A spectroscopic study to assess the photogeneration of singlet oxygen by graphene oxide

Abstract

The photogeneration of singlet oxygen (1O2) during short irradiation times of graphene oxide (GO) is assessed under visible light with soft irradiation conditions either directly monitoring the phosphorescence emission of 1O2 at ca. 1275 nm, or indirectly by means of the fluorescent probe 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA). Results obtained using both methodologies lead to the conclusion that 1O2 generation is negligible under our experimental conditions. In the case of using ABDA very small emission changes were recorded, which could be attributed to other side reactions. Special care should be taken when using this spectroscopic probe to assess the generation of 1O2, since ABDA and related probes based on the reactivity of the anthracene fluorophore can also detect electron transfer processes. This kind of approaches have been less explored in the field of Materials Science at the nanoscale, and we believe that the knowledge on the lack of generation of 1O2 by irradiated GO is informative and useful, especially for the assessment of the environmental and biological toxicity of nanomaterials based on GO.