School of Chemistry - Theses
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ItemSynthesis and self-assembly of core-shell gold nanorod-PNIPAM nanoparticles( 2016)An essential requirement for the use of nanoparticles in self assembly applications is ensuring their colloidal stability is maintained, as well as being able to tailor their properties for enhanced functionality. One way of doing so is through the incorporation of nanoparticles in responsive microgels, leading to the formation of inorganic/organic hybrid nanocomposites. The aim of this research was to develop a generic protocol for the preparation of hybrid core-shell microgels composed of nanoparticle cores and responsive polymer shells. Specifically, core-shell gold nanorod - poly-N-isopropylacrylamide (PNIPAM) particles with high yield and monodispersity were synthesised. Due to the high sensitivity of the longitudi-nal plasmon band to its local environment, the change in refractive index caused by the temperature-induced collapse of the PNIPAM shell led to a red-shift on the order of tens of nanometres in the plasmon band. This shift was reversible for multiple heating/cooling cycles, and no aggregation of the gold nanorod cores was observed. Concentrating the gold nanorod-PNIPAM solutions at high volume fractions enabled them to crystallise, thereby exhibiting strong diffraction peaks. The formed colloidal crystals could be melted upon annealing, and re-formed upon cooling due to the responsive behaviour of the PNIPAM shell. These crystals exhibited fascinating optical behaviour which opens a pathway to a new class of hybrid materials with potential use in a wide array of applications.