Study of porous materials by scanning probe microscopy
Study of porous materials by scanning probe microscopy
The aim of this research was to assess diffusional ion transport through various porous materials. The study used two novel non-destructive imaging techniques: Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). The SECM was used to probe highly localised fluxes of a specific electroactive species diffusing through the channels of porous materials. The validity and feasibility of the approach were demonstrated with the help of model experiments carried out on a track-etched polycarbonate membrane. This sample was chosen for its low porosity (5%) and its quasi perfect 10μm diameter pores. While diffusion of redox species was induced by a large concentration gradient across the sample, other mass transport mechanisms were eliminated.
The arrival of the redox species, [Fe(CN)6]4-, was detected amperometrically by the SECM tip positioned a few micrometers above the mouth of the pores. Maps (tip current versus planar coordinates,X,Y) were recorded to assess the distribution of diffusional fluxes. Images of localised diffusional fields were obtained and analyzed in terms of single ion fluxes associated with individual pores. More complex experiments were carried out with human dentine samples. Dentine has a very high porosity (75%) with tubules varying from 2 to 5 μm in diameter. It was chosen to challenge the ability of the SECM to image the fluxes of electroactive species diffusing through closely spaced pores and because ion transport through dentinal tubules is thought to be one of the major mechanisms for nerve stimulation in dentine hypersensitivity.
The dentine samples were characterised by AFM and a side study using the same instrument was also carried out to show the efficiency of desensitising toothpaste. The SECM images highlighted the variations in the activity of the pores. Chronoamperograms obtained in the vicinity of the porous substrate provided valuable information on the intricate time dependent diffusional processes occurring in the gap between the sample and the active probe.
University of Southampton
Nugues, Steven
2b5f45b8-d099-4f2d-907d-8c68706c11df
1996
Nugues, Steven
2b5f45b8-d099-4f2d-907d-8c68706c11df
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Nugues, Steven
(1996)
Study of porous materials by scanning probe microscopy.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The aim of this research was to assess diffusional ion transport through various porous materials. The study used two novel non-destructive imaging techniques: Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). The SECM was used to probe highly localised fluxes of a specific electroactive species diffusing through the channels of porous materials. The validity and feasibility of the approach were demonstrated with the help of model experiments carried out on a track-etched polycarbonate membrane. This sample was chosen for its low porosity (5%) and its quasi perfect 10μm diameter pores. While diffusion of redox species was induced by a large concentration gradient across the sample, other mass transport mechanisms were eliminated.
The arrival of the redox species, [Fe(CN)6]4-, was detected amperometrically by the SECM tip positioned a few micrometers above the mouth of the pores. Maps (tip current versus planar coordinates,X,Y) were recorded to assess the distribution of diffusional fluxes. Images of localised diffusional fields were obtained and analyzed in terms of single ion fluxes associated with individual pores. More complex experiments were carried out with human dentine samples. Dentine has a very high porosity (75%) with tubules varying from 2 to 5 μm in diameter. It was chosen to challenge the ability of the SECM to image the fluxes of electroactive species diffusing through closely spaced pores and because ion transport through dentinal tubules is thought to be one of the major mechanisms for nerve stimulation in dentine hypersensitivity.
The dentine samples were characterised by AFM and a side study using the same instrument was also carried out to show the efficiency of desensitising toothpaste. The SECM images highlighted the variations in the activity of the pores. Chronoamperograms obtained in the vicinity of the porous substrate provided valuable information on the intricate time dependent diffusional processes occurring in the gap between the sample and the active probe.
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Published date: 1996
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Local EPrints ID: 459809
URI: http://eprints.soton.ac.uk/id/eprint/459809
PURE UUID: a8279523-db09-44b7-84d7-29686255b598
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Date deposited: 04 Jul 2022 17:19
Last modified: 26 Oct 2024 01:33
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Author:
Steven Nugues
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