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Effects of surface-anchoring mode and aggregation state on electron injection from chalcogenorhodamine dyes to titanium dioxide

Paper ID Volume ID Publish Year Pages File Format Full-Text
27503 44027 2013 8 PDF Available
Title
Effects of surface-anchoring mode and aggregation state on electron injection from chalcogenorhodamine dyes to titanium dioxide
Abstract

•We have used transient absorption spectroscopy to measure relative electron-injection yields from selenorhodamine dyes to titanium dioxide.•Electrons were injected approximately twice as efficiently from dyes anchored to TiO2 via carboxylate linkages than via phosphonate linkages.•For a given anchoring mode, electrons were injected approximately twice as efficiently from H-aggregated dyes than from non-aggregated dyes.

We used transient absorption spectroscopy to characterize excited-state electron injection from a 2,7-bis(dimethylamino)-9-(5-phosphonothien-2-yl)selenoxanthylium dye (3-Se) into TiO2. Dye 3-Se adsorbed to TiO2 via the phosphonic acid group as a mixture of H-aggregates and monomers. Injection of electrons from photoexcited 3-Se into TiO2 yielded the dication radical (3-Se+) and an associated transient absorption at wavelengths shorter than 540 nm, the amplitude of which was proportional to the quantum yield of electron injection (ϕinj). Our data revealed that ϕinj from H-aggregated 3-Se was (2.0 ± 1.3)-fold greater than from monomeric 3-Se; therefore, H-aggregation increased the efficiencies of both light-harvesting and electron injection. Comparison with our reported data for the analogous carboxylic acid-functionalized dye (1-Se) revealed that ϕinj via the carboxylate linkage was (2.3 ± 1.1)-fold greater than via the phosphonate linkage. Thus, electron-injection reactivity is sensitive to both the aggregation state and the surface-anchoring mode of these chalcogenorhodamine dyes. The decrease of ϕinj for 3-Se is offset by its enhanced stability and persistence on TiO2, rendering the phosphonic acid-functionalized and H-aggregated dye a particularly attractive sensitizer.

Keywords
Dye sensitization; Electron injection; Rhodamine; H-aggregation; Phosphonic acid; Transient absorption
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Effects of surface-anchoring mode and aggregation state on electron injection from chalcogenorhodamine dyes to titanium dioxide
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 264, 15 July 2013, Pages 18–25
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