Current Nanomaterials - Volume 3, Issue 1, 2018

Nanostructure based energy storage devices with high surface area and conductivity are challenging requirements, which are extensively focused in the past few years. Recently, the nanostructures synthesis by microwave energy has become an increasingly popular theme among the scientific community to fulfill the energy storage demands at commercial scale. Since, microwave heating has reduced reaction times and side reactions with increased product yields and purity as compared to conventional heating methods. The high product yield is favorable at the industrial level, which is not possible by other synthesis techniques. On the other hand, supercapacitors have wide future applications, such as replacement of Li-Ion batteries due to cost effectiveness, high shelf-life and stable cycle life. Among various types of supercapacitors NiO has shown comparable supercapacitance to RuO2. A comprehensive overview of all synthesis techniques and reported supercapacitance results in comparison with microwave-assisted synthesis of NiO nanostructures are provided in this review article.

Metal oxides have attracted growing interest due to their large scale properties and application in various fields. These oxides have exhibited remarkable electrochemical properties. They are not only cheap, friendly to use, easy to synthesize but also are presenting better energy storage efficiency in response to the existing pure metal oxide materials. In this review, we shall try to focus on the importance of energy storage devices, their importance in the current circumstances. This review also includes an introduction about mixed metal oxides and their synthesis using various techniques. Moreover, a simple comparison also has been given. Similarly, an effort also has been made to explain which technique is more beneficial and cost effective presently and similarly ensure green synthesis. Finally, an effort has been made to highlight the applications of these mixed metal oxides in the modern energy storage devices.

Background: ZnO is well-known for its versatile applications in the semiconductor industry. The recently discovered polymorphs of ZnO are, therefore, attracting significant research and commercial interest to further extend their applications to modern technological devices and gadgets. Method: Using density functional theory based full potential linearized-augmented-plane-wave-pluslocal- orbital method, we performed calculations for the electronic and optical properties of various polymorphs of ZnO. The modified Becke-Johnson exchange potential and generalized gradient approximation by Perdew et al. are used for the treatment of exchange-correlation energy in the pursuit of the present calculations. Results: The band-structure results revealed them wide band gap semiconductors with band gap amounting to 2.99eV, 3.20eV, 2.86eV and 3.38eV for Sphalerite, GeP, NiAs and β-BeO type structured ZnO, respectively. Among them, Sphalerite, NiAs and β-BeO type polymorphs of ZnO exhibited direct band gap, whereas the band-gap of GeP-type ZnO was found to be of indirect nature. Conclusion: These polymorphs of ZnO exhibit interesting electronic and optical properties and are likely important for applications in optoelectronic devices. We believe that this study will contribute as an important reference for the applications of the different polymorphs of ZnO in designing electronic and optoelectronic devices.

Objective: Alleviate heat stress in wheat plants using nanotechnology technique. Method: Two consecutive seasons were held in El Wadi El Gadeed governorate, Egypt (a hot climate area) and two cultivars were used, Sids1 (heat tolerant) and Gimmeza7 (heat sensitive). The nanoparticles used were Zn NPs (80 nm) and Fe NPs (50 nm) which were used with several concentrations (0, 0.25, 0.50, 0.75, 1.0 and 10ppm). Results: Some concentrations from NPs achieved the best survival of wheat plants under heat stress conditions and this was done through enhancing some biochemical markers. There was an enhancing effect of NPs (highest mean value was observed at 10 ppm Zn NPs and 0.25 ppm Fe NPs) on yield quantity by Gimmeza7 cultivar. The enhancing effect of such NPs was related to increasing antioxidant enzymes activities (Glutathione S transferase, superoxide dismutase, peroxidase and catalase), the appearance of new bands in some isozymes and decreasing of lipid peroxidation product malondialdehyde. Conclusion: In this work, preparation of biocompatible metal based and well-characterized nanoparticles succeeded in stimulation of wheat plants to tolerate heat stress condition in El Wadi El Gadeed, Egypt.

Background: Owing to their lightweight and excellent specific mechanical properties, the utilization of magnesium-based materials promises the desired weight/energy savings in demanding applications. In the recent years, the addition of ceramic reinforcements to magnesium is being extensively researched due to their potential to replace the commercial alloys for structural applications. Method: One of the major limitations of Mg-based materials (alloys and nanocomposites) targeting aerospace/ high-temperature applications is its poor ignition resistance. In this regard, an attempt is made in this study to develop and characterize the properties of a new Mg / 0.5, 1, 1.5, 2 CaO nanocomposite system in terms of the ignition resistance. Further, microstructural and mechanical properties are also studied to understand the overall effect of CaO addition. The Mg/CaO nanocomposites required for this study were developed using disintegrated melt deposition method followed by hot extrusion. Results: Microstructural investigation showed significant grain refinement and the presence of Mg2Ca phase along with CaO particles. Evaluation of mechanical properties revealed significant improvements as compared to pure magnesium. Evaluation of ignition properties revealed excellent improvements in ignition temperature relative to magnesium as well as novel and commercial magnesiumbased alloys. The result of this investigation may be useful in further studies in the development of Mg/CaO nanocomposites for future commercial utilization, especially in the aviation, automotive and electronics industries.

Background: We report on the fabrication and characterization of Zinc Oxide (ZnO) and Zinc Oxide Graphene (ZnO-G) composites via a simple chemical route-polyol process, using zinc nitrate hexahydrate, ethylene glycol and reduced graphene oxide (RGO) as the precursors. The ZnO-G composites exhibit significantly enhanced photoluminescence, which is ~ 8 times stronger than that of ZnO samples. Such improved optical property is attributed to the contribution of plasmonic effect of graphene in ZnO-G. Moreover, the high crystalline quality ZnO-G composites hold great potential for dyesensitized solar cell (DSSC) applications. Method: Graphite oxide (GO) was synthesized using modified hummers method. RGO was then synthesized from GO by using hydrazine hydrate as a reducing agent. Results: The short-circuit current density was increased in the ZnOG solar cell compared to that of bare ZnO device, which is around 1.930 mA/cm2 and 0.308 mA/cm2 respectively. The conversion efficiency of the ZnO-G DSSC was measured as 0.438%, which is ~ 7 times higher than that of ZnO DSSC. The enhanced conversion efficiency achieved in ZnO-G DSSC resulted from the enhanced absorption and large surface area of the composite compared to ZnO. The synthesized flakes like ZnO and ZnO-G composites offer promising materials for DSSC applications.