Electrospun ZnO was deposited on a glass substrate from zinc acetate dihydrate (Zn(CH 3 COO) 2 .2H 2 O) with polyvinyl acetate (PVAc) polymer dissolved in N, N, dimethyl formamide (DMF) and annealed in the presence of oxygen until organic molecules were decomposed. The resultant fibre was characterized using scanning electron microscope with energy dispersive spectrophotometry (SEMEDS), Fourier transform infrared (FTIR), and Rutherford backscattering spectroscopy (RBS). SEMEDS and FTIR exhibited a total decomposition of the organic precursor. The mean fibre width was found to be 260 nm, and fibre thickness was measured at 460 nm. XRD patterns indicate that ZnO was corundum with the hexagonal wurtzite structure. The crystallite size was determined by the Debye formula to be 54 nm. The optical analysis indicated that the percentage transmittance increased after calcination. The material band gap for this electrospun ZnO fibre was found to be 3.28 eV. The material optical parameters such as dispersion energy, average oscillator strength, and single oscillator strength were also calculated. The optical conductivity and dielectric plot demonstrated that the material conductivity and dielectric properties increase with increasing photon energy and increase sharply around the material energy bandgap. The Urbach tail analysis of the materials shows that they obey the Urbach rule. Therefore, the n-type electrospun ZnO fibre high refractive index is attributable to the presence of excess oxygen.

This work investigated the quality of signal strength coverage of the existing Digital Terrestrial Television (DTTV) operator in Nigeria using Startimes Ibadan as a case study. Signal strength and altitude data at different locations within a 40km radius of the Startimes transmitting station were measured to determine the quality of signal strength reception of Startime's digital television in Ibadan metropolis. A signal analyzer, a 10-meter cable, Yaggi external antenna and Global Positioning System (GPS) were used for the measurements at various locations in Ibadan within 40km radius distance of Startimes based station at Agodi in Ibadan. The city was grouped into six different zones for proper signal testing and efficient data collation. Parameters such as signal strength, distance, altitude, signal to noise ratio, modulation error rate, pre-bit error rate and post-bit-error rate were measured and recorded. The effects of distance and altitude were analyzed. It was observed from the result that there is a direct relationship between power level and altitude. In addition, there is an inverse relationship between power level and distance.

No abstract

Many metal oxide heterostructures have been synthesized as mixed oxides or layered structures for photocatalytic, photodegradation of pollutants and light-harvesting applications. However, in the layered structures the effects of interfacial properties and composition have largely not been explored. Hence, the effects of interfacial mixing and diffusion of sandwiched thin CuO layer on optical absorption of as-deposited and heat-treated multi-layered structured SnO2/CuO/SnO2 films were studied. The RBS analysis of the as-deposited films showed the presence of a minute amount of Cu in the surface and bottom SnO2 layers of the structure. We attributed this to inhomogeneous layer thickness evidenced by very low Sn/Cu atoms ratio of the CuO layer. However, the thermal treatment of the layered structure led to pronounced interlayer mixing and consequent formation of SnO2-CuO solid solutions throughout the layered structure. The layer integrity of the inserted CuO of the as-deposited films was very high and the as-deposited structure was far more optically absorbing. However, the annealed structure showed lesser optical absorption because of the onset of interfacial mixing and improved crystallization. This reflected in the optical bandgap variations of the as-deposited and annealed multilayered structures. The significance of this result is that the multi-layered films possess band narrowing – evidence of increased photon absorption - making it a better candidate than pure SnO2 oxide for photocatalysis, photodegradation and photodetection applications. It also pointed to the fact that attention must be paid to effects of heat treatments or annealing when inserting an absorbing layer into a photocatalyst or a material meant for photodegradation or any light-harvesting material.

The quest for improved visible light absorption in ZnO-based photocatalysts and photodetectors is a prevailing research problem. One method of solving this problem is by narrowing the band gap of this material well into the range of visible light energy. In this work, we have demonstrated considerable band narrowing into the visible region in our electrospun ternary ZnO-Zn 2 SnO 4 nanofibres. We also showed that band narrowing is highly dependent on the amount of Sn in the synthesized composite which could be attributed to the creation of localized states in the ZnO band and the attendant structural changes. However, beyond 15%wt doping there were observed changes in the trend of the bandgap reduction, crystallite sizes, and width of the localized states in the ternary ZnO-Zn 2 SnO 4 band. The details of experimental procedures and discussion of results have been included in this paper.

The use of carbon nanotubes (CNT) for fabrication of sensors and biosensors has increased considerably over the past decade. This review covers the progress and advances made during the years (2014-2018) in the utilisation of carbon nanotubes for fabrication of electrochemical biosensors. The focus of the review is on reported CNT-based biosensors for detection of, important substances, such as glucose, H2O2, (DNA), ascorbic acid, uric acid, dopamine, metal ions, and pesticides. The review starts by first discussing the structures and properties of CNTs, followed by discussion of some of the synthetic methods for CNTs preparation. The working principles and performances of CNT-based biosensors are then discussed. Considerations for future developments in CNT-based biosensors are also outlined.

The effects of CuO on the optical and dielectric properties of SnO2 thin film were studied to achieve improved light photon absorption and conversion. The films were deposited using airblast chemical spray pyrolysis. Rutherford Backscattering Spectrometric analysis using the Windows SIMNRA software gave the compositions of as-deposited and annealed films and their thicknesses. The optical and dielectric parameters were evaluated from the transmittance data obtained from UV – Visible spectrophotometer. The optical band gap of as-deposited SnO2-CuO film was evaluated to be 3.4 eV. The value of Urbach tail width of the as-deposited mixed oxide is higher (296 meV) compared to that of the annealed (252 meV) indicating the presence of more disordered states in the as-deposited film. The analysis also showed that the presence of CuO in the matrix of SnO2 led to a decrease in optical bandgap, refractive index, and by extension dielectric constants of SnO2. Our investigation led to the conclusion that the addition of CuO into SnO2 increased its electromagnetic photon absorption and also delay its speed thereby enhancing photon interaction with free charge carriers in the mixed oxide film. We opined that the mixed oxide will perform better in photocatalysis, photodegradation of pollutants and other lightharvesting applications since the CuO inclusion has extended its absorption edge towards the visible light range.

An analysis of measured global solar radiation (GR) in Osogbo (7.77oN, 4.57oE, 288m) is presented in the form of hourly average, monthly average and percentage frequency distribution. The experimental data corresponds to a year data of 2017. The results reveal that the monthly average values of daily total radiation exhibit seasonal variation with maximum value in dry season month of March (16.59MJ/m2) and minimum value in wet season month of August (8.98 MJ/m2). The annual average GR value is 14.20 MJ/m2 while the annual cumulative GR is 5122 MJ/m2. The solar radiation climate of Osogbo has also been compared to those reported for a number of locations. The percentage frequency of days possessing irradiation rate greater than 15 MJ/m2 is 14 percent whereas that possessing less than 10 MJ/m2 is 61 percent. We conclude, based upon the above analysis that Osogbo is characterized by relatively low global solar radiation.