Sharif Digital Repository

This study deals with an experimental investigation on the thermal performance of a mechanical wet cooling tower with counter flow arrangement by using multi-walled carbon nanotubes (MWNTs) and nanoporous graphene nanofluids. Stable nanofluids were prepared through two-step procedure by using water with properties taken from a working cooling tower in the South of Iran. Zeta potential revealed suitable stability of MWNTs and nanoporous graphene nanofluids. Thermal and rheological properties of the nanofluids were investigated. It was found that thermal conductivity increases by 20% and 16% at 45°C for MWNTs and nanoporous graphene nanofluids, respectively. The increase in density and... 

A simple platform based on a hairpin oligonucleotide switch and multi-walled carbon nanotubes (MWCNTs) for the ultrasensitive detection of specific DNA sequences has been developed. In this approach, the π-stacking interaction of single-strand DNA-MWCNT was employed to construct an electrochemical DNA biosensor. Changes to the surface conductivity, based on the MWCNT replacement, were monitored by using the electrochemical species [Fe(CN)6]3-/4- as a redox probe. Morphological and voltammetric characterizations of the electrode surface were performed using atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV), differential pulse voltammetry (DPV) and... 

The main aim of the present study was to enhance the degradation capacity of Acid Blue 92 (AB92) by visible-light-active Ag3PO4 nanocomposites based on g-C3N4 and Multiwalled Carbon Nanotubes (MWCNTs). The nanocomposites were fabricated through a tunable in situ deposition method. The properties of the resulting samples were investigated by X-ray diffraction, scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The photocatalytic activity results revealed that the Ag3PO4/g-C3N4 heterojunction inorganic/organic composite exhibited an improvement in both efficiency and the rate of AB92 photodegradation in comparison with the others. The enhanced photocatalytic... 

We report a new facile strategy to enhance the efficiency of TiO2 dye-sensitized solar cells (DSSCs) using Nb-doped TiO2 photoelectrodes with carbon nanotube-derived TiO2 nanotubes (CDTs). Multi-walled carbon nanotubes (CNTs) with an average diameter of 80 nm are used as the template to produce CDTs through facile sol-gel and oxidation processes at 600 °C. Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analyses reveal that the synthesized CDTs have a uniform thickness of 60-120 nm and a crystallite size of 17 nm. We prepare Nb-doped TiO2 nanoparticles with different atomic ratios of 0-4 at% Nb and test them as photo-electrodes to investigate the doping... 

Liquid phase hydro-purification of crude terephthalic acid (CTA) was performed using supported Pd and Pd-Sn catalysts on functionalized multi-wall carbon nanotubes (FMWCNT). Pd/FMWCNT catalysts were prepared by wet impregnation with Pd loadings of 0.05 to 0.6 wt.%. Pd-Sn/FMWCNT catalysts were prepared by co-impregnation (CI) and successive impregnation (SI) using 0.3 wt.% Pd loading and Sn/Pd molar ratios of 0.1 and 0.35 for the CI method and 0.05 to 0.35 for the SI method. Pd loading of 0.3 wt.% for Pd/FMWCNT was sufficient to decrease the 4-carboxybenzaldehyde (4-CBA) content of CTA from 2100 ppm to 5.5 ppm without excessive hydrogenation of terephthalic acid (TA). The commercial catalyst... 

In this research, multi-walled carbon nanotubes (MWCNTs) were modified by dendritic macromonomer. Herein, polyamidoamine with acrylamide end groups was incorporated on MWCNTs. Afterwards, poly(N-isopropylacrylamide), (PNIPAM), was grafted on polyamidoamine in a facile synthesis. Then, doxorubicin as anticancer drug was loaded on this nanocarrier. The drug release was studied at below and above the lower critical solution temperature of PNIPAM, (LCST 32 °C), 27 °C and 37 °C, respectively. At 37 °C (body temperature) the polymer shell dehydrated and the drug release increased. The profile of drug release was expressed by Higuchi's equation which indicated that the drug release mechanism was... 

In this paper, using the continuum approximation together with Lennard-Jones potential, a new semi-analytical expression is given to evaluate the van der Waals interaction between two single-walled carbon nanotubes. Based on this expression, two new formulations are also proposed to model multi-walled carbon nanotubes. In the first one, the interactions between each pair of shells from the inner and outer tubes are summed up over all of the pairs, whereas in the second formulation, a set of correction factors are applied to convert the results of double-walled carbon nanotubes to the correlated multi-walled ones. With respect to the present formulations, extensive studies on the variations... 

