Sharif Digital Repository

Rather vertically aligned ZnO rods with flower-like structures were grown on quartz substrates through vapor phase transport method. X-ray diffraction (XRD) analysis and photoluminescence (PL) measurement were performed to determine crystalline structure and defects, respectively. H2S gas sensing properties of the grown structure were investigated at both room temperature and 250 °C for comparison. A remarkable increase in response and selectivity at room temperature compared to 250 °C was observed. High response and selectivity to low concentrations of H2S at room temperature as well as good stability make the sensor a promising candidate for practical applications  

A series of tests were carried out to study the unsteady wake behaviour behind an aerofoil which is a section of a wind-turbine blade. The model is oscillated in pitch about its quarter chord axis at various reduced frequencies, amplitudes, and mean angles-of-attack. Instantaneous and mean velocity profiles were obtained using total and static pressure at 35 vertically aligned points behind the aerofoil via two similar rakes. The rakes were located at a distance of 1.5 chord length behind the model. An estimation of the real time and average variations of the linear momentum deficit during the oscillation cycle is obtained and has been compared with the corresponding static data. The results... 

For the rapid detection of hyperglycemia in human blood, we adopted a facile and two-step electrochemical procedure to prepare nickel/reduced graphene oxide (rGO) hybrid electrodes in the framework of a three-dimensional (3D) nanostructure. High-density and vertically-aligned nickel submicrorods with an average diameter of 155 ± 15 nm and a length of 7 ± 1 μm (an aspect ratio of about 40-50) were prepared by template-mediated electrochemical deposition techniques. Networks of rGO nanosheets between the rod-shaped arrays were formed by the cathodic electrophoretic deposition method. The synergistic effect of nickel morphology (planar and high-density rod-shaped arrays) and graphene oxide... 

This study reports the successful fabrication of high-performance flexible binder-free lithium-ion battery anode and supercapacitor based on the synthesis of 3D hierarchical MnO2 nanoflakes (NFs) on vertically aligned carbon nanotubes (VACNTs) grown upon stainless steel (SS). The experimental results revealed that the prepared electrodes were well served as supercapacitors with a tremendous specific capacitance of MnO2 NFs VACNT/SS 1131 F/g at 0.25 A/g in 0.5 mol.L−1 Na2SO4, 518.8% more than VACNT/SS (218 F/g). Compared to other MnO2 NFs/CNT composites, as-fabricated binder-free MnO2 NFs/VACNTs electrode achieves outstanding performance with high initial discharge and charge capacities of... 

This study reports the successful fabrication of high-performance flexible binder-free lithium-ion battery anode and supercapacitor based on the synthesis of 3D hierarchical MnO2 nanoflakes (NFs) on vertically aligned carbon nanotubes (VACNTs) grown upon stainless steel (SS). The experimental results revealed that the prepared electrodes were well served as supercapacitors with a tremendous specific capacitance of MnO2 NFs VACNT/SS 1131 F/g at 0.25 A/g in 0.5 mol.L−1 Na2SO4, 518.8% more than VACNT/SS (218 F/g). Compared to other MnO2 NFs/CNT composites, as-fabricated binder-free MnO2 NFs/VACNTs electrode achieves outstanding performance with high initial discharge and charge capacities of... 

In this report, the fabrication of vertically aligned carbon nanotube nanoelectrode array (VACNT-NEA) by photolithography method is presented. Electrochemical impedance spectroscopy as well as cyclic voltammetry was performed to characterize the arrays with respect to different diffusion regimes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion. The fabricated VACNT-NEA and high density VACNTs were employed as electrochemical glutamate biosensors. Glutamate dehydrogenase is covalently attached to the tip of CNTs. The voltammetric biosensor, based on high density VACNTs, exhibits a sensitivity of 0.976 mA mM-1 cm-2 in the... 

Ruthenium oxide was coated on multiwalled carbon nanotubes (MWCNTs) to obtain nanocomposite electrode which has a good response to the pH. To synthesize this electrode, gold and cobalt were coated on a stainless steel 304 substrates, respectively, and then, vertically aligned carbon nanotubes were grown on the prepared substrates by chemical vapor deposition. Gold reduced activity of the stainless steel, while cobalt served as a catalyst for growth of the carbon nanotube. Ruthenium oxide was then coated on MWCNTs via sol-gel method. At last, different techniques were used to characterize the properties of synthesized electrode including scanning electron microscopy (SEM), transmission... 

Optimizing highway alignment requires a versatile set of cost functions and an efficient search method to achieve the best design. Because of numerous highway design considerations, this issue is classified as a constrained problem. Moreover, because of the infinite number of possible solutions for the problem and the continuous search space, highway alignment optimization is a complex problem. In this study, a customized particle swarm optimization algorithm was used to search for a near-optimal highway alignment, which is a compound of several tangents, consisting of circular (for horizontal design) and parabolic (for vertical alignment) curves. The selected highway alignment should meet... 

