The present work highlights the facile synthesis of hydrophobic palm fatty acid functionalized Fe3O4 nanoparticles (MNP-FA) for the efficient removal of oils from the surface of water. An intense hydrophobic layer was introduced on the surface of Fe3O4 nanoparticles functionalized by the palm fatty acid obtained from the hydrolysis of palm olein. Scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), Energy dispersive X-ray spectroscopy (EDX) and water contact angle analysis (WCA) measurements were used to characterize the newly fabricated palm fatty acid adorned magnetic Fe3O4 nanoparticles (MNP-FA). The obtained results confirmed the successful synthesis of palm fatty acid-functionalized magnetic nanoparticles. Oil removal tests performed with MNP-FA revealed that this newly prepared material could selectively adsorb lubricating oil up to 3.5 times of the particles' weight while completely repelling water. The main parameters affecting the adsorption of oil i.e., sorption time, mass of sorbent and pH of water were optimized.
In this work, the direct electrochemistry of hemoglobin (Hb), which was immobilized on carbonyl functionalized single walled carbon nanotube (SWCNT) and deposited onto a gold (Au) electrode has been described. The synthesis of the network of crosslinked SWCNT/Hb was done with the help of crosslinking agent EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide). The UV-Vis and FTIR spectroscopy of SWCNT/Hb networks showed that Hb maintained its natural structure and kept good stability. In addition with this, scanning electron microscopy (SEM) illustrated that SWCNT/Hb networks had a featured layered structure and Hb being strongly liked with SWCNT surface. Cyclic voltammetry (CV) was used to study and to optimize the performance of the resulting modified electrode. The cyclic voltammetric (CV) responses of SWCNT/Hb networks in pH 7.0 exhibit prominent redox couple for the FeIII/II redox process with a midpoint potential of -0.46 V and -0.34, cathodic and anodic respectively. Furthermore, SWCNT/Hb networks are utilized for the detection of hydrogen peroxide (H2O2). Electrochemical measurements reveal that the resulting SWCNT/Hb electrodes display high electrocatalytic activity to H2O2 with high sensitivity, wide linear range, and low detection limit. Overall, the electrochemical results are due to excellent biocompatibility and excellent electron transport efficiency of CNT as well as high Hb loading and synergistic catalytic effect of the modified electrode toward H2O2.
Undoped and Mn2+ doped CoAl2O4 (MnxCo1-xAl2O4; x = 0.0 to 1.0) spinel nanoparticles were successfully synthesized by a microwave heating method using glycine as the fuel. X-ray powder diffraction (XRD) was confirmed the cubic spinel structure. The average crystallite size of the samples was found to be in the range of 16.46 nm to 20.25 nm calculated by Scherrer's formula. The nano-sized particle-like morphology of the samples was confirmed by high resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (HR-TEM) analysis. Energy dispersive X-ray (EDX) results showed the pure form of spinel aluminate structure. The band gap energy (Eg) of pure CoAl2O4 was estimated to be 3.68 eV from UV-Visible diffuse reflectance spectroscopy (DRS), and the Eg values increased with increase of Mn2+ ions, due to the smaller grain size. The magnetic hysteresis (M-H) loop showed the superparamagnetic nature, and the magnetization and coercivity values increased with increasing Mn2+ ions, which was confirmed by vibrating sample magnetometer (VSM). All compositions of the nano-catalysts were tested as catalyst successfully for the conversion of benzyl alcohol into benzaldehyde and observed good catalytic activity.
This study explores optimization of resistance load (R-Load) of four silicon nanowire transistor (SiNWT)-based static random-access memory (SRAM) cell. Noise margins and inflection voltage of butterfly characteristics with static power consumption of SRAM cell are used as limiting factors in this optimization. Range of R-Load used in this study was 20-1000 KΩ with Vdd = 1 V. Results indicate that optimization depends critically on resistance load value. The optimized range of R-Load is 100-200 KΩ.
