The study of polymeric and solid-state luminescent materials

This thesis explores the synthesis and photophysical evaluation of inorganic and organic luminescent materials in the form of doped zinc sulfides and doped-ring-opened copolymerisation polymers. In chapter 1, doped zinc sulfide phosphors are prepared using a high temperature (800 ˚C) solid state synthetic procedure under non-oxidising conditions. Copper doped zinc sulfides, within the literature, have been claimed to emit light over a wide range of wavelengths, including 450, 520, and 600 nm. Previously these transitions have been assigned to zinc vacancies, interstitial zinc, relaxation from a shallow trap state to copper, relaxation from the conductance band to copper t2 states, and relaxation to interstitial copper defects. In this work, four emission peaks are observed: 454, 490, 520, and 600 nm, and assigned to zinc vacancies, sulfur vacancies, interstitial zinc, and interstitial zinc defects, respectively. The assignments were also supported with quasiparticle G0W0 calculations that showed reasonable agreement with the experimental data, with the exception of the interstitial sulfur defect. Doping with Group 2 metals was also explored. Barium and strontium were observed to form both zinc defects and sulfur vacancies, respectively. Calcium was found to not favour the formation of any defect. With the addition of a manganese co-dopant, only barium caused a substantial red shift of the emission to 620 nm, with strontium and calcium causing no alteration to the manganese emission. Chapter 2 focuses on the preparation of small organic luminophores, 1,8-naphthalimides and 1-aminoanthraquinone, suitable for incorporation into a polymer through either post-polymerisation modification using an amine, or through direct incorporation during the polymerisation procedure using a terminal epoxide group. In chapter 3, these small luminophores are used for the synthesis of luminescent polymers with varying concentrations of luminophores. Three small scale polymers are prepared, using 5 and 10 mol% anthraquinone dopant (by epoxide), and 100% naphthalimide as a monomer. Anthraquinone doped polymers displayed molecular weights significantly higher than predicted, while the naphthalimide based polymer exhibited a lower than expected molecular weight. Additionally, large scale (300 g) polymerisation was performed using dopant level quantities of a luminophore to prepare blue, green, and yellow emitting polymers, with colour-fast properties