Zinc Oxide Nanotubes Research Articles

Synthesis and characterization of ZnO-MWCNT nanocomposites for 1-butanol sensing application at room temperature

Zinc oxide and multiwall carbon nanotubes ZnO/(MWCNT) composites were synthesised using wet chemical method and annealed at 400 °C for 1 h. They were studied for their microstructure, morphology, optical, electrical and gas sensing properties. SEM analysis showed uniform hexagonal disc like structure of ZnO within the fibers of MWCNT. XRD pattern indicated that the crystalline nature of the sample with hexagonal wurtzite phase. The crystallite size was reduced due to the increased MWCNT concentration. Optical band gap was determined using Tauc's plot. It was decreased from 3.12eV to 2.97eV with increasing MWCNT concentration. FTIR spectra confirmed the Zn–O stretching and carboxylic group in the ZnO composite samples. I–V curve showed the ohmic nature of sample. 1-butanol sensing properties were studied at the room temperature of 27 °C in static mode. Experiment results indicated a highest sensitivity with ZnO at 500 ppm. Whereas ZnO/MWCNT composite sensor showed faster response and recovery times.

Layer by Layer Assembly of Zinc Oxide Nanotubes and Nanoflowers as Catalyst for Separate and Simultaneous Catalytic Degradation of Dyes and Fuel Additive

AbstractZinc oxide nanotubes and nanoflowers are synthesized using urea as template through hydrothermal technique. XRD confirmed that product is consists of zinc and oxygen atoms forming a hexagonal crystal system with ZnO chemical formula. SEM showed that tubes and flower like particles are formed. ATR‐IR confirmed the presence of Zn−O bond as a functional group. UV‐VIS spectroscopic analysis exhibits that product has a band gap energy of 3.49 eV. Synthesized product due to its outstanding properties such as wide band gap semiconductor and large surface area to volume ratio is used as a catalyst for individual and simultaneous catalytic degradation of methylene blue (MB) and Congo red (CR) dyes. The apparent rate constant (kapp) value of individual and simultaneous catalytic degradation of CR dye is decreased with increase in catalyst dosage while kapp value of individual and simultaneous catalytic degradation of MB dye is increased with increase in catalyst dosage. The synthesized product is found more active towards CR dye as compared to MB dye. Small size and high surface area to volume ratio of product also make it a desirable additive for enhancing the efficiency of diesel fuel. Results obtained from fuel additive activity show that as the concentration of nanoadditive is increased from 20, 40, 60, 80 and 100 ppm the calorific value is increased which indicates the enhanced efficiency of fuel due to additive.

Solution-Processed Hybrid Ambipolar Thin-Film Transistors Fabricated at Low Temperature

We demonstrate solution-processed hybrid ambipolar thin-film transistors (TFTs) employing a stack structure composed of indium–gallium–zinc-oxide (IGZO) and single-wall carbon nanotube (SWCNT) as an active channel fabricated at low temperature. With an optimized deep-ultraviolet (DUV) photo annealing process for sol–gel based IGZO thin film on SWCNT random networks, the ambipolar transport of both electrons and holes with good electrical characteristics was realized. We also investigate the effect of DUV photo annealing on the material characteristics of solution-processed hybrid stack films and on the device performance of solution-processed hybrid ambipolar TFTs compared to those of samples thermally annealed at 500 °C, which is required for solution-processed high-quality IGZO thin films. The Raman spectra show that DUV photo annealing ensures hole transport in SWCNT random networks of a hybrid stack film, where the intensity of the 2D peak to the G peak was not changed compared to that of pristine SWCNT random networks. We believe that these analytical investigations reveal that DUV photo annealing is a promising method by which to realize hybrid ambipolar SWCNT/IGZO TFTs fabricated at low temperature.

