One-step synthesis and characterization of highly luminescent nitrogen and phosphorus co-doped carbon dots and their application as highly selective and sensitive nanoprobes for low level detection of uranyl ion in hair and water samples and application to cellular imaging

Abstract Innovative water-soluble nitrogen-phosphorus co-doped carbon dots (N,P-CDs) with bright luminescence and high quantum yields of 35.0% were synthesized via a simple and straightforward hydrothermal method, using an aqueous solution of alendronate sodium as a novel N and P containing single-source precursor. UV–vis absorption and photoluminescence spectroscopies, TEM, AFM, X-ray photoelectron spectroscopy, dynamic light scattering and FT-IR spectroscopy were used to characterize the morphological, structural and optical properties of the synthesized N,P-CDs. The N,P-CDs with excellent water solubility and biocompatibility possess a strong greenish blue emission centered at 420 nm (λ em  = 330 nm). Due to the existence and special response of bisphosphonate groups to uranyl ions (UO 2 2+ ), the fluorescence signal of N,P-CDs found to rapidly and selectively quench by this important cation. The linear response range to UO 2 2+ was from 0.01 to 2.5 μM with a limit of detection of 4.5 nM (S/N = 3). The prepared N,P-CDs was then applied to highly sensitive and selective detection of traces of uranyl ion in water and hair samples. Moreover, the prepared N,P-CDs were used as a nice bioimaging agent in BT474 cells, so that the cytotoxicity and cellular uptake of N,P-CDs were investigated by a MTT assay and through a localization study, respectively.