Ni-doped cobalt aluminate NixCo1-xAl2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) spinel nanoparticles were successfully synthesized by a simple microwave combustion method using urea as the fuel and as well as reducing agent. X-ray powder diffraction (XRD) was confirmed the formation of single phase, cubic spinel cobalt-nickel aluminate structure without any other impurities. Average crystallite sizes of the samples were found to be in the range of 18.93 nm to 21.47 nm by Scherrer's formula. Fourier transform infrared (FT-IR) spectral analysis was confirmed the corresponding functional groups of the M-O, Al-O and M-Al-O (M = Co and Ni) bonds of spinel NixCo1-xAl2O4 structure. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images was confirmed the particle like nanostructured morphology. Energy band gap (Eg) value was calculated using UV-Visible diffuse reflectance spectra (DRS) and the Eg values increased with increasing Ni2+ dopant from x = 0.2 (3.58 eV) to x = 1.0 (4.15 eV). Vibrating sample magnetometer (VSM) measurements exposed that undoped and Ni-doped CoAl2O4 samples have superparamagnetic behavior and the magnetization (Ms) values were increased with increasing Ni2+ ions. Spinel NixCo1-xAl2O4 samples has been used for the catalytic oxidation of benzyl alcohol into benzaldehyde and was found that the sample Ni0.6Co0.4Al2O4 showed higher conversion 94.37% with 100% selectivity than other samples, which may be due to the smaller particle size and higher surface area.
In this study, performances of mesoporous Mo/Al2O3 catalysts prepared by sol-gel and post-hydrolysis methods in hydrocracking of atmospheric residual oil were compared. In addition, different methods: (i) the single step and (ii) conventional impregnation method to incorporate active metal over the mesoporous support were also investigated. For single step method, Mo/Al2O3 catalysts were synthesized directly by sol-gel and post-hydrolysis method. On the other hand, the impregnation method was a two step procedure which involved the production of alumina via sol-gel or post-hydrolysis method and followed by respective Mo impregnation. In general, mesoporous Mo/Al2O3 catalysts prepared by sol-gel method resulted in relatively higher surface area (> 400 m2/g) and large pore volume (- 0.8 cm3/g). Mo/Al2O3 catalysts prepared by sol-gel method exhibited higher hydrocracking activity as well. The Mo crystal size was found to relate directly with the hydrocracking result.
The utilization of carbon dioxide for the production of valuable chemicals via catalysts is one of the efficient ways to mitigate the greenhouse gases in the atmosphere. It is known that the carbon dioxide conversion and product yields are still low even if the reaction is operated at high pressure and temperature. The carbon dioxide utilization and conversion provides many challenges in exploring new concepts and opportunities for development of unique catalysts for the purpose of activating the carbon dioxide molecules. In this paper, the role of carbon-based nanocatalysts in the hydrogenation of carbon dioxide and direct synthesis of dimethyl carbonate from carbon dioxide and methanol are reviewed. The current catalytic results obtained with different carbon-based nanocatalysts systems are presented and how these materials contribute to the carbon dioxide conversion is explained. In addition, different strategies and preparation methods of nanometallic catalysts on various carbon supports are described to optimize the dispersion of metal nanoparticles and catalytic activity.
A detailed study on the surface properties of oleic acid-stabilized PtNi nanoparticles supported on silica is reported. The oleic acid-stabilized PtNi nanoparticles were synthesized using NaBH4 as the reducing agent at various temperatures and oleic acid concentrations, prior to incorporation onto the silica support. X-ray diffraction studies of the unsupported oleic acid-stabilized PtNi particles revealed that the PtNi existed as alloys. Upon incorporation onto silica support, surface properties of the catalysts were investigated using H2-temperature reduction (H2-TPR), H2-temperature desorption (H2-TPD) and H2-chemisorption techniques. It was found that for the bimetallic catalysts, no oxides or very little oxidation occurred. Furthermore, these catalysts exhibited both Pt and Ni active sites on its surface though the availability of Ni active sites was dominant. A comparison of the surface properties of these materials with those prepared without oleic acid in our previous work [N. H. H. Abu Bakar et al., J. Catal. 265, 63 (2009)] and how they affect the hydrogenation of benzene is also discussed.
