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- 2017
- photosynthesis
- dry matter
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- Agronomy
- University of Basilicata
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Potential of plant‐based photosensitizers in dye‐sensitized solar cell applications
摘要： In this work, the performance of dye-sensitized solar cells (DSSCs) has been investigated using the extracts from Murraya koenigii, Plectranthus amboinicus, and Coriandrum sativum. The DSSCs were assembled with the extracts, titanium dioxide as the working electrode, iodide/tri-iodide (I3?/I?) as redox couple, and platinum as the counter electrode and their photovoltaic performances were compared. The crude chlorophyll photosensitizer extracted from Plectranthus amboinicus exhibited an open-circuit voltage (VOC) of 637 mV, a short-circuit current density of 0.99 mA/cm2, a fill factor of 0.63, and an energy conversion efficiency of 0.46%. The present results were much higher than the previously reported results by our group.
关键词： photo-sensitizers,fabrication,chlorophyll,clean energy,natural dyes,solar cells
更新于2025-09-11 14:15:04
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Similarity and Specificity of Chlorophyll <i>b</i> Triplet State in Comparison to Chlorophyll <i>a</i> , as Revealed by EPR/ENDOR and DFT Calculations.
摘要： An investigation of the photoexcited triplet state of chlorophyll (Chl) b has been carried out by means of Electron Nuclear Double Resonance (ENDOR), both in frozen organic solvent and in protein environment provided by the Water-Soluble Chlorophyll Protein of Lepidium virginicum. Density functional theory (DFT) calculations have allowed the complete assignment of the observed hyperfine couplings corresponding to the methine protons and the methyl groups, leading to a complete picture of the spin density distribution of the triplet state in the tetrapyrrole macrocycle. The triplet state properties of Chl b were found to be similar in many respects to those previously reported for Chl a, although some specificities have been highlighted. Concerning the spin density distribution, the differences are manly localized on the carbon atoms close to the formyl group which, in Chl b, replaces the methyl group of Chl a.
关键词： EPR/ENDOR,triplet state,DFT calculations,Chlorophyll b,spin density distribution
更新于2025-09-11 14:15:04
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Mode-locked Tm-doped fiber laser with large modulation depth ReS <sub/>1.02</sub> Se <sub/>0.98</sub> nanosheet saturable absorber
摘要： Microcystis blooms and their associated microcystins pose a significant health risk to humans. Microcystis normally occurs as colonies in eutrophic water bodies, and its physiological tolerance to algaecides is dissimilar to that of unicellular forms. However, the differences of physiological response to algaecides between unicellular and colonial Microcystis have been poorly explored. The current study investigated the effects of hexane extract of Acorus calamus rhizome (HEACR) on the physiological and photosynthetic mechanisms of unicellular and colonial M. aeruginosa in the laboratory. We analyzed the cell density, reactive oxygen species (ROS) level, malonaldehyde (MDA) content, photosynthetic pigments, capsular polysaccharide (CPS), and photosystem (PS II) parameters of the two morphological forms of Microcystis. Our results show that HEACR suppresses the growth of both unicellular and colonial M. aeruginosa, increases the intracellular ROS level and cause lipid peroxidation, as well as exerting a detrimental effect on chlorophyll a (chl a) content and photosynthetic efficiency. Almost 100% inhibition was observed for unicellular and colonial M. aeruginosa after 3 d exposure to 50 and 100 mg L?1 HEACR, respectively. The ROS level increase, MDA accumulation, the chl a decrease and carotenoid increase in unicellular M. aeruginosa were all more obvious than that in colonial cells. The fall in photosynthetic efficiency of unicellular M. aeruginosa were also more significant than that of colonial cells. After 3d exposure, the maximum quantum yield of PS II photochemistry (Fv/Fm), effective quantum yield of PS II photochemistry (Fv’/Fm’) and effective quantum yield of photochemical energy conversion in PS II (YII) of unicellular M. aeruginosa was almost totally inhibited by 20 mg L?1 HEACR, while the Fv/Fm, Fv’/Fm’ and YII of colonial M. aeruginosa decreased by 43%, 26% and 66% for 100 mg L?1 of HEACR, respectively. Comparing the two morphological forms of Microcystis, colonies show a greater increase in CPS level to more effectively resist the stress of HEACR and to mitigate ROS generation thereby better defending against oxidative damage. Furthermore, colonial M. aeruginosa shows better photoprotection ability than the unicellular form when exposed to HEACR. The colonies also sustain their maximum electron transport rate, increase their tolerance to strong light, and maintain a higher ability to disperse excess energy. These results demonstrated that HEACR can significantly interfere with the growth and physiological processes of both unicellular and colonial M. aeruginosa, but that colonial M. aeruginosa has a greater ability to adjust physiological tolerance to resist the stresses of HEACR.
