However, the selective catalytic production of single wall carbon nanotubes is still a challenge, since catalytic systems performances both in terms of selectivity and activity are still relatively low. One of the main challenges for the catalytic growth of SWCNT is the control of the catalyst nanoparticles size distribution along the high temperatures required by the process. This article provides a comprehensive overview of the state of the art of the strategies that have been followed to selectively grow single wall carbon nanotubes. It focuses on catalysts preparation and activity/selectivity and on the growth mechanism of these nanostructures. Particular attention is given to the identification of the parameters that control the selectivity of the reaction, such as the choice of the metal/support couple, the particle’s sizes, and the chemical vapor deposition conditions.     

磁性多壁碳纳米管吸附处理甲基橙模拟废水的研究

对多壁碳纳米管进行纯化处理后采用化学共沉淀法制成磁性多壁碳纳米管(mMWNT),研究了其对甲基橙废水的处理效果,考察了投加量、吸附时间、pH值、温度等因子的影响。结果表明,mMWNT成功负载了Fe3O4和γ-Fe2O3;mMWNTs投加量为6 g/L时甲基橙的去除率可达99.2%;甲基橙去除率随时间呈逐渐增大趋势直至吸附平衡;实验的最佳pH为1时,去除率最高;温度为30℃时,去除率达到80%。mMWNT吸附处理甲基橙模拟废水过程符合准二级吸附动力学方程。     

碳纳米管的改性及其应用

碳纳米管因其具有独特的物理化学性质在许多领域具有潜在的应用价值。碳纳米管表面改性是实现其应用价值的主要手段之一。介绍了碳纳米管表面改性方法的研究进展,以及改性碳纳米管在复合材料、医学、环保、储能等领域的一些应用。     

锂离子二次电池用负极炭材料的掺硼改性

掺杂法是进行锂离子二次电池用炭负极材料改性与修饰的方法之一,通过对国内外以硼作为掺杂原子进行炭负极材料改性的方法的总结,举例分析了浸渍法、包埋法和共混法掺硼的特点,并指出了目前掺硼工艺中存在的硼在炭材料中的分散不均匀和硼含量较低的两大问题。此外,总结介绍了前人关于硼与炭材料相互作用的机理,从理论上分析探讨了掺杂硼炭材料的特点以及掺杂硼炭材料用作锂二次电池负极的电化学性能。并且指出添加硼元素后,炭负极材料的各种容量都有所提高,而今后的任务之一就是降低不可逆容量。     

Preparation of Magnetic Carbon Nanotubes (Mag-CNTs) for Biomedical and Biotechnological Applications

Carbon nanotubes (CNTs) have been widely studied for their potential applications in many fields from nanotechnology to biomedicine. The preparation of magnetic CNTs (Mag-CNTs) opens new avenues in nanobiotechnology and biomedical applications as a consequence of their multiple properties embedded within the same moiety. Several preparation techniques have been developed during the last few years to obtain magnetic CNTs: grafting or filling nanotubes with magnetic ferrofluids or attachment of magnetic nanoparticles to CNTs or their polymeric coating. These strategies allow the generation of novel versatile systems that can be employed in many biotechnological or biomedical fields. Here, we review and discuss the most recent papers dealing with the preparation of magnetic CNTs and their application in biomedical and biotechnological fields.     

Adsorption Characteristics of Atrazine on Granulated Activated Carbon and Carbon Nanotubes

Adsorption of atrazine (ATZ) from aqueous solutions by granular activated carbon (GAC) and carbon nanotubes (CNT) was studied in a batch‐mode adsorption system at different initial concentrations of ATZ (1.0–30.0 mg L^–1) and at three temperatures of 288, 296 and 304 K. The adsorption isotherms of Langmuir, Freundlich, Polanyi–Manes, and Brunauer–Emmett–Teller (modified) were used to model the process. The adsorption kinetics followed a pseudo‐second‐order kinetic model. The thermodynamic parameters ΔH⁰, ΔS⁰, and ΔG⁰ of the adsorption were estimated. The thermodynamic parameters indicate that the adsorption process is spontaneous and exothermic.     

Jet Dispersion of Multiwall Carbon Nanotubes and Correlation with Suspension Rheology

A novel jet dispersion technique was developed and investigated which enabled excellent carbon nanotube (CNT) dispersion by high exfoliation at even very low pressure drops. Suitable procedures were developed for the characterization of agglomerate size and fraction of individual CNTs. The appropriate characterization enabled the definition of a dimensionless dispersing parameter and the development of a kinetic model that describes CNT dispersion in dependence of the volumetric energy input. The rheological behavior of CNT suspensions in steady-shear flows was investigated and demonstrated how the agglomerate fracture and CNT individualization influence the suspension viscosity.     

Large-Scale Fabrication of Boron Nitride Nanotubes via a Facile Chemical Vapor Reaction Route and Their Cathodoluminescence Properties

Cylinder- and bamboo-shaped boron nitride nanotubes (BNNTs) have been synthesized in large scale via a facile chemical vapor reaction route using ammonia borane as a precursor. The structure and chemical composition of the as-synthesized BNNTs are extensively characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and selected-area electron diffraction. The cylinder-shaped BNNTs have an average diameter of about 100 nm and length of hundreds of microns, while the bamboo-shaped BNNTs are 100–500 nm in diameter with length up to tens of microns. The formation mechanism of the BNNTs has been explored on the basis of our experimental observations and a growth model has been proposed accordingly. Ultraviolet–visible and cathodoluminescence spectroscopic analyses are performed on the BNNTs. Strong ultraviolet emissions are detected on both morphologies of BNNTs. The band gap of the BNNTs are around 5.82 eV and nearly unaffected by tube morphology. There exist two intermediate bands in the band gap of BNNTs, which could be distinguishably assigned to structural defects and chemical impurities.     

