Surface-enhanced Raman spectroscopy for environmental and biological analysis : a dissertation presented for the Doctor of Philosophy in Nanoscience, Massey University, Manawatu, New Zealand. EMBARGOED until 1 October 2021.

Abstract

In recent years, extended efforts have been made to protect the environment, public and animal health from toxic chemicals that create a threat to the society. Either it is rodenticides affecting the entire forest food chain or toxicity of certain drugs on animals and humans. All such outbreaks require a faster and readily available detection method as a solution. There are numerous techniques for such toxic contaminant detection, but all require specific instrumentation and tedious sample preparation procedures. Due to the growing popularity of Surfaceenhanced Raman spectroscopy (SERS), detection becomes a simpler, easier, faster and inexpensive for multiplex detection of environmental, chemical or biological contaminants. Here, we explored a variety of SERS substrates (e.g., etched silicon, silver dendrites, and silver colloidal nanoparticles) for such detection. Our results demonstrate that colloidal nanoparticles combined with an omniphobic substrate, known as slippery infused porous substrate (SLIPSERS) has the potential for detection of rodenticides and anesthetic drugs in simple and complex biological matrices. This research explores the diversity of this method as well as how it behaves differently in different environments responsible for surface enhancement by substrate characterisation. An initial experiment was performed on Rhodamine 6G as a test analyte using SLIPSERS which give an excellent limit of detection down to picomolar level concentration. Therefore, the method was further applied for the detection of rodenticides – brodifacoum and sodium monofluoroacetate in aqueous solution and milk and lidocaine hydrochloride in aqueous and deer antler velvet. The results indicate that SLIPSERS and SERS are capable of highly sensitive detection, characterisation, and quantification of toxic analytes in the environment that pose a threat to society. Moreover, for the first time, the SLIPSERS method has been used for detection and quantification of such analytes quickly and accurately.