Biomimetic routes to hierarchical-functional nanomaterials

Abstract

It is undeniable that nanosystems are interesting materials, displaying properties that are fascinating and different from their bulk material counterparts. These exciting properties are perhaps one of the main motivations fuelling the quest for nanoscale as the next frontier in material science. Certainly, as science moves forward, it is becoming more apparent that nature that has been designing materials on a nanoscale for eons and that we have a lot that we can learn from its capabilities in more bottom-up preparations. Learning and borrowing from nature has led to the growth of the biomimetic materials fields. Here, the author has attempted to produce novel functional nano materials as photocatalysts and bone graft substitutes by combining biomimicry and nano-scaling. It is hoped that the final hierarchical functional nanomaterials will benefit the society in general. In this thesis, the photocatalytic properties of titania replicas that have been obtained using Eucalyptus camaldulensis and Rotala rotundifolia biotemplates were synthesised and characterised. It was discovered that the biotemplated replicas ended up forming mixed oxide systems, which could degrade MO and TX-100 in water. They were also successful incorporated in a novel asymmetric floating film, which retained its photocatalytic properties in an immobilised format. Bone graft substitutes utilising hydrogel blends were also synthesised to resemble vesicle like membranes, seen during ossification, for the mineralisation of amorphous calcium phosphates (ACP) and crystalline hydroxyapatite (CDHA). The resulting mineralised hydrogel scaffolds showed improved mechanical properties for use in low load bearing areas, as well as being bioactive when tested in SBF. The scaffolds as a whole, showed an ability to take up and release MO, MB and AA, thus highlighting their secondary use as drug delivery devices. Finally, biodegradable PLA microspheres were synthesised and successfully coated with CaP and a titanium phase. They were shown to be able to uptake and release the drug gentamicin afterwards. Taken as a whole, this thesis sheds lights on the use of biomimicry to create templates capable of forming functional materials like TiO2 and CDHA, as well as the factors that need to be considered to ensure that the necessary properties are achieved and preserved.