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Issue 24, 2017
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Roles of nitrogen functionalities in enhancing the excitation-independent green-color photoluminescence of graphene oxide dots

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Abstract

Fluorescent graphene oxide dots (GODs) are environmentally friendly and biocompatible materials for photoluminescence (PL) applications. In this study, we employed annealing and hydrothermal ammonia treatments at 500 and 140 °C, respectively, to introduce nitrogen functionalities into GODs for enhancing their green-color PL emissions. The hydrothermal treatment preferentially produces pyridinic and amino groups, whereas the annealing treatment produces pyrrolic and amide groups. The hydrothermally treated GODs (A-GODs) present a high conjugation of the nonbonding electrons of nitrogen in pyridinic and amino groups with the aromatic π orbital. This conjugation introduces a nitrogen nonbonding (nN 2p) state 0.3 eV above the oxygen nonbonding state (nO 2p state; the valence band maximum of the GODs). The GODs exhibit excitation-independent green-PL emissions at 530 nm with a maximum quantum yield (QY) of 12% at 470 nm excitation, whereas the A-GODs exhibit a maximum QY of 63%. The transformation of the solvent relaxation-governed π* → nO 2p transition in the GODs to the direct π* → nN 2p transition in the A-GODs possibly accounts for the substantial QY enhancement in the PL emissions. This study elucidates the role of nitrogen functionalities in the PL emissions of graphitic materials and proposes a strategy for designing the electronic structure to promote the PL performance.

Graphical abstract: Roles of nitrogen functionalities in enhancing the excitation-independent green-color photoluminescence of graphene oxide dots

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Publication details

The article was received on 12 Feb 2017, accepted on 15 May 2017 and first published on 16 May 2017


Article type: Paper
DOI: 10.1039/C7NR01037K
Citation: Nanoscale, 2017,9, 8256-8265
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    Roles of nitrogen functionalities in enhancing the excitation-independent green-color photoluminescence of graphene oxide dots

    C. Teng, B. Nguyen, T. Yeh, Y. Lee, S. Chen and H. Teng, Nanoscale, 2017, 9, 8256
    DOI: 10.1039/C7NR01037K

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