Functionalization of multi‐walled carbon nanotubes with pramipexole for immobilization of palladium nanoparticles and investigation of catalytic activity in the Sonogashira coupling reaction

Pramipexole drug was attached to the surface of multi‐walled carbon nanotubes (MWCNTs) by reaction of acylated carbon nanotubes with pramipexole for the first time. The modified MWCNTs were characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopies and CHNS analysis. The prepared pramipexole–MWCNTs were used for immobilization of palladium nanoparticles as a novel nanocatalyst. After characterization of the final nanocomposite, the pramipexole–MWCNTs/Pd was applied as a novel phosphine‐free recyclable heterogeneous catalyst for Sonogashira reactions. Interestingly, the novel catalyst could be recovered and recycled five times without any significant loss in activity.     

Modification and dispersion of multi-walled carbon nanotubes in water

In the present work, the decorated purified raw multi-walled carbon nanotubes (R-MWCNTs) were obtained by chemical modification (CM) by treatment with concentrated sulfuric acid and concentrated nitric acid mixture with a certain volume ratio of 1: 3. The R-MWCNTs and CM-MWCNTs samples were investigated by X-ray Diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FT-IR). The prepared MWCNTs were homogeneously dispersed in water using a commercial surfactant (Polyvinyl pyrrolidone, (PVP)) and ultra-sonication. The dispersion of MWCNTs was obtained by UV-Vis analysis. The results show that chemical modification purified MWCNTs and more effective functional groups were attached on the surface of MWCNTs. Meanwhile, R-MWCNTs and CM-MWCNTs were uniformly distributed in aqueous PVP solution and the dispersion of CM-MWCNTs in water was better.     

多壁碳纳米管负载Pt-Au电催化剂的微波合成及其催化氧还原性质

采用微波还原法合成了具有较小的纳米颗粒以及较高的分散程度的纳米Pt-Au复合多壁碳纳米管(Pt-Au/MWCNTs)电催化剂. 利用旋转圆盘电极(RDE)技术对Pt-Au/MWCNTs电催化剂在0.1 mol•L−1 HClO4溶液中的催化氧还原的动力学进行了研究. 结果表明, Pt和Au的质量比为1:2时, 表现出对氧气较好的催化还原活性.     

无电沉积法AuNPs-MWCNTs的制备及其对黄酮类化合物的电化学催化性能研究

利用多壁碳纳米管具有较低的还原电位,以多壁碳纳米管作为还原剂和负载基底,通过无电沉积法制备了负载纳米金粒子的碳纳米管催化剂。此种材料具有更多的活性位点,避免了纳米金粒子表面保护剂的存在造成其催化活性降低的缺陷,发现其对典型黄酮类化合物-芦丁和黄芩苷具有良好的电化学催化性能和较高的灵敏度,并将其应用于电化学分析检测黄酮类化合物。     

聚合酞菁铁/多壁碳纳米管复合材料的制备及氧还原催化性能

采用高效、 便捷的微波合成法制备了4种不同结构的聚合酞菁铁/多壁碳纳米管(Poly-FePc/MWCNTs)复合材料并进行了表征. 结果表明, 聚合酞菁铁均匀地包裹在多壁碳纳米管上. 利用线性扫描电位法(LSV)和电化学阻抗法(EIS)对材料的氧还原催化活性进行了研究, 发现FePPc/MWCNTs复合材料具有最好的氧还原催化活性. 采用X射线光电子能谱(XPS)和X射线吸收精细结构光谱(XAFS)研究了Poly-FePc/MWCNTs复合材料中酞菁铁结构变化与氧还原催化性能的相关性. 结果表明, FePPc/MWCNTs复合材料中Fe-N₄接近平面结构, 聚合酞菁铁能够更好地与MWCNTs产生协同作用, 从而加速氧还原过程中电子的转移, 提高氧还原活性.     

