International Postgraduate Research Conference (IPRC)
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Item Addition of two Trichoderma species with organic fertilizer paste - A boon for crop yield of Abelmoschus esculentus L. cv. MI 5(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Kalpani, N. N.; Kannangara, B. T. S. D. P.; Ratnayake, R. M. C. S.Sustainable agriculture is a farming technique that minimizes environmental impacts while providing a tenable yield. The use of organic amendments as an alternative to inorganic treatments has more significant potential to establish a self-sustaining, less expensive, and environmentally friendly agricultural system. The amalgamation of organic fertilizer with bio-controlling microorganisms is more beneficial than individual application in cropping land to enhance crop productivity. The present study was aimed to examine the influence of an organic fertilizer paste enriched with Trichoderma spp. to enhance the growth performances and yield of Abelmoschus esculentus L. cv. MI 5. The organic fertilizer paste was prepared by aerobic digestion of air-dried and powdered immature twigs of the following plants; Annona glabra, Clidemia hirta, Chromolaena odorata, and Pongamia pinnata (2.0 kg each) in distilled water (42.0 L) for a month. Bio-controlling agents Trichoderma harzianum (KT852821.1) and Trichoderma virens (KP985643.1) were formulated in solid carrier material (compost, straw, clay, and cow urine; 2:1:1:1) separately. The pot trial consisted of six treatments of liquid organic fertilizer enriched with Trichoderma spp. (T10H, T10V, T20H, T20V, T25H, and T25V, where 10, 20, and 25 denote 10%, 20%, and 25% of C. odorata, A. glabra, C. hirta, and P. pinnata extract combined with H as T. harzianum and V as T. virens) with 15 replicates in a completely randomized block design. One-week-old A. esculentus L. cv. MI 5 seedlings were soil treated for 3 months (1st week - 5 mL, 2nd week - 10 mL, 3rd week - 15 mL, 4th week - 20 mL, and 100 mL). The positive and negative controls were commercial fertilizer (Maxicrop) and tap water, respectively. Shoot growth performances, root growth performances, average fresh weights, and average dry weights, and the amount of harvest of A. esculentus L. cv. MI 5 were measured after 3 months of the plantation. One-way ANOVA statistical method, along with Tukey’s multiple comparison tests were used to identify the significant differences (P≤0.05) in growth parameters among treatments using MINITAB (Version 17). T10H treatment (10 % diluted C. odorata, A. glabra, C. hirta, and P. pinnata extract only incorporated with T. harzianum) recorded significantly (P≤0.05), the highest average plant shoot height (163.6±5.40 cm), number of leaves (39±2), stem circumference (5±0.19 cm), average leaf area (309.56±1.2 cm2), root length (38±2.20 cm), the girth of the root (5.24±0.32 cm), number of lateral roots (59±2.08), fresh weight of the entire plant (146.13±16.79 g/plant), fresh weight of the root (35.53±5.82 g/plant), average dry weight of the whole plant (17.61±1.79 g/plant), dry weight of the shoot biomass (13.1±1.42 g/plant), dry weight of the root biomass (4.19±0.09 g/plant), the average number of pods per plant (30±0.24), and average fresh weight of pods (39.83±2.14 g). Therefore, T10H treatment can be successfully used as the best organic fertilizer paste enriched with T. harzianum to enhance the growth and yield of Abelmoschus esculentus L. cv. MI 5.Item Effect of coconut milk on intestinal barrier function and management of oxidative stress(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Ambanpola, N.; Anjali, N. V. P.; Manilgama, T.; Gunawardane, M.; Seneviratne, K. N.; Jayathilaka, N.Coconut milk (CM) is a major source of dietary fat in a Sri Lankan meal. It is rich in saturated, medium-chain fatty acids (MCFA) and various polyphenols. Some of the ingested fats and polyphenols are not absorbed in the small intestine and reach the colon. This study assessed the formation of metabolic products from CM and the influence of CM on intestinal barrier function. Twelve-week-old female Wistar rats were housed at 25 ± 1°C with a 12 h light and dark cycle. Rats were randomly assigned to two experimental groups (12 rats/ group). Ad libitum access to water and a diet containing 4.2 % total