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.
Highlights
In recent years, carbon dots (CDs) have been regarded as a new class of nanoscale light-emitting material with remarkable chemical properties like tunable emission and great biocompatibility [1, 2]
The as-prepared nitrogen-doped carbon dots (NCDs) in different solvents show tunable emission and PL enhancement attributed to hydrogen bonding between solvents and NCDs
The addition of NaBH4 can induce the reduction of the C=O bonds existing in original NCDs to C–O bonds and result in the enhancement of the intrinsic (n–π*) emission
Summary
Carbon dots (CDs) have been regarded as a new class of nanoscale light-emitting material with remarkable chemical properties like tunable emission and great biocompatibility [1, 2]. The photoluminescence (PL) origin of CDs is still in dispute, which has been mainly ascribed to intrinsic emission and surface defect emission [9, 20]. To address this issue, it is necessary to develop facile post-treatments to control PL properties and verify the role of surface states through post-treatments in this work
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