Photochemistry of Complex Ions. III. Absolute Quantum Yields for the Photolysis of Some Aqueous Chromium(III) Complexes. Chemical Actinometry in the Long Wavelength Visible Region
01 Feb 1966-Journal of the American Chemical Society (American Chemical Society)-Vol. 88, Iss: 3, pp 394-404
About: This article is published in Journal of the American Chemical Society.The article was published on 1966-02-01. It has received 362 citations till now. The article focuses on the topics: Photodissociation.
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TL;DR: In this article, the inverse photosensitized oxidative transformation of tetraethylated rhodamine (RhB) under visible illumination of aqueous titania dispersions is demonstrated.
Abstract: Chemical oxygen demand (CODCr) and proton NMR, UV−vis, and spin trapping EPR spectroscopic evidence is presented to demonstrate the inverse photosensitized oxidative transformation of tetraethylated rhodamine (RhB) under visible illumination of aqueous titania dispersions. Both de-ethylation and oxidative degradation take place with the former proceeding in a stepwise manner to yield mono-, di-, tri-, and tetra-de-ethylated rhodamine species. Intermediates present after each de-ethylation step remain in a fast dynamic equilibrium between the titania particle surface and the bulk solution. The concentration of •OH radicals, formed from the inverse photosensitization process through the superoxide radical anion, increases upon addition of the anionic dodecylbenzene sulfonate surfactant (DBS) because a larger number of RhB excited states are able to inject an electron into the conduction band of the TiO2 particles. Also, intermediates that can no longer absorb the visible light, (i.e., once the dye solution ...
948 citations
TL;DR: In this article, a mechanism for the present CO2 photoreduction process is presented; it involves separate pathways for CO and formate generation, in which the [Re(bpy) (CO)3X] complex plays the role of both the photoactive and the catalytic center.
Abstract: [fac-Re(bpy) (CO)3Cl] (bpy = 2,2′-bipyridine) is an efficient homogeneous catalyst for the selective and sustained photochemical or electrochemical reduction of CO2 to CO. A quantum yield of 14% and a faradic efficiency of 98% were measured in the presence of excess Cl− ions. The photochemical process took place under visible-light irradiation and consumed a tertiary amine as electron donor. A formato-rhenium complex was isolated in the absence of excess Cl− ions. Substitution by Cl− ion generated free formate, but no CO was detected. Luminescence measurements showed that the tertiary amine quenches the metal-to-ligand charge-transfer excited state of the rhenium complex via a reductive mechanism, with a rate constant of 3.4 × 107M−1S−1. The 19e-complex [Re(bpy) (CO)3X]− produced either photochemically or electrochemically appears to be the active precursor in the CO-generation process. Detailed spectroscopic studies on 13C-enriched carbonyl-rhenium and formato-rhenium complexes derived from 13C-enriched CO2 were performed in order to confirm the origin of the products and to study the exchange of the ligands. A mechanism for the present CO2 photoreduction process is presented; it involves separate pathways for CO and formate generation, in which the [Re(bpy) (CO)3X] complex plays the role of both the photoactive and the catalytic center.
581 citations
TL;DR: In this paper, the photodegradation of H2O2 occurred via a zero-order process, and •OH radicals were detected by electron paramagnetic resonance experiments in visible-light-irradiated aqueous TiO2 suspensions.
Abstract: Photodecomposition of hydrogen peroxide on TiO2 surfaces under visible irradiation (λ > 420 nm) was investigated, and an interesting result was found that small organic compounds such as salicylic acid were degraded in the presence of TiO2 and H2O2 under visible irradiation, although either TiO2 or H2O2 alone cannot absorb visible light to decompose H2O2 or small organic compounds. Furthermore, the effects of H2O2 concentration, pH, and the wavelength of irradiation light on the degradation of H2O2 were studied. The photodegradation of H2O2 occurred via a zero-order process, and •OH radicals were detected by electron paramagnetic resonance experiments in visible-light-irradiated aqueous TiO2 suspensions. A reaction mechanism for the decomposition of H2O2 on the TiO2 surfaces is proposed involving a photoinduced electron transfer of the surface complexes of ⋮TiIV−OOH.
322 citations
TL;DR: In this article, the photo-assisted degradation of alizarin red mediated by TiO2 particles under visible light radiation was proposed, and the photodegradation kinetics were discussed in terms of the Langmuir−Hinshelwood model, a case of saturation type kinetics.
Abstract: Alizarin red undergoes rapid photoassisted decomposition in air-equilibrated aqueous TiO2 dispersions under visible light radiation (λ > 420 nm). Proton NMR, chemical oxygen demand (CODCr), UV−visible, IR, GC−MS, and spin-trapping ESR spectroscopic techniques were employed to obtain details of the photodegradation of alizarin red. Peroxides and carbonyl species are the first intermediates observed during the process. The major component of the peroxides produced is H2O2, and no organoperoxides were detected. We have also confirmed that in addition to CO2 and to smaller carbonyl species the principal intermediate produced is phthalic acid, which is unable to degrade further because it does not absorb the actinic visible light radiation (λ > 420 nm). The photodegradation kinetics are discussed in terms of the Langmuir−Hinshelwood model, a case of saturation type kinetics. A mechanism for the photoassisted degradation of alizarin red mediated by TiO2 particles under visible light radiation is proposed.
253 citations
01 Jan 1982
TL;DR: In this paper, a proper assessment of microbial absorption of light energy is provided for any studies on photosynthetic microorganisms, including the analysis of excessive growth of blue-green algae in waters, evaluation of light-energy conversion efficiency, etc.
Abstract: Needless to say, any studies on photosynthetic microorganisms should be accompanied by a proper assessment of microbial absorption of light energy whatever the purposes of these works might be — biomass production, analysis of excessive growth of blue- green algae in waters, evaluation of light-energy conversion efficiency, etc.
212 citations