Papers by Author: W.O. Soboyejo

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Authors: S.T. Azeko, O.S. Odusanya, K. Malatesta, Nicolas Anuku, W.O. Soboyejo
Abstract: Improper disposal of commodity plastics such as polyethylene (PE) in the environment causes land pollution and soil infertility. It is unsightly and strongly threatens plant and animal life. The current effort describes the bacteria-mediated biodegradation of polyethylene by Serratia marcescens marcescens (SM) without prior exposure to thermo-oxidative aging. This study further describes the mechanism involved in the biodegradation of PE, in which a carbonless medium containing essential minerals and vitamins and powdered PE, were placed in the presence of overnight cultures of SM. The samples were incubated at 30°C, centrifuged at a speed of 141 revolutions per minute (rpm) in a rotary shaker for ten weeks in order to observe the degradation process. The effects of cell-free supernatants (from the SM cultures) upon the degradation of sterile PE are elucidated. The results show that the supernatants from SM degrade PE faster than the bacteria, with a 37.5 percent of degradation rate within a month. The SEM micrographs suggest that the biodegradation of polyethylene involves the formation and coalescence of microvoids. The DSC results revealed that the feeding activity of SM is mostly favored at the crystalline region due to its high energy.
Authors: T.A. Owoseni, S.G. Olukole, A.I. Gadu, I.A. Malik, W.O. Soboyejo
Abstract: Bioinspired design involves the use of concepts observed in natural biological materials in engineering design. The hope is that the leveraging of biological materials in the engineering domain can lead to many technological innovations and novel products. This work presents the initial material characterization of kinixys erosa tortoise shell using a combination of x-ray diffraction, optical/scanning electron microscopy and micro-mechanical testing. The results were used in the analytical/computational modelling of shell structures. The potential implications or the results were then discussed to give fundamental understanding of deformation and stress responses of shell structures
Authors: S.O. Dozie-Nwachukwu, G. Etuk-Udo, J.D. Obayemi, Nicolas Anuku, O.S. Odusanya, Karen Malatesta, C. Chi, W.O. Soboyejo
Abstract: The biosynthesis of gold nanoparticles from Nauclea latifolia leaf/plant extract is presented in this paper. The synthesis is shown to produce gold nanoparticles from hydrogen Tetra-chloro auric acid (HAuCl4) in less than 1 minute. The resulting gold nanoparticles are characterized using UV/Visible spectrophotometry (UV-Vis), Energy Dispersive X-ray Spectroscopy (EDX), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). The implications of the results are discussed for potential applications of biosynthesized gold nanoparticles in cancer detection and treatment.
Authors: S.O. Dozie-Nwachukwu, J.D. Obayemi, Y. Danyo, G. Etuk-Udo, N. Anuku, O.S. Odusanya, Karen Malatesta, C. Chi, W.O. Soboyejo
Abstract: This paper presents the biosynthesis of gold nanoparticles from the bacteria, Serratia marcescens. The intra-and extra-cellular synthesis of gold nanoparticles is shown to occur over a range of pH and incubation times in cell-free exracts and biomass of serratia marcescens that were reacted with 2.5mM Tetrachloroauric acid (HAuCl4). The formation of gold nanoparticles was identified initially via color changes from yellow auro-chloride to shades of red or purple in gold nanoparticle solutions. UV-Visible spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray spectroscopy (EDS), Helium Ion Microscopy (HIM) and Dynamic Light Scattering (DLS) were also used to characterize gold nanoparticles produced within a range of pH conditions. The results show clearly that the production of gold nanoparticles from cell-free extracts require shorter times than the production of gold nanoparticles from the biomass.
Authors: Joseph Asare, B. Agyei-Tuffour, O.K. Oyewole, G.M. Zebaze-Kana, W.O. Soboyejo
Abstract: This research investigates the effects of bending on the electrical, optical, structural and mechanical properties of flexible organic photovoltaic (OPV) cells. Bulk heterojunction organic solar cells were fabricated on Polyethylene terephthalate (PET) substrates using Poly-3-hexylthiophene: [6, 6]-phenyl-C61-butyric acid methyl ester (P3HT: PCBM) as the active layer and Poly (3, 4-ethylenedioxythiophene) Polystyrenesulfonate (PEDOT: PSS) as the hole injection layer. All the organic layers were deposited by spin coating while the Al cathode was vacuum thermally evaporated. The Indium Tin Oxide (ITO) anode has an average optical transmittance of 85% in the visible spectrum, a sheet resistivity of 60 ohms per square and an average surface roughness of 3nm. The relationship between the optoelectronic performance of the various device layers and the applied mechanical strains has been analyzed. The effects of stress and strain on the current-voltage characteristics of the device and its failure were modeled using the Abaqus software.
