scholarly journals Generation of Ketene With High Quantum Yield by a KrF Laser

1985 ◽  
Vol 5 (5) ◽  
pp. 257-273 ◽  
Author(s):  
Zhang Yunwu ◽  
W. Fuss ◽  
K. L. Kompa ◽  
F. Rebentrost
Keyword(s):  
Thermal Decomposition ◽  
Single Step ◽  
Quantum Yields ◽  
Methyl Radicals ◽  
High Quantum ◽  
Photochemical Formation ◽  
A Chain ◽  
Technical Interest ◽  
Approximate Rate ◽  
Pulsed Laser Irradiation

Acetone was photolyzed around 770 K by pulsed laser irradiation at 248 nm. The methyl radicals, generated in the primary step, trigger a chain reaction, producing ketene (CH2CO) and methane. Long chains (high quantum yields) result from low radical concentrations. Using a collimated laser beam of low intensity, quantum yields up to 300 have been demonstrated. Approximate rate constants have been derived and used for extrapolation to higher temperatures and different densities. Compared to the thermal process, the photochemical formation of ketene is faster. Therefore its thermal decomposition can be avoided to some extent. But the improvement is probably too small to be of technical interest. We also found indications that the thermal decomposition of acetone above about 500 to 600 K yields three fragments in a single step.

Photolysis of hydrogen peroxide, photocatalytic effects of Cu(II) and reaction kinetics

1986 ◽  
Vol 51 (5) ◽  
pp. 973-981 ◽  
Author(s):  
Stanislav Luňák ◽  
Petr Sedlák ◽  
Josef Vepřek-Šiška
Keyword(s):  
Hydrogen Peroxide ◽  
Thermal Decomposition ◽  
Quantum Yield ◽  
Reaction Kinetics ◽  
Copper Ions ◽  
Oxidation States ◽  
Radiation Temperature ◽  
Quantum Yields ◽  
High Quantum ◽  
Catalytically Active

The quantum yield of hydrogen peroxide photolysis has been measured as a function of the concentration of photocatalytically active Cu2+ ions, intensity of photolytic radiation, temperature, and hydrogen peroxide concentration. The results obtained are consistent with the concept that high quantum yields of hydrogen peroxide photolysis (Φ >> 1) are due to thermal decomposition of hydrogen peroxide catalyzed by photochemically generated copper ions in oxidation states which are catalytically active.

Highly efficient orange-red electroluminescence of iridium complexes with good electron mobility

2017 ◽  
Vol 5 (32) ◽  
pp. 8150-8159 ◽  
Author(s):  
Hua-Bo Han ◽  
Rong-Zhen Cui ◽  
Yi-Ming Jing ◽  
Guang-Zhao Lu ◽  
You-Xuan Zheng ◽  
...  
Keyword(s):  
Current Efficiency ◽  
Electron Mobility ◽  
Quantum Yields ◽  
Iridium Complexes ◽  
Maximum Luminance ◽  
High Quantum ◽  
Highly Efficient ◽  
Maximum Current ◽  
Low Efficiency

Two orange-red iridium complexes with high quantum yields and good electron mobility were applied in efficient OLEDs showing a maximum luminance of 129 466 cd m−2, a maximum current efficiency of 62.96 cd A−1 with low efficiency roll-off.

scholarly journals Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

2014 ◽  
Vol 10 ◽  
pp. 672-679 ◽  
Author(s):  
Fabian Klukas ◽  
Alexander Grunwald ◽  
Franziska Menschel ◽  
Thomas J J Müller
Keyword(s):  
Natural Products ◽  
Electronic Structure ◽  
Biologically Active ◽  
Blue Luminescence ◽  
Quantum Yields ◽  
One Pot ◽  
Dft Computations ◽  
High Quantum ◽  
Bright Blue ◽  
Coupling Sequence

2,5-Di(hetero)arylfurans are readily accessible in a pseudo five-component reaction via a Sonogashira–Glaser coupling sequence followed by a superbase-mediated (KOH/DMSO) cyclization in a consecutive one-pot fashion. Besides the straightforward synthesis of natural products and biologically active molecules all representatives are particularly interesting due to their bright blue luminescence with remarkably high quantum yields. The electronic structure of the title compounds is additionally studied with DFT computations.

