Faculty of Science

Permanent URI for this collectionhttp://172.16.31.117:4000/handle/123456789/45

Browse

Now showing 1 - 20 of 292

ASSESSMENT OF Plasmodium falciparum RESISTANCE TO PIPERAQUINE AND OTHER FRONTLINE ANTIMALARIALS IN KENYA USING GENOMIC ANALYSES AND GROWTH INHIBITION ASSAYS
(Egerton University, 2023-11) WAKOLI MUSAMALI DANCAN
Dihydroartemisinin-piperaquine (DHA-PPQ) is an alternative first-line antimalarial to artemether- lumefantrine in Kenya. However, recent reports on emergence of PPQ resistance in Southeast Asia threaten its continued use in Kenya and Africa. In line with the policy on continued deployment of DHA-PPQ, it is imperative to monitor susceptibility of Kenyan parasites to PPQ and other frontline antimalarials in order to clarify its field expedience at this period of intensified deployment. Parasites isolates from samples collected between 2008 and 2021 from individuals with naturally acquired P. falciparum infections presenting with uncomplicated malaria were tested for in vitro susceptibility to piperaquine, dihydroartemisinin, lumefantrine, artemether, and chloroquine using the malaria SYBR Green I method. A subset of the 2019-2021 samples was further tested for ex vivo susceptibility to PPQ using piperaquine survival assay (PSA). Each isolate was also characterized for mutations associated with antimalarial resistance in Pfcrt, Pfmdr1, Pfpm2/3, Pfdhfr, and Pfdhps genes using real-time PCR and Agena MassARRAY platform. Associations between phenotype and genotype were also determined using the Kruskal-Wallis H- test and Mann-Whitney U test. The PPQ median IC50 interquartile range (IQR) remained stable during the study period, 32.70 (IQR 20.2-45.6) nM in 2008 and 27.30 (IQR 6.9-52.8) nM in 2021, (P=0.1615). The median ex vivo piperaquine survival rate (IQR) was 0 (0-5.27) %, at 95% CI. Five isolates had PSA survival rate of ≥10%, consistent with the range of PPQ resistant parasites, though they lacked polymorphisms in Pfmdr1 and Plasmepsin genes. Lumefantrine and artemether median IC50s rose significantly to 62.40 (IQR 26.9-100.8) nM, (P = 0.0201); 7.00 (IQR 2.4-13.4) nM, (P = 0.0021) in 2021from 26.30 (IQR 5.1-64.3) nM; 2.70 (IQR 1.3-10.4) nM in 2008, respectively. Conversely, chloroquine median IC50s decreased significantly to 10.30, (IQR 7.2- 20.9) nM in 2021 from 15.30 (IQR 7.6-30.4) nM in 2008, coinciding with a decline in prevalence of Pfcrt 76T allele over time from 39.3% to 0% (P = 0.0357). The proportions of piperaquine- resistant markers including Pfpm2/3 and Pfmdr1 did not vary significantly. However, a significant association was observed between PPQ IC50 and Pfcrt K76T allele (P=0.0026). Circulating Kenyan parasites have remained sensitive to PPQ and other antimalarials, though response to artemether and lumefantrine is declining. This study forms a baseline for continued surveillance of current antimalarials for timely detection of resistance.
INTERVAL ESTIMATION FOR A TWO-PARAMETER WEIBULL DISTRIBUTION BASED ON TYPE-2 CENSORED DATA
(Egerton University, 2024-04) MASILA, MWELELI RAPHAEL
In most occasions, when performing life testing experiments, the main interest is to examine the lifespan of a specimen. For example, the time an aircraft wing takes until it fails from metal fatigue, or the survival time of a patient after a kidney transplant. In practice, such life data is usually censored because one does not have sufficient resources in terms of money and time. Type-2 censoring is one of the most popular censoring schemes used in reliability and life testing experiments. Weibull distribution is the most preferred distribution to fit censored life data because it is versatile and able to take on characteristics of other types of statistical distributions based on the value of the shape parameter. The maximum likelihood method is applicable for obtaining ML estimates (MLEs) for parameters of the 2-parameter Weibull distribution. Once the parameter point estimates have been obtained, construction of confidence intervals and confidence regions can be performed. In previous research works, construction of approximate confidence intervals based on Wald method under type-2 censoring scheme has been done. However, these confidence intervals may not be accurate for small sample sizes. The profile-likelihood method can be used to construct approximate confidence intervals for the parameters of interest when the sample size is small. In this study, the approximate profile-likelihood confidence intervals and likelihood confidence region are constructed for parameters of the 2-parameter Weibull distribution based on small type-2 censored samples. The study employed both simulated and real data sets. Subroutines for construction of profile- likelihood intervals were developed in 𝑅 program (version 3.5.1). Approximate profile-likelihood confidence interval results were then compared with the Wald confidence intervals using confidence lengths and coverage probabilities. Most of the coverage probability results for the parameters associated with the Wald method were relatively unstable because they were below the nominal coverage probability (0.95). On the other hand, most of the coverage probabilities associated with the profile-likelihood method were relatively close to the nominal coverage probability (0.95). The Profile-likelihood method outperformed Wald method because the confidence lengths obtained using profile-likelihood technique were narrower as compared to those associated with Wald method. Finally, Profile-likelihood interval estimates obtained in this study using small type-2 censored data can be used to make better inferences in life-testing experiments by using an effective small sample size.