Preparation and characterization of MnO<Subscript>2</Subscript>/MWCNTs-modified graphite electrode and its catalysis for oxygen reduction reaction (ORR)

Manganese dioxides were prepared onto multi-walled carbon nanotubes (MWCNTs) by cyclic voltammetry (CV). The obtained manganese oxide-MWCNTs (MnO₂/MWCNTs) samples were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectrometry (FTIR) and thermogravimetry (TG), respectively. The MnO₂/MWCNTs-modified graphite electrode was utilized in the electrochemical oxygen reduction reaction (ORR) and the enhanced oxygen reduction peak current strongly suggested that MnO₂/MWCNTs has catalysis for ORR when compared to the pure MnO₂ or MWCNTs. The catalysis mechanism of MnO₂/MWCNTs for ORR was also-discussed.     

PDDA修饰的碳纳米管载铂电催化剂的合成及其在碱性条件下的氧气还原反应催化性能

采用长链聚合物聚二烯丙基二甲基氯化铵(PDDA)对多壁碳纳米管(MWCNTs)进行修饰,并将采用胶体法还原出的铂(Pt)纳米粒子通过静电作用担载于PDDA修饰的多壁碳纳米管上,从而制备出Pt/PDDA/MWCNTs复合电催化剂.透射电镜(TEM)与X射线衍射(XRD)测试结果表明, Pt纳米粒子均匀地分布在MWCNTs的表面,其平均粒径约为3.6 nm.热失重分析显示催化剂的实际负载量为36%(w).旋转圆盘电极测试结果表明, Pt/PDDA/MWCNTs催化剂对碱性条件下的氧气还原反应(ORR)具有优异的催化活性.与负载量为40%(w)的商业Pt/C催化剂相比, Pt/PDDA/MWCNTs催化剂的氧气还原反应的起始电位和半波电位均正移约30 mV,其质量比活性更大.动力学研究结果进一步证实Pt/PDDA/MWCNTs催化剂比负载量为40%(w)的商业Pt/C催化剂在碱性条件下对氧气还原反应具有更优异的催化活性.     

高利用率多壁碳纳米管负载金铂合金纳米粒子催化剂在碱性溶液中的甲醇电催化氧化性能研究

使用乙二醇还原法合成了一系列高利用率多壁碳纳米管负载的金铂双金属纳米粒子电催化剂,在碱性溶液中由循环伏安和计时电流法测试该AuPt催化剂对于甲醇氧化反应的电催化活性.透射电子显微镜、X射线衍射与X射线能谱观测催化剂形貌,表征催化剂结构.结果表明,金铂双金属纳米粒子均匀分散在碳纳米管上,催化剂具有良好甲醇电氧化性能.实验表明Au/Pt/MWCNTs比为10∶8∶32(bymass)时,该催化剂具有最高甲醇电氧化峰电流密度与最负起始氧化电位.     

Co@Pt–Ru core-shell nanoparticles supported on multiwalled carbon nanotube for methanol oxidation

A novel synthesis route concerning reduction of cobalt core onto the surface of multiwalled carbon nanotubes (MWCNTs) and then substitution of part of Co core with Pt–Ru precursor was developed to synthesize the core-shell Co@Pt–Ru/MWCNTs catalyst. In this synthesis route, sodium borohydride and hydrazine hydrate were employed to reduce cobalt step by step in order to control the size of cobalt and the growth speed of cobalt crystal. The novel core-shell Co@Pt–Ru/MWCNTs catalyst shows good electrocatalysis towards methanol oxidation.     

