Spectra Of Chlorophyll Research Articles

Estimating leaf SPAD values of freeze-damaged winter wheat using continuous wavelet analysis

Freeze injury, one of the most destructive agricultural disasters caused by climate, has a significant impact on the growth and production of winter wheat. Chlorophyll content is an important indicator of a plant's growth status. In this study, we analyzed the hyperspectral reflectance of normal and freeze-stressed leaves of winter wheat using a spectro-radiometer in a laboratory. The response of the chlorophyll spectra of plants under freeze stress was analyzed to predict the severity of freeze injury. A continuous wavelet transform (CWT) was conducted in conjunction with a correlation analysis, which generated a correlation scalogram that summarized the correlation between the chlorophyll content (SPAD value) and wavelet power at different wavelengths and decomposition scales. A linear regression model was established to relate the SPAD values and wavelet power coefficients. The results indicated that the most sensitive wavelet feature (region E: 553 nm, scale 5, R2 = 0.8332) was located near the strong pigment absorption bands, and the model based on this feature could estimate the SPAD value with a high coefficient of determination (R2 = 0.7444, RMSE = 7.359). The data revealed that the chlorophyll content of leaves under different low temperatures treatments could be accurately estimated using CWT. Also, this emerging spectral analytical approach can be applied to other complex datasets, including a broad range of species, and may be adapted to estimate basic leaf biochemical elements, such as nitrogen, cellulose, and lignin.

Li2SrSiO4:Ce3+, Pr3+ Phosphor with Blue, Red, and Near‐Infrared Emissions Used for Plant Growth LED

Ce3+/Pr3+ codoped Li2SrSiO4 (LSS) phosphors with blue, red, and near‐infrared (NIR) tri‐emission have been prepared via a high‐temperature solid‐state reaction method. Under the excitation of 200 to 400 nm near‐ultraviolet (n‐UV), the photoluminescence (PL) spectra of phosphors are composed of visible and NIR two parts. The former exhibits blue and red emission bands centered at around 428 nm from 5d–4f transition of Ce3+ and 611 nm from 1D2 → 3H4 transition of Pr3+, those overlap with photosynthesis action spectra of plants and absorption spectra of chlorophylls and carotenoids. While the later presents a broad NIR emission band peaking near 1039 nm caused by the 1G4 → 3H4 of Pr3+, matching with the absorption of bacteriochlorophyll. Their emission intensity ratios (B: R: NIR) could be tuned by altering the relative ratios of Ce3+ and Pr3+ concentration in the phosphors to meet the requirements of multifarious plants and bacteria. The efficient energy transfer from Ce3+ to Pr3+ takes place in the LSS host, which ascribed to an exchange interaction according to PL spectra and decay curves of phosphors. Results suggest that the present LSS: Ce3+, Pr3+ phosphors have great potential applications in plant growth n‐UV LED.

Highly matched spectrum needed for photosynthesis in Ce3+/Er3+/Yb3+ tri-doped oxyfluoride glass ceramics

A series of oxyfluoride glass ceramics containing CaF2 nano-crystals tri-doped with Ce3+/Er3+/Yb3+ ions were prepared by high temperature melting method and subsequent heat treatment. The structural properties were examined by X-ray diffraction measurements. The absorption, excitation, and emission spectra of the glass ceramics were investigated. Difference in erbium emission spectra between glass and glass ceramics had been studied. The emission bands originating from the 4F9/2 state of Er3+ were enhanced when the CaF2 nano-crystal created. By down-converting the ultraviolet wavelength region (280∼400 nm) light and up-converting the near-infrared wavelength region (900∼1100 nm) light, the glass ceramics can also emit strong reddish orange emission. The emission spectra consisting of bluish violet (400∼500 nm) and reddish orange (640∼680 nm) bands match well with the action spectrum of photosynthesis and absorption spectra of chlorophylls. Our materials will be favored to promote the development of glass greenhouses for green plant.

