Browsing by Author "Chaudhari A."
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Item Association of solar flares with magnetic complexity of the sunspot groups in solar active regions during solar cycles 23�25(Springer, 2024) Chaudhari A.; Singh A.; Sharma G.; Singh A.K.The present study aims to investigate the association of X-ray solar flares with the magnetic complexity of sunspot groups in active regions for the period from 1996 to 2023 (solar cycles 23 to 24 and ascending phase of solar cycle 25). Statistically, we have found that (1) the total 37,166 sunspots are affiliated with the 5412 active regions. Following the Hale magnetic complexity categorization method, a total occurring sunspot groups, comprised of 31.01%�?, 57.13%�?, 0.01% ?, 0% ?, 0.027% ??, 0.54%�??, 8.45%�??, and 2.83% ??? magnetic groups. (2) We also found that a total of 44,667 solar flares were observed in selected time intervals. Out of that total of 44,667 solar flares, only 24,031 (60.40%) flares have their solar active region, remaining flares have an unknown solar origin. Further investigation also shows that, out of 24,031 solar flares only 23,531 solar flares are associated with sunspot groups of different magnetic complexity (according to Hale magnetic classification). These sunspot groups are affiliated with the 2499 active regions. The investigated flares (sunspot-associated) database consists of 34.11% B-, 57.87% C-, 7.36% M-, and 0.63% X-class flares. Finally, we found that a higher percentage of the intense flares (M- and X-Class) are associated with the ??? type sunspot groups in solar cycles 23 and 24. We also observed that maximum X-class flares are associated with ??? sunspot groups during the peak of solar cycles 23 and 24. Whereas maximum B- and C-class flares are associated with ? sunspot groups during the ascending phase of each solar cycle. � Indian Association for the Cultivation of Science 2024.Item Biosynthesis of TiO2 nanostructures using Camellia sinensis extract (polyphenols) and investigation of their execution as photoanodes in photovoltaic device(Elsevier B.V., 2024) Kumar A.; Chaudhari A.; Kumar S.; Kushwaha S.Titanium dioxide (TiO2) nanoparticles (NPs) are indeed widely recognized and utilized as one of the most prominent photoanode materials in dye-sensitized solar cells (DSSCs). Therefore continuous efforts have been made to improve the performance of TiO2 photoanodes in terms of light absorption, charge carrier mobility, and overall energy conversion efficiency. Green synthesis methods for the production of TiO2 NPs, including the use of plant-based reducing agents, have gained significant attention in recent years. These methods are considered environmental friendly alternatives to traditional physical and chemical synthesis methods, which often involve the use of hazardous chemicals and complex processes. Therefore, in this work, a variety of tea types, including green, white, black, oolong, pu-erh have been used to synthesize TiO2 NPs. The differences in the amount of phenolic compounds and caffeine in various tea varieties can influence the topology, structure, and composition of the as synthesized nanoparticles (NPs). The prepared TiO2 NPs were comprehensively characterized for particle size, morphology, purity, composition, crystalline nature, structural, electrochemical and photovoltaic capabilities. The as synthesized titanium oxide (TiO2) NPs were spherical in shape and particle sizes ranged from 10 to 20 nm with little agglomerations. For DSSC application, thin films of synthesized TiO2 NPs were prepared by making paste of TiO2 NPs with Triton-X and spread onto conducting substrate (FTO) with the help of glass rod and finally sintering for 1 h at 450 �C. The prepared TiO2 electrodes were dipped in the standard N719 dye solution (0.1 � 10?3 M) in acetonitrile medium overnight for complete adsorption. Overall efficiency = 3.0 %, JSC = 9.72 mA/cm2, VOC = 660 mV and FF = 0.46 was achieved with the DSSC made up with green tea mediated TiO2 NPs based photo anode. Due to high phenolic content and good reductive properties, TiO2 NPs prepared using green tea extract were highly crystalline in nature, have high surface area, high roughness factor, good stability which results in maximum dye loading and hence increase in the overall conversion efficiency. � 2024 Elsevier B.V.Item Comparative study of natural and synthetic dyes in DSSCs: An experimental and computational approach(Elsevier B.V., 2024) Kumar A.; Chaudhari A.; Kumar S.; Kushwaha S.; Mandal S.This study explores the natural and synthetic dyes as sensitizers for dye-sensitized solar cells (DSSCs). Anthocyanin dye extract (PG) from pomegranate (Punica granatum) fruit, betanin pigment (BR) from beetroot (Beta vulgaris), and the commercially available organic dye, Rose Bengal (RB), were investigated as sensitizers for DSSCs and their photovoltaic performances were recorded. Density functional theory (DFT) and time-dependent DFT (TD-DFT) studies have also been performed in order to get insight into the photophysical and photoelectrochemical properties. The overall efficiencies (?) of 0.34%, 0.30%, and 0.25% were obtained for the PG, BR, and RB dyes under 1 sun illumination, respectively. The results infer that PG dye would act as a promising photo-sensitizer for DSSCs as compared to BR and RB sensitizers, which may be due to better interaction between anthocyanin molecule of pomegranate extract and TiO2. � 2024 Elsevier B.V.Item Synthesis of TiO2 nanoparticles by green approach: Application as photoanode for dye-sensitized solar cells(Elsevier Ltd, 2024) Chaudhari A.; Kumar A.; Kumar S.; Kushwaha S.Efficient photoanodes play a central role in the performance of dye-sensitized solar cells. Traditional methods for synthesizing TiO2 often involve chemical processes