https://repository.seku.ac.ke/handle/123456789/49 2026-07-24T18:54:54Z 2026-07-24T18:54:54Z Ngumbi, Paul K. https://repository.seku.ac.ke/handle/123456789/8405 2026-07-23T08:42:42Z 2021-01-01T00:00:00Z

Synthesis and characterization of graphene-gold nanocomposite counter electrodes for dye-sensitized solar cell application Ngumbi, Paul K. With the increasing global demand for alternative energy, photovoltaic (PV) technology has undergone remarkable evolution extending over four PV generations. Currently, dye-sensitized solar cells (DSSCs), which fall within the 3rd generation are more versatile and relatively less costly compared to the dominant crystalline silicon (Si) technologies. These DSSCs bear the hope of becoming the future solution to the energy crisis. However, the poor catalysis within the electrodes makes DSSCs relatively inefficient hence ineffective for full commercial utilization. This study investigated the use of composite counter electrodes (CEs) by incorporating graphene (Gr) and/or plasmonic gold (Au) nanoparticles (NPs) with the aim to improve the efficiency of the conventional platinum (Pt) based DSSCs. Gold nanoparticles (AuNPs) in colloidal form with an average size of ~12 nm were prepared by chemical reduction method. The size evaluation was done using the resulting localized surface plasmon resonance (LSPR) peak wavelength values (518- 520 nm) based on the UV-Vis spectra data. Graphene modules prepared by chemical vapor deposition (CVD) on a glass/Fluorine-doped tin oxide (FTO) were used as electrode substrates in this work. These modules depicted G and 2D bands at 1380 and 1700 cm-1 respectively under Raman spectroscopy, indicating low defect state of the Gr. Four different sets of composite CE modules namely FTO/Pt (CE1), FTO/Gr/Pt (CE2), FTO/Gr/AuNPs (CE3) and FTO/Gr/AuNPs/Pt (CE4) were prepared. The CEs recorded transmittance above 70% under UV-Vis spectroscopy, meeting requirements for back-electrode application in DSSCs. Photoanode (PA) modules consisting of titanium dioxide (TiO2) on the FTO/Gr substrate were prepared by the doctor-blade method. Three DSSC modules were assembled based CEs CE2, CE3 and CE4 and their PV performance compared to the reference cell based on CE1. Both Gr and AuNPs were found to possess PV properties and enhanced the resulting DSSCs by 13.4 and 10.1% respectively. The DSSCs containing Pt (CE1, CE2, and CE4) performed better in terms of power conversion efficiency (PCE) due to the increased short circuit current densities (Jsc) and fill factors (FF). However, change in the open-circuit voltage (Voc) was negligible. The CE4 based cell design presented the best PCE at 4.62%, In this composite DSSC, the Jsc (9.92 mA/cm2 ), Voc (0.68 V) and FF (0.69) values recorded representing 13.9%, 0.8% and 9.0% increase respectively compared to CE1. This represented a 24.9% PCE enhancement, which is the synergistic effect of Gr and AuNPs as a composite. This remarkable performance could be due to increased electrocatalytic activity resulting from the graphene matrix within the electrodes. It is also partly attributed to the suppressed carrier recombination resulting from the LSPR property of the Au contacts anchored on the Gr surface in the CE structure. Doctor of philosophy in physics, 2021

2021-01-01T00:00:00Z Ogbonna, Vincent A. https://repository.seku.ac.ke/handle/123456789/8284 2026-03-10T07:23:54Z 2025-01-01T00:00:00Z

