(142a) Graph Theoretic Characterisation of Chirality in Complex Nanodendrimers

Organic, polymeric, and inorganic materials with branching segments radially diverging from the central core are known for unique biological, biomedical, rheological, and other properties. They are referred to as dendrites, dendrimers, arborols, and fractal particles with majority of them displaying stochastically bifurcating structures. There is no established pathway to relate their complex structure combining both order and disorder to measurable macroscale properties. Here, we investigate nanostructured dendrimer-like gold particles with various branching generations Unlike previous nanostructure assemblies with star-, flower-, urchin- and hedgehog-like morphologies, the nanodendritic particles in this study are flat with spikes predominantly confined to one plane. Additionally, they are chiral with multiscale mirror asymmetry determined by L/D-enantiomers of cysteine used during synthesis. Their branching segments can have preferentially left- or right-handed twist leading to polarization rotation. The complex structure of the particles can be quantified using graph theory (GT) which is capable of accurately describing the combined order and disorder in their architecture. Here, we show how classical GT parameters are augmented with geometry to describe this complex structure. Furthermore, we show how electrodynamic simulations may be used to inform the definition of a new parameter, the spike branch factor (SBF) that accurately captures the effect of structure on the optical asymmetry factor (i.e. g-factor). We expect that these parameters will provide a pathway for property-centric design of the complex particles.