Carbon nanotube–metal oxide nanocomposites: Fabrication, properties and applications

The need to sense gases and vapors arises in numerous scenarios in industrial, environmental, security and medical applications. Traditionally, this activity has utilized bulky instruments to obtain both qualitative and quantitative information on the constituents of the gas mixture. It is ideal to use sensors for this purpose since they are smaller in size and less expensive; however, their performance in the field must match that of established analytical instruments in order to gain acceptance. In this regard, nanomaterials as sensing media offer advantages in sensitivity, preparation of chip-based sensors and construction of electronic nose for selective detection of analytes of interest. This article provides a review of the use of carbon nanotubes in gas and vapor sensing.

Carbon Nanotube-Based Chemical Sensors

Multi-walled carbon nanotube (MWCNT) film has been fabricated onto Pt-patterned alumina substrates using the chemical vapor deposition method for NH3 gas sensing applications. The MWCNT-based sensor is sensitive to NH3 gas at room temperature. Nanoclusters of Co catalysts have been sputtered on the surface of the MWCNT film to enhance gas sensitivity with respect to unfunctionalized CNT films. The gas sensitivity of Co-functionalized MWCNT-based gas sensors is thus significantly improved. The sensor exhibits good repeatability and high selectivity towards NH3, compared with alcohol and LPG.

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Enhancement of NH3 gas sensitivity at room temperature by carbon nanotube-based sensor coated with Co nanoparticles.

Chemical sensors based on tin dioxide-carbon nanotubes (SnO2-CNT) composite films were fabricated by hot filament chemical vapor deposition (HF-CVD) technique. The composite films consist of SnO2 nanoparticles highly dispersed on the CNTs surface. Their resistivity is highly sensitive to the presence of adsorbates, which become easily attached or detached at room temperature and ambient pressure depending on their gas phase concentration. We systematically studied the sensitivity of the SnO2-CNT composite films for ethanol, methanol and H2S. The results were also compared to those for SnO2 and CNTs separately. It is shown that the SnO2-CNT composite films can detect ethanol, methanol and H2S down to ppm levels below OSHA's permissible exposure limits at room temperature and ambient pressure. Moreover, they self-recover within 1 min without requiring any heating or energy source.

Room temperature gas sensor based on tin dioxide-carbon nanotubes composite films

One step biofunctionalized electrospun multiwalled carbon nanotubes embedded zinc oxide nanowire interface for highly sensitive detection of carcinoma antigen-125

Synthesis and gas sensing characteristic based on metal oxide modification multi wall carbon nanotube composites

Quantum transport properties of mono-bi-monolayer graphene junctions (MBMGJs) are investigated via first principle calculation. The simulation results show that the MBMGJs introduce more effective quantum transport channels in comparing with a full monolayer graphene nanoribbon channel and result in significantly increased on-state current. An overlapping-MBMGJ channel with one overlapping zigzag carbon chain shows a larger current even than a full bilayer graphene channel. The robustness of the effective quantum transport channel introduced by the overlapping-MBMGJ against the variation of the length of the bilayer region is also verified.

Mono-bi-monolayer graphene junction introduced quantum transport channels

Response on the effects of individual differences of common carbon nanotubes on the field emission current stability and the luminescence uniformity of cathode film, a new type of cathode film made of dendritic carbon nanotubes embedded with Zinc oxide quantum dots is proposed. The film of dendritic carbon nanotubes was synthesized through high-temperature pyrolysis of iron phthalocyanine on a silicon substrate coated with zinc oxide nanoparticles. The dendritic structure looks like many small branches protrude from the main branches in SEM and TEM images, and both the branch and the trunk are embedded with Zinc oxide quantum dots. The turn-on field of the dendritic structure film is ∼1.3V/µm at a current of 2 µA, which is much lower than that of the common carbon nanotube film, and the emission current and the luminescence uniformity are better than that of the common one. The whole film emission uniformity has been improved because the multi-emission sites out from the dendritic structure carbon nanotubes cover up the failure and defects of the single emission site.

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Xin Li

Papers

Synthesis and gas sensing characteristic based on metal oxide modification multi wall carbon nanotube composites

Mono-bi-monolayer graphene junction introduced quantum transport channels

Field emission properties of the dendritic carbon nanotubes film embedded with ZnO quantum dots

Carbon nanotube cathode with capping carbon nanosheet

The Gas Sensing Mechanism of the Low-Dimension Carbon Composites with Metal Oxide Quantum Dots