N-doped Graphene : Beyond Single Substitution for Enhanced Molecular Sensing

1. CNMS Staff Science Highlight N-doped Graphene: Beyond Single Substitution for Enhanced Molecular Sensing Scientific Achievement Substitutionaldoping of graphene with nitrogen results in the disruption of the ideal sp2hybridization, locally inducing significant changes in the electronic properties and chemical reactivity which has been exploited to enhance molecular sensing. • Significance • We describe the synthesis and imaging of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding a unique N-doping site composed of two quasi-adjacent substitutional nitrogen atoms within the same graphenesub-lattice (denoted N2AA). • Research Details • CNMS capability:Experiments were conducted with aCNMS-built variable temperature scanning tunneling microscope, whose operating temperature varies from 25 K to 300 K. • A simple but efficient method to synthesize large-area and highly-crystalline monolayer NG sheets is established. • As-synthesized NG sheets contain an abundant amount of N dopants within the same graphene sub-lattice (N2AA) comprising 80% of all identified defects, as well as more complex configurations. • It was demonstrated for the first time that individual NG sheets could be used to efficiently identify organic molecules through a significant enhancement of the Raman signal. Experimental and simulated STM images of as-synthesized NG sheets. (a) Large-area STM image of the NG illustrating the presence of numerous N-dopants with a similar peapod-like configuration (highlighted by white arrows), The upper and lower squares are used to indicate the undoped region and N2AAdopants. (b) Highly resolved STM image of a N2AA dopant. (c) Ball-stick structural model of the N2AA dopant and simulated STM image obtained using first-principles calculations. The carbon and nitrogen atoms are illustrated using gray and cyan balls, respectively. (d) STM spectroscopy measured on N2AAdopants (red) and on undoped graphene region (blue). R. Lv, Q. Li, A. R. Botello-Méndez, T. Hayashi, B. Wang, A. Berkdemir, Q. Hao, A. L. Elías1, R. Cruz-Silva, H. R. Gutiérrez, Y. A. Kim, H. Muramatsu, J. Zhu, M. Endo, H. Terrones, J. Charlier, M. Pan, M. Terrones, Nature Scientific Reports, 2,586(2012)