that can be expensive and environmentally harmful due to the use of toxic and hazardous substances. Therefore in this work, TiO2 nanoparticles (NPs) were synthesized using bio-inspired processing through a hydrothermal procedure using different concentrations of Aloe barbadensis miller leaves extract as the reducing and stabilizing agent. Scanning electron microscopy (SEM), UV�vis spectroscopy (UV), X-ray difraction (XRD), Raman Spectroscopy, transmission electron microscopy (TEM) and Brunauer�Emmett�Teller (BET) analysis were used to characterize as synthesized TiO2 NPs. DSSCs were fabricated employing the prepared TiO2 NPs as photoanodes, and their performance was assessed. DSSC generates JSC of 9.7 mA/cm2, VOC of 0.682 V and efficiency (?) of 4.3 % when 20 mL concentration of extract was used for the synthesis of TiO2 NPs and subsequently their photoanodes. � 2024 Elsevier LtdItem Thin-film fabrication techniques in dye-sensitized solar cells for energy harvesting(wiley, 2024) Kumar A.; Chaudhari A.; Kumar S.; Kushwaha S.; Mandal S.From the last few decades, dye-sensitized solar cells (DSSCs) have emerged out as economical and reliable substitutes for energy source owing to their simple preparation, cheap cost, low toxicity, and competitive efficiency. The key components of DSSCs include the semiconducting thin film, sensitizer, redox couple, and counter electrode. The photoanode, which is made of a semiconducting thin film with a dye adsorbed on it, plays a crucial role in DSSCs, and its morphology depends on the deposition techniques used. Various established physical and chemical coating/deposition methods are promising for attaining high-quality thin films for DSSC fabrication. The morphology and particle size of the thin films strongly depend on the deposition techniques employed. Surface and interfacial effects significantly impact the whole performance of these films, leading to improved properties and characteristics compared to bulk materials. Highly functionalized thin films have their benefits when used as photoanodes in DSSCs, as the boosted functional properties of materials can be exploited at the nanoscale level. There are several techniques for depositing thin films, including physical, chemical, and colloidal routes. Some widely used methods include spray pyrolysis, sol-gel, plasma spray, electrophoretic deposition, screen printing, and dip coating. Vacuum deposition techniques such as magnetron sputtering and pulsed laser deposition are successfully established in the thinfilm coating industry due to the high quality and reproducibility of the fabricated thin films. While these techniques often require expensive equipment and complex experimental setups, they offer the advantage of producing thin and dense films. Colloidal, doctor blade, and dip coating techniques are advantageous because of their low cost and simplified experimental setup and equipment. These techniques produce thin films with controlled structures and particle size distributions. However, they may be prone to issues such as cracks, pores, or layer separation, which can be overcome by repeating the coating process several times intermittently. Sol-gel and slurry methods are extensively used to fabricate nanocrystalline thin films in DSSCs due to their lower cost than gas-phase methods. However, the meager stability of the precursors against hydrolysis remains a concern. The SILAR (successive ionic layer adsorption and reaction) method is another solution-based thin-film deposition technique, a modified version of chemical bath deposition. The resulting thin films exhibit improved grain structure orientation. In short, various deposition techniques are employed to fabricate thin films for DSSCs, each with its advantages and challenges. Researchers continue to explore and optimize these techniques/methods to improve the overall performance of DSSCs. � 2024 Scrivener Publishing LLC. All rights reserved.Item Variation in the Flaring Potential of Different Sunspot Groups During Different Phases of Solar Cycles 23 and 24(Institute of Physics, 2024) Singh A.; Chaudhari A.; Sharma G.; Singh A.K.In this present study, we have analyzed different types of X-ray solar flares (C, M, and X classes) coming out from different classes of sunspot groups (SSGs). The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019. During this, we observed a total of 15015 flares (8417 in SC-23 and 6598 in SC-24) emitted from a total of 33780 active regions (21746 in SC-23 and 12034 in SC-24) with sunspot only. We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface. Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24. In addition, we investigated yearly variations in the potential of producing flares by different SSGs (A, B, C, D, E, F, and H) during different phases (ascending, maximum, descending, and minimum) of SC-23 and 24. These are our findings: (1) D, E, and F SSGs have the potential of producing flares ?8 times greater than A, B, C and H SSGs; (2) The larger and more complex D, E, and F SSGs produced nearly 80% of flares in SC-23 and 24; (3) The A, B, C and H SSGs, which are smaller and simpler, produced only 20% of flares in SC-23 and 24; (4) The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24, respectively. (5) The potential for producing flares in each SSG is higher in SC-24 than in SC-23, although SC-24 is a weaker cycle than SC-23. (6) The alterations in the number of flares (C+M+X) show different time profiles than the alterations in sunspot numbers during SC-23 and 24, with several peaks. (7) The SSGs of C, D, E, and H-class have the highest flaring potential in the descending phase of both SC-23 and 24. (8) F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24. � 2024. National Astronomical Observatories, CAS and IOP Publishing Ltd.
