Carbon Nanotube Hybrid Materials Research Articles

RETRACTED ARTICLE: Application of Polypropylene Amine Dendrimers (POPAM)-Grafted MWCNTs Hybrid Materials as a New Sorbent for Solid-Phase Extraction and Trace Determination of Gold(III) and Palladium(II) in Food and Environmental Samples

A new method which utilizes a polypropylene amine dendrimers (POPAM)-grafted multi-walled carbon nanotubes (MWCNTs) hybrid materials as an effective sorbent in solid-phase extraction has been developed for separation and preconcentration of Au(III) and Pd(II) trace levels in food, water and soil samples. The optimum experimental conditions such as pH, flow rates, type, concentration, and volume of the eluent for elution of gold and palladium ions, breakthrough volume, and effect of potentially interfering ions on separation and determination of these noble metals were investigated. The extraction recoveries for the mentioned noble metals were greater than 98 % and the limits of detection were 0.08 and 0.12 ng mL−1 for gold and palladium, respectively. The relative standard deviations of the method were less than 4 % for eight separate column experiments for determination of 5.0 μg of gold and palladium ions. The adsorption capacity of the modified MWCNT was 92 mg g−1 for gold and 74 mg g−1 for palladium on POPAM-grafted MWCNTs. Validation of the suggested method was performed by analyzing certified reference materials. Finally, the proposed method was applied for determination of gold(III) and palladium(II) in real samples, including fish, shrimp, water, and soil.

RETRACTED ARTICLE: PdAu Alloy Nanoparticles Encapsulated by PPI-g-MWCNTs as a Novel Catalyst for Chemoselective Hydrogenation of Alkenes Under Mild Conditions

The synthesis, characterization and catalytic applications of bimetallic PdAu encapsulated on polypro- pylene imine grafted multi-wall carbon nanotubes hybrid materials have been reported. The results show that the catalyst induces a highly activity and chemoselective hydrogenation of less hindered alkenes to the correspond- ing alkanes using hydrogen gas in environmentally friendly solvents H2O/EtOH at 50 C with high yields. The char- acterization of catalyst was confirmed by FT-IR, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction.

Facile scalable synthesis of Co3O4/carbon nanotube hybrids as superior anode materials for lithium-ion batteries

In this report, Co3O4/multiple-wall carbon nanotube (MWCNT) hybrid materials were synthesized via strong ultrasonication-assisted shaking and magnetic stirring processes. The prepared samples were well characterized by utilizing powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy techniques. Results indicated that the resulting Co3O4 nanoparticles were highly dispersed in the MWCNT network backbone and further form Co3O4/MWCNT hybrid materials. The obtained Co3O4/MWCNT hybrids can be employed as anode electrode in Lithium-ion batteries and deliver as high as discharge capacity of 1250mAhg−1 at a current density of 0.2C, additionally, 81% of the discharge capacity for sample 2 with 20wt.% MWCNT loading could be retained after 70 cycles, which could be associated with the specific hybrid structure of the electrode as well as the addition of MWCNT. Most importantly, the present synthetic approach is facile, controllable, and scalable, which allowing it more easily adapted to prepare other hybrid materials with specific architectures.

Fabrication and supercapacitive properties of a thick electrode of carbon nanotube–RuO2 core–shell hybrid material with a high RuO2 loading

A core-shell hybrid material of amorphous hydrous RuO2-coated carbon nanotubes (CNT–RuO2) with a RuO2 loading as high as 82.4wt% was prepared by a solution method using RuCl3 and NaHCO3 aqueous solutions. The effect of preparation conditions, especially the dripping speed of the NaHCO3 solution, on the formation of the core-shell structure was investigated, and the corresponding mechanism was discussed. Supercapacitive properties of the CNT–RuO2 and amorphous hydrous RuO2 electrodes with a thickness of over 200μm were studied and the crucial factors to govern their rate capability were analyzed. For the thick CNT–RuO2 electrode, a comparison of its specific capacitance before and after subtracting the effect of the voltage drop of discharge curves caused by the inner resistance of the CNT–RuO2 symmetrical supercapacitor indicates that electronic conductivity is more important than proton diffusion in determining its rate capability.

