TiO2 Multi-walled Carbon Nanotubes Research Articles

Preparation and characterization of ball milled titanium oxide/multi walled carbon nanotube nanocomposite for supercapacitor applications

In this work, titanium oxide nanoparticles (TiO2 NPs) and TiO2-Multi walled carbon nanotubes (MWCNTs) nanocomposites were prepared using the ball milling technique. The characterization of synthesized nanocomposite was done using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), Raman spectroscopy, and transmission electron microscopy (TEM). Dielectric constant ε1 (ω) and dielectric loss ε2 (ω) were discussed in terms of the dielectric polarization process. The Ac conductivity was increased with increasing MWCNTs amount. The charge carrier transport mechanism was interpreted using the correlated barrier hopping model (CBH). The Impedance spectroscopy showed a non-Debye relaxation in the material. The specific capacitance was increased with increasing MWCNTs concentration. Based on these detailed results, the TiO2-MWCNTs nanocomposites displayed higher specific capacitance than TiO2. In addition, the control of the current density applied onto CV measurements and MWCNTs composition of the electrodes to enhance the capacitance will open up a new strategy for the high-performance supercapacitors.

Mechanical, thermal, and flammability properties of polyamide-6 reinforced with a combination of carbon nanotubes and titanium dioxide for under-the-hood applications

The current study aims to explore the tensile fracture mechanism and thermo-mechanical efficiency of polyamide-6 (PA6) reinforced with titanium dioxide (TiO2) and multiwalled carbon nanotubes (MWCNTs). The uniform dispersion of the MWCNTs and appreciable interfacing between PA6, TiO2, and MWCNTs were revealed in the fractography figures. The crystallization temperature and degree of crystallinity have been enhanced by the addition of nanoparticles to the PA6 matrix. Young’s modulus, tensile strength, and Charpy impact strength improved proportionally concerning reinforcement content. The essential work of fracture (EWF) method was applied to evaluate the toughening and fracture behavior of PA6 hybrid systems. Considerable improvement (+60.6%) in the EWF of PA6–TiO2–MWCNT nanocomposites was observed at 4 wt.% CNT and 2 wt.% TiO2. Limiting oxygen index (LOI) findings demonstrate that a polymer with a combination containing titanium dioxide and multiwalled carbon nanotubes has a highly substantial retardant influence. As a result, the TiO2–CNT combination acts as a synergist filler, offering versatile PA6 composite products.

Synthesis of Fe- or Ag-doped TiO2–MWCNT nanocomposite thin films and their visible-light-induced catalysis of dye degradation and antibacterial activity

Thin films of TiO2, TiO2-multiwalled carbon nanotubes (TiO2–MWCNT), Fe-doped TiO2–MWCNT (Fe–TiO2–MWCNT), and Ag-doped TiO2–MWCNT (Ag–TiO2–MWCNT) supported on glass substrates were successfully prepared by sol–gel drop coating method. MWCNTs were treated by H2SO4 and HNO3 to oxidize graphitic carbon. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV-Vis) absorption spectroscopy to confirm their structure and optical properties. XRD patterns of all prepared films exhibited (101), (004), (200), (105), (211), (204), (116), (220), (215), and (224) planes of anatase-phase TiO2. A pronounced broad peak at ~3400 cm−1 in the FTIR spectrum of the MWCNT confirmed oxidation of some carbon atoms on the surface of MWCNTs by HNO3 and H2SO4. The photocatalytic and antibacterial activities of the prepared materials were tested under visible-light irradiation based on degradation of methylene blue (MB) dye in aqueous solution and reduction in the viable count of Escherichia coli, respectively. Fe or Ag was doped into the TiO2-MWCNT composites, lowering the bandgap and thereby enabling enhanced photocatalytic activity in the visible-light region. Based on the MB photodegradation results, the photocatalytic efficiency of the Fe–TiO2–MWCNT and Ag–TiO2–MWCNT composites could be due to the following mechanism: (1) adsorption and photoinduced electron absorption by MWCNT, and (2) electron trapping by Fe or Ag within the TiO2 matrix, in addition to the usual photocatalytic activity of TiO2. Moreover, as-synthesized Ag–TiO2–MWCNT composite films showed outstanding antimicrobial activity.