Fabrication and characterization of buckypaper-based nanostructured electrodes as a novel material for biofuel cell applications

The fabrication process of buckypapers (BPs) made from stable suspensions of as-received or functionalized multi-walled carbon nanotubes (MWCNTs) with high purity (97.5 wt%, Baytubes), their characterization and their utilization towards novel biofuel cell electrode applications are reported. The BPs can vary in thickness between 1 μm and 200 μm, are mechanically robust, flexible, stable in solvents, possess high meso-porosities as well as high apparent electrical conductivities of up to 2500 S m(-1). Potentiodynamic measurements of biocathodes based on bilirubin oxidase (BOD)-decorated BPs for the oxygen reduction reaction (ORR) in neutral media (phosphate buffer solution) containing glucose indicate that BP electrodes based on functionalized MWCNTs (fBPs) perform better than BP electrodes of as-received MWCNTs and have high potential as an effective electrode material in biofuel cells and biosensors.     

Functionalization of multi-walled carbon nanotubes with coumarin derivatives and their biological evaluation

We report the synthesis and the characterization of different multi-walled carbon nanotubes (MWCNTs) linked to natural molecules, 5,7-coumarins and/or oleic acid, obtained from purified pristine MWCNTs by a cascade of chemical functionalization. The activities of these modified MWCNTs were investigated in vitro on human umbilical vein endothelial cells (HUVECs) by evaluating their ability to influence cell viability and to induce cell apoptosis. Our data showed that pristine MWCNTs are markedly cytotoxic; conversely, the carboxylated carbon nanotubes, much more readily dispersed in aqueous solutions and CNT-Link, the key intermediate designed by us for the drug anchorage, are biocompatible at the tested concentrations (1 and 10 μg ml(-1)).     

Electrochemical production, characterization, and application of MWCNTs

The subject of this study is production of carbon nanotubes (CNTs) using an original procedure of reduction of lithium molten salts onto graphite cathode; their structural characterization and application as support material for electrocatalysts aimed for hydrogen evolution. As-produced CNTs were characterized by means of scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric and differential thermal analysis (DTA). SEM and TEM images have shown that nanotubes are mostly of curved shape with length of 1–20 μm and diameter of 20–40 nm. Raman peaks indicate that the crystallinity of produced nanotubes is rather low. The obtained results suggest that formed product contains up to 80 % multiwalled carbon nanotubes (MWCNTs), while the rest being non-reacted graphite and fullerenes. DTA curves show that combustion process of the nanotubes takes place in two stages, i.e., at 450 and 720 °C. At the lower temperature, combustion of MWCNTs occurs, while at higher one, fullerenes and non-reacted graphite particles burn. As-produced MWCNTs were used as electrocatalyst’s support materials and their performance was compared with that of traditional carbon support material Vulcan XC-72. MWNTs have shown almost twice higher real surface area, and electrocatalyst deposited on them showed better catalytic activity than corresponding one deposited on Vulcan XC-72.     

Insight into the Origin of the Positive Effects of Imidazolium Salt on Electrocatalytic Activity: Ionic Carbon Nanotubes as Metal‐Free Electrocatalysts for Oxygen Reduction Reaction

We report remarkable metal‐free electrocatalytic activities of the imidazolium salt‐functionalized ionic multi‐walled carbon nanotubes (IM‐f‐MWCNTs) in the oxygen reduction reaction (ORR). The electrocatalytic activity can be attributed to the induced polarization of the π‐electrons of CNTs, thus accelerating interfacial electron transfer. The zwitterionic MWCNTs functionalized with poly(vinylimidazolium sulfonate) have a more positive surface charge and exhibit a better electrocatalytic activity than the poly(vinylbutylimidazolium chloride)‐functionalized MWCNTs. The IM‐f‐MWCNTs showed better fuel selectivity than the commercial Pt/C electrocatalyst.     

