TY - JOUR
T1 - Multiple-Exponential Electron Injection in Ru(dcbpy)2(SCN)2 Sensitized ZnO Nanocrystalline Thin Films
AU - Asbury, John B.
AU - Wang, Yong Qiang
AU - Lian, Tianquan
N1 - Funding Information:
This work was supported by a set-up fund from Florida State University to H.C. The authors thank A.B. Thistle (Florida State University) for careful editing of this manuscript and Ji-Young Lee (Boyce Thompson Institute) for the miR165A::GFP and miR166B::GFP lines.
PY - 1999/8/12
Y1 - 1999/8/12
N2 - We have studied the electron injection dynamics of Ru(dcbpy)2(SCN)2 sensitized ZnO nanocrystalline thin films by femtosecond mid-IR absorption spectroscopy. Upon 400 nm excitation of the sensitizer, nonexponential electron injection kinetics from the sensitizer MLCT excited state to ZnO were observed by probing the absorption of injected electrons in the 2000 to 1900 cm-1 region on the <1 ns time scale. A three-exponential fit to the data yields the following rise time constants and amplitudes (in parentheses): < 1ps (18%), 42ps (46%), and 450ps (36%). For films with increasing coverage of sensitizer molecules (optical density at 500 nm of 0.7, 2.3, 2.6), similar electron injection times were observed, while the injection yield decreases. This result suggests that aggregation or multilayer formation of sensitizer molecules reduces the quantum yield of electron injection to ZnO on the <1 ns time scale, and the observed multiexponential injection kinetics are attributed to the distribution of injection rates from the first monolayer of sensitizers. Possible reasons for the nonexponential injection are discussed. The injection dynamics are also compared with the very different injection dynamics observed for the same sensitizer on TiO2.
AB - We have studied the electron injection dynamics of Ru(dcbpy)2(SCN)2 sensitized ZnO nanocrystalline thin films by femtosecond mid-IR absorption spectroscopy. Upon 400 nm excitation of the sensitizer, nonexponential electron injection kinetics from the sensitizer MLCT excited state to ZnO were observed by probing the absorption of injected electrons in the 2000 to 1900 cm-1 region on the <1 ns time scale. A three-exponential fit to the data yields the following rise time constants and amplitudes (in parentheses): < 1ps (18%), 42ps (46%), and 450ps (36%). For films with increasing coverage of sensitizer molecules (optical density at 500 nm of 0.7, 2.3, 2.6), similar electron injection times were observed, while the injection yield decreases. This result suggests that aggregation or multilayer formation of sensitizer molecules reduces the quantum yield of electron injection to ZnO on the <1 ns time scale, and the observed multiexponential injection kinetics are attributed to the distribution of injection rates from the first monolayer of sensitizers. Possible reasons for the nonexponential injection are discussed. The injection dynamics are also compared with the very different injection dynamics observed for the same sensitizer on TiO2.
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U2 - 10.1021/jp991625q
DO - 10.1021/jp991625q
M3 - Article
AN - SCOPUS:0346615702
SN - 1520-6106
VL - 103
SP - 6643
EP - 6647
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 32
ER -