Multi-walled carbon nanotubes/TiO2 thin layer for photocatalytic degradation of organic pollutant under visible light irradiation

This paper is based on preparation of MWCNT/TiO2 photoactive thin layer deposited on glass substrate using the sol–gel dip-coating technique. The thin layer consists of TiO2 coupled with different amount of per-noncovalent functionalized multi-walled carbon nanotubes (MWCNTs). The optimum MWCNTs/TiO2 weight ratio in the thin film was found to be 1.75 % under the experimental conditions investigated. The MWCNT/TiO2 film was characterized by a range of analytical techniques including: scanning electron microscopy, atomic force microscopy, X-ray diffraction, photoluminescence spectra, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. The photoactivity of the prepared films, under visible light irradiation, was evaluated by decoloration of methyl orange (MO). Complete decoloration of MO was observed only in 2 h under visible light irradiation. Furthermore, we used chemical oxygen demand (COD) method to determine the degradation efficiency of the MWCNT/TiO2 thin layer. 42 % reduction in COD value of treated MO solution shows substantial degradation of MO by photoactive film. According to the results of MO removal experiment, the excellent activity of the photoactive film can be attributed to the strong interaction between TiO2 particles and MWCNT bundles and the high electron acceptability of CNTs network.

Comparison between Experimental and Theoretical Thermal Conductivity of Nanofluids Containing Multi-walled Carbon Nanotubes Decorated with TiO2 Nanoparticles

This article reports the thermal conductivity modeling of nanofluids containing decorated multi-walled carbon nanotubes with TiO2 nanoparticles. TiO2 nanoparticles and decorated multi-walled carbon nanotubes are synthesized with different amounts of TiO2 nanoparticles. The experimental results show that the measured thermal conductivities of TiO2 nanofluids and multi-walled carbon nanotube nanofluids are higher than the predicted values by theoretical models. The comparison results of multi-walled carbon nanotube nanofluids and multi-walled carbon nanotube–TiO2 nanofluids reveal that the predicted values by the Xue model are closer to the measured values. In addition, the results show that the thermal conductivity of nanofluids containing multi-walled carbon nanotube–TiO2 increases with respect to TiO2 content of hybrid.

Designing of TiO2/MWCNT Nanocomposites for Photocatalytic Degradation of Organic Dye

The nanocomposites were obtained from commercial multi-walled carbon nanotubes (MWCNTs) and with titanium tetra propoxide as TiO2 precursor, and heat treated at 400°C and 500°C to form crystalline phases of TiO2. The nanocomposites were investigated for their photocatalytic activity, employing them as catalysts in the degradation of organic methyl orange dye in an aqueous solution under UV radiation. The results were associated with the characteristics of the nanocomposite structure, using techniques such as x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Optical characterization was obtained by photoluminescence spectroscopy and diffuse reflectance spectroscopy. The highest photocatalytic efficiency was observed in the TiO2–MWCNT nanocomposites obtained in an acid medium and heat treated at 500°C. These results could be associated with the lower transition energy and level of defects in the TiO2 of these nanocomposites when compared to the other samples.

Preparation of TiO2–MWCNT core/shell heterostructures containing a single MWCNT and their electromagnetic properties

TiO2–MWCNT core/shell heterostructures containing a single MWCNT have been successfully prepared via solvothermal method. TiO2–MWCNT heterostructures with different morphologies and electromagnetic (EM) properties have obtained by adjusting the weight ratio of titanium dioxide (TiO2) and multi-walled carbon nanotubes (MWCNT) (weight ratio: 1:1, 5:1 and 10:1). EDS spectrum and X-ray diffraction analysis reveal that the product is composed of Ti, O, and C elements, and the crystal structure of TiO2 is tetragonal anatase phase. SEM and TEM images show that the MWCNTs are coated by a thin layer of TiO2 crystals, and the average diameters of the needle-like TiO2 nanocrystals are less than 100 nm. EM properties of the as-prepared TiO2–MWCNT heterostructures are investigated in the 0.5–18.0 GHz range. The permittivity and permeability of the TiO2–MWCNT heterostructures change obviously as the weight ratio of TiO2 and MWCNT increases. Moreover, the typical resonance–antiresonance phenomenon can be observed in the permittivity and permeability curves.

Fabrication of a reusable magnetic multi-walled carbon nanotube–TiO2 nanocomposite by electrostatic adsorption: enhanced photodegradation of malachite green

A simple, quick and efficient method for the fabrication of a magnetic multi-walled carbon nanotube–TiO2 (MMWCNT–TiO2) nanocomposite through electrostatic attraction was proposed as a novel method.