SOURCE ROCK EVALUATION OF TOTAL ORGANIC CARBON, MINERALOGY, AND ALIPHATIC HYDROCARBON BIOMARKERS (THE ANZA BASIN, KENYA)
(Egerton University, 2024-08) CHESIR, CHEMUTAI LORNA
One of the essential steps in hydrocarbon exploration and exploitation is to understand the association of organic matter and minerals in petroleum reservoirs which is a vital component of the hydrocarbon-generation process. Understanding how and where hydrocarbons origi- nated, helps to comprehend and predict where they can be discovered, particularly in uncon- ventional reservoirs such as source rocks. The purpose is this study is to characterize the or- ganic matter content of seven source rocks collected from three wells (Chalbi-3, Sirius-1, and Ndovu-1) located in the Anza Basin in the north eastern part of Kenya. These were character- ized using: (i) elemental (CHN) analysis for organic matter components; and (ii) X-ray diffrac- tion (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), scan- ning electron microscopy (SEM-EDX), thermogravimetric and differential scanning calorime- try (TG/DSC) for mineralogical characterization, and gas chromatography-mass spectrometry (GC-MS) analysis for saturated aliphatic biomarkers. This evaluation revealed, for all the wells and the depths studied, the source rocks have TOC values of 0.54%, 1.46%, 1.54%, and 1.99 % for Sirius-1, Chalbi-3, and Ndovu-1, respectively. The high quartz content coupled with a fair to good %TOC content, and low H/C values, have demonstrated the potential of the source rocks as being good and capable of oil and/or gas expulsions from the wells. High organic richness has been measured in each source rock sample. The XRF, XRD, and FTIR results revealed that the source rocks were comprised mainly of quartz, followed by silicate-clay min- erals and calcite minerals. While Thermogravimetric Analysis (TG/T∆G) and Differential Scanning Calorimetry (DSC)–under a controlled (O2/air) oxidizing atmosphere and at a heating rate of 10 °C min−1, showed there was a strong correlation between TG and DSC, and that for both processes, the source rocks underwent thermal decomposition in three steps. In addition, solvent-extractable organic matter investigation revealed a unimodal distribution of bi- omarkers: n-alkanes and isoprenoids (low pristane/ phytane ratios). Thus, the hydrocarbons in the source rocks were derived from algae and bacteria, which had been deposited under weakly anoxic and low oxic environmental conditions with least contributions from terrestrial organic matter sources. Hydrogen Indices are low (HI= H/C: 0.19–0.60 atomic ratios), indicating a predominance of mixed type III/IV (oil/gas-prone). The drilled well depths (1066-3100 m) demonstrated good reservoir rock properties with fair to good hydrocarbon generation potential (TOC values between 0.5–2%) with the existence of commercial hydrocarbon production.
ORGANIC CONTAMINANTS AND HEAVY METAL ANALYSIS IN THE GROUNDWATER OF KERIO VALLEY WATER BASIN, BARINGO COUNTY, KENYA
(Egerton University, 2024-06) LANGAT, KIPKEMOI FESTUS
Many harmful effects of human activities below the surface of the earth have a negative impact on groundwater quality, as many mineral- and oil-rich places can attest to. The impacts may include enhanced risks of cancer and genetic aberrations. Therefore, research on the determination of physico-chemical characteristics, heavy metals and organic pollutants in groundwater from boreholes of Kerio Valley water basin near commercial oil exploratory wells is fundamental. A solid phase extraction technique was used to extract water samples from specific boreholes in the Kerio Valley water basin of Baringo County. The water samples were then analyzed for organic contaminants using a gas chromatograph interfaced with a mass spectrograph detector. Out of the 4 boreholes sampled, 3 contained benzene derivatives, mainly xylene, 1,3,5-trimethylbenzene, 1-ethyl-3-methylbenzene, 1-methyl-2-propylpentylbenzene, and polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, fluoranthene, azulene, and pyrene. Furthermore, long-chain hydrocarbons were found in varied quantities in all groundwater samples. Benzene derivative concentrations ranged from 2.84 ± 1.04 to 20.47 ± 1.53 ppm. However, polycyclic hydrocarbons exhibited the highest concentrations of all organic pollutants, with pyrene giving a concentration of 23.14 ± 2.05 ppm, fluoranthene (18.54 ± 1.89 ppm), phenanthrene (14.13 ± 1.60 ppm) and anthracene (12.72 ± 1.20 ppm). In accordance with the results, 3-methyl-2,3-dihydro-1-benzofuran predominated in all samples, with concentrations ranging from 0.070 ± 0.28 to 9.390 ± 1.12 ppm compared to 0.28 ppm WHO permitted limits. Heavy metals were analysed in groundwater samples using atomic absorption spectroscopy (AAS). The results showed that the boreholes have remarkably high concentrations of lead, cadmium, and chromium. Interestingly, Pb was found to have a concentration profile ranging from 0.26 ± 0.01 to 10.76 ± 0.22 ppm, Cd ranges from 0.22 ± 0.01 to 0.29 ± 0.03 ppm, Mn posting high concentration of 1.86 ± 0.04 ppm in KV8 water sample, while Cr concentration ranged from 0.09 ± 0.002 to 0.37 ± 0.03 ppm. According to the results of this study, borehole water in the Kerio Valley basin is contaminated and may be hazardous for human consumption. The reported concentration levels were several times greater than the guidelines of the United States Environmental Protection Agency (USEPA) and the World Health Organization (WHO). Consequently, it is vital to establish a policy framework for the assessment and monitoring of water quality in the region, as well as propose intervention methods to assure a clean water supply for the well-being of inhabitants of the Kerio Valley water basin.
INVESTIGATION OF ANTIMICROBIAL AND NEMATICIDAL ACTIVITY OF SECONDARY METABOLITES FROM Armillaria SPECIES
(Egerton University, 2024-08) CHEPKEMOI, JACKLYNE
Infectious diseases caused by pathogens are the leading cause of death for both adults and children. These diseases are responsible for 18.4 % fatalities worldwide. The widespread of the infectious diseases caused by these pathogens arises due to antimicrobial drug resistance. Plant- parasitic nematodes are responsible for approximately 80% of vegetable output loss in Kenya. They have also caused havoc on agriculture throughout the world, jeopardizing agriculture's long-term viability. Currently, control of nematodes relies on synthetic nematicides, which unfortunately causes environmental and ecological pollution and threatens human health. The development of antimicrobial drug resistance and the safety hazards of synthetic nematicides have triggered a great research effort towards natural products. In this study, antimicrobial and nematicidal activities of bioactive secondary metabolites from Desarmillaria ectypa (MUCL 31078), A. gallica (STMA 12242) and A. mellea (STMA 12328) were studied. The three fungal strains were obtained from Helmholtz Centre for infection research (HZI). Subculturing was done on YM 6.3 media and fermented on rice and Q61/2 media. The metabolites from Q61/2 media were extracted with Ethyl acetate solvent and ethyl acetate crude extract was obtained. The metabolites from rice media were extracted with methanol solvent and methanol crude extract was obtained. The methanol extract was subjected to liquid-liquid partitioning using hexane and ethyl acetate solvents where hexane and ethyl acetate crude extracts were obtained. The ethyl acetate crude extracts from rice and Q61/2 media were then purified using Prep-high performance liquid chromatography. Nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry was used to obtain the structures of the pure compounds. One new compound, (3) alongside four known compounds, armillaridin (1), arnamiol (2), diatretol (4) and 3-chloro-6-hydroxy-4-methoxy-2-methylbenzoic acid (5) were isolated from D. ectypa. The known compounds, 5’-O-methylmelledonal (6), Melledonal C (7), 10α-hydroxydihydromelleolide (8) and melledonal (9) were isolated from A. mellea. Lepistamide B (10), which is also a known compound was isolated from A. gallica. The compounds were tested for antimicrobial and nematicidal activity in which a weak activity was observed against S. aureus (ATCC 25923) and E. coli (ATCC 25922). The compounds did not show nematicidal activity. Armillaridin (1) was active against Mucor hiemalis (DSM 2656) at 33.3 μg/mL and Bacillus subtilis (DSM 10) at 8.3 μg/mL. The study provides potential leads of antimicrobials from Armillaria species.
