Eco-friendly Egyptian blue (CaCuSi4O10) dye for luminescent solar concentrator applications

This study focuses on synthesizing the heavy metal-free ancient Egyptian blue (EB; CaCuSi4O10) dye using a facile ceramic method for luminescent solar concentrator (LSC) application. XRD, SEM and EDX results confirmed that this well-crystallized material is successfully synthesized. Optical studies revealed that EB has a high Stokes shift and possesses an average lifetime of 110.50 μs with a quantum yield of 12.93%. Finally, an EB-integrated LSC was fabricated that exhibits a power conversion efficiency (η) of 0.15% and an optical conversion efficiency (ηopt) of 1.21%, which are the highest values reported so far using EB.publishedVersio

Anthropogenic Factors Driving Recent Range Expansion of the Malaria Vector Anopheles stephensi

The malaria vector Anopheles stephensi is found in wide tracts of Asia and the Middle East. The discovery of its presence for the first time in the island of Sri Lanka in 2017, poses a threat of malaria resurgence in a country which had eliminated the disease in 2013. Morphological and genetic characterization showed that the efficient Indian urban vector form An. stephensi sensu stricto or type form, has recently expanded its range to Jaffna and Mannar in northern Sri Lanka that are in proximity to Tamil Nadu state in South India. Comparison of the DNA sequences of the cytochrome oxidase subunit 1 gene in An. stephensi in Jaffna and Mannar in Sri Lanka and Tamil Nadu and Puducherry states in South India showed that a haplotype that is due to a sequence change from valine to methionine in the cytochrome oxidase subunit 1 present in the Jaffna and Mannar populations has not been documented so far in Tamil Nadu/Puducherry populations. The Jaffna An. stephensi were closer to Tamil Nadu/Puducherry populations and differed significantly from the Mannar populations. The genetic findings cannot differentiate between separate arrivals of the Jaffna and Mannar An. stephensi from Tamil Nadu or a single arrival and dispersion to the two locations accompanied by micro-evolutionary changes. Anopheles stephensi was observed to undergo preimaginal development in fresh and brackish water domestic wells and over ground cement water storage tanks in the coastal urban environment of Jaffna and Mannar. Anopheles stephensi in Jaffna was resistant to the common insecticides deltamethrin, dichlorodiphenyltrichloroethane and Malathion. Its preimaginal development in wells and water tanks was susceptible to predation by the larvivorous guppy fish Poecilia reticulata. The arrival, establishment, and spread of An. stephensi in northern Sri Lanka are analyzed in relation to anthropogenic factors that favor its range expansion. The implications of the findings for global public health challenges posed by malaria and other mosquito-borne diseases are discussed

Ruthenium (Ru) Doped Titanium Dioxide (P25) electrode for dye sensitized solar cells

In this study, P25-titanium dioxide (TiO2) was doped with ruthenium (Ru) by systematically varying the Ru content at 0.15, 0.30, 0.45 and 0.6 mol%. The synthesized Ru-doped TiO2 nanomaterials have been characterized by X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray (EDX) analysis, UV-visible (UV–Vis) spectroscopy, and electrochemical impedance (EIS) spectroscopy. The XRD patterns of undoped and Ru-doped TiO2 nanomaterials confirm the presence of mixed anatase and rutile phases of TiO2 while EDX spectrum confirms the presence of Ti, O and Ru. Further, UV-visible absorption spectra of doped TiO2 nanomaterial reveal a slight red shift on Ru-doping. The short circuit current density (JSC) of the cells fabricated using the Ru-doped TiO2 photoanode was found to be dependent on the amount of Ru present in TiO2. Optimized cells with 0.3 mol% Ru-doped TiO2 electrodes showed efficiency which is 20% more than the efficiency of the control cell (η = 5.8%) under stimulated illumination (100 mWcm−2, 1 sun) with AM 1.5 filter. The increase in JSC resulted from the reduced rate of recombination upon doping of Ru and this was confirmed by EIS analysis

Bimetallic AC/Ag2CrO4/SnS heterostructure photoanode for energy conversion and storage: A self-powered Photocapacitor

