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Photodriven reduction and oxidation reactions on colloidal semiconductor particles: Implications for prebiotic synthesis

Paper ID Volume ID Publish Year Pages File Format Full-Text
28917 44104 2007 11 PDF Available
Title
Photodriven reduction and oxidation reactions on colloidal semiconductor particles: Implications for prebiotic synthesis
Abstract

Photoelectrochemical reactions on mineral surfaces may have contributed to the synthesis of prebiotic molecules on early Earth. Laboratory experiments were conducted to develop this idea. Colloidal particles of ZnS were selected as a prototypical semiconducting mineral material. We investigated (1) the capability of the ZnS colloid to reduce aqueous CO2 under ultraviolet irradiation to yield formate in the presence of a sulfur hole scavenger and (2) to oxidize formate to yield CO2 in the absence of a hole scavenger. In the presence of the hole scavenger, the initial quantum efficiency is 10% for formate production from CO2 at pH 6.3. The reaction rate is sensitive to the pH of the solution, increasing with acidity for the pH range of 5–9. The initial formate production rate is proportional to the concentration of aqueous inorganic carbon from 13 to 65 mM, suggesting an absence of surface saturation. Photoproducts other than formate also form, including acetate and propionate, a finding which demonstrates the formation of carbon–carbon coupling products. In the absence of hole scavenger but in the presence of the ZnS colloid, formate is photooxidized with a quantum efficiency of 1.1%. The likely presence of semiconducting colloidal particles in the oceans of the prebiotic Earth suggests that photochemical reactions on their surfaces could have played a significant role in the synthesis of organic molecules.

Keywords
Early Earth; Origin of life; Carbon fixation; Zinc sulfide
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Photodriven reduction and oxidation reactions on colloidal semiconductor particles: Implications for prebiotic synthesis
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 185, Issues 2–3, 25 January 2007, Pages 301–311
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us