▎ 摘　　要

NOVELTY - A packaging film comprises 0.1-0.5 pt. wt. graphene, 0.01-0.03 pt. wt. silver nitrate, 0.1-1.0 pt. wt. modified pullulan polysaccharide and 100 pts. wt. polymer resin-based film. USE - Packaging film for cold storage of sweet cherries. ADVANTAGE - The packaging film has good antibacterial and gas-proof properties with high sterilization, oxygen and carbon dioxide barrier properties, water vapor transmission rate and base film strength, and effectively adjust the oxygen and carbon dioxide content in sweet cherries packaging bags at -0.5-4 degrees C, and delays the breathing rate of sweet cherries. The packaging film maintains proper moisture content in the packaging bag, suppresses mildew, browning, water rot and other deterioration of sweet cherries during cold storage after water pre-cooling, effectively extends the storage period of sweet cherries, and increases the freshness of sweet cherries out of the warehouse. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of packaging film, which involves ultrasonically dispersing graphene oxide in water for 1-3 hours to obtain graphene oxide dispersion having concentration of 1 mg/ml, adding silver nitrate to the dispersion, adding sodium borohydride, raising the temperature to 80-100 degrees C, reacting for 2-4 hours, filtering, washing, drying to obtain nano silver modified graphene, adding nano silver modified graphene to N,N-dimethylformamide solution, ultrasonically processing for 0.5 hour to obtain a solution having concentration of 1 mg/ml, adding pullulan polysaccharide or its derivatives to the solution, stirring at room temperature overnight, filtering the reaction solution, washing to obtain pullulan-modified nano silver-modified graphene, mixing the polymer resin base dried in an oven at 80 degrees C with the modified substance, homogenizing, heating, shearing, extruding through twin screw extruder and granulating to obtain a modified resin and blowing the modified resin.