WO-STAGE NEGATIVE BINOMIAL GROUP TESTING MODEL FOR ESTIMATING PREVALENCE OF A RARE TRAIT
(Egerton University, 2023-09) KARIUKI, MWANGI FRANCIS
Group testing is an economical screening strategy that is beneficial in terms of efficiency and cost-cutting. The idea dates back to World War II, and it entails amalgamating individual specimens into pools that are tested for the presence of a trait of interest. Since its inception, group testing literature has branched into two research areas: classification and estimation. Research work in group testing has concentrated on designs without errors and has mainly developed under the binomial model. However, a combination of inverse sampling and group testing has been established to be useful when there is a need to report estimates early in the screening process. The main focus under the negative binomial group testing designs has been to develop more efficient estimators and to determine optimum group sizes under the assumption that the testing process has no misclassification. However, errors associated with labelling, and misclassification are prone to occur in an experimental design. Retesting of pools has been established to improve the efficiency of an estimator and increase the precision of a test. This research has constructed and analyzed a two-stage negative binomial group testing model for estimating the prevalence of a rare trait when imperfect tests with known sensitivity and specificity are used. The study utilized the Maximum Likelihood Estimation (MLE) method to obtain the estimator and the Cramer-Rao bound method to compute the Fischer information of the estimator. The properties of the constructed estimator were examined. The efficiency of the constructed estimator relative to other estimators in pool testing designs was determined by computing the Asymptotic Relative Efficiency (ARE) and the Relative Mean Squared Error (RMSE). The procedure was illustrated, and the model was verified by performing Monte Carlo simulations using R programming language version 3.5.2. The research findings showed that the model was superior to the one-stage negative binomial group testing model with misclassification as low variances were obtained as the proportion p increased. Also, the constructed estimator performed more efficiently for higher values of p. Furthermore, the study can be used for surveillance of pathogens and monitoring the prevalence of infectious diseases such as the Coronavirus disease 2019 (COVID-19) to prevent another pandemic resurgence.
TWO-STAGE ADAPTIVE NEGATIVE BINOMIAL GROUP TESTING MODEL FOR ESTIMATING THE PREVALENCE OF A RARE TRAIT
(Egerton University, 2024-04) AKOMBOH JACKLINE ONGECHA
Group testing has been found to be an efficient and economical way of classifying observations under study as defective or unsatisfactory depending on the test performed as well as estimating the prevalence rate of a trait in a population. However, groups of appropriate sizes should be used to realize these benefits. Adaptive schemes have been developed to counter the problems brought about by inappropriate choice of group sizes. The available adaptive schemes have been constructed using a binomial sampling model where the number of groups to be tested is fixed, implying that all groups must be tested before recording the number of successes. But in some situations, such as the case of infectious diseases, estimates need to be reported as soon as detection is made, and for that case, the Negative Binomial (NB), sampling model is preferred. Under NB model, the testing procedure stops immediately when the desired number of successes, which is fixed prior, is attained. This study constructed a two-stage adaptive NB group testing model for estimating the prevalence of a rare trait. The adaptation adjusts group sizes from one stage to the next based on the estimate obtained from the previous stage. The group size used in each stage was the optimal one that minimizes the variance of the estimate of the prevalence rate in the previous stages. The maximum likelihood estimation method was used to find the point estimate of the parameter of the developed model and its properties investigated. The study further constructed the Wald confidence intervals, and its performance was investigated using mean interval length. The developed model was compared to the non- adaptive group testing model existing in the literature using relative mean squared error (RMSE) and asymptotic relative efficiency (ARE) to identify the best model. R-programming language version 4.1.2 was used for Monte Carlo simulation and analysis to verify the model. The use of the two-stage adaptive NB model combined with MLE provided lower and precise estimates. The comparative analysis highlighted the superiority of the adaptive model over the non-adaptive model emphasizing the importance of incorporating adaptivity in group testing procedures. The study highly recommends leveraging these findings to enhance the efficiency and reliability of group testing methods across diverse applications, including disease screening and surveillance of viral illnesses such as Covid-19. By incorporating these findings, the effectiveness of this testing strategies can greatly be improved, leading to more accurate and timely identification of infections, ultimately contributing to better public health outcomes.
SUITABILITY OF REDWORMS, (Eisenia foetida) AS PROTEIN INGREDIENT OF FISH FEEDS FOR NILE TILAPIA AND AFRICAN CATFISH IN GREENHOUSE AND OPEN POND AQUACULTURE SYSTEMS
(Egerton University, 2024-01) AMUYUNZU, AKIDIVA ALEX
This study assessed the suitability of redworms as a protein ingredient in fish feeds. Furthermore, the study evaluated the use of greenhouse technology to promote aquaculture of warm water fish species in high altitude areas characterized by low temperatures below optimum range of 25 to 33˚C. The study was conducted at the Agro-Science Park’s Fish Farm in Egerton University from January to June 2017. A total of 240 catfish and 240 monosex male tilapia fingerlings were stocked in 30 hapa nets in greenhouse and 30 hapa nets in open pond at a rate of 8 fingerlings per net. Redworms were cultured for use in feed formulation. Two isonitrogenous diets containing 35% and 40% were formulated for tilapia and catfish respectively using redworms and fish meal as animal protein ingredients. Five redworm experimental diets containing 0:100%, 25:75%, 50:50%, 75:25% and 100:0% redworm and fish meal were formulated and fed to fish twice daily at 3% body weight. Selected physico- chemical parameters; temperature, conductivity, dissolved oxygen and pH were monitored daily while nutrients; nitrites, nitrates, ammonia, soluble reactive phosphorus and total phosphorus were analyzed monthly. Fish were sampled every fortnight to determine the Absolute Growth, Specific Growth, Food Conversion Ratio, Length Weight Relationship, and condition factor. There was no significant difference in the mean protein content of redworm meal 62.29±1.13 and fish meal 57.71±0.77 (t-test, df=1, p > 0.05). Similarly, there was no significant difference in mean lipid content of redworm (6.34±0.48) and fish meal (5.51±0.19). Temperature varied significantly in the two pond systems (t-test, p<0.05). There were significant differences in the Specific Growth rate, Absolute growth and mean weight gain of Nile tilapia and African catfish cultured in greenhouse and open pond systems (t-test, df=1, p < 0.05). Fish cultured in greenhouse pond had higher mean weight gain than those in the open pond system. However, there were no significant differences in the specific growth and Absolute growth rates of fish fed on the 5 redworm experimental diets (One Way ANOVA, df ꞊ 4, p ꞊ 0.071). Fish fed on diet containing 50% redworm diet gained highest weight. Nile tilapia and African catfish cultured in greenhouse pond had condition factors of 2.15 and 3.62 respectively while values of 0.87 and 0.88 in the open pond indicating isometric and allometric growth in greenhouse and open ponds, respectively. Calculated Food conversion ratio indicated that both experimental diets were efficiently utilized in greenhouse pond compared to the open pond. Therefore, this study recommends the use of redworm meal as an alternative protein ingredient and use of greenhouses in improving the growth rate of warm water fish species in aquaculture.
