Acetic acid aqueous solution (0.5 vol%) was prepared; chitosan (Mw 5.0×10³, deacetylation 40%) was dissolved to 0.1 mg/mL; 500 mg graphite was added (chitosan:graphite = 1:10); ultrasonic treatment at 75°C, 600 W, 0.5 hour; centrifuged at 1000 rpm for 10 min; centrifugally washed with 0.5% acetic acid at 15000 rpm for 0.5 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 10000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (2 vol%) was prepared; chitosan (Mw 2.0×10⁴, deacetylation 53%) was dissolved to 0.2 mg/mL; 200 mg graphite was added (chitosan:graphite = 1:5); ultrasonic treatment at 60°C, 540 W, 2 hours; centrifuged at 2000 rpm for 10 min; centrifugally washed with 2% acetic acid at 20000 rpm for 1 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 5000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (4 vol%) was prepared; chitosan (Mw 1.5×10⁵, deacetylation 60%) was dissolved to 0.5 mg/mL; 100 mg graphite was added; ultrasonic treatment performed; porous graphene and graphene quantum dot obtained by centrifugation and dialysis. XPS characterization of graphite vs. porous graphene (FIG 2), photoluminescence of graphene quantum dot (FIG 3), TEM and AFM of graphene quantum dot (FIG 4) were reported.

Acetic acid aqueous solution (0.5 vol%) was prepared; chitosan (Mw 5.0×10³, deacetylation 40%) was dissolved to 0.1 mg/mL; 500 mg graphite was added (chitosan:graphite = 1:10); ultrasonic treatment at 75°C, 600 W, 0.5 hour; centrifuged at 1000 rpm for 10 min; centrifugally washed with 0.5% acetic acid at 15000 rpm for 0.5 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 10000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (2 vol%) was prepared; chitosan (Mw 2.0×10⁴, deacetylation 53%) was dissolved to 0.2 mg/mL; 200 mg graphite was added (chitosan:graphite = 1:5); ultrasonic treatment at 60°C, 540 W, 2 hours; centrifuged at 2000 rpm for 10 min; centrifugally washed with 2% acetic acid at 20000 rpm for 1 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 5000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (4 vol%) was prepared; chitosan (Mw 1.5×10⁵, deacetylation 60%) was dissolved to 0.5 mg/mL; 100 mg graphite was added; ultrasonic treatment performed; porous graphene and graphene quantum dot obtained by centrifugation and dialysis. XPS characterization of graphite vs. porous graphene (FIG 2), photoluminescence of graphene quantum dot (FIG 3), TEM and AFM of graphene quantum dot (FIG 4) were reported.

Acetic acid aqueous solution (0.5 vol%) was prepared; chitosan (Mw 5.0×10³, deacetylation 40%) was dissolved to 0.1 mg/mL; 500 mg graphite was added (chitosan:graphite = 1:10); ultrasonic treatment at 75°C, 600 W, 0.5 hour; centrifuged at 1000 rpm for 10 min; centrifugally washed with 0.5% acetic acid at 15000 rpm for 0.5 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 10000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (2 vol%) was prepared; chitosan (Mw 2.0×10⁴, deacetylation 53%) was dissolved to 0.2 mg/mL; 200 mg graphite was added (chitosan:graphite = 1:5); ultrasonic treatment at 60°C, 540 W, 2 hours; centrifuged at 2000 rpm for 10 min; centrifugally washed with 2% acetic acid at 20000 rpm for 1 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 5000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (4 vol%) was prepared; chitosan (Mw 1.5×10⁵, deacetylation 60%) was dissolved to 0.5 mg/mL; 100 mg graphite was added; ultrasonic treatment performed; porous graphene and graphene quantum dot obtained by centrifugation and dialysis. XPS characterization of graphite vs. porous graphene (FIG 2), photoluminescence of graphene quantum dot (FIG 3), TEM and AFM of graphene quantum dot (FIG 4) were reported.

Acetic acid aqueous solution (0.5 vol%) was prepared; chitosan (Mw 5.0×10³, deacetylation 40%) was dissolved to 0.1 mg/mL; 500 mg graphite was added (chitosan:graphite = 1:10); ultrasonic treatment at 75°C, 600 W, 0.5 hour; centrifuged at 1000 rpm for 10 min; centrifugally washed with 0.5% acetic acid at 15000 rpm for 0.5 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 10000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (2 vol%) was prepared; chitosan (Mw 2.0×10⁴, deacetylation 53%) was dissolved to 0.2 mg/mL; 200 mg graphite was added (chitosan:graphite = 1:5); ultrasonic treatment at 60°C, 540 W, 2 hours; centrifuged at 2000 rpm for 10 min; centrifugally washed with 2% acetic acid at 20000 rpm for 1 hour; precipitate = porous graphene; supernatant dialyzed with MWCO 5000 bag to yield graphene quantum dot.

Acetic acid aqueous solution (4 vol%) was prepared; chitosan (Mw 1.5×10⁵, deacetylation 60%) was dissolved to 0.5 mg/mL; 100 mg graphite was added; ultrasonic treatment performed; porous graphene and graphene quantum dot obtained by centrifugation and dialysis. XPS characterization of graphite vs. porous graphene (FIG 2), photoluminescence of graphene quantum dot (FIG 3), TEM and AFM of graphene quantum dot (FIG 4) were reported.