关键词： Reactive oxygen species,Acorus calamusrhizome extract,Microcystis aeruginosa,Physiological tolerance,Capsular polysaccharide,Chlorophyll fluorescence parameters
更新于2025-09-11 14:15:04
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Charge transfer dynamics in chlorophyll-based biosolar cells
摘要： We fabricated a chlorophyll (Chl)-based biosolar cell with H2Chl-sensitized TiO2 as an acceptor and (ZnChl)n as a donor. This solar cell gives a relatively high quantum yield from the absorption spectral contribution from both the donor and acceptor species. We employed subpicosecond time-resolved absorption spectroscopy (TAS) to study the excited state dynamics at the Chl interface. A charge transfer (CT) state between TiO2–H2Chl and (ZnChl)n was observed at 640 nm after excitation at the Qy peaks, 680 nm and 720 nm. This CT state is entirely different from the CT states observed for either TiO2–H2Chl (TiO2–H2Chl/spiro-OMeTAD) or TiO2–(ZnChl)n systems. Due to the slower charge transfer process from H2Chl+ to TiO2 as compared to that from (ZnChl)n+ to H2Chl, the CT lifetimes of H2Chl–(ZnChl)n+ (t1 = 0.1 ps, t2 = 1.4 ps) excited at 720 nm are slightly shorter than that excited at 680 nm (t1 = 0.2 ps, t2 = 5.6 ps). The TAS results suggest that the interface of TiO2–H2Chl and (ZnChl)n not only transfers holes as spiro-OMeTAD does, but also provides a built-in field for charge dissociation between the two Chl species.
关键词： TiO2,charge transfer,biosolar cell,chlorophyll,time-resolved absorption spectroscopy
更新于2025-09-11 14:15:04
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Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats
摘要： Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about microbial-mediated carbon fluxes in extreme environments. Hence, the methodology of sample acquisition described in the very few studies available implies two major problems: A) high resolution data require a large number of samples, which is difficult to obtain in remote areas; B) unavoidable sample manipulation such as cutting, sawing, and melting of ice cores that leads to a misunderstanding of in situ conditions. In this study, a prototype device that requires neither sample preparation nor sample destruction is presented. The device can be used for in situ measurements with a high spectral and spatial resolution in terrestrial and ice ecosystems and is based on the Laser-Induced Fluorescence Emission (L.I.F.E.) technique. Photoautotrophic supraglacial communities can be identified by the detection of L.I.F.E. signatures in photopigments. The L.I.F.E. instrument calibration for the porphyrin derivates chlorophylla (chla) (405 nm laser excitation) and B-phycoerythrin (B-PE) (532 nm laser excitation) is demonstrated. For the validation of this methodology, L.I.F.E. data were ratified by a conventional method for chla quantification that involved pigment extraction and subsequent absorption spectroscopy. The prototype applicability in the field was proven in extreme polar environments. Further testing on terrestrial habitats took place during Mars analog simulations in the Moroccan dessert and on an Austrian rock glacier. The L.I.F.E. instrument enables high resolution scans of large areas with acceptable operation logistics and contributes to a better understanding of the ecological potential of supraglacial communities in the context of global change.
关键词： chlorophyll,glacial melt,laser-induced fluorescence emission (L.I.F.E.),ice,cryospheric habitats,phycoerythrin,non-invasive
更新于2025-09-11 14:15:04
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The visible reflectance spectrum stability and water content resistivity of natural dye coating paint film consisting chlorophyll
摘要： The purpose of this paper is to study the colour stability and water content resistivity of the green colour coating paint film (consisting of chlorophyll) during exposure to ultraviolet A (UV-A). The natural green dye was prepared by immersing Cassia alata L. leaves in absolute ethanol. The extract was prepared in two batches of dye samples where one of it was a pure dye and the other was added with 3 Wt. % Cu(NO3)2 as an additive. Polymer blend as a binder was prepared by mixing poly(methyl methacrylate) (PMMA) and commercial acrylic polyol. The blended polymer was mixed with the natural dye in a specific ratio and applied as coating paint film on glass panel surfaces. The visible spectrum stability (colour stability) and water content resistivity of the coating paint films during exposure to UV-A were monitored. Addition of Cu(NO3)2 had improved the colour stability of the coating paint film. Fourier transform infrared spectroscopy analysis showed that both coating paint films do not absorb water and are resistive to water content. The ability of Cu(NO3)2 as an colour stability additive to the natural green dye applied in the coating paint film. The coating paint film developed in this work is suitable to be applied on glass substrates. The colour stability of the coating paint film was analysed by using the reflectance spectrum.