fat; from that 3% fat by means of soybean oil (SOD) control or CM (CMD) was provided for four weeks. Six rats from each group fasted for 10–12 h and were treated with ethanol (20%, 6 g/kg body weight) by oral gavage (SODM and CMDE groups were obtained). Blood (1 mL) was then drawn from the tail vein. Plasma antioxidant capacity, lipid peroxidation, and protein carbonyl content were determined by 2,2-diphenyl-1-picryl-hydrazy (DPPH) assay, ferric reducing antioxidant power (FRAP) assay, protein carbonyl assay, and thiobarbituric acid reactive substances (TBARS) assay according to previously reported methods. At the end of the feeding experiments, animals were subjected to barbiturate euthanasia and a transverse abdominal incision was made. The cecal wash samples with phosphate-buffered saline (pH 7.4) were stored at -80 °C. Liver and brain samples were also harvested. All experimental procedures were approved by the Ethics Review Committee, University of Kelaniya. Short-chain fatty acids (SCFAs) in the cecal wash, plasma, liver, and brain samples were quantified by Gas chromatography. SCFA levels were determined by the standard curves of each SCFA. Shapiro-Wilk normality test (P<0.05) and t-test was used for the statistical comparison. Acetate, propionate, and butyrate concentrations were 802.9±0.4 μg/mL, 156.3±2.1 μg/mL, 20.5±0.4 μg/mL and 802.8±0.4 μg/mL, 153.5±1.7 μg/mL, 19.9±0. μg/mL in CMD and SOD cecal wash samples respectively. Acetate, propionate, and butyrate concentrations were 236.2±0.1 μg/mL, 16.2±0.2 μg/mL, 1.3±0.0 μg/mL and 226.3±1.4 μg/mL, 14.4±0.2 μg/mL, 1.2±0.0 μg/mL in CMD and SOD plasma samples respectively. There was a significant (P<0.05) difference between plasma acetate and propionate levels in CMD compared to SOD. SCFAs were not detected in liver and brain samples. Saccharolytic microbes ferment oligo- and polysaccharides and produce SCFAs. Following their production SCFAs are rapidly absorbed by colonic cells and those not metabolized by colonic cells pass into the liver. Thus, only a small amount of the SCFAs reach systemic circulation and other tissues. Alcohol causes oxidative stress by releasing reactive oxygen species (ROS) during alcohol metabolism. Polyphenols serve as exogenous antioxidants, and they scavenge free radicals to control ROS. According to the four assays, there were no significant differences in the antioxidant capacity between the four groups suggesting no antioxidant effect of coconut milk over soy oil control. Thus, CM has a significant (P<0.05) impact on SCFAs passing through the intestinal barrier but no effect on the management of oxidative stress than soy oil.Item Effect of the wet extraction methods on the phenolic profile of coconut oil(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Anjali, N. V. P.; Algama, C. H.; Seneviratne, K. P.; Jayathilaka, N.; Seneviratne, K. N.; Sakalasuriya, D. D.; Silva, C. D.There are multiple methods for producing virgin coconut oil, which can broadly be divided into wet and dry processes. In the wet methods, coconut oil is directly extracted from the coconut milk, an aqueous emulsion is prepared using freshly grated coconut kernel. The method used to extract oil can affect the quality parameters and the phenolic profile of each coconut oil. Therefore, the phenolic profile, and the antioxidant capacity of coconut oil produced using four wet extraction methods, namely, boiling method (BM), fermentation method (FM), chilling and thawing method (CTM) and centrifugation method (CM) were quantified using previously reported methods. The shelf life of each oil sample at 28 ℃ was analyzed based on the induction time of each oil sample using a Rancimat apparatus. Phenolic profiles and unsaponifiable matter were analyzed qualitatively and quantitatively using HPLC. Shelf life at 28 ℃ (2.9±0.0 years), 𝛼-tocopherol (78.9±0.4 mg/Kg), total phenolic content (660±1 gallic acid equivalent mg/oil Kg) and antioxidant activity (19.4± 1.0%) are significantly (P<0.05) higher in the oil prepared by BM compared to the other wet extraction methods. The phenolic profile of CM and CTM included p-hydroxybenzoic acid, epigallocatechin gallate (EGCG), and epicatechin. The phenolic profile of coconut oil prepared by FM included gallic acid, p-hydroxybenzoic acid, EGCG, epicatechin, and epigallocatechin (EGC). In addition to the p-hydroxybenzoic acid and gallic acid, gallocatechin gallate (GCG), and catechin were found in significantly (P<0.05) higher amounts in coconut oil extracted using BM as a result of epimerization of EGCG and epicatechin to GCG and catechin under the heating conditions used in the BM. Hydrolysis of EGCG was found to be responsible for the observed low levels of EGCG (0.01±0.00 mg/oil Kg) and the presence of gallic acid and EGC in the coconut oil prepared by FM compared to the other two cold extraction methods (CTM, CM). Therefore, the extraction method has a significant impact on the phenolic profile of coconut oil.Item Application of rolling circle amplification (RCA) to detect direct amplification of dengue virus in patient serum samples.(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Manilgama, T.; Seneviratne, K. N.; Jayathilaka, N.Rolling Circle Amplification (RCA) is an isothermal amplification process that can be utilized for rapid amplification of target nucleic acids. In contrast to PCR, which uses thermocycling to mediate denaturation, annealing, and subsequent extension, RCA can be performed at a single reaction temperature making RCA an attractive solution for disease diagnosis based on amplification of pathogen nucleic acids at resource limited settings. In addition, PCR-based detection of pathogenic RNA involves the additional steps required to make complementary DNA copies of the target for amplification. Dengue is a mosquito vector borne viral RNA infection that largely affects urban and semi-urban, sub-tropical and tropical areas. While majority of dengue fever patients recover with careful hospital monitoring some patients may develop severe complications that result in mortality. Therefore, early diagnosis is critical for screening the patients that require hospital management and to prevent exceeding hospital capacity during a dengue outbreak. We developed a direct RCA of dengue virus RNA in serum samples from dengue virus positive patients using Phi 29 DNA Polymerase for the disease diagnosis at resource limited settings. Serum samples were collected from patients suffering from dengue virus infection based on a positive NS 1 antigen test within four days from fever onset with informed consent (n=3). Serum samples collected from healthy individuals were used as the controls (n=3). Multiple Displacement Amplification (MDA) was used to increase the amplification efficiency. Positive control reactions were carried out using a circularized 66 bp linear 5´phosphorylated probe that contained a complementary sequence to all four dengue serotypes and a forward primer against the conserved target region on the probe at 30 oC overnight. The product formation was confirmed by gel electrophoresis following restriction enzyme digestion of the RCA/MDA products with EcoRI. The RCA/MDA products were quantified using a ssDNA dye. Direct isothermal amplification of dengue virus from serum samples collected from dengue infected subjects confirmed that RCA/MDA reaction specifically amplifies dengue virus in patients while no amplification was detected for the serum samples collected from healthy volunteers. Since RCA/MDA can be used for direct gene expression analysis of mRNA and micro RNA in resource limited settings, this novel method can be used for simultaneous disease diagnosis and early prognosis of severe dengue based on differential expression in resource limited settings.Item Metagenomic analysis of the effect of coconut milk on the colon microbiota(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Ambanpola, N.; Anjali, N. V. P.; Manilgama, T.; Gunawardane, M.; Seneviratne, K. N.; Jayathilaka, N.The main source of fat in the diet affects the gut microbiome composition. Coconut milk (CM) has a high percentage of medium chain fatty acids (MCFA). A portion of MCFA reaches the colon and is fermented by the microbiota. This study was conducted with Wistar rats to study the effect of CM on colonic microbial diversity. Twelve-week-old female Wistar rats were randomly assigned to two experimental groups (12 rats/group). Ad libitum access to water and food was provided throughout the study. The control group was fed with a WHO-recommended diet containing 4.2 % total fat; of that 3% fat from soybean oil (SOD). The other