The Optimisation of Silicas: Pre-treatment, Grafting & Potential Devices

Abstract

Silica materials especially mesoporous silicas are prime candidates as materials which could help solve many issues currently existing such as rising CO2 levels as capture devices and rising levels of cancer worldwide as therapeutics. Interest in these materials are always rising due to the large amount of applications which these materials hold a good portion of the research. From adsorption processes in waste streams and exhaust systems to supports of enzymes and catalysts, silicas offer large benefits to these areas of study. In chapter 1, the main motivations as to why the research presented during this PhD was carried out are discussed. The chapter explains the current challenges facing the various sectors, based on the application associated with that particular area. It lays out the fundamentals associated with mesoporous silicas which include synthesis, grafting and characterisation of resulting products. In chapter 2 the synthetic methods to produce silica throughout the results chapters are outline and discussed. The methods of characterisation including the techniques used are also described along with their governing principals. In chapter 3 the role of cleaning methods is examined in terms of their effect on mesoporous silicas. The cleaning of silica surfaces is a critical step in the semiconductor industry and is carried out before functionalisation to prime the surface for attachment with whatever ligand or agent is being attached. The chapter examines this effect in mesoporous silicas and looks to determine if it has any effect on latter grafting quantities. In chapter 4 the functionalisation of mesoporous silicas SBA-15 and MCM-41 with polymers is examined. Hydroxyl-terminated poly-2-vinyl pyridine is used and the optimal conditions for grafting are determined. Using SBA-15 grafted poly-2-vinyl pyridine, metal salts can be infiltrated into the polymer layer and were examined with potential applications such as heavy metal adsorption from waste streams and as a catalyst in mind. Chapter 5 explores the incorporation of antimicrobial essential oils (EO) into mesoporous silica, SBA- 15 for potential application food packaging. The development of a simple method to load antimicrobial EO within a support material chemically bound to a substrate was explored. Mesoporous silica (SBA- 15) was functionalised via a post-synthetic reaction using (3-aminopropyl) triethoxysilane (APTES) and then grafted to a 3-glycidyloxypropyltrimethoxysilane (GPTS) modified surface. The smart delivery device was assessed against common food spoilage microorganisms. In chapter 6 final conclusions are wrapped up and potentially new lines of enquiries which could be examined are outlined in future works.