Dual-emission fluorescent ZnS nanosheets for sensitive detection of carcinogenic Sudan dyes in chili powder and lipstick samples.

Sudan dyes are carcinogenic colorants illicitly added to foods and cosmetics, posing serious health risks. Herein, a rapid dual-emission fluorescent probe based on two-dimensional (2D) ZnS nanosheets is developed for sensitive detection of Sudan dyes (III/IV). Compared with conventional nanoparticles, the nanosheet structure offers high surface accessibility, excellent dispersion, and reduced aggregation, enabling reliable sensing in complex matrices. The ZnS nanosheets (NS), synthesized via the solvothermal method, exhibit stable fluorescence emissions at 521 and 557 nm with photobleaching resistance. Fluorescence quenching by Sudan dyes is governed by the inner filter effect, allowing a rapid response within 20 s over a broad pH range (2-10). The probe shows high selectivity and reproducibility, with detection limits of 339/436 nmol L-1 for Sudan III and 4.0/3.5 nmol L-1 for Sudan IV at 521/557 nm. Practical applicability is confirmed in spiked chili powder and lipstick samples, achieving recoveries of 96-101 % (RSD < 5 %).