Enhanced solid-phase photocatalytic degradation of polyethylene by TiO2–MWCNTs nanocomposites

In this work, a novel acid vapor method was introduced to prepare the water soluble multi-walled carbon nanotubes (MWCNTs) and the titanium dioxide (TiO2)–MWCNTs nanocomposites photocatalyst were successfully synthesized by sol–gel solvothermal method. Products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the anatase TiO2 particles were uniform deposited on MWCNTs surface. UV–vis diffuse reflectance spectroscopy (UV–vis) showed that composite photocatalyst had an obviously absorption band which covered the whole range of UV–vis region and exhibited a significant enhancement of optical absorption property. Based on above properties, we used the TiO2–MWCNTs composites as photocatalysts to degrade the polyethylene (PE) plastic. Solid-phase PE film photocatalytic degradation experiments were investigated through monitoring TiO2–MWCNTs–PE composite film's weight loss under mercury lamp irradiation. Results showed that the degradation efficiency could be tuned by changing the concentration of MWCNTs in photocatalyst. The photo-induced degradation of composite film was significantly higher than that of the pure PE film and the Degussa P25-PE film under the same UV irradiation. The weight loss of TiO2–MWCNTs (20 wt%)–PE sample reached 35% under 180 h UV-light irradiation. Our work could be extended to synthesize other MWCNTs based composite with the purpose of enhancing TiO2's activity and inspiring for the practical environmental pollution, especially for degradation of plastics.

Enhancing photovoltaic performances of dye-sensitized solar cells by multi-layered nanostructured titanium oxide photoelectrode

In the present study, a multi-layered nanostructured titanium oxide film has been fabricated as the photoelectrode for dye-sensitized solar cells (DSSCs). The multi-layered TiO2 electrode has the advantages of easy fabrication, being compatible with current deposition process and readily modifiable by adjusting the process parameters. The application of TiO2–MWCNTs (multiwalled carbon nanotube) as a nanocomposite overlayer reduces the inhomogeneity of dispersing carbon nanotubes (CNTs) throughout the whole photoanode, which largely simplifies the fabrication process and improves the performance of the as-prepared photoanodes. By using a multi-layered photoelectrode comprising a structure of TiO2–MWCNT/Degussa P25-TiO2/compact TiO2/TCO glass, a 27% enhancement in conversion efficiency is realized in DSSC as compared with pristine P25-TiO2 photoanode of identical thickness. The enhancement in efficiency brought by incorporation of MWCNTs, as revealed by electrochemical impedance spectroscopy (EIS), could be attributed to the excellent charge transport properties of CNTs, which led to efficient charge transfer within nanoporous TiO2 networks. A compact TiO2 blocking layer suppresses effectively the dark current, thus enhancing both JSC and VOC prominently.

Preliminary study towards photoactivity enhancement using a biocompatible titanium dioxide/carbon nanotubes composite

Recent research is focused on the enhancement in photoactivity of titanium dioxide/carbon nanotubes through formation of novel nanocomposites that exhibit a high specific surface area, remarkable electron transfer and biocompatibility. Here, we explore a new synthesis route in the system composed of nanocrystalline titanium dioxide supported on external walls and inner space of multiwalled carbon nanotubes (MWCNT). The advantages of this method are: its simplicity, direct fusion of titanium dioxide particles on the carbon material, and formation of chemical bond Ti–O–C between TiO2 and MWCNT. Photocatalytic performance of this system has been compared to a commercial catalyst (Degussa P25) in a model reaction of phenol decomposition in/under UV light. The efficiency of the process increased by the factor of 2.5 when the TiO2–MWCNT photocatalyst was utilized. Further, the photoactive nanocomposite was analysed towards its biocompatibility in order to establish a safe dose of the catalyst. Its influence on the cells viability was studied on mouse fibroblasts and human liver tissue cells, in the range from 0 to 100μg/mL. This has revealed that the composite in concentrations up to 25μg/mL exerted low toxicity, which allowed for finding a compromise between the highest safe dose and acceptable photoactivity of the catalyst.

Temperature-dependent charge transport in TiO2–multiwalled carbon nanotube composites

Charge transport properties of TiO2–multiwalled carbon nanotube (MWCNT) composites were investigated. The TiO2–MWCNT composites were fabricated by spark plasma sintering of a mixture of TiO2 nanoparticles and MWCNTs. Temperature-dependent electrical conductivities of the composites reveal that the percolation threshold for the MWCNT network is affected by temperature, and that the activation process for electron hopping is also influenced by the percolation. Based on this interdependence, an integrated charge transport model, including both the effects of the percolation and the electron hopping, is proposed for this system.