DENSITY FUNCTIONAL THEORY STUDY OF STRUCTURAL, MECHANICAL, ELASTIC ANISOTROPY, LATTICE DYNAMICS, AND ELECTRONIC PROPERTIES OF NICKEL AND PALLADIUM BASED HEUSLER ALLOYS
(EGERTON UNIVERSITY, 2025-09) LUKORITO,TINDIBALE EDWARD
This study explores the structural, mechanical, elastic anisotropy, lattice dynamics, and electronic properties of nickel and palladium based Heusler compounds for thermoelectric (TE) applications. Current energy sources such as fossil fuels have been crucial in supplying the world's needs, however, they face certain difficulties such as greenhouse gas emissions. The availability of thermal energy in the form of waste heat has drawn attention to the TE energy conversion process. Low efficiency and thermal stability are still problems for several energy-conversion materials that exploit different varieties and compositions in their alloys. These challenges are linked to the physical properties of energy-conversion materials and the kind of contact electrode that enhances the performance of TE devices. The compounds investigated in this study belong to Heusler alloys with designations including half and full Heusler. Computations were performed using density functional theory (DFT) as implemented in the Quantum ESPRESSO (QE) code. For the exchange-correlation functional, the generalized gradient approximation (GGA) was used, while the projected augmented wave method (PAW) was used for electron-ion interaction. Optimized lattice constants for all compounds investigated agree with available experimental and theoretical values in the literature. The lattice parameter mismatch for HfNiSn/HfNi2Sn, ZrNiSn/ZrNi2Sn, and TiNiSn/TiNi2Sn compounds was minimal, ranging between 2.5 % and 3 %. Mechanical properties indicated that nickel-based half Heusler compounds were brittle except for ZrNiSi and TiNiSn, which were ductile. Additionally, ductile behavior was noted in palladium based half Heusler and nickel based full Heusler compounds. Elastic constants were found to satisfy the general conditions for stability for cubic symmetry, except for TiNi2Ge. Based on anisotropies in sound velocities in the [111], [110], and [100] crystal directions, anisotropy indices, and directional surfaces, all compounds exhibited anisotropic character. Lattice dynamics properties showed that, with the exception of TiPdGe, half-Heusler alloys and full Heusler compounds of TiNi2Sn, TiNi2Si, ZrNi2Sn, and HfNi2Sn were dynamically stable. The electronic properties for nickel-based compounds showed that HfNiSn, ZrNiSn, and TiNiSn compounds have the least indirect energy gaps of 0.3847 eV, 0.5019 eV, and 0.4508 eV respectively. Among the palladium-based compounds, TiPdSn, ZrPdSn, and HfPdSn recorded narrow energy band gaps of 0.4804 eV, 0.4747 eV, and 0.3815 eV, respectively. The findings of this work offer theoretical guidance for improving the performance of TE materials and devices that can significantly contribute to clean energy solutions, hence aligning with the global shift towards sustainable energy practices.
BENZENE DERIVATIVES AND SPECIATION OF SELECTED TRACE METALS IN LAKE BOGORIA GEOTHERMAL SYSTEM, KENYA AND HEAVY METAL ANALYSIS IN NYAMNYUMABA AND BUGARAMA HOT SPRINGS OF RWANDA
(EGERTON UNIVERSITY, 2025-10) SUNGUTI ANZELIM ELIWA
Geothermal energy is a renewable and environmentally friendly resource that has gained traction in the recent past as an alternative source of energy to the fast-depleting fossil transport fuels. Nonetheless, research on the presence of trace metals and organic pollutants in geothermal water and steam is scarce in literature. This current study dealt with the examination of geochemical properties of geothermal springs in Lake Bogoria. During the analysis, quantification of poly alkyl benzenes was carried out using Gas Chromatography Mass Spectrometry (GC MS) and the results showed the presence of poly alkyl benzenes with a mean value of 0.37 ± 0.28 ppm, which is below the United States Environmental Protection Agency (US EPA) limit for most alkyl benzenes. Trace amounts of naphthalene were also detected in some samples. The trace metals – Mn, Cd, Pb, Cu and Ni were analysed using Atomic Absorption Spectroscopy (AAS). Statistical treatment of data was carried out using Pearson’s Correlation Coefficient (PCC), Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The mean concentrations of Mn, Cu and Ni were found to be 0.19 + 0.08 ppm, 0.02 + 0.02 ppm and 0.03 + 0.02 ppm, respectively, values that are below the permissible World Health Organisation (WHO) limits. On the other hand, Pb and Cd showed mean concentrations of 0.06 + 0.04 and 0.05 + 0.02 ppm, correspondingly, values that are above the WHO limits. A related geochemical survey of Rwandan geothermal sites was also done, and it focused on investigating the presence of select trace metals (Pb, Cd, Mn, Ni and Cu) in Nyamyumba and Bugarama hot springs in the Western Province of Rwanda. The trace metals were determined using Micro Plasma Atomic Emission Spectroscopy (MP-AES). The mean concentrations of Cu in both Nyamyumba and Bugarama were found to be 0.1 ppm, which is within the permissible World Health Organisation (WHO) limits for potable water. Similarly, the concentrations of Mn were within the acceptable WHO limits with mean concentrations of 0.04 ± 0.02 and 0.11 ± 0.03 ppm in Nyamyumba and Bugarama, correspondingly. Lead was found to be beyond the WHO limits with mean results of 0.01 and 0.013 ± 0.01 ppm in Nyamyumba and Bugarama, respectively. Cadmium mean concentration was 0.01 ppm in both areas, which is above the permissible WHO limit. Nickel was below the detection limit. It is envisaged that the research findings of this study will enhance the scientific understanding of the geochemistry of the geothermal springs in the respective areas of study for their future efficient and sustainable exploitation as alternative green energy resources.
