Colorimetric analysis through electrospun WO3/PAN membrane for indication of oxygen in food packaging using a smartphone

Colorimetric oxygen indicator for food packaging is highly demanding owing to their increasing need for food freshness inspection, production efficiency, and the package's integrity. It is satisfying to develop colorimetric oxygen indicators based on cost-effective, robust, and fast-responding chromic systems. Here, we synthesize WO3/polyacrylonitrile nanofiber membranes (WO3/PAN NFM) through electrospinning. The photo-reduced NFM shows a dark blue color and can be easily oxidized to light yellow color by the oxygen in the air, which can be worked as the colorimetric oxygen indicator. Most of the WO3 nanoparticles are distributed on the surface of the fiber, and the porosity of the NFMs also enables them to absorb oxygen molecules faster and easier. Furthermore, a smartphone was used in the visual detection by identifying the RGB value of the optical photos of NFMs. The application of smartphones has greatly shortened the detection time and reduced detection cost, providing a new strategy for detecting food quality anytime and anywhere.