Nanotechnology

Synthesis of a nanocomposite hydrogel P-PAMPS-PAAm/ZnO, has been made by the polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and acrylamide (AAm) in the presence of pectin (P) and zinc oxide (ZnO) using microwave irradiation technique. FTIR, XRD, SEM and TEM studies indicated the formation of a gel network and incorporation of ZnO particles within gel structure. The system was evaluated for adsorption of Cu (II) and Pb(II) ions from aqueous solutions. About 77 mgg-1 of Cu(II) and 125 mgg-1 of Pb(II) could be adsorbed from aqueous solutions. Different isotherm models have been employed to study the adsorption process and the data is found to fit well with Langmuir isotherm model. The kinetic studies revealed a second-order adsorption process. About 95% of the metal ions adsorbed could be stripped in acidic medium of pH 1.2 indicating the reusability of the gel.

Mechanical properties of seven types of Ag - clay nano films were investigated. Elasticity of Modulus, Tensile Strength, Toughness, Elongation at break, Tear Strength and color of nano films were compared with those of the regular Low Density Poly Ethylene film. Results showed that inclusion of nano particles increased Modulus of Elasticity, Tensile Strength and Tear Strength but Elongation at break point and toughness of the films were decreased. The effect of film type on Modulus of Elasticity, Tensile Stress and Tear Strength, were significant at the 0.01 level and for Elongation at break point and toughness was significant at the 0.05 level. Investigation of film color parameters and ?E showed that the 1000 ppm nano Ag film has more color than other films. The smallest ?E was related to the control film. ?E value of the nano Ag films increased with increasing nano particle content and in nano composite films, decreased with increasing clay content. In sum, the nano film with 1000 ppm nano Ag content was the best film and control film was the worst film. In conclusion, the nano composite film (SC3) with 500 ppm nano Ag- 450 ppm nano clay content was the best film in terms of the mechanical properties.

Zinc oxide nanostructure were successfully synthesized by chemical method and deposited on Al2O3 substrate using PLD. XRD analysis demonstrated that the ZnO nanostructure has a wurtzite structure with orientation of (002). SEM results indicated that by increasing the calcined temperature, the dimension of the ZnO nanostructure increases. The optimum temperature for synthesizing high density ZnO nanostructure was determined to be 1250 K. Room temperature PL spectra of the ZnO nanostructure showed a strong UV emission peak located at around 380 nm and a relatively weak green emission at around 540 nm, confirming that the as-grown nanorods possess good optical properties. The sensitivity of zinc oxide NRs films to 50 ppm vapor NO2 gas as a function of working temperature with different doping.

The thermal evaporation system type (Edwards) has been used to evaporate high purity (99.9 %) silver on glass substrates at room temperature under low pressure (about 10-6 torr) for different thickness (50, 75, 100, 125 and 150) nm. Using a rapid thermal oxidation (RTO) of Ag film at oxidation temperature 350 oC and different oxidation times, Ag2O thin film was prepared. The optical properties of Ag2O film were investigated and compared with other published results. The gas response behaviors of the p-Ag2O/PSi/c-Si – based gas sensor to H2 gas were investigated. The film gas response dependence on the temperature and test gas concentration was tested.

In this paper, we present the concept demonstrating some of the possibilities of nanotechnologies might enable in the future communication devices. Nanotechnology aloows control of physical problem of nanostructures and devices with single molecule precision. The device is build by numerous nano-transistors. This device is used for sensing toxicity of the materials. The devices constructed by nanotechnology can be stretched and folded to desired length since it has the strength of spider silk. As the transistors are temperature dependent, the devices are auto-chargeable when exposed to sunlight (solar energy). Nanoscale electronics are invisible to human eye, the devices are transparent.

Precious metals doped anatase titanium dioxide nanoparticles are used in various applications including environmental photocatalysis and solar cells. In this work we present the synthesis of Au- doped and Pt-doped TiO2 nanoparticles employing sol-gel methodology. The doping procedures based either on UV photodeposition (UV-PD). The morphology, composition, particle size and specific surface area of these synthesized nanoparticles have been characterized using several instrumental techniques namely, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDXS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Brunauer–Emmett–Teller (BET) theory. Au impregnated (2%) nano anatase TiO2 powder was examined in photo decolourization of Orange G as dye environmental pollutant under visible light illumination and optimum operational conditions.

