Ultrasensitive visual detection of mycotoxin citrinin with yellow-light emitting carbon dot and Congo red

Ultrasensitive visual detection of mycotoxin citrinin is reported here using a novel yellow-light emitting Carbon dot (CD) and Congo red dye. Detection strategy is based on higher binding affinity of citrinin with diammonium citrate, and urea derived CD over Congo red in presence of Mg²⁺. Congo red statically quenched the yellow fluorescence of CD, resulting in emission in red region, which was restored in presence of citrinin. Visual limit of detection (LOD) of 10 pmol and spectroscopic LOD of 6.6 pmol/mL was achieved within 5 min of incubation with citrinin. The assembly was found to respond well for citrinin detection in the presence of Aflatoxin b1 (AFL b1) and Ochratoxin A (OTA), that frequently co-exist with citrinin in real food samples. The method exhibits immense potential to sense citrinin in sub-nanogram range by visual inspection in an inexpensive yet robust on-site detection platform in relevant food packaging and agricultural industry.