N, S-CDs for colorimetric/fluorometric dual-mode nanosensor and smartphone-based determination of curcumin in fruits

N,S-doped carbon dots (N,S-CDs) were fabricated by utilizing m-phenylenediamine and β-mercaptoethylamine as precursors and designed as colorimetric/fluorometric dual-mode nanosensors. The curcumin (CUR) could quench the green fluorescence around 509 nm. The mechanism of fluorescence quenching was mainly attributed to the static quenching effect. Meanwhile, the color alterations of sensing solution were acquired with CUR contents changing from 0 to 50 μM. Thereby, the quantitative measurement of CUR could be materialized based on colorimetric and fluorometric dual-mode sensing methods. The wide linearity and low detection limit (LOD) were achieved through this dual-mode nanosensor. The feasibility of this system was continuously confirmed via the assay of CUR in fruit samples. Moreover, a portable smartphone-assisted detection system based on N, S-CDs suggested a facile, inexpensive, and efficient approach for detecting CUR in actual fruit samples.