Introduction Zoledronic acid, a nitrogen containing bisphosphonate compound, is an inhibitor of osteoclastic bone resorption and is clinically used for the treatment of tumor induced hypercalcemia, bone metastases arising from any cancer, and for the prevention of bone metastases associated with advanced breast cancer and prostate cancer [1-2]. Hence, quantification of Zoledronic acid in biological samples is critical to provide a daily quality control analysis. This paper reports, for the first time, a one-step and facile preparation of the nitrogen-doped carbon quantum dots (N-CDs) from date kernel by the hydrothermal method. The synthesized NCDs were used as a label- free platform for the determination of Zoledronic acid. Experimental CNDs were synthesized from kernel date. A certain amount of Fe (III) solution was added to the CDs. This caused quenching of the fluorescence of CDs. Addition of Zoledronic acid to the mixture caused restoring of the fluorescence of the system. The increased fluorescence intensity was linearly proportional with Zoledronic acid concentration in a given range. Results and discussion The obtained N-CDs were fully characterized by high-resolution transmission electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, Raman spectroscopy, UV-vis absorption and photoluminescence (PL) spectroscopy. These characterizations were consistent with the previous reports [3]. The influence of pH, dosage of N-CDs and incubation time was investigated and the optimum conditions were established. Due to the synergistic impression of the static quenching mechanism arising from the formation of a stable non-fluorescent complex between CD and Fe3+ [4] and inner filter effect, upon addition of ferric ions, fluorescence intensity of the N-CDs solution was gradually decreased (state Off). The CD/Fe3+ complex were used for the detection of Zoledronic acid by restored fluorescence intensity (
