Annual Research Symposium (ARS)
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Item Monitoring anti-cholinesterase contamination in Bathalagoda reservoir, Sri Lanka(University of Kelaniya, 2008) Hemachandra, C.K.; Pathiratne, A.; Pathiratne, K.A.S.Organophosphosphorus and carbamate pesticides are widely used in Sri Lanka for agricultural pest management. They may enter inland water bodies draining agricultural watersheds and affect aquatic fauna including fishery resources. These pesticides are considered as anti-cholinesterases as they could inhibit the cholinesterase enzymes including acetylcholinesterase which plays an important role in maintaining normal functioning of the nervous system. Hence monitoring of anticholinesterase contaminations in inland water bodies is important yet difficult due to low persistence of many of these pesticides. In the present study, anticholinesterase contaminations in Bathalagoda reservoir, located in the vicinity of agricultural lands in Kurunagala District were monitored bimonthly during the period September 2007 to June 2008 using brain and muscle cholinesterases (ChE) of feral Nile tilapia (Oreochromis niloticus), as a biomarker (n=IO). ChE activities were measured using standard methods established for this fish. The results show that ChE activities in brain and muscle tissues in feral fish were depressed significantly in comparison to the laboratory reared control fish by 57-72% and 59-78% respectively in September 2007 and December 2007. There were no significant gender specific differences in the ChE levels of the feral fish at each sampling stage. The brain and muscle ChE activities in the fish collected from the reservoir at each sampling stage were negatively correlated (p < 0.05) with the rainfall in the area. The depression of ChE levels in the brain and muscle tissue of feral tilapia may indicate the exposure of fish to anti-cholinesterase contaminations present in the reservoir during rainy periods.Item Evaluation of the Potential of Selected Polycyclic Aromatic Hydrocarbons in Inducing Xenobiotic Biotransformation Enzymes in Nile Tilapia(University of Kelaniya, 2007) Hemachandra, C.K.; Pathiratne, A.; Pathiratne, K.A.S.Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous contaminants of much ecotoxicological concern in the aquatic ecosystems. They can be biotransformed in fish liver by the phase 1 CYP1A1 dependent activation enzymes such as 7-ethoxyresorufin- 0-deethylase (EROD) and the phase II detoxification enzyme, Glutathione S-transferase (GST). The present study was carried out to evaluate the potential of selected P AHs in the natural environment in inducing hepatic xenobiotic biotransformation enzymes viz. EROD and GST in Nile tilapia, a widely distributed food fish in freshwater ecosystems. The fish (n = 5-6) were treated with naphthalene (20 ~-tg/g) or phenanthrene (20 and 40 ~-tg/g) or fluoranthene ( 1, 5, and 20 11glg) or corn oil alone as the carrier (controls) and enzyme activities were determined at 1 day and 3 days after the treatment using standard methods. The results showed that the EROD activity of the fish was not affected significantly by the treatment of fish with 1 11g/g fluoranthene. However all the other PAH treatments significantly depressed the EROD activity of the fish in comparison to the controls. Hepatic GST activity of the fish was significantly increased (up to 2 folds) by the P AH treatments in a dose dependent manner. Liver somatic index of the fish was not affected by the P AH treatments. The results revealed that naphthalene, phenanthrene and fluoranthene lack the inducing ability of hepatic EROD which could produce damaging side effects through the formation of reactive intermediates that could bind covalently with cellular DNA, RNA and proteins.Item Estimation of agricultural drainage and phosphorous loading to Embilikala and Malala lagoons in the Bundala wetland systems(University of Kelaniya, 2000) Priyankarage, S.C.; Matsuno, Y.; Mallawaarachchi, A.P.; Pathiratne, K.A.S.Item Investigation of growth parameters of CuInTe2 thin films by electrodeposition technique(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Chandima, A.M.B.; Pathiratne, K.A.S.; Darmadasa, M.; Wijesundera, R.P.; de Silva, D.S.M.Copper indium di-telluride (CuInTe2) is a promising semiconductor material for photovoltaic applications because of its suitable optoelectronic properties. Among the various deposition techniques available for the preparation of CuInTe2 thin films, method of electrodeposition is an attractive technique because of its simplicity, low cost and possibility of making large area thin films. In this investigation, potentiostatic electrodeposition of CuInTe2 thin films on fluorine doped tin oxide (FTO) was studied using a three electrode electrochemical cell containing an aqueous solution of CuCl, InCl2 and TeO2. pH of the solutions was adjusted by adding ultra pure HCl. The counter electrode was a graphite rod and reference electrode was Ag/AgCl. Electrolytic solutions were prepared with deionised water and 99.995 % pure chemicals. Prior to the film deposition FTO substrates were degreased in acetone and rinsed with deionised water followed by 2 min ultra-sonication. Cyclic voltammograms were used to investigate the growth parameters; deposition potential, concentration, proportion of CuCl, InCl2 and TeO2, pH, temperature and stirring speed of the bath. In order to grow the photoactive CuInTe2 thin films, set of samples were prepared by slightly changing the deposition potential using the growth parameters obtained from cyclic voltammetric curves. Photoactive performance (Voc and Isc) of the films were characterized using I-V measurements in PEC containing aqueous solution of Na2S2O3. Highest photoactivity is given when the film deposited at -600 mV Vs Ag/AgCl for 20 min in the electrolyte containing aqueous solution of 1 mM CuCl, 20 mM InCl2 and 2 mM TeO2. Deposition temperature, pH and stirring speed of the bath were room temperature, 1.5 and 125 rpm respectively. Annealing