Hydrothermal synthesis of single-walled carbon nanotube–TiO2 hybrid and its photocatalytic activity

A single-walled carbon nanotube (SWCNT)–TiO2 hybrid was prepared hydrothermally by direct growth of TiO2 nanoparticles on the surface of functionalized SWCNTs to develop highly efficient photocatalysts. The SWCNT–TiO2 hybrid was characterized by X-ray diffraction, electron microscopy, N2-adsorption analysis, FT-IR, Raman, and UV–vis spectroscopy. The photocatalytic activity of the SWCNT–TiO2 hybrid was examined by the photocatalytic degradation of pirimicarb. Although the SWCNT–TiO2 hybrid exhibits no visible-light-induced activity, the photocatalytic degradation efficiency of pirimicarb over TiO2 can be increased significantly with the introduction of SWCNTs (2–3 times) because SWCNTs can act as electron conductors that hinder the recombination of photo-generated electrons and holes. Compared with a multi-walled carbon nanotube–TiO2 hybrid, it can be found that the electronic configurations of carbon nanotubes significantly affect the photocatalytic activity of carbon nanotube–TiO2 hybrid. Metal-typed SWCNTs act more as an electrical conductor than a photosensitizer, which efficiently suppress charge recombination, improve interfacial charge transfer, and improve the photoactivity.

TiO2-Multi Walled Carbon Nanotubes Hybrid Film Sensor for Sensing of Antiprotozoal Agent Satranidazole in Solubilzed System

A highly sensitive and stable TiO2- multi walled carbon nanotubes (TiO2-MWCNTs) composite film modified glassy carbon electrode was fabricated and characterized. The excellent electrocatalytic activity and the influence of composite film results in good characteristics such as low potential detection of satranidazole (STZ) with a low detection limit, fast response, good stability and anti-interferent ability. The incorporation of TiO2 nanoparticles with multi walled carbon nanotubes (MWCNTs) greatly increases the voltammetric peak current and electrochemical reactivity of STZ in comparison to that at the MWCNTs film. The morphologies and electrochemical performance of the modified TiO2-MWCNTs/GC electrode was investigated by scanning electron microscopy (SEM), impedance spectroscopy, cyclic voltammetry (CV) and square wave voltammetry. The electrochemical sensor shows excellent analytical performance and exhibits wide linear range of 80 ng mL−1−100 μg mL−1 with detection limit of 2.809 ng mL−1 and quantification limit of 9.365 ng mL−1.

Synthesis, characterization, and its photocatalytic activity of double-walled carbon nanotubes-TiO2 hybrid

Double-walled carbon nanotube (DWCNT)-TiO2 hybrid was prepared by hydrothermal method and characterized by X-ray diffraction, electron microscopy, N2-adsorption analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of DWCNT-TiO2 hybrid was tested by the photocatalytic degradation of sulfathiazole. The experimental results showed that the introduction of the DWCNTs provides DWCNT-TiO2 hybrid with visible light-induced photoactivity and a large surface area. The DWCNTs were coated with TiO2 nanoparticles, which generated an intimate contact between the DWCNTs and TiO2. The DWCNT-TiO2 hybrid showed an excellent visible-light-induced activity, compared with multi-walled carbon nanotube-TiO2 and single-walled carbon nanotube-TiO2 hybrids, which can be attributed to the unique electronic structure of the DWCNTs that can work well as not only a photosensitizer but also an electron conductor. In addition, DWCNT-TiO2 hybrid with the DWCNTs of long length showed higher degradation efficiency than that with the short length.

Dispersing agents for electrophoretic deposition of TiO2 and TiO2–carbon nanotube composites

Organic anionic molecules such as 2,3-dihydroxybenzoic acid (DBA23), 2,6-dihydroxybenzoic acid (DBA26), 5-sulfosalicylic acid (SSA) and pyrocatecholsulfonphthalein (PCS) were investigated for electrophoretic deposition (EPD) of TiO2 and TiO2–multiwalled carbon nanotube (MWCNT) films from suspensions in ethanol. The adsorption of the molecules on TiO2 surfaces was based on catecholate or salicylate binding, involving adjacent OH groups or adjacent OH and COOH groups, respectively. The adsorption of the anionic molecules allowed efficient dispersion, charging and EPD of TiO2. The deposition yield was studied as a function of DBA23, DBA26, SSA and PCS concentration in TiO2 suspensions and deposition time. An important finding was the possibility of efficient dispersion, charging and EPD of MWCNT using PCS. It was shown that PCS can be used as a universal dispersing agent for co-deposition of TiO2 and MWCNT and fabrication of composite TiO2–MWCNT films. The advantages of the new strategies, compared to other methods described in literature, were discussed. The deposits were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The proposed approach paves the way for EPD of other oxide materials and composites.

