Browsing by Author "Opoku, Francis"

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    Antimicrobial and Phytochemical Properties of Alstonia Boonei Extracts
    (OMICS Publishing Group, 2015-01-01) Opoku, Francis; Akoto, Osei
    Alstonia boonei De wild is a major spice crop grown abundantly in Ghana and other tropical countries. In this study we have carried out phytochemical analysis and antimicrobial investigation of ethanol and aqueous extracts of the root of Alstonia boonei against a panel of clinically significant bacterial and fungal strains. Four Gram positive and Gram negative bacteria namely Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus were subjected to test the antimicrobial activity along with one fungi namely, Candida albicans. The ethanol and aqueous extracts of root of Alstonia boonei were subjected to microbial susceptibility assays using agar well diffusion method. Phytochemical screening was done to test the presence of phytochemicals responsible for the antimicrobial potential of roots of Alstonia boonei. The results of the phytochemical studies revealed the presence alkaloids, cyanogenetic glycosides, flavonoids, terpenoids and steroids and saponins. Susceptibility testing by disc diffusion assay revealed significant antimicrobial activity of methanol and aqueous extracts of the roots against the pathogens tested. The minimum inhibitory concentrations (MIC) of the various extracts by Agar Dilution method ranged from 3.0 to 10.0 mg/ml. The ethanol extracts exhibited better antimicrobial activity than aqueous extract. The study findings provide supportive evidence for the use of Alstonia boonei in traditional medicines.
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    Density functional theory study of the gas phase decomposition of single-source precursors for the chemical vapour deposition of binary and ternary metal chalcogenides
    (2013) Opoku, Francis
    Chemical vapour deposition (CVD) method has been widely exploited to grow high quality thin films of metal chalcogenides. However, in some processes the formation of thin films in the gas phase at higher temperature can be a major obstacle to decreasing the deposition rate, thus the thin films formation reaction can compete with the surface deposition reaction and consume the gas phase reactants, before the vapour reaches the heated substrate surface. A variety of single source precursors have been developed for the deposition of thin films. However, few single source precursors have deposited good quality thin films. Hence it is important to design and develop single source precursors with appropriate physico-chemical properties. In this work, a series of novel metal (Pb, Zn, Cd) complexes of diphenyl- and diisopropyl-thioselenophosphinate were studied. These organometallic complexes were employed as potential single source precursors for the deposition of metal chalcogenides thin films. Metal chalcogenides thin films have potential applications in photovoltaics, solar cells, microelectronics, displays and opto-electronic devices. Density functional theory (DFT) calculations have been shown to be valuable tools for elucidating the various decomposition processes of single source precursors and thus making their development more effective and less costly. The reaction mechanisms involved in the thermal decomposition of the precursors were explored by computing the activation barriers and reaction energies at the density functional theory MO6/LACVP * level of theory. This thesis is made up of the following chapters: 1. Chapter one presents a general introduction on metal chalcogenides, chemical vapour deposition process, single-source precursors and applications of metal chalcogenides. v Literature reports about thin films and their applications, and methods of fabrication of thin films are also presented. 2. Chapter two gives the general introduction on computational chemistry. The molecular mechanics method, semi empirical methods and ab initio methods are also discussed in addition to the hybrid methods and basis sets. 3. Chapters three to six describe the density functional theory at the MO6/LACVP * level of theory for the thermal decompositions of Pb[(C6H5)2PSSe]2, Pb[( i Pr)2PSSe]2, Zn[( i Pr)2PSSe]2 and Cd[( i Pr)2PSSe]2 single-source precursors for the chemical vapour deposition of binary and ternary metal chalcogenides. 4. Chapter seven gives a general conclusion and recommendation for future studies.
