Wireless gas-sensing technology can be utilized to monitor food freshness in real time to prevent food fraud and spoiled food consumption. Nanoflake sensors have the advantage over traditional gas sensors that they do not need excessive heat or power consumption, making them ideal for such real-time applications. There are sensors available for many nitrogen-containing gaseous indicators of spoilage, including reduced graphene oxide (rGO) which is selective for ammonia.
In this work (open access) the authors coupled a high-sensitivity ammonia gas sensor with Bluetooth technology to produce a wireless communication system for live tracking beef freshness. They used a chemiresistive gas sensor containing hydrothermally produced sulfur-rich WS2/rGO hierarchical nanoflakes for gas sensing in real time. This nanohybrid was evaluated using various physicochemical techniques, including XRD analysis, HR-SEM, FE-TEM, FTIR spectroscopy, Raman spectroscopy, and XPS.
They reported that the sensitivity of the sulfur-rich WS2/rGO nanohybrid towards NH3 was twice as high as that of pristine sulfur-rich WS2 with an LOD of 0.5 ppb and a response of 7.5%. The NH3-sensing mechanism was attributed to a negative charge donated by NH3 on the positively charged sulfur-rich WS2/rGO composite, which enabled it to interact with certain functional groups (SO3H, –OH, and H2O) and enhanced the resistance of the material. The composite had a 3.7-fold greater response to NH3 than to other volatile organic compounds and good stability after 25 cycles.
They concluded that the system was practical for real-time monitoring of beef in the supply chain and, coupled with AI, could be used to detect anomalies (i.e. indicators of fraud)
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