As-grown Multi-wall Carbon Nanotubes Research Articles

Synthesis of Multi Wall Carbon Nanotubes based Electronic Sensors for Internet of Things (IoT)

The Internet of Things (IoT) refers to advance devices other than computers that are connected to the Internet and can send and receive information. IoT is a new paradigm that has transformed traditional lifestyles into high-tech ones. It is the notion of a ubiquitous computer environment in which custom-sized electronics are effortlessly implanted into common things. Electronic sensors at the heart of the IoT detect physical/environmental occurrences, translate these measurements into electrical signals, and wirelessly transfer the data for remote computation. Indeed, the 5G communication and cloud computing stimulate the research in applications of carbon nanotubes in electronic devices. CNTs have demonstrated potential applications in electronics, biosensing, artificial intelligence and the Internet of ThingsIn present study, we report the synthesis of Multi Wall Carbon Nanotubes (MWCNTs) by Chemical Vapour Deposition (CVD) at 600C on Zinc Oxide (ZnO) catalyst coated silicon substrate by thermal evaporation technique. As-grown MWCNTs are characterized by Scanning Electron Microscope (SEM). High density growth of MWCNTs have been confirmed by SEM image. Catalyst nanoparticles play very important roles in the decomposition of the hydrocarbon source and to provide nucleation site for growth of MWCNTs. High MWCNT density is required for IoT-based sensors with high performance, sensitivity, selectivity, and distant sensing. Because IoT not only provides services but also creates massive amounts of data. Hence, this study would be helpful for the next generation 5G communication and cloud computing stimulate to enhance living style.

Synthesis and Gas-Sensing Properties of MnO2 – x and MnO2 – x/CuO-Coated Multiwalled Carbon Nanotube Nanocomposites

Nanocomposites based on multiwall carbon nanotubes (MWCNTs) impregnated with manganese oxide MnO2 – x and copper oxide CuO are synthesized and studied. The morphology and elemental composition of MWCNT layers and MWCNT/MnO2 – x and MWCNT/MnO2 – x/CuO nanocomposites are investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. We study the gas-sensing response of the prepared nanocomposites to hydrogen sulfide (H2S) and nitrogen dioxide (NO2). An increase in the conductance observed for the as-grown MWCNTs and the nanocomposites upon NO2 adsorption suggests that these structures exhibit a behavior characteristic of p-type conductivity. Nanocomposites with copper show a markedly enhanced gas-sensing response to H2S.

Effects of different carbon precursors on synthesis of multiwall carbon nanotubes: Purification and Functionalization

Cyclohexanol and xylene were used as carbon precursors, for synthesis of multiwall carbon nanotubes (MWCNTs) arrays in a CVD system at temperature of 750 °C, using nitrogen as carrier gas and ferrocene as catalyst. Different characterization methods were employed to compare the MWCNTs structure synthesized by these two precursors. All scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and Raman spectroscopy results illustrated that using cyclohexanol could significantly reduce formation of amorphous carbon and catalyst particles in the as-grown CNTs. The less amorphous carbon can be attributed to in situ oxidation in presence of oxygen atom of cyclohexanol. Characterizations showed that MWCNTs with high purity could be obtained using cyclohexanol as carbon precursor. The as-grown MWCNTs were purified by oxidation and acid treatment. Characterization of the purified MWCNTs using HNO 3/H 2SO 4 (1/3 or 1/1), 8 M HCl or 8 M HNO 3 was carried out. The results showed that 8 M HNO 3 could be considered as the best chemical to obtain more pure MWCNTs, less amorphous and metal particles and less damaged MWCNTs. The Raman spectroscopy results demonstrated that HNO 3/H 2SO 4 (1/3) treatment could more disorder the MWCNTs structure and this was attributed to the bigger destroying effect of this acid treatment. Furthermore, the TEM analysis of MWCNTs before and after acid treatment revealed that acid treatment could remove encapsulated catalyst particles. The FTIR analysis illustrated that purification of the MWCNTs with nitric acid could connect the functional groups onto the outer surface of MWCNTs and this resulted in more dispersion of the MWCNTs in water.

X-RAY PROPAGATION IN MULTIWALL CARBON NANOTUBES

There is considerable interest in the development of inexpensive lithography techniques for applications in the area of nanoscale electronics. The semiconductor industry is pursuing the development of photolithography techniques such as extreme UV and x-ray. However these techniques are extremely expensive and not suitable for smaller scale applications. In this paper we describe research on the feasibility of exploiting x-ray propagation within carbon nanotubes (CNTs) for the fabrication and characterisation of nanoscale devices. A description is given of a test structure designed to explore experimentally the possibility of x-ray propagation in carbon nanotubes. As x-ray propagation requires a grazing angle of incidence the nanotubes need to be straight and reproducible. In order to alleviate this problem the possibility of using Bragg reflection is investigated. This approach to the problem is stimulated by the inherent Bragg structure of multiwall carbon nanotubes. It is further encouraged by the recent development of coatings using materials such as WS2. Results from simulations presented in this paper show that although Bragg reflection in as-grown multiwall carbon nanotubes is weak the potential for exploitation of this phenomenon in suitably coated nanotubes exists.

Application of oxidized multi-wall carbon nanotubes for Th(IV) adsorption

Th(IV) adsorption onto oxidized multi-wall carbon nanotubes (MWCNTs) was carried out at 293±2K. The effects of MWCNT concentration, pH, and ionic strength were studied. The results showed that Th(IV) adsorption onto oxidized MWCNTs strongly depended on MWCNT concentration and pH, and was weakly dependent on ionic strength. Oxidized MWCNTs showed a higher Th(IV) adsorption capacity than as-grown MWCNTs. The adsorption process followed pseudo second order kinetics. The Freundlich isotherm model described the data better than the Langmuir model. The adsorption mechanism of Th(IV) may be surface complexation. Oxidized MWCNTs may be a promising candidate for the concentration of Th(IV), or its analogue actinides from large volumes.

Modification of carbon nanotubes by laser ablation of copper

Multi-wall carbon nanotubes (MWNTs) were modified by laser ablation of Cu in the presence of He gas. Quasi-spherical particles with diameters of 200 nm to 2 μm were sparsely deposited on as-grown MWNTs. Agglomerated nanoparticles with sizes of 1–10 nm covered ultrasonically treated MWNTs. Both particles were oxidized. The interaction of nanoparticles with the surface of the ultrasonicated MWNTs, due to small charge transfer to carbon atoms of the MWNTs upon adsorption of Cu, was suggested. We discuss the size distribution and morphology of the particles from cluster and particle formation in the gas phase and the surface properties of the two MWNTs.