scholarly journals THE PHOTOSYNTHETIC EFFICIENCY OF PHYCOCYANIN IN CHROOCOCCUS, AND THE PROBLEM OF CAROTENOID PARTICIPATION IN PHOTOSYNTHESIS

1942 ◽  
Vol 25 (4) ◽  
pp. 579-595 ◽  
Author(s):  
Robert Emerson ◽  
Charlton M. Lewis
Keyword(s):  
Quantum Yield ◽  
Absorption Spectra ◽  
Photosynthetic Efficiency ◽  
High Efficiency ◽  
Wave Length ◽  
Visible Spectrum ◽  
Living Cells ◽  
Reasonable Doubt ◽  
Carotenoid Pigments ◽  
Relative Absorption

The absorption spectra of the principal pigment components extracted from Chroococcus cells have been measured, and their sum compared with the absorption of a suspension of living cells. The agreement was sufficiently close so that it was concluded the absorption spectra of the extracted and separated pigment components could be used to obtain estimates of the relative absorption of the various components in the living cells. The quantum yield of Chroococcus photosynthesis was measured at a succession of wave lengths throughout the visible spectrum, and the dependence of yield on wave length was compared with the proportions of light absorbed by the pigment components. This comparison showed beyond reasonable doubt that the light absorbed by phycocyanin is utilized in photosynthesis with an efficiency approximately equal to that of the light absorbed by chlorophyll. The light absorbed by the carotenoid pigments of Chroococcus seems for the most part to be unavailable for photosynthesis. The results leave open the possibility that light absorbed by the carotenoids is active in photosynthesis, but with an efficiency considerably lower than that of chlorophyll and phycocyanin. It is also possible that the light absorbed by one or a few of the several carotenoid components is utilized with a high efficiency, while the light absorbed by most of the components is lost for photosynthesis.

scholarly journals THE RELATION OF TIME, INTENSITY AND WAVE-LENGTH IN THE PHOTOSENSORY SYSTEM OF PHOLAS

1928 ◽  
Vol 11 (5) ◽  
pp. 657-672 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Absorption Spectrum ◽  
Reaction Time ◽  
Absorption Spectra ◽  
Wave Length ◽  
Visible Spectrum ◽  
Ultra Violet ◽  
Fundamental Properties ◽  
Stimulation Of ◽  
The Way

The most effective point in the visible spectrum for the stimulation of Pholas is 550 mµ. On the red side, the effectiveness drops rapidly to almost zero. On the violet side, the effectiveness drops to about half, and rises again in such a way as to indicate a possible second maximum in the near ultra-violet. On the basis of certain ideas these data are assumed to represent the properties of the absorption spectrum of the photosensitive system in Pholas. A comparison with Mya shows that the absorption spectra of the photosensitive systems in the animals are distinctly different. Nevertheless the way in which intensity and reaction time are related in the two animals are found to be identical. The conclusion is then drawn from this and from previous work, that although the fundamental properties of the photoreceptor process show an identical organization in several different animals, the materials which compose these processes are specific.

scholarly journals LIGHT-INDUCED EFFICIENCY AND PIGMENT ALTERATIONS IN RED ALGAE

1958 ◽  
Vol 41 (6) ◽  
pp. 1113-1117 ◽  
Author(s):  
C. S. Yocum ◽  
L. R. Blinks
Keyword(s):  
Blue Light ◽  
Red Algae ◽  
Photosynthetic Efficiency ◽  
High Efficiency ◽  
Light Exposure ◽  
Action Spectrum ◽  
Green Light ◽  
Chromatic Adaptation ◽  
Carotenoid Pigments ◽  
Low Efficiency

The low photosynthetic efficiency of chlorophyll in freshly collected red algae, can, in the case of Porphyra perforata, P. nereocystis, and Porphyridium cruentum, be increased by growing the algae for 10 days in red or blue light. Exposure to darkness or to green light maintains the algae in their originally low efficiency with respect to chlorophyll, while retaining the high efficiency of phycobilins. Red- or blue-adapted algae are rapidly reversed by exposure to green light, the chlorophyll efficiency dropping to low values again in a few hours. This is assumed to account for the action spectrum of freshly gathered plants. Some pigment changes were observed, but not in the direction of "chromatic adaptation;" and the carotenoid pigments were not activated, even by blue light, but remained as photosynthetically inactive shading filters. The higher red algae (Florideae) did not show activation of chlorophyll by red or blue light.

scholarly journals Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 17
Author(s):  
Eldred Lee ◽  
Kaitlin M. Anagnost ◽  
Zhehui Wang ◽  
Michael R. James ◽  
Eric R. Fossum ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Quantum Yield ◽  
Photon Energy ◽  
High Efficiency ◽  
High Energy ◽  
Yield Enhancement ◽  
X Ray ◽  
Simulation Results ◽  
Conversion Efficiencies

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.

