Metal-decorated Carbon Nanotubes Research Articles

Probing the Electronic Structure of Prussian Blue and Analog Films by Photoemission and Electron Energy Loss Spectroscopies.

X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS) were employed to characterize the electronic properties of Prussian blue (PB) and its analogs when electrodeposited over metal-decorated carbon nanotubes (CNTs). Through an investigation of the influence of carbon nanotubes (CNTs) and preparation conditions on the electronic structure, valuable insights were obtained regarding their effects on electrochemical properties. XPS analysis enabled the probing of the chemical composition and oxidation states of the film materials, unveiling synthesis-driven variations in their electronic properties. REELS provided information on energy loss and electronic transitions, enabling further characterization of the changes in the electronic structure induced by different preparation methods. Such findings emphasize the importance of surface characterization to understand how the unique electronic properties of such materials can be harnessed to enhance their performance and functionality.

Density functional theory study of adsorption and dissociation of CH2Cl2 on the surfaces of transition metal (Fe, Co, Ni, and Cu)-doped carbon nanotubes

A DFT study was carried out on the adsorption capacity and dissociation mechanism of dichloromethane by intrinsic carbon nanotubes and Fe, Co, Ni and Cu adsorption-modified carbon nanotube systems. The calculated results indicated the dopant of transition metal can effectively enhance the electronic properties of carbon nanotubes. The adsorption of carbon nanotubes for CH2Cl2 is also enhanced, and the dissociations of CH2Cl2 on the four metal-decorated carbon nanotubes are exothermic. Especially in the case of Fe adsorption modification (adsorption energy reaches -1.91 eV), which is much higher than the intrinsic carbon nanotube adsorption energy of CH2Cl2 (-0.38 eV), and the reactive energy barrier of the dissociation process of the CH2Cl2 is as low as 0.493 eV. Meanwhile, the dissociation process can occur spontaneously at room temperature, which contributes to the dissociation of CH2Cl2 on Fe adsorption-modified carbon nanotube systems, providing theoretical support for the subsequent governance process of CH2Cl2.

Co metal-decorated carbon nanotubes with excellent thermal catalytic performance

Co metal-decorated carbon nanotubes with excellent thermal catalytic performance

A density functional theory study on the interaction of toluene with transition metal decorated carbon nanotubes: a promising platform for early detection of lung cancer from human breath

In this study, single-wall carbon nanotubes (SWCNTs) decorated by platinum-group transition metals (Pt, Pd, Rh, or Ru) were introduced as promising nanosensors for the detection of toluene, an important biomarker in the exhaled breath of the lung cancer patients. First-principle calculations based on density functional theory (DFT) was employed to scrutinize the impact of an individual toluene gas molecule on the structural, electronic, and magnetic properties of pristine and metal decorated SWCNTs. It was discovered that toluene is physisorbed on the pristine SWCNT through the interaction of the π orbitals of the carbon atoms in the toluene and the nanotube. Decoration of the SWCNT with metal atoms enhanced the adsorption energies significantly by means of strong overlapping between d orbital of the metal atoms and p orbital of C atoms in the benzene ring of toluene. Investigations showed that toluene is strongly chemisorbed on Rh- and Ru-SWCNT systems via strong covalent bonds with the superior response (−96.98% and −99.98%, respectively), and moderately chemisorbed on Pt-SWCNTs (−27.3%) and Pd-SWCNTs (61.60%). Our findings propose metal decorated SWCNT molecular sensors are attractive candidates for the detection of toluene and other lung cancer biomarkers in the exhaled breath of the lung cancer patients.

Adsorption behavior analyses of several small gas molecules onto Rh-doped single-walled carbon nanotubes

Owing to the excellent adsorption performance, the transition metal-decorated carbon nanotubes (CNTs) have received widespread attention, and consequently have served an increasingly important role in the areas of gas detection and storage recently. Based on density functional theory method, a novel Rh-modified single-walled CNT is proposed in the present work to explore its adsorption behaviors upon some small gas molecules including CO, CO2, CH4, C2H4 and SO2 for the sake of suggesting potentially promising materials in terms of gas adsorbent/sensors. The calculated results indicated that Rh–CNT has good adsorption performance upon CO, C2H4 and SO2 molecules given their large adsorption energies and small adsorption distances while exhibiting insensitivity towards CO2 and CH4 due to their weak interaction basically depending on Van der Waals’ force. Our calculations are meaningful for providing experimentalists with strong theoretical foundation in further applications of such novel sensing material.