Vertically aligned multi-wall carbon nanotube (CNT) arrays were fabricated in tip-growth mode on Ni/Si substrates using plasma enhanced chemical vapor deposition. In a purification process including hydrogenation and acid washing of the Ni/CNTs, the oxygen-containing functional groups were substantially reduced and a wide hollow core at the tip of the CNTs was formed by removing the Ni seeds. Sol-gel silver nanoparticles were deposited on the surface of the unpurified Ni/CNTs, while they could also be embedded within the hollow core of the Ni-removed CNTs. The persistency of the silver ions in the Ni-removed Ag-CNTs in comparison to the release of the silver ions from the Ag-Ni/CNTs in a... 

Local photodegradation of graphene oxide sheets at the tip of ZnO nanorods was used to achieve semiconducting graphene nanomeshes. The chemically exfoliated graphene oxide sheets, with a thickness of ∼0.9 nm, were deposited on quartz substrates. Vertically aligned ZnO nanorod arrays with diameters of 140 nm and lengths of <1 μm were grown on a glass substrate by using a hydrothermal method. The graphene oxide sheets were physically attached to the tip of the ZnO nanorods by assembling the sheets on the nanorods. UV-assisted photodegradation of the graphene oxide sheets (with dimension of ∼5 × 5 μm) at a contact place with the ZnO nanorods resulted in graphene nanomeshes with a pore size of... 

Large-scale K-doped ZnO nanotapers were successfully grown on an indium tin oxide (ITO) substrate using a facile electrochemical route. The structural and morphologic analysis exhibited that the K-doped ZnO nanostructures had a nanotaper morphology and strong preferential [0001] c-axis direction with a hexagonal polycrystalline structure. The optical results show that the incorporation of K+ ions as the donors in a ZnO lattice leads to substantial modulation of the band gap structure of ZnO nanotapers, which results in a redshift in the ultraviolet emission peaks. The considerable enhancement of performance in K-doped ZnO-based dye-sensitized solar cells (DSSCs) can be related to the doping... 

Here, controlled growth of vertically aligned carbon nanotubes (VACNTs) on free-standing porous activated reduced graphene oxide (a-rGO) paper was fabricated using plasma-enhanced chemical vapor deposition method. The electrochemical performance of prepared film was investigated to provide effective electrode for 3D flexible high-performance lithium-ion batteries (LIBs) and supercapacitors. The results revealed that the prepared electrode exhibited a high specific capacitance of 347 F/g at 0.5 A/g in 1 M KOH electrolyte, 60% more than non-activated rGO-paper (218 F/g). The VACNTs on a-rGO have increased the accessible surface area and acted as efficient electrical conducting paths, which... 

A sensitive glutamate biosensor is prepared based on glutamate dehydrogenase/vertically aligned carbon nanotubes (GLDH, VACNTs). Vertically aligned carbon nanotubes were grown on a silicon substrate by direct current plasma enhanced chemical vapor deposition (DC-PECVD) method. The electrochemical behavior of the synthesized VACNTs was investigated by cyclic voltammetry and electrochemical impedance spectroscopic methods. Glutamate dehydrogenase covalently attached on tip of VACNTs. The electrochemical performance of the electrode for detection of glutamate was investigated by cyclic and differential pulse voltammetry. Differential pulse voltammetric determinations of glutamate are performed... 

TiO2/multi-wall carbon nanotube (MWNT) heterojunction arrays were synthesized and immobilized on Si(0 0 1) substrate as photocatalysts for inactivation of Escherichia coli bacteria. The vertically aligned MWNT arrays were grown on ∼5 nm Ni thin film deposited on the Si by using plasma enhanced chemical vapor deposition at 650 °C. Then, the MWNTs were coated by TiO2 using dip-coating sol-gel method. Post annealing of the TiO2/MWNTs at 400 °C resulted in crystallization of the TiO2 coating and formation of Ti-C and Ti-O-C carbonaceous bonds at the heterojunction. The visible light-induced photoinactivation of the bacteria increased from MWNTs to TiO2 to TiO2/MWNTs, in which the bacteria could... 

Abstract : Vertically aligned carbon nanotube (CNT) arrays were synthesized by thermal chemical vapor deposition (CVD) on stainless steel substrates coated by cobalt nanoparticles as catalyst. Morphological and elemental analyses conducted by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that bamboo-like CNTs were blocked by Co nanoparticles at the tips. The fabricated nanotubes underwent functionalization by electrochemical oxidation in sulfuric acid, and the subsequent structural studies, as well as Fourier transform infrared (FTIR) spectroscopy confirmed that the tips of functionalized CNTs were opened while oxygenated functional groups were...