Spatio-temporal variations in physicochemical water quality and the impact of land use/land cover change In River Athi Basin, Kenya. Ogbonna, Vincent A. The growing impacts of natural processes and human activities on water quality at global, regional, and local scales are raising concerns. The River Athi Basin natural gravitational flow toward lower elevations, ultimately reaching the Indian Ocean, facilitates waste disposal practices among the residence located along the river bank. This study sought to determine the Spatiotemporal Variations in Physicochemical Water Quality and the Impact of Land Use/Land Cover Change in the Mid Reaches of River Athi Basin, Kenya by; 1) examining the influence of land use/land cover change in river Athi Basin from 2015 to 2023. (2) Determining seasonal variation in the physicochemical water quality of the river Athi Basin. (3) Assessing the spatial variation in physicochemical water quality of the river Athi Basin. The study examined the influence of LULC changes from 2015 to 2023 using Landsat 8 imagery, GIS, remote sensing, and GPS technologies for data extraction, image processing, and LULC analysis. Pearson correlation analysis assessed spatial differences of land use land cover impacts on water quality across six sampling stations in the basin. Interview survey was used to supplement the water quality dataset. The studies applied multivariate analysis for spatial and temporal reduction of the multidimensional dataset and identification of pollution sources. Seasonal variations in the physico-chemical water quality of River Athi Basin was determined using eight physicochemical parameters (pH, EC, TDS, NO₃, K, PO₄, BOD, and COD) and two heavy metals (Cd and Cr). Data collection was carried out during two distinct seasonal periods: the short dry and rainy season (August-September for dry, November-December for rainy) in 2023, and the long dry and rainy season (January-February for dry, April-May for rainy) in 2024. An independent T-test was used to compare the mean levels of water quality parameters between dry and rainy seasons. The study assessed spatial variation in the physicochemical water quality of the river basin, covering six sampling stations. One way analysis of variance (ANOVA) compared the mean values of variables of the sampling stations. Multiple linear regression tested the influence of pH, EC, TDS, NO3, K, and PO4 on BOD and COD (oxidation parameters) and cadmium and chromium (heavy metals). The Pearson Product-Moment Correlation Coefficient (PPMCC) assessed the relationships between water physicochemical parameters and heavy metals in seasonal and spatial variations in water quality of the river basin. The findings on LULC analysis show notable shifts in land use from 2015 to 2023. Between these periods, the overall built-up increased to 0.29%, bare-lands declined by 7.06%. Farmlands, forests, and grasslands were elevated by 0.52%, 4.54%, and 2.77%, with decline in open waters by 1.24%. Spatial LULC difference with correlation analysis reveal higher amounts of EC, TDS, Cd, Cr, NO3, and PO4 influencing water quality. Interview survey revealed settlements, agriculture, and climate conditions as the main causes of degradation of water quality. Seasonal finding reveal significant fluctuations in pollution, with the dry season exhibiting higher pollution levels. February demonstrate proliferated temporal pollution, characterized by high concentrations of EC, TDS, BOD, and COD. Spatial finding demonstrated significantly higher pollution signatures in Athi River Town, Stony Athi, and NYS stations, while NYS contribute to higher levels of nutrients, organic pollutants, and heavy metals. In contrast, the control station and Kibwezi Bridge station demonstrates effective self-purification processes. Multivariate analysis revealed pollution sources over time and space in the River Basin. The stable pH levels over time and space was influenced by the buffering capacity. Multiple regression analysis indicates that physicochemical parameters, such as pH, EC, TDS, NO₃, K, and PO₄, explain 62% of BOD variation and 70% of COD variation, as well as 36% of both Cd and Cr variations. Pearson correlation analysis shows strong links between EC, TDS, BOD, and heavy metals (Cd, Cr), with significant associations among nutrients and other water quality indicators. Natural and anthropogenic activities are pivotal drivers of the water quality degradation of River Athi Basin over time and space. This study recommends that the National Environmental Management Authority (NEMA) and the National Environmental Policy (NEP) strengthen regulations on environmental management, water resource conservation, sustainable land use, public health protection, irrigation control, forest preservation, and aquatic ecosystem conservation in order to support global efforts toward achieving Sustainable Development Goals (SDGs). Doctor of Philosophy (Ph.D.) In Environmental Management

2025-01-01T00:00:00Z Musyimi, Charles https://repository.seku.ac.ke/handle/123456789/8100 2025-07-08T11:37:56Z 2025-01-01T00:00:00Z