group was fed a diet in which the fat component was replaced with CM (CMD). After 28 days, six rats from each group were fasted for 10–12 h and treated with ethanol (20%, 6 g/kg body weight) by oral gavage (SODE and CMDE). Mean ± standard deviation (SD) feed Intakes were 900.50±4.93 g, 899.50±9.31 g, 818.00±6.57 g, 820.00±6.57 g and body weight gains were 52.83±1.83 g, 52.33±1.75 g, 45.50±2.43 g, 47.33±2.34 g in CMD, CMDE, SOD and SODE groups respectively. Feed conversion rates were approximately equal in the four groups (average 0.0580±0.002). At the end of the feeding experiments, animals were subjected to barbiturate euthanasia and a transverse abdominal incision was made. The cecal wash samples with phosphate-buffered saline (pH 7.4) were stored at -80 °C. All experimental procedures were approved by the Ethics Review Committee, University of Kelaniya. Microbial DNA was isolated from cecal wash samples using DNeasy blood and tissue kit (Qiagen). The 16S rRNA gene libraries were prepared and sequenced according to the protocols recommended by Ion Torrent (Ion GeneStudio S5 prime system, Thermo Fisher Scientific). Trimmed sequences were clustered into operational taxonomic units (OTUs) with a hierarchical cutoff of 97.0% similarity using Ion Reporter v5.16. Taxonomic annotation was conducted against Curated MicroSEQ 16S Reference Library v2013.1 and Curated Greengenes v13.5 databases. Alpha-diversity and beta-diversity analyzes were performed using the QIIME2 platform. Bacteroidetes and Firmicutes phyla represent 90% of the cecal bacterial community across dietary groups. Other microbial phyla in the cecal wash samples were Actinobacteria, Proteobacteria, and Tenericutes. The cecal microbiota of CMD-fed rats was characterized by a significant increase (P<0.05) in the relative abundance of Desulfovibrionaceae, Eubacteriaceae, Erysipelotrichaceae, Lachnospiraceae Porphyromonadaceae, Ruminococcaceae bacterial families, and a decreased relative abundance of Bacteroidaceae, Clostridiaceae and Lactobacillaceae compared to the control diet. Studies have shown that alcohol promotes both dysbiosis and bacterial overgrowth. According to the two factor ANOVA, there was a significant difference (P<0.05) in colonic-microbiota between the four groups. Family level rarefaction plots were varied CMD>CMDE>SOD>SODE and CMD>SODE>CMDE>SOD according to Chao1 index and Simpson’s indexes respectively. Principle component analysis revealed four distinct clusters, suggesting that both diet and alcohol-induced oxidative stress affected gut microbiota. The elevated bacterial families have an impact on microbial-mediated saccharolytic functions, lipophilic functions, vitamin synthesis, and protection against intestinal infections. Thus, the intestinal microbiota in Wistar rats varies significantly with dietary fat source and oxidative stress conditions.Item Distribution of leishmaniasis cases and some demographic characters of patients recorded in the Medirigiriya medical officer of health (MOH) area, Polonnaruwa district of Sri Lanka(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Karunarathna, D. M. N. P.; Udayanga, N. W. B. A. L.; Ranathunge, R. M. T. B.; Kumarawansha, W. K. W. S.; Ganehiarachchi, G. A. S. M.Leishmaniasis has been recognized as one of the major challenges to the health sector of many countries. In the Sri Lankan context also, leishmaniasis infections are increasing within the past few years. Evaluation of the spatio-temporal trends in leishmaniasis incidence strongly facilitates the management of leishmaniasis. Therefore, the current study was conducted to identify recent spatial and temporal trends in leishmaniasis distribution, while assessing the characteristics of susceptible population to leishmaniasis infection in the Medirigiriya Medical Officers of Health (MOH) area in the District of Polonnaruwa, which reported the highest number of Leishmaniasis cases over the period from 2015 to 2022. Monthly records of reported leishmaniasis cases in Medirigiriya MOH area were obtained at monthly intervals from Epidemiology Unit, Sri Lanka from January, 2018 to June, 2022. Spatial maps of the recorded leishmaniasis case distribution in each Public Health Inspector (PHI) area were developed using ArcGIS (version 10.8). The paired-Chi square was used to investigate