Electron–phonon couplings at C60 interfaces: a case study by two-color, infrared–visible sum–frequency generation spectroscopy

Caudano, Yves; Silien, Christophe; Humbert, Christophe; Dreesen, Laurent; Mani, A. A.; Péremans, A.; Thiry, P.A.

doi:10.1016/s0368-2048(03)00062-8

Cited by 30 publications

(42 citation statements)

References 31 publications

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“…A strong SFG intensity is only detected when the infrared ($1460 cm À1 ) and SFG wavelengths ($494 nm) matches both the interface A g (2) pentagonal pinch mode and the specific HOMO (highest occupied MO)-LUMO (lowest unoccupied MO) electronic transition, respectively [16]. Indeed, at 494 nm SFG wavelength, the energy of the SFG photons is about 2.5 eV.…”

Section: Influence Of the Adsorbate Electronic Structure: Tpd/ptmentioning

confidence: 97%

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Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Humbert

CAUDANO

Dreesen

et al. 2004

Applied Surface Science

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Two-colour sum-frequency generation (two-colour SFG) spectroscopy was used to probe both vibrational and electronic properties of 1-dodecanethiol/Ag(1 1 1), Au(1 1 1), and Pt(1 1 1), of 5-[p-(6-mercaptohexoxy)-phenyl]-10,15,20-triphenylporphin/Pt(1 1 1), and of C 60 /Ag(1 1 1). The role of the various physical parameters determining the sum-frequency generation (SFG) intensity equation is highlighted. The enhancement of the non-linear second order susceptibility in the aforementioned interfaces is explained in terms of metal interband transition, molecular electronic transition and of electron-phonon coupling, respectively.

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Section: Influence Of the Adsorbate Electronic Structure: Tpd/ptmentioning

confidence: 97%

“…Here, the non-resonant contribution of Ag (1 1 1), w ð2Þ NR , and the electronic resonant contribution of the adsorbate, w ð2Þ e , are unable to explain the enhancement at 532 nm visible wavelength. For C 60 /Ag (1 1 1), w ð2Þ S reads [13,16]:…”

Section: Influence Of the Adsorbate Electronic Structure: Tpd/ptmentioning

confidence: 99%

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Humbert

CAUDANO

Dreesen

et al. 2004

Applied Surface Science

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“…4 Results and discussion 4.1 DR-SFG of undoped C 60 /Ag(111) Preliminary two-colour SFG measurements on C 60 performed in ambient air have shown the occurrence of the DR-SFG phenomenon at the C 60 /Ag(111) interface [11]. However, the ambient conditions are detrimental to the monolayer stability [11,22] and the origin of the observed resonance remained uncertain.…”

Section: Dr-sfg Set-upmentioning

confidence: 99%

“…The Ag(111) substrate and UHV environment were chosen for these studies because many applications of these materials depend strongly on the fullerene charge, which can be modified by alkali metal intercalation doping and by adsorption on a metallic substrate [1,[5][6][7][8][9]. The C 60 molecule is an excellent model system for studying electron-phonon couplings at interfaces [10,11].…”

mentioning

confidence: 99%

In situ nonlinear optical spectroscopy of electron–phonon couplings at alkali‐doped C₆₀/Ag(111) interfaces

Kakudji¹,

Silien²,

Lis³

et al. 2010

Physica Status Solidi (b)

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We use doubly resonant, infrared-visible sum-frequency generation spectroscopy (DR-SFG) to probe vibrational and electronic properties of C 60 and K-doped C 60 monolayers adsorbed on Ag(111) single crystal under ultra-high vacuum (UHV). We recorded the interface SFG spectra for five visible wavelengths. We observe a strong dependence of the SFG intensity of the totally symmetric A g (2) mode of the fullerene while scanning the visible wavelength, due to the DR-SFG phenomenon. The SFG intensity of the A g (2) mode is the strongest at 488 nm and at 532 nm for the pure and fully doped monolayers, respectively. These results demonstrate the occurrence of electron-phonon couplings at the C 60 /Ag(111) and saturated K/C 60 /Ag(111) interfaces. They enable us to determine the energy of the coupled electronic transition and to link the electronic resonance to the h u (HOMO) to t 1g (LUMO þ 1) transition of C 60 .

