Absorption Spectrum Of Chlorophyll Research Articles

Rare-earth-free Sr(Ca)2Ga2GeO7 phosphors with Ca-substitution-induced red-shift emission, perfectly aligned for Chlorophyll's absorption

Rare-earth-free Sr(Ca)2Ga2GeO7 phosphors exhibiting self-activated luminescence properties were synthesized by solid-state method. The incorporation of Ca in place of Sr resulted in a pronounced redshift in the emission spectrum, enabling a closer alignment with the absorption spectrum of chlorophyll. This advancement offers increased flexibility in designing blue LEDs optimized for diverse crop growth applications.

Photovoltaic Energy Production in Greenhouses With Spectral Splitting Solar Trackers

The spectral filtering low concentration photovoltaic system developed by Voltiris is an innovative solution for energy production in greenhouses without affecting food production. A first prototype was installed in the greenhouse of the agricultural research center Agroscope in Conthey, Switzerland. During an eight-month agronomic study from March to October, the yield of tomato, pepper bell and basil under this system was on a par with a control group. I-V curves were recorded to evaluate the photovoltaic system performance, and the impact of concentration and filtering. The curves showed that the prototype achieved a direct normal irradiation efficiency of 10.1 %. The specific power output of the Voltiris system inside the greenhouse was comparable to the one of a conventional solar panel placed outside. Filters with two different transmission spectra were used, both of which were matched to the absorption spectra of chlorophyll and reflected 50 % and 60 % of the incident global radiation respectively. To transfer the performance of the system to other greenhouses, the transmittance of the test greenhouse and its glass cover were measured for global and diffuse radiation. This allowed to determine the transmittance of the greenhouse specific metal structure. In the test greenhouse, the overall transmission coefficient for direct solar radiation was 0.28, hence limiting the system yield.

A narrow-band blue emitting phosphor by co-doping Bi3+ and alkali metal ions (Li+, Na+ and K+) with dual luminescence center

The technology of solid-state lighting has developed for decades in various industries. Phosphor, as an element part, determines the application domain of lighting products. For instance, blue and red-emitting phosphors are required in the process of plant supplementing light, arrow-band emitting phosphors are applied to backlight displays, etc. In this work, a Bi3+-activated blue phosphor is obtained in a symmetrical and compact crystal structure of Gd3SbO7 (GSO). Then, the co-doping strategy of alkali metal ions (Li+, Na+, and K+) is used to optimize the performance. The result shows that the photoluminescence intensity is increased by 2.1 times and 1.3 times respectively by introducing Li+ and K+ ions. Not only that, it also achieves narrow-band emitting with the full width of half-maximum (FWHM) reaching 42 nm through Na+ doping, and its excitation peak position also shifts from 322 to 375 nm, which can be well excited by near-ultraviolet (NUV) light emitting diode (LED) chips (365 nm). Meanwhile, the electroluminescence spectrum of GSO:0.6 mol%Bi3+,3 wt%Na+ matches up to 93.39% of the blue part of the absorption spectrum of chlorophyll a. In summary, the Bi3+-activated blue phosphor reported in this work can synchronously meet the requirements of plant light replenishment and field emission displays.

A novel light source for post-harvest lettuce preservation based on chlorophyll absorption spectrum

With increased consumers’ demand for safe and healthy food, LED lighting for photobiology has received wider attention. In order to prolong the preservation time of the post-harvest lettuce, this paper documents a novel light source designed for preservation based on the chlorophyll absorption spectrum. Effects of intermittent exposure (35 μmol m−2 s−1) on sensory quality and chlorophyll content in fresh lettuce were investigated during 3 days storage at 20°C ± 1°C and 60% ± 1% humidity using dark as the control. The results show that the lighting reduced the colour difference value of lettuce by 23.5% compared with the dark. The content of chlorophyll was 19.7% more than in the dark. The lighting with the novel light source inhibited the decline in the colour difference value − a/ b of lettuce and delayed the degradation of chlorophyll.

