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Öğe Considerations about the determination of optical bandgap from diffuse reflectance spectroscopy using the tauc plot(Springer India, 2024) Jubu, Peverga R.; Obaseki, O. S.; Ajayi, D. I.; Danladi, E.; Chahrour, Khaled M.; Muhammad, A.; Landi Jr, S.The optical diffuse reflectance data of a semiconductor material is usually converted into the Kubelka-Munk function before proceeding to process the conventional Tauc's plot from which optical bandgap energy can be determined. Firstly, it is conventional/ customary to convert the percentage reflectance (R-infinity(%)) data, which is obtained from UV-vis measurement into an equivalent reflectance (R-infinity) that range between 0 and 1 before processing the Tauc's plot. Secondly, the Kubelka-Munk function is usually multiplied by the incident photon energy, h nu, to produce an all-elements/ comprehensive Tauc's plot. Literature is scarce to convincingly demonstrate that a correct bandgap value can, alternatively be obtained from the Tauc's plot that is derived directly from the (R-infinity(%) data without having to convert to R-infinity. Also, publication is rarely available to demonstrate that a proper bandgap value can be determined without having to multiply the Kubelka-Munk function by the term h nu. The present investigation shows diminutive differences in the bandgap values estimated from the R-infinity(%)-based Tauc's plots and the equivalent R-infinity-based Tauc's plots. This suggests that either of the methods can be employed for a precise bandgap estimate. A comparison between the magnitudes of the bandgap energies determined from the comprehensive Tauc's plot and when the Kubelka-Munk function is not multiplied by h nu reveals insignificant differences in the estimated values. This suggests that either of the two methods can be employed to obtain a reliable bandgap for direct and indirect optical gap semiconductors.Öğe Crystallinity tuning of LCNO/graphene nanocomposite cathode for high-performance lithium-ion batteries(Elsevier, 2024) Haider, Adawiya J.; Chahrour, Khaled M.; Addie, Ali J.; Abdullah, Ahmed Q.; Jubu, Peverga R.; AL-Saedi, Safaa I.; Naje, Asama N.In this work, a graphene-enhanced LiCo0.525Ni0.475O2 (LCNOG) cathode was synthesized by self-propagating high-temperature synthesis and the effects of annealing at 650-850 degrees C were investigated. Sharper X-ray diffraction peaks showed enhanced crystallization with an increase in average crystallite size from 28 nm to 56 nm after annealing at 850 degrees C. LCNOG annealed at 850 degrees C delivered a high capacity of over 2030 J compared to 1280 J, with a near ideal coulombic efficiency of 99.5 % and long cycle stability. The acceleration of kinetics is evidenced by more favorable redox peak positions in voltammetry and a 5-fold lower interfacial resistance in electrochemical impedance spectroscopy. The improved performance is due to the larger grain size, higher crystallinity, increased conductivity and graphene-induced diffusion facilitation. The relationship between crystallinity and cathodic properties provides critical insight into cathode design. The exceptional performance achieved by tailoring crystallinity through annealing makes LCNOG a potential material for high-voltage cathodes for lithium-ion technology.Öğe CuO/Cu/rGO nanocomposite anodic titania nanotubes for boosted non-enzymatic glucose biosensors(Royal Soc Chemistry, 2023) Chahrour, Khaled M.; Ooi, Poh Choon; Nazeer, Ahmed Abdel; Al-Hajji, Latifa A.; Jubu, Peverga R.; Dee, Chang Fu; Ahmadipour, MohsenHighly arranged porous anodic titania (TiO2) nanotube arrays (ATNT) were fruitfully fabricated by the anodization of Ti foil in an ammonium fluoride electrolyte. Then, the CuO/Cu nanoparticles were consistently decorated onto the porous ATNT surface through electrochemical deposition and afterward impregnated into graphene oxide (GO) aqueous solution to produce CuO/Cu/GO-ATNT, which was then electrochemically reduced to form CuO/Cu/rGO nanocomposite ATNT electrode. The microstructures, morphologies, and chemical elements were investigated using XRD and FESEM techniques linked with EDS and XPS, respectively. The as-fabricated CuO/Cu/rGO nanocomposite ATNT electrode was utilized for non-enzymatic glucose sensing in a neutral electrolyte and exhibited superior electro-catalytic activity compared with the pristine and CuO/Cu nanoparticle ATNT electrodes. The electrocatalysis performance of the recommended CuO/Cu/rGO nanocomposite ATNT electrode was inspected and optimized. The experimental results exposed an effective amperometric electrode of glucose acquired under 0.6 V vs. Ag/AgCl with an excellent sensitivity of (371.6 mu A mM(-1) cm(-2)), a low detection limit (22.8 mu M), and a wide linear range from 0.5 mM to 16 mM (R-2 = 0.9992). This designed non-enzymatic glucose biosensor demonstrated high stability, reproducible, and selective biosensor. Hence, this endorses its promising technique for the detection of glucose samplers for clinical and pharmaceutical diagnoses.