title: Tunable optical transition in polymeric carbon nitrides synthesized via bulk thermal condensation.
abstract: Polymeric derivatives of dicyandiamide were synthesized via a bulk thermal condensation method, using a range of process temperatures between 400 and 610 °C. The obtained carbon nitride powders exhibit an optical transition in the UV-green range that has been assigned to the direct bandgap of a semiconductor-like material. Within this context, the apparent bandgap is linearly tunable with increasing process temperatures, showing a temperature coefficient of - 1.7(1) meV K(-1) between 2.5 and 3.0 eV. The obtained results show a predominant optical transition within the tri-s-triazine unit of the polymer, with a bathochromic shift originating from a gradually increasing degree of polymerization.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie, Institute for Heterogeneous Material Systems, Berlin, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Tyborski
authors.forename: C
authors.initials: C
authors.lastname: Merschjann
authors.forename: S
authors.initials: S
authors.lastname: Orthmann
authors.forename: F
authors.initials: F
authors.lastname: Yang
authors.forename: M-Ch
authors.initials: MC
authors.lastname: Lux-Steiner
authors.forename: Th
authors.initials: T
authors.lastname: Schedel-Niedrig