Concentrated sulfuric acid

Acetone, n-hexane, ethyl acetate, concentrated sulfuric acid, sodium hydroxide, phosphoric acid, acetonitrile, ascorbic acid, methanol, formic acid, sodium acetate, acetic acid, hydrochloric acid, iron(III) chloride hexahydrate solution, ammonium acetate, were purchased from Guangzhou Chemical Reagent Factory (Guangzhou, China). phenolic compound standards [rutin (Rut), quercetin (Que), quercitrin (Quer), isoquercitrin (Iso), chlorogenic acid (ChA), syringic acid (SyA), ferulic acid (FeA), caffeic acid (CaA), resveratrol (Res), epicatechin (Epi), astragalin (Ast), scopoletin (Sco), galangal (Gal), catechuic acid (CatA), vanillic acid (VaA), benzoic acid (BeA), gallic acid (GaA), and protocatechuic acid (PrA)] were purchased from the National Institutes for Food and Drug Control (Beijing, China). 2,4,6-tris(2-pyridyl)-S-triazine (TPTZ), 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2ʹ-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) were purchased from Sigma-Aldrich (St. Louis, MO, USA).

Natural graphite powder was purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai, China). PEPA was synthesized according to [34 (link)]. Concentrated sulfuric acid (98%), sodium nitrate, potassium permanganate, 30% H₂O₂ solution, hydrochloric acid, TDI, dimethyl formamide (DMF), dichloroethane (EDC), absolute ethyl alcohol (EtOH), dimethyl ketone (DMK) and tetrahydrofuran (THF) were all of analytical reagent grade and provided by Guangzhou Chemical Reagent Factory (Guangzhou, China). IFR as described below, was mainly composed of ammonium polyphosphate.