temperature and time were 4000C and 20 minutes respectively. The preliminary results of this study suggest the possibility of growing photoactive p-CuInTe2 thin films by single step electrodepostion technique.Item Electrochemical deposition of CdS thin films using ammonium thiocynate as the sulfur source(Book of Abstracts, Annual Research Symposium 2014, 2014) Ariyasingha, N.M.; de Silva, D.S.M.; Pathiratne, K.A.S.Use of a complexing agent containing sulfur atoms which can form a charge complex with Cd2+ ions could provide a condition necessary to bring atoms or ions of both the elements Cd and S together in the form of a charge complex to the electrode surface thereby facilitating the formation of CdS on the electrode surface over other materials. In the present study, electrochemical conditions necessary to electrodeposits thin films of CdS using ammonium thiocynate as the complexing agent was studied.Item Electrochemical deposition and characterization of CdTe thin films(Book of Abstracts, Annual Research Symposium 2014, 2014) Kumarasinghe, K.D.M.S.P.K.; Chinthana, H.R.D.; de Silva, D.S.M.; Pathiratne, K.A.S.The semiconductor cadmium telluride (CdTe) has been widely used in applications of photovoltaics, sensors and detectors because of its direct band gap with high atomic number and electron density. With its narrow and direct band gap, stability with high absorption coefficient and other optoelectronic properties, it is the most ideal material for photovoltaic structures. A solar cell made of polycrystalline CdTe thin film is one of the most promising low cost materials for photovoltaic applications. CdTe was grown using different techniques such as physical vapor deposition, chemical vapor deposition, molecular beam epitaxy, close space sublimation, liquid phase deposition and electrodeposition. Electrodeposition has demonstrated numerous advantages due to its simplicity, low cost and scalable manufacturing techniques. CdTe films have been electrodeposited on fluorine doped tin oxide (FTO) coated glass substrates which have sheet resistance less than 20 ?/sq. A conventional three electrode cell was used for the deposition where a high purity graphite rod and saturated calomel electrode (SCE) were presented as the counter electrode and as the reference electrode respectively. Prior to the deposition of semiconductor layers FTO glass substrates were cleaned by a sequence of steps which included wiping out with detergent, ultrasonic washing in detergent solvents and then with deionised water followed by degreasing using acetone, methanol and isopropyl alcohol. CdTe thin films have been prepared by potentiostatic electrodeposition from acidic solution containing CdSO4, CdCl2 and TeO2. The deposition mechanism was investigated by cyclic voltammetry. The thickness of the film can be controlled by the charge passed during the deposition, and it is possible to obtain p-type and n-type materials by changing the deposition potential. Photoelectrochemical (PEC) cell measurements were carried out in order to determine the electric conductivity type of electrodeposited layers.The PEC values were determined for both as deposited and heat treated materials.The electrodeposited thin films were characterized and investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible absorption spectroscopy. The CdTe thin films were found to posses a bandgap of (1.44�0.02) eV, which is in a good accordance with those reported in the literature.Item Eletrodeposition of CdS thin films using different sulfur sources for CdS/CdTe solar cells(Book of Abstracts, Annual Research Symposium 2014, 2014) Kumarasinghe, K.D.M.S.P.K.; Chinthana, H.R.D.; de Silva, D.S.M.; Pathiratne, K.A.S.Cadmium Sulphide (CdS) and Cadmium Telluride (CdTe) are two promising photovoltaic materials for thin film solar cells. CdS is a wide band gap n-type semiconductor, which can act as a window layer. The function of CdS is to allow energetic shorter wavelength photons to pass for the incidence at the hetero-interface with minimum absorption loss. The high optical band gap of CdS (~2.42 eV) assists this function. Among the different techniques, electrodeposition is one of the most suitable low cost methods, because the material can be deposited on the desired area of the substrate thus providing a film of reproducible quality. CdS films were prepared by electrodeposition technique from CdCl2 as cadmium precursor and Na2S2O3 or (NH4)2S2O3 as sulfur precursor in aqueous medium. For the electrodeposition of CdS three electrode system was employed using glass/FTO as the working electrode (cathode), saturated calomel electrode as a reference electrode and high purity graphite rod as a counter electrode (anode). Electrochemical deposition method through the influence of the concentration of precursor species, deposition potential, deposition temperature and pH offers excellent control over the properties of thin CdS layers using a potentiostatic approach. The changes in the morphology and properties of the films prepared from different sulfur sources were studied. The CdS layers grown using Na2S2O3 as sulfur precursor show thickness below 100 nm. Voc and Jsc obtained for initial solar cells with CdS films grown using Na2S2O3 as sulfur precursor had higher values compared to that of CdS semiconductor layers grown using (NH4)2S2O3. The photoelectrochemical (PEC) cell measurements were used to identify the electrical conductivity type of the layers and it was found that as grown and heat treated material layers were of n-type for both CdS layers which were grown using different sulfur sources. Upon heat treatment, the material layers show enhanced PEC signal indicating improved optical properties. The optical absorption measurements were carried out in order to evaluate the band gap of the resulting materials. All samples exhibit a band gap value of 2.42 0.08 eV without any noticeable differences as expected. Electrodeposited CdS films were characterized by XRD for determination of bulk structure and SEM for surface analysis.