the impact of gender and age on the infection. The Medirigiriya MOH area had reported a total of 418 cases within the study period. Among the five PHI areas, Medirigiriya (34.7%) and Diulankadawala (33.8%) PHI areas reported the highest incidence of leishmaniasis cases, emerging as the high-risk areas. Meanwhile, Ambagaswewa PHI area denoted the lowest susceptibility (7.6%). As suggested by the results of the paired-Chi square test, emergence of leishmaniasis was characterized with significant spatial and temporal trends (P<0.05). The Percentage Infected Male: Female Ratio (PIMFR) suggested that the, males had a relatively high susceptibility for leishmaniasis infection than females, with an average PIMFER of 62.4:37.6. Significant shifts in the age of leishmaniasis patients were identified throughout the study period (P<0.05). Population belonging to the age group of 40 to 60 years (44%) and 21 to 40 years (25.2%) were identified as the most vulnerable age group for the incidence of leishmaniasis. On the contrary, age groups of > 60 years reported the lowest vulnerability (9.2%) for leishmaniasis infection. The identification of the potential high risk PHI areas with high susceptibility to leishmaniasis, along with the vulnerable age groups in the community would assist the relevant vector controlling agencies to concentrate their efforts, ensuring the effective controlling of leishmaniasis outbreak occurrence within the Medirigiriya MOH.Item In silico study of physicochemical, pharmacokinetic, toxicity, metabolism and molecular docking of aristolactam E, a constituent of Aristolochia elegans Mast(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Wadanambi, P. M.; Seneviratne, K. N.; Jayathilaka, N.Aristolochia elegans Mast, also known as Calico flower, is an ornamental plant found around the world including Asia. In traditional medicine, the plant has been used to treat a variety of disorders by employing its broad spectrum of pharmacological properties such as antibacterial, antitumoral, antidiarrheal, anti-snake venom, and anti-scorpion venom. It is also rich in aristolactam alkaloids, which have a variety of biological effects including anti-inflammatory, antibacterial, and anticancer activities. Aristolactam E (AE) is one of the less studied aristolactam alkaloids found in Aristolochia elegans Mast. Therefore, this computational study was designed to investigate (a) physicochemical properties and drug likeness, (b) pharmacokinetic and toxicity, (c) mode of antibacterial, anticancer and antiinflammatory action, (d) sites of metabolism mediated by cytochrome P450 (CYP) 3A4 isoform and (e) probable metabolites of AE compound. The physicochemical attributes and drug likeness were assessed using molinspiration server. SwissADME, LASAR, and Pred-hERG 4.2 servers were used to estimate pharmacokinetic and toxicological characteristics. Molecular docking was performed using AutoDock 4.2 software to determine the binding affinity and molecular interactions of AE with protein targets namely, dihydropteroate synthase (DHPS), dihydroneopterin aldolase (DHNA), phospholipase A2 (PLA2) and tankyrase 2 (TNK2). SOMP, SMARTcyp, and RS-WebPredictor webservers were used to predict the sites of AE metabolism mediated by the CYP 3A4 isoform. Furthermore, the BioTransformer and GLORYx online tools were used to forecast the potential AE metabolites. AE demonstrated favorable physicochemical qualities and met the requirements for oral bioavailability and druggability by following both Lipinski's rule of five and the Veber rule. It also showed a high rate of human intestinal absorption and no blood-brain barrier permeability. Furthermore, the toxicity predictions revealed that AE was a mutagenic chemical, but it was not carcinogenic or cardiotoxic in the mouse model. The AE showed binding affinity of -5.45 kcal/mol, -8.79 kcal/mol, -7.32 kcal/mol, -8.30 kcal/mol and -8.41 kcal/mol with DHPS, DHNA, PLA2, TNK2 (nicotinamide binding site) and TNK2 (adenosine binding site) respectively. The AE exhibited a stronger binding affinity than the control compounds of DHNA and PLA2 while showing close binding affinity to the control of TNK2 (nicotinamide binding site). The overall evaluation identified two sites of metabolism of AE based on a consensus of different metabolism site predictions