Polycaprolactone-polylactide block copolymers (PCL-block-PLA) were grafted onto filled multi-wall carbon nanotubes (MWCNT) successfully. In this synthesis, MWCNTs were opened and functionalized, and then they were filled by silver nanoparticles. The filled MWCNT were used as macroinitiator for ring opening polymerization of ε-caprolactone and L-lactide. Then the end hydroxyl functional groups of MWCNT-graft-PCL or MWCNT-graft-PLA were used as initiator for ring opening polymerization of lactide and ε-caprolactone and MWCNT-graft-PCL-block-PLA or MWCNT-graft-PLA-block-PCL were obtained, respectively. Length of grafted copolymer chains onto the MWCNT was controlled using CNT/monomer ratio.... 

Abstract: The electrodeposition of platinum nanoparticles (PtNPs) on multiwall carbon nanotubes (MWCNTs)/fluorine-doped tin oxide glass (FTO) was investigated. Nucleation and growth mechanisms were studied via Scharifker and Hills model. Chronoamperometry results clearly show that the electrodeposition processes are diffusion-controlled and the diffusion coefficient is 1.5×10-5cm2/s. The semi-spherical particles with lamellar morphology were observed in 1M H 2SO 4, while a petal shape was discerned in 0.5M H 2SO 4. Also, dispersion, size, and uniformity of PtNPs were investigated, where the finer distribution of PtNPs with the average size less than 100 nm was obtained in 0.5M H 2SO 4... 

In this article, a continuum-based constitutive model is developed to predict the mechanical behavior of 5052 resin epoxy reinforced by multiwalled carbon nanotubes (MWCNTs) based on experimentally generated data. For this purpose, MWCNTs/epoxy specimens with various percentages of functionalized and nonfunctionalized MWCNTs are prepared. The SEM graphs indicate that functionalization leads to a better bound between epoxy and MWCNTs and a higher level of dispersion. The specimens are then tested under standard ASTM D638-02 a procedure and their true plastic stress–strain curves are extracted. Investigations on experimentally generated data reveal that a wt% dependent equation which is... 

In this work, the adsorption of benzoic acid (BA) over metal organic framework of chromium-benzenedicarboxylates (MIL-101) is reported for the first time. The influences of pH, contact time, initial concentration, and temperature of BA solution on the adsorption behavior were investigated. The Langmuir adsorption isotherm was adequate to represent the experimental data (R2 > 0.99) and the adsorption kinetics was well-represented by a pseudo-second order kinetic model (R2 > 0.96). The zeta potential of MIL-101 decreased with increasing pH confirming the importance of electrostatic interactions between MIL-101 and BA as well as the importance of the large pore volume (1.32 m3/g) and large... 

Biodegradable acrylate-terminated polyurethane/acrylate (APUA) filled with 2-hydroxyethyl methacrylate functionalized carbon nanotube (CNT-HEMA) was prepared by in situ free radical crosslinking. CNT-HEMA enhanced crystallinity of soft domain and caused more phase separation between hard and soft domains of APUA. Tensile testing showed a considerable improvement in elastic modulus (∼160%) and tensile strength (∼30%) at 1 wt% loading. Morphological features of APUA induced by nanotubes were found to be dominant on mechanical properties of APUA/CNT-HEMA. CNT-HEMA increased water contact angle of APUA; however, wettability of APUA/CNT-HEMA maintained in acceptable range for biomedical... 

Sol-gel technique was used to coat multiwall carbon nanotubes (MWCNTs) with anatase titania to increasing the surface area and improve the photocatalytic activity of TiO2. Room temperature ballistic conduct of MWCNT combined with semiconducting behavior of anatase brought about a photocatalytic improvement of ∼37 % with respect to the highest methyl orange decolorization flair. For characterization and photocatalytic efficiency determination, X-ray diffraction (XRD), field emission (FE) scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS) and ultraviolet visible (UV-vis) spectroscopy were rehearsed. Attachment of anatase... 

