Transition-metal-catalyzed unzipping of single-walled carbon nanotubes into narrow graphene nanoribbons at low temperature

Open, sesame! Graphene nanoribbons (GNRs) with smooth edges and controllable widths are crucial for graphene electronic and spintronic applications. High-quality narrow GNRs can be synthesized from single-walled carbon nanotubes at 200-300?°C using a Cu-atom catalyst, which dramatically reduces the energy barrier of unzipping from 3.11 to 1.16?eV.     

Electrochemical chlorine sensor with multi-walled carbon nanotubes as electrocatalysts

It has been reported for the first time that an electrochemical gas sensor modified with multi-walled carbon nanotubes (MWNTs) film as electrocatalyst was fabricated for the determination of chlorine (Cl₂).Here, MWNTs and graphite were compared with each other in terms of their electrochemical properties using cyclic voltammetry. Cl₂ gas was allowed through the cathode surface of the sensor and the resulting galvanic effects were monitored. Results indicated that both of the MWNTs and graphite have the electrocatalytic activity for the reduction of Cl₂ while the MWNTs-modified electrode exhibited a higher accessible surface area in electrochemical reactions, excellent sensitivity, stable response, reproducibility and recovery for the determination of Cl₂.     

In situ electrochemical organization of CdSe nanoclusters on graphene during unzipping of carbon nanotubes

In situ decoration of very small CdSe quantum dots on graphene nanoribbons (GNRs) has been achieved during the electrochemical unzipping of single walled carbon nanotubes. Critical parameters like the width of the GNRs, size distribution of quantum dots and their organization on GNRs have been shown to be strongly dependent on the electric field and time.     

Electrochemical synthesis of gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode and their application

Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed.     

Curvature effect in the longitudinal unzipping carbon nanotubes

Density functional theory (DFT) calculations are performed to analyze curvature effects in the oxidative longitudinal unzipping of carbon nanotubes (CNTs) of different diameters. The reactions considered involve the adsorption of permanganate, followed by the oxidation of the nanotube, which results in dione and hole formation. The study was performed with armchair CNTs of different diameters and with corrugated graphene layers, which emulate the curvature of CNT of larger radii, with the finding that the curvature and the pyramidalization angle of the these structures strongly affects the stability of the intermediate dione structure formed during the unzipping process. Permanganate adsorption energies increase for more curved surfaces promoting the oxidation reaction in surfaces of small radius, making this reaction spontaneous for small radius. The second permanganate adsorbs on the parallel carbon–carbon bond to first diona formation resulting the longitudinal unzipping of the CNT.     

One-step water-assisted synthesis of high-quality carbon nanotubes directly from graphite

At 1 atm pressure, high-quality multiwall carbon nanotubes were synthesized directly from graphite in the absence of catalyst by a one-step water-assisted method.     

Toxicity of graphene oxide and multi-walled carbon nanotubes against human cells and zebrafish

Graphene possesses unique physical and chemical properties, which have inspired a wide range of potential biomedical applications. However, little is known about the adverse effects of graphene on the human body and ecological environment. The purpose of our work is to make assessment on the toxicity of graphene oxide (GO) against human cell line (human bone marrow neuroblastoma cell line and human epithelial carcinoma cell line) and zebrafish (Danio rerio) by comparing the toxic effects of GO with its sister, multi-walled carbon nanotubes (MWNTs). The results show that GO has a moderate toxicity to organisms since it can induce minor (about 20%) cell growth inhibition and slight hatching delay of zebrafish embryos at a dosage of 50 mg/L, but did not result in significant increase of apoptosis in embryo, while MWNTs exhibit acute toxicity leading to a strong inhibition of cell proliferation and serious morphological defects in developing embryos even at relatively low concentration of 25 mg/L. The distinctive toxicity of GO and MWNTs should be ascribed to the different models of interaction between nanomaterials and organisms, which arises from the different geometric structures of nanomaterials. Collectively, our work suggests that GO does actual toxicity to organisms posing potential environmental risks and the result is also shedding light on the geometrical structure-dependent toxicity of graphitic nanomaterials.     

Polystyrene grafted multi-walled carbon nanotubes

Oxidised, multi-walled, carbon nanotubes can be grafted with polystyrene molecules using an situ radical polymerisation reaction, thereby dramatically modifying their solubility and their suitability for nanocomposite applications.     

