Engineering of bacteriochlorophyll pigments and quantum dots for the production of novel photonic materials

Due to their small size, and consequent quantum confinement, quantum dots (QDs) exhibit electronic properties intermediate between those of bulk semiconductors and individual molecules. The electronic and optical properties of these semiconductor nanocrystals are tuneable by nanocrystal size and composition. Consequently, they offer a range of attractive photophysical properties with a wide range of possible applications. Copper indium sulphide (CIS) QDs are attracting increasing attention due to lower toxicity, significant quantum confinement, and a bulk direct band-gap of ~1.5eV making them ideal for solar energy applications. Bacteriochlorophylls (BChls) c/d and e are photosynthetic pigments found in green photosynthetic bacteria. Due to their structure, they are able to self-assemble into densely packed aggregates exhibiting strong excitonic coupling between individual pigments as well as optical spectra substantially different to those of monomeric BChls. The self-aggregating nature of these molecules and the resulting strong coupling results in impressive light harvesting ability and rapid energy transfer, thus providing exciting opportunities for use in nanomaterials. Coupling BChl aggregates with QDs should lead to strong interaction between energy levels and efficient energy transfer, yielding new hybrid nanostructures with novel electronic and optical properties. In this thesis, BChl pigments and QDs are investigated with a focus on how they might be combined to produce novel photonic materials. This thesis outlines a new method for the production of zinc containing BChl analogues as well as presenting the first molecular dynamics simulations on BChl c pigment assemblies investigating the origin of intrinsic curvature. In addition, a new method for the direct synthesis of hydrophilic CIS QD is presented, along with the first quantitative data on size dependent photoluminescent quantum yield for CIS QDs. Furthermore photoluminescent decay studies presented in this thesis shed new light on the role of size and composition on the relative contribution of key recombination pathways within CIS quantum dots.