Inhomogeneity of electron injection rates in dye-sensitized TiO2: continuous mesoporous films and single particle behavior

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

doi:10.1117/12.681448

30 August 2006 Inhomogeneity of electron injection rates in dye-sensitized TiO₂: continuous mesoporous films and single particle behavior

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

Author Affiliations +

Proceedings Volume 6325, Physical Chemistry of Interfaces and Nanomaterials V; 63250X (2006) https://doi.org/10.1117/12.681448
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

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.

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Toby D. M. Bell, Cynthia Pagba, Mykhaylo Myahkostupov, Johan Hofkens, and Piotr Piotrowiak "Inhomogeneity of electron injection rates in dye-sensitized TiO₂: continuous mesoporous films and single particle behavior", Proc. SPIE 6325, Physical Chemistry of Interfaces and Nanomaterials V, 63250X (30 August 2006); https://doi.org/10.1117/12.681448

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KEYWORDS

Nanoparticles

Molecules

Atmospheric particles

Particles

Confocal microscopy

Luminescence

Picosecond phenomena

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