Development\nof Multimodal Sensors for Calcium-Based\nFood Adulterant Using Tannic Acid Derived Functional Nanomaterials

A facile tannic acid (TA) based multimodal sensor was\ndeveloped\nto detect calcium based artificial ripening agent calcium carbide\n(CaC<sub>2</sub>) through colorimetric and fluorescence methods. The\ninteraction of TA with CaC<sub>2</sub> is proposed to be through the\n−OH groups of TA which can be confirmed by various spectrochemical\nanalysis. Carbon dots (TA-CDs) with a quantum yield of 34% were\nsynthesized from TA by hydrothermal method and evaluated for their\nefficiency as a fluorescent “turn-off” sensor for the\ndetection of CaC<sub>2</sub>. The properties and the interaction of\nthe TA-CDs with CaC<sub>2</sub> were analyzed by various spectroscopic\nmethods such as UV–visible, FT-IR, Raman, and photoluminescence\nspectroscopy. The change in the morphology and the stability of the\nTA-CDs were studied by using HR-TEM, zeta potential analysis, and\nvarious other parameters. The LOD and LOQ of sensing were found to\nbe 147 and 447 ppm, respectively. Further, TA based paper strips\nwere developed which showed promising results enabling point-of-care\ndetection of CaC<sub>2</sub>.