Emissive carbon dots derived from natural liquid fuels and its biological sensing for copper ions

Liquid fuels rich in aliphatic and aromatic carbon compounds are utilized as the carbon precursors for the production of carbon dots (CDs) for the first time. Herein we demonstrate the preparation of liquid fuels derived CDs (d-CDs and f-CDs) via chemical oxidation approach and the subsequent application for cerebral copper ions (Cu²⁺) sensing in rat brain microdialysate. The as-prepared CDs exhibits different morphology and photoluminescence properties depending on the different component of precursors. The luminescence of the as-prepared d-CDs can be significantly quenched upon addition of Cu²⁺, in which Cu²⁺ are trapped by the oxygen and nitrogen functional groups surrounding the emissive d-CDs. Moreover, the fluorescence intensity of d-CDs is sensitive to the concentration of Cu²⁺ with a linear relationship in the range of 0-4 μM, and a detection limit was estimated to be 0.039 μM. Simultaneously, we found out that the luminescent d-CDs manifests an extraordinarily high selectivity which can clearly discriminate Cu²⁺ from other interference species in aqueous solution and therefore substantially endows d-CDs as a fluorescent sensing platform for Cu²⁺. According to this nature, we employed d-CDs for the in vivo analysis of Cu²⁺ in the rat brain microdialysate and the measured basal level of Cu²⁺ was estimated to be 2.82 ± 0.16 μM (n = 3) even in the presence of other metal ions, biological substances and amino acids that commonly existing in the rat brain.