Antifouling Coatings Developed from Functionalised Silica Nanoparticles

Biological fouling of surfaces, occurring through the attachment and accumulation of microorganisms, is an extensive problem affecting the marine, biomedical, building, and food processing industries. Commercial coatings that are applied to surfaces to reduce or prevent biological fouling frequently rely on the incorporation of toxic antimicrobial chemicals, where their release from the surface is uncontrolled and can have undesirable secondary effects. New approaches to prevent fouling focus on the development of surfaces or coatings with tailored physicochemical properties which inhibit the interaction and attachment of fouling species. Despite advances in the use of nanomaterials for antifouling applications, many emerging coating technologies are complex, expensive, and unable to be scaled-up for industrial applications. In this thesis, functionalised silica nanoparticles (SiNP) are explored as an emerging platform material for the development of hydrophilic antifouling coatings. SiNPs are common additives to surface coatings as they are cheap, highly processable, and able to be simply functionalised through silane coupling chemistry. In this work, particles were functionalised with zwitterionic and cationic quaternary ammonium chemistries to investigate the effect of chemistry on the nanoparticle coating hydrophilicity and antifouling behaviour. In Chapter 2, two methods of preparing hydrophilic low-fouling surface coatings were explored through reaction of SiNP suspensions and pre-deposited SiNP films with zwitterionic sulfobetaine (SB). SiNP suspensions were functionalised with SB across three pH conditions and deposited as thin films via a simple spin-coating process to generate hydrophilic antifouling coatings. In addition, coatings of predeposited SiNP were surface functionalised via exposure to zwitterionic solutions. Quartz crystal microgravimetry with dissipation monitoring (QCM-D) was employed as a high throughput technique for monitoring and optimising reaction to the SiNP surfaces. Functionalisation of nanoparticle films was rapid and could be achieved over a wide pH range and at low zwitterion concentrations. All functionalised particle surfaces presented a high degree of wettability and resulted in large reductions in adsorption of bovine serum albumin (BSA) protein. Particle coatings also showed a reduction in adhesion of fungal spores (Epicoccum nigrum) and bacteria (Escherichia coli) by up to 87% and 96%, respectively