The electron density and charge transport studies of organic field effect transistors (OFETs) based 2-phenyl-3Hpyrrole molecule have been calculated from the quantum chemical and DFT methods. Density functional theory calculations with B3LYP/aug-cc-PVDZ basis sets was used to determine ground state gas space molecular geometries (bond lengths and bond angles), electron density and bonding features of this molecule. The electron densities at the bond critical point (BCP) of aromatic Car–Car bonds are much stronger than the other bonds in the molecule. The calculated HOMO and LUMO energies is ~5.50 eV [B3LYP/aug-cc-PVDZ], this shows that charge transfer occurs within the molecule. The HOMO–LUMO gap calculated from quantum chemical calculations has been compared with the value calculated from the density of states. The negative electrostatic potential (ESP) is concentrated solely around the N atoms, whereas in the rest of the region a positive ESP to dominate.

Porous Silicon (PS) layers were prepared by electrochemical etching in a single-tank cell on the surface of single-crystalline p-type (100) silicon wafers, using hydrofluoric acid (HF) and ethanol (C2H5OH) in the volume ratio of 1:2. The surface and cross-section morphologies of the PS were observed from images obtained using Scanning Electron Microscope (SEM). Likewise, the porosity of the PS sample was determined using the parameters obtained from SEM images by geometrical method. SEM images indicated that, the pores were surrounded by a thick columnar network of silicon walls. This porous silicon layer can be considered as a sponge like structure. The X-ray diffraction (XRD) pattern showed the growth of PS layer on silicon wafer and the grain size of the PS layer was found to be around 60.2 nm. The effective refractive index of porous silicon was calculated using Effective Medium Approximation (EMA) analysis. The optical properties of PS were investigated using Fourier Transform Infrared (FTIR) spectroscopy and Photoluminescence (PL). The surface chemical bonds of the PS were observed by FTIR and the band gap of the PS sample was obtained from PL spectra. The efficiency of ethanol gas sensing properties of PS was investigated at room temperature. The sensor was found to operate with maximum efficiency at a concentration of 100 ppm hence, this PS material can be used as an effective sensor element to detect ethanol vapour.

The titanium dioxide powder was prepared on p-type porous silicon by sol-gel process. The morphology of TiO2 sensing film surface was imaged by atomic force microscope (AFM) model AA3000 SPM from Angstrom Advanced Inc. The average roughness of the film surface is 25 nm. The X-ray diffraction (XRD) patterns shows of TiO2nano-particalprepared by the solgel method arepolycrystalline, the anatase phase with the preferential orientation of the crystallites along the [101] direction,at2? =25.253°theresultisinagreementwiththe ASTM Card (PDF 21-1272).The resistance of the TiO2nano-partical sensors reduces with the presence of vapor ethanol.

Gold nanoparticles have been synthesized and they have been made to self assemble on indium tin oxide (ITO) coated with 3-mercaptopropyltrimethoxysilane. An aqueous solution of gold chloride was added to tetraoctyl ammonium bromide dissolved in toluene. The mixture was stirred well. Then an aqueous solution of sodiumborohydride was added and the mixture was stirred for 4 hours at room temperature. The organic phase was washed with water in a separating funnel. The solvent was removed by evaporating the solution in vacuum to get a black solid. The black solid was suspended in ethanol and kept under refrigeration overnight. The residue was filtered and washed thoroughly with ethanol. The residue was dried. The gold nanoparticles produced were characterized by Transmission Electron Microscope (TEM). A clean indium titanium oxide electrode was prepared. It was immersed in an aqueous solution containing potassium ferro cyanide and sodium chloride solution in a three electrode cell assembly. Saturated calomel electrode was used as reference electrode. A platinum foil was used as counter electrode. Cyclic voltammogram was recorded in the potential range of -0.1v to 0.5v at a sweep rate of 50mV/s. The experiment was repeated with the ITO electrode coated with 3-mercaptopropytrimethoxysilane. It was seen from the cyclic voltammogram that the redox peaks were absent and there was decrease in the current. This suggests the formation of MPTMS monolayer which acts as a barrier. Since the redox probe has to diffuse through the monolayer, the redox current decreased compared to the bare ITO. When ITO electrode modified with MPTMS was immersed in gold nanoparticles self assembled on the monolayer of MPTMS. The gold nanoparticles were attached to the –SH groups of MPMS. When CV was run with this electrode, there was increase in redox current suggesting that the GNPs have assembled on ITO electrode modified with MPTMS. These electrodes may find application in Biosensors.