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    Effect of Jatropha cake and inorganic fertilizer on the growth and yield of Jatropha curcas (L.) A
    (2015-09-25) Opoku, Francis
    Since the surge of interest in renewable energy alternatives to liquid fossil fuels, attention has been paid to the possibility of growing Jatropha curcas, for the purpose of producing biofuel. The seed of Jatropha curcas contains 30% oil that can be used in standard diesel engines. Jatropha biodiesel being a profitable alternative, it has attracted many multinational companies into Ghana with the quest of establishing jatropha plantations. In line with the Bioenergy Policy of Ghana, the government is collaborating with the private sector to develop about one million hectares of jatropha plantation throughout the country. The need therefore arises as to how to improve the yield of jatropha through agronomic techniques such as fertilization to produce enough oil to contribute to the energy requirements of the nation. Few studies on its utilization have proven that jatropha bio-waste (cake) has the potential as a fertilizer. This study was therefore carried out at the Agricultural Research Station at Awomaso, under the College of Agriculture and Natural Resources (CANR), Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana, to investigate the effect of different levels of jatropha cake and their combinations with NPK 15:15:15 on the growth and yield of Jatropha curcas plants. A Randomized Complete Block Design (RCBD) with three replicates was used and twelve treatments applied. Results of a one year study showed a significant (P < 0.05) vegetative growth (number of leaves, stem height, stem diameter and number of branches) response of Jatropha curcas to all the fertilized treatments except lower levels of NPK (T1= 250 Kg/ha). Early growth responses were observed in plants that received either NPK only or their combinations with jatropha cake. Later, plants that received lower levels of NPK showed similar vegetative growth as controls while their combinations with jatropha cake still performed better. Plants that received jatropha cake only responded late but recorded similar stem heights, stem diameters vi and number of branches as those that received NPK fertilizers and their combinations with jatropha cake. The combination of both organic and inorganic amendments ensured increased vegetative growth at all stages of the plant’s life. Also early flowering as well as fruiting occurred in all fertilized plants but did not translate into higher seed yield. The results of the effects of the various treatments and the plants on the soil’s physical and chemical properties showed no significant differences (p>0.05) between any of the treatments in soil characteristics after two years. When compared to the initial soil properties however, all the treatments had significantly higher (p<0.05) pH values than the initial. The results reported in this work indicate that fertilizer application can induce higher and faster vegetative growth but not seed yields in the first year of the plant’s establishment. Also fertilization does not affect the soil’s physical and chemical properties. However, the jatropha plant can reduce soil acidity after two years of establishment.
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    Heavy metal contamination assessment of groundwater quality: a case study of Oti landfill site, Kumasi
    (Springer International Publishing, 2019-03-04) Boateng, Thomas Kwame; Opoku, Francis; Akoto, Osei
    Environmentally friendly municipal solid waste management is the biggest problem facing several developing countries, including Ghana. Heavy metals pollution generated by landfill leachate has become increasingly concerned due to its potential impact on human health. This study assessed the pollution level and sources of heavy metal levels in groundwater, as well as evaluated the human health risk effect. The sampling technique and sample treatment were done based on the Standard Methods for the Examination of Water and Wastewater. The results suggested that the mean concentration of Pb, Fe, Cd, and Cr was above the acceptable limits of the World Health Organization for drinking water except for Zn and Cu. The heavy pollution index indicates contamination, while hazard index values at sites BH1 and W4 were greater than one, suggesting adverse health effects. However, the heavy metal pollution index values were less than the critical limit of 100 for drinking water. Multivariate analysis predicted that lithogenic and anthropogenic factors were the possible sources of water pollution of heavy metal in the Oti community. Thus, multivariate statistical techniques could be a beneficial tool for the evaluation of possible sources of heavy metal contamination. The high levels of heavy metals found in the Oti community suggested a considerable pollution of water by leachate percolation from the landfill site. The findings of the study, which can be used in areas under similar environmental conditions, can offer a valuable benchmark for the design of suitable approaches to manage groundwater resources by both local and national policymakers
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    Theoretical and experimental insight into the construction of FTO/NiSe2/ BiVO4 photoanode towards an efficient charge separation for the degradation of pharmaceuticals in water
    (Journal of Environmental Chemical Engineering, 2023-10) Yusuf, Tunde Lewis; Ogundare, Segun Ajibola; Opoku, Francis; Arotiba, Omotayo A.; Mabuba, Nonhlagabezo; 0000-0002-8308-9113
    The increasing contamination of water bodies by pharmaceuticals has become a major environmental concern, with traditional treatment methods often proving ineffective. In this manuscript, we present a theoretical and experimental investigation into the construction of an S-scheme FTO/NiSe2/BiVO4 (NSB) photoanode toward the photoelectrocatalytic degradation of pharmaceutical pollutants in water. The study focuses on the optimization of the photoanode structure to significantly restrain charge recombination and maximize photoelectrocatalytic performance. The photoanode achieves higher efficiency (76%) in comparison with the pristine FTO/BiVO4 (BVO) (43%) and FTO/NiSe2 (NS) (17%) for the PEC degradation of ciprofloxacin. This can be attributed to the improved band gap (1.92 eV), low charge transfer resistance (9.6 Ω), reduced flat band potential (0.24 V) and higher charge density (4.86 × 1017 cm–1 ) resulting from synergic interaction at the interface of the semiconductor resulting to fast transition of the charge and restraining of recombination of the charge carriers. The accumulation of the electrons majorly takes place at the NS layer as displayed by the theoretical modeling of the charge density difference. This suggests a transition of electrons from BVO to NS. The band offset as well as the built-in electric field across the NSB interface limit the recombination of the photoinduced carriers. The mechanism including the functions of different reactive species is studied, which reveals that the holes mostly dominate the degradation process. Based on density functional theory, active species capture experiment, and photoelectrochemical detection, the synthesized NSB photocatalyst conforms to an S-scheme heterojunction charge transfer mechanism. We consider the composite suitable for the treatment of water contaminated with pharmaceutical waste.