Laser Spectrofluorimetry of Chlorophylls

1974 ◽  
Vol 52 (22) ◽  
pp. 3723-3727 ◽  
Author(s):  
Roger M. Leblanc ◽  
Geneviève Galinier ◽  
Alain Tessier ◽  
Lise Lemieux
Keyword(s):  
Chlorophyll A ◽  
Emission Spectra ◽  
Polarization Rotator ◽  
Excitation Beam ◽  
Solid States ◽  
Set Up

A device has been set up to determine quantitatively the weak fluorescence intensities of pigment molecules. It consists of a laser spectrofluorimeter. The excitation beam can be produced with either a He/Cd laser (441.6 nm) or a He/Ne laser (632.8 nm). This system allows us to detect the fluorescence of dilute chlorophyll a or b solutions of the order of 10−12 mol/l. This sensitivity also permits the study of the emission spectra from chlorophyll in monomolecular or solid states, and since a polarization rotator has been incorporated into our apparatus, one may presume some possible orientation of the molecules.

scholarly journals Structure of the Red Fluorescence Band in Chloroplasts

1966 ◽  
Vol 49 (4) ◽  
pp. 763-780 ◽  
Author(s):  
Govindjee ◽  
Louisa Yang
Keyword(s):  
Chlorophyll A ◽  
Room Temperature ◽  
Emission Spectra ◽  
Matrix Analysis ◽  
Spinach Chloroplast ◽  
Excitation Spectra ◽  
Temperature Changes ◽  
Pigment System ◽  
Fluorescence Efficiency ◽  
Chlorophyll A And B

Using Weber's method of "matrix analysis" for the estimation of the number of fluorescent species contributing to the emission of a sample, it is shown that the fluorescence1 band in spinach chloroplast fragments at room temperature originates in two species of chlorophyll a. Emission spectra obtained upon excitation with different wavelengths of light (preferentially absorbed in chlorophyll a or b) are presented. Upon cooling to - 196°C, the fluorescence efficiency increases about twentyfold. Two additional bands, that now appear at 696 and 735 mµ, suggest the participation of four molecular species. Emission spectra observed at different concentrations of chloroplast fragments with excitation in chlorophyll a and b and excitation spectra for different concentrations of chloroplast fragments and measurements at 685 and 760 mµ are presented. Two of the four emission bands may belong to pigment system I and two to system II. The 685, 696, and 738 mµ bands respond differently to temperature changes. In the -196°C to -150°C range, the intensity of the 685 mµ band remains constant, and that of the 696 mµ band decreases twice as fast as that of the 738 mµ band.

scholarly journals High sensitivity fluorescence up-conversion spectroscopy of 3MLCT emission of metal-organic complexes

2019 ◽  
Vol 205 ◽  
pp. 09009 ◽  
Author(s):  
Li Liu ◽  
Damianos Agathangelou ◽  
Thomas Roland ◽  
Olivier Crégut ◽  
Thibaud Duchanois ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Emission Spectra ◽  
High Sensitivity ◽  
High Signal ◽  
Triplet States ◽  
Organic Complexes ◽  
Metal Organic ◽  
Set Up ◽  
Weak Luminescence

We demonstrate the implementation of a broadband fluorescence up-conversion set-up with high signal-to-noise ratio and dynamic range allowing for the detection of weak luminescence from triplet states in Fe(II) NHC complexes. Based on the experimentally determined radiative rates and the emission spectra, these states have dominant MLCT character.

Characterization of Light Emission from 4H and 6H SiC MOSFETs

2000 ◽  
Vol 640 ◽  
Author(s):  
P. J. Macfarlane ◽  
R. E. Stahlbush
Keyword(s):  
Light Emission ◽  
Broad Band ◽  
Emission Spectra ◽  
Spectral Studies ◽  
Attractive Alternative ◽  
Interface Trap ◽  
Electron Hole ◽  
Set Up ◽  
A Charge ◽  
Hole Recombination

ABSTRACTWhile SiC devices are an attractive alternative to Si in high power applications, interface trap densities measured in SiC-based MOSFETs are significantly larger than in Si-based ones. Here, we study SiC MOSFETs using both spatial images and spectral analysis of light emission due to electron-hole recombination. The light emission is produced by alternately driving the channel between accumulation and inversion using what is essentially a charge-pumping set-up. Emission is due to interface trap and bulk electron-hole recombination. The spatial imaging studies suggest that recombination occurs at both interface traps and bulk defects. Spectral studies of the emission indicate the presence of a narrow band centered at 425 nm and a broad band extending from approximately 500 to 800nm. The former we suggest is due to bulk recombination and the latter to interface trap recombination. The spectral studies of the 500 to 800 nm band are timed to separate light emitted during the inversion-to-accumulation transition from that emitted during the accumulation-to-inversion transition and visa versa. Comparisons of the emission spectra collected during these specific periods are consistent with a larger Dit in the upper half of the bandgap than the lower half in both 4H and 6H devices.