Free energies for the coordination of ligands to the magnesium of chlorophyll-a in solvents

The coordination of bases to chlorophyll magnesium modifies spectroscopic properties in solution as well as in situ in reaction centres. We evaluate the free energies of complexation of one or two pyridine, 1-propanol, diethyl ether or water solvent molecules at 298 and 150 K to rationalise observed phenomena. Various a priori dispersion-corrected density functional theory calculations are performed as well as second-order Møller–Plesset calculations, focusing on the effects of dispersion modifying the intermolecular interactions, of dispersion modifying solvation energies, of entropy, and of basis-set superposition error. A process of particular interest is magnesium complexation in ether at low temperature that is often exploited to assign the Q-band visible absorption spectrum of chlorophyll. Recently, we demonstrated that trace water interferes with this process, but the nature of the resulting complex could not be uniquely determined; here, it is identified as ether.Chlorophyll-a.H2O, consistent with interpretations based on our authoritative 2013 assignment.

How does the β-ionone effect the spectra of chlorophyll and the excitation energy transfer in solution

This paper presents the excitation spectra and fluorescence spectra of mixed solution containing chlorophyll a(Chla), chlorophyll b(Chlb) and β-ionone of different concentration, investigates the spectral changes of Chla and Chlb caused by β-ionone through optimizing the frontier orbital of Chl-β-ionone compound, and calculates the energy transfer rate between Chla and Chlb by means of the fluorescence Gauss decomposition. The results show that the β-ionone interacts with Chl mainly via the connection between the magnesium atom in Chl molecule and the carbonyl in β-ionone molecule. The formation of Chl-β-ionone compound changes the charge distribution of Chl so greatly that it leads to the red-shift of the excitation spectra and blue-shift of the fluorescence spectra of Chls. Also in the compound the electronic energy located on carbon double bond of β-ionone can be transferred to Chl molecule by the Mg…O bond, which enhances the fluorescence intensity greatly. The calculation of the excitation energy transfer (EET) rate indicates that a small amount of β-ionone can promote the EET between Chla and Chlb.

A multifrequency virtual spectrometer for complex bio-organic systems: vibronic and environmental effects on the UV/Vis spectrum of chlorophyll a.

The subtle interplay of several different effects means that the interpretation and analysis of experimental spectra in terms of structural and dynamic characteristics is a challenging task. In this context, theoretical studies can be helpful, and as such, computational spectroscopy is rapidly evolving from a highly specialized research field toward a versatile and widespread tool. However, in the case of electronic spectra (e.g. UV/Vis, circular dichroism, photoelectron, and X-ray spectra), the most commonly used methods still rely on the computation of vertical excitation energies, which are further convoluted to simulate line shapes. Such treatment completely neglects the influence of nuclear motions, despite the well-recognized notion that a proper account of vibronic effects is often mandatory to correctly interpret experimental findings. Development and validation of improved models rooted into density functional theory (DFT) and its time-dependent extension (TD-DFT) is of course instrumental for the optimal balance between reliability and favorable scaling with the number of electrons. However, the implementation of easy-to-use and effective procedures to simulate vibrationally resolved electronic spectra, and their availability to a wide community of users, is at least equally important for reliable simulations of spectral line shapes for compounds of biological and technological interest. Here, such an approach has been applied to the study of the UV/Vis spectra of chlorophyll a. The results show that properly tailored approaches are feasible for state-of-the-art computational spectroscopy studies, and allow, with affordable computational resources, vibrational and environmental effects on the spectral line shapes to be taken into account for large systems.

Distinguishing Electronic and Vibronic Coherence in 2D Spectra by Their Temperature Dependence

Long-lived oscillations in 2D spectra of chlorophylls are at the heart of an ongoing debate. Their physical origin is either a multipigment effect, such as excitonic coherence, or localized vibrations. We show how relative phase differences of diagonal- and cross-peak oscillations can distinguish between electronic and vibrational (vibronic) effects. While direct discrimination between the two scenarios is obscured when peaks overlap, their sensitivity to temperature provides a stronger argument. We show that vibrational (vibronic) oscillations change relative phase with temperature, while electronic oscillations are only weakly dependent. This highlights that studies of relative phase difference as a function of temperature provide a clear and easily accessible method to distinguish between vibrational and electronic coherences.

