Near-Infrared Optical Gas Sensor for Intelligent Food Packaging

Aim: This project focuses on the design and fabrication of an intelligent packaging system based on a gas-phase optical sensor. The optical sensor emits near-infrared light that is able to penetrate through visibly opaque materials, including plastics, paper, and cardboard. The sensor will provide real-time monitoring of the quality of packaged food products using a specialized, near-infrared camera.

Method: The near-infrared signal from the optical sensor is based on the fluorescence emissions of carbon nanotubes (CNTs). The CNTs are wrapped with single-stranded DNA that is able to spontaneously assemble onto the nanotubes following sonication. This wrapping not only solubilizes the CNTs in aqueous solutions but also controls the optical responsivity of the CNTs towards different gases. The resulting solutions are then incorporated into an agar hydrogel. We subsequently investigate the response of the sensor in the presence of ammonia, a gas associated with food spoilage. Finally, we investigate the selectivity of the sensor in the presence of other gases.

Results: Our results show that the fluorescence intensity of the AT₍₁₅₎-wrapped CNTs increases upon exposure to ammonia. Interestingly, we observe distinct responses from different CNT chiralities. We also observe a concentration-dependent and selective response of the AT₍₁₅₎-wrapped CNT sensor to the target gas, with no significant response to the other gases used in this study.

Conclusion: Here, we developed an optical sensor based on the fluorescence of CNTs for intelligent food packaging applications. The sensor can be used to monitor food quality in real-time, notifying the user on onset of food spoilage. This sensor thus offers both consumers and manufacturers a quick and accessible means of ensuring food quality and safety.