Use of Nanoparticles for the Disinfection of Desalinated Water

When chemical disinfection is performed before or after desalination, a number of harmful compounds are formed. Thus, efforts have been directed toward developing alternative methods for water disinfection. In this study, seven nanoparticles (NPs) were evaluated for disinfecting water produced from reverse osmosis and multi-stage flash desalination plants. The tested NPs were silver, copper, silver-copper, zinc oxide, magnesium oxide, silicon dioxide, and carbon nanotubes. The antimicrobial activity of the NPs was investigated by batch studies in desalinated water samples spiked with E. coli, Enterobacter, Salmonella, and Enterococci. The Chick-Watson model was fitted to the inactivation data to evaluate the kinetic constant for each combination of NPs, water type, and indicator bacteria. The results indicated that silver and silver-copper NPs have the highest disinfection efficiency among the tested NPs. Among the bacteria, Enterobacter (strain TPC129) appears to be the most inactivated, while Enterococci (strain NCTC775) seems to be the least influenced by the NPs. Variations in the chemical characteristics of the tested water samples appeared to cause noticeable differences in the antibacterial efficacies of copper and magnesium oxide NPs, but not in those of the other NPs.

Enhanced Ultraviolet Photodetector Based on Mg-Doped ZnO Nanorods Films

Magnesium-doped zinc oxide (ZnO: Mg) nanorods and nanotubes films were prepared by hydrothermal method deposited on glass substrates. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL), and optical absorption spectroscopy (UV) were performed to characterize the prepared films. X-ray diffraction analysis showed a decrease in the lattice parameters of Mg doped ZnO NRs. The Photoluminescence of the undoped and Mg-doped ZnO NRs displayed a near band edge. At 10 V bias, the metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector performance of the Mg-doped ZnO prepared for various Mg concentrations of 0.0, 0.02, and 0.06 was investigated under radiation of 40μW/cm2 at the wavelengths of 365 and 385 nm UV light. The responsivity, detectivity and quantum efficiency of Mg-doped based on MSM detector were 0.118A/W, 1.0579*1012 and 40.05157 under UV of wavelength 365nm respectively.

Effect of silicon dioxide substrate on buckling behavior of Zinc Oxide nanotubes via size-dependent continuum theories

This paper aims to highlight the effect of SiO2 substrate on the buckling behavior of Zinc Oxide (ZnO) nanotube. ZnO nanotube is modeled in various length and diameter to show the effect of size on buckling loads. Silicon Dioxide (SiO2) is the material on which Zinc Oxide (ZnO) is grown and used as gas/chemical sensor. In present paper, SiO2 substrate is modeled as two parameters elastic layer. In order to consider the elastic substrate, Winkler and Pasternak foundation models are used. Different values of elastic foundation parameters are taken into consideration to see the effect of these parameters on buckling loads of Zinc Oxide (ZnO) nanowire. Additionally, to take the size effect into consideration on calculating buckling loads, nonlocal elasticity, surface elasticity, modified couple stress, modified strain gradient theories are used. Some benchmark results have been depicted. Some detailed results are also given and compared in figures and tables.

Two-Step Formation of Zno Nanotubes by Wet Oxidation and Selective Etching

Zinc oxide (ZnO) hierarchical structures composed of nanorods were grown by wet oxidation of etched zinc (Zn) foils in hot water at 90°C for 4 h. The ZnO nanorods having an average topmost diameter of 490 nm were then selectively etched in 0.5–4 M potassium chloride (KCl) solution at 80°C for 1–4 h to facilitate conversion to nanotubes. Well-formed ZnO nanotubes were obtained after immersion in 1 M KCl solution at 80°C for 3 h. However, increasing the etching time to 4 h resulted in the collapse of the structure. XRD analysis showed that the nanorods and nanotubes were highly crystalline with wurtzite structure.

