Using nanoplasmonic metasurfaces to construct miniaturised marine ecosystem sensors

Abstract

This thesis investigates the potential for nanoplasmonic sensing technology to improve upon current marine environmental sensors. The significant advantage of this technology lies in its compact size and versatility. To realise the full potential of nanoplasmonic sensors, the possibility of directly measuring as many different essential ocean variables as possible is explored.

Chapter one provides the necessary background information on the topics of marine environmental science and nanoplasmonic technology. The required methods used throughout this thesis are detailed in chapter two.

The nanoplasmonic sensors in chapter three utilise bulk refractive index sensing to evaluate salinity of artificial and real seawater samples with a sensitivity of 126 nm/refractive index unit.

In chapters four and five, with the addition of chemical modifications to the nanoplasmonic sensors, molecular sensing of the major oceanic anions and cations is achieved using a cross reactive sensing technique with an accuracy of 79.4% and 84.2% respectively across a naturally occurring concentration range.

The ability to detect subtle changes in complex artificial seawater solutions is accomplished using different combinations of nanoplasmonic metasurfaces in chapter six. These subsets of nanoplasmonic metasurfaces are able to discriminate and identify complex anion and cation solutions with an accuracy of 93.8% and 95.8% respectively. The entire range of nanoplasmonic metasurfaces used throughout this thesis are then combined to be able to identify artificial climate change extreme seawater solutions. This enabled discrimination between seawater solutions with variations in both anions and cations to an accuracy of 92.6%. This array of nanoplasmonic metasurfaces goes on to identify and discriminate between real seawater samples taken from around St Andrews Bay. Using statistical analysis, the different sensor arrays can predict the complex solution with an accuracy above 85.0%.

Chapter seven elaborates on the development of a portable nanoplasmonic detection system that can readily measure changes in salt concentration within solutions using a microfluidic channel. This paves the way for a new generation of portable and powerful environmental sensors.