Pulse shaping based two-dimensional electronic spectroscopy in a background free geometry

We demonstrate a "drop-in" modification of the pulse-shaped pump-probe geometry two-dimensional Fourier transform spectrometer that significantly improves its performance by making the measurement background-free. The modification uses a hybrid diffractive optic/pulse-shaping approach that combines the advantages of background-free detection with the precise timing and phase-cycling capabilities enabled by pulse-shaping. In addition, we present a simple new method for accurate phasing of optically heterodyned two-dimensional spectra. We demonstrate the high quality of data obtainable with this approach by reporting two-dimensional Fourier transform electronic spectra of chlorophyll a in glycerol/water at 77 K.

The Dependence of the Photocurrent on the Concentration of Electron Mediator (Para-Benzoquinone) in Thylakoids

The photocurrent harvested from the isolated thylakoids has been investigated as a function of concentration of electron mediator. This photocurrent measured has been verified indeed from the photosynthesis on the thylakoid membranes. The photocurrent has a linear dependence on light intensity; the photocurrent shares similar frequency dependence as that of absorption spectrum of chlorophyll; the photocurrent decreases or disappears with the application of 3-(3',4'-dichlorophenyl)-1,1-dimethylurea as an inhibitor. A new finding of a peak in the photocurrent as a function of the concentration CBQ of electron mediator para-benzoquinone (p-BQ) has been reported here. It is found that the photocurrent measured increases at small CBQ, and a maximum current is obtained at CBQ approximately equal to 1.8-2 mM and decreases with further increase in CBQ. A simplistic model has been proposed to explain the peak. The effect of bias voltage applied between the electrodes on photocurrent is studied as well.

Noninvasive Measurement of Membrane Potential Modulation in Microorganisms: Photosynthesis in Green Algae

Cell membrane potential (CMP) modulation is a physical measurement to quantitatively probe cell physiology in real time at high specificity. Electrochemical field effect transistors (eFETs) made from graphene and Si nanowire provide strong mechanical and electrical coupling with neurons and muscle cells to noninvasively measure CMP at high sensitivity. To date, there are no noninvasive methods to study electrophysiology of microorganisms because of stiff cell walls and significantly smaller membrane polarizations. An eFET made from the smallest possible nanostructure, a nanoparticle, with sensitivity to a single-electron charge is developed to noninvasively measure CMP modulation in algae. The applicability of the device is demonstrated by measuring CMP modulation due to a light-induced proton gradient inside the chloroplast during photosynthesis. The ∼9 mV modulation in CMP in algae is consistent with the absorbance spectrum of chlorophyll, photosynthetic pathway, and inorganic carbon source concentration in the environment. The method can potentially become a routine method to noninvasively study electrophysiology of cells, such as microorganisms for biofuels.

Computational Analysis of Chlorophyll Structure and UV-Vis Spectra: A Student Research Project on the Spectroscopy of Natural Complexes

ABSTRACT Chlorophyll was extracted from fresh spinach leaves (Spinacia L.) and its absorption spectrum was recorded. Computational methods were used to optimize the geometry and energy of chlorophyll as well as to compute UV-Vis spectra of chlorophylls a and b and to compare them with the spectrum of chlorophyll extract. Chlorophyll bands are well predicted, especially with B3LYP/CIS and TD-B3LYP methods. This research project forms a modern approach to the process of spectroscopy teaching—students can apply quantum-mechanics calculations for understanding of reaction mechanisms with the involvement of biologically active compounds and learn to interpret the absorption spectra of chlorophyll extract obtained by themselves.

Study of chlorophyll and macromutations induced by gamma rays and sodium azide in urd bean (Vigna mungo L. Hepper).

The mutagenic effect of gamma rays (5, 10, 20, 30, 40, 50 and 60 kR) and sodium azide (1, 2, 3, 4, 5, 6 and 7 mM) alone or in combination (10 kR + 2 mM, 20 kR + 2 mM, 30 kR + 2 mM and 40 kR + 2 mM) on frequency and spectrum of chlorophyll and micromutations in cultivar, T9 of urd bean have been observed. The spectrum of chlorophyll mutations consisted of albina, chlorina, viresence, viridis and xentha. Out of these chlorophyll mutations, xantha type was predominant in both mutagenic treatments. Conclusively, the combination treatments have yielded the higher frequency, and various doses of mutagenic agents have independent response towards macromutations in bean cv-T9. These studies were broadly aimed at understanding the process of mutation, testing the efficacy of various mutagens, identifying optimum dose and best method of treatment; isolation of mutants of basic and applied value; elucidating the biological effects of gamma rays and sodium azide. Key words: Gamma rays, sodium azide (SA), chlorophyll, macro mutations, urd bean.

