Preparation and electrochemiluminescent and photoluminescent properties of a graphene oxide colloid

A simple strategy was developed for the preparation of a graphene oxide (GO) colloid with good water-solubility and stability by the reaction of graphite oxide with nitric acid. The as-prepared GO colloid was characterized by atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. The results demonstrated that the GO colloid had an average height of 0.8 nm, widths in the range ∼10 to 60 nm, and contained abundant carboxyl, and hydroxyl groups. Strong electrochemiluminescent emission was observed from the GO colloid in the presence of K2S2O8. The electrochemiluminescent signal of this system was quite stable with time, and its mechanism was ascribed to the electron-transfer of GO colloid and SO4·- radicals produced by electroreduction of S2O82- ions. The photoluminescent activity of the GO colloid was also studied. The results indicated that it had a visible photoluminescence, excellent photostability, and stable photoluminescence intensity in a wide pH range.