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

Chiao Yi Teng, Ba Son Nguyen, Te Fu Yeh, Yuh Lang Lee, Shean Jen Chen, Hsisheng Teng

研究成果: Article同行評審

13 引文 斯高帕斯(Scopus)

摘要

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.

原文English
頁(從 - 到)8256-8265
頁數10
期刊Nanoscale
9
發行號24
DOIs
出版狀態Published - 2017 六月 28

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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