| The stabilization against moisture and abrasion of Luminova was examined as a function of surface modification by the deposition of a hydrophobic polymer (PDVB), metal oxide (silica and titania), and a polymer-metal oxide combined matrix. The polymer coating was applied by in situ polymerization and was used to obtain a physically adsorbed, uniform, and continuous surface coverage. The thickness, or weight percent, of the polymer was controlled by adjusting the solids : monomer : initiator ratio. In order to keep the amount of polymer to a minimum yet retain the brightness of the phosphor, the organic coating was combined with an inorganic one for further improvements. In this doubly coated sample, the organic coating served the role of moisture barrier. The inorganic coating was the softening agent and was deposited by carrying out the sol-gel reaction in the presence of the polymer-coated sample. Analyses of the samples by SEM, TGA, and FTIR showed that the desired coatings were achieved in continuous, uniform fashion that led to the desired stabilization.; The interactions of an important but toxic anesthetic, bupivacaine, with different electron deficient aromatic acceptor moieties were studied primarily by UV-visible and proton NMR spectroscopy. The anesthetic, an electron donor, forms a pi-pi charge transfer complex with the acceptor. The complexation was monitored by changes in the wavelength and chemical shifts induced in the acceptor resonances. For reference and proof of concept the acceptor molecules, the synthesis of which is also presented, were first evaluated with models of the anesthetic. The ability of the anesthetic itself to form a complex with the acceptors was then measured. The equilibrium binding constant, K, was determined and used to calculate the free energy for complex formation. The acceptor molecules were covalently tethered to silica nanoparticles using silation and standard organic functional group interconversions and the efficiency of binding the dissolved donor measured. It is envisioned that the selective binding, when optimized, may prove useful for in vivo removal of overdoses of the anesthetic as well as other types of therapeutic and environmentally hazardous chemicals, and for liquid chromatography separations. |