A novel reddish‐orange emitting NaSrBiTeO6:Sm3+ phosphor with high moisture resistance and thermostability for horticultural light emitting diode applications

AbstractA sequence of reddish‐orange emitting NaSrBi(1−x)TeO6:xSm3+ phosphors were successfully composited by a favorable solid‐phase chemical process. The sintering temperature is optimized as 850°C. NaSrBiTeO6 (NSBTO):Sm3+ samples were assigned to the cubic double‐perovskite structure, exhibiting the space group of Fmm (225). Photoluminescence emission spectra display the main peaks at 562, 598, 645, and 705 nm at 404 nm excitation. Among them, the most intense emission peak is at 645 nm. The concentration‐quenching mechanism of Sm3+ follows the interaction between electric dipoles and quadrupoles. The asymmetric ratio (I(4G5/2‐6H9/2)/I(4G5/2‐6H5/2) of NSBTO:2 mol%Sm3+ phosphor is extracted as 4.96. The optimum NSBTO:2 mol%Sm3+ phosphor has excellent thermal stability with a remained emission intensity riches 93.61% (420 K). After testing with high‐pressure water steam at various periods, the phosphor remains chemically stable for moisture resistance. For the NSBTO:2 mol%Sm3+ phosphor, the satisfactory color purity and low correlated color temperature (CCT) are obtained with 99.9% and 1494 K, respectively. The electroluminescence spectra of the prepared red light emitting diode (LED) are in conformity with the phytochrome absorption spectra of chlorophyll a, chlorophyll b, PFR, and PR. The white light‐emitting diode (w‐LED) is also perfectly packaged, obtaining an efficient color rendering index (Ra) of 92.12 and CCT of 5553 K. These exceeding optical properties certified that NaSrBi(1−x)TeO6:xSm3+ demonstrates promising prospects and can be efficiently applied in horticultural LED applications.

Synthesis of Bi3+ and Eu3+ co-doped Na4CaSi3O9 blue-red light tunable emission phosphors for inducing plant growth

Sunlight is an important factor in plant growth. In this regard, both blue and red lights provide significant contributions. Blue–red light dual-emission phosphors, which can be achieved by regulating energy transfer between two independent luminous centers, have recently been investigated extensively. In this study, Bi3+ and Eu3+ co-doped Na4CaSi3O9 (NCSO: Bi3+, Eu3+) phosphors are successfully synthesized via a high-temperature solid-phase method at approximately 900 °C for a few hours. X-ray powder diffraction is used to verify the crystal structure, phase purity, and structural refinement of the NCSO-based phosphors. Upon light excitation at 299 nm, the phosphors show blue–red dual emission. The blue emission (300–500 nm) may have originated from the 3P1 → 1S0 transition of Bi3+, whereas the red emission (575–725 nm) is attributable to the 5D0 → 7FJ (J = 1, 2, 3 and 4) transition of Eu3+ ions. Energy transfer from Bi3+ to Eu3+ is systematically investigated and the thermal stability of the phosphors is analyzed using temperature-dependent spectroscopy. The emission spectra of NCSO: Bi3+, Eu3+ are consistent with the absorption spectra of chlorophyll a, chlorophyll b, phytochrome PR, and phytochrome PFR. These results indicate that the obtained phosphors exhibit significant potential for inducing plant growth.

High thermally stable deep red-emitting Sb3+,Ho3+-codoped Cs2NaScCl6 double perovskite for plant lighting

Lead-free halide double perovskite has received widespread attention due to its excellent optical performance. However, the lack of deep red light and poor heat quenching resistance severely limit its application in plant lighting field. In this work, Ho3+ was introduced into the thermally stable Cs2NaScCl6 host, exhibiting a deep red emission of 660 nm. By constructing an energy transfer channel between Sb3+ and Ho3+, the photoluminescence quantum yield (PLQY) of Cs2NaScCl6:1%Sb3+,40%Ho3+ rises up to 53.8%, that is increased by 17 times, and its emission intensity can still be maintained by 80% at 423 K, exhibiting good heat quenching resistance. The obtained Cs2NaScCl6:1%Sb3+,40%Ho3+ and Cs2NaScCl6:1%Sb3+ with blue light emission were employed for fabricating a light-emitting diode (LED) device with a 340 nm UV chip, and its emission spectrum matches well the absorption spectra of chlorophyll A and chlorophyll B with the high resemblance of 70% and 75%, making it suitable for use as an artificial light source to control the growth process of plants in the field of plant lighting.

Photonics of plant chloroplasts

It is shown that the features of light propagation in plant leaves depend on the long-range ordering in chloroplasts and spectral characteristics of pigments. It has been established that, with regard of the dispersion of the chlorophyll absorption spectrum, the photonic density of states increases and the spectral peak shifts to the effective photosynthesis wavelength range, which enhances the probability of the photosynthesis processes.

