Ultrafast Nonlinear Optical Studies of Surface Reaction Dynamics: Mapping the Electron Trajectory

Lanzafame, Joseph; Palese, Stephen P.; Wang, D.; Miller, R. J. Dwayne; Muenter, Annabel A.

doi:10.1021/j100094a008

Cited by 90 publications

(114 citation statements)

References 18 publications

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“…However experimental studies on these time scales have been very limited. 6 Of all potential sensitising dyes for photoelectrochemical solar cells, ruthenium(II) trisbipyridyl (Ru(bpy) 3 2+ ) complexes and their analogues have received the most attention. 5,9 The optimum energy conversion reported to date for a photoelectrochemical solar cell has been obtained using the sensitizer dye Ru II (2,2′-bipyridyl-4,4′-dicarboxylate) 2 (NCS) 2 , (Ru II (dcbpy) 2 -(NCS) 2 , 1).…”

Section: Introductionmentioning

confidence: 99%

Subpicosecond Interfacial Charge Separation in Dye-Sensitized Nanocrystalline Titanium Dioxide Films

et al. 1996

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We have employed subpicosecond transient absorption spectroscopy to study the rate of electron injection following optical excitation of the ruthenium dye Ru II (2,2′-bipyridyl-4,4′-dicarboxylate) 2 (NCS) 2 (1) adsorbed onto the surface of nanocrystalline titanium dioxide (TiO 2 ) films. This sensitizer dye is of particular interest as it is the most efficient sensitizer dye reported to date and is receiving considerable attention for applications in photoelectrochemical solar energy conversion. Transient data collected for 1 adsorbed onto TiO 2 films were compared with those obtained for control dye-coated ZrO 2 films, as the high conduction band edge of ZrO 2 prevents electron injection. Adsorption of the dye onto the TiO 2 film was found to result in a rapid (<500 ps) quenching of the dye excited-state luminescence. Absorption difference spectra collected for the two dye-coated films were assigned by comparison with the spectroscopy of the dye excited and cation states in solution. These transient absorption data indicated that electron injection in these films occurs in e10 -12 s. Detailed analysis indicates the injection is at least biphasic, with ∼50% occurring in <150 fs (instrument response limited) and 50% in 1.2 ( 0.2 ps. These ultrafast electron injection kinetics are contrasted with the charge recombination reaction, which occurs on the microsecond-millisecond time scales. The ultrafast rate of electron injection observed here is critical both for the high energy conversion efficiencies obtained with this sensitizer dye, and for the excellent long-term stability of this dye in photoelectrochemical solar cells.

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Section: Introductionmentioning

confidence: 99%

Subpicosecond Interfacial Charge Separation in Dye-Sensitized Nanocrystalline Titanium Dioxide Films

et al. 1996

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“…Since the surface-to-volume ratio is inversely proportional to the radius of the particle, nano-particles have exceedingly large surface area relative to bulk (typically a million-fold increase). This large surface area is desirable for almost all applications that are conducted on the surface or interface of metals and semiconductors, e.g., photocatalysis and photoelectrochemistry [3,[5][6][7][8][9]. Furthermore, because the size is usually much smaller than the wavelength of light, these particles can be conveniently studied using transmission optical techniques.…”

Section: Introductionmentioning

confidence: 99%

Preparation and ultrafast optical characterization of metal and semiconductor colloidal nano-particles

