Fluorescent starch nanocrystal and preparation method and application thereof

A method for preparing a fluorescent starch nanocrystal, the method comprising:

• (1) an activating step consisting of adding 1 w/v % to 8 w/v % of starch nanocrystal to a sodium hydroxide solution having a pH of 8.0 to 11.0 and continuously stirring for 2 to 6 h to obtain an alkali-activated starch nanocrystal, which is subsequently separated and then washed with aqueous ethanol;
• (2) adding 0.1 w/v % to 0.8 w/v % of benzoyl peroxide to 60 v/v % to 95 v/v % aqueous ethanol and continuously stirring at 100 to 400 rpm at room temperature until benzoyl peroxide is fully dissolved to form a benzoyl peroxide solution, then adding 1 v/v % to 5 v/v % γ-aminopropyl triethoxysilane to the benzoyl peroxide solution to carry out hydrolysis for 0.5 to 6 h to form a silane hydrolysate solution;
• (3) adding the activated starch nanocrystal of step (1) to the silane hydrolysate solution of step (2) and continuously stirring for 2 to 6 h to form a reaction mixture followed by conducting rotary evaporation of the reaction mixture under a vacuum degree of −0.1 to −0.06 Mpa and at a temperature of 50 to 55° C., followed by drying at 40 to 55° C. for 3 to 12 d, and the dried amino silane modified starch nanocrystal is re-dispersed and washed with water until pH value is constant before drying at 40 to 55° C. and then passing through a 60 to 100 mesh screen and
• (4) adding 0.1 w/v % to 2.0 w/v % of the amino silane modified starch nanocrystal obtained from step (3) to a 55 v/v % to 90 v/v % aqueous methanol containing 0.1 w/v % to 1.5 w/v % fluorescein isothiocyanate and keeping in dark place at room temperature for 12 to 36 h to obtain the fluorescent starch nanocrystal.

A method for preparing a fluorescent starch nanocrystal, the method comprising:

• (1) an activating step consisting of adding 1 w/v % to 8 w/v % of starch nanocrystal to a sodium hydroxide solution having a pH of 8.0 to 11.0 and continuously stirring for 2 to 6 h to obtain an alkali-activated starch nanocrystal, which is subsequently separated and then washed with aqueous ethanol;
• (2) adding 0.1 w/v % to 0.8 w/v % of benzoyl peroxide to 60 v/v % to 95 v/v % aqueous ethanol and continuously stirring at 100 to 400 rpm at room temperature until benzoyl peroxide is fully dissolved to form a benzoyl peroxide solution, then adding 1 v/v % to 5 v/v % γ-aminopropyl triethoxysilane to the benzoyl peroxide solution to carry out hydrolysis for 0.5 to 6 h to form a silane hydrolysate solution;
• (3) adding the activated starch nanocrystal of step (1) to the silane hydrolysate solution of step (2) and continuously stirring for 2 to 6 h to form a reaction mixture followed by conducting rotary evaporation of the reaction mixture under a vacuum degree of −0.1 to −0.06 Mpa and at a temperature of 50 to 55° C., followed by drying at 40 to 55° C. for 3 to 12 d, and the dried amino silane modified starch nanocrystal is re-dispersed and washed with water until pH value is constant before drying at 40 to 55° C. and then passing through a 60 to 100 mesh screen and
• (4) adding 0.1 w/v % to 2.0 w/v % of the amino silane modified starch nanocrystal obtained from step (3) to a 55 v/v % to 90 v/v % aqueous methanol containing 0.1 w/v % to 1.5 w/v % fluorescein isothiocyanate and keeping in dark place at room temperature for 12 to 36 h to obtain the fluorescent starch nanocrystal, which is subjected to centrifugal washing until the supernatant has no characteristic absorption peak in a scanning spectrum, and the washed fluorescent starch nanocrystal is then dried in the dark at 40° C. and passed through a 60 to 100 mesh screen.