The worldwide increase in generation of solar based electricity prompts the essentiality of research efforts on the development of energy storage systems. In this regard, self-powered photocapacitors are of keen interest as they can directly convert and store the solar energy in the form of electrical energy in a single device. This study reports the photoelectrochemical energy storage capacity of a novel photocapacitor fabricated with FTO/Activated Carbon (AC)/Ag2CrO4/SnS nanostructured photoanode. Initially, the Ag2CrO4 and SnS nanostructures were synthesized using simple ultrasonication technique and hydrothermal method, respectively. The crystallinity, morphology and optical properties of the synthesized nanostructures were then studied. The XRD patterns indicated orthorhombic structure of both Ag2CrO4 and SnS. Their optical band gaps were calculated as 1.93 and 1.65 eV, respectively using Kubelka-Munk plots. The FTO/AC/Ag2CrO4/SnS photoanode was then fabricated and photoelectrochemical studies, namely cyclic voltammetry and electrochemical impedance spectroscopy were carried out on a three electrode system. The FTO/AC/Ag2CrO4/SnS photoanode showed a specific capacitance of 4782 mF/g at the scan rate of 10 mVs−1 when the device was subjected to visible light illumination (1 sun). Hence, the fabricated heterostructured photoanode provides a promising path for the design and synthesis of novel highly efficient solar energy harvesting and storage materials as photocapacitors

Cost Effective Solvothermal Method to Synthesize Zn-Doped TiO2 Nanomaterials for Photovoltaic and Photocatalytic Degradation Applications

Titanium dioxide (TiO2) is a commonly used wide bandgap semiconductor material for energy and environmental applications. Although it is a promising candidate for photovoltaic and photocatalytic applications, its overall performance is still limited due to low mobility of porous TiO2 and its limited spectral response. This limitation can be overcome by several ways, one of which is doping that could be used to improve the light harvesting properties of TiO2 by tuning its bandgap. TiO2 doped with elements, such as alkali-earth metals, transition metals, rare-earth elements, and nonmetals, were found to improve its performance in the photovoltaic and photocatalytic applications. Among the doped TiO2 nanomaterials, transition metal doped TiO2 nanomaterials perform efficiently by suppressing the relaxation and recombination of charge carriers and improving the absorption of light in the visible region. This work reports the possibility of enhancing the performance of TiO2 towards Dye Sensitised Solar Cells (DSSCs) and photocatalytic degradation of methylene blue (MB) by employing Zn doping on TiO2 nanomaterials. Zn doping was carried out by varying the mole percentage of Zn on TiO2 by a facile solvothermal method and the synthesized nanomaterials were characterised. The XRD (X-Ray Diffraction) studies confirmed the presence of anatase phase of TiO2 in the synthesized nanomaterials, unaffected by Zn doping. The UV-Visible spectrum of Zn-doped TiO2 showed a red shift which could be attributed to the reduced bandgap resulted by Zn doping. Significant enhancement in Power Conversion Efficiency (PCE) was observed with 1.0 mol% Zn-doped TiO2 based DSSC, which was 35% greater than that of the control device. In addition, it showed complete degradation of MB within 3 h of light illumination and rate constant of 1.5466×10−4s−1 resembling zeroth order reaction. These improvements are attributed to the reduced bandgap energy and the reduced charge recombination by Zn doping on TiO2

Cost Effective Solvothermal Method to Synthesize Zn-Doped TiO2 Nanomaterials for Photovoltaic and Photocatalytic Degradation Applications

Titanium dioxide (TiO2) is a commonly used wide bandgap semiconductor material for energy and environmental applications. Although it is a promising candidate for photovoltaic and photocatalytic applications, its overall performance is still limited due to low mobility of porous TiO2 and its limited spectral response. This limitation can be overcome by several ways, one of which is doping that could be used to improve the light harvesting properties of TiO2 by tuning its bandgap. TiO2 doped with elements, such as alkali-earth metals, transition metals, rare-earth elements, and nonmetals, were found to improve its performance in the photovoltaic and photocatalytic applications. Among the doped TiO2 nanomaterials, transition metal doped TiO2 nanomaterials perform efficiently by suppressing the relaxation and recombination of charge carriers and improving the absorption of light in the visible region. This work reports the possibility of enhancing the performance of TiO2 towards Dye Sensitised Solar Cells (DSSCs) and photocatalytic degradation of methylene blue (MB) by employing Zn doping on TiO2 nanomaterials. Zn doping was carried out by varying the mole percentage of Zn on TiO2 by a facile solvothermal method and the synthesized nanomaterials were characterised. The XRD (X-Ray Diffraction) studies confirmed the presence of anatase phase of TiO2 in the synthesized nanomaterials, unaffected by Zn doping. The UV-Visible spectrum of Zn-doped TiO2 showed a red shift which could be attributed to the reduced bandgap resulted by Zn doping. Significant enhancement in Power Conversion Efficiency (PCE) was observed with 1.0 mol% Zn-doped TiO2 based DSSC, which was 35% greater than that of the control device. In addition, it showed complete degradation of MB within 3 h of light illumination and rate constant of 1.5466×10−4s−1 resembling zeroth order reaction. These improvements are attributed to the reduced bandgap energy and the reduced charge recombination by Zn doping on TiO2

Natural sensitizer extracted from Mussaenda erythrophylla for dye-sensitized solar cell