Porous ZnO nanostructures have become the subject of research interest--due to their special structures with high surface to volume ratio that may produce peculiar properties for use in optoelectronics, sensing and catalysis applications. A microwave-assisted hydrothermal method has been used for effecting the formation of porous nanostructure of metaloxide materials, such as CoO and SnO2, in solution. Here, by adopting the unique performance of a microwave-assisted-hydrothermal method, we realized the formation of highly porous ZnO nanostructures directly on the substrate surface, instead of in solution. The effects of the ambient reaction conditions and the microwave power on the structural growth of the ZnO nanostructures were studied in detail. Two different ambient reaction conditions, namely refluxed and isolated in autoclave systems, were used in this work. Porous ZnO (PZO) nanostructures with networked-nanoflakes morphology is the typical result for this approach. It was found that the morphology of the ZnO nanostructures was strongly depended on the ambient conditions of the reaction; the isolated-autoclave system may produce reasonably high porous ZnO that is constituted by vertically oriented grainy-flakes structures, whereas the refluxed system produced solid vertically-oriented flake structures. The microwave power did not influence the structural growth of the ZnO. It was also found that both the ambient reaction conditions and the microwave power used influenced the crystallographic orientation of the PZO. For instance, PZO with dominant (002) Bragg plane could be obtained by using refluxed system, whereas PZO with dominant (101) plane could be realized if using isolated system. For the case of microwave power, the crystallographic orientation of PZO prepared using both systems changed from dominant (002) to (101) planes if the power was increased. The mechanism for the formation of porous ZnO nanostructures using the present approach is proposed. The ZnO nanostructures prepared using the present method should find an extensive use in currently existing application due to its property of reasonably high porosity.
The present study deals with surface modification of Ti6Al4V alloy via anodization technique. The morphology, structure, adhesion and bioactivity of Ti6Al4V alloy after anodization process were investigated in detail. The influence of fluoride content and direct circuit (DC) applied voltage during anodization of Ti6Al4V alloy in a bath with electrolytes composed of ethylene glycol (EG) and ammonium fluoride (NH4F) were considered. It was found that the average pore sizes and length of nanoporous or nanotubes were increasing with the fluoride content and applied voltage. A minimum of 3 wt% of NH4F is required to grow a self-organized nanotube arrays. As the fluoride content was increased to 5 wt%, TiO2 nanotubes with average diameter of 110 nm and 3.4 microm lengths were successfully synthesized. It is noteworthy to point out that the rate of the nanotube formation was increasing up to 9 microm thick bioactive TiO2 nanotubes layer as anodization time was increased to 3 h. Based on the results obtained, the PA6 cells cultured on anodic Ti6Al4V alloy showed highest level of cell viability and greater cell adhesion compared to the flat Ti6Al4V foil substrate. In fact, highly ordered nanotubes structure on Ti6Al4V alloy can provide beneficial effects for PA6 cells in attachment and proliferation.
This study is the first to demonstrate dimensional optimization of nanowire-complementary metal-oxide-semiconductor inverter. Noise margins and inflection voltage of transfer characteristics are used as limiting factors in this optimization. Results indicate that optimization depends on both dimensions ratio and digital voltage level (Vdd). Diameter optimization reveals that when Vdd increases, the optimized value of (Dp/Dn) decreases. Channel length optimization results show that when Vdd increases, the optimized value of Ln decreases and that of (Lp/Ln) increases. Dimension ratio optimization reveals that when Vdd increases, the optimized value of Kp/Kn decreases, and silicon nanowire transistor with suitable dimensions (higher Dp and Ln with lower Lp and Dn) can be fabricated.
This paper addresses the growth of nano-structured MgZnO thin films by sol-gel spin coating method which will be used as a template layer to grow carbon nanotubes. The nano-structured MgZnO films were deposited on platinized (100) silicon substrates. In this work, we focused on the effect of aging and Mg content on the film structure and resistivity. Sols with Mg content of 10, 30 and 50 at.% were subjected to aging times of between 3 to 240 hours. Results from scanning (SEM) and field emission scanning electron (FESEM) microscopes and surface profiler (SP) showed that the sol aging increased the thickness, grain size and surface roughness for aging up to 240 hours. The energy dispersive analysis by X-ray (EDAX) confirmed the element of Mg in the ZnO films. The electrical resistivity also increased with aging time as confirmed by four point probe method. The results suggest that appropriate aging of the sol is important for improving physical quality and electrical performance of MgZnO thin films derived from sol-gel technique.