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“…It has been applied to probe charge transfer, [23] to characterise biomaterial surface electronic properties, [24] and to describe the occurrence of interfacial vibronic coupling phenomena. [21,25] STM imaging is widely used for characterising organic monolayer/noble metal substrate systems in UHV or at liquid/ solid interfaces. However, under ambient conditions, STM poses problems for characterising organic monolayers on transition metals such as platinum, mainly due to thermal drift.…”

mentioning

confidence: 99%

On the Protoporphyrin Monolayers Conformation

et al. 2006

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Porphyrins are intensively studied due to their involvement in haemoglobin constitution for protoporphyrins IX (PPIX) and their derivatives, and due to the technological applications of ferrocene and thiol-linked porphyrins for photovoltaic systems. [1][2][3] For instance, PPIX (Figure 1 a) are used as photosensitizers to eliminate cancerous cells in photodynamic therapy (PDT). [4] However, when a zinc metal ion (Zn II PPIX) is present as shown in Figure 1 b, processes such as oxygenase are inhibited and consequently this metalloporphyrin cannot be used as photosensitizer. Such interesting features are related to their remarkable electronic activity, located in the optically visible or ultraviolet energy ranges, arising from the p-conjugated aromatic groups constituting their moiety. Indeed, in solution, their main electronic characteristics are an intense B-band ( % 400 nm), called the Soret band, and a weaker Q-band ( % 500-600 nm) in the visible energy range. Thin films could exhibit sharp differences depending on their molecular conformation on the substrate, highlighting specific electronic coupling between the porphyrin moieties. Numerous studies have been applied to solutions or aggregates [5][6][7] by using Raman spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) techniques. [8,9] The effect of metal intercalation under electrochemical conditions also constitutes a major research topic. [10,11] Herein, STM and two-colour sum-frequency generation (2C-SFG) spectroscopy measurements are performed ex situ at ambient air on these two parent protoporphyrin self-assembled monolayers (SAMs) in order to characterise their molecular conformation and electronic properties on a Pt(111) substrate.The use of infrared-visible vibrational SFG spectroscopy, [12] a nonlinear optical technique, extends in many research laboratories around the world to applications ranging from engineering to biology. This tool is well-suited for studying organic/ metal interfaces, [13,14] polymers in a pre-defined environment, [15] even in aqueous systems, [16,17] and for measuring sensitive biological compound characteristics such as wettability [18] or biocompatibility, [19] and biomolecular recognition. [20] However, these studies are limited to highlight vibrational modes, neglecting the electronic activity of the interfaces. A few studies using two tunable infrared and visible laser wavelengths [21,22] show the emergence of a new nonlinear optical tool called 2C-SFG. It has been applied to probe charge transfer, [23] to characterise biomaterial surface electronic properties, [24] and to describe the occurrence of interfacial vibronic coupling phenomena. [21,25] STM imaging is widely used for characterising organic monolayer/noble metal substrate systems in UHV or at liquid/ solid interfaces. However, under ambient conditions, STM poses problems for characterising organic monolayers on transition metals such as platinum, mainly due to thermal drift. Nevertheless, over the past years, some...

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Electron–phonon couplings at C60 interfaces: a case study by two-color, infrared–visible sum–frequency generation spectroscopy

Cited by 30 publications

References 31 publications

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

In situ nonlinear optical spectroscopy of electron–phonon couplings at alkali‐doped C₆₀/Ag(111) interfaces

On the Protoporphyrin Monolayers Conformation

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Electron–phonon couplings at C60 interfaces: a case study by two-color, infrared–visible sum–frequency generation spectroscopy

Cited by 30 publications

References 31 publications

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

Self-assembled organic and fullerene monolayers characterisation by two-colour SFG spectroscopy: a pathway to meet doubly resonant SFG process

In situ nonlinear optical spectroscopy of electron–phonon couplings at alkali‐doped C60/Ag(111) interfaces

On the Protoporphyrin Monolayers Conformation

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In situ nonlinear optical spectroscopy of electron–phonon couplings at alkali‐doped C₆₀/Ag(111) interfaces