Sonochemically Assembled Photoluminescent Copper-Modified Graphene Oxide Microspheres.

Abstract

A new accessible sonochemical assembly method is developed for the preparation of photoluminescent oil-filled silica@CuS/Cu2O/CuO-graphene oxide (GO) microspheres that emit light of green, yellow, and red colors. This method is based on the ultrasonic emulsification of a biphasic mixture consisting of CuS/Cu2O/CuO-graphene oxide (GO) nanocomposites with poly(vinyl 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 properties of microspheres result from 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 a nonionized form and tends to be in the oil phase, prohibiting the charge transfer on CuS/Cu2O/CuO-GO.