Concentrated sulfuric acid

Polyether polyol (type:1012a) and isocyanate (type:1012b) were purchased from Shenzhen Keshengda Trading Co., Ltd. (Shenzhen, China). Concentrated sulfuric acid (98%, AR), potassium permanganate (AR), and sodium nitrate (AR) were supplied by the Beijing Chemical Factory (Beijing, China). Hydrogen peroxide (30%, AR) and anhydrous ethanol (AR) were bought from the Tianjin Yongda Chemical Reagent Co., Ltd. (Tianjin, China). Phytic acid (PA) and the silane coupling agent KH550 (GR) was bought from the National Pharmaceutical Group Chemical Reagent Co., Ltd. (Shanghai, China). Ammonium polyphosphate (APP) was purchased from the Tangshan Yongfa Flame Retardant Material Factory (Tangshan, China). Graphite powder was bought from the Tianjin Zhiyuan Chemical Reagent Co., Ltd. (Tianjin, China). Expandable graphite (EG, type: ADT150) was purchased from the Shijiazhuang Kepeng Flame-retardant Material Factory (Shijiazhuang, China).

1,10-diaminodecane (DMD) was purchased from Wuxi Yinda Co., Ltd. Terephthalic acid (PTA) was purchased from Jinan Mingxin Chemical Co., Ltd. 1,12-dodecanedicarboxylic acid (TDA) was purchased from Wuhan Yuancheng Group. Benzoic acid (BA) and sodium hypophosphite (SHP) were purchased from Shanghai Macklin Biochemical Co., Ltd. Concentrated sulfuric acid (96%) and N, N-dimethylformamide (DMF) were purchased from Beijing Chemical Reagent Company. All the reagents were used without future purification.

Graphene oxide (GO) was prepared by the modified two steps Hummers’ method^{49 (link),50 (link)}. In a typical synthesis protocol, 4.0 g of 200 mesh natural graphite oxide flakes (Alfa Aesar), 48 mL of concentrated sulfuric acid (Beijing Chemical Works), 8.0 g of potassium permanganate (Shanghai Aladdin Biochemical Technology Co., Ltd), and 8.0 g of phosphorus pentoxide (Beijing Chemical Works) were added in turn to synthesize pre-oxidized GO, which was then washed by deionized water till the vacuum filtrate becomes neutral. Then, 3.0 g of the pre-oxidized GO was dried in an oven at 60 °C for 12 h and was further oxidized with 3.0 g sodium nitrate (Beijing Chemical Works) and 18.2 g potassium permanganate (Shanghai Aladdin Biochemical Technology Co., Ltd.) in an ice bath. The mixed solution was then transferred to a 35 °C water bath for 2 h. After that, the solution was diluted with 300 mL of deionized water, followed by adding 10 mL of 30% hydrogen peroxide (Shanghai Aladdin Biochemical Technology Co., Ltd.) to completely react the excess potassium permanganate. The mixture was purified in dialysis tubes for a week, and followed by centrifugation at 8000 r/min twice to remove the liquid supernatant. The retained sticky GO dispersion was diluted to a suspension with 0.06 g/L GO.

Natural graphite flakes (8,000 mesh, 99.95% purity), p-propylaniline, p-n-octylaniline, and p-n-dodecylaniline were supplied by Aladdin. Concentrated sulfuric acid (95–98%), concentrated hydrochloric acid (36–38%), potassium permanganate, and solvents used in this work were all analytically pure and purchased from Beijing Chemical Factory (China). Hydrogen peroxide (H₂O₂) and sodium nitrate were supplied by LaiYang Shi Kant chemical company. Cellulose ester membrane was supplied by Hangzhou Special Paper Co. Ltd.

Glucose, rutin, gallic acid, cyclic adenosine monophosphate (CAMP) and ursolic acid were HPLC grade and purchased from the National Standard Substance Center (Beijing, China). Methanol and potassium dihydrogen phosphate were chromatographic pure reagents purchased from Xi’an Chemical Factory (Xi’an, China). Sodium nitrite, aluminum nitrate, sodium hydroxide, ethanol, methanol, phenol, concentrated sulfuric acid, glacial acetic acid, and vanillin were analytical grade from Beijing Chemical Factory (Beijing, China).