ASSESSMENT OF FISH SPECIES COMPOSITION USING ENVIRONMENTAL DNA METABARCODING AND CATCH SURVEY IN THE SATELLITE LAKES OF LAKE VICTORIA, KENYA
(EGERTON UNIVERSITY, 2025-09) OCHINGO, JARED JOAB
The satellite lakes of Lake Victoria are identified as key refugia for native fish species, most of which are threatened by factors such as invasive species and habitat loss. Nevertheless, fish species composition in these lakes are understudied, which drastically hampers fisheries management and conservation measures. This research applied both molecular (eDNA metabarcoding) and conventional methods through catch surveys to identify the fish species composition in Lakes Kanyaboli, Namboyo, Sare, and Bob. The morphometrics, DNA tissues, and questionnaire data were collected twice a month from November 2024 to February 2025. The Total Length (TL) and total weight (TW) of the fish were measured using a measuring board and an analytical balance, respectively. The eDNA and tissue samples were transported to SPYGEN Laboratory (France) for sequencing and bioinformatics analysis. A total of 95 fishermen were interviewed across the satellite lakes. 37.8% and 33.3% of fishermen in Kanyaboli and Bob, respectively, were in the age range of 30-39 years. The eDNA metabarcoding detected 31 taxa, while the catch survey recorded 21 taxa. Shannon Weiner diversity indices showed that Lakes Namboyo and Bob recorded the highest diversity, 1.64 and 1.43, respectively. Kanyaboli 1.3 and Lake Sare recorded the least diversity, 0.73, based on eDNA metabarcoding. Common species detected include the tilapiines, C. gariepinus, and P. aethiopicus. Two invasive species, Gambusia sp and Lates niloticus, and five haplochromine species (Pundamilia nyererei- found in all four lakes, Pundamilia pundamilia- found in all lakes except in Sare, Haplochromis maxillaris, Astatotilapia nubilus and Haplochromis argenteus were found in Kanyaboli. One-way Analysis of Variance (ANOVA) indicated significant differences between the total weight in all the lakes (p=0.001). The length-weight relationship of O. niloticus in Lakes Kanyaboli, Sare and Bob showed an isometric growth pattern (b=3), O. leucostictus and O. esculentus in Kanyaboli showed a negative allometric growth (b<3), O. leucostictus in Sare revealed a positive allometric growth (b=3.2), and O. variabilis in Sare had an isometric growth (b=3). Both C. gariepinus and P. aethiopicus across the four lakes showed a negative allometric growth with (b<3). The condition factor (K) and the Relative condition factor (Kn) were all above 1.0, indicating that the fish were in good condition across all the lakes. The study demonstrates the effectiveness of eDNA as a tool for fish biodiversity assessment in the satellite lakes. The findings will benefit fisheries officers, Researchers, policymakers and local communities by guiding conservation strategies and ensuring sustainable use of these aquatic ecosystems.
ASSESSMENT OF SUSCEPTIBILITY OF GARDEN PEA (Pisum sativum L.) VARIETIES TO ASCOCHYTA BLIGHT AND EVALUATION OF EFFICACY OF CHEMICAL AND BIOLOGICAL (Trichoderma spp.) FUNGICIDES IN NAKURU COUNTY, KENYA
(EGERTON UNIVERSITY, 2025-06) OMWANSA, OMWENGA DANIEL
Garden pea (Pisum sativum L.) is a nutritionally and economically important legume widely cultivated for its high protein content and nitrogen-fixing capability. However, its productivity is significantly constrained by Ascochyta blight, a fungal disease favoured by cool and moist conditions. This study aimed to evaluate the susceptibility of four garden pea varieties; Nano Progress 9 (Grano), Peas Plum, Peas Kelvedon, and Peas Greenfeast to Ascochyta blight, and to assess the efficacy of selected chemical fungicides (mancozeb, chlorothalonil, benomyl, and carbendazim) and the biocontrol agent Trichoderma harzianum in disease management under field and laboratory conditions in Nakuru County, Kenya. Field trials were conducted in Molo Sub-county using a Randomized Complete Block Design (RCBD) with ten replicates, where soil fertility served as the blocking factor. Laboratory experiments followed a Completely Randomized Design (CRD). Data were analysed using two-way ANOVA for field data, and one-way ANOVA for laboratory data. Means were separated using Fisher’s Least Significant Difference (LSD) test. Although varietal differences in disease severity were observed, they were not statistically significant (p = 0.107), with Peas Nano Progress 9 exhibiting marginally lower severity compared to Peas Plum, Peas Kelvedon, and Peas Greenfeast. All tested fungicides significantly reduced disease severity compared to untreated controls (p < 0.001), with chlorothalonil showing slightly higher efficacy. In vitro dual culture assays demonstrated that Trichoderma harzianum significantly inhibited the growth of Ascochyta pisi, achieving a 90.9% reduction in radial colony diameter (p = 0.001). These results highlight the effectiveness of chemical fungicides and the potential of T. harzianum as a biocontrol agent. However, the limited resistance among varieties underscores the need for breeding programs targeting disease-resistant cultivars. Further research is recommended to validate the efficacy of T. harzianum under field conditions and to explore broader genetic resources for resistance breeding in garden pea varieties. Determination of resistant garden pea varieties coupled with synthetic fungicides and T. harzianum warrants further research, as it presents a promising approach for the sustainable management of Ascochyta blight disease in garden pea.
