Ramsay, Massimiliano Leo Alan;
(2022)
Nanostructured Diamond for Environmentally Robust Surface Enhanced Raman Spectroscopy Sensors.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Surface enhanced Raman spectroscopy (SERS) is a vibrational spectroscopic technique that combines the specificity of Raman spectroscopy with the high detection sensitivity of surface enhancement effects. These effects typically leverage the electromagnetic near-field enhancement generated by free electron oscillations (plasmons) of gold and silver nanoparticles in response to electromagnetic radiation. However, SERS enhancing surfaces are not known for their physical and chemical durability, as they rely on exposed metallic nanoparticles. The aim of the studies presented herein is to develop environmentally robust SERS substrates, to be able to chemically monitor aqueous environments for prolonged periods of time. Hence, novel approaches are needed in order to extract the high sensitivity of SERS whilst improving their resistance in harsh aquatic environments. To address this, diamond encapsulation of silver and gold nanoparticles was explored as a chemically and physically resilient coating. Plasma etching of the overgrown diamond layers and durability tests were carried out, showing excellent physical resistance of partly encapsulated gold nanoparticles and chemical resistance of fully encapsulated silver nanoparticles after exposure to piranha solution with sustained SERS performance. Simulations were applied to find the optimal arrangement of spherical gold and silver nanoparticles encapsulated in diamond, to improve the plasmonically generated near-field. These were explored for two common Raman excitation wavelengths: 532 nm and 633 nm. Nanoimprint lithography (NIL) was implemented as a rapid and facile methodology to address the fabrication of structures close to the ones simulated. SERS studies of the encapsulated silver nanoparticles showed improvements in Raman signal enhancement over the randomly distributed silver nanoparticles. NIL was also utilised in two additional studies. Firstly, to study the behaviour of annealing gold films of various thickness into diamond nanoholes of varying depths. A trend between the two thickness metrics was found, allowing for size control of the resulting nanoparticles. Secondly, successful encapsulation of a gold nanoparticles in diamond nanopyramids was presented via templated growth. Excellent SERS responses of these structures were registered after exposure to highly etching piranha solution.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Nanostructured Diamond for Environmentally Robust Surface Enhanced Raman Spectroscopy Sensors |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10158007 |
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