Second harmonic generation of molecules located at the air / water interface
Second harmonic generation of molecules located at the air / water interface
Second Harmonic Generation (SHG) and the related technique of Second Harmonic Ellipsometry (SHE) have been used to study the interfacial properties of several different molecules when located at the air/water interface.
The technique of SHG was used to monitor the air/water interface as the temperature was raised from 20 to 60°C, where a very weak dependence of the measured SHG intensity was found. The observed drop in signal was rationalised in terms of the increasing energy/entropy of the system reducing the influence of the hydrogen-bonding and water dipole-dipole contributions to the surface ordering. The potential for the SHE technique as a sensitive surface probe was demonstrated by the detection of a surface impurity missed in routine surface tension measurements.
The interfacial behaviour of paranitrophenol was investigated at both the air/water and dodecane/water interfaces. The subsequent analysis of the SHG data indicated a difference of surface orientation, where at the dodecane/water interface an 8° shift of the paranitrophenol molecules towards the surface normal occurs. The analysis and the change in the δ parameter observed in the SHE investigation implies a much less ordered arrangement for paranitophenol when located at the air/water interface.
The presence of certain metal cations were shown to affect the interfacial behaviour of three simple crown-ethers to the extent that changes were observed in the SHG polarisation response. Qualitatively, these results and the differences were rationalised in terms of ionic diameter, ring cavity size, ion/crown-ether affinity and an ion-chromophore interaction. The more detailed analysis of the data presented was discussed.
University of Southampton
Timson, Andrew John
282d1751-228e-4c62-a984-01bf4a7d1fce
2000
Timson, Andrew John
282d1751-228e-4c62-a984-01bf4a7d1fce
Timson, Andrew John
(2000)
Second harmonic generation of molecules located at the air / water interface.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Second Harmonic Generation (SHG) and the related technique of Second Harmonic Ellipsometry (SHE) have been used to study the interfacial properties of several different molecules when located at the air/water interface.
The technique of SHG was used to monitor the air/water interface as the temperature was raised from 20 to 60°C, where a very weak dependence of the measured SHG intensity was found. The observed drop in signal was rationalised in terms of the increasing energy/entropy of the system reducing the influence of the hydrogen-bonding and water dipole-dipole contributions to the surface ordering. The potential for the SHE technique as a sensitive surface probe was demonstrated by the detection of a surface impurity missed in routine surface tension measurements.
The interfacial behaviour of paranitrophenol was investigated at both the air/water and dodecane/water interfaces. The subsequent analysis of the SHG data indicated a difference of surface orientation, where at the dodecane/water interface an 8° shift of the paranitrophenol molecules towards the surface normal occurs. The analysis and the change in the δ parameter observed in the SHE investigation implies a much less ordered arrangement for paranitophenol when located at the air/water interface.
The presence of certain metal cations were shown to affect the interfacial behaviour of three simple crown-ethers to the extent that changes were observed in the SHG polarisation response. Qualitatively, these results and the differences were rationalised in terms of ionic diameter, ring cavity size, ion/crown-ether affinity and an ion-chromophore interaction. The more detailed analysis of the data presented was discussed.
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Published date: 2000
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Local EPrints ID: 464193
URI: http://eprints.soton.ac.uk/id/eprint/464193
PURE UUID: 9085ec35-01b9-46bd-a296-731ee26591d1
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Date deposited: 04 Jul 2022 21:31
Last modified: 16 Mar 2024 19:19
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Author:
Andrew John Timson
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