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AN EXPLORATION INTO THE QUANTUM CONFINEMENT OF CTS/NATURAL DYE CORE- SHELL QUANTUM DOTS
摘要： In this work, we have presented a simple way of changing the confinement energies of Copper Tin Sulphide (CTS) quantum dots using natural dyes as shell material. Tetragonal CTS quantum dots in the size range of 1.7nm- 2.2nm, of bandgaps of 2.48eV and 5.0 eV were prepared by means of a green colloidal synthesis technique. These quantum dots were treated with natural dyes such as onion and beetroot skin dyes. Pelargonidin and Betanin (pigments of onion and beetroot skin dye respectively) formed hydrogen bonding with the capping agent, thus forming a shell around the CTS quantum dots. The change in confinement due to the effect of dye as shell was studied from absorption, photoluminescence and infrared spectroscopic techniques. The transitions occurring were analysed using a theoretical approach. CTS quantum dots, with its high transmittance in a wide range of wavelengths find promising applications in the buffer layer of solar cells.
关键词： Betanin,Copper tin sulphide,quantum dots,Pelargonidin,colloidal synthesis,quantum confinement
更新于2025-09-12 10:27:22
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Performance Enhancement of Betanin Solar Cells Co-Sensitized with Indigo and Lawsone: A Comparative Study
摘要： Co-sensitization is an important strategy toward e?ciency enhancement of solar cells by enabling better light harvesting across the solar spectrum. Betanin is a natural dye which absorbs light in the major portion of the incident solar spectrum (green region) and is the most e?cient natural pigment used in dye-sensitized solar cells. This study investigates the performance enhancement of a betanin solar cell by co-sensitizing it with two natural pigments which show complementary light absorption, indigo and lawsone, absorbing in the red and blue regions of the solar spectrum, respectively. The calculated highest occupied molecular orbital and lowest unoccupied molecular orbital energies of the pigment molecules, derived from density functional theory (DFT) simulations, con?rmed their optimal alignment with respect to the conduction band energy of the TiO2 semiconductor and reduction potential energy level of the I?/I3 ? electrolyte, a necessary requirement for optimal device performance. Lawsone solar cells displayed better performance, showing average e?ciencies of 0.311 ± 0.034%, compared to indigo solar cells showing e?ciencies of 0.060 ± 0.004%. Betanin was co-sensitized with indigo and lawsone, and the performances of the co-sensitized solar cells were compared. The betanin/lawsone co-sensitized solar cell showed a higher average e?ciency of 0.793 ± 0.021% compared to 0.655 ± 0.019% obtained for the betanin/indigo co-sensitized solar cell. An 11.7% enhancement in e?ciency (with respect to betanin) was observed for the betanin/indigo solar cell, whereas a higher enhancement of 25.5% was observed for the betanin/lawsone solar cell. Electrochemical impedance spectroscopy studies con?rmed that the higher e?ciency can be attributed to the higher electron lifetime of 313.8 ms in the betanin/lawsone co-sensitized solar cell compared to 291.4 ms in the betanin/indigo solar cell. This is due to the energy levels being more optimally aligned in lawsone compared to that of indigo, as observed in the DFT studies, and the lack of dipole moment in indigo, resulting in more e?cient charge separation and charge transfer in lawsone.
关键词： DFT simulations,indigo,electrochemical impedance spectroscopy,dye-sensitized solar cells,co-sensitization,betanin,lawsone
更新于2025-09-12 10:27:22
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Preharvest application of ethephon and postharvest UV-B radiation improve quality traits of beetroot (Beta vulgaris L. ssp. vulgaris) as source of colourant
摘要： Background: Betanins have become excellent replacers for artificial red-purple food colourants. Red beet (Beta vulgaris L. spp. vulgaris) known as beetroot, is a rich source of betalains, which major forms are betanin (red to purple) and vulgaxanthin (yellow). Betalains and phenolic compounds are secondary metabolites, accumulation of which is often triggered by elicitors during plant stress responses. In the present study, pre-harvest applications of ethephon (an ethylene-releasing compound) and postharvest UV-B radiation were tested as elicitors of betalains and phenolic compounds in two beetroot cultivars. Their effects on quality parameters were investigated, and the expression of biosynthetic betalain genes in response to ethephon was determined. Results: Ethephon was applied as foliar spray during the growth of beetroot, resulting in increased betanin (22.5%) and decreased soluble solids contents (9.4%), without detrimental effects on beetroot yield. The most rapid accumulation rate for betanin and soluble solids was observed between 3 and 6 weeks after sowing in both untreated and ethephon-treated beetroots. Overall, the expression of the betalain biosynthetic genes (CYP76AD1, CYP76AD5, CYP76AD6 and DODA1), determining the formation of both betanin and vulgaxanthin, increased in response to ethephon treatment, as did the expression of the betalain pathway activator BvMYB1. In the postharvest environment, the use of short-term UV-B radiation (1.23 kJ m? 2) followed by storages for 3 and 7 days at 15 °C resulted in increased betanin to vulgaxanthin ratio (51%) and phenolic content (15%). Conclusions: The results of this study provide novel strategies to improve key profitability traits in betalain production. High betanin concentration and high betanin to vulgaxanthin ratio increase the commercial value of the colourant product. In addition, lowering soluble solids levels facilitates higher concentration of beetroot colour during processing. Moreover, we show that enhanced betanin content in ethephon-treated beetroots is linked to increased expression of betalain biosynthetic genes.
关键词： Betanin,Ethephon,UV-B radiation,Vulgaxanthin,Beetroot,Betalain biosynthetic pathway
更新于2025-09-09 09:28:46