Colorful Polymer Compositions with Dyed Graphene Oxide Nanosheets

A water suspension of graphene oxide nanosheets (GONSs) obtained via exfoliation of a graphite oxide was treated with a solution of rhodamine 6G. It was found that adding the dye results in the destruction of the GONS water suspension and the precipitation of dyed graphene oxide. The precipitate, washed out of the excess dye and subjected to a second dispersal via sonification, provides a stable suspension of dyed GONS in water or dimethylformamide. The GONS dyeing produces shifts of major absorption bands of the dye in solutions or in polymer compositions toward larger wavelengths. We also found that the stability of a dye subjected to ultraviolet irradiation increases if the dye is bound to a GONS. The increased stability resulted from excitation transfer from dye to a GO nanosheet and its subsequent reduction. 1. Introduction Graphite oxide is known since the 19th century [1]. The current surge of interest to graphite oxide is due to not only its application as a prospective material for electrodes, membranes, and polymer additives [2–7] but also to a new avenue which opened after the discovery of the unique properties of graphene [8–10]. Contrary to many other carbon materials, graphite oxide is hydrophilic and is capable of forming colloidal solutions in water, spirits, and other polar solvents, where GO splits into thin sheets of up to one carbon layer thickness [11–13]. Graphite oxide “solubility” is due to a large number of oxygen-containing groups chemically bound to graphene layers. The presence of these groups deteriorates the mechanical and conducting properties of GO nanosheets with respect to those of graphene. A hydrazine processing restores [14–16] the GONS π-system and results in properties similar to those of graphene. Generally, the GO nanosheets possess [17] sites with different reaction abilities; therefore, it is difficult to predict beforehand the results of interactions between a GONS and different molecules. This letter describes the products of interactions between a GONS and the dye rhodamine 6G (R6G, C28H31ClN2O3) and then discusses some properties of this product. The goal of this work was to produce dyed GONSs in transparent polymer compositions. We prepared films of polymethylmethacrylate (PMMA) modified using both dye and dyed GONSs. The film samples were characterized using spectral methods. 2. Experimental Details Our GO samples were prepared according to Hummers and Offeman’s method [18] using a procedure whose details are described elsewhere [19]. Suspensions were prepared by mixing GO (100？mg) with water (100？mL) in