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In this study, zinc oxide nanoparticles (ZnO NPs) in powder and in thin film were successfully synthesized first time using an eco-friendly, simple and cost effective green synthesis method mediated by corn husk (Zea mays) extract as an effective chelating agent, and zinc nitrate hexahydrate as precursor. Diverse characterizations techniques such as High Resolution – Scanning Electron Microscopy (HR-SEM), Energy Dispersive X- rays Spectroscopy (EDS), X-Rays Diffraction (XRD), and UV – Vis – NIR spectroscopy as well as Photoluminescence (PL) were investigated to confirm ZnO NPs nature. For the ZnO NPs powder, highly crystalline ZnO nanoparticles (ZnO NPs) annealed at 500°C which are 48.635 nm in particles size were characterised by HR-SEM and XRD analysis. The structure morphology and the constituents of the resultant ZnO powder were investigated respectively by HR-SEM and EDS. UV – Visible spectroscopy analysis was investigated on the optical band gap of ZnO NPs, which was calculated to be 3.31 eV. This result indicates that ZnO NPs can be used in metal oxide semiconductor-based devices. For the ZnO NPs thin film, XRD patterns of hexagonal wurtzite structure with c/a ratio about of 1.60 and μ – parameter of 0.38 were obtained. PL measurements showed a broad emission band in the 380 – 800 nm range, centred at 481 nm. ZnO NPs thin film yielded relatively more intense photoluminescence spectra than the ZnO NPs powder. The intrinsic point defects and defect level transitions responsible for the broad emission are discussed.
P-type NiO powders with an average crystallite size of 16 nm as shown by x-ray diffraction analysis were produced via biosynthesis using cactus plant extract. SEM showed that the NiO powders consisted of particles with sizes in the 20-35 nm range. A cyclic voltammetric study of the NiO nanopowders showed a quasi-reversible redox processes with the NiO powder showing potential for pseudo capacitance. Through these findings the use of natural Cactus extracts is hereby shown to be a cost-effective and environmentally friendly alternative for preparing Nickel oxide nanosized powders that can be of use in a variety of energy storage applications.
Bio-reduction agents are being explored to synthesised nanoparticles to minimize the effects of toxic chemicals. The present study was focused on green approach for the synthesis of zinc oxide nanoparticles using aqueous seeds extract of Papaver somniferum. The biosynthesised ZnO NPs (27.8nm) were characterized by using of spectroscopy and microscopy instruments. The surface morphology and the structural analysis confirms the formation of hexagonal nanostructure and a pure zincite nature of ZnO nanoparticles (NPs) respectively. The EDS spectrum confirms pure ZnO NPs were synthesised. From electrochemical properties, the CV indicates both anodic and cathodic sweep are quasi-reversible properties whose intensity increases with the scan rates. The bode plot shows the maximum angles of 74o which is an indication of a higher conductivity of ZnO NPs.
Functional polymers were previously employed to minimize the susceptibility of metallic nanoparticles (MNPs) for aggregation. Herein, we intended to conjugate catechol moiety into the polymer chain end considering its anchoring ability to virtually most surfaces. Accordingly, catechol end-functionalized polysarcosine (cat-PSar) was successfully prepared from the ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCA) using dopamine hydrochloride initiator. ROP of Sar-NCA was carried out at different monomer to initiator feed ratios. The molecular structure of cat-PSar was confirmed by 1H NMR and MALDITOF. Afterward, the obtained catechol functionalized polymer was used for in-situ synthesis and stabilization of silver nanoparticles (Ag-NPs) in aqueous solution. The observed characteristic absorption peak at λmax of 415 nm indicates the formation of Ag-NPs. Scanning electron microscope (SEM) images also elucidate the formation of Ag-NPs with the relatively small sizes of the nanocomposite at a high concentration of silver nitrate. Hence, biomimetic polymers could play a dual role as reducing and stabilizing agents in the preparation of monodispersed MNPs.
Highly oriented VO2 (M1) thin films are difficult to produce using non-crystalline substrates. For example, to produce such films on glass has required post-annealing or the use of a ZnO transparent layer. Here, we overcome this challenge and report highly oriented VO2 (M1) in the (100) plane directly on the glass substrate by pulsed laser deposition (PLD). We study the influence of the laser wavelengths (1064, 532, 355 and 266 nm) on the orientation of VO2 (M1) deposited on Corning glass. We find that the laser wavelength of 532 nm leads the most highly a-axis textured VO2 (M1) demonstrating the highest reversible metal-to-insulator at about 62 °C with a lowest hysteresis width of approximately 9 °C. One of the conditions is to select the green 532 nm wavelength laser in PLD as this particular laser wavelength also produces films with highest roughness value (of more than 60 nm) when compared to other wavelengths which produce films of roughness values less than 40 nm.
A novel technique providing a cost effective sustainable wet chemical etching method of synthesizing black Moly thin films rapidly has been presented. A top- down method for fabricating MoO3 has been investigated to understand the effect of chemical etchant concentration on the structural, morphological and optical properties of the thin films on Mo substrates. The XRD patterns demonstrated the formation of Tugarinovite MoO2 films on Mo substrate after annealing at 500°C in a vacuum. In this work, we developed nanostructured MoO3 on Mo substrate solar absorber, with a high solar absorptance of over 89%. These results suggest that solar absorbers made from refractory metal oxide nanostructures can be used for solar thermal applications.
This contribution reports on the biosynthesis of nickel oxide and zinc oxide nanoparticles (NiO-NPs & ZnO-NPs) via a natural extract from Moringa Oleifera leaves as an effective chelating and/or oxidizing/reduction agent of nickel nitrate hexahydrate and zinc nitrate hexahydrate. The structural and optical properties of these two types of semiconductors obtained in a similar procedure are investigated using X-rays Diffraction (XRD), Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR), diffuse reflectance UV-Visible-NIR and Photoluminescence (PL) techniques. The structural analysis shows the formation of pure cubic NiO-NPs and pure wurtzite ZnO-NPs with an average crystallite size of 17.80 nm and 10.81 nm respectively. Their band gaps, calculated from the diffuse reflectance analysis were found to be 4.28 eV and 3.35 eV respectively.
This contribution provides the synthesis and characterization of nickel oxide nanoparticles (NiO NPs) which were prepared by green synthesis method using natural extract oranges peel skin (Peel Citrus Sinensis) as an effective bio-oxidizing/bio-reducing agent. The effect of different calcination temperatures on the size of the NiO NPs was investigated. The prepared nanoparticles were characterized by various techniques such as X-rays diffraction (XRD) results indicated that all the samples have a face-centered cubic (FCC) structure and confirmed the presence of high degree of crystallinity nature NiO NPs. The functional group composition of NiO NPs were investigated by using attenuated total reflection-Fourier transform infrared (ART-FTIR), Photoluminescence (PL), and Scanning electron microscopy (SEM).