Measurements and Theoretical Modelling of Ultrafast Heterogeneous Spacer-Controlled Electron Transfer

Burfeindt, Bernd; Ramakrishna, S.; Zimmermann, C.; Meissner, Britta; Hannappel, T.; Storck, W.; Willig, F.

doi:10.1007/978-3-642-72289-9_193

Cited by 12 publications

(24 citation statements)

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“…Competition of Electron Injection and Vibrational Relaxation. In addition to the Ru dye-sensitized TiO 2 , ,,,,, ultrafast electron injection on the 100 fs or faster time scale from various sensitizers to TiO 2 has also been reported in recent years. ,,,,, An injection process on the <100 fs time scale is comparable to or faster than the vibrational energy relaxation within the excited states of the molecules. , It implies that injection may occur from vibrationally excited states instead of the minimum in the excited-state manifold as was previously thought. To directly demonstrate the competition between electron injection and excited-state relaxation pathways and its effect on injection dynamics, we have investigated the following systems:…”

Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 79%

“…Martini et al , reported a <200 fs electron injection time for 9-anthracene-sensitized anatase TiO 2 nanoparticles. Burfeindt et al , studied modified perylene-sensitized TiO 2 thin films in an ultrahigh vacuum chamber. A 190 fs electron injection time was first reported 58 and a more recent measurement with improved time resolution yielded a 75 fs electron injection time .…”

Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 99%

“…Burfeindt et al , studied modified perylene-sensitized TiO 2 thin films in an ultrahigh vacuum chamber. A 190 fs electron injection time was first reported 58 and a more recent measurement with improved time resolution yielded a 75 fs electron injection time . An electron injection time of 40 ± 20 fs on an oxazine-sensitized bulk SnS 2 crystal surface has also been inferred from its fluorescence lifetime …”

Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 99%

“…In addition to the Ru dye-sensitized TiO 2 , 48,53,80,81,83,84 ultrafast electron injection on the 100 fs or faster time scale from various sensitizers to TiO 2 has also been reported in recent years. 51,54,58,78,123,124 An injection process on the <100 fs time scale is comparable to or faster than the vibrational energy relaxation within the excited states of the molecules. 73,125 It implies that injection may occur from vibrationally excited states instead of the minimum in the excited-state manifold as was previously thought.…”

Section: Competition Of Electron Injection and Vibrationalmentioning

confidence: 99%

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Ultrafast Electron Transfer Dynamics from Molecular Adsorbates to Semiconductor Nanocrystalline Thin Films

et al. 2001

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Interfacial electron transfer (ET) between semiconductor nanomaterials and molecular adsorbates is an important fundamental process that is relevant to applications of these materials. Using femtosecond midinfrared spectroscopy, we have simultaneously measured the dynamics of injected electrons and adsorbates by directly monitoring the mid-IR absorption of electrons in the semiconductor and the change in adsorbate vibrational spectrum, respectively. We report on a series of studies designed to understand how the interfacial ET dynamics depends on the properties of the adsorbates, semiconductors, and their interaction. In Ru(dcbpy)2(SCN)2 (dcbpy = 2,2‘-bipyridine-4,4‘-dicarboxylate) sensitized TiO2 thin films, 400 nm excitation of the molecule promotes an electron to the metal-to-ligand charge transfer (MLCT) excited state, from which it is injected into TiO2. The injection process was characterized by a fast component, with a time constant of <100 fs, and a slower component that is sensitive to sample condition. Similar ultrafast electron injection times were measured in TiO2 films sensitized by Ru(dcbpy)2(X)2 (X2 = 2CN- and dcbpy). Electron injection in these systems was found to compete with the vibrational energy relaxation process within the excited state of the molecules, leading to an injection yield that depends on the excited-state redox potential of the adsorbate. The injection rate from Ru(dcbpy)2(SCN)2 to different semiconductors was found to obey the trend TiO2 > SnO2 > ZnO, indicating a strong dependence on the nature of the semiconductor. To understand these observations, various factors, such as electronic coupling, density of states, and driving force, that control the interfacial ET rate were examined separately. The effect of electronic coupling on the ET rate was studied in TiO2 sensitized by three adsorbates, Re(L n )(CO)3Cl [L n is a modified dcbpy ligand with n (=0, 1, 3) CH2 units between the bipyridine and carboxylate groups]. We found that the ET rate decreased with increasing number of CH2 units (or decreasing electronic coupling strength). The effect of driving force was investigated in Ru(dcbpy)2X2 (X2 = 2SCN-, 2CN-, and dcbpy) sensitized SnO2 thin films. In this case, we observed that the ET rate increased with the excited-state redox potential of the adsorbates, agreeing qualitatively with the theoretical prediction for a nonadiabatic interfacial ET process.

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Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 79%

Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 99%

Section: Ultrafast Electron Injection Dynamicsmentioning

confidence: 99%

Section: Competition Of Electron Injection and Vibrationalmentioning

confidence: 99%

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Ultrafast Electron Transfer Dynamics from Molecular Adsorbates to Semiconductor Nanocrystalline Thin Films

et al. 2001

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“…For this system heterogeneous ET ͑into the semiconductor͒ which proceeds on a 100 fs time scale has been observed, 35,36 and can be well simulated in models which will be used here, too. [37][38][39] Although we have such a system in mind, the present studies concentrate on the models given in Fig.…”

Section: Introductionmentioning

confidence: 99%