Dye-sensitized solar cells based on anatase TiO2/multi-walled carbon nanotubes composite nanofibers photoanode

Anatase TiO2/multi-walled carbon nanotubes (TiO2/MWCNTs) hybrid nanofibers (NFs) film was prepared via a facile electrospinning method. Dye-sensitized solar cells (DSSCs) based on TiO2/MWCNTs composite NFs photoanodes with different contents of MWCNTs (0, 0.1, 0.3, 0.5, 1wt.%) were assembled using N719 dye as sensitizer. Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), and Raman spectrometer were used to characterize the TiO2/MWCNTs electrode films. The photocurrent–voltage (I–V) characteristic, incident photo-to-current conversion efficiency (IPCE) spectrum, and electrochemical impedance spectroscopy (EIS) measurements were carried out to evaluate the photoelectric properties of the DSSCs. The results reveal that the energy conversion efficiency is greatly dependent on the content of MWCNTs in the composite NFs film, and a moderate incorporation of MWCNTs can substantially enhance the performance of DSSCs. When the electrode contains 0.3wt.% MWCNTs, the corresponding solar cell yield the highest efficiency of 5.63%. This efficiency value is approximately 26% larger than that of the unmodified counterpart.

Photocatalytic Degradation of Sulfonamides over the Short Multi-Walled Carbon Nanotube-TiO<sub>2</sub> Hybrid

The short multi-walled carbon nanotube-TiO2 (SMWNT-TiO2) hybrid was synthesized via direct growth of TiO2 nanoparticles on the surface of the functionalized SMWNTs by the hydrothermal treatment and utilized as the photocatalyst in the sulfonamides degradation under UV light irradiation. The photodegradation efficiency of sulfonamides was examined by HPLC technique, which demonstrates that sulfonamides can be readily degraded under UV light irradiation. However, the four sulfonamides have different degradation rates, which is in the order of sulfadimidine > sulfanilamide > sulfamethoxazole > sulfathiazole. These experimental results can be attributed to the point charge of the atoms in the sulfonamide molecule and its adsorption on the surface of the SMWNT-TiO2 hybrid.

TiO2 Nanotubes/MWCNTs Nanocomposite Photocatalysts: Synthesis, Characterization and Photocatalytic Hydrogen Evolution Under UV-Vis Light Illumination

Nanocomposite of TiO2 nanotubes (TiO2NTs) and multiwalled carbon nanotubes (MWCNTs) has been synthesized by a hydrothermal method and firstly used in photocatalytic hydrogen production. The obtained TiO2 NTs/MWCNTs composites were characterized by X-ray diffraction, transmission electron microscopy, Raman spectrum and ultraviolet-visible diffuse reflectance spectroscopy. The experimental results revealed that the MWCNTs were decorated with well dispersed anatase TiO2 nanotubes with a diameter of 8-15 nm. A slight blue shift and weak symmetry was observed for the strongest Raman peak which resulted from strain gradients originating from interface integration between TiO2 nanotubes and MWCNTs. The photocatalytic activity of the as-prepared samples was evaluated by hydrogen evolution from water splitting using Na2S and Na2SO3 as sacrificial reagents under UV-vis light irradiation. Enhanced photocatalytic activity compared with P25 has been observed for the resulted samples. The nanocomposite with optimized MWCNTs content of 1% displayed a hydrogen production rate of 161 micromol x h(-1) x g(-1). Good photocatalytic stability of the as-synthesized samples was observed as well.

TiO2–MWCNT rice grain-shaped nanocomposites—Synthesis, characterization and photocatalysis

Abstract Titanium dioxide (TiO 2 )-multiwalled carbon nanotube (MWCNT) nanocomposites with a novel morphology of rice-grains are prepared by electrospinning method. Anatase-MWCNT composites (with a negligibly small percentage of rutile and brookite) are obtained by high temperature sintering of the as-spun (polymer-TiO 2 –MWCNT) composite fibers. The nanocomposites are characterized using spectroscopy and microscopy. The results show that the functionalized MWCNTs are integrated into the TiO 2 rice grain structures. The enhanced photocatalysis of the nanocomposites in comparison to TiO 2 rice grains and commercially available P-25 is demonstrated in photodegradation of Alizarin Red dye.