title: Photobleaching and stabilization of carbon nanodots produced by solvothermal synthesis.
abstract: In this work we performed a detailed investigation of the photostability of bottom-up produced carbon nanodots (CDs) prepared from citric acid and urea by solvothermal synthesis. Analytical ultracentrifugation (AUC) reveals that the CDs have a hydrodynamic diameter of <1 nm and a very narrow size distribution. In the community it is widely assumed that CDs are photo-stable. In contrast, we found that CDs exposed to UV-irradiation exhibit noteworthy fluorescence degeneration compared to freshly prepared CDs or CDs stored in the dark, indicating that fluorescence bleaching is caused by a photochemical process. We found that fluorescence intensity decay due to exposure to UV-irradiation is accelerated in the presence of oxygen and identified the surface status of CDs as the decisive factor of fluorescence bleaching of CDs. Based on a discussion on the underlying mechanisms we show how to avoid photobleaching of CDs.
authors.affiliation: Friedrich-Alexander University Erlangen-Nürnberg, Institute of Particle Technology, Cauerstrasse 4, 91058 Erlangen, Germany. wolfgang.peukert@fau.de.
authors.forename: Wenshuo
authors.initials: W
authors.lastname: Wang
authors.forename: Cornelia
authors.initials: C
authors.lastname: Damm
authors.forename: Johannes
authors.initials: J
authors.lastname: Walter
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Nacken
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Peukert