On the importance and challenges of modelling extraterrestrial photopigments via density-functional theory

The emergence of oxygenic photosynthesis was a major event in Earth’s evolutionary history and was facilitated by chlorophylls (a major category of photopigments). The accurate modelling of photopigments is important to understand the characteristics of putative extraterrestrial life and its spectral signatures (detectable by future telescopes). In this paper, we perform a detailed assessment of various time-dependent density-functional theory (TD-DFT) methods for predicting the absorption spectra of chlorophyll a, with particular emphasis on modern low-cost approximations. We also investigate a potential extraterrestrial photopigment called phot0 and demonstrate that the electronegativity of the metal ion may exert a direct influence on the locations of the absorption peaks, with higher electronegativity inducing blue-shifting and vice-versa. Based on these calculations, we established that global-hybrid approximations with a moderate percentage of exact exchange – such as M06 and PW6B95 – are the most appropriate compromise between cost and accuracy for the computational characterisation of photopigments of astrobiological interest. We conclude with a brief assessment of the implications and avenues for future research.

Structure and luminescence of a high-efficient blue-red-emitting Na2BaMg(PO4)2: Eu2+, Mn2+ phosphor for plant growth LEDs

New dual-emitting phosphor Na2BaMg(PO4)2: Eu2+, Mn2+ is prepared via conventional sintering method. The structural and luminescent properties of as-synthesized phosphor were systematically studied by experimental characterization and theoretical calculation. Utilizing the Eu2+→Mn2+ energy transfer, this phosphor exhibits efficient double-band emissions at 415 and 620 nm, which has a good match with the absorption spectra of chlorophyll A/B and phytochrome in plants. The energy transfer mechanism had been investigated through emission intensity and decay lifetime variation using Reisfeld's approximation method. Na2BaMg(PO4)2: Eu2+, Mn2+ shows promising properties like good thermal stability (75% emission intensity maintenance at 200 °C) and high quantum efficiency (QE > 80%). A prototype LED was fabricated using optimized phosphor and NUV chip, which exhibits two distinct emission peaks modulating an optimum action spectrum for plant absorption. All results indicate that Na2BaMg(PO4)2: Eu2+, Mn2+ is of great potential as converted component for plant growth LEDs.

An efficient protocol for excited states of large biochromophores.

Efficient energy transport in photosynthetic antenna is a long-standing source of inspiration for artificial light harvesting materials. However, characterizing the excited states of the constituent chromophores poses a considerable challenge to mainstream quantum chemical and semiempirical excited state methods due to their size and complexity and the accuracy required to describe small but functionally important changes in their properties. In this paper, we explore an alternative approach to calculating the excited states of large biochromophores, exemplified by a specific method for calculating the Qy transition of bacteriochlorophyll a, which we name Chl-xTB. Using a diagonally dominant approximation to the Casida equation and a bespoke parameterization scheme, Chl-xTB can match time-dependent density functional theory's accuracy and semiempirical speed for calculating the potential energy surfaces and absorption spectra of chlorophylls. We demonstrate that Chl-xTB (and other prospective realizations of our protocol) can be integrated into multiscale models, including concurrent excitonic and point-charge embedding frameworks, enabling the analysis of biochromophore networks in a native environment. We exploit this capability to probe the low-frequency spectral densities of excitonic energies and interchromophore interactions in the light harvesting antenna protein LH2 (light harvesting complex 2). The impact of low-frequency protein motion on interchromophore coupling and exciton transport has routinely been ignored due to the prohibitive costs of including it in simulations. Our results provide a more rigorous basis for continued use of this approximation by demonstrating that exciton transition energies are unaffected by low-frequency vibrational coupling to exciton interaction energies.

Rhodopsin driven microbial CO2 fixation using synthetic biology design.

Rhodopsin driven microbial CO2 fixation using synthetic biology design.

Conversion of UV light to dazzling reddish orange light with robust color purity for plant growth in biocompatible glasses

Remarkable red luminescence was achieved from synthesized lithium zinc borate glasses (LBZ) composed of Eu3+ and Gd3+ ions by melt quenching for greenhouse applications. LBZ: Gd3+ glass exhibited emission at 311 nm (6P7/2→8S7/2) upon 265 nm excitation. By exciting at 393 nm, LBZ: Eu3+ glass emits a dazzling reddish-orange emission at 612 nm (5D0→7F2). Due to successful energy migration from Gd3+ to Eu3+, co-doped glasses generate more exquisite reddish light at 612 nm with high color purity than independently (Eu3+) doped glass under 265 nm of UV irradiation. Various fluorescence methods were used to demonstrate energy transmission. Notably, the enhanced luminescence extending from 580 to 700 nm pertaining to co-doped glasses was correlated with the absorption spectrum of chlorophyll. The results of in vitro cell viability confirm the non-cytotoxicity and a high level of biocompatibility. From the results, the non-cytotoxic co-doped (1.0Gd3+-1.0Eu3+)-glass has been found to be a potential candidate as a biocompatible greenhouse glass for plant growth.

