Photochemistry and Photo-Induced Ultrafast Dynamics at Metal Surfaces

Matsumoto, Yoshiyasu

doi:10.1246/bcsj.80.842

Cited by 15 publications

(5 citation statements)

References 81 publications

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“…(1b) A photoinduced charge transfer between the substrate and adsorbate, leading to the formation of a negative ion resonance. Such substrate-mediated photochemical reactions, where hot electrons induce a chemical process on metal surfaces such as desorption and dissociation, have been discussed for various systems [29][30][31][32][33][34]. (1c) The formation of a positive ion resonance via a hole transfer from the metal substrate to the adsorbate.…”

Section: Adsorbate-substrate Interactionmentioning

confidence: 99%

Optically and thermally induced molecular switching processes at metal surfaces

Tegeder

2012

J. Phys.: Condens. Matter

123

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Using light to control the switching of functional properties of surface-bound species is an attractive strategy for the development of new technologies with possible applications in molecular electronics and functional surfaces and interfaces. Molecular switches are promising systems for such a route, since they possess the ability to undergo reversible changes between different molecular states and accordingly molecular properties by excitation with light or other external stimuli. In this review, recent experiments on photo- and thermally induced molecular switching processes at noble metal surfaces utilizing two-photon photoemission and surface vibrational spectroscopies are reported. The investigated molecular switches can either undergo a trans-cis isomerization or a ring opening-closure reaction. Two approaches concerning the connection of the switches to the surface are applied: physisorbed switches, i.e. molecules in direct contact with the substrate, and surface-decoupled switches incorporated in self-assembled monolayers. Elementary processes in molecular switches at surfaces, such as excitation mechanisms in photoisomerization and kinetic parameters for thermally driven reactions, which are essential for a microscopic understanding of molecular switching at surfaces, are presented. This in turn is needed for designing an appropriate adsorbate-substrate system with the desired switchable functionality controlled by external stimuli.

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Section: Adsorbate-substrate Interactionmentioning

confidence: 99%

Optically and thermally induced molecular switching processes at metal surfaces

Tegeder

2012

J. Phys.: Condens. Matter

123

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“…The elementary excitation of photochemical processes on metal surfaces have been classified into direct absorption and substrate-mediated indirect mechanisms. − In order to clarify the excitation mechanism behind the photoinduced tautomerization, we investigated the wavelength, power and polarization dependence of its cross section. Figure a shows the fraction of trans and cis molecules ( N trans/cis ) with respect to the total number of molecules ( N total ) as a function of the dosed photon number at 405 nm excitation wavelength.…”

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confidence: 99%

Direct Observation of Photoinduced Tautomerization in Single Molecules at a Metal Surface

et al. 2016

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Molecular switches are of fundamental importance in nature, and light is an important stimulus to selectively drive the switching process. However, the local dynamics of a conformational change in these molecules remain far from being completely understood at the single-molecule level. Here, we report the direct observation of photoinduced tautomerization in single porphycene molecules on a Cu(111) surface by using a combination of low-temperature scanning tunneling microscopy and laser excitation in the near-infrared to ultraviolet regime. It is found that the thermodynamically stable trans configuration of porphycene can be converted to the metastable cis configuration in a unidirectional fashion by photoirradiation. The wavelength dependence of the tautomerization cross section exhibits a steep increase around 2 eV and demonstrates that excitation of the Cu d-band electrons and the resulting hot carriers play a dominant role in the photochemical process. Additionally, a pronounced isotope effect in the cross section (∼100) is observed when the transferred hydrogen atoms are substituted with deuterium, indicating a significant contribution of zero-point energy in the reaction. Combined with the study of inelastic tunneling electron-induced tautomerization with the STM, we propose that tautomerization occurs via excitation of molecular vibrations after photoexcitation. Interestingly, the observed cross section of ∼10(-19) cm(2) in the visible-ultraviolet region is much higher than that of previously studied molecular switches on a metal surface, for example, azobenzene derivatives (10(-23)-10(-22) cm(2)). Furthermore, we examined a local environmental impact on the photoinduced tautomerization by varying molecular density on the surface and find substantial changes in the cross section and quenching of the process due to the intermolecular interaction at high density.

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“…3,4 We proposed the direct excitation mechanism from the highest occupied molecular orbital (HOMO) state to an excited state of methane hybridized with substrate electronic states. [4][5][6] Later, this mechanism was proved to be right with x-ray absorption spectroscopy performed by Nilsson and co-workers; 7 they found new adsorption-induced bands right above the Fermi level that can be accessible from HOMO of methane with a 6-eV photon. Since we studied the photochemistry of methane, the question on the excitation mechanism has been my central concern in surface photochemistry at metal surfaces.…”

Section: Introductionmentioning

confidence: 92%

Toward photochemistry of integrated heterogeneous systems

Matsumoto

2012

The Journal of Chemical Physics

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This paper begins with describing the excitation mechanisms in surface photochemistry and nuclear dynamics of adsorbate induced by electronic excitation. An illustrative example is Cs adsorbate on a Cu(111) surface. This adsorption system shows drastic changes in the electronic structure with coverage; this allows us to examine different types of electronic excitations that stimulate nuclear motions of Cs. Remarks are made on challenges in photoinduced processes at well-defined surfaces: direct observations of adsorbate-substrate vibrational modes and photoinduced reactions between adsorbates. Then, the paper addresses some issues in more complex systems: metal-liquid interfaces and powdered photocatalysts of metal oxides. Photochemistry and photoinduced nuclear dynamics at metal-liquid interfaces have not been well explored. Studies on this subject may make it possible to bridge the gap between surface photochemistry and electrochemistry. Photocatalysis with powdered catalysts has been extensively studied and is still an active area, but our understanding of the mechanism of photocatalysis is far from satisfactory. Although complicated, the highly integrated systems provide an opportunity to extend our knowledge of surface photochemistry.

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Photochemistry and Photo-Induced Ultrafast Dynamics at Metal Surfaces

Cited by 15 publications

References 81 publications

Optically and thermally induced molecular switching processes at metal surfaces

Optically and thermally induced molecular switching processes at metal surfaces

Direct Observation of Photoinduced Tautomerization in Single Molecules at a Metal Surface

Toward photochemistry of integrated heterogeneous systems

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