Preparation and Application of Light Conversionfilm Forexploiting Solar Energy

For take fully advantage of solar energy, the blue light conversion agent Ca0.6Sr0.4F2:Eu2+,Sm3+and the red light conversion agent CaS:Eu2+ were prepared in this paper. X-ray power diffraction (XRD) analysisconfirmed the phase formationof these light conversion agents.The luminescence intensity influencedby theconcentration of rare-earth-doped was discussed.Measuring results revealed thatthe blue and red agents canabsorb 375nm, 570nm radiations and emit 435nm, 640nmlight, respectively.The emitting spectra of them are matchedwith the absorption spectrum of chlorophyll. Light conversion film was prepared by introducing light conversion agents into polyethylene (PE). The trials of vegetables plantingin greenhouses that covered by conversion filmsindicate thatconversion films are able to enhance the availability of solar energy, and accelerate the ripening of vegetables, increase yield higher than 19.8%.

The peak effect of the photocurrent on the concentration of electron mediator (para-benzoquinone) in thylakoids

Abstract This work investigates the photocurrent harvested from the isolated thylakoids. Several tests have been used to verify that the photocurrent measured is indeed from the photosynthesis on the thylakoid membranes. The photocurrent has a linear dependence on light intensity; the photocurrent shares similar frequency dependence as that of absorption spectrum of chlorophyll; the photocurrent decreases or disappears with the application of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea as an inhibitor. The new finding of this report is the observation of a peak in the photocurrent as a function of the concentration CBQ of electron mediator para-benzoquinone (p-BQ). It is found that the photocurrent measured increases at small CBQ, and a maximum current is obtained at CBQ ≈ 1.8–2 mM and decreases with further increase in CBQ. A simplistic model has been proposed to explain the peak. The effect of bias voltage applied between the electrodes on photocurrent is studied as well.

Spectroscopic and biocatalytic properties of a chlorophyll-containing extract in silica gel

UV–Vis absorption and fluorescence spectra of chlorophyll a (in the form of spinach extract) in acetone solution and in silica gel showed a predominance of pigment dimers in its overall concentration and an evident transformation of chlorophyll a to pheophytin with time. The dimerization constant of chlorophyll a in acetone was logKdim=2.14, whereas the constants for chlorophyll a and pheophytin a in alcogel were logKdim=4.70 and logKdim=5.22, respectively. Biocatalytic experiments indicated the possibility of using the pigment embedded in silica gel, i.e. mainly its dimeric form, for biotransformation of α-pinene to pinocarveyl hydroperoxide, trans-pinocarveol, pinocarvone and myrtenal. The advantage of a heterogeneous biocatalytic system (composed of a solvent and silica gel) over a homogeneous system (single phase of chloroform) is the possibility of reusing the biocatalyst with about 10% preservation of its activity.

Single-phased silicate-hosted phosphor with 660 nm-featured band emission for biological light-emitting diodes

A single-phased (Ba,Sr)3MgSi2O8:Eu2+, Mn2+ phosphor with 660 nm-featured dual band-emission is investigated upon optimizing composition to simulate the artificial photosynthetic action spectrum (PAS) for near-ultraviolet (NUV) biological light-emitting diodes (bio-LEDs). A specific composition range in Ba–Sr binary solid solution of (Ba,Sr)3MgSi2O8 is found to be capable of obtaining single-phased host in the absence of an easily formed orthosilicate impurity, leading to a 660 nm-featured red band emission of Mn2+ induced by an efficient energy transfer from a co-doped blue-emitting Eu2+ sensitizer. This dual broad band emission phosphor has a 72 nm full width at half maximum (FWHM) for red band that covers fairly well to the absorption spectrum of chlorophyll and PAS for most plants, enabling a flexible option in the application of bio-illumination for artificial photosynthesis.

