Formation mechanism of carbon dots: From chemical structures to fluorescent behaviors

One-step microwave synthesis of red-emissive carbon dots for cell imaging in extreme acidity and light emitting diodes

“…The peak at 6.3 (in d 6 -DMSO) was attributed to the amino hydrogen, which was consistent with the data shown in the literature. 40 When CD 3 OD was used as the solvent, the hydrogen in the amino group could exchange with deuterium ions, resulting in the disappearance of the peak in the 1 H-NMR spectrum. In the 1 H-NMR spectrum of the R-CDs, the signals in the 9.5-10.0 ppm region were assigned to the hydrogen on the hydroxyl group, which was consistent with the XPS results; the spectral peaks with chemical shis between 6.8 and 8.0 could be assigned to hydrogens on aromatic rings, indicating that the R-CDs contained aromatic ring structures.…”

“…This indicated that the protons interact strongly with groups on the surface of the R-CDs. It has been reported that o-PD can generate phenazine-type compounds during the synthesis of CDs, 36,40 and that the protonation of the phenazine groups caused a signicant red shi in the uorescence emission. 36 The XPS and 1 H-NMR results also conrmed that the surfaces of the R-CDs contained pyridine nitrogen and amino groups.…”

“…It has been reported that o-PD can generate 2,3-diaminophenazine and 2-amino-3-hydroxyphenazine during the synthesis of CDs. 36,40 We speculated that the groups with different basicity on the surface of the R-CDs may be similar to 2,3-diaminophenazine, such as amino groups, pyrazine groups, etc. To conrm this, a thin-layer chromatography (TLC) experiment was performed to investigate the products during microwave reaction for 1 min and 4 min (Fig.…”

“…Recently, the preparation of CDs using o-phenylenediamine (o-PD) as a carbon source has attracted the attention of many researchers; [34][35][36][37][38][39][40][41][42][43] o-PD can not only dope the CDs with nitrogen atoms to improve their optical properties but also modify the CD surface with amino groups, enabling CDs to detect pH, identify substances, etc. 44,45 However, to the best of our knowledge, there have been no reports on the direct microwavemethod preparation of R-CDs using o-PD as a carbon source to detect extremely low pH values by uorescence enhancement.…”

Novel fluorescence sensor for the selective recognition of tetracycline based on molecularly imprinted polymer-capped N-doped carbon dots

“…Carbon dots (CDs) are a kind of uorescent nanomaterials, which have attracted extensive attention due to excellent optical properties and biocompatibility, simple preparation process, low toxicity and relatively low cost. 13,14 Because of these advantages, CDs are widely applied in many elds such as bioimaging, photocatalysis, sensors, and drug delivery. CDs can be synthesized by many methods including hydrothermal reactions, 15 microwave-assisted technique, 16 laser ablation, 17 chemical oxidation 18 and solid-state reaction.…”