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Posted: Feb 22, 2012

Single-particle spectroscopy reveals role of surface defects

(Nanowerk News) Photoinduced interfacial electron transfer (ET) from covalently bound molecules or particles to a semiconductor oxide plays a critical role in solar cells, photocatalysis, and molecular electronics. Titania surfaces are a key factor influencing photoinduced charge injection processes from covalently bound chromophores. However, the dependence of ET on TiO2 structure, defects, and facets remains poorly understood because of the multitude of binding sites.
Lund
In an effort to correlate TiO2 surface features with ET, researchers compare the photoinduced ET dynamics from single quantum dots (QDs) to polycrystalline TiO2 thin films (pc-TiO2) grown by atomic layer deposition (ALD) with that of porous TiO2 nanoparticle films (np-TiO2) by utilizing single-particle fluorescence spectroscopy. (© ACS)
To correlate TiO2 surface features with ET, users from Argonne's Materials Science Division and Northwestern University, together with CNM's Nanophotonics Group, compared the photoinduced ET dynamics from single quantum dots (QDs) to polycrystalline TiO2 thin films (pc-TiO2) grown by atomic layer deposition with that of porous TiO2 nanoparticle films (np-TiO2) by using single-particle fluorescence spectroscopy (see paper in The Journal of Physical Chemistry C: "Reduced Heterogeneity of Electron Transfer into Polycrystalline TiO2 Films: Site Specific Kinetics Revealed by Single-Particle Spectroscopy").
Unlike the broad distribution of ET rates on np-TiO2, QDs on pc-TiO2 exhibit two ET rates that are attributed to reduced site heterogeneity.
Combined with annealing studies of pc-TiO2 preparation, this study reveals the role of the surface defects in photoinduced ET processes for the first time.
Source: Argonne National Laboratory
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