Photoelectromotive Force (PEMF) Studies of [Fe(CN)5SCN]3- Complex Ions Adsorbed on Pb(SCN)2 Semiconductor Surfaces

2001 ◽  
Vol 66 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Horst Hennig ◽  
Athanasios Kokorakis ◽  
Stefan Fränzle ◽  
Cornelia Damm ◽  
Franz W. Müller ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Visible Region ◽  
Laser Flash ◽  
Semiconductor Surfaces ◽  
Spectral Sensitization ◽  
Complex Ions ◽  
Hole Trapping ◽  
Photoelectromotive Force

Adsorbates of [Fe(CN)5SCN]3- complex ions on semiconducting Pb(SCN)2 surfaces were subject to photoelectromotive force (PEMF) investigations. Laser flash excitation of the adsorbates at 560 nm yields a weak PEMF signal due to spectral sensitization of the semiconductor Pb(SCN)2, not absorbing in the visible region. PEMF signals observed with laser flash excitation at 337 nm are explained by hole trapping accompanied with photoinduced redox reactions of the complex, when the number of flashes is increased.

Photocatalytic redox reactions with metalloporphyrins

2020 ◽  
Vol 24 (01n03) ◽  
pp. 21-32 ◽  
Author(s):  
Shunichi Fukuzumi ◽  
Yong-Min Lee ◽  
Wonwoo Nam
Keyword(s):  
Hydrogen Evolution ◽  
Redox Reactions ◽  
Bond Formation ◽  
Visible Region ◽  
Photosynthetic Reaction Center ◽  
Structure And Function ◽  
Free Base ◽  
Redox Catalyst ◽  
Redox Active ◽  
And Function

Metalloporphyrinoids are utilized as efficient sensitizers and catalysts in photosynthesis and the reverse reaction that is respiration. Because metalloporphyrinoids show strong absorption in the visible region and redox active, metalloporphyrinoids are also suited as photoredox catalysts for photo-driven redox reactions using solar energy. In particular, metalloporphyrins are utilized as pivotal components to mimic the structure and function of the photosynthetic reaction center. Metalloporphyrins are used as photoredox catalysts for hydrogen evolution from electron and proton sources combining hydrogen evolution catalysts. Metalloporphyrins also act as thermal redox catalysts for photocatalytic reduction of CO2 with photoredox catalysts. Metalloporphyrins are also used as dual catalysts for a photoredox catalyst for oxygenation of substrates with H2O and a redox catalyst for O2 reduction when dioxygen is used as a two-electron oxidant and H2O as an oxygen source, both of which are the greenest reactants. Free base porphyrins can also be employed as promising photoredox catalysts for C–C bond formation reactions.

Energy-transfer studies on phthalocyanine–BODIPY light harvesting pentad by laser flash photolysis

2015 ◽  
Vol 19 (01-03) ◽  
pp. 261-269 ◽  
Author(s):  
Mohamed E. El-Khouly ◽  
Cem Göl ◽  
Morad M. El-Hendawy ◽  
Serkan Yeşilot ◽  
Mahmut Durmuş
Keyword(s):  
Energy Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Visible Region ◽  
Geometry Optimization ◽  
Laser Flash ◽  
Zinc Phthalocyanine ◽  
Nanosecond Laser ◽  
Artificial Photosynthetic ◽  
Photosynthetic Antenna

A molecular pentad, comprised of zinc phthalocyanine ( ZnPc ) with four boron dipyrromethene units (BODIPY) have been examined by femtosecond and nanosecond laser flash photolysis to explore its photoinduced intramolecular events from the excited BODIPY. The geometry optimization showed that the phthalocyanine moiety is completely symmetric and form perfect square planar complex with zinc. The absorption spectrum of ZnPc -BODIPY pentad covers most of the visible region (ca. 300–750 nm), which clearly is an advantage for capturing solar energy. The excitation transfer from the singlet BODIPY to ZnPc is envisioned due to good spectral overlap of the BODIPY emission and ZnPc absorption spectra. Femtosecond laser flash photolysis studies provided concrete evidence for the occurrence of energy transfer from the singlet excited BODIPY to ZnPc in tetrahydrofuran. The kinetic study of energy transfer measured by monitoring the decay of the BODIPY emission revealed fast energy transfer (5.90 × 1010 s-1) in the molecular pentad. Since the electron transfer from the singlet ZnPc to BODIPY is thermodynamically not feasible, the singlet ZnPc decayed to populates the triplet ZnPc , in addition to the grounds state. These findings suggest the potential of the examined ZnPc -BODIPY pentad to be efficient photosynthetic antenna in the artificial photosynthetic systems.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

STRUCTURE OF CLEAN III-V SEMICONDUCTOR SURFACES

1989 ◽  
Vol 50 (C7) ◽  
pp. C7-119-C7-128
Author(s):  
M. SAUVAGE-SIMKIN
Keyword(s):  
Semiconductor Surfaces
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