Electromagnetic (EM) waves transmitted by Horizontal Electric Dipole (HED) source to detect contrasts in subsurface resistivity termed Seabed Logging (SBL) is now an established method for hydrocarbon exploration. However, currently used EM wave detectors for SBL have several challenges including the sensitivity and its bulk size. This work exploits the benefit of superconductor technology in developing a magnetometer termed Superconducting Quantum Interference Device (SQUID) which can potentially be used for SBL. A SQUID magnetometer was fabricated using hexagon shape-niobium wire with YBa2Cu37O, (YBCO) as a barrier. The YBa2Cu37O, samples were synthesized by sol-gel method and were sintered using a furnace and conventional microwave oven. The YBCO gel was dried at 120 degrees C in air for 72 hours. It was then ground and divided into 12 parts. Four samples were sintered at 750 degrees C, 850 degrees C, 900 degrees C, and 950 degrees C for 12 hours in a furnace to find the optimum temperature. The other eight samples were sintered in a microwave with 1100 Watt (W) with a different sintering time, 5, 15, 45 minutes, 1 hour, 1 hour 15 minutes, 1 hour 30 minutes, 1 hour 45 minutes and 2 hours. A DEWAR container was designed and fabricated using fiberglass material. It was filled with liquid nitrogen (LN2) to ensure the superconducting state of the magnetometer. XRD results showed that the optimum sintering temperature for the formation of orthorhombic Y-123 phase was at 950 degrees C with the crystallite size of 67 nm. The morphology results from Field Emission Scanning Electron Microscopy (FESEM) showed that the grains had formed a rod shape with an average diameter of 60 nm. The fabricated SQUID magnetometer was able to show an increment of approximately 249% in the intensity of the EM waves when the source receiver offset was one meter apart.
In this study, Single-Walled and Multi-Walled Carbon Nanotubes in their perfect forms were investigated by the Finite Element Method. Details on the modeling of the structure are provided in this paper, including the appropriate elements, the element properties that should be defined based on the atomic structure of Carbon Nanotubes and the corresponding chemical bonds. Non-covalent van der Waals interactions between two neighbor atoms as well as the required approximations for the modeling of the structures with this kind of interaction are also presented. Specific attention was dedicated to the necessity of using some time- and energy-consuming steps in the simulation process. First, the effect of simulating only a single ring of the whole structure is studied to find out if it would represent the same mechanical behavior as the long structure. Results show that by applying an appropriate set of boundary conditions, the stiffness of the shortened structure is practically equal to the long perfect structure. Furthermore, Multi-Walled Carbon Nanotube structures with and without defining the van der Waals force are studied. Based on the observations, applying the van der Waals force does not significantly influence the obtained Young's modulus of the structure in the case of a uniaxial tensile test.
Magnetic nanoparticles in the hollow region of carbon nanotubes have attraction due to their changing physical electrical and magnetic properties. Nickel zinc ferrite plays an important role in many applications due to its superior magnetic properties. Ni0.8Zn0.2Fe2O4 single crystals were encapsulated in multiwall carbon nanotubes (MWCNTs). The magnetic nano crystals were prepared using a sol-gel self combustion method at the sintering temperature of 750 degrees C and were characterized by XRD, FESEM, TEM and VSM. Initial permeability, Q-factor and relative loss factor were measured by impedance vector network analyzer. XRD patterns were used for the phase identification. FESEM images show morphology and dimensions of the grains of Ni0.8Zn0.2Fe2O4 single crystals and Ni0.8Zn0.2Fe2O4 single crystals in MWCNTs. TEM images were used to investigate single crystal and encapsulation of Ni0.8Zn0.2Fe2O4 single crystals in the MWCNTs. VSM results confirmed super paramagnetic behaviour of encapsulated Ni0.8Zn0.2Fe2O4 single crystals. It was also attributed that encapsulated Ni0.8Zn0.2Fe2O4 single crystals in MWCNTs showed a higher initial permeability (51.608), Q-factor (67.069), and low loss factor (0.0002) as compared to Ni0.8Zn0.2Fe2O4 single crystals. The new encapsulated Ni0.8Zn0.2Fe2O4 single crystals in the MWCNTs may have potential applications in electronic and medical industries.
