Development of Multimodal Sensors for Calcium-Based Food Adulterant Using Tannic Acid Derived Functional Nanomaterials

A facile tannic acid (TA) based multimodal sensor was developed to detect calcium based artificial ripening agent calcium carbide (CaC2) through colorimetric and fluorescence methods. The interaction of TA with CaC2 is proposed to be through the −OH groups of TA which can be confirmed by various spectrochemical analysis. Carbon dots (TA-CDs) with a quantum yield of 34% were synthesized from TA by hydrothermal method and evaluated for their efficiency as a fluorescent “turn-off” sensor for the detection of CaC2. The properties and the interaction of the TA-CDs with CaC2 were analyzed by various spectroscopic methods such as UV–visible, FT-IR, Raman, and photoluminescence spectroscopy. The change in the morphology and the stability of the TA-CDs were studied by using HR-TEM, zeta potential analysis, and various other parameters. The LOD and LOQ of sensing were found to be 147 and 447 ppm, respectively. Further, TA based paper strips were developed which showed promising results enabling point-of-care detection of CaC2.