Cyclic voltammetric investigation of Eu<Superscript>3+</Superscript> on a MWCNTs/SDS-modified glassy carbon (GC) electrode

Electrochemical reduction behavior of Eu³⁺ on a multi-walled carbon nanotubes (MWCNTs)/sodium lauryl sulfate (SDS) (MWCNTs/SDS)-modified glassy carbon (GC) electrode was investigated by cyclic voltammetry (CV). Results indicated that the electrochemical reduction process of Eu³⁺ at the MWCNTs/SDS-modified GC electrode is a quasi-reversible and diffusion-controlled process. The value of standard rate constant (k _s) at the MWCNTs/SDS-modified GC electrode was estimated to 1.96 × 10⁻² cm s⁻¹. CV studies showed that the electrochemical response of Eu³⁺ was directly related to the ratio of MWCNTs to SDS, and the tube diameter of MWCNTs had a slight influence on the electrochemical behavior of Eu³⁺, whereas the tube length. of MWCNTs had a strong influence. CVs results also proved that s-MWCNTs (with shorter tube length)-modified GC electrode showed better response to the electrochemical reaction of Eu³⁺.     

Direct electrochemistry and electrochemical catalysis of myoglobin-TiO2 coated multiwalled carbon nanotubes modified electrode

TiO(2) nanoparticles were homogeneously coated on multiwalled carbon nanotubes (MWCNTs) by hydrothermal deposition, and this nanocomposite might be a promising material for myoglobin (Mb) immobilization in view of its high biocompatibility and large surface. The glassy carbon (GC) electrode modified with Mb-TiO(2)/MWCNTs films exhibited a pair of well-defined, stable and nearly reversible cycle voltammetric peaks. The formal potential of Mb in TiO(2)/MWCNTs film was linearly varied in the range of pH 3-10 with a slope of 48.65 mV/pH, indicating that the electron transfer was accompanied by single proton transportation. The electron transfer between Mb and electrode surface, k(s) of 3.08 s(-1), was greatly facilitated in the TiO(2)/MWCNTs film. The electrocatalytic reductions of hydrogen peroxide were also studied, and the apparent Michaelis-Menten constant is calculated to be 83.10 microM, which shows a large catalytic activity of Mb in the TiO(2)/MWCNTs film to H(2)O(2). The modified GC electrode shows good analytical performance for amperometric determination of hydrogen peroxide. The resultant Mb-TiO(2)/MWCNTs modified glassy carbon electrode exhibited fast amperometric response to hydrogen peroxide reduction, long term life and excellent stability. Finally the activity of the sensor for nitric oxide reduction was also investigated.     

Performance of dye-sensitized solar cells with various carbon nanotube counter electrodes

Double-wall carbon nanotubes (DWCNTs), single-wall carbon nanotubes (SWCNTs), and multi-wall carbon nanotubes (MWCNTs) were investigated as an alternative for platinum in counter-electrodes for dye-sensitized solar cells. The counter-electrodes were prepared on fluorine-doped tin oxide glass substrates by the screen printing technique from pastes of carbon nanotubes and organic binder. The solar cells were assembled from carbon nanotubes counter-electrodes and screen printed anodes made from titanium dioxide. The cells produced with DWCNTs, SWCNTs or MWCNTs have overall conversion efficiencies of 8.0%, 7.6% and 7.1%, respectively. Electrochemical impedance spectroscopy measurements revealed that DWCNTs displayed the highest catalytic activity for the reduction of tri-iodide ions. The large surface area and superior chemical stability of the DWCNTs facilitated the electron-transfer kinetics at the interface between counter-electrode and electrolyte and yielded the lowest transfer resistance, thereby improving the photovoltaic activity. A short-term stability test at moderate conditions confirmed the robustness of solar cells based on the use of DWCNTs, SWCNTs or MWCNTs.

Mb/AuNPs/MWCNTs/GC电极对H2O2电催化性能的研究

采用还原法制备了AuNPs/MWCNTs复合材料,并构建了氧化还原蛋白质的固定化和生物传感界面AuNPs/MWCNTs/GC电极.以肌红蛋白(Myoglobin,Mb)为例,研究了固定化蛋白质在AuNPs/MWCNTs/GC电极上的直接电化学.结果表明,AuNPs/MWCNTs复合材料不仅能有效地促进Mb与电极表面的直接电子转移,而且能很好地保持固定化Mb的生物催化活性.Mb/AuNPs/MWCNTs/GC电极对H2O2具有良好的电催化还原性能,其线性响应范围为1～138μmol·L-1,检测限为0.32μmol·L-1(S/N=3),并具有较低的米氏常数(0.143 mmol·L-1).该电极操作简单,响应迅速,稳定性和重现性好,有望用于蛋白质的固定化及第三代生物传感器的制备.     

