International Journal Of Nanoscience and Nanotechnology
Volume:11 Issue: 1, Winter 2015

Nanocomposites of multi-walled carbon nanotubes and titanium dioxide (MWCNT/TiO2) were synthesized by the sol-gel method. Regarding hydrophobicity of carbon nanotubes (CNTs), benzyl alcohol was used as the linking agent between CNT powder and TiO2 gel which was prepared from the precursor of titanium tetraisopropoxide. The prepared samples were treated under thermal treatments. A part of the samples was heated to prepare MWCNT/TiO2 nanocomposite with anatase TiO2 and the other parts were heated until burning CNTs and prepare pseudo-tube TiO2 (PT-TiO2). The aterials were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), Brunauer-Emmet-Teller (BET) measurement and UV-vis diffuse reflectance spectra (DRS). The hotocatalytic activity of MWCNT/TiO2 nd PT-TiO2 was studied for degradation of acetaldehyde under UV-visible and visible light irradiation. The Photocatalytic reaction was examined in a gaseous stirred flow reactor equipped with 80W Hg lamp and the concentration–time results were compared with commercial TiO2 (P25-TiO2). Considerable reduction of acetaldehyde concentration was achieved under visible irradiation by the MWCNT/TiO2 nanocomposite, whereas none of the PT-TiO2 and typical P25-TiO2 showed activity under visible light. An optimal fraction of 30 wt% MWCNT in anatase TiO2 was found to have the highest activity under visible light irradiation.

To date, the effects of nanoparticles on woody plants remain unaddressed. This study reveals some of the physiological and biochemical effects of SiO2 nanoparticles on wild pear seedlings. The seedlings were irrigated with different concentrations of nano silica (0, 10, 100, 500 and 1000 mg/l) for 14 days. Nanoparticle adsorption and absorption, biomass allocation, gas exchange, relative water content, xylem water potential, electrolyte leakage, pigment and proline content, antioxidant enzymes, and nutrient cycles were surveyed. The attachment of nanoparticles on the root surface was observed by scanning electron microscopic and the accumulation of Si in leaves was measured by X-ray fluorescence analysis. Although the performed experiments did not show any acute toxic effects of adding of SiO2 nanoparticles in irrigation to wild pear plant, the finding should be confirmed with other experiments of longer duration and high exposure concentrations before a final conclusion in this issue can be made.

Nanotechnology involves the ability to see and control individual atoms and molecules which are about 100 nanometer or smaller. One of the major tools used in this field is atomic force microscopy which uses a wealth of techniques to measure the topography and investigates the surface forces in nanoscale. Friction force is the representation of the surface interaction between two surfaces and surface topology. In order to have more precise nano-manipulation, friction models must be developed. In this study a sensitivity analysis has been conducted for nano-manipulation of nanoparticles toward dimensional and environmental parameters based on Coulomb and Hurtado and Kim (HK) friction models using Sobol method. Previously graphical sensitivity analysis has been used for this target in which the percentage of importance of parameters is not taken into account. But in Sobol method as a statistical model this problem is solved. Results show that cantilever thickness is the most effective dimensional parameter on critical force value while cantilever length and width are of less importance. Environmental parameters such as cantilever elasticity modulus, substrate velocity and adhesion, respectively, take next orders.

The aim of this paper is to enhance thermal performance of a microchannel heat sink by using nanoencapsulated phase change material (NEPCM) slurry as a cooling fluid instead of pure fluid. A threedimensional model of a circular channel using water slurry of NEPCM was developed. The results show a significant reduction in the mean fluid temperature along the channel and heat sink wall temperature under certain conditions for heat flux rates that depend on the NEPCM-slurry volume fraction and slurry inlet velocity. Lower temperatures across the electronic device can be attained at high heat flux compared with using water as the only cooling fluid.

In this report, magnetic iron oxide nanoparticles were synthesized via coprecipitation of Fe2+ and Fe3+ with ammonium hydroxide, and the surface of synthesized nanoparticles was organically functionalized by commercially available amine coupling agent namely, 3-aminopropyl trimethoxysilane (APTS) by using well-known sol–gel method. Further reaction of the synthesized Fe3O4@APTS core-shell magnetite nanoparticles with 2-Chloropyridine via nucleophilic aromatic mechanism in position 2 led to the target molecule Fe3O4@APTS/ 2-Chloropyridine. All prepared materials e.g the magnetite iron oxide, Fe3O4@APTS nanoparticles as well as organically coated Fe3O4@APTS/ 2-Chloropyridine magnetite particles were characterized using Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). SEM images showed that the Fe3O4@APTS/ 2-Chloropyridine nanoparticles were roughly spherical with average size of 45-55 nm. FTIR indicated the formation of a layer of APTS-Py on the surface of the Fe3O4 magnetite core. Thermogravimetric analysis of the coated APTS-Py on the Fe3O4 surface revealed that 8 % of organic materials coated on iron oxide nanoparticles.

In this paper, the effects of adding nanoparticles including Tio2 to a fluid media for purpose of free convection heat transfer improvement were analyzed. The free convection was assumed to be in laminar flow regime and the solutions and calculations were all done by the integral method. Water, as a Newtonian fluid, was considered the base fluid (water) and all the thermo physical properties of the nano-fluids have been considered unvarying. According to the calculations performed and all depicted graphs, one can thoroughly consider that adding nanoparticles to the fluid generally causes increment and development of heat transfer coefficient. Increasing nanoparticles concentration increases the heat transfer rate. The heat transfer increment is also dependent on the nanoparticles thermal onductivity and the viscosity theory used. In this study, four different kinds of theories were used for the nano-fluids viscosity calculations. The effects of viscosity on the nano-fluids thermal conductivity can be obviously seen. All the calculations have been done for the concentrations lower than 4%.

Glassy carbon (GC) is the most commonly used carbon-based electrode in the analytical laboratory. Because of the high background current and low electrode response, modification of this electrode can be done by various materials and techniques. An ionic liquid (IL), 1-methyl-3-(3-trimethoxysilyl propyl) imidazoliumbis (trifluoromethylsulfonyl) imide, was covalently cross linked onto the GC surface. GC was activated in sulfuric acid solution by cyclic voltammetry, which generate surface oxygen containing functional groups such as OH group, through which the IL was covalently bonded the surface of GC. The resulting surface was characterized by using cyclic voltammetry, differential pulse voltammetry and atomic force microscopy. Hydroquinone and ascorbic acid were the redox systems used to study the effect of ILcovalent bonding on the electron transfer rate and response decay of the GC. Compared to GC modified with a physically adsorbed layer of IL with an unstable response and decrease in peak current, the chemically IL-modified electrode showed stable and favorable response characteristics.

Nanofluids are colloidal suspension of nanoparticles in a base fluid and have superior thermal properties in comparison to their base fluids. Novel properties of nanofluids are yet to be explored to the highest potential. Currently extensive investigation has been done on thermal conductivity of metallic and oxide nanofluids. Composites offer the advantage of tailor made properties and fluids with nano composite can offer tunable thermal conductivities.The present work deals with investigation on thermal conductivity of Cu2O-TiO2 nanocomposites with water as base fluid using Maxwell model for different volume fractions of anophase. The thermal conductivity variation is analyzed with respect to olume fraction of each phase of the nanocomposite.also by varying volume fraction of the individual phase of anocomposites. The highest thermal conductivity was obtained for the Cu2O-TiO2 (1:9) with water as base fluid. The results depend on the shape of Cu 2O-TiO2, viscosity of nanofluid, interfacial layer thickness and size of nanoparticle due to the constraints in Maxell thermal conductivity equation.