Educational subsidies and students’ participation rates in education in public secondary schools in Makueni County, Kenya Musyimi, Charles Governments around the world agree that, the ability to provide quality education for all and to respond to new priorities depends on the availability of adequate funding in education. Financing of education is the greatest enabler of learners to participate in education and flow through education system from entry to exit. The purpose of this study was to investigate the influence of educational subsidies on participation rates in public secondary schools in Makueni County, Kenya. The specific objectives of the study were to establish the influence of Free Day Secondary Education (FDSE) capitation grants, government bursary funds, financing by non-state agencies and provision of teaching and learning materials by the government on participation rates in public secondary schools in Makueni County, Kenya. The researcher formulated four null hypotheses stating: There is no statistically significant relationship between FDSE capitation grants, government bursary funds, education financing by non-state agencies and provision of teaching and learning materials by the government and participation rates in public secondary schools in Makueni County, Kenya. The study was anchored on the Classical Liberal Theory by Rousseau. The study adopted a descriptive survey design. The study targeted all 384 schools, all 384 Principals, 384 Deputy Principals and 9 Sub County Directors of Education in Makueni County. Out of the 384 schools, the study sampled 196 schools’ principals and deputy principals through stratified, simple random sampling. Data collection instruments included questionnaires for Principals, Deputies and interview schedule for Sub-county Directors of Education. The instruments were ascertained through piloting and by research experts to ensure content validity while reliability was achieved through piloting and testing reliability. Data was analyzed by use of SPSS version 22. Descriptive statistics such as frequencies, percentages, means and standard deviations and inferential statistics were used to analyze the quantitative data. Qualitative data was analyzed through content analysis and the responses presented in narratives, tables and figures. The results revealed that there was statistically significant relationship between FDSE capitation grants, government bursary funds, education financing by non-state agencies and provision of teaching and learning materials by the government on participation rates in public secondary schools in Makueni County. This was at r values of 0.67,0.68, 0.63, and 0.59 respectively which were all positive and significant with values of 0.014, 0.015, 0.019, and 0.022 respectively. The study concluded that FDSE capitation grants, government bursary funds, financing by non-state agencies and provision of teaching and learning materials by the government all influence students’ participation rates in public secondary schools in Makueni county, Kenya. And that, education subsidies influence students’ participation rates in the study locale. The results indicated that 64% of the variation in the participation of students in schooling in public secondary schools in Makueni County could be explained by provision of education subsidies in financing education. The study recommends that, the government should continue providing and diversifying educational subsidies, schools should come up with income generating activities whose profits can be used to give bursaries to deserving students. Further, schools should utilize the available resources cost-effectively.

2025-01-01T00:00:00Z Kawinzi, Jeremiah M. https://repository.seku.ac.ke/handle/123456789/7731 2025-01-31T08:53:35Z 2024-01-01T00:00:00Z

Institutional determinants of strategic plan implementation in public secondary schools in Machakos County, Kenya Kawinzi, Jeremiah M. Strategic plan as a management tool can help to improve the performance of an organization since it guides all stakeholders to work towards the same objectives. It also makes an organization adapt to the ever changing environment toward realizing better results. This study sought to investigate the influence of institutional determinants of strategic plan implementation in public secondary schools in Machakos County, Kenya. The specific study objectives sought to establish the influence of school structure, resource allocation, leadership communication strategies, and the stakeholders’ participation in school development plans on the strategic plan implementation. The study used descriptive survey research design. The study targeted 351 public secondary schools, 351 principals in these schools, and 3,159 class teachers and academic Heads of Departments. The study used a sample of 30% of all the targeted principals and 10% of the targeted HoDs and class teachers from each zone to arrive at 105 principals, and 316 academic HoDs and class teachers. Public secondary schools in Machakos County were grouped into eight zones (strata) using the stratified sampling technique. The study used open-ended questionnaire to obtain qualitative data and closed-ended questionnaires to obtain quantitative data. Descriptive statistics that is distribution of responses, measures of variability and measures of central tendency were used to analyze data which was presented using frequency distribution tables, and pie charts. Multiple linear regression was used to analyze the inferential data. Qualitative data gathered using open-ended questionnaires was grouped into themes based on the study objectives. The study tested four hypotheses each at a 0.05 level of significance. From the first objective, the study gave a positive coefficient of 0.0470 on school structure with a p-value of 0.314 and was not statistically significant at 0.05 level, hence we fail to reject the null hypothesis that, school structure had no influence on strategic plan implementation. Based on the second objective, the study produced a positive coefficient of 0.4168 on school leadership with a p-value of 0.000 which was statistically significant at the 0.05 level, hence we reject the null hypothesis that, school leadership had no influence on strategic plan implementation. In the third objective, the study produced a negative coefficient of -0.0168 on resource allocation with a p-value of 0.714 which was not statistically significant at the 0.05 level, hence we fail to reject the null hypothesis that, resource allocation has no influence on strategic plan implementation. The findings from the fourth objective produced a positive coefficient of 0.2519 on stakeholder participation in school development plans with a p-value of 0.000 which was statistically significant at 0.05 level, thus we reject the null hypothesis that, stakeholder participation in school development plans has no influence on strategic plan implementation. From the study findings, the study concluded that institutional leadership and stakeholders’ participation in institution development plans have a statistically significant influence on strategic plan implementation; however institutional structure does not have a statistically significant influence on strategic plan implementation even though school structure is positively and significantly related to strategic plan implementation, in addition, institutional allocation of resources had no statistically significant influence on strategic plan implementation in public secondary schools in Machakos County. Based on these findings, the study recommends that the school Principals ought to make sure that there is clarity in co-coordinating the curriculum, and stakeholders’ need to honor the invitation to participate in the school development plans in the strategic plan. Doctor of philosophy in economics of education and planning, 2024

2024-01-01T00:00:00Z