Electrochemical preparation of luminescent graphene quantum dots from multiwalled carbon nanotubes

Green luminescent, graphene quantum dots (GQDs) with a uniform size of 3, 5, and 8.2(±0.3)?nm in diameter were prepared electrochemically from MWCNTs in propylene carbonate by using LiClO(4) at 90?°C, whereas similar particles of 23(±2)?nm were obtained at 30?°C under identical conditions. Both these sets of GQDs displayed a remarkable quantum efficiency of 6.3 and 5.1?%, respectively. This method offers a novel strategy to synthesise size-tunable GQDs as evidenced by multiple characterisation techniques like transmission and scanning electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction (XRD). Photoluminescence of these GQDs can be tailored by size variation through a systematic change in key process parameters, like diameter of carbon nanotube, electric field, concentration of supporting electrolyte and temperature. GQDs are promising candidates for a variety of applications, such as biomarkers, nanoelectronic devices and chemosensors due to their unique features, like high photostability, biocompatibility, nontoxicity and tunable solubility in water.     

Asymmetric end-functionalization of multi-walled carbon nanotubes

Asymmetric end-functionalization of carbon nanotubes was achieved by sequentially floating a substrate-free aligned carbon nanotube film on two different photoreactive solutions with only one side of the nanotube film being contacted with the photoreactive solution and exposed to UV light each time. The resultant nanotubes with different chemical reagents attached onto their opposite tube-ends should be very useful for site-selective self-assembling of carbon nanotubes into many novel functional structures for various potential applications.     

Electrochemical properties and the determination of nicotine at a multi-walled carbon nanotubes modified glassy carbon electrode

Electrochemical properties of nicotine at the glassy carbon electrode modified with multi-walled carbon nanotubes were explored. Nicotine underwent irreversible reduction at the modified electrode, which was an adsorption-controlled process with two protons and two electrons. The reductive peak current of nicotine significantly increased at the modified electrode compared with the bare glassy carbon electrode, suggesting that the multi-walled carbon nanotubes can enhance the electron transfer rate. The current was proportional to the concentration of nicotine over two line ranges, and the detection limit was 9.3 µM (at S/N?=?3). For ten parallel detections of 0.62 mM nicotine, the relative standard deviation was 2.67%, suggesting that the film modified electrode had excellent reproducibility. The modified electrode was applied to the direct determination of nicotine in tobacco samples with good sensitivity, selectivity and stability.     

Electrochemical characteristics of the immobilization of calf thymus DNA molecules on multi-walled carbon nanotubes

Immobilization of DNA on carbon nanotubes plays an important role in the development of new types of miniature DNA biosensors. Electrochemical characteristics of the immobilization of calf thymus DNA molecules on the surfaces of multi-walled carbon nanotubes (MWNTs) have been investigated by cyclic voltammetry and electrochemical impedance analysis. The peak currents for Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox couple observed in the cyclic voltammograms decrease and the electron-transfer resistance (R(et)) obtained from the Nyquist plots increase due to the immobilization of DNA molecules (dsDNA or ssDNA) on the surfaces of MWNTs. Most of calf thymus DNA are covalently immobilized on MWNTs via diimide-activated amidation between the carboxylic acid groups on the carbon nanotubes and the amino groups on DNA bases, though the direct adsorption of the DNA molecules on MWNTs can be observed. Additionally, the interaction between DNA molecules immobilized on MWNTs and small biomolecules (ethidium bromide) can be observed obviously by cyclic voltammetry and electrochemical impedance analysis. This implies that the DNA molecules immobilized at the surface of MWNTs, with little structure change, still has the ability to interact with small biomolecules.     

Cover picture: transition-metal-catalyzed unzipping of single-walled carbon nanotubes into narrow graphene nanoribbons at low temperature (angew. Chem. Int. Ed. 35/2011)

Narrow, smooth-edged graphene nanoribbons are needed for graphene electronics to replace the current silicon technology. In their Communication on page?8041?ff., J. Wang, F. Ding, et?al. report a smart strategy for cutting single-walled carbon nanotubes (gray) into narrow graphene nanoribbons in H(2) gas (green) with a single transition-metal atom (Cu, red) as the chemical scissors.     

盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电化学行为

运用循环伏安法、线性扫描伏安法、计时电量法等研究了盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电化学行为。实验表明:盐酸左氧氟沙星在聚L-精氨酸/多壁碳纳米管修饰电极上的电极反应过程为等电子等质子吸附控制的不可逆过程,在pH=6.0的Na2HPO4-NaH2PO4支持电解质中,其氧化峰电流与浓度在7.0×10-6~1.0×10-4mol·L-1范围内呈良好的线性关系,相关系数R为-0.9992,检出限为5.0×10-6mol·L-1,样品测定回收率为98.26%~101.70%。     

Electrochemical oxidation of sulfur-containing amino acids on an electrode modified with multi-walled carbon nanotubes

MWNT-modified electrodes are introduced for the voltammetric determination of sulfur-containing amino acids. The morphology of the electrode surface has been characterized by atomic force microscopy. The MWNT layer consists of deeply intertwined vermicular structures with the average diameter of 25 nm. Cysteine, glutathione and methionine are oxidized on the electrode while only cysteine gives signals on the glassy carbon (GC) electrode. The application of such electrodes leads to a decreased overpotential and increase of oxidation currents for cysteine in comparison with a bare GC electrode. The schemes of oxidation are proposed. A decrease of the lower limit of determination and an enlargement of the analytical range for antioxidants were obtained. A simple, fast and accurate procedure for the voltammetric determination of methionine in pharmaceuticals has been developed and can be recommended for quality control purposes.     

A facile approach to synthesize poly(4-vinylpyridine)/multi-walled carbon nanotubes nanocomposites: highly water-dispersible carbon nanotubes decorated with gold nanoparticles

A facile approach to attach high-density and uniform gold nanoparticles on individual multi-walled carbon nanotubes (MWNTs) is achieved. By simple grinding, water-soluble linear polymers poly(4-vinylpyridine) (PVP)-wrapped around nanotubes and thus rendered them reversibly soluble in water, ethanol, and DMF. Individual tubes are clearly observed after PVP-wrapped nanotubes were spin-coated onto a silicon wafer. Subsequently, Au nanoparticles were densely decorated on the individual MWNTs by in situ reduction of HAuCl₄ in the homogeneous aqueous solution of MWNTs–PVP to form stable water-dispersible Au/PVP/MWNTs hybrid. Morphology of Au nanoparticles was determined by scanning electron microscope and atomic force microscope. The diameter of the Au nanoparticles is controlled in the range of 3.5 to 13.5 nm. The presence of gold nanoparticles with decreased particle size was also detected by UV–Vis spectroscopy.     

Ligand-modified multi-walled carbon nanotubes for potentiometric detection of silver

Three novel hybrid materials have been synthesized by ligands: N-(2-vinylsulfanyl-ethylidene)-benzene-1,2-dimine (SBD), N-pyridin-2-ylmethylene-benzene-1,2-dimine (NBD) and N-furan-2-ylmethylene-benzene-1,2-dimine (OBD), covalently linking to multi-walled carbon nanotubes (MWCNTs). These MWCNT hybrid materials were used both as ionophores and as ion-to-electron transducers to construct Ag(+) carbon paste electrodes. The resulting electrodes show higher selectivity to Ag(+) than other cations tested. Among the three electrodes, the electrode based on SBD-g-MWCNTs with optimum composition shows the best performance to Ag(+). It exhibits an excellent Nernstian response to Ag(+) in the concentration range from 8.8 × 10(-8) to 1.0 × 10(-1) M with a detection limit of 6.3 × 10(-8) M, and it can also be used over a wide pH range of 3.0-8.0 with a quick response time of 5 s. The response mechanism of the proposed electrode was also investigated by using AC impedance and UV-vis spectroscopy techniques.     

Oxidation of dopamine on multi-walled carbon nanotubes

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of the chemical vapor deposition technique with decomposition of either acetonitrile (ACN) or benzene (BZ) in the presence of ferrocene (FeCp₂) which served as catalyst. The electrochemical response of the two different kinds of MWCNT-based films, further referred to as MWCNT-ACN and MWCNT-BZ, towards the oxidation of dopamine (DA) to dopamine-o-quinone (DAQ) was tested by means of cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Both MWCNT-based films exhibit quasi-reversible response towards DA/DAQ with some slight kinetic differences; specifically, the charge-transfer process was found to be faster on MWCNT-ACN (k _s?=?35.3?×?10^?3 cm s^?1) compared to MWCNT-BZ (k _s?=?6.55?×?10^?3 cm s^?1). The detection limit of MWCNT-BZ for DA (0.30 μM) appears to be poorer compared to that of MWCNT-ACN (0.03 μM), but nevertheless, both MWCNT-based films exhibit greater detection ability compared to other electrodes reported in the literature. The sensitivities of MWCNT-ACN and MWCNT-BZ towards DA/DAQ were determined as 0.65 and 0.22?A M^?1 cm^?2, respectively. The findings suggest that the fabricated MWCNT-based electrodes can be successfully applied for the detection of molecules with biological interest.