Emission Spectra of Chlorophyll‐a in Polar and Nonpolar Solvents

1967 ◽  
Vol 46 (9) ◽  
pp. 3334-3340 ◽  
Author(s):  
S. B. Broyde ◽  
S. S. Brody
Keyword(s):  
Chlorophyll A ◽  
Emission Spectra ◽  
Nonpolar Solvents

Fluorometric Properties of N-Methyltetraphenylporphine and Several Derivatives: Evaluation as Standards for Determination of Chlorophyll Concentrations

1982 ◽  
Vol 36 (4) ◽  
pp. 430-435 ◽  
Author(s):  
David K. Lavallee ◽  
Thomas J. McDonough ◽  
Lisa Cioffi
Keyword(s):  
Chlorophyll A ◽  
Organic Solvents ◽  
Fluorescence Spectra ◽  
Emission Spectra ◽  
Quantum Yields ◽  
Polar Organic Solvents ◽  
Solvent Systems ◽  
Nonpolar Organic ◽  
Chlorophyll Concentrations

As part of an ongoing study of the chemistry and properties of N-methylporphyrins and their metal complexes, we have observed that the excitation and emission spectra of N-methyltetraphenylporphyrin and N-methyltetra( p-sulfophenyl)porphyrin and their zinc complexes closely resemble corresponding spectra of chlorophyll a. We have characterized fluorescence spectra for these species in a variety of solvents commonly used for quantitative determination of chlorophylls. Quantum yields for the N-methylporphyrins are lower by approximately a factor of 10 than yields for chlorophyll a in such solvents as acetone, ethanol, and mixed aqueous/organic solvent systems. The yields are quite sufficient, however, for these species to be used as fluorescence standards. Solution of N-methylporphyrins are stable and the compounds can be inexpensively synthesized in high purity. The tetra( p-sulfophenyl) species are soluble in aqueous and highly polar organic solvents, whereas the tetraphenyl species are soluble in nonpolar organic solvents.

scholarly journals The influence of a magnetic field on radiation frequency

1897 ◽  
Vol 60 (359-367) ◽  
pp. 513-514 ◽  
Keyword(s):  
Magnetic Field ◽  
Emission Spectra ◽  
Radiation Frequency ◽  
Set Up ◽  
The University ◽  
Physical Fact

I ask permission to bring before tbe notice of the Fellows a notable discovery recently made at Leyden by Dr. P. Zeeman, who is now elected Professor of Physics in the University of Amsterdam. To put myself in order, I will state that I have set up apparatus suitable-for showing the effect, and have verified its primary feature, viz., that both lines in the ordinary spectrum of sodium are broadened when a magnetic field is concentrated upon the flame emitting the light. Zeeman has observed it likewise with lithium, and with absorption as well as with emission spectra; taking precautions against deception by spurious effects due to changes of density or of temperature. It is thus probably not a chemical fact, dependent on the nature of a substance, but a physical fact, dependent on the nature of radiation and absorption, i. e ., a fact connected with the interchange of energy between ether and matter.

Chlorophyll-Protein Complexes of Chlorella fusca

1980 ◽  
Vol 35 (7-8) ◽  
pp. 627-637 ◽  
Author(s):  
Aloysius Wild ◽  
Barbara Urschel
Keyword(s):  
Chlorophyll A ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Sodium Dodecyl ◽  
Chlorophyll B ◽  
Chlorella Fusca ◽  
Ps Ii ◽  
Chlorophyll Protein Complexes ◽  
Chlorophyll Protein ◽  
Set Up

Chlorophyll-protein complexes from thylakoids of the normal type and two mutants of Chlorella fusca were separated using sodium dodecyl sulfate acrylamide gel electrophoresis (PAGE). The properties of the chlorophyll-protein complexes of the three strains of Chlorella were compared. Standard curves were set up for the characterization of the chlorophyll-proteins. In every electrophoretic separation of chlorophyll-protein complexes, a certain amount of pigment is separated from the protein. We tried to keep that amount as low as possible by mild solubiliza­tion and by working in low temperature. Under these conditions, we obtained several new chlorophyll-proteins in addition to the P-700-chlorophyll a-protein (CP I) and the light-harvesting chlorophyll a/b-protein (CP II). Thus, a small band (CP I a) was located between the top of the gel and the CPI after elec­trophoresis. Although it shows spectral qualities similar to CP I, it possesses a much lower chloro­phyll a/chlorophyll b ratio. It may be an aggregate of photosystem I and light-harvesting chloro­phyll. We found and analyzed three other chlorophyll-proteins with electrophoretic mobilities inter­mediate between that of the P-700-chlorophyll a-protein and that of the light-harvesting chloro­phyll a/b-protein complex. Two of these chlorophyll-proteins, the LHCP1 and the LHCP2, have a low chlorophyll a/chlorophyll b ratio and spectral properties similar to that of the light-harvesting chlorophyll a/b-protein (LHCP3). They obviously represent dimers or oligomers of the latter com­plex. A third, new complex (CPa) migrated between LHCP3 and its dimer. With the chlorophyll b deficient mutant G 36 of Chlorella fusca, this complex could be obtained in high purity and great enrichment (15% of total chlorophyll). It could be proved that this complex only contains chloro­phyll a. Its red absorption maximum is at 671 nm. Some indirect evidences suggest that it may be a good candidate for the PS II reaction center complex.

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