NUTRITIVE VALUE OF Arthrospira platensis, (Gomont, 1892) AND Oocystis sp. AS PROTEIN SOURCES IN NILE TILAPIA FISH FEEDS
(EGERTON UNIVERSITY, 2023-04)
Fish farming is a rapidly developing industry globally due to the increasing demand on protein for feeding the rapidly increasing human population. On the other hand, capture fisheries have significantly declined. One major impediment to aquaculture is access to affordable fish feeds, due to the expensive crude protein component. To address this challenge, this study investigated the potential of two algal species: Arthrospira platensis, and Oocystis sp. as sources of crude protein in fish feeds. The objectives of this study were to establish the most appropriate fertilizer regime that would allow for the optimum Oocystis sp. growth to generate adequate biomass, formulate fish feeds from the two algal species, analyse their proximate composition, and determine their efficiency in the growth of Oreochromis niloticus. Two experimental set-ups were made in the study, the first set-up involved the culturing of Oocystis sp., and determining its biomass and crude protein contents. The growth rate, doubling time, and divisions per day were determined from the changes in chlorophyll-a concentration. Proximate analysis was done on subsamples of Oocystis sp. and A. platensis. The second experimental set-up involved the assessment of the performance of O. niloticus fed on seven formulated diets namely, diet 1 was the control with Caridina nilotica as the protein source and the other six diets had 10%, 20%, and 40% replacement of C. nilotica with Oocystis sp. (diet 2-diet 4), and A. platensis (diet 5-diet 7). To achieve this, a ten-week experiment was conducted at the Agro-science Fish Park at Egerton University, where 21 hapa nets, each containing of 30 O. niloticus fry were subjected to the seven diets in triplicates. The results of the first experiment showed that there were no significant differences in the mean Oocystis sp. biomass (p> 0.05), growth rate (p> 0.05), divisions per day (p> 0.05), and doubling time (p> 0.05) from the different treatments. The overall body weight of the fish increased significantly (p < 0.05) from 0.240 g to 8.486 g. There were significant differences (p< 0.001) in the final body weight between diet 1 (7.778 ± 0.498 g) against diet 2 (9.985 ± 0.504 g) and diet 5 (9.937 ± 0.366 g). Therefore, this study showed that inorganic fertilizers can be used as cost-effective media in the mass scale culture of Oocystis sp. and that 40% substitution of C. nilotica as a protein source with either A. platensis, or Oocystis sp. enhances the growth of O. niloticus fry and reduces production cost, while having no adverse effects on the growth performance. In conclusion, the study revealed that there is great potential in the use of A. platensis, and Oocystis sp. as protein sources in fish feeds. This study recommends the potential inclusion of A. platensis or Oocystis sp. to lower the cost of production so that aquaculture not only becomes more profitable but contributes to increased food and nutritional security.
Performance of an anisotropic magneto-resistive electrical energy meter
(Egerton University, 2025) Fredrick Macharia Kagucia
Electro-mechanical energy meters provide an excellent combination of simplicity and reliability and have been used for over a hundred years. They only indicate units consumed and need for additional functionalities made the transition to solid-state electrical energy meters a necessity. Most energy meters use traditional current sensors which have shortcomings like thermal drift, limitation of frequency range, cost, size and lack of electrical isolation. In this research an Anisotropic Magneto-Resistive (AMR) current sensor which overcomes the above disadvantages was tested and found to have a linear characteristic suitable for electrical energy metering. A digital electrical energy meter based on the AMR current sensor was designed using Proteus 8 Professional software, basic electronic components and an Arduino micro microcontroller which sampled and processed supply voltage and current signals through a C-code program. The meter displayed accurate output results of supply voltage, current, power factor (pf), „real-time‟ power consumption and cumulative electrical energy (kWh) on a Liquid Crystal Display (LCD). Test-runs lasting 5 minutes were conducted and repeated on electrical loads using the developed AMR meter, Powertek and laboratory multimeters. Analysis of variance was performed on recorded data using Statistical Analysis of Systems (SAS). Means of currents, voltages and pf measured on different meters including the AMR meter were found not to be significantly different at α = 0.05. In one of the test runs, analysis of variance on data from four energy meters gave electrical energy means of 0.1197a, 0.1233a, 0.1233a and 0.1333a. Since the means were followed by the same letters, it implied that the means were not significantly different at α = 0.05 and the performances of the energy meters were therefore similar. The results showed that the AMR meter performed competitively against common domestic electrical energy meters and also displayed more useful information. Although in the performance analysis the error bars overlapped, further study need to be carried out to investigate on how the errors could be reduced at low current loads.
Reducing hydrogen cyanide in cassava based diets to improve grower pig performance in Kenya
(Egerton University, 2025) Mutuyimana valentine
In Kenya, the benefits of pig farming help many households; however, its growth is constrained by the high cost of commercial pig feeds, mainly caused by the constant dependence on maize. Cassava has been identified as a substitute for maize in feeds, however, its elevated levels of crude fibre and the hydrogen cyanide (HCN) contribute to poor nutrient digestibility in animals. This study evaluated the effect of Fermentation and Enzyme Treatment on the nutritional composition, in-vitro digestibility, cyanide reduction of Cassava (Manihot Esculenta) based diets (In a ratio of 1: 0.3; Root: 1; Leaf: 0.3, CRLM), and its impact on grower pig performance. In the first experiment, CRLM was subjected to five treatments: untreated (T1), fermented with Aspergillus niger (T2), spontaneously fermented (T3), enzyme-treated with Natuzyme® (T4), and fermented with Lactobacillus brevis (T5). Nutritional composition, digestibility, were analyzed. What the data reveals is that the optimal treatment was reconfirmed in the following feeding trials. In experiments two and three, 18 Landrace x Large White crosses (20 +/- 3 kg) were allotted three diets; 0% fermented CRLM (T1), 20% FCRLM (T2) and 40% FCRLM (T3). These diets were evaluated for their impact on growth performance, carcass traits and sensory characteristics of the pork. The in-vitro digestibility data, feeding trials and carcass data were all two-way analysed using the ANOVA procedures available in the Statistical Analysis System (SAS, 2023). Differences between means were subjected to Tukey’s test for significance at p < 0.05. In the clinical trial results obtained from the pretreatment phase, it was inconclusive that during the course of spontaneous fermentation (T3) the CRLM quality was improved by the decrease of HCN concentration from 45.00 ppm to 8.00 ppm and CF from 5.16% to 3.87%, and increase in crude protein from 7.47% to 11.09% and dry matter digestibility from 93.67% to 98.62%. The trial results indicated that the feeding of 20% of fermented CRLM resulted in the optimal average daily gain of 0.68 kg/day and the best feed conversion ratio of 4.16, with no detrimental effects on carcass traits and meat quality. These results indicated that spontaneous fermentation substantially increases the nutritive value of CRLM and as such, its use as a feed ingredient for pigs is safe and nutritionally adequate. Incorporating up to 20% FCRLM in grower pig diets can reduce feed costs while maintaining growth performance and pork quality.