Öğe Enhanced photoelectrochemical transient photoresponse properties of molybdenum oxide film deposited on black silicon(Elsevier, 2023) Jubu, Peverga R.; Yusuf, Bashir; Abdulkadir, Auwal; Obaseki, O. S.; Chahrour, Khaled M.; Yusof, Yushamdan; Dehiin, Hile D.Nanostructured black silicon (b-Si) is widely deployed for different solar applications due to its novel light-harvesting characteristics, and large surface area-to-volume ratio. The present research work applies a novel approach via the chemical vapour deposition method to prepare molybdenum oxide (MoO3) film on a b-Si substrate for photoelectrochemical application. X-ray diffraction revealed alpha-MoO3 phase, with the MoO3/b-Si film exhibiting a relatively large crystallite size and improved crystalline quality. Optical reflectance measure-ments showed a relatively low reflectance and reduced optical bandgap energy for the MoO3/b-Si film. Chro-noamperometric measurements showed an enhanced photocurrent density of 656.34 mu A/cm2 at 1 V bias for the MoO3/b-Si photoanode measured in a 0.5 M H2SO4 solution. The enhanced photoelectrochemical activity could be attributed to an increase in light absorption, the relatively small bandgap energy, improved crystalline quality, and improved charge carrier separation and transfer at the interface.Öğe Photoanodic properties of In/ß-Ga2O3 nanostructures fabricated under hydrogen reducing ambient by the vapour-phase growth method(Elsevier, 2023) Jubu, Peverga R.; Danladi, E.; Chahul, H. F.; Aldayyat, A.; Yusof, Y.; Chahrour, Khaled M.; Kyesmen, P. I.A great deal of efforts have been dedicated to reduce carrier recombination problem in ss-Ga2O3 using strategies, such as doping, compositing, and interfacing with different materials to enhance device performance. However, reports are rarely available for integrating In with ss-Ga2O3 for photoelectrochemical applications. Herein, we reports the effect of In addition in ss-Ga2O3 to produce In/ ss-Ga2O3 nanocomposite for photoelectrocatalysis. The intrinsic sample exhited mixed-phase (a-ss)-Ga2O3, whereas the composite showed a mixed-phase ss-Ga2O3-in-dium. A significant amount of In was detected on the heterogenous film, suggesting that doping was exceeded. A significant bandgap narrowing was observed from 4.79 to 4.45 eV upon In incorporation. The presence of In in ss-Ga2O3 resulted in a shift in photoluminescence emission from violet to green light. Photoelectrochemical measurements in 0.1 M KOH solution demonstrated a relatively high photocurrent density of 1.720 mA/cm2 at 1.0 V vs. Ag/AgCl for the In/ ss-Ga2O3 heterogeneous film.Öğe Titanium oxide nanotube film decorated with ?-Ga2O3 nanoparticles for enhanced water splitting properties(Pergamon-Elsevier Science Ltd, 2022) Jubu, Peverga R.; Chahrour, Khaled M.; Yam, F. K.; Awoji, O. M.; Yusof, Yushamdan; Choo, Ee BeeTiO2 is a wide bandgap material with inherent photogenerated charge carrier recombination problems, which reduces its photoelectrochemical (PEC) water splitting efficiency. Considerable efforts have been dedicated to reducing this charge recombination problems by decorating the film's surface using transition metal nano particles (NP) to enhanced device performance. And considerable numbers of literature reports are available to this respect. However, reports are rare for the surface modification of TiO2 nanotubes (TNT) arrays with metal oxide, specially by beta-Ga2O3 nanostructures and its potential applications. Herein, the PEC water splitting properties of beta-Ga2O3 NP (GNP)-modified TNT arrays is described. The TNT were synthesized by anodization, whereas the GNP were fabricated by chemical vapour deposition method. X-ray diffraction (XRD) results revealed the presence of weak beta-Ga2O3 peaks and reduction in crystallite size upon GNP addition. The integration of GNP on the TNT arrays resulted in a slight increase in optical bandgap from 3.4 to 3.6 eV observed by UV-vis measurements. Linear sweep voltammetry measurement for the modified TNT photocatalyst showed a 32.5% enhancement in photocurrent density compared to the bare TNT photoelectrode, measured in 1 M HCl solution. Elemental analysis confirmed the presence of beta-Ga2O3 , thereby supporting the XRD and UV-vis results. This study demonstrates that GNP-activated TNT arrays could be used as photoanode for enhanced photocatalytic activity in the PEC cell.
