Gold and copper metamaterials for plasmonic photocatalysis and sensing

Abstract

The integration of plasmonic effects into metamaterial architectures, comprised of plasmonic elements separated by sub-wavelength distances, has presented exciting opportunities for developing new metamaterials with desired optical properties using different geometries of the constituent elements. These degrees of freedom mean plasmonic metamaterials are suitable for applications in nanophotonics, optoelectronic devices, sensing, photovoltaics and photocatalysis. The recent drive toward harnessing the hot-carriers created upon plasmonic decay in nanostructures has driven a re-evaluation of metamaterial design principles. Increasing the optical absorption and tailoring the nanoscale feature sizes can both be utilised to improve the efficiency of photocatalytic processes, particularly in combination with suitable functional plasmonic metals or via the hybridisation with metal oxides to drive the photo-electrochemical reactions.
In this thesis, the development of two plasmonic metamaterials, based on sub-wavelength arrays of gold nanotubes and copper nanorods will be presented. This scalable, facile and inexpensive fabrication technique is based on anodised alu-minium oxide templates. The subsequent structural and optical characterisation, alongside numerical simulations, demonstrate the ability to control the geometrical parameters of the materials with nanometric precision and illustrate the resultant spectrally tunable plasmonic behaviour and their sensitivity to surrounding media.
The novel fabrication method developed for gold nanotube arrays and the subsequent development of a novel core-shell gold-nickel oxide metamaterial, is broadly applicable to other material constituents that can be electrochemically deposited. This metamaterial is explored as an optical sensor for the detection of acetone at room temperature. The applicability of copper nanorod metamaterials as photocathodes for the electroreduction of carbon dioxide has been investigated and a plasmonic enhanced photocurrent has been observed. Broadband control of the optical properties of these metamaterials has also been demonstrated by cre-ating a core-shell architecture, by precise electrochemical growth of nanometric copper-oxide layers, a process monitored in real-time using in-situ visible light spectroscopy.

Date of Award	1 Jul 2021
Original language	English
Awarding Institution	King's College London
Supervisor	Wayne Dickson (Supervisor)