碳纳米管和偶联剂协同作用对热塑性复合材料力学性能的影响

将碳纳米管（CNTs）和硅烷偶联剂（AMEO）分散至纤维表面,制备聚芳硫醚（PAS）/玻璃纤维布/CNTs/AMEO复合材料,并探究复合材料的表面形貌和力学性能。结果表明：未经偶联剂处理的体系中,CNTs与纤维的结合性较弱。将CNTs进行羧化和偶联剂处理,能够提高CNTs和纤维之间的结合强度,提升纤维与PAS之间的应力传递,进一步提高复合材料的力学性能。当AMEO加入量为400、800、1 200、1 600μL/gCNTs,复合材料的拉伸强度分别为352、381、403、390 MPa,弯曲强度分别为380、414、443、478 MPa。由此得出,CNTs和AMEO协同作用明显提高复合材料的力学性能。     

Ab Initio Calculation of BN Generation from Boron and Nitrogen Oxides

Boron Nitride (BN) is one of the products produced in the burning of boron‐containing propellant. A possible reaction mechanism for the reactions of boron and nitrogen oxides (NO, NO₂, N₂O) has been studied using the G2MP2 method. The BN product can be formed in the reactions of B(⁴P) with NO, NO₂ and N₂O. Among these three reactions, B(⁴P)+NO₂ and B(⁴P)+N₂O are 181.42 kJ/mol and 160.92 kJ/mol more‐exothermic than the B(⁴P)+NO reaction. The barrier heights from intermediates to transition states are 64.85 kJ/mol and 111.75 kJ/mol for B(⁴P)+NO₂ and B(⁴P)+N₂O, respectively. However, in the reaction B(⁴P)+NO , the transition from intermediate to product (IM3→BN+O) is very endothermic by 420.70 kJ/mol. So B(⁴P)+ N₂O→BN+NO and B(⁴P)+NO₂→BN+O₂ are more likely reactions to generate BN than B(⁴P)+NO→BN+O.     

On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

Carbon nanotubes (CNTs) were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.     

“直接电子传递”源自碳纳米管与杂质的协同作用

多壁碳纳米管被众多研究者视为生物燃料电池或酶传感器直接电子传递的根源。但新的实验证据表明,碳纳米管中的金属杂质起着至关重要的作用。葡萄糖氧化酶FAD氧化还原峰在碳纳米管中金属杂质被回流去除之后消失,重新添加金属杂质之后其氧化还原峰又再次出现。所以酶电极的直接电子传递是金属杂质和碳纳米管协同作用的结果。     

Biological Nitrogen Removal Using the Supernatant of Ozonized Sludge as Extra Carbon Source

A sludge ozonation process with lab-scale anaerobic/oxic (A/O) system was used to investigate the utilization of the ozonized sludge (OS) supernatant as extra carbon source for denitrification. The optimal ozone dose for the sludge ozonation was 0.2 gO₃/gSS. The concentrations of SCOD, BOD, NH₃-N and TN in the supernatant increased respectively at this ozone dose. In the meantime, the sludge was significantly reduced. The OS supernatant had negative effect on nitrification because of low pH and alkalinity. After alkalinity adjustment, the A/O with the OS supernatant as the extra carbon source achieved a nitrogen removal rate of 78%, which was very close to the control experiment using glucose (79%).     

Detoxification of Ciprofloxacin in an Anaerobic Bioprocess Supplemented with Magnetic Carbon Nanotubes: Contribution of Adsorption and Biodegradation Mechanisms

In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals in wastewaters. Common electron transfer limitations benefit from the acceleration of reactions through utilization of redox mediators (RM). This work explores the potential of carbon nanomaterials (CNM) as RM on the anaerobic removal of ciprofloxacin (CIP). Pristine and tailored carbon nanotubes (CNT) were first tested for chemical reduction of CIP, and pristine CNT was found as the best material, so it was further utilized in biological anaerobic assays with anaerobic granular sludge (GS). In addition, magnetic CNT were prepared and also tested in biological assays, as they are easier to be recovered and reused. In biological tests with CNM, approximately 99% CIP removal was achieved, and the reaction rates increased ≈1.5-fold relatively to the control without CNM. In these experiments, CIP adsorption onto GS and CNM was above 90%. Despite, after applying three successive cycles of CIP addition, the catalytic properties of magnetic CNT were maintained while adsorption decreased to 29 ± 3.2%, as the result of CNM overload by CIP. The results suggest the combined occurrence of different mechanisms for CIP removal: adsorption on GS and/or CNM, and biological reduction or oxidation, which can be accelerated by the presence of CNM. After biological treatment with CNM, toxicity towards Vibrio fischeri was evaluated, resulting in ≈ 46% detoxification of CIP solution, showing the advantages of combining biological treatment with CNM for CIP removal.