关键词： Chlorophyll,Colour stability,Natural dye,Paints,Organic coatings
更新于2025-09-11 14:15:04
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[IEEE 2018 7th International Conference on Agro-geoinformatics (Agro-geoinformatics) - Hangzhou (2018.8.6-2018.8.9)] 2018 7th International Conference on Agro-geoinformatics (Agro-geoinformatics) - Improved Estimation of Leaf Chlorophyll Content from Non-Noon Reflectance Spectra of Wheat Canopies by Avoiding the Effect of Soil Background
摘要： Crop leaf chlorophyll content (LCC) is a valuable indicator for agronomists to make fertilization recommendation and can be estimated from canopy reflectance spectra. However, the estimation accuracy of LCC is often influenced by soil background. To alleviate the adverse effect of soil background, this study proposed to collect spectral measurements at non-noon (such as 14:00-16:00 local time) hours and evaluated the performance of these spectral measurements with experimental data and radiative transfer model. The results from the wheat experiment conducted at Rugao demonstrated that the canopy spectra measured at non-noon were less sensitive to the soil background compared with those collected at midday (such as 12:00), which improved the estimation accuracy (R2) for LCC from 0.71 to 0.77. A canopy radiative transfer model called 4SAIL-RowCrop was also used to validate the performance and feasibility of the non-noon measurement scheme. One thousand spectra with different combinations of LCC, soil reflectance, and canopy structure were simulated at three observation times (12:00, 14:00 and 16:00). The CIred-edge calculated from the canopy reflectance spectra simulated for 16:00 exhibited a higher correlation to LCC (R2 = 0.76) than that for 12:00 (R2 = 0.43). These consistent findings from experimental and modeled datasets suggested that the effect of soil background can be alleviated and the estimation accuracy of LCC can be improved by determining a proper timing of spectral observation.
关键词： Remote sensing,Wheat,Leaf chlorophyll content,Non-noon observation,Soil Background
更新于2025-09-11 14:15:04
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[IEEE 2018 7th International Conference on Agro-geoinformatics (Agro-geoinformatics) - Hangzhou (2018.8.6-2018.8.9)] 2018 7th International Conference on Agro-geoinformatics (Agro-geoinformatics) - Retrieval of Leaf Chlorophyll Content of Paddy Rice with Extracted Foliar Hyperspectral Imagery
摘要： Retrieving foliar chlorophyll content with canopy spectral data is critical for understanding the growing status and yield estimation of paddy rice. However, given the field of view of rice canopy is a mixture of plant organs (i.e., leaves, stems and spikes) and backgrounds (i.e., water, soil and gaps), spectral signals from the targeted portions were disturbed by other portions, thus result in a limited accuracy for foliar chlorophyll content estimation, particularly when the canopy closure was low. As an advanced remote sensing technology, hyperspectral imaging sensors could collect information from both image and spectral dimensions, which allows identification and separation of different plant portions and backgrounds within the scene. Based on this principle, this paper proposed a method using refined spectrum for retrieving rice foliar chlorophyll content. The experimental data consisted of 58 hyperspectral images of rice canopy that were obtained by a Cubert S185 hyperspectral imager. Besides, corresponding chlorophyll content of rice leaves was measured with a SPAD meter. To retrieve foliar chlorophyll contents with refined spectra, a spectral purification procedure was established. Background of rice images was firstly removed by a decision tree method. Then, rice spikes could be removed according to an object-oriented classification which thus left the portion of rice leaves. Vegetation indices were extracted from the refined leaf spectra and were correlated with foliar chlorophyll content. Comparing with the performance of vegetation indices with original canopy hyperspectral data in retrieving foliar chlorophyll content, results suggested that retrieving accuracy based on refined spectra resulted in a significant improvement. The proposed spectral purification procedure helps to mitigate the background impact by wiping out those non-target spectral signals, which thus substantially improve the retrieval accuracy. Such a method can lay a good foundation for subsequent development of some built-in algorithms for in-situ sensors and UAV remote sensing platforms.
关键词： Chlorophyll Content,Spectral purification,Retrieving Accuracy,Hyperspectral
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Validation of the Sentinel-3 Ocean and Land Colour Instrument (OLCI) Terrestrial Chlorophyll Index (OTCI): Synergetic Exploitation of the Sentinel-2 Missions
摘要： Continuity to the Medium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI) will be provided by the Sentinel-3 Ocean and Land Colour Instrument (OLCI), and to ensure its utility in a wide range of operational applications, validation efforts are required. In the past, these activities have been constrained by the need for costly airborne hyperspectral data acquisition, but the Sentinel-2 Multispectral Instrument (MSI) now offers a promising alternative. In this paper, we explore the synergetic use of Sentinel-2 MSI data for validation of the Sentinel-3 OLCI Terrestrial Chlorophyll Index (OTCI) over the Valencia Anchor Station, a large agricultural site in the Valencian Community, Spain. High retrieval accuracy (RMSE = 0.20 g m-2) was obtained by applying machine learning techniques to Sentinel-2 MSI data, highlighting the valuable information it can provide when used in synergy with Sentinel-3 OLCI data for land product validation.
关键词： validation,Vegetation biophysical variables,Sentinel-2,Sentinel-3,canopy chlorophyll content
更新于2025-09-11 14:15:04
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The Unique Photophysical Properties of the Peridinin-Chlorophyll-a-Protein
摘要： Peridinin-Chlorophyll-a-Proteins (PCPs) are water-soluble light harvesting complexes from dinoflagellates. They have unique light-harvesting and energy transfer properties which have been studied in details in the last 15 years. This review aims to give an overview on all the main aspects of PCPs photophysics, with an emphasis on some aspects which have not been reviewed in details so far, such as vibrational spectroscopy studies, theoretical calculations, and magnetic resonance studies. A paragraph on the present development of PCPs towards technological applications is also included.
关键词： peridinin-chlorophyll-protein,peridinin,Carotenoids,photoprotection.,light-harvesting
更新于2025-09-11 14:15:04