SYNTHESIS AND SPECTROSCOPY OF SOME QUATERNARY OXYFLUORIDE GLASSES DOPPED WITH COPPER

2013 ◽  
Vol 22 ◽  
pp. 284-291 ◽  
Author(s):  
CH. SRINIVASU ◽  
M. A. SAMI ◽  
A. EDUKONDALU ◽  
SYED RAHMAN
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Copper Ions ◽  
Wave Length ◽  
Broad Band ◽  
Spin Hamiltonian Parameter ◽  
Band Gap Energy ◽  
Site Symmetry ◽  
Optical Absorption Spectra ◽  
Absorption Data

Electron paramagnetic resonance (EPR) and optical absorption spectra of copper ions in xLiF-(50-x)Li2O-20SrO-30Bi2O3 glass system have been studied. MDSC studies showed that the glass transition temperature decreases with LiF content. Optical absorption spectra of the pure glasses reveled that the cut off wave length increased and optical band gap energy decreased with increase in LiF content. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The Cu2+ ions are in well-defined axial sites but subjected to small distortion leading to the broadening of the spectra. The spin-Hamiltonian parameter values indicate that the ground state of Cu2+ is d x2 y2 and the site symmetry around Cu2+ ions is tetragonally distorted octahedral. The optical absorption spectra exhibited a broad band corresponding to the d-d transition bands of Cu2+ ion. By correlating EPR and optical absorption data, the bond parameters are evaluated from various techniques.

Computational Study on Triphenylamine-Based Dyes Containing Benzimidazole Units for Dye-Sensitized Solar Cells

2013 ◽  
Vol 668 ◽  
pp. 110-114
Author(s):  
Zhong Quan Wan ◽  
Lin Lei Zhou ◽  
Chun Yang Jia ◽  
Xiao Jun Yao ◽  
Yu Shi
Keyword(s):  
Absorption Spectra ◽  
Molecular Orbital ◽  
High Efficiency ◽  
Computational Study ◽  
Electronic Absorption Spectra ◽  
Energy Levels ◽  
Dye Sensitized Solar Cells ◽  
Conduction Band Edge ◽  
Tio2 Electrode ◽  
Lowest Unoccupied Molecular Orbital

Three novel dyes (D1, D2 and D3) containing triphenylamine (TPA) unit as core and bearing different benzimidazole units as secondary electron-donors are designed. The geometries, electronic structures, and electronic absorption spectra of these dyes are studied by DFT and TD-DFT. The optimized results indicate that these dyes are all non-coplanar, which can help to inhibit the close intermolecular π-π stacking aggregation effectively. The lowest unoccupied molecular orbital (LUMO) energy levels of the dyes are higher than the conduction band edge of the TiO2, which ensures a high efficiency of electron transfer from these dyes to TiO2 electrode. As the highest occupied molecular orbital (HOMO) energy levels of these dyes are lower than those of I-/I-3, these molecules that lose electrons could be restored by getting electrons from electrolyte. The absorption spectra of these dyes are simulated, and the calculated results indicate that D3 can absorb more photons than those of D1, D2 and TPAR in the region from 250 to 580 nm, which should have the best performance of photo-to-electric conversion efficiency.

scholarly journals Tetra-fluorinated aromatic azide for highly efficient bioconjugation in living cells

RSC Advances ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 23-26 ◽  
Author(s):  
Xuekang Cai ◽  
Dan Wang ◽  
Yasi Gao ◽  
Long Yi ◽  
Xing Yang ◽  
...  
Keyword(s):  
High Efficiency ◽  
Living Cells ◽  
Highly Efficient ◽  
Aromatic Azide

A fast strain-promoted azide–alkyne cycloaddition based on tetra-fluorinated aromatic azide was developed and applied to label proteins and living cells with high efficiency.

Nanocrystalline semiconductor LEDs with simple structure and high efficiency

2003 ◽  
Vol 771 ◽  
Author(s):  
Dietrich Bertram ◽  
Volker Weiler ◽  
Dimitri Talapin ◽  
Horst Weller
Keyword(s):  
High Efficiency ◽  
Organic Materials ◽  
Visible Spectrum ◽  
Semiconductor Nanoparticles ◽  
Solution Chemistry ◽  
Inorganic Nanoparticles ◽  
Ambient Conditions ◽  
High Quality ◽  
Synthesis Conditions ◽  
Nanocrystalline Semiconductor

AbstractNanocrystalline semiconductor particles exhibit a size dependent bandgap emission, due to size quantisation effects. These particles are derived from solution chemistry and can be made monodisperse under the right synthesis conditions. Compared to organic materials, the inorganic nanoparticles show much higher stability against oxidation and degradation, which makes them an interesting candidate for LEDs and displays. So far, LEDs based on semiconductor nanoparticles typically included low stability organic materials to provide charge injection. The talk will present a new class of nanoparticle LEDs, made without sensitive organic materials. These LEDs show high efficiencies, well defined color throughout the red to green part of the visible spectrum and improved stability under ambient conditions without excessive encapsulation. Using high quality monodisperse suspensions, high color purity is achieved for the emission which paves the road to cheap, high quality displays based on inorganic semiconductor nanoparticles.

Sign in / Sign up

Export Citation Format

Share Document