Selenium-Functionalized Graphene Oxide That Can Modulate the Balance of Reactive Oxygen Species.

Graphene oxide (GO) is an important two-dimensional material since it is water-soluble and can be functionalized to adapt to different applications. However, the current covalent functionalization methods usually require hash conditions, long duration, and sometimes even multiple steps, while noncovalent functionalization is inevitably unstable, especially under a physiological environment where competing species exist. Diselenide bond is a dynamic covalent bond and can respond to both redox conditions and visible light irradiation in a sensitive manner. Thus, in this work by combining the stimuli response of diselenide bond and the oxidative/radical attackable nature of GO, we achieved the in situ covalent functionalization of GO simply by stirring GO with diselenide-containing molecules in aqueous solution. The covalent functionalization was proved by Fourier transform infrared, time-of-flight secondary ion mass spectrometry, atomic force microscopy, thermogravimetric analysis, and so forth, and the functionalization mechanism was deduced to involve both redox reaction and radical addition reaction according to the X-ray photoelectron spectrscopy, atomic emission spectroscopy, and Raman spectroscopy. Moreover, we modified GO with a biocompatible diselenide-containing polymer (mPEGSe) and found selenium-functionalized GO could modulate the balance of reactive oxygen species (ROS). GOSe could decrease ROS level by accelerating the reduction of peroxides when the ROS concentration is high while boosting the ROS level by in situ generating ROS when its concentration is relatively low.