Preparation of Graphene-Incorporated Chitosan-Polyvinyl Alcohol Composite Film Loaded with Copper-1-(2-Pyridylazo)-2-naphthol Complex and Its Application to Monitor Shrimp Freshness

A colorimetric composite film (Cu-PAN@G-CS/PVA) for the detection of H₂S in shrimp meat by indicator displacement was prepared by tape casting method using copper (Ⅱ)-1-(2-pyridylazo)-2-naphthol complex (Cu-PAN) as a H₂S-sensitive material, chitosan (CS) combined with polyvinyl alcohol (PVA) as a film-forming material and graphene as a sensitizing material. The morphology and functional groups of Cu-PAN@G-CS/PVA were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and the sensing performance to H₂S was examined by ultraviolet-visible (UV-vis) absorption spectroscopy. Experimental results showed that the color of the Cu-PAN@G-CS/PVA film changed from purplish red to yellow with increasing H₂S concentration. This film was used to monitor the freshness of Penaeus chinensis stored at 4 or 25 ℃. It was shown that the trend of the color difference value (ΔE) of the Cu-PAN@G-CS/PVA film had a good correlation with the total volatile basic nitrogen (TVB-N) content of the sample. Therefore, the Cu-PAN@G-CS/PVA film could accurately and rapidly indicate the freshness of P. chinensis, which may provide a reference for the development of intelligent packaging of aquatic products.