Sonochemically Assembled Photoluminescent Copper Modified Graphene Oxide Microspheres

Abstract

New accessible sonochemical assembly method is developed for the preparation of photoluminescent oil-filled silica@CuS/Cu2O/CuO-GO microspheres with green, yellow and red colors of emitted light. This method is based on the ultrasonic emulsification of a biphasic mixture consisting of CuS/Cu2O/CuO-graphene oxide (GO) nanocomposites with polyvinyl alcohol (PVA) (aqueous phase) and tetraethyl orthosilicate with sunflower oil (organic phase). CuS/Cu2O/CuO-GO nanocomposites are composed of sonochemically formed three phases of copper: covellite CuS (p-type semiconductor), cuprite Cu2O (Bloch p-type semiconductor) and CuO (charge transfer insulator). The photoluminescence property of microspheres results from the H-bridging between PVA and CuS/Cu2O/CuO-GO nanostructures, light absorption ability of Cu2O and charge transfer insulation by CuO. Substitution of PVA by S-containing methylene blue quenches fluorescence by enhanced dye adsorption on CuS/Cu2O/CuO-GO because of CuS and induced charge transfer. Non-S-containing malachite green is in non-ionized form and tends to be in the oil phase, prohibiting the charge transfer on CuS/Cu2O/CuO-GO.