Spectroscopic Properties of Chlorophyll f

The absorption and fluorescence spectra of chlorophyll f (newly discovered in 2010) have been measured in acetone and methanol at different temperatures. The spectral analysis and assignment are compared with the spectra of chlorophyll a and d under the same experimental conditions. The spectroscopic properties of these chlorophylls have further been studied by the aid of density functional CAM-B3LYP and high-level symmetric adapted coupled-cluster configuration interaction calculations. The main Q and Soret bands and possible sidebands of chlorophylls have been determined. The photophysical properties of chlorophyll f are discussed.

Purely absorptive fifth-order three-dimensional electronic spectroscopy

We demonstrate a method to measure a purely absorptive fifth-order three-dimensional (3D) electronic spectrum based on a pulse-shaper assisted pump-probe beam geometry setup. The 3D spectra are measured as a function of two independently controlled population times. With phase-cycling and data processing, purely absorptive 3D spectra of chlorophyll a are obtained.

Chelating effect of leek (Allium tuberosum Rottler ex Sprengel) containing chlorophyll on Cd, Pb, and As

Effect of leek (Chinese chive) on bioaccessibility of arsenic (As), cadmium (Cd), and lead (Pb) was determined in comparison with sodium copper chlorophyllin (SCC) using in vitro digestion model. Leek (0, 6, 12, 60, and 120 mg) and SCC (0, 1, 5, 10, and 50 mg) were digested with equal concentration (10 ppm) of As, Cd, and Pb. Concentration of each heavy metal in aqueous phase following in vitro digestion was measured using an inductively coupled plasma optical emission spectrometer. Changes in absorbance spectra of chlorophyll extracted from leek and SCC by heavy metals were measured at 0, 1, 2, and 3 h after mixing. Results showed that the concentration of each heavy metal in aqueous phase decreased with increasing amounts of leek and SCC. At the highest level of leek (120 mg), the concentrations of As, Cd, and Pb decreased to 93.9, 87.1, and 58.2%, respectively. Absorbance of chlorophyll drastically decreased after 1 h of mixing with each As, Cd, and Pb, and no difference in the absorbance was observed after 2 and 3 h. This result indicates that mixing chlorophyll extracted from leek with each heavy metal for 1 h was sufficient for chelating As, Cd, and Pb ions. On the other hand, SCC and each heavy metal showed a decreasing pattern of absorbance without any significant difference for 3 h, indicating that chlorophyll from leek was more effective than SCC, a commercial grade chlorophyll derivative, in chelating As, Cd, and Pb. Results showed leek reduces heavy metals in humans.

Effects of Substituents on Synthetic Analogs of Chlorophylls. Part 3: The Distinctive Impact of Auxochromes at the 7‐ versus 3‐Positions

Assessing the effects of substituents on the spectra of chlorophylls is essential for gaining a deep understanding of photosynthetic processes. Chlorophyll a and b differ solely in the nature of the 7-substituent (methyl versus formyl), whereas chlorophyll a and d differ solely in the 3-substituent (vinyl versus formyl), yet have distinct long-wavelength absorption maxima: 665 (a) 646 (b) and 692 nm (d). Herein, the spectra, singlet excited-state decay characteristics, and results from DFT calculations are examined for synthetic chlorins and 13(1)-oxophorbines that contain ethynyl, acetyl, formyl and other groups at the 3-, 7- and/or 13-positions. Substituent effects on the absorption spectra are well accounted for using Gouterman's four-orbital model. Key findings are that (1) the dramatic difference in auxochromic effects of a given substituent at the 7- versus 3- or 13-positions primarily derives from relative effects on the LUMO+1 and LUMO; (2) formyl at the 7- or 8-position effectively "porphyrinizes" the chlorin and (3) the substituent effect increases in the order of vinyl < ethynyl < acetyl < formyl. Thus, the spectral properties are governed by an intricate interplay of electronic effects of substituents at particular sites on the four frontier MOs of the chlorin macrocycle.