Inhomogeneity of electron injection rates in dye-sensitized TiO 2: Continuous mesoporous films and single particle behavior

Toby D.M. Bell, Cynthia Pagba, Mykhaylo Myahkostupov, Johan Hofkens, Piotr Piotrowiak

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

Abstract

Pump-probe experiments show that electron injection from a dye into mesoporous TiO2 is as fast as 1×1013 s-1. However, the same materials exhibit residual dye emission with lifetimes in the long nanosecond range. This inhomogeneity of e- injection rates was addressed in fluorescence lifetime microscopy experiments. The residual emission of continuous films of TiO2 was compared with that of individual anatase nanoparticles that had undergone extensive dialysis. The films produce intense emission with multiexponential decay. The mesoporous film contains physisorbed and trapped dye, which is the dominant source of the emission. The distribution of emission lifetimes may reflect the mean free paths experienced by the dye molecules diffusing within the porous TiO2. The intensity of emission from individual nanoparticles from which the loose dye was removed is orders of magnitude lower. The lifetimes are much shorter, with the primary components on subnanosecond time scale. The presence of residual emission with a ∼200 ps lifetime shows that even on dialyzed nanoparticles a fraction of dye does not inject electrons with the same rate as observed in ultrafast pump-probe experiments. It is likely that the residual emission originates from the dye bound to defects.

Original languageEnglish
Title of host publicationPhysical Chemistry of Interfaces and Nanomaterials V
DOIs
Publication statusPublished - 23 Nov 2006
Externally publishedYes
EventPhysical Chemistry of Interfaces and Nanomaterials V - San Diego, CA, United States of America
Duration: 15 Aug 200617 Aug 2006

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume6325
ISSN (Print)0277-786X

Conference

ConferencePhysical Chemistry of Interfaces and Nanomaterials V
CountryUnited States of America
CitySan Diego, CA
Period15/08/0617/08/06

Keywords

  • Anatase
  • Confocal microscopy
  • Electron injection
  • Ru(bpy)(dcbpy)
  • TCSPC

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