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Research and development of nano-sized Zinc Oxide (ZnO) has recently received great attention due to its remarkable properties such as large exciton binding energy of 60 meV, extraordinary photosensitivity, nontoxic nature, wide bandgap and the fact that it is a low cost material with many technological applications. The inherent necessity for stoichiometric ZnO nanostructures suggest that a deposition method where the film stoichiometry is controlled by a chemical reaction is unavoidable. Moreover, it is extremely important, when developing new methods for deposition of ZnO nanostructures to keep the deposition system as simple as possible, maximize throughput, and keep costs at a minimum. Modified aqueous chemical growth method offer such an opportunity. In this work, ZnO nano-petals on microscope glass substrates have been prepared by using a modified aqueous chemical growth method. On the other hand, before utilization of the fabricated ZnO nanostructures by any technique for any technological applications, it is essential to investigate morphological, optical, electrical and structural properties. In this work morphological, optical, electrical and structural properties with respect to change in deposition time have been cross examined using FESEM, UV-Vis spectroscopy, I-V properties by Keithley system and XRD respectively. SEM micrographs have revealed very little changes in the shape, orientations and distribution of ZnO nanopetals formed with change in deposition times. SEM micrographs have also revealed the growth pattern for the prepared ZnO nano-petals which proceeds via a nucleation, and coalescence of ZnO nuclei. XRD analysis have revealed that the synthesized ZnO nano-petals have a hexagonal Wurtzite ZnO structure with peaks at 2θ positions 31.7°, 34.4°, 36.2°, 47.4°, 56.5°and 62.7° belonging to the (100), (002), (101), (102), (110) and (103) planes respectively. UV-Vis spectroscopy has in the same way shown that the synthesized ZnO nano-petals have energy band gaps ranging from 3.46 eV to 3.65 eV. I-V measurements have disclosed that the ZnO nano-petals are conductive. Film resistivity values obtained from the I-V curves showed an exponential increase in resistivity with increased film thickness. Our method of preparation of ZnO nano-petals via a chemical assisted route can serve as benchmark for controlled synthesis of ZnO nanostructures for various technological applications.

The increasing energy consumption and its resultant CO2 emission in the built environment have revolutionized the housing design. Buildings are strategically designed to harness ambient weather factors for indoor space thermal conditioning and lighting. A comparison of the daylighting and potential environmental mitigations due to the lighting energy consumption in a passive solar and the conventional house was the aim of this study. Both houses used as a case study are in Alice, Eastern Cape in South Africa. The indoor illuminance of the homes was monitored using Li-Cor 210R photometric sensors. Between 07 h00 to 16 h30, the passive solar house’s average daylighting was 217 lux and 56 lux in the conventional house on a clear sky. Under the same sky condition, there was 47% lighting energy saving. This reduces the amount of coal usage by 1.97 kg, 3.53 kg of CO2, 14.80 g of NO2, and 4.76 L of water. In contrast, no energy savings were achieved in the conventional home. The equivalent environmental impacts due to 4.20 kg of coal usage were 7.52 kg of CO2, 31.52 g of NO2 emissions, and 10.14 L of water usage. From the findings, daylight harvest through passive solar design shows the potential of energy savings and environmental mitigation measures in the housing sector.

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