Journal of Nano Research Vol. 13

Abstract: In this study, the buoyancy-driven fluid flow and heat transfer in a differentially-heated rectangular cavity filled with the TiO₂-water nanofluid is investigated numerically. The left and the top walls of the cavity are maintained at constant temperatures T_h and T_c, respectively, with T_h > T_c. The enclosure’s right and bottom walls are kept insulated. The governing equations are discretized using the finite volume method. A proper upwinding scheme is employed to obtain stabilized solutions for high Rayleigh numbers. Using the developed code, a parametric study is undertaken, and the effects of pertinent parameters, such as, the Rayleigh number, the aspect ratio of the cavity and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that by increasing the volume fraction of the nanoparticles, the mean Nusselt number of the hot wall increases for the shallow cavities; while, the reverse trend occurs for the tall cavities. Moreover, the heat transfer enhancement utilizing nanofluid is more effective at Ra = 10³.

Abstract: Transparent conducting oxides (TCOs) are well known and have been widely used for a long time in optoelectronics industries. The most popular TCOs have n-type characteristics. However p-type material is not well established and examined. The delafossite-CuAlO₂ is one of the p-type TCOs. In this paper, amorphous Cu-Al-O films were deposited onto (100) p-type silicon substrate by magnetron sputtering. After that, the films were annealed at 800°C for 2 h in different partial oxygen levels ranging from 5*10^-5 to 1 atm with N₂, air, and O₂. X-ray diffraction patterns showed that as-deposited films were amorphous. In addition, delafossite-CuAlO₂ (R m and P6₃/mmc phase) appeared at 800°C in N₂, but monoclinic-CuO and spinel-CuAl₂O₄ phases existed in air and O2. The formation of delafossite-CuAlO₂ phase can be explained with thermodynamics. The optoelectronic properties of delafossite-CuAlO₂ films were also measured. The direct optical bandgap was around at 3.3 eV, which is comparable with literature data. The electrical conductivity was obtained to be 6.8*10^-3 S/cm. The hot-probe method employed to measure the electrical property of the films, which indicates that delafossite-CuAlO₂ films have p-type characteristics.

Abstract: The photoconductivity of a nanocomposite MEH-PPV:TiO₂ thin film is investigated. The nanocomposite MEH-PPV:TiO₂ thin film was deposited on a glass substrate by spin coating technique. The composition of the TiO₂ powder was varied from 5 wt% to 20 wt% (with 5 wt% interval). The concentration of the MEH-PPV is given by 1 mg/1 ml. The current voltage characteristics were measured in dark and under illumination. The photoconductivity showed increment in value as the composition of the TiO₂ is raised in the polymer based solution. The absorption showed augmentation as the amount of TiO₂ is increased. The escalation of the current voltage is then supported by the results of surface morphology.

Abstract: Electromagnetic (EM) waves are able to distinguish between water and hydrocarbons due to their high difference in resistivity value. The method that uses EM technology to explore hydrocarbon is called Seabed Logging (SBL). Due to high demand of hydrocarbons, improvement of this technology is needed. The paper consists of modelling of the prototype of EM transmitter and receiver for hydrocarbons exploration. EM transmitter consists of carbon nanotubes (CNT), aluminium wire with magnetic feeder in toroidal shape. ZnO-CNTs-PVDF composites are used for EM detection. The XRD analysis showed a clear diffraction peak of [101] plane at 36°C of the 2θ. Raman spectra were obtained for ZnO synthesised at 200°C and 300°C temperatures. The initial permeability, Q-factor and relative loss factor were measured using vector network analyser. Results show high value of Q-factor (~43) of the ZnO-CNTs at frequency between 20-30 MHz. The nanoparticles also show low relative loss factor for frequencies above 10 MHz. The grain size, morphology and shape of the particles were characterized using FESEM and revealed rod-like structures. The CNT dipole transmitter system using improved CNT dipole antenna and CNT-ZnO detector record an enhancement of 192% and can be used for hydrocarbon detection.

Abstract: The development of nanoscale materials for optical chemical sensing applications has emerged as one of the most important research areas of interest over the past decades. Nanomaterials exhibit highly tunable size- and shape-dependent chemical and physical properties, show unique surface chemistry, thermal and electrical properties, high surface area and large pore volume per mass unit area. Because of their unique and advantageous features they can help to improve sensitivity, response time and detection limit of sensors. In this review, recently developed photoluminescence-based optical chemical nanosensors are presented. Some future trends of the nanomaterial-based optical chemical sensors are given.