Live-tracking of beef freshness by sub-ppb level ammonia detection using WS2/rGO nanoflakes incorporating edge site-enriched acidic sulfur

Abstract

Highly accurate, easily accessible room temperature wireless gas-sensing technology can be utilized to monitor food freshness in real time to prevent food fraud and spoiled food consumption, thus safeguarding humans from diseases. In this work, we coupled a high-sensitivity ammonia gas sensor with interface transmitter/gateway Bluetooth technology to produce a wireless communication system for live tracking beef freshness. Herein, we propose a chemiresistive gas sensor containing hydrothermally produced sulfur-rich WS2/rGO hierarchical nanoflakes for gas sensing at RT. The as-developed nanohybrid was subjected to various physicochemical techniques, including XRD analysis, HR-SEM, FE-TEM, FTIR spectroscopy, Raman spectroscopy, and XPS. 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% at RT. 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. In addition, the composite had a 3.7-fold greater response to NH3 than other VOCs and great stability after 25 cycles. Moreover, the practical application potential was also evaluated for beef freshness monitoring. This technology can be expanded to rapidly tune gas-sensing active materials via nanoengineering for various applications in wireless gas sensors, such as air-quality, automobile-exhaust, food-deterioration, and gas-leak monitoring.