Metal To Metal Charge Transfer Induced Efficient Yellow/Far‐Red Luminescence in Na2Ca3(Nb, Ta)2O9:Bi3+ toward the Applications of White‐LEDs and Plant Growth Light

AbstractRed and far‐red spectral components are the basics for color rendering improvement of illumination devices and growth regulation of plants, respectively. Establishing a feasible design principle in solid state materials for the red/far‐red phosphors is significant but challenging. Realizing metal to metal charge transfer (MMCT) in Bi3+‐doped phosphors is a new strategy to target the red/far‐red luminescence. As a proof of concept, the MMCT state involving the ground state of Bi3+ ion and the excited state of host (Nb/Ta)5+ cations in Na2Ca3(Nb, Ta)2O9:Bi3+ induces efficient and tunable yellow/far‐red luminescence (peaking at 597–667 nm). Moreover, benefited from the appropriate distance between Bi3+ and (Nb/Ta)5+ ions, Na2Ca3(Nb, Ta)2O9:Bi3+ possess intense absorption in near‐ultraviolet region and no absorption in visible region. The plant growth light with the blending of Na2Ca3Nb2O9:Bi3+ far‐red phosphor and BAM:Eu2+ blue phosphor yields broadband electroluminescence covering almost the entire absorption spectra of chlorophyll and phytochrome, which is superior to the Cr3+‐ and Mn4+‐based light‐emitting diode (LED) devices. The white‐LED device by employing Na2Ca3Ta2O9:Bi3+ yellow phosphor as the essential component yields full‐spectrum warm white light with high color indexes.

Novel Dual-Excitation and Dual-Emission Materials: Eu2+,Pb2+ Co-doped Core-Shell-Structured CaS@CaZnOS Phosphors and Their Application for Highly Efficient Photosynthesis of Plants.

Eu2+,Pb2+-doped core-shell-structured CaS@CaZnOS phosphors were synthesized by a two-step high-temperature solid-phase method. The as-synthesized CaS:Eu2+,Pb2+@CaZnOS:Pb2+ phosphors possess excellent dual-excitation and dual-emission (DE2) luminescent properties, which give rise to red emission peaking at 650 nm under green excitation, derived from the core CaS:Eu2+,Pb2+, and blue emission peaking at 424 nm, originating from the shell CaZnOS:Pb2+, under ultraviolet (UV) excitation. In addition, tunable red/blue emission can be achieved by changing the doping concentration of Pb2+ in the CaZnOS shell. The red/blue dual emission of core-shell DE2 phosphors under excitation of UV and green light significantly matches with the absorption spectrum of chlorophyll (a, b); hence, the as-prepared phosphors are excellent solar spectral conversion (SSC) auxiliaries of plastic films or laminated glass for greenhouses and provide ideas for creating more efficient and practically valuable SSC auxiliaries. The DE2 properties are described, and the energy transfer mechanism from Pb2+ to Eu2+ in the core is proposed and discussed in detail.

Investigation of Chlorophyl-a Derived Compounds as Photosensitizer for Photodynamic Inactivation

Chlorophyll has unique physicochemical properties which makes them good as photosensitizer of Photodynamic Inactivation (PDI). The physicochemical properties of chlorophyll as photosensitizer can be optimized through several routes. One of the possible route is by replacing the metal ion center of chlorophyll with other ions. In this research, the effect of coordinated metal ion in the natural chlorophyll-a was studied for bacterial growth (S. aureus) inhibition. The replacement of metal in the center of chlorophyll hopefully can improve the intensity of Intersystem Crossing Mechanism (ISC) lead to the formation of singlet oxygen species. The chlorophyll a and b were isolated from spinach via precipitation technique using 1,4 dioxane and water. The chlorophyll a and b were separated using sucrose column chromatography. The thin layer chromatography result showed that chlorophyll a (Rf: 0.57) had been well separated with chlorophyll b (Rf: 0.408). The absorption spectra of chlorophyll a and b showed that the Soret band was observed at 411 and 425 nm, while the Q band appeared at 663 and 659 nm. Replacement of metal ion center shifted the Soret band of chlorophyll- a derivatives to lower energy region, while Q-band was slightly shifted to the higher energy region. The absorption and the fluorescence intensity were also observed decreasing after ion replacement. The Inhibition activity investigation over S. aureus showed the highest inhibition activity was exhibited by Zn-pheophytin-a (66.8%) followed by chlorophyll a (30.1 %) and Cu-pheophytin-a (0%). The inhibition activity is correlated with decreasing fluorescence intensity. The formation of singlet oxygen by ISC mechanism is hypothesized to deactivate the excitation state of Cu-pheophytin-a. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Tunable blue-red dual emission via energy transfer in Na4CaSi3O9: Ce3+, Mn2+ phosphors for plant growth LED