Secondary Metabolites from Dovyalis Abyssinica (A. Rich.) Warb Fruits and their Antioxidant Effects
(Egerton University, 2025) Eric Ngutu Muange
One of the main underlying causes of modern diseases is oxidative stress, an imbalance between radicals and antioxidants in living organisms. Its causative agents, unquenched radicals that outnumber antioxidants, remain challenging due to industrialization and modern lifestyles. In humans, these free radicals continue to harm fatty tissues, DNA, and proteins, which results in a multitude of diseases, including cancer, neurological, and cardiovascular diseases. There is, therefore, a need to document and add sources of natural antioxidants. Traditional medicine has long used extracts from D. abyssinica to treat certain human pathogens. Scientific research has demonstrated the efficacy of several secondary metabolites isolated from its leaves, roots, and bark against human infections. However, no investigation on the fruits of this plant has yet been reported. This research, therefore, studied the antioxidant capacities and total phenolic content of fruit extracts of D. abyssinica and isolated three known secondary metabolites from its fruits. Ripe fruits were collected from Egerton University botanic garden, freeze-dried, and ground into fine powder. Solvent extraction was done to obtain hexane, methylene chloride, ethyl acetate, and methanol crude extracts. Samples of these four crude extracts were subjected to the folin-ciocalteu method and DPPH assay to determine their total phenolic content and antioxidant capacities, respectively. The methanol extract gave 921.79 ± 1.63×10-³ mg GAE/100g (mg of gallic acid equivalents per 100g of extract), whereas the ethyl acetate extract gave 517.95 ± 1.4×10-³ mg GAE/100g phenolic content. In contrast, the methylene chloride and hexane extracts gave 261.54 ± 1.0×10-⁴ mg GAE/100g and 24.36 ± 8.2×10-⁴ mg GAE/100g respectively. From these extracts, data on IC50 showed a significant radical scavenging capacity in the methanol extract (4.4 g/mL) than those of ethyl acetate, methylene chloride, and hexane extracts (8.4 g/mL, 28.8 g/mL, and 55.8 g/mL respectively). Subsequently, methanol and ethyl acetate crude extracts were subjected to column, thin layer, and ultimately preparative thin layer chromatographic techniques for separation and purification. 1-D and 2-D NMR spectroscopic analysis revealed three known compounds: betulinic acid (31), sitosterol (32), and 3,4-bis(4-hydroxybenzoyl)-1,5-anhydro-Dglucitol (41), and the compounds are new reports from the fruits of D. abyssinica. This research showed that the studied fruits of D. abyssinica exhibited a substantial phenolic content and antioxidant capacity, providing a source of natural antioxidants and hence contributing to SDGs 2.1 and 3.7 on improved nutrition and well-being promotion.
Bayesian Interval Estimation and Predictive Analysis in a Nonhomogeneous Poisson Process with Delayed S-Shaped Intensity Function
(Egerton University, 2025) Otieno Collins
In the 21st century, software reliability is a significant issue as computers are the most preferred system in almost every global sector. A software is reliable if it can perform its functions for a specified period under specified conditions without causing system failure. A software neither wears out nor burns out and does not fail unless flaws within cause a failure in its dependent system. As such, software reliability testing is performed in the development phase to correct the flaws within the software. Among the non-homogeneous Poisson processes (NHPP) software reliability growth models (SRGMs) proposed and used in software reliability assessment is the Delayed S-shaped model with two unknown parameters 𝛼 and 𝛽, that must be estimated. Most research works have fitted the model to software failure data and obtained point and interval estimates of the unknown parameters using the Maximum Likelihood Estimation (MLE) and Bayesian approaches. However, the construction of Bayesian credible sets for the parameters of this model and the comparison of their accuracy with the traditional Wald confidence intervals based on simulation has not been explored. Predictive analysis on the model has been explored using the Bayesian method with gamma-distributed informative prior. More optimal methods can be developed based on the priors assigned to the unknown parameters to enhance accuracy in modifying, debugging, and determining when to terminate software testing processes. This study introduced a non-informative prior given by 1/αβ and also used 1/α prior existing in the literature and gamma-distributed informative prior to construct Bayesian credible intervals, compare them with Wald confidence intervals using interval lengths and coverage probabilities, and perform predictive analysis. Markov Chain Monte Carlo (MCMC) via Metropolis-Hastings (MH) within Gibbs was used to sample the parameters from their respective conditional posterior distributions. Bayesian approach was also used to address four prediction issues closely associated with software reliability testing. The issues have been outlined as Propositions I, II, III, and IV for the case of non-informative priors, and I.1, II.1, III.1, and IV.1 for the case of the informative prior. The study found that the Bayesian method with gamma-distributed informative and 1/αβ priors yielded more precise interval estimates than the Wald confidence intervals. Moreover, the study developed methods for addressing the outlined single-sample prediction problems and illustrated them using secondary software failure data. The methods developed in this study can be used in software quality assessment.
Role of Cytokines in Varying Trypanosoma Brucei Rhodesiense Infection Outcomes in Vervet Monkeys
(Egerton University, 2025) Clarah Jebet
The clinical manifestations of Rhodesian human African trypanosomiasis (rHAT), which is caused by T. b. rhodesiense, range from acute illness to chronic illness. The basis of this is poorly understood but is suggested to involve host and pathogen factors, and their interaction. Among other factors, host immune factors, including cytokines, play a role which has begun to unravel, and has been shown to vary depending on the host, pathogen species and strain, and mode of infection. These factors have also been suggested to be potential diagnostic biomarkers. With clinical diagnosis important in HAT, understanding the underlying basis of varying infection outcomes is important. In this study, the vervet monkey (Chlorocebus aethiops), a non-human primate (NHP) model of HAT, was employed to investigate the involvement of cytokines in the manifestation of different clinical outcomes of rHAT. The work utilised pathological data along with cryopreserved, archived serum and cerebrospinal fluid (CSF) samples obtained from previously infected animals. Two groups of vervet monkeys were infected with strains KETRI 3801 and KETRI 3928 to represent acute and chronic disease forms, respectively, alongside an uninfected control group. Three animals per group (n=3) for plasma analysis and two animals per group(n=2) for CSF analysis were selected due to limited resources available. Quantities of immune modulators, namely INF-γ, TGF-β, TNF-α, IL-1β, IL-6, IL-10, IL-12, IL-13 and a brain damage biomarker protein, S100B were determined, and pathological data, including survival time, parasitaemia, packed cell volume (PCV), temperature, weight and food intake, were analysed. The levels of individual cytokines showed variations in the course of infection. Levels of IL-12, IL-6 and IL-1β cytokines were significantly increased (p<0.05) from the early stage through to the onset of late-stage disease. Additionally, cerebrospinal fluid (CSF) parasite counts and white blood cell (WBC) levels were higher in KETRI 3801 infections compared to KETRI 3928. IL-12, IL-6 and IL-1β cytokines were particularly higher in acute infection, possibly contributing to the severity of the disease in KETRI 3801 infections, while the interaction between IL-1β, IL-6 and IL-10 played a typical pro- and counter-inflammatory response during infection progression. Fluctuations in parasitaemia were observed in infected animals, with the KETRI 3801 cohort exhibiting a higher parasitaemia (peak antilog 8.7) than KETRI 3928 (peak antilog 7.8). In addition, infected animals had higher febrile temperature, lower body weight and PCV, which these much pronounced in acute as compared to chronic infections. Monkeys infected with KETRI 3801 and KETRI 3928 had a mean survival time of 28 and 95 days, respectively. The findings suggest strain-directed and host-dependent immunomodulation as the basis of the different infection outcomes. Also, cytokines are key regulators of disease progression and severity in the NHP model of HAT, and they are essential for understanding the differences in infection outcomes.