Membrane Absorption Coupling Process for CO2 Capture: Application of Water-Based ZnO, TiO2, and Multi-Walled Carbon Nanotube Nanofluids

In this work, stable water-based zinc oxide (ZnO), titania (TiO2), and multi-walled carbon nanotube (MWCNT) nanofluids are prepared and examined as CO2 absorbents in a polypropylene hollow fiber membrane contactor. Different operating variables, such as liquid flow rate, gas flow rate, and concentration of nanoparticles, and their effects on CO2 molar flux are investigated. The long-term stability of nanofluids is monitored using ultraviolet–visible spectroscopy. Also, ζ-potential measurements and sediment photography are applied to confirm the results of nanofluid stability. Dynamic light scattering is used to determine the size distribution of dispersed nanoparticles. The results show that the increase in the nanoparticle concentration to 0.15 wt % has a favorable effect on CO2 absorption efficiency as a result of the increase in Brownian motion and other related mechanisms. However, it adversely affects the CO2 absorption by lowering the nanofluid stability at higher concentrations. The obtained result...

Fabrication of silver nanoparticles decorated zinc oxide nanotubes by electrodeposition technique for photoelectrochemical water splitting

In this study, ZnO nanotube arrays decorated with Ag nanoparticles are synthesized on the fluorine-doped tin oxide glass by using simple and cost-effective electrodeposition technique for investigating photoelectrochemical water splitting performance under visible light irradiation. The photocatalytic response of arrays for water splitting is studied using linear sweep voltammetry and electrochemical impedance spectroscopy. These arrays reveal remarkably enhanced performance in comparison with pure ZnO nanorods, ZnO nanotubes and ZnO nanorods decorated by Ag nanoparticles arrays, respectively. This improvement is attributed to reduce the band gap and charge recombination due to surface plasmon resonance effect of decorated Ag nanoparticles on ZnO nanotubes.

DFT study of Ni, Cu, Cd and Ag heavy metal atom adsorption onto the surface of the zinc-oxide nanotube and zinc-oxide graphene-like structure

In the current article, we investigated adsorption properties of Nickel (Ni), Copper (Cu), Cadmium (Cd) and silver (Ag) heavy metal atoms with zinc oxide (ZnO) nanotube and ZnO-graphene like structures sheet using Ab-initio based density functional theory (DFT) calculations. At first, both nanostructures were optimized and then most stable configuration, adsorption energy and equilibrium distance of each heavy metal with nanostructures were computed via DFT and the results were compared with each other. Our obtained results reveal that ZnO-nanotube had a better adsorbing behavior comparing to ZnO-graphene sheet case by case due to lower equilibrium distance and higher adsorption energy. This nanostructure created a strong binding with Ni, Cu and Ag but adsorption energy for Cd was clearly lower than others. Also, only Ni and Cu could have a chemisorption adsorption with the ZnO-graphene sheet and others showed a nearly weak physisorption adsorption with this nanostructure. The maximum adsorption energy for both ZnO-nanostructures occurred for nickel which were about −3.45 eV and −2.19 eV respectively. The minimum adsorption energy for ZnO nanotube occurred with Cd (−1.3 eV) while for ZnO-graphene sheet it occurred with Zn (−0.15 eV). In almost all items equilibrium distance decreased with increasing in adsorption energy. Moreover, we generated density of state (DOS) diagrams to investigate the electrical properties of studied structures.

Synthesis of zinc oxide nanorods or nanotubes on one side of a microcantilever.

Cantilevers are really promising sensitive sensors despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with zinc oxide (ZnO) nanorods or nanotubes having a diameter of approximately 100 nm and a length of 1 µm. The nanostructure growth was first optimized on a silicon wafer and then transferred to the cantilevers. The ZnO nanorods were grown in an autoclave. The centre of the nanorods was dissolved in order to obtain nanotubes. The dissolution conditions were optimized in order to have the longest etching depth. After 1.25 h in a dissolution solution containing 0.75 wt% of NH3(aq) and 0.75 wt% of cetyltrimethyl ammonium bromide, the longest etching depth was obtained. After the transfer of the syntheses to the cantilevers, nanorods/nanotubes grew on both sides of the cantilever, which prevents the reflection of the laser allowing the resonance frequency measurement. A masking procedure was developed in order to avoid the growth on one face of the cantilever of zinc oxide nanostructures. As far as the authors are concerned, for the first time, zinc oxide nanotubes were synthesized on only one face of cantilevers with optical readout.

