The Development and Application Of Various Novel SERS Substrates, Based on the Ordered Assemblies of (Closely Packed) Gold Nanoparticles, For Reliable Detection of Nanoplastics In Water

Abstract

Micro- and nanoplastics have a harmful impact on human health with potential to damage organs. The harmful effects of the latter (i.e. nanoplastics) on human health are of particular concern because nanoplastics are smaller in size than microplastics, which makes the nanoplastics greater in surface area to volume. Consequently, nanoplastics have greater capacity to absorb persistent organic pollutants, ions, pathogens and other harmful contaminants present in the environment. The smaller size of nanoplastics also makes nanoplastic penetration through cell wall and tissue possible, therefore, nanoplastics pose more of a threat to human health as compared to microplastics. In order to get better knowledge about the occurrence, transport and toxicological impact of nanoplastics, there is a need to be able to reliably and accurately detect these tiny particles. Whilst in the near past an increase in the research on development of analytical techniques for detection of nanoplastics has been noticed, but in comparison to microplastics detection, there is a dearth in the analytical tools that can achieve reproducible and cost-effective detection of nanoplastics, with the existing technologies in a pre-mature phase of development. Of the existing analytical techniques, Surface-Enhanced Raman Scattering (SERS) has demonstrated great potential in the field, albeit there is still a lot of research required for developing SERS substrates suitable for nanoplastic detection. To this end, the work presented in the thesis was carried out to develop low-cost SERS substrate based on gold nanoparticles, for the reliable detection of low concentrations of nanoplastics in water. Three different methodologies were devised and tested to form ordered assemblies of closely packed gold nanoparticles to be used as SERS substrates detecting low concentrations (of at least 1 μg/mL) of 50 nm and 100 nm pristine polystyrene nanoplastics in dH2O. The reliability of the methodologies and subsequently the homogeneity of the prepared substrates was checked using the parameter coefficient of variation (CV%). The obtained CV% values lower than 15% proved the reliability of the substrates. Furthermore, the practicality of the developed substrates for detection of real world nanoplastics was demonstrated by detecting nanoplastics released from hot insulated cup and food preparation gloves. The methodologies and SERS substrates presented in this thesis overcome the state of the art, therefore contributing to the field of nanoplastic detection through the use of SERS.