Smith

Waters

Faulhaber

et al. 1997

J Sol-Gel Sci Technol

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Abstract. The ultrafast dynamics of photoinduced electrons in several metal and semiconductor colloidal nanoparticle systems are characterized using femtosecond laser spectroscopy. Various preparation methods are used and, in several cases, modified for making particles with long-term stability and narrow and controllable size distributions. The particle size and size distribution are determined using transmission electron microscopy and electronic absorption spectroscopy. For aqueous gold and silver colloids, spatial size confinement is found to cause substantially slower electronic relaxation due to reduction of non-equilibrium electron transport and weaker electron-phonon coupling. In gold colloids, photoejection of electrons into the liquid is observed, which is attributed to a two-photon enhanced ionization process. The effect of surfactant on the electron dynamics in CdS colloids is examined and found to be significant, substantiating the notion that electrons are dominantly trapped at the liquid-solid interface. In Ru3+-doped TiO2 colloids, the electronic decay is found to be as fast as or even faster than in undoped TiO2 and other semiconductor colloids such as CdS, suggesting that ion doping of large bandgap semiconductor colloids is not necessarily effective in lengthening the election lifetime. In almost all cases studied, the majority of the photoinduced electrons are found to decay within a few tens of picoseconds due to non-radiative relaxation. The results are discussed in the context of the potential applications of metal and semiconductor nano-particles in areas including photocatalysis and photoelectrochemistry.

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“…For a large number of accessible acceptor levels, the summation over all terms of this nuclear factor may be reduced to a pure density of final electronic states. [27] In the non-adiabatic case, where the electronic coupling of the donor and acceptor is not very large (typically |H| <150 cm -1 ≅ 0.7 k B T), FCWD becomes a constant, which implies that the rate of the charge injection process is solely controlled by the electronic factor |H| 2 .…”

Section: Ultrafast Charge Injection: Beyond Current Theories Of Etmentioning

confidence: 99%

Dynamics and Mechanisms of Interfacial Photoinduced Electron Transfer Processes of Third Generation Photovoltaics and Photocatalysis

Bauer¹,

Teuscher²,

Brauer³

et al. 2011

Chimia

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Photoinduced electron transfer (PET) across molecular/bulk interfaces has gained attention only recently and is still poorly understood. These interfaces offer an excellent case study, pertinent to a variety of photovoltaic systems, photo-and electrochemistry, molecular electronics, analytical detection, photography, and quantum confinement devices. They play in particular a key role in the emerging fields of third-generation photovoltaic energy converters and artificial photosynthetic systems aimed at the production of solar fuels, creating a need for a better understanding and theoretical treatment of the dynamics and mechanisms of interfacial PET processes. We aim to achieve a fundamental understanding of these phenomena by designing experiments that can be used to test and alter modern theory and computational modeling. One example illustrating recent investigations into the details of the ultrafast processes that form the basis for photoinduced charge separation at a molecular/bulk interface relevant to dye-sensitized solar cells is briefly presented here: Kinetics of interfacial PET and charge recombination processes were measured by fs and ns transient spectroscopy in a heterogeneous donor-bridge-acceptor (D-B-A) system, where D is a Ru II (terpyridyl-PO 3 )(NCS) 3 complex, B an oligo-p-phenylene bridge, and A nanocrystalline TiO 2 . The forward ET reaction was found to be faster than vibrational relaxation of the vibronic excited state of the donor. Instead, the back ET occurred on the μs time scale and involved fully thermalized species. The D-A distance dependence of the electron transfer rate was studied by varying the number of p-phenylene units contained in the bridge moiety. The remarkably low damping factor β = 0.16 Å -1 observed for the ultrafast charge injection from the dye excited state into the conduction band of TiO 2 is attributed to the coupling of electron tunneling with nonequilibrium vibrations redistributed on the bridge, giving rise to polaronic transport of charges from the donor ligand to the acceptor solid oxide surface.

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Ultrafast Nonlinear Optical Studies of Surface Reaction Dynamics: Mapping the Electron Trajectory

Cited by 90 publications

References 18 publications

Subpicosecond Interfacial Charge Separation in Dye-Sensitized Nanocrystalline Titanium Dioxide Films

Subpicosecond Interfacial Charge Separation in Dye-Sensitized Nanocrystalline Titanium Dioxide Films

Preparation and ultrafast optical characterization of metal and semiconductor colloidal nano-particles

Dynamics and Mechanisms of Interfacial Photoinduced Electron Transfer Processes of Third Generation Photovoltaics and Photocatalysis

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