Catalytic Ozonation in Arrayed Zinc Oxide Nanotubes as Highly Efficient Mini-Column Catalyst Reactors (MCRs): Augmentation of Hydroxyl Radical Exposure.

Reactor design is significant to catalytic ozonation for an efficient mass transfer and exposure of the powerful but short-lived hydroxyl radicals (HO•). Herein, five groups of zinc oxide nanotube arrays with pore sizes from 168 to 10 nm were produced as mini-column catalyst reactors (MCRs) for internal catalytic ozonation, whose performance was comparatively studied on the kinetics of ozone transfer, consumption, and radical probe interaction. Using an RCT value describing HO• exposure, all the MCRs with sufficient ozone transfer featured an RCT level of at least 3.2 × 10-6, which is substantially higher than most values in referenced works (10-9∼10-6) and that for microscale reactors in our work (∼10-8). Furthermore, the HO• exposure dramatically increased with diminishing pore size, causing an elevated RCT up to 8.0 × 10-5 for the smallest MCR with 10 nm pore. The interphase formed in this flow-through system might have enriched HO• radicals produced via surface, and for a smaller MCR, the effect would be greater with a more confined microfluidic region. Investigations on electron paramagnetic resonance and the treatment of ozone-recalcitrant organics corroborated the nanoscale effect of MCR on augmentation of HO• exposure. This study offers a new way to design nanotube reactors for internal HO•-based heterogeneous catalysis.

Preparation of nanocrystalline ZnO/CoxOy and CNT/CoxOy bilayers for photoabsorption potential: XPS and some surface structural characterization

Zinc oxide and carbon nanotubes (CNT) have been separately grown atop cobalt oxide (CoxOy) thin film to form bilayer structures. The structures were characterized by some surface probing techniques. Surface morphology shows that particles of the underlying CoxOy film are evenly distributed across substrate, its average size increases between 60 and 73 nm with deposition voltage. A transparent layer of ZnO completely laminated the CoxOy film in the first set of bilayer sample. Thickness of overgrown CNT on CoxOy is about 16 nm. Dispersion of CoxOy crystallites along the path of the adsorbed CNT was also observed. Optical studies indicated that both the CoxOy film and the ZnO/CoxOy bilayers are fairly transparent to visible light. Values of their energy band gap were estimated in the range between 2.0 and 2.14 eV. Photoemission and crystallographic studies revealed possible interaction between particles of CoxOy and ZnO films but not with the substrate. The study suggests that both the laminated II-VI bilayer and the CNT enhanced structures could be a recipe for effective charge harvesting and separation in nanostructured photovoltaic devices.

The effects of hybrid nano-powder of zinc oxide and multi walled carbon nanotubes on the thermal conductivity of an antifreeze

In the past decade, researchers have been focusing on new advanced nanofluids composed of different nanoparticles. This type of nanofluids, also referred to as hybrid nanofluids, is generally made of a combination of two different nanoparticles with a base fluid. Use of nanofluids leads to reduced production cost of metal-based nanofluids and/or carbon nanotubes. Carbon nanotubes cause magnificent thermophysical properties in nanofluids and, therefore, their addition to the base fluid can significantly affect the thermal conductivity in nanofluids. Addition of an oxide nanoparticle to carbon nanotubes or metal nanoparticles leads to their increased stability and improved suspension. This research aimed to experimentally investigate the effects of temperature and volume fraction of nanoparticles on the thermal conductivity of ZnO-MWCNT/EG-Water nanofluid. The experiments were conducted in a temperature range of 25–50°C on samples with volume fractions of 0.0375, 0.075, 0.15, 0.3, 0.6, and 1.2%. Measurements revealed that the thermal conductivity increased up to 30% by increasing the amount of nanoparticles and temperature. Finally, an experimental correlation was presented for prediction of thermal conductivity, and deviation of margin analysis was performed on the proposed correlation. The analyses results suggested a maximum deviation of margin of 1.46%, indicating an appropriate accuracy for the proposed correlations in prediction of thermal conductivity of ZnO-MWCNT/EG-Water nanofluid.

