Preparation and Performance Evaluation of Spiropyran-Labeled Fluorescent Chitosan Electrospun Anti-Counterfeiting Nanofibers

With the rapid development of the economy, new imitation methods are keeping emerging and posing a huge challenge to anti-counterfeiting technology. Due to the advantages such as good concealment, high recognizability, water repellency, and dirt resistance, fluorescent fiber has attracted great attention from researchers. To impart good fluorescence to chitosan (CS) for the preparation of anti-counterfeiting fiber, various amounts of fluorescent molecules — carboxyl-containing spiropyran (SP)—were used to label CS to prepare a series of CS–SP with different degrees of labeling (DL). Then, nanofiber membranes were produced by electrospinning using the CS–SP/PVA blend spinning solutions. Effects of the DL on application performance of the CS–SP were studied. It was found that, labeling appropriate amounts of SP units onto CS was an effective way to endow the CS with good fluorescence property. With the increase in the DL of the CS–SP, its fluorescence intensity increased initially, reached the maximum when the DL was 0.499 mol%, and then decreased. At the DL of 0.499 mol%, the CS–SP/PVA nanofiber membrane could emit bright fluorescence, of which the color was able to change dynamically along with the irradiation time of UV light. Meanwhile, the labeling of SP unit would not bring about adverse effects on surface morphology of the electrospun CS–SP/PVA nanofiber membrane. The fluorescent CS–SP nanofibers have overcome many shortcomings of the commonly used fluorescent fibers and shown great application potential in the anti-counterfeiting field.