Ultrafine-grained Al-CNT (2 and 4 vol%) composites were successfully fabricated using the flake powder metallurgy and hot pressing route, and the microstructure and tribological properties of the produced composites were studied. The results showed that the coefficient of friction and the wear rate of Al decrease with the addition of the CNT reinforcement. A carbon-rich film formed on the worn surfaces during wear test, which prevented the Al oxidation and yielded the self-lubricating effect for the composites. This improvement in the wear behavior of the composites can be attributed to the simultaneous effects of the ultrafine-grained matrix and strengthening and self-lubricating properties... 

The present paper describes a voltammetric sensor based on glassy carbon electrode (GCE) modified with a thin film of multi-walled carbon nanotubes (MWCNTs) coated with an electro-polymerized layer of titan yellow-doped over–oxidized polypyrrole (OPPY) for the determination of tizanidine (TIZ). A significant enhancement was observed in the anodic peak current of TIZ on the surface of OPPY/CNT/GCE, relative to the bare, CNT- and OPPY-coated GCEs. The microscopic structure and surface morphology of the composite film was thoroughly characterized by means of atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. The effect of various... 

Biodegradable acrylate-terminated polyurethane/acrylate (APUA) filled with 2-hydroxyethyl methacrylate functionalized carbon nanotube (CNT-HEMA) was prepared by in situ free radical crosslinking. CNT-HEMA enhanced crystallinity of soft domain and caused more phase separation between hard and soft domains of APUA. Tensile testing showed a considerable improvement in elastic modulus (∼160%) and tensile strength (∼30%) at 1 wt% loading. Morphological features of APUA induced by nanotubes were found to be dominant on mechanical properties of APUA/CNT-HEMA. CNT-HEMA increased water contact angle of APUA; however, wettability of APUA/CNT-HEMA maintained in acceptable range for biomedical... 

Supportless Ni-Pd-0.1CNT foamy nanocatalyst with specific surface area of 611.3 m2/g was produced by electroless deposition of nickel, palladium and multiwall carbon nanotube (MWCNT) on interim polyurethane substrate. Application of temperature programmed reduction (TPR) and temperature programmed oxidation (TPO) data into Kissinger (Redhead) kinetic model showed lessening of their activation energies due to Pd and CNT addition. Presence of foamy Ni/SiC caused 8% higher steam reforming of methane; while Ni-Pd-0.1CNT presence resulted in 22% higher methane conversion. The catalytic behavior of the samples was described by morphological and compositional studies which were carried out by... 

Core-Shell structures of Ag@Pt Nanoparticles (NPs) dispersed on different carbon base supports such as Graphene Oxide (GO), Multiwall Carbon Nanotubes (MWCNT) and Carbon black (CB) Vulcan applied to the oxygen reduction reaction (ORR) in a Proton Exchange Membrane Fuel Cell (PEMFC). Electrocatalysts synthesized through the ultrasonic treatment method. The morphology of as prepared materials characterized through the High Resolution Transmission Electron Microscopy (HRTEM) and X-ray diffraction (XRD) analyses. The ORR activities and stabilities of electrocatalysts studied through electrochemical measurements of Cyclic Voltammetry (CV) and single cell tests, respectively. Results revealed all... 

In this review, the importance of nanoparticles (NPs), with emphasis on their general and specific properties, especially the high surface-to-volume ratio (A/V), in many technological and industrial applications is studied. Some physical and chemical preparation methods for growing several metallic and binary alloy NP catalysts are reviewed. The growth and mechanism of catalytic reactions for synthesis of 1D nanostructures such as ZnO nanowires and multiwall carbon nanotubes (MWCNTs) are discussed. Gas-phase production with emphasis on dependence of catalytic activity and selectivity on size, shape and structure of NPs is also investigated. Application of NP catalysts in several... 

A chemically modified carbon-paste electrode (CPE) is prepared by incorporating congo red (CR) immobilized on multi-walled carbon nanotube (MWCNT). The results show that CR is effectively immobilized on the surface of MWCNT under the ultrasonic agitation in aqueous solution and further incorporating the nafion. The prepared electrode, due to the electrostatic repulsions between the CR and ascorbate anion, is capable to mask the response of the ascorbic acid (AA) completely and provide an effective method for the detection of minor amounts of uric acid (UA) in the presence of high concentrations of AA. On the other hand, an increase in the microscopic area of the electrode by addition of...