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Non-linear spectroscopic studies at interfaces : experiment and theory

Non-linear spectroscopic studies at interfaces : experiment and theory
Non-linear spectroscopic studies at interfaces : experiment and theory

The structure and properties of the neat air/toluene interface were studied with SHG using a fundamental wavelength of 532 nm.  The second harmonic wavelength (266 nm) was resonantly enhanced with the first electronic transition and a polarisation dependence study showed the toluene molecule to be oriented by 36° to the surface normal.  Extensive theoretical calculations were carried out using Hartree-Fock (HF), Møller-Plesset (MP2) and Density Functional theory (DFT) methods on the geometries, harmonic frequencies, excitation energies and frequency dependent (hyper) polarisabilities on the toluene molecule.

The non-linear optical properties of the aromatic amino acid L-phenylalanine (Phe) were investigated at the air/water interface.  Polarisation and concentration dependence studies were performed on the air/phenylalanine(aq) interface for concentrations up to 0.8 M.  The phenylalanine molecules were found to complete a monolayer for concentrations above 0.2 M and the adsorption could be described by a Langmuir isotherm.  The orientation of the molecule at the interface didn’t change significantly with increasing bulk concentration and the molecule could be approximated to being weakly aligned at the interface.  The surfactant C20-Phe was studied as a Langmuir-Blodgett (LB) film at the air/water interface.  The orientation of the Phe chromophore was studied by SHG from the gas phase of the film monolayer and it was found to be shifted 6° away from the surface normal with respect to the orientation of the free Phe molecule at the air/water interface.  A frequency dependent calculation on the hyperpolarisability of the Phe molecule with different Phe conformations revealed the sensitivity of the hyperpolarisability values on the conformation of the molecule.

University of Southampton
Danos, Lefteris
c8d070de-d46a-4daa-95cb-5f37b8dbfb50
Danos, Lefteris
c8d070de-d46a-4daa-95cb-5f37b8dbfb50

Danos, Lefteris (2003) Non-linear spectroscopic studies at interfaces : experiment and theory. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The structure and properties of the neat air/toluene interface were studied with SHG using a fundamental wavelength of 532 nm.  The second harmonic wavelength (266 nm) was resonantly enhanced with the first electronic transition and a polarisation dependence study showed the toluene molecule to be oriented by 36° to the surface normal.  Extensive theoretical calculations were carried out using Hartree-Fock (HF), Møller-Plesset (MP2) and Density Functional theory (DFT) methods on the geometries, harmonic frequencies, excitation energies and frequency dependent (hyper) polarisabilities on the toluene molecule.

The non-linear optical properties of the aromatic amino acid L-phenylalanine (Phe) were investigated at the air/water interface.  Polarisation and concentration dependence studies were performed on the air/phenylalanine(aq) interface for concentrations up to 0.8 M.  The phenylalanine molecules were found to complete a monolayer for concentrations above 0.2 M and the adsorption could be described by a Langmuir isotherm.  The orientation of the molecule at the interface didn’t change significantly with increasing bulk concentration and the molecule could be approximated to being weakly aligned at the interface.  The surfactant C20-Phe was studied as a Langmuir-Blodgett (LB) film at the air/water interface.  The orientation of the Phe chromophore was studied by SHG from the gas phase of the film monolayer and it was found to be shifted 6° away from the surface normal with respect to the orientation of the free Phe molecule at the air/water interface.  A frequency dependent calculation on the hyperpolarisability of the Phe molecule with different Phe conformations revealed the sensitivity of the hyperpolarisability values on the conformation of the molecule.

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Published date: 2003

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Local EPrints ID: 465165
URI: http://eprints.soton.ac.uk/id/eprint/465165
PURE UUID: 86e8c13f-f52b-47a0-99ed-b49a446c3e6b

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Date deposited: 05 Jul 2022 00:26
Last modified: 05 Jul 2022 04:24

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Author: Lefteris Danos

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