Electrospinning of composite microbeads for tribological improvements

Tribological properties of electrospun polymer-based microbeads dispersed in mineral oil were investigated. Microbeads composed of polyvinylpyrrolidone, zinc oxide and multi-walled carbon nanotubes (MWCNTs) were generated using an electrospinning apparatus. The influence of various electrospinning parameters such as voltage, injection rate and concentration were investigated. The friction reducing ability of microbeads enhanced lubricants were evaluated using a reciprocating tribometer system. In the tribometer, a hemispherical ruby counter surface was slid against an aluminum 6061 workpiece in the presence of a mineral oil-based lubricant. Friction was reduced by 13%–27% when the composite microbeads were emulsified in the base mineral oil. On average, the addition of 0.015 g/mL of composite microbeads reduced the wear scar depth by 53.7%, the wear volume by 50.1% and the wear coefficient by 35.4%.

A State-of-the-Art Review of Nanoparticles Application in Petroleum with a Focus on Enhanced Oil Recovery

Research on nanotechnology application in the oil and gas industry has been growing rapidly in the past decade, as evidenced by the number of scientific articles published in the field. With oil and gas reserves harder to find, access, and produce, the pursuit of more game-changing technologies that can address the challenges of the industry has stimulated this growth. Nanotechnology has the potential to revolutionize the petroleum industry both upstream and downstream, including exploration, drilling, production, and enhanced oil recovery (EOR), as well as refinery processes. It provides a wide range of alternatives for technologies and materials to be utilized in the petroleum industry. Nanoscale materials in various forms such as solid composites, complex fluids, and functional nanoparticle-fluid combinations are key to the new technological advances. This paper aims to provide a state-of-the-art review on the application of nanoparticles and technology in the petroleum industry, and focuses on enhanced oil recovery. We briefly summarize nanotechnology application in exploration and reservoir characterization, drilling and completion, production and stimulation, and refinery. Thereafter, this paper focuses on the application of nanoparticles in EOR. The different types of nanomaterials, e.g., silica, aluminum oxides, iron oxide, nickel oxide, titanium oxide, zinc oxide, zirconium oxide, polymers, and carbon nanotubes that have been studied in EOR are discussed with respect to their properties, their performance, advantages, and disadvantages. We then elaborate upon the parameters that will affect the performance of nanoparticles in EOR, and guidelines for promising recovery factors are emphasized. The mechanisms of the nanoparticles in the EOR processes are then underlined, such as wettability alteration, interfacial tension reduction, disjoining pressure, and viscosity control. The objective of this review is to present a wide range of knowledge and expertise related to the nanotechnology application in the petroleum industry in general, and the EOR process in particular. The challenges and future research directions for nano-EOR are pinpointed.

Performance studies of ZnO and multi walled carbon nanotubes-based counter electrodes with gel polymer electrolyte for dye-sensitized solar cell

Counter electrode (CE) is one of the major component which determine the energy conversion efficiency of the dye-sensitized solar cells (DSSCs). Here in, five types of CEs using two different materials were fabricated. Three types are zinc oxide (ZnO) based while other two are multi-walled carbon nanotubes based CEs. The thickness and resistance per cm2 of each CE were measured. The gel polymer electrolyte based on polyacrylonitrile polymer, sodium iodide salt, 1-Hexyl-3-methyl-imidazolium iodide ionic liquid was also prepared. The conductivity studies revealed that the highest ionic conductivity of gel polymer electrolyte was 6.72 mS cm−1 upon incorporation of 100 wt% 1-Hexyl-3-methyl-imidazolium iodide ionic liquid. This gel polymer electrolyte was sandwiched between commercial TiO2 photo-anode and different types of CE to fabricate the DSSCs. The J-V characteristic curves of the DSSCs were obtained and the DSSC characterization parameters were determined. The efficiencies achieved using ZnO and MWCNT-based CEs were ranging from 0.46% to 7.07%. The results demonstrate that ZnO and multi-walled carbon nanotubes are good candidates of CEs for DSSC application.

