One-pot room temperature synthesis of orange-emitting carbon dots for highly-sensitive vitamin B12 sensing

Fluorescent carbon dots (CDs) with the long-wavelength emission have received increasing attention due to their promising application prospects in the biological field. The synthesis of CDs with long wavelength emission mainly focuses on the high temperature method, but the room temperature synthesis is still rarely studied. Herein, a simple room temperature strategy is developed for the preparation of orange-emitting CDs (O-CDs) by Schiff base crosslinking reaction between methyl-p-benzoquinone and triethylenetetramine. The proposed O-CDs show a strong excitation-dependent emission with a relative quantum yield of about 6.56%. Because of the strong inner filter effect, O-CDs can be well applied for the highly-sensitive detection of vitamin B12 (VB12). The intensity ratio (F/F₀) of O-CDs is linear against the concentration of VB12 from 50 nM to 200 μM with a low detection limit of 10 nM. Therefore, the obtained O-CDs nanoprobes provide a promising platform for pharmaceutical analysis applications.