Performance of Improved Indigenous Layer Chicken in Kenya fed on Processed Cassava (Manihot Esculenta Crantz) Root Meal-Based Diet
(Egerton University, 2025) Chelangat Nasta
Cassava (Manihot esculenta Crantz) root meal (CRM) is a readily available and inexpensive feed ingredient in tropical areas; it limits its use in poultry food due to low protein content and hydrogen cyanide (HCN) content. This study compared the impact of enzyme-treated cassava root meal (CRM) on nutrient profiles, productive traits, egg quality, and economic returns in enhanced indigenous layer hens. To determine the impact of the processing technique fermentation (spontaneous, Saccharomyces cerevisiae), and the enzyme treatment on the nutritive value of CRM and the level of hydrogen cyanide, the pre-test was carried out. An experimental feeding was done over 12 weeks in a deep litter house where there were thirty-six chickens, sixteen weeks old. The cage was used to separate the experimental unit with three chickens per square meter, and each treatment was repeated three times. Four iso-nitrogenous and iso-caloric experimental diets were formulated containing 0, 25, 50 and 75% enzyme treated CRM. Data on feed intake, feed conversion ratio, and egg production were collected and subjected to the Analysis of variance (ANOVA) in a completely randomized design (CRD) using the General Linear Model procedure of Statistical Analysis System (SAS) version 9.4 at a 5% significance level. There was no significant difference (p>0.05) in feed intake among the treatments, but the FCR was significantly lower (p<0.05) in the 75% CRM. There was a significant difference (p< 0.05) in egg production among treatments, with a significantly low egg production at 75% CRM. The highest egg shape index was recorded in the 75% CRM diet (73.385, p<0.05), while eggshell thickness was highest in the 50% CRM (0.594 mm, p<0.05). Yolk-to-albumen ratio was highest in the 50% CRM diet (57.420, p<0.05). Economic analysis showed that the 50% CRM inclusion gave the highest economic returns (ROI of 47.7%, CBR of 1.48, and profit of KES 3,681.74 per treatment (3 chicken), p<0.05). In comparison, the 75% CRM inclusion showed the lowest economic returns. It is concluded that a CRM inclusion level of up to 50% is optimal based on feed conversion ratio, percentage egg production, egg quality, and ROI. The study recommended inclusion of up to 50% of enzyme-treated CRM for better sustainability and profitability in improved indigenous layer chicken production.
Synthesis and characterization of silver sulphide-reduced graphene oxide nanocomposite for application in the photoactive and hole transport layers of organic solar cells
(Egerton University, 2025) Oyugi Ngure Robert
The demand for clean energy, occasioned by technological innovations, necessitates sustainable and cost-effective sources such as organic solar cells (OSCs), speciﬁcally bulk heterojunction polymer solar cells (BHPSCs). Inadequate light absorption and charge transport are the common challenges with these sources, which reduce their power conversion efficiency. Incorporating silver sulphide (Ag2S) and reduced graphene oxide (rGO) can improve light absorption and charge carrier mobility, respectively. The study reports successful synthesis, characterisation, and application of Ag;S-rGO nanocomposite (synthesised by chemical reduction method) to enhance the OSCs’ performance. Scanning electron microscopy (SEM) demonstrated the intercalation of rGO sheets within the Ag; S nanoparticles during the chemical reduction process, and that Ag2S had a nanowire shape. Further, SEM energy dispersive X-ray (SEM EDX) showed purity of Ag2S — rGO by indicating C, Ag, O, and S as the only elements in the nanocomposite. X-ray diffraction (XRD) analysis showed sharp and intense diffraction peaks, conﬁnning the high crystallinity of the Ag2S nanoparticles. Thennal gravimetric analysis (TGA) showed rGO slowed nanocomposite decomposition between 520°C and 850°C. AgzS-rGO nanocomposite exhibited strong absorption of light in the ultraviolet and visible regions, making the nanocomposite suitable for use in OSCs. The Fourier Transform Infrared (FTIR) analysis of the nanocomposite showed strong AgzS-rGO interaction with new C-O-C and OH bands, indicating S1lCC€SSfLll integration of rGO into AggS, hence nanocomposite formation. The nanocomposite increased the light trapping of the P3HT: PCBM photoactive layer material within the visible region, improving the efﬁciency of OSCs in light harvesting. For the hole transport layers, however, the higher rGO content slightly reduced the light transmittance due to strong absorbance and plasmonic effects due to Ag2S nanoparticles. All the OSCs with modiﬁed active and hole transport layers (HTL) exhibited improved photovoltaic performance. The nanocomposite in the absorbing layer improved charge generation, leading to increased JSC (from 6.9 mAcm'2 to 17 mAcm'2) and a subsequent enhancement in PCE from 1.5% to 3.4% (a 127% increase). The nanocomposite improved charge collection at the interface, leading to an enhanced PCE by 53% (from 1.5% to 2.3%). The application of Ag2S-rGO nanocomposite considerably improved the performance of the OSCs after application in the HTL and the photoactive layers. Therefore, the study supports the development of sustainable energy solutions.

Browse

Recent Submissions