Metal decorated carbon nanotubes for electrocatalytic water splitting

Water is the most abundant, renewable source of hydrogen on our planet. Appropriate catalytic materials are needed to minimize the energy required to electrochemically split the water molecule, and electrode with high specific areas are sought to maximize the electrolyte/electrode interface. We use Carbon Nanotubes (CNTs) bundles as templates for water splitting electrodes fabrication. Appropriate catalyst materials are thermally evaporated on CNTs, to exploit both their good electrical conductivity and large specific area, while optimizing over-potential towards Hydrogen Evolving Reaction (HER) or Oxygen Evolving Reaction (OER) through the deposited catalysts. Electrodes morphology and surface chemistry are characterized, before and after electrolysis, by means of scanning electron microscopy and X-ray photoelectron spectroscopy. Our electrodes are able to perform water oxidation and water reduction near their thermo-dynamical limit. Performances of these electrodes, taking into account the extremely low loading mass of catalytic material (10−2 mg cm−2) with respect to other reported systems, are among the best HER and OER system reported so far. Finally, a working electrolyser, capable to operate at the interesting low voltage of a single AA battery (1.5 V) and output a stable current (>2.0 mA cm−2) for at least 20 h, is successfully assembled and tested.

Adsorption performance of Rh decorated SWCNT upon SF6 decomposed components based on DFT method

Transition metal decorated carbon nanotubes (CNTs) applied in the field of gas adsorption and storage have in recent years accepted considerable attentions because of their superior adsorbing performance. In electrical engineering, they are employed as adsorbents to remove the decomposed products of SF6 caused by partial discharge, for guaranteeing the insulation status of gas insulation switchgear (GIS). In this paper, Rh doped SWCNT is introduced to investigate its adsorption properties towards typical gases of SF6 based on density functional theory (DFT) method. Both single and double molecules adsorbing systems were performed to investigate the adsorption ability of proposed material. Results indicate that Rh-CNT, which has strong interaction with defined gas molecules, is a promising material for SF6 decompositions adsorption especially SO2 and SOF2 that exhibit topmost sensitivity to the modified surface. Therefore, we suggest the Rh-CNT to be an adsorbent to be applied in GIS for guaranteeing the operation state of such devices and even to be exploited as gas sensor to evaluate the insulation state of the power system. Our calculations would provide experimentalist with a first insight into physicochemical properties of this material.

Field emission with ultralow turn on voltage from metal decorated carbon nanotubes.

A simple and scalable method of decorating 3D-carbon nanotube (CNT) forest with metal particles has been developed. The results observed in aluminum (Al) decorated CNTs and copper (Cu) decorated CNTs on silicon (Si) and Inconel are compared with undecorated samples. A significant improvement in the field emission characteristics of the cold cathode was observed with ultralow turn on voltage (Eto ∼ 0.1 V/μm) due to decoration of CNTs with metal nanoparticles. Contact resistance between the CNTs and the substrate has also been reduced to a large extent, allowing us to get stable emission for longer duration without any current degradation, thereby providing a possibility of their use in vacuum microelectronic devices.

Preparation of Pt- and Pd-decorated CNTs by DCC-activated amidation and investigation of their electrocatalytic activities

Pt- and Pd-decorated carbon nanotubes (CNTs) have been prepared by diimide-activated amidation, an approach that avoids the harmful products of conventional SOCl 2 treatment. In this study, N, N′-dicyclohexylcarbodiimide (DCC) was used as a coupling agent for the formation of an amide linkage. According to ICP measurements, the resulting materials consist of 7.1 wt.% loaded Pt and 8.6 wt.% loaded Pd. The TEM images show that size-similar and quasi-spherical nanoparticles are highly dispersed along the entire CNT walls. The prepared Pt-CNT exhibited an especially high oxidation current toward methanol, formic acid, and formaldehyde compared with that of the pristine CNT and a Pt/CNT mixture (10 wt.% Pt). Furthermore, the Pd-CNT displayed higher activity toward H 2O 2 reduction than that of the reference systems. The better catalytic activities can be explained by the high electrochemically active surface area that resulted from the smaller size and excellent dispersion of metal nanoparticles on CNT. These results demonstrate the DCC-activated amidation to be a very effective and useful way to tune size and disperse metal species in metal-decorated CNTs, markedly improving their catalytic activity.

