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Ultrafast Transient Absorption Studies of Hematite Nanoparticles: The Effect of Particle Shape on Exciton Dynamics
Author(s) -
Fitzmorris Bob C.,
Patete Jonathan M.,
Smith Jacqueline,
Mascorro Xiomara,
Adams Staci,
Wong Stanislaus S.,
Zhang Jin Z.
Publication year - 2013
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201300571
Subject(s) - hematite , ultrashort pulse , ultrafast laser spectroscopy , nanoparticle , exciton , chemical physics , particle (ecology) , absorption (acoustics) , materials science , transient (computer programming) , nanotechnology , molecular physics , chemistry , physics , spectroscopy , optics , condensed matter physics , quantum mechanics , laser , oceanography , geology , metallurgy , composite material , computer science , operating system
Much progress has been made in using hematite (α‐Fe 2 O 3 ) as a potentially practical and sustainable material for applications such as solar‐energy conversion and photoelectrochemical (PEC) water splitting; however, recent studies have shown that the performance can be limited by a very short charge‐carrier diffusion length or exciton lifetime. In this study, we performed ultrafast studies on hematite nanoparticles of different shapes to determine the possible influence of particle shape on the exciton dynamics. Nanorice, multifaceted spheroidal nanoparticles, faceted nanocubes, and faceted nanorhombohedra were synthesized and characterized by using SEM and XRD techniques. Their exciton dynamics were investigated by using femtosecond transient absorption (TA) spectroscopy. Although the TA spectral features differ for the four samples studied, their decay profiles are similar, which can be fitted with time constants of 1–3 ps, approximately 25 ps, and a slow nanosecond component extending beyond the experimental time window that was measured (2 ns). The results indicate that the overall exciton lifetime is weakly dependent on the shape of the hematite nanoparticles, even though the overall optical absorption and scattering are influenced by the particle shape. This study suggests that other strategies need to be developed to increase the exciton lifetime or to lengthen the exciton diffusion length in hematite nanostructures.