by CYP3A4 using SOMP, SMARTcyp and RS-WebPredictor webservers. Two probable metabolites of AE were proposed based on the consensus of the results of BioTransformer and GLORYx web tools. This computational analysis can aid in the development of AE derivatives with improved pharmacokinetic and toxicological profiles, hence accelerating drug discovery against microbial infections and inflammation.Item An investigation on the sensory quality parameters of cookies incorporated with coconut testa flour(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Kumuduni, L. D. S.; Majeed, U. L. A.; Asmath, A. M. M; Rihan, M. H.Coconut testa is an underutilized by-product generated from coconut industries. It has a potential nutritional value and various health benefits due to the presence of functional and nutraceutical compounds in it. However, coconut testa is underutilized as animal feed or wasted with no added value. Therefore, the researchers focus on how it could be incorporated into food preparations that would benefit the wider society. Hence, this study focused on developing a coconut testa-based flour and studying the possibility of using it as a food ingredient, particularly for the bakery industry. A good quality coconut testa was selected and sliced into small pieces. The slices were then dehydrated for 25 minutes at 160°C and ground into a fine powder. The quality of the cookies developed from the blends of wheat flour: coconut testa flour at five different ratios such as 100:0, 75:25, 65:35, 55:45, and 45:55 % respectively, were investigated to evaluate the sensory properties of cookies including the characteristics such as texture, color, odor, appearance, taste, mouthfeel, and overall acceptability. The sensory evaluation was conducted with 60 untrained panelists who scored against various quality attributes on a 7-point Hedonic scale to determine consumer preference. The data generated were statistically analyzed with SPSS (version 25). The results obtained revealed that a significant difference (p<0.05) was observed among different treatments in terms of all sensory quality parameters except odor. Score values for the color of cookies tended to increase due to brown color development caused by higher amounts of coconut testa flour. According to the panelists, a slightly bitter taste and undesirable mouthfeel were noticed in cookie samples exceeding 35% coconut testa flour level, which might be the cause of the lower acceptance of cookies incorporated with more than 35 % coconut testa flour. According to the findings of this investigation, replacing coconut testa flour up to a 35 % level might result in palatable cookies. However, higher preferences were given by the panelists to the cookie treated with 65:35 percent wheat: coconut testa flour. Therefore, underutilized coconut testa could be utilized for the development of bakery products with lower gluten content.Item Tuning the carboxylic groups and increasing the number of defects in graphene oxide nano sheets by changing the oxidation duration of modified Hummers method(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Premadasa, P. M.; Panamaldeniya, S. A.; Munasinghe, M. A. H. M.; Gunawardhana, N.Graphene Oxide (GO) is a 2-D monolayer/ few stacked layers material synthesized from graphite by introducing oxygen-containing functional groups (carboxylic, hydroxyl, and epoxy) to the graphene sheet. GO has both SP2 and SP3 hybridized carbon atoms, which are decorated by oxygen-containing functional groups. GO is extensively investigated in the translational research rather than fundamental research due to the broad range of applications in the synthesis of energy storage devices as fuel cells. The Modified Hummers method is the most frequently used method for the synthesis of GO. In this work, we have used the oxidation duration of the modified Hummers’ method to tune the carboxylic groups that are attached to the GO sheets with a higher number of defects because the more COOH groups with higher number of defects could enhance the activity of the GO. Here, grinded vain graphite, KMnO4 (an oxidizing agent), and H2O2 were used as basic precursors and three distinct GO materials were synthesized by varying the oxidation durations as 24, 48, and 72 hours for GO-1, GO-2, and GO-3. SEM, PXRD, FTIR, and