Plasma synthesis of Pd nanoparticles decorated-carbon nanotubes and its application in Suzuki reaction

The synthesis of palladium nanoparticles-functionalized multi-walled carbon nanotubes (Pd-MWNTs) hybrid materials has been realized by a gas–liquid interfacial plasma performed in ionic liquid ([bmim]BF4) mediate. High-density Pd nanoparticles with size below 7nm are found to uniformly deposit on the surface of MWNTs with high loading ratio up to 33wt.% by plasma method. The synthesized hybrid materials were systematically examined by Fourier transform infrared spectroscopy, transmission electron microscopy combined with energy dispersive X-ray spectroscope and selected-area electron diffraction, X-ray photoelectron spectroscopy, X-ray diffraction, and inductive coupled plasma spectroscopy. Importantly, the synthesized Pd-MWNTs are found to exhibit a high catalytic activity, and serve as good recyclability catalyst in Suzuki reaction.

Assembling fabrication and capacitance of manganese oxide nanosheets and functionalized carbon nanotubes hybrid material

The manganese oxide nanosheets (MnO2) with negative charge and the functionalized carbon nanotubes (CNTs) with positive charge are selected as assembling blocks, and the manganese oxide nanosheets and functionalized carbon nanotubes hybrid material (CNTs–MnO2 hybrid material) is fabricated by an assembling flocculation method. The restacking process of the manganese oxide nanosheets is effectively prevented due to the existence of CNTs, and manganese oxide nanosheets exist in nearly exfoliation state in CNTs–MnO2 hybrid material. The morphology and structure of the obtained materials are investigated by FTIR, XRD, SEM and TEM. A unique flaky appearance is observed for hybrid material. The capacitance of the CNTs–MnO2 hybrid material is investigated by cyclic voltammetry (CV) and Nyquist plots. A strong synergistic effect between the functionalized CNTs and exfoliated MnO2 is observed. The doped CNTs not only increase the utilization of manganese oxide nanosheets in the active cathode material, but also improve its performance at the high rate charge and discharge. The capacitance of CNTs–MnO2 hybrid material electrode is about 285Fg−1 at 5mVs−1. A relative high specific capacitance of 151Fg−1 can be maintained even at 100mVs−1.

Facile Synthesis of Cubic Spinel Cobalt Oxide/Multi-Walled Carbon Nanotube Hybrid Material as a Bifunctional Electrocatalyst for Metal-Air Batteries

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Thermostability, Photoluminescence, and Electrical Properties of Reduced Graphene Oxide–Carbon Nanotube Hybrid Materials

Reduced graphene oxide–carbon nanotube (RGO–CNT) hybrid materials were prepared by a simple catalyst-free route. The thermostability, photoluminescence (PL) and electrical properties of RGO–CNTs were investigated systematically. The results revealed that compared to RGO, RGO–CNTs showed multicolor PL, and higher thermostability and conductivity. The RGO–CNTs therefore have important potential applications in the fields of photonic and electrical devices.

Unzipped multiwalled carbon nanotubes-incorporated poly(vinylidene fluoride) nanocomposites with enhanced interface and piezoelectric β phase

An improved method is described for the fabrication of poly(vinylidene fluoride) (PVDF)/carbon nanotubes (CNTs) hybrid materials to solve intrinsic limitation of CNTs. In this study, multiwalled carbon nanotubes (MWCNTs) were unzipped by an oxidative unzipping process before dispersing in PVDF matrix, and unzipped MWCNTs (μCNTs) with different unzipping degrees were obtained through controlling the amounts of oxidant (KMnO4). Due to the increased available interface area and specific interaction between the oxygen-containing groups (such as >CO) in μCNTs and the >CF2 group of PVDF, the dispersion of μCNTs in PVDF matrix is tremendously improved. The resulting PVDF/μCNTs nanocomposites were characterized by wide angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It is found that μCNTs nucleate PVDF crystallization and enhance piezoelectric β phase with a concomitant decrease of α phase. This is particularly true for the nanocomposites including the μCNTs with higher unzipping degree, in which the mass crystallinity and content of β phase (Fβ) were enhanced, implied by the increased piezoelectric constant d33. In addition, the increased storage modulus (E′) tested by dynamic mechanical analysis confirmed that μCNTs were more effective than pristine MWNTs in terms of reinforcing polymers.

Catalyst-free synthesis of reduced graphene oxide–carbon nanotube hybrid materials by acetylene-assisted annealing graphene oxide

A facile catalyst-free approach for synthesis of reduced graphene oxide-carbon nanotube (RGO-CNT) hybrid materials was presented by acetylene-assisted annealing graphene oxide. The weight ratio of CNTs to RGO can be adjusted by regulating the annealing temperature, and it can be tuned in a relatively wide range of 0.33 to 7.039. The catalyst-free method opens up the possibility for the synthesis of RGO-CNTs for various applications.

