Synthesis of carbon quantum dots from apple juice and graphite: investigation of fluorescence and structural properties and use as an electrochemical sensor for measuring Letrozole

In this study, hydrothermal method was used to prepare carbon quantum dots from the natural apple juice and electrochemical synthesis method was used to prepare carbon quantum dots from graphite. The effect of synthesis type and current intensity on fluorescence and structural properties of the prepared carbon quantum dots was investigated. TEM and FTIR techniques were used for chemical and morphological study of carbon quantum dots. The synthesized carbon quantum dots were used for modification of the surface of the glassy carbon electrode and were used as an electrochemical sensor to measure Letrozole. According to the results, the sizes of apple juice-based carbon quantum dots were 5–10 nm and the sizes of graphite-based carbon quantum dots were 1–5 nm. With the increase and the intensity of the applied current in the electrochemical synthesis method, the particle size became larger and their fluorescence intensity decreased. The FTIR results confirmed the synthesis of the carbon quantum dots and the corresponding functional groups. Modified electrodes with a variety of carbon quantum dots showed a good response to Letrozole. The prepared sensor showed a good selectivity for Letrozole compared to similar drug (Clomifene). The sensitivity of the optimal sensor to Letrozole was 0.111 (A/M) while to Clomifene drug was 0.041 (A/M). The sensor was able to measure Letrozole in the concentration range of 1–12 × 5 M and the detection limit was 1.85 × 5 M. The results showed that the designed sensor with the appropriate recovery percentage can measure Letrozole in real drug samples.