Preparation method and application of multifunctional intelligent cellulose-based visual label

A method for preparing a cellulose-based visual label, comprising the following steps:

• step 1, carboxylation modification, comprising:
• adding straw fibers into an oxalic acid aqueous solution with a mass percentage concentration of 25%-50%, heating the straw fibers and the oxalic acid aqueous solution to a temperature of 78 degrees Celsius (° C.) to 82° C. along with magnetic stirring for 0.5 hours (h) to 1 h to perform a reaction between the straw fibers and the oxalic acid aqueous solution;
• after the reaction is finished, obtaining a reaction product, adding absolute ethanol into the reaction product to remove residual oxalic acid of the reaction product and thereby to obtain a first product, and performing rotary evaporation on the first product to recycle ethanol in the first product and obtain a second product;
• filtering the second product to obtain filtrate, flushing precipitate in the filtrate with the ethanol until a conductivity of the filtrate is stable, and thereby obtaining carboxylated fibers;
• step 2, cationic grafting, comprising:
• adding the carboxylated fibers into a chitosan quaternary ammonium salt aqueous solution with a concentration of 20 grams per liter (g/L) to 30 g/L, performing magnetic stirring on the carboxylated fibers and the chitosan quaternary ammonium salt aqueous solution for 0.5 h to 4 h at room temperature, and then filtering and washing with water to obtain quaternized fibers;
• step 3, preparation of a composite dye solution, comprising:
• dissolving bromothymol blue and methyl red at a mass ratio of 1:(0.9-1) in a sodium hydroxide solution with a concentration of 0.045 moles per liter (mol/L) to 0.055 mol/L to obtain the composite dye solution;
• step 4, preparation of responsive fibers, comprising:
• adding the quaternized fibers into the composite dye solution, placing the composite dye solution added with the quaternized fibers in an oscillating water bath machine to perform an oscillatory adsorption for 3.5 h to 4 h, and then eluting dyes physically attached to surfaces of the quaternized fibers with sodium hydroxide solution with a concentration of 0.045 mol/L to 0.055 mol/L, and washing the quaternized fibers with distilled water until a potential of hydrogen (pH) of the composite dye solution is neutral, thereby obtaining the responsive fibers;
• and
• step 5, preparation of the cellulose-based visual label, comprising:
• performing vacuum filtration on the responsive fibers to obtain paper with a basis weight of 65 grams per square meter (g/m2) to 70 g/m2, and then drying the paper to obtain the cellulose-based visual label.