Direct electrochemistry of glucose oxidase at electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid material modified electrode for glucose biosensor

Direct electrochemistry of glucose oxidase (GOx) at an electrochemically reduced graphene oxide–multiwalled carbon nanotubes hybrid (ERGO–MWCNT) modified glassy carbon electrode (GCE) has been reported. The π–π stacking interaction operating between the MWCNT and graphene oxide (GO) has been revealed by UV–Vis absorption spectroscopy. GOx was well immobilized onto the ERGO–MWCNT hybrid film, as a result direct electrochemistry of GOx has been achieved. Compared with pristine MWCNT, 2.1 fold higher peak current and very low peak to peak separation (ΔEp) of 26mV were observed at the hybrid film, demonstrating faster electron transfer between GOx and the modified electrode surface. Moreover, the modified film exhibited high electrocatalytic activity towards glucose via reductive detection of oxygen consumption and in the presence of mediator. The proposed biosensor exhibits low detection limit of 4.7μM with wide linear range of 0.01–6.5mM and acquires excellent storage and operational stabilities. The accurate glucose determination in human blood serum and good recoveries achieved in spiked urine samples revealed their great potential in the practical applications.

Solvothermal in situ synthesis of Fe3O4-multi-walled carbon nanotubes with enhanced heterogeneous Fenton-like activity

Fe3O4-multi-walled carbon nanotubes (Fe3O4-MWCNTs) hybrid materials were synthesized by a solvothermal process using acid treated MWCNTs and iron acetylacetonate in a mixed solution of ethylene glycol and ultrapure water. The materials were characterized using X-ray powder diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. The results showed that a small amount of water in the synthesis system played a role in controlling crystal phase formation, size of Fe3O4, and the homogeneous distribution of the Fe3O4 nanoparticles deposited on the MWCNTs. The Fe3O4 nanoparticles had diameters in the range of 4.2–10.0nm. They displayed good superparamagnetism at room temperature and their magnetization was influenced by the reaction conditions. They were used as a Fenton-like catalyst to decompose Acid Orange II and displayed a higher activity than nanometer-size Fe3O4.

Enhanced Catalytic Activity for Methanol Electro‐oxidation of Uniformly Dispersed Nickel Oxide Nanoparticles—Carbon Nanotube Hybrid Materials

Highy crystalline NiO nanoparticles are uniformly grown on the walls of carbon nanotubes (CNTs) by atomic layer deposition (ALD) at moderate temperature.Their size and stoichiometry are controlled by the ALD process parameters. The obtained NiO/CNT hybrids exhibit excellent performance in the electro-oxidation of methanol.

Functionalization of nitrogen-doped carbon nanotubes with gallium to form Ga-CNx-multi-wall carbon nanotube hybrid materials

In an effort to combine group III–V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI3), it was possible to form covalent bonds between the Ga3+ ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride–carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy

In situ synthesis of graphene/single-walled carbon nanotube hybrid material by arc-discharge and its application in supercapacitors

Aiming to the synthesis of graphene/single-walled carbon nanotube (SWNT) hybrid materials, an arcing-discharge method for an efficient and large-scale production has been developed. Furthermore, the performance of supercapacitors using this graphene/SWNT hybrid has been studied, which gives a remarkable result with the specific capacitance of ∼350F/g at 2.7V and an energy density of ∼68Wh/kg in the standard industry organic electrolyte system.

Chemical-free synthesis of graphene–carbon nanotube hybrid materials for reversible lithium storage in lithium-ion batteries

Graphene–carbon nanotube hybrid materials were successfully prepared through the π–π interaction without using any chemical reagent. We found that the ratio between carbon nanotube and graphene had critical influences on the state in aqueous solution and morphology of hybrid materials. Field emission scanning electron microscope and transmission electron microscope analysis confirmed that graphene nanosheets wrap around individual carbon nanotubes and form a homogeneous three-dimensional hybrid nanostructure. When applied as an anode material in lithium ion batteries, graphene–carbon nanotube hybrid materials demonstrated a high reversible lithium storage capacity, a high Coulombic efficiency and an excellent cyclability.

