Vibrational spectroscopy of a silane monolayer at air/solid and liquid/solid interfaces using sum-frequency generation

Guyot‐Sionnest, Philippe; Superfine, R.; Hunt, James B.; Shen, Y. R.

doi:10.1016/0009-2614(88)87079-9

Cited by 186 publications

(121 citation statements)

References 11 publications

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“…Fig. 4 presents a clear example (40). For an octadecyltrichlorosilane (OTS) surfactant monolayer adsorbed at two different liquid/quartz interfaces (buried interfaces), CCl4/OTS/quartz and hexadecane/ OTS/quartz, the spectrum is completely dominated by the OTS monolayer.…”

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confidence: 99%

A few selected applications of surface nonlinear optical spectroscopy.

Shen

1996

Proc. Natl. Acad. Sci. U.S.A.

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As a second-order nonlinear optical process, sum-frequency generation is highly surface-specific and accordingly has been developed into a very powerful and versatile surface spectroscopic tool. It has found many unique applications in different disciplines and thus provided many exciting new research opportunities in surface and surfacerelated science. Selected examples are discussed here to illustrate the power of the technique.In recent years, we have been developing and applying modern optical techniques to surface and interface studies. The one that has attracted much attention is surface optical second harmonic generation (SHG) and sum-frequency generation (SFG) (1). This is because the technique has very high surface specificity and wide applicability. SFG is a nonlinear optical process in which two laser beams at frequencies wi and w2 impinging on a medium mix and generate a sum-frequency output at ws = Wl + W2. SHG is a special case of SFG with wi = w2. It is well known that a second-order nonlinear optical process like SHG and SFG is forbidden in a medium with inversion symmetry (2). At a surface or interface, however, the inversion symmetry is necessarily broken. This then leads to the surface specificity of SHG and SFG. More formally, SFG (or SHG) originates from a nonlinear polarization P(2)(ws) induced in a medium by laser wave mixing (2): p(2)(W) = X(2):E()E(W2) [1] where E(wi) is the laser field at wi and X(2) is a tensor describing the nonlinear response of the medium to the fields. Inversion symmetry of the medium yields72) = _.i2), and therefore x (2) must vanish. The SFG Lor SHG) measurement on a surface allows the deduction of X(2)(Ws = Wl + W2), which is a tensor characteristic of the surface (3). For example, the symmetry of 2) provides information about the surface structural symmetry. The spatial variation of x42) over the surface directly reflects the spatial variation of the surface structure. The time variation of 92) indicates how the surface structure changes with time. Of particular importance is that 2) also carries spectroscopic information that enables us to learn microscopic details about the surface. As shown in Fig. 1

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confidence: 99%

A few selected applications of surface nonlinear optical spectroscopy.

Shen

1996

Proc. Natl. Acad. Sci. U.S.A.

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“…In a time domain representation of a BB-SFG experiment, the fs IR pulse induces an oscillating time dependent first order polarization (1) (1)…”

Section: Theorymentioning

confidence: 99%

“…Some advantages of VSFG are: (1) the richness of the molecular level information; (2) the ability to perform in situ non-destructive measurements; and (3) access to buried interfaces. A standard method for acquiring SFG spectra is to scan a narrow band IR pulse over the vibrational resonance of interest, in the presence of narrow band visible pulse (nanosecond or picosecond) [1][2][3]. Alternatively, broadband sum frequency generation (BB-SFG) makes use of femotosecond (fs) broad bandwidth IR pulses (~200-300 cm −1 FWMH) which are sum-mixed with picosecond (ps) narrow band visible pulses at an interface.…”

Section: Introductionmentioning

confidence: 99%

Vibrational sum frequency generation spectroscopy using inverted visible pulses

et al. 2010

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“…Because of the symmetry requirement for the second order nonlinear processes, the leading dipolar term of the SHG or SFG processes is generally forbidden for the centrosymmetric bulk medium, and thus SHG and SFG become effective probes for the interface between the two centrosymmetric bulk phases. 26 The theoretical foundation and the experimental demonstration of the interfacial selectivity of SHG as well as SFG were pioneered by Shen and his colleagues since the early 1980's, 27,28,29,30,31,32,33,34 extending from the original formulation of the light waves at the boundary of nonlinear media by Bloembergen et al in the early 1960's. 35 With SHG and SFG-VS, equilibrium and dynamic behaviors of the molecular interface or film can be directly measured from the nonlinear electronic or vibrational spectroscopic response of the interfacial molecular moieties.…”

Section: Introductionmentioning

confidence: 99%

Microscopic molecular optics theory of surface second harmonic generation and sum-frequency generation spectroscopy based on the discrete dipole lattice model

Dong¹,

Yuan²,

Liu³

et al. 2008

International Reviews in Physical Chemistry

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Two crucial issues in the interface studies with the interface specific nonlinear spectroscopy are on how to describe the macroscopic dielectric constant of the molecularly thin layer and how to calculate the anisotropic two dimensional microscopic local field effect. In the currently accepted models of the nonlinear optics, the nonlinear radiation was treated as the result of an infinitesimally thin polarization sheet layer, and a three layer model was generally employed. The direct consequence of this approach is that an apriori dielectric constant, which still does not have a clear definition, has to be assigned to this polarization layer. Because the Second Harmonic Generation (SHG) and the Sum-Frequency Generation vibrational Spectroscopy (SFG-VS) have been proven as the sensitive probes for interfaces with the submonolayer coverage, the treatment based on the more realistic discrete induced dipole model needs to be developed. Here we show that following the molecular optics theory approach the SHG, as well as the SFG-VS, radiation from the monolayer or submonolayer at an interface can be rigorously treated as the radiation from an induced dipole lattice at the interface. In this approach, the introduction of the polarization sheet is no longer necessary. Therefore, the ambiguity of the unaccounted dielectric constant of the polarization layer is no longer an issue. Moreover, the anisotropic two dimensional microscopic local field factors can be explicitly expressed with the linear polarizability tensors of the interfacial molecules. Based on the planewise dipole sum rule in the molecular monolayer, crucial experimental tests of this microscopic treatment with SHG and SFG-VS are discussed. Many puzzles in the literature of surface SHG and SFG spectroscopy studies can also be understood or resolved in this framework. This new treatment may provide a solid basis for the quantitative analysis in the surface SHG and SFG studies.

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Vibrational spectroscopy of a silane monolayer at air/solid and liquid/solid interfaces using sum-frequency generation

Cited by 186 publications

References 11 publications

A few selected applications of surface nonlinear optical spectroscopy.

A few selected applications of surface nonlinear optical spectroscopy.

Vibrational sum frequency generation spectroscopy using inverted visible pulses

Microscopic molecular optics theory of surface second harmonic generation and sum-frequency generation spectroscopy based on the discrete dipole lattice model

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