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Title: Dimensionality of nanoscale TiO2 determines the mechanism of photoinduced electron injection from a CdSe nanoparticle

Assumptions about electron transfer (ET) mechanisms guide design of catalytic, photovoltaic, and electronic systems. We demonstrate that the mechanism of ET from a CdSe quantum dot (QD) into nanoscale TiO2 depends on TiO2 dimensionality. The injection into a TiO2 QD is adiabatic due to strong donor–acceptor coupling, arising from unsaturated chemical bonds on the QD surface, and low density of acceptor states. In contrast, the injection into a TiO2 nanobelt (NB) is nonadiabatic, because the state density is high, the donor–acceptor coupling is weak, and multiple phonons accommodate changes in the electronic energy. The CdSe adsorbant breaks symmetry of delocalized TiO2 NB states, relaxing coupling selection rules, and generating more ET channels. Both mechanisms can give efficient ultrafast injection. Furthermore, the dependence on system properties is very different for the two mechanisms, demonstrating that the fundamental principles leading to efficient charge separation depend strongly on the type of nanoscale material.
Authors:
 [1] ;  [2] ;  [3]
  1. National Energy Technology Lab. (NETL), Albany, OR (United States); URS Corp., Albany, OR (United States)
  2. Univ. College Dublin, Dublin (Ireland)
  3. Univ. of Rochester, Rochester, NY (United States)
Publication Date:
OSTI Identifier:
1165415
Report Number(s):
CONTR-PUB--044
Journal ID: ISSN 1530-6984
Grant/Contract Number:
FE0004000
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 14; Journal Issue: 4; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
National Energy Technology Lab. (NETL), Albany, OR (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY nonadiabatic molecular dynamics; time-domain density functional theory; semiconductor quantum dots; electron-vibrational interaction; adiabatic electron transfer