Molecularly imprinted optosensing sensor for highly selective and sensitive recognition of sulfadiazine in seawater and shrimp samples

Two types of molecularly imprinted silica layers appended to quantum dots (MIP-QDs) for sulfonamides (SAs) were fabricated using reverse microemulsion surface grafting with 3-aminopropyltriethoxysilane as a functional monomer and sulfadimethoxine (SDM) and sulfadiazine (SDZ) as template molecules. The characterizations of both MIP-QDs were analyzed by ATR-FT-IR, SEM, and TEM, and their imprinting and specific fluorescence quenching mechanisms were elucidated through selectivity fluorescence response experiments. Finally, the MIP-QDs synthesized with SDZ as template exhibited excellent selective fluorescence quenching properties, which were attributed to the complementary imprinting cavities of the MIP-QDs to the templates and to the specific interactions between the functional monomer and the template molecules. Furthermore, a selective MIP-QD-based fluorescence optosensing sensor for the highly selective and sensitive recognition of SDZ was developed and successfully applied to detect SDZ in seawater and shrimp samples. Under optimal conditions, linear relationships with correlation coefficients 0.9971 were obtained along the range of 0.005-1.5 mg/L to SDZ. The limit of detection was 0.004 μg/L and 0.79 μg/kg for SDZ in seawater and shrimp samples, respectively. Excellent recoveries (82.7-99.9%) with a relative standard deviation (below 6.1%) were obtained for both samples spiked with three levels of SDZ. The proposed MIP-QD method provides a powerful tool for the rapid and sensitive determination of SDZ in real samples.