Matrix‐grafted multiwalled carbon nanotubes/poly(methyl methacrylate) nanocomposites synthesized by in situ RAFT polymerization: A kinetic study

A new approach was developed to functionalize multiwalled carbon nanotubes (MWCNTs) with a polymerizable methyl methacrylate (MMA) groups, and the structure of functionalized MWCNTs were characterized by FTIR, Raman, XPS, and TEM. Using the strategy of “grafting through,” poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of MWCNTs during the in situ synthesis of MWCNT/PMMA nanocomposites over reversible addition‐fragmentation chain transfer (RAFT) polymerization. Kinetics of RAFT‐mediated polymerization of MMA in the presence of MMA‐grafted MWCNTs was studied by using gas chromatography and gel permeation chromatography. To further study, attached polymers were detached and their molecular characteristics were compared to freely formed chains. Results of kinetic studies showed that the utilized commercial chain transfer agent strictly reduced the rate of polymerization as well as relatively controlled molecular weights and narrow molecular weight distributions of free chains. MWCNTs showed a radical activity, retarding the polymerization and reducing the rate of reaction. The effect of MWCNTs concentrations on molecular weights and polydispersity indexes (PDI) was different at the surface and in the bulk. The molecular weights of free chains increased, and the PDI was decreased with increasing MWCNTs. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 555–569, 2012     

室温下镀钯多壁碳纳米管对苯的气敏响应特性

在酸氧化后的多壁碳纳米管上化学还原镀钯,用水将镀钯后的碳管清洗至中性并配制成悬浊液,将悬浊液旋涂在真空溅射的叉指金电极表面,干燥后作为气敏膜,把气敏膜暴露于一定浓度的苯气体中,检测传感器的电流变化,并计算其灵敏度。镀钯后的多壁碳管在室温下对苯响应和回复迅速,电导变化与苯气体的浓度呈良好的线性关系,其线性回归方程y=0.0041x 0.1288,r=0.9546。Pd颗粒对苯分子和碳管壁结构缺陷间的电子转移的促进作用可能是多壁碳管镀钯后产生良好气敏响应的原因。     

Advantages of immobilization of Pt nanoparticles protected by dendrimers on multiwalled carbon nanotubes

Pt nanoparticles (PtNPs) were synthesized in the presence of a NH(2)-terminated fourth generation poly(amido amine) (PAMAM) dendrimer as a stabilizer at different molar ratios (M:D) of metal precursor to amine terminal group of dendrimer. Subsequently, PtNPs protected by dendrimers (DENPtNPs) were covalently immobilized on multiwalled carbon nanotubes (MWCNTs) by using a condensing agent for amide bond formation between acid-treated MWCNTs and DENPtNPs and the product CNT/DENPtNPs were characterized. PtNPs on MWCNTs increased quantitatively in content with M:D and dispersed with same aspect as the dispersion of DENPtNPs in water: PtNPs homogeneously dispersed at low M:D ratio and slightly aggregated at high ratio. The decomposition of CNT/DENPtNPs occurred at the lower temperature owing to the catalytic effect of PtNPs. A near-infrared absorption band around 2083 nm, which is extremely weak for MWCNTs, was intensified and D, D' and G Raman bands were slightly downshifted when DENPtNPs were attached. These phenomena can be attributed to the electron transfer from DENPtNPs to MWCNTs. Remarkable advantage is apparent from the enhanced electrochemical behavior of CNT/DENPtNPs loaded on gold electrode. PtNPs promoted the electron transfer of MWCNTs and dendrimers contributed to uptake of redox materials.