Synthesis and Electrochemical Properties of ZnO Nanotube Materials

Zinc oxide (ZnO) is one of the widely used metal oxide materials in industry. It is cheap and chemically stable. In addition, it has a wide bandgap (3.37 eV) and a high binding energy in a crystalline state (60 meV), which ensure efficient exciton emission. Based on these characteristics, ZnO has been applied from traditional industry such as white pigment and sunscreen to high technology industry that includes semiconductors, optical materials, conductive films, solar cells, biosensors, and light emitting diodes. Nanostructured ZnO materials can be synthesized by various methods such as hydrothermal, vapor deposition, and vapor-liquid-solid processes. The shapes of the nanostructure are rod, wire, tube, ring, spring, sheet, propeller, etc. These various nanostructures can be beneficial for enabling fast electronic and ionic transport in electrochemical energy storage device applications such as rechargeable batteries and supercapacitors. However, the low electronic conductivity of ZnO is still a problem when it is used as electrode materials for lithium rechargeable batteries. In the present work, carbon coated ZnO nanotube materials were formed by a simple one-pot synthesis method. Conventional ZnO nanotube structures have been synthesized by relatively complex methods and have usually grown on the substrates. Here, free-standing ZnO nanorod materials were prepared by a hydrothermal process and then they were transformed into nanotubes with simultaneous carbon-coating during annealing process. The ZnO nanotube structure is suitable for alleviating volume changes for Li insertion and extraction during cycling and carbon coating enables fast electronic transport with a buffering effect for volume changes of the active materials.

Vertical ZnO Nanotube Transistor on a Graphene Film for Flexible Inorganic Electronics.

The bottom-up integration of a 1D-2D hybrid semiconductor nanostructure into a vertical field-effect transistor (VFET) for use in flexible inorganic electronics is reported. Zinc oxide (ZnO) nanotubes on graphene film is used as an example. The VFET is fabricated by growing position- and dimension-controlled single crystal ZnO nanotubes vertically on a large graphene film. The graphene film, which acts as the substrate, provides a bottom electrical contact to the nanotubes. Due to the high quality of the single crystal ZnO nanotubes and the unique 1D device structure, the fabricated VFET exhibits excellent electrical characteristics. For example, it has a small subthreshold swing of 110 mV dec-1 , a high Imax /Imin ratio of 106 , and a transconductance of 170 nS µm-1 . The electrical characteristics of the nanotube VFETs are validated using 3D transport simulations. Furthermore, the nanotube VFETs fabricated on graphene films can be easily transferred onto flexible plastic substrates. The resulting components are reliable, exhibit high performance, and do not degrade significantly during testing.

Study of quantum confinement effects in ZnO nanostructures

Motivation to fact that zinc oxide nanowires and nanotubes with successful synthesis and the mechanism of formation, stability and electronic properties have been investigated; in this study the structural, electronic properties and quantum confinement effects of zinc oxide nanotubes and nanowires with different diameters are discussed. The calculations within density functional theory and the pseudo potential approximation are done. The electronic structure and energy gap for Armchair and zigzag ZnO nanotubes with a diameter of about 4 to 55 Angstrom and ZnO nanowires with a diameter range of 4 to 23 Å is calculated. The results revealed that due to the quantum confinement effects, by reducing the diameter of nanowires and nanotubes, the energy gap increases. Zinc oxide semiconductor nanostructures since having direct band gap with size-dependent and quantum confinement effect are recommended as an appropriate candidate for making nanoscale optoelectronic devices.