Carbon Nanotube-Based Sensors for Intelligent Packaging

Abstract

Aim: The aim of this project is to develop a gas-phase optical sensor for oxygen detection in intelligent packaging. The optical sensor will be based on near-infrared light that can penetrate through visibly opaque materials, including plastics, paper, and cardboard. An automated near-infrared camera will be used to precisely and quickly inform the user of any change in the integrity of packages that are vacuum-sealed or atmospherically modified. Method: The optical sensor is based on near-infrared fluorescence that is emitted from carbon nanotubes (CNTs). CNTs exhibit a sensitive and photostable fluorescence that is well suited for sensing applications. The CNTs are wrapped by one of two types of DNA, AT(15) and GT(15), through sonication. These wrappings control the responsivity of the CNTs to different gases while also solubilizing them for further processing. The resulting solutions are then drop-casted into a film. We subsequently investigate the response of the film in the presence of the target gas, oxygen, at different concentrations. Finally, we evaluate the selectivity of the sensor in the presence other gases including carbon dioxide, ethylene, and ammonia. Results: Our results reveal that the fluorescence intensity of the AT(15) and GT(15)-wrapped CNTs quenches upon the exposure of oxygen. Interestingly, we observe that the different CNT chiralities respond distinctly to the presence of oxygen. In particular, whereas some chiralities undergo an irreversible loss in fluorescence after several oxygen exposure cycles, the (8,6) chirality demonstrates stability over multiple cycles for both AT(15) and GT(15)-wrapped CNTs. Finally, our results show a concentration-dependent and selective response of both the AT(15)- or GT(15)-wrapped CNT sensors to the oxygen, as we observed no significant response to the other studied gases. Conclusion: We developed an optical, gas-phase sensor based on CNT fluorescence for intelligent food packaging. The sensor is selective to oxygen and demonstrates reversibility over multiple oxygen exposure cycles. These sensors can be used to monitor the integrity of packages that are vacuum-sealed or otherwise atmospherically modified. This technology can thus provide consumers and manufactures a means of preventing early spoilage and ensuring food quality.