Authors: O.K. Oyewole, J. Asare, D.O. Oyewole, B. Agyei-Tuffour, V.C. Anye, M.G. Zebaze Kana, W.O. Soboyejo
Abstract: This paper presents the results of a study of the adhesion and optical properties of layered structures that are relevant to stretchable organic solar cells. A combination of modeling and experiments is used to investigate the effects of adhesion and stretching on failure mechanisms and optical properties. The adhesion between the possible bi-layers is determined by incorporating force microscopy measurements of pull-off forces into adhesion models. The failure mechanisms associated with the tensile stretching of the structures are then investigated using a combination of in-situ/ex-situ microscopy observations and analytical/computational models. The resulting changes in optical properties are elucidated before discussing their implications for the design of stretchable organic solar cells
Authors: F.O. Kolawole, A.M. Rees, G.A. Etuk-Udo, Shola Odusunya, W.O. Soboyejo
Abstract: Conversion of lignocellulosic biomass from bamboo (Bambusa vulgaris) to butanol is an important alternative energy source. In this work, bamboo was used as biomass feedstock for the production of butanol by the fermentation of sugars. Mechanical grinding was carried out, followed by pre-treatment with dilute sulfuric acid concentration of 0.5 and 1.0 (%v/v). This was done at temperatures of 25, 110, 120, 150 and 200°C at time intervals of 2 and 4 hours. Pre-hydrolysate was later analyzed for total sugars by the use of UV-Visible Spectrophotometer. For the conditions considered, the maximum glucose yields were obtained at 200°C. The yields after pre-treatment were 244.80 mg/g, at pre-treatment conditions of 200°C and acid concentrations of 1% for 4 hours. Water insoluble solids obtained were subsequently hydrolysed with Celluclast (Trichoderma reesi) and β-glucosidase (Novozyme 188) for 72 hrs. Bacteria (Clostridium acetobutylicum) were then used to ferment the solubilized sugar into butanol. Raman spectroscopy was used to determine the butanol yield. Optical Microscope images of bamboo samples were obtained at various stages of pre-treatment and enzymatic hydrolysis. These revealed the morphological changes that occur in the cellular structure of the bamboo during exposure to acid and enzymatic hydrolysis. The results show that, increasing temperature, time and acid concentration are associated with higher total sugar yields and cellulose conversion rates. 10.4mg/mL of butanol was produced in sample treated at 1% H2SO4 for 110°C.
Authors: E. Annan, K. Mustapha, S.T. Azeko, O.S. Odusanya, Karen Malatesta, W.O. Soboyejo
Abstract: According to World Health Organization, there was increase in the number of people that have access to safe drinking water between 2006 and 2010. Such trends can be countered partly by the use of ceramic water filters that can remove microbial pathogens from water. However, the initial flow rates in such filters are often limited to ranges between 1 and 3 L/hr. The flow rates may vary statistically and decrease with increasing filter use. In this paper, the flow through ceramic water filters is characterized using Darcy’s equation. An effective permeability is obtained for filters with a range of micro-and nanoscale pore sizes. The statistical variations in the flow rates and effective permeabilities are elucidated along with the potency of multiple filter system for scale-up studies in serving a community.
Authors: B. Agyei-Tuffour, E.R. Rwenyagila, J. Asare, O.K. Oyewole, M.G. Zebaze Kana, D.M. O’Carroll, W.O. Soboyejo
Abstract: This paper explored the effects of pressure on contacts between layers of organic photovoltaic cells with poly (3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as the active layer. The contacts between the layers are modeled using analytical concepts and finite element models. The potential effects of surface roughness and dust particles are modeled along with the effects of lamination pressure and adhesion energy. The results show that, increased pressure is associated with decreased void length or increased contact length. The contacts associated with the interfaces between the active layer and the hole/electron injection layer poly (3,4-ethylenedioxythiophene: poly styrenesulphonate (PEDOT.PSS) and Molybdenum trioxide (MoO3) are also compared. The implications of the results are discussed for the design of stamping/lamination processes for the fabrication of organic photovoltaic cells.
Authors: S.K. Kolawole, F.O. Kolawole, O.P. Enegela, O.O. Adewoye, A.B.O. Soboyejo, W.O. Soboyejo
Abstract: This paper presents the results of the combined study of experiments and modeling of the pitting corrosion behavior of low carbon steel. The effects of pH are elucidated via experiments on low carbon steel exposed to various corrosive media. The corrosion rates for the steel samples immersed in various corrosive media were determined by polarization experiments via a gamry potentiostat. The microscopic observations of the surfaces reveal clear evidence of corrosion pits that increase in size with increasing exposure duration. The observed pit size distribution and the evolution of pit size are modeled using statistical models. The implications of the results are used for the application of low carbon steels in corrosive environment.
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