Nitrogen and phosphorus co-doped carbon dots as an effective fluorescence probe for the detection of doxorubicin and cell imaging

Nitrogen and phosphorus co-doped carbon dots (NPCDs) with bright blue fluorescence were established by a hydrothermal method using alanine and diammonium phosphate as raw materials. The NPCDs were characterized by transmitted electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, ultraviolet–visible absorption (UV–vis), and fluorescence spectroscopy to investigate the morphology, elemental composition, and optical properties. The NPCDs had good water solubility, high dispersibility with an average diameter of only 2.77 nm, and satisfactory optical properties with a fluorescence quantum yield of 17.2%. The NPCDs were employed for the detection of doxorubicin (DOX). A good linear response of the NPCDs in the range 0.5–6.5 μM was obtained for DOX with a detection limit of 12 nM. The NPCDs were also applied to the analysis of real samples, urine and serum, with a recovery of 92.0–109.3%. The low cytotoxicity and good biocompatibility of the NPCDs were indicated by an MTT assay and cell imaging of HeLa cells. Compared with other detection systems, using NPCDs for DOX detection was a facile and efficient method with good selectivity and sensitivity.