RAMAN techniques were used to examine the qualitative and quantitative variations in COOH bonds in all three materials. According to the observed SEM images, the sheet morphology is visible in all three materials. But, the GO-3 sample exhibits a cloud-like structure with sheet morphology. It suggests that changing the oxidation time affected the number of defects in the materials. Next, the PXRD spectrums were observed to analyze interlayer spacing of GO sheets. Characteristic peaks of PXRD were obtained between 10° and 12°, but the d-spacing value increased with the oxidation duration of the materials. According to the observed FTIR spectrums, the peak intensities relevant to the carboxylic bonds at 1756cm-1 enhanced with the oxidation duration while all the other peaks remained the same. Stronger vibration relevant to the COOH indicates the production of COOH bonds and GO-3 contains more COOH bonds rather than other two materials. The Raman analysis shows that the intensity of the G and D peaks has grown with the length of oxidation. With the rise in oxidation duration, the FWHM (full width half maximum) of band G, which indicates the presence of SP3 bonding in the materials have also increased. Similarly, the oxidation duration affected the nature of the D band which confirmed the increment of number of defects with oxidation duration. In conclusion, the oxidation duration of the modified Hummers’ method directly influences the formation of COOH bonds, and the number of COOH bonds increase with oxidation duration.Item Introducing an ED-CdTe nucleation layer on the CBD-CdS layer in solar cell fabrication(Faculty of Graduate Studies, University of Kelaniya Sri Lanka, 2022) Gajanayake, G. K. U. P.; Silva, D. S. M. D.; Thanihaichelvan, M.Developing a cost-effective and efficient thin-film CdS/CdTe solar is vital in resolving the energy crisis in the world. In the fabrication of solar cells, the weak interlayer contact caused by the voids between the window and the absorber layer adversely affected the performance of the device. This study explores the effectiveness of introducing an intermediate ultra-thin CdTe nucleation layer on reducing the Te diffusion into CdS and recombination effect to mitigate layer mismatch between the window and the absorber layer. Herein, the CdS layer was grown on the glass/FTO substrates which were subjected to prior chemical and plasma cleaning processes. In CdS deposition, Cd(CH3COO)2 (0.033 mol/L), CS(NH2)2 (0.667 mol/L) were utilized as cadmium and sulfur precursors while CH3CO2NH4 (1.0 mol/L) and NH4OH (25%) were used to adjust the pH in the bath at 90 ℃. The deposited glass/FTO/CBD-CdS samples were sonicated and dried with N2 flow. Next, an ultrathin CdTe nucleation layer was electrodeposited in an electrolyte containing 1.0 mol/mL CdSO4 and 1.0 mmol/mL TeO2 in pH 2.3 at 65 ℃ for 40 s on the glass/FTO/CBD-CdS. Herein, the graphite sheet (counter electrode), saturated calomel electrode (reference electrode) and glass/FTO/CdS substrate (working electrode) were used at a cathodic deposition potential of -650 mV with respect to the SCE. The optical property analysis revealed that the energy band gap of the glass/FTO/CBD-CdS and glass/FTO/CBD-CdS/ED-CdTe declined from 2.39 eV to 2.37 eV and their optical transmittance is over 80% in the wavelength ranges of 520-900 nm and 535-900 nm, respectively, in the devices. Therefore, there is no adverse effect of the ED-CdTe nucleation layer on light absorption by the window layer. The miniature shrinkage of the band gap might arise due to Te diffusion into the CdS layer. The SEM cross-sectional analysis uncovered that the thickness of the CBD-CdS/ED-CdTe bilayer was ~102 nm, and further, there is no distinguishable boundary between the ED-CdTe layer and CBD-CdS layer. No drastic change in surface roughness was detected between CBD-CdS/ED-CdTe and CBD-CdS. The SEM and AFM imaging further evidenced the improved uniformity of the surface layer upon deposition of the nucleation layer. Hence, the well packed ultra-thin ED-CdTe layer developed on glass/FTO/CBD-CdS substrate facilitates the growth of the CdTe absorber layer while minimizing the possible degradation or contamination of the CdS layer underneath upon exposure to high-temperature deposition by the close-spaced sublimation of CdTe.