Quantitative trace analysis of benzene using an array of plasma-treated metal-decorated carbon nanotubes and fuzzy adaptive resonant theory techniques

The functionalization of carbon nanotube sidewalls with metal nanoparticles is exploited here to improve the sensitivity and selectivity of gas sensors operated at room temperature. An array of sensors using oxygen plasma treated multiwalled carbon nanotubes (bare and decorated with Pt, Pd or Rh nanoparticles) is shown to selectively detect traces of benzene (i.e., 100 ppb) in the presence of carbon monoxide, hydrogen sulfide or nitrogen dioxide at different humidity levels. Employing a quantitative fuzzy adaptive resonant theory (ART) network whose inputs are the responses of the sensor array, it is possible to accurately estimate benzene concentration in a changing background. The quantitative fuzzy ART is especially suited for compensating the nonlinear effects in sensor response caused by changes in ambient humidity, which explains why this method clearly outperforms partial least squares calibration models at estimating benzene concentration. These results open the way to design new affordable, wearable, sensitive and selective detectors aimed at the personal protection of workers subject to occupational exposure to benzene, toluene, ethyl benzene and xylenes.

Hydrogen sulfide sensing properties of multi walled carbon nanotubes

This paper investigates the effect of functional groups on the hydrogen sulfide sensing properties of multi-walled carbon nanotubes using carboxyl and amide groups and Mo and Pt nanoparticles as decorated precursors in gaseous state at working temperature. Carbon nanotubes were synthesized by the CVD process and decorated with the nano particles; provide higher sensitivity for H 2S gas detection. The MWCNTs were characterized by scanning electron microscopy combined with energy dispersive X-ray (SEM/EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), ATR-IR absorption and Fourier transforms infrared (FT-IR) analyses. The MWCNTs were deposited as a thin film layer between prefabricated gold electrodes on alumina surfaces. The sensitivity of carbon nanotubes was measured for different H 2S gas concentrations and at working temperature. The results showed that the measured electrical conductance of the modified carbon nanotubes with functional groups is modulated by charge transfer with P-type semiconducting characteristics and metal decorated carbon nanotubes exhibit better performances compared to functional groups of carboxyl and amide for H 2S gas monitoring at room temperature.

Selective detection of benzene traces at room temperature using metal decorated carbon nanotubes

Hybrid materials consisting of oxygen plasma treated multiwalled carbon nanotubes (MWCNTs) decorated with four different metal nanoparticles can be tailored for the recognition of benzene vapors with high sensitivity and selectivity. The plasma treatment enables cleaning, activating, functionalizing and metal decorating carbon nanotubes in a single step. Metal nanoparticles transfer significant amount of charge upon adsorption of a target molecule, so as to affect electron transport in the nanotube. When combined in a microsensor array operating at room temperature, the use of benzene-sensitive and benzene-insensitive metal-decorated multiwalled carbon nanotubes can provide selective detection of benzene at trace levels (i.e., detection limit below 50 ppb.

Novel hexagonal WO3 nanopowder with metal decorated carbon nanotubes as NO2 gas sensor

Abstract In this work, hexagonal tungsten oxide (hex-WO3) nanopowders were prepared by acidic precipitation from a sodium tungstate solution. TEM analysis of nanopowders showed that the average size of the hexagonal nanoparticles was 50–100 nm. Novel hybrid composites were fabricated by embedding a low amount of carbon nanotubes into the hex-WO3 matrix. Metallic nanoclusters (Ag, Au) were added to the carbon nanotubes for improving the gas sensing properties of the films. The addition of MWCNTs lowered the temperature range of sensitivity of the hex-WO3 nanocomposites to NO2 hazardous gas. In comparison, the sensitivity of hex-WO3 to NO2 was in the temperature range between 150 °C and 250 °C, while the hex-WO3/MWCNTs composites were sensitive to NO2 gas at room temperature.

Gas Sensor Array Based on Metal-Decorated Carbon Nanotubes

Here we demonstrate design, fabrication, and testing of electronic sensor array based on single-walled carbon nanotubes (SWNTs). Multiple sensor elements consisting of isolated networks of SWNTs were integrated into Si chips by chemical vapor deposition (CVD) and photolithography processes. For chemical selectivity, SWNTs were decorated with metal nanoparticles. The differences in catalytic activity of 18 catalytic metals for detection of H(2), CH(4), CO, and H(2)S gases were observed. Furthermore, a sensor array was fabricated by site-selective electroplating of Pd, Pt, Rh, and Au metals on isolated SWNT networks located on a single chip. The resulting electronic sensor array, which was comprised of several functional SWNT network sensors, was exposed to a randomized series of toxic/combustible gases. Electronic responses of all sensor elements were recorded and the sensor array data was analyzed using pattern-recognition analysis tools. Applications of these small-size, low-power, electronic sensor arrays are in the detection and identification of toxic/combustible gases for personal safety and air pollution monitoring.