Abstract In this study, a natural dye from the flowers of Mussaenda erythrophylla extracted separately in ethanol and de-ionized water was employed as a photosensitizer in DSSCs. The quantitative phytochemical analyses were performed on both extracts. The existence of flavonoids (anthocyanin) and chlorophyll a pigments in the ethanol extract of the dye was confirmed by the UV–Visible spectroscopy. The stability study performed on the said ethanol extract confirmed that the dye extracted in ethanol was stable in the dark and did not degrade for nearly 50 days. The presence of the dye molecules and uniform adsorption of them on the P25-TiO2 surface were confirmed by fourier transform infrared spectroscopy and atomic force microscopy, respectively. Moreover, the influence of dye concentration and pH on the optical properties of the dye was also studied. The natural dye extracted in ethanol was employed in DSSCs, fabricated by utilizing the said dye sensitized P25-TiO2 photoanodes, $${I}^{-}$$ I - / $${I}_{3}^{-}$$ I 3 - electrolyte, and Pt counter electrode. Photovoltaic performances of the fabricated devices were determined under simulated irradiation with the intensity of 100 mWcm–2 using AM 1.5 filter. The device fabricated with the P25-TiO2 photoanode sensitized by the dye extracted in ethanol at pH = 5 exhibited the best power conversion efficiency (PCE) of 0.41% with the JSC of 0.98 mAcm–2 which could be attributed to the optimum light absorption in the visible region of solar spectrum by the chlorophyll a and anthocyanin molecules in the extracted natural dye

Salinity-tolerant larvae of mosquito vectors in the tropical coast of Jaffna, Sri Lanka and the effect of salinity on the toxicity of <it>Bacillus thuringiensis</it> to <it>Aedes aegypti</it> larvae

<p>Abstract</p> <p>Background</p> <p>Dengue, chikungunya, malaria, filariasis and Japanese encephalitis are common mosquito-borne diseases endemic to Sri Lanka. <it>Aedes aegypti</it> and <it>Aedes albopictus</it>, the major vectors of dengue, were recently shown to undergo pre-imaginal development in brackish water bodies in the island. A limited survey of selected coastal localities of the Jaffna district in northern Sri Lanka was carried out to identify mosquito species undergoing pre-imaginal development in brackish and saline waters. The effect of salinity on the toxicity of <it>Bacillus thuringiensis israelensis</it> larvicide to <it>Ae</it>. <it>aegypti</it> larvae at salinity levels naturally tolerated by <it>Ae</it>. <it>aegypti</it> was examined.</p> <p>Methods</p> <p>Larvae collected at the selected sites along the Jaffna coast were identified and salinity of habitat water determined in the laboratory. The LC₅₀ and LC₉₀ of <it>B</it>. <it>thuringiensis</it> toxin, the active ingredient of a commercial formulation of the larvicide BACTIVEC®, were determined with <it>Ae</it>. <it>aegypti</it> larvae. Bioassays were also carried out at salinities varying from 0 to18 ppt to determine the toxicity of <it>Bacillus thuringiensis</it> to fresh and brackish water-derived larvae of <it>Ae</it>. <it>aegypti</it>.</p> <p>Results</p> <p>Larvae of four <it>Anopheles</it>, two <it>Aedes</it>, one <it>Culex</it> and one <it>Lutzia</it> species were collected from brackish and saline sites with salinity in the range 2 to 68 ppt. The LC₅₀ and LC₉₀ of <it>B</it>. <it>thuringiensis</it> toxin for the second instar larvae of <it>Ae</it>. <it>aegypti</it> in fresh water were 0.006 ppm and 0.013 ppm respectively, with corresponding values for brackish water populations of 0.008 and 0.012 ppm respectively. One hundred percent survival of second instar fresh water and brackish water-derived <it>Ae</it>. <it>aegypti</it> larvae was recorded at salinity up to 10 and 12 ppt and 100% mortality at 16 and 18 ppt, yielding an LC ₅₀ for salinity of 13.9 ppt and 15.4 ppt at 24 h post-treatment respectively for the two populations. Statistical analysis showed significantly reduced toxicity of <it>B</it>. <it>thuringiensis</it> to fresh and brackish water-derived <it>Ae</it>. <it>aegypti</it> larvae at high salinities.</p> <p>Conclusion</p> <p>A variety of mosquito vectors of human diseases undergo pre-imaginal development in brackish or saline waters in coastal areas of the Jaffna district in northern Sri Lanka. Salinity has a small but significant negative impact on the toxicity of <it>B</it>. <it>thuringiensis</it> toxin to <it>Ae</it>. <it>aegypti</it> larvae at salinity levels where <it>Ae</it>. <it>aegypti</it> larvae are found in the environment. This has implications for the use of <it>B</it>. <it>thuringiensis</it> toxin as a larvicide in brackish waters.</p