Preparation method of nanoscaled dye@zif-8-based colorimetric sensor and application thereof in food quality evaluation

A method for preparing a nanoscaled dye@ZIF-8-based colorimetric sensor, comprising:

• (a) dissolving Zn(CH3COO)2·2H2O in deionized water to obtain a Zn(CH3COO)2 solution, wherein a ratio of a weight of the Zn(CH3COO)2·2H2O to a volume of the deionized water is 2.70 g:
• 45 mL;
• and dissolving 2-methylimidazole in deionized water to obtain a 2-methylimidazole solution, wherein a ratio of a weight of the 2-methylimidazole to a volume of the deionized water is 22.23 g:
• 100 mL;
• (b) mixing the Zn(CH3COO)2 solution and the 2-methylimidazole solution following by stirring and standing to obtain a precipitate, wherein a volume ratio of the Zn(CH3COO)2 solution to the 2-methylimidazole solution is 45:57.6;
• and subjecting the precipitate to centrifugal washing respectively with water and ethanol and drying to obtain a zeolitic imidazolate framework-8 (ZIF-8) nanomaterial;
• (c) dispersing the ZIF-8 nanomaterial with ethanol to obtain a ZIF-8 dispersion with a concentration of 2 mg/mL;
• (d) preparing a colorimetric solution with a concentration of 2 mg/mL, wherein the colorimetric solution is a pH indicator ethanol solution or a metalloporphyrin dichloromethane solution;
• a ratio of a weight of a pH indicator to a volume of ethanol in the pH indicator ethanol solution is 20 mg:
• 10 mL;
• a ratio of a weight of a metalloporphyrin compound to a volume of dichloromethane in the metalloporphyrin dichloromethane solution is 20 mg:
• 10 mL;
• the pH indicator is selected from the group consisting of cresol red, brilliant yellow, and neutral red;
• and the metalloporphyrin compound is selected from the group consisting of 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23H-porphine nickel (II), 5, 10, 15, 20-tetraphenyl-21H,23H-porphine zinc, and 5, 10, 15, 20-tetrakis(pentafluorophenyl)-21H, 23H-porphyrin iron (III) chloride;
• (e) mixing the colorimetric solution with the ZIF-8 dispersion in a volume ratio of 1:1 to obtain a mixed solution;
• and
• (f) adding polyethylene glycol-300 to the mixed solution followed by ultrasonic treatment to obtain a nanoscaled dye@ZIF-8 colorimetric material, wherein the polyethylene glycol-300 is 20% by volume of the mixed solution;
• and fixing the nanoscaled dye@ZIF-8 colorimetric material on a substrate to obtain the nanoscaled dye@ZIF-8-based colorimetric sensor.