Background report: Kurunegala, Sri Lanka

Development projects / Water resources / Social aspects / Population / Households / Income / Water supply / Sanitation / Wastewater / Water quality / Public health / Waterborne diseases / Land use / Land tenure / Legislation / Sri Lanka / Kurunegala / Wan Ela / Beu Ela

Composition-Tunable Properties Of CdSxTe1-x Alloy Nanocrystals

Ternary CdSxTe1-x semiconductor quantum dots with both homogeneous and gradient composition have been fabricated via pyrolysis of organometallic precursors. The nanocrystal structure, size, and composition were characterized by UV-visible absorption and fluorescence spectroscopy, transmission electron microscopy, energy-dispersive X-ray elemental analysis, and X-ray diffractrometry. It was found that the band gap of homogeneously alloyed CdSxTe1-x is highly nonlinear with the crystalline composition, which was evidenced by a significant red-shift in the fluorescence of these nanocrystals with respect to the emission wavelength of their CdS and CdTe binary compounds. This effect, also known as optical bowing, seems to be enhanced in CdSxTe1-x nanocrystals because of large differences in atomic radii and electronegativities of S and Te chalcogens. Properties of gradient ternary alloys were found to be markedly different from those of homogeneous CdSxTe1-x. Their absorption and emission profiles, for instance, had a relatively low spectral overlap leading to large Stokes shifts of up to 150 nm. Other properties of fabricated CdSxTe1-x, nanocrystals and their significance to applications in areas of biomedical imaging, solar cells, and quantum dot-based LEDs are discussed

Blue-shifted Emission in CdTe/ZnSe Heterostructured Nanocrystals

Properties of colloidal heterostructured nanocrystals are largely determined by the spatial distribution of photogenerated carriers across the junction of semiconductor materials that form the heterostructure. The two known types of carrier distributions are identified based on whether both carriers reside within the same (type I) or opposite (type II) sides of the heterojunction. Here we demonstrate the existence of another type of spatial carrier distribution in heteronanocrystals, which corresponds to the localization of both charges along the material junction. Such localization. pattern was realized in novel CdTe/ZnSe heteronanocrystals, where the expected type I infrared emission was dominated by more intense photoluminescence in the 570-600 nm range, corresponding to the recombination of carriers within an interfacial alloy layer, formed by the cation and anion exchange between CdTe and ZnSe phases. Fabricated heteronanocrystals exhibit excellent optical characteristics including near-single-exponential lifetimes, enhanced emission stability, and fluorescence emission quantum yields of up to 24%

Clinical presentation and outcome of Sri-Lankan Ornamental Tarantula Poecilotheria fasciata spider bite: a case report

We report on a 19-year-old boy with visible muscle spasms admitted to the hospitals 24 hours after spider bite. He was treated effectively with intravenous calcium gluconate followed by oral calcium supplements and made a full recovery 48 hours after the incident. Although no specific treatment exists in Srilanka, it has been suggested that calcium supplements may be beneficial to relieve the muscle spasms. Our patient made a full recovery with calcium supplements suggesting the treatment with calcium is beneficial in relieving the pain and muscle spasms caused by Sri-Lankan Ornamental Tarantula Poecilotheria fasciata

Linker-Free Modification Of TiO2 Nanorods With PbSe Nanocrystals

We report on a colloidal synthesis of Pbse/TiO2 heterostructures, comprising small-diameter PbSe nanocrystals epitaxially grown onto the surface of TiO2 nanorods. The deposition of lead selenide onto prefabricated TiO2 nanocrystals proceeds via formation of a thin PbSe shell that subsequently breaks into sub-2-nm islands. Additional precursor injections are then used to increase the size of PbSe nanocrystals up to 5 nm. In the case of small-size PbSe, a 2.1-ns transfer of photoinduced carriers into TiO2 domain was evidenced through quenching of the PbSe band gap emission. Overall, the present synthesis demonstrates a colloidal approach to all-inorganic modification of TiO2 surfaces with semiconductor nanocrystals, which provides a viable alternative to a more common supramolecular assembly of nanocrystal-oxide composites

Synthesis Of Pbs/tio2 Colloidal Heterostructures For Photovoltaic Applications

We report on heteroepitaxial growth of nearly monodisperse PbS nanocrystals onto the surface of TiO2 nanoparticles via colloidal hot-injection routes. Fabricated PbS/TiO2 nanocomposites can be dispersed in nonpolar solvents, which enables an easy solution processing of these materials into mesoporous films for use as light-absorbing layers in nanocrystal-sensitized solar cells. High-temperature deposition of the sensitizer material allows controlling both the size and the number of PbS domains grown onto TiO2 nanoparticles, whereby providing synthetic means for tuning the absorbance spectrum of PbS/TiO2 nanocomposites and simultaneously enhancing their photocatalytic response in the visible and near-infrared. Compared with conventional ionic bath deposition of PbS semiconductors onto TiO2, the reported method results in an improved nanocrystal quality and narrower distribution of PbS sizes; meanwhile, the use of hot-temperature deposition of PbS (T = 180 degrees C) promotes the formation of near-epitaxial relationships between PbS and TiO2 domains, leading to fewer interfacial defects. The photovoltaic response of pyridine-treated PbS/TiO2 nanocomposites was investigated using a two-electrode cell filled with polysulfide electrolyte. The measured photocurrent compared favorably to that of PbS/TiO2 electrodes fabricated via chemical bath deposition

Background report: Kurunegala, Sri Lanka

Unpublished background report, produced as part of the Wastewater Agriculture and Sanitation For Poverty Alleviation in Asia (WASPA Asia) ProjectWASPA Asia Project Report 1This project is funded by the European Commission under its Asia Pro Eco II Program. It is undertaken by the International Water Management Institute (IWMI), Sri Lanka; COSI, Sri Lanka; the International Water and Sanitation Centre (IRC), the Netherlands; NGO Forum for Drinking Water Supply and Sanitation, Bangladesh; and the Stockholm Environment Institute (SEI), Sweden. The project pilot cities are Rajshahi City in Bangladesh and Kurunegala City in Sri Lanka

Artificial neural network (ANN) approach to optimize cultivation conditions of microalga Chlorella vulgaris in view of biodiesel production

Artificial neural networks (ANN) are widely used for the modelling of biological systems due to their ability to interpret non-linear relationships between input and output parameters. Hence, ANN can be used as a tool for optimization of biological systems. In the present study, ANN models were developed to simulate the concentrations of biomass, total lipid, unsaturated lipid and oleic acid of Chlorella vulgaris with cultivation time and pH level as inputs. The predicted values were strongly correlated with experimental values (R-2>0.97 for training data set, R-2>0.92 for validation data set) for all ANN models while indicating superior prediction accuracy over response surface methodology (RSM). The importance of pH and time on different metabolites are diverse as indicated by the Olden's plots, and thus, special attention should be given when optimizing the cultivation of C. vulgaris for biodiesel production. Multi-objective optimization algorithm along with ANN models was used to determine the optimum cultivation time and pH to produce biodiesel. The optimum oleic acid concentration of 745.21 mg/L was observed at pH 7.46 after 16 days of cultivation whereas the concentrations of biomass, total lipid and unsaturated lipid are 2663.34 mg/L, 1266.33 mg/L, and 1072.58 mg/L respectively