Along with the rapid development of modern agriculture, plant growth requires better light quality. Blue and red light play a crucial role in plant growth, so achieving blue-red dual light emission is urgently needed. The energy transfer (ET) between two independent luminous centers is an effective means to regulate the blue-red dual emission. Hence, Ce3+-Mn2+ co-doped Na4CaSi3O9 (NCSO) phosphors are successfully synthesized by a conventional high-temperature solid-state method. The crystal structure and phase purity of NCSO phosphors are confirmed by X-ray powder diffraction (XRD) and Rietveld structure refinement. Ce3+ and Mn2+ co-doped NCSO phosphors exhibit blue - red dual emission under the excitation of 336 nm. The blue emission mainly comes from the 5d-4f transition of Ce3+, while the red emission belongs to the 4T1(4G)-6A1(6S) spin-forbidden transition of Mn2+. The emission spectra of NCSO: Ce3+, Mn2+ is in good agreement with the absorption spectra of chlorophyll. The ET process from Ce3+ to Mn2+ is studied and the temperature-dependent luminescence is examined to verify the thermal stability of phosphor. These results indicate that the as-obtained phosphors may have potential applications in plant growth lighting.

Simulation of plant growth spectrum with high-fitness based on spectral segmentation fitting

Light emitting diodes (LEDs) are considered next-generation light sources. Because of their narrow spectral distribution, fast response and convenient adjustment, LEDs are widely used in spectrally adjustable light sources. In order to determine the best combination of LEDs to obtain a high-fitness plant growth spectrum, in this paper we use Gaussian function model to construct the spectral distribution of monochromatic LEDs, choose the absorption spectrum of chlorophyll b as the target spectrum. Divide the spectrum into gentle wavebands and steep wavebands and use the combination of equal-interval and unequal-interval peak wavelength LEDs to fit the target spectrum, then compared eight experiments and determined the best number of LEDs used in different wavebands of the target spectrum. Finally, this paper use the LEDs of Epitex series to fit target spectrum, experimental results show that correlation coefficient R2 can reach 0.9673 and 0.9675.

Design of highly efficient deep-red emission in the Mn4+ doped new-type structure CaMgAl10O17 for plant growth LED light.

The auxiliary light equipment for plant growth requires phosphor-converted light-emitting-diodes (pc-LEDs) with high luminous efficiency and a stable structure, and the properties of phosphors highly determine the performance of the pc-LEDs. This work reports a deep-red emitting phosphor with an ultra-wide response range which is regarded as CaMgAl10O17:Mn4+. The absorption range spans the ultraviolet, near-ultraviolet, blue, and green light regions from 250 to 550 nm. Under the excitation of the best excitation position at 343 nm, deep-red light at 654 nm is emitted, and the quantum efficiency is as high as 86.7%. The luminous efficiency of the two pc-LED devices prepared based on CaMgAl10O17:Mn4+ with 395 and 460 nm chips reached 54.3 and 59.6 lm W-1, respectively. The spectra of the two pc-LEDs exhibit high resemblance to the absorption spectra of chlorophyll A and B in plant growth photosynthesis. These indicate that the CaMgAl10O17:Mn4+ phosphor can be an excellent candidate for plant growth LED light.

Accurate Computation of the Absorption Spectrum of Chlorophyll a with Pair Natural Orbital Coupled Cluster Methods.

The ability to accurately compute low-energy excited states of chlorophylls is critically important for understanding the vital roles they play in light harvesting, energy transfer, and photosynthetic charge separation. The challenge for quantum chemical methods arises both from the intrinsic complexity of the electronic structure problem and, in the case of biological models, from the need to account for protein–pigment interactions. In this work, we report electronic structure calculations of unprecedented accuracy for the low-energy excited states in the Q and B bands of chlorophyll a. This is achieved by using the newly developed domain-based local pair natural orbital (DLPNO) implementation of the similarity transformed equation of motion coupled cluster theory with single and double excitations (STEOM-CCSD) in combination with sufficiently large and flexible basis sets. The results of our DLPNO–STEOM-CCSD calculations are compared with more approximate approaches. The results demonstrate that, in contrast to time-dependent density functional theory, the DLPNO–STEOM-CCSD method provides a balanced performance for both absorption bands. In addition to vertical excitation energies, we have calculated the vibronic spectrum for the Q and B bands through a combination of DLPNO–STEOM-CCSD and ground-state density functional theory frequency calculations. These results serve as a basis for comparison with gas-phase experiments.