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An optical sensing platform for the detection of an important mycotoxin, aflatoxin B1 (AFB1), in the absence of a bioactive environment is explored. In this work, a fluorescence-based sensing technique was designed by combining graphene quantum dots (GQDs) and AFB1 via fluorescence quenching, where AFB1 acts as the quencher of GQD fluorescence. GQDs were synthesized through a single-step hydrothermal reaction from the leaves of “curry tree” (Murraya Koenigii) at 200 °C. The fluorescent GQDs were quenched by AFB1 (quencher), which itself is detecting the analyte. Hence, this study reports the direct sensing of the mycotoxin AFB1 without the involvement of inhibitors or biological entities. The possible mode of quenching is the nonradiative resonance energy transfer between the GQDs and the AFB1 molecules. This innovative sensor could detect AFB1 in the range from 5 to 800 ng mL–1 with a detection limit of 0.158 ng mL–1. The interferent study was also carried out in the presence of different mycotoxins and carbohydrates (d-fructose, cellulose, and starch), which demonstrated the high selectivity and robustness of the sensor in the complex sample matrix. The recovery percentage of the spiked samples was also calculated to be up to 106.8%. Thus, this study reports the first GQD based optical sensor for AFB1.

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Bisphenol A (BPA), an endocrine-disrupting compound, is used in beverage and food packaging, leaches into the water and food source cycles affecting humans and the environment due to the thermodynamic instability of BPA. Herein, we report a sensitive, quick, economical, simple, and selective electrochemical platform exploring green synthesized silver nanoparticles (AgNps) anchored in reduced graphene oxide (RGO) composite for BPA determination in milk and water samples. For confirmation of the synthesis of AgNps-RGO composite, characterizations were done with X-ray diffraction, UV–visible spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and scanning electron microscopy. The sensor platform was fabricated using indium tin oxide (ITO) glass substrate through electrophoretic deposition. The sensor electrode (AgNps-RGO/ITO) achieved a sensitivity of 2.56 μA (log μM)−1 cm−2, a detection limit of 0.14 μM, and linear response in the range of 1.9 × 10−10 to 0.820 μM. This is mainly ascribed to the synergetic benefits of AgNps and RGO, which are synthesized in situ through the green route using Cinnamomum tamala leaf extract. The sensor showed insignificant interference from its analogs, inorganic and organic species, along with good repeatability and reproducibility. The developed sensor demonstrated good potential application to detect BPA with acceptable recoveries and their relative standard deviation values.

Ochratoxin-A (OTA) is a fungal mycotoxin that is present in most of the food stuff, and shows adverse effects on human beings. Therefore, the rapid and accurate detection of OTA is necessary. Here, ceria nanoparticles based microfluidic nanobiochip was fabricated for the electrochemical detection of OTA. Ceria nanoparticles were synthesized using a chemical coprecipitation method and characterized by various techniques. Raman spectroscopy confirmed the formation of fluorite cubic structure. Transmission electron microscopy (TEM) exhibited the formation of very small size (4-5 nm) with nearly spherical shape nanoparticles. Microfluidic nanobiochip was fabricated using 300 μm microfluidic channel using polydimethylsiloxane (PDMS). Simultaneously, indium tin oxide (ITO) coated Corning glass was used for the fabrication of immunoelectrodes platform using antibodies (anti-OTA) for the OTA detection. The detection range was achieved from 350 pg ml À 1 to 10 ng ml À 1 with sensitivity of 7.5 μA ng À 1 mL cm À 2 , without any interference effect using differential pulse voltammetry.