In seabed logging the magnitude of electromagnetic (EM) waves for the detection of a hydrocarbon reservoir in the marine environment is very important. Having a strong EM source for exploration target 4000 m below the sea floor is a very challenging task. A new carbon nanotubes (CNT) fibres/aluminium based EM transmitter is developed and NiZn ferrite as magnetic feeders was used in a scaled tank to evaluate the presence of oil. Resistive scaled tank experiments with a scale factor of 2000 were carried out. X-ray Diffraction (XRD), Raman Spectroscopy and Field Emission Scanning Electron Microscope (FESEM) were done to characterize the synthesized magnetic feeders. Single phase Ni0.76Mg0.04Zn0.2Fe2O4, obtained by the sol-gel method and sintered at 700 degrees C in air, has a [311] major peak. FESEM results show nanoparticles with average diameters of 17-45 nm. Samples which have a high Q-factor (approximately 50) was used as magnetic feeders for the EM transmitter. The magnitude of the EM waves of this new EM transmitter increases up to 400%. A curve fitting method using MATLAB software was done to evaluate the performance of the new EM transmitter. The correlation value with CNT fibres/aluminium-NiZnFe2O4 base transmitter shows a 152.5% increase of the magnetic field strength in the presence of oil. Modelling of the scale tank which replicates the marine environment was done using the Finite Element Method (FEM). In conclusion, FEM was able to delineate the presence of oil with greater magnitude of E-field (16.89%) and the B field (4.20%) due to the new EM transmitter.
This paper presents the temperature characteristics of silicon nanowire transistors (SiNWTs) and examines the effect of temperature on transfer characteristics, threshold voltage, I(ON)/I(OFF) ratio, drain-induced barrier lowering (DIBL), and sub-threshold swing (SS). The (MuGFET) simulation tool was used to investigate the temperature characteristics of a transistor. The findings reveal the negative effect of higher working temperature on the use of SiNWTs in electronic circuits, such as digital circuits and amplifiers circuits, because of the lower I(ON)/I(OFF) ratio, higher DIBL, and higher SS at higher temperature. Moreover, the ON state is the optimum condition for using a transistor as a temperature nano-sensor.
We report the use of a new precursor as active agents to promote the growth of carbon nanotubes (CNT) in methane ambient using a simple thermal chemical vapour deposition method. The agents consist of ammonia and methanol mixed at different ratios and was found to enhance the growth of CNTs. The optimum methanol to ammonia ratio was found to be 8 to 5, whereby longer and denser CNTs were produced compared to other ratios. The result was found otherwise when the experiment was done solely in methane ambient. In addition, CNT growth on substrates coated with double layer Ni catalyst was improved in terms of quality and density compared to a single coated substrates. This finding is supported by Raman spectrometry analysis.
Transparent nanostructured ZnO thin films were successfully deposited using sol-gel spin coating method on a quartz substrate. The 0.4 M ZnO solution gel was prepared using zinc acetate dihydrate (Zn(CH3COO)22H2O) as the precursor, 2-methoxyethanol as the solvent and monoethanolamine (MEA) as the stabilizer. The electrical and optical properties dependencies on the annealing temperature of the nanostructured ZnO thin films were investigated. It was found that as the annealing temperature increased, the particle size, conductivity and the peak of the UV emission also increased.
This paper shows the effect of the dimensions of nanowires on threshold voltage, ON/OFF current ratio, and sub-threshold slope. These parameters are critical factors of the characteristics of silicon nanowire transistors. The MuGFET simulation tool was used to investigate the characteristics of a transistor. Current-voltage characteristics with different dimensions were simulated. Results show that long nanowires with low diameter and oxide thickness tend to have the best transistor characteristics.