Surface States Induced Photoluminescence Enhancement of Nitrogen-Doped Carbon Dots Via Post-Treatments

• Main Authors: Xian Wei, Shiliang Mei, Dan Yang, Guilin Zhang, Fengxian Xie, Wanlu Zhang, Ruiqian Guo
• Format: Article
• Language: English
• Published: SpringerOpen 2019-05-01
• Series: Nanoscale Research Letters
• Subjects: Carbon dots; N-doped; Surface states; PL enhancement; Solvent-dependent effect; Reduced-reaction effect
• Online Access: http://link.springer.com/article/10.1186/s11671-019-3008-9

Abstract The tunable photoluminescence (PL) of nitrogen-doped carbon dots (NCDs) has attracted much attention in recent years while the specific mechanism is still in dispute. Herein, NCDs with yellow emission were successfully synthesized via a facile hydrothermal approach. Three kinds of post-treatment routes were investigated to verify the influence of surface states on the PL emission of NCDs including solvent-dependent, reduced-reaction and metal-enhanced effect. The interaction mechanism was studied by absorption spectrum, structural characterizations, steady-state and time-resolved spectroscopy. When dispersed in different solvents, the as-prepared NCDs show tunable emission and PL enhancement attributed to hydrogen bonding between solvents and NCDs. Besides, the addition of NaBH4 can induce the reduction of the C=O bonds existing in original NCDs to C–O bonds and thus result in the enhancement of the intrinsic (n–π*) emission. Moreover, metal-enhanced fluorescence of NCDs can also be observed when adding Ag+ into initial NCD solution, which might be ascribed to aggregation-induced emission enhancement. These results for post-treated NCDs demonstrate that surface functional groups are responsible for PL emission and provide new possibilities like multi-image sensing and lighting application.