Selma M. H. Al-Jawad

Bio: Selma M. H. Al-Jawad is an academic researcher from University of Technology, Iraq. The author has contributed to research in topics: Thin film & Chemical bath deposition. The author has an hindex of 13, co-authored 49 publications receiving 377 citations.

Preparation of n -ZnO/ p -Si solar cells by oxidation of zinc nanoparticles: effect of oxidation temperature on the photovoltaic properties

Abstract: In this study, n-ZnO/p-Si solar cells were fabricated by spraying ZnO nanoparticles (NPs) film synthesised by dissolving of high purity zinc in hydrogen peroxide H2O2 followed by thermal oxidation in air on p-type silicon substrates. The oxidation was carried out at different temperatures (200–500) °C. The crystalline structure of the ZnO NPs films was investigated by X-ray diffraction which indicated wurtzite structure films along (100) plane. The morphology of the NPs was studied by atomic force microscopy and scanning electron microscopy. The result showed an average grain size of ZnO NPs in the range of (72.7–95.8) nm and the surface roughness increasing with oxidation temperature. Three peaks located at ultraviolet, violet and green emission regions were noticed in the photoluminescence spectra of ZnO NPs. From optical studies, it was shown that the direct optical band gap is found to be in the range of (3.85–3.96) eV depended on the oxidation temperature. The synthesised ZnO films have n-type conductivity, and the mobility was in the range of (7–24) cm2 V−1 s−1. Current–voltage I–V and capacitance–voltage C–V of ZnO NPs/Si heterojunction solar cell were investigated as function of oxidation temperature. The spectral response of n-ZnO NPs/p-Si solar cell showed two peaks of response and its maximum value approaching 0.62 mA W−1 at λ = 800 nm. Solar cell oxidized at 500 °C gave open circuit voltage V OC of 375 mV, short circuit current density J SC of 25 mA cm−2, a fill factor FF of 0.72, and conversion efficiency η of 6.79 % under illumination of 100 mW cm−2.

Studying structural, morphological and optical properties of nanocrystalline ZnO:Ag films prepared by sol–gel method for antimicrobial activity

Abstract: Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500 °C for 2 h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000 nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23 eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.

Thin films and nanostructures of niobium pentoxide : fundamental properties, synthesis methods and applications

Abstract: As one of the transition metal oxides, niobium pentoxide (Nb2O5) offers a broad variety of properties that make it a potentially useful and highly applicable material in many different areas. In comparison to many other transition metal oxides, Nb2O5 has received relatively little attention, which presents a significant opportunity for future investigations aimed at fundamentally understanding this material and finding new and interesting applications for it. In this article, a general overview of Nb2O5 is presented which focuses on its fundamental properties, synthesis methods and recent applications, along with a discussion on future research directions relevant to this material.

Gold nanoparticles-mediated photothermal therapy and immunotherapy.

Abstract: Cancer has been a significant threat to human health with more than eight million deaths each year in the world. Therefore, there is a significant need for novel technologies to effectively treat cancer and ultimately reduce cancer recurrences, treatment costs, number of radical cystectomies and mortality. A promising therapeutic platform for cancer is offered by nanoparticle-mediated therapy. This review highlights the development and applications of various nanoparticle platforms for photo-induced hyperthermia and immunotherapy. Taking advantage of gold's high biocompatibility, gold nanoparticles (GNPs) can be injected intravenously and accumulate preferentially in cancer cells due to the enhanced permeability and retention effect. Various gold nanoplatforms including nanospheres, nanoshells, nanorods, nanocages and nanostars have been used for effective photothermal treatment of various cancers. GNPs have also been used in immunotherapies, involving cancer antigen and immune adjuvant delivery as well as combination therapies with photothermal therapy. Among GNPs platforms, gold nanostars (GNS) have great therapeutic potential due to their unique star-shaped geometry that dramatically enhances light absorption and provides high photon-to-heat conversion efficiency due to the plasmonic effect. This photothermal process can be exploited to specifically ablate tumors and, more importantly, to amplify the antitumor immune response following the highly immunogenic thermal death of cancer cells. GNS-mediated photothermal therapy combined with checkpoint immunotherapy has been found to reverse tumor-mediated immunosuppression, thereby leading to the treatment of not only primary tumors but also cancer metastasis, as well as to induce effective long-lasting immunity, in other words, an anticancer 'vaccine' effect.

Circulating purification of cutting fluid: an overview

Abstract: Cutting fluid has cooling and lubricating properties and is an important part of the field of metal machining. Owing to harmful additives, base oils with poor biodegradability, defects in processing methods, and unreasonable emissions of waste cutting fluids, cutting fluids have serious pollution problems, which pose challenges to global carbon emissions laws and regulations. However, the current research on cutting fluid and its circulating purification technique lacks systematic review papers to provide scientific technical guidance for actual production. In this study, the key scientific issues in the research achievements of eco-friendly cutting fluid and waste fluid treatment are clarified. First, the preparation and mechanism of organic additives are summarized, and the influence of the physical and chemical properties of vegetable base oils on lubricating properties is analyzed. Then, the process characteristics of cutting fluid reduction supply methods are systematically evaluated. Second, the treatment of oil mist and miscellaneous oil, the removal mechanism and approach of microorganisms, and the design principles of integrated recycling equipment are outlined. The conclusion is concluded that the synergistic effect of organic additives, biodegradable vegetable base oils and recycling purification effectively reduces the environmental pollution of cutting fluids. Finally, in view of the limitations of the cutting fluid and its circulating purification technique, the prospects of amino acid additive development, self-adapting jet parameter supply system, matching mechanism between processing conditions and cutting fluid are put forward, which provides the basis and support for the engineering application and development of cutting fluid and its circulating purification.