Microwave-induced fabrication of copper nanoparticle/carbon nanotubes hybrid material

Copper nanoparticle/multi-walled carbon nanotube (MWCNT) hybrid material could be fabricated by microwave irradiation to a suspension of MWCNTs dispersed in copper precursor with the presence of ethylene glycol. Microscopic and spectroscopic analyses could confirm the uniform dispersion of copper oxide nanoparticles hybridized on the outer surface of MWCNTs. Reduction of Cu2+ ions to Cu2O and Cu nanoparticles was ascribed to functional groups which were generated after the precursor was irradiated by microwave. Sufficient irradiation time of 5 min or longer played an important role to induce the agglomeration of copper oxide nanoparticles on the MWCNT surface.

Electrocatalytic oxidation of oxalic acid on palladium nanoparticles encapsulated on polyamidoamine dendrimer-grafted multi-walled carbon nanotubes hybrid material

In this work, a heterogeneous catalyst based on palladium nanoparticles encapsulated on polyamidoamine dendrimer-grafted multi-walled carbon nanotubes (PdNPs/PAMAM–MWCNTs) hybrid material was used as an electrode modifier. The catalyst was dissolved in N,N-Dimethylformamide (DMF) and immobilized on the surface of glassy carbon electrode using drop casting method to fabricate PdNPs/PAMAM–MWCNTs modified electrode. The modified electrode showed good catalytic activity for the electrooxidation of oxalic acid in 0.1 M HClO4 with a substantial decrease in anodic overpotentials (450 mV) and increase in anodic peak current (about 3 times) in comparison with unmodified electrode. The values of electron transfer coefficients (α = 0.37) and diffusion coefficient (D = 2.12 × 10−6 cm2 s−1) were calculated for oxalic acid using electrochemical approaches. The cyclic voltammetry showed a linear response in the range of 0.03–5.0 mM with detection limit (3σ) of 0.02 mM for oxalic acid. The experimental results also showed that the sensor has good reproducibility (R.S.D = 4.3% for 5.0 mM, n = 5), long-term stability (over than 100 analysis with intermittent use), and a fast response time (5 s). Finally, the modified electrode was successfully applied to determine the oxalic acid content in spinach.

Wintersweet‐Flower‐Like CoFe2O4/MWCNTs Hybrid Material for High‐Capacity Reversible Lithium Storage

CoFe(2)O(4)/multiwalled carbon nanotubes (MWCNTs) hybrid materials were synthesized by a hydrothermal method. Field emission scanning electron microscopy and transmission electron microscopy analysis confirmed the morphology of the as-prepared hybrid material resembling wintersweet flower "buds on branches", in which CoFe(2)O(4) nanoclusters, consisting of nanocrystals with a size of 5-10 nm, are anchored along carbon nanotubes. When applied as an anode material in lithium ion batteries, the CoFe(2)O(4)/MWCNTs hybrid material exhibited a high performance for reversible lithium storage. In particular, the hybrid anode material delivered reversible lithium storage capacities of 809, 765, 539, and 359 mA h g(-1) at current densities of 180, 450, 900, and 1800 mA g(-1), respectively. The superior performance of CoFe(2)O(4)/MWCNTs hybrid materials could be ascribed to the synergistic pinning effect of the wintersweet-flower-like nanoarchitecture. This strategy could also be applied to synthesize other metal oxide/CNTs hybrid materials as high-capacity anode materials for lithium ion batteries.

Study on the application of reduced graphene oxide and multiwall carbon nanotubes hybrid materials for simultaneous determination of catechol, hydroquinone, p-cresol and nitrite

In this paper, the reduced graphene oxide and multiwall carbon nanotubes hybrid materials (RGO–MWNTs) were prepared and a strategy for detecting environmental contaminations was proposed on the basis of RGO–MWNTs modified electrode. The hybrid materials were characterized by the scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and N2 sorption–desorption isotherms. Due to the excellent catalytic activity, enhanced electrical conductivity and high surface area of the RGO–MWNTs, the simultaneous measurement of hydroquinone (HQ), catechol (CC), p-cresol (PC) and nitrite (NO2−) with four well-separate peaks was achieved at the RGO–MWNTs modified electrode. The linear response ranges for HQ, CC, PC and NO2− were 8.0–391.0μM, 5.5–540.0μM, 5.0–430.0μM and 75.0–6060.0μM, correspondingly, and the detection limits (S/N=3) were 2.6μM, 1.8μM, 1.6μM and 25.0μM, respectively. The outstanding film forming ability of RGO–MWNTs hybrid materials endowed the modified electrode enhanced stability. Furthermore, the fabricated sensor was applied for the simultaneous determination of HQ, CC, PC and NO2− in the river water sample.