Reactions of Thiyl Radicals. XI. Further Investigations of Thiol–Disulfide Photolyses in the Liquid Phase

1973 ◽  
Vol 51 (9) ◽  
pp. 1410-1415 ◽  
Author(s):  
Donna D. Carlson ◽  
Arthur R. Knight
Keyword(s):  
Liquid Phase ◽  
Room Temperature ◽  
Liquid Mixtures ◽  
Quantum Yields ◽  
Chain Reaction ◽  
Photochemical Process ◽  
High Quantum Efficiency ◽  
Thiyl Radicals ◽  
Exchange Processes ◽  
A Chain

The photolysis of C2H5SH liquid at 2537 Å has been shown to give H2 and C2H5SSC2H5 at equal rates with a quantum yield of 0.25. The photolysis of ethanethiol – methyl disulfide liquid mixtures leads, via a chain reaction involving propagation by attack of thiyl radicals on the disulfide S—S bond, to the formation with high quantum efficiency of CH3SH, C2H5SSC2H5 and, as an intermediate that is consumed after long exposures, CH3SSC2H5. The net result of the sequence of exchange processes is the essentially irreversible conversion of the methyl disulfide into methanethiol. The same overall reaction occurs thermally at room temperature, but the rate is appreciably less than that of the photochemical process. The quantum yields of formation of the unsymmetrical disulfides arising from the photochemically initiated exchange reaction in equimolar mixtures of CH3SSCH3 + n-C3H7SSC3H7 and C2H5SSC2H5 + n-C3H7SSC3H7 have been shown to be 6.9 and 4.4, compared to 355 for CH3-SSCH3 + C2H5SSC2H5 mixtures. In all three types of system examined in this investigation all thiyl radicals can be accounted for stoichiometrically on the basis of exchange and combination reactions alone, indicating negligible disproportionation of these species in condensed phase.

Un exemple d'isomérisation radicalaire en chaînes: la photoinduction de l'isomérisation cis–trans de la pentène-3 one-2

1977 ◽  
Vol 55 (22) ◽  
pp. 3915-3926 ◽  
Author(s):  
Armel Rioual ◽  
André Deflandre ◽  
Jacques Lemaire
Keyword(s):  
Energy Transfer ◽  
Quantum Yields ◽  
Unsaturated Ketone ◽  
Chain Process ◽  
Triplet Energy ◽  
Low Concentrations ◽  
Energy Transfers ◽  
Donor And Acceptor ◽  
A Chain ◽  
Triplet Energy Transfer

Mechanisms of the photosensitized cis–trans photoisomerization of 3-penten-2-one which do not imply only classical triplet–triplet energy transfer are proposed; they are based upon measurements of the variations of initial quantum yields of isomerization with the initial donor and acceptor concentrations, the wavelength of excitation, and the nature of the donor and of the solvent. Carbonyl donors (acetophenone, benzophenone, acetone) induce a radical isomerization by a chain process in reducing solvents; the example of acetophenone is specially interesting. In solvents in which the donor is not photoreduced (as benzene or CCl4) classical triplet–triplet energy transfers occur. Sensitization with aromatic donors (benzene, mesitylene) proceeds through triplet–triplet energy transfer at low concentrations of the acceptor. At higher concentrations of acceptor, an exciplex is formed between the ketone and the aromatic in its singlet excited state; this exciplex is deactivated by dissociation and by causing the isomerization of the α,β-unsaturated ketone.

Efficient red luminogen with aggregation-induced emission for in vivo three-photon brain vascular imaging

2020 ◽  
Vol 4 (6) ◽  
pp. 1634-1642 ◽  
Author(s):  
Haiyan Tian ◽  
Dongyu Li ◽  
Xi Tang ◽  
Yubo Zhang ◽  
Zhiyong Yang ◽  
...  
Keyword(s):  
High Resolution ◽  
Penetration Depth ◽  
Vascular Imaging ◽  
Quantum Yields ◽  
High Signal ◽  
Aggregation Induced Emission ◽  
Background Ratio ◽  
High Quantum

DCPE-TPA exhibits three morphologies with high quantum yields and nanoparticles of DCPE-TPA are utilized for in vivo 3PF imaging, achieving a penetration depth of 300 μm with a high resolution of 1.8 μm and a high signal-to-background ratio of 14.

Green and Orange Emissive Carbon Dots with High Quantum Yields Dispersed in Matrices for Phosphor-Based White LEDs

2020 ◽  
Vol 8 (8) ◽  
pp. 3151-3161 ◽  
Author(s):  
Panpan Ma ◽  
Xiaobo Sun ◽  
Wei Pan ◽  
Guifeng Yu ◽  
Jinping Wang
Keyword(s):  
Carbon Dots ◽  
Quantum Yields ◽  
White Leds ◽  
High Quantum
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