Sulfuric acid h2so4

PSf with 22,000 Da average molecular weight (Sigma-Aldrich, USA), polyvinylpyrrolidone (PVP) (K 30, Sigma-Aldrich, USA), 1-methyl-2-pyrrolidinone (NMP) (99.5%, Sigma-Aldrich, USA) and N-N-Dimethylformamide (DMF) (99.8%, Sigma-Aldrich, USA) were used for PSf ultrafiltration substrates preparation. m-Phenylenediamine (MPD) flakes (99%, Aldrich, China) and 1,3,5-Benzenetricarbonyl chloride (TMC) (98%, Sigma-Aldrich, USA) dispersed in hexane (98%, Aldrich, China) were used for the IP process. Graphite (Sigma-Aldrich, USA), sodium nitrate (NaNO₃) (Beijing Chemical Factory, China), hydrogen peroxide (H₂O₂) (Beijing Chemical Factory, China), sulfuric acid (H₂SO₄) (Beijing Chemical Factory, China), and potassium permanganate (KMnO₄) (Sigma-Aldrich, USA) were used for GO nano-sheets preparation. For membranes chlorine resistance tests, sodium hypochlorite (NaClO) (Chemical Supply Pty Ltd, China) was used. Sodium chloride (NaCl) (ACS reagent, Beijing Chemical Factory, China) was dissolved in deionized water (DI) produced with a Milli-Q system (Millipore, USA) for FO tests.

(100) oriented smooth silicon wafers (n-type) were purchased from GRINM Semiconductor Materials Co., LTD. Pillar-structured silicon substrates were prepared by standard photolithography techniques³⁶ . In our experiments, we fabricated pillar-structured silicon substrates with adjustable pillar diameters (20, 40 and 60 μm) and pillar periods (10, 20 and 30 μm), constant pillar heights (20 µm) and circular pillar-top shape (Fig. S2). After resist-stripping (Microposit Remover 1165), the substrates were cleaned using ethanol and acetone prior to the chemical modification process. According to previously published procedures, three kinds of typical POMs such as Anderson-structured (NH₄)₃[CoMo₆O₂₄H₆] (denoted as CoMo₆), Keggin-structured Na₃PW₁₂O₄₀ (denoted as PW₁₂) and Wells-Dawson-structured K₆P₂W₁₈O₆₂ (denoted as P₂W₁₈) were successfully synthesized^{33 (link)–35} . Doubly distilled water (>1.82 MΩ cm, MilliQ system) was used. Sulfuric acid (H₂SO₄, 95%-98%, AR), Hydrogen peroxide (H₂O₂, 30%, AR) were purchased from Beijing Chemical Works and used without further purification. Trichloro-(1 H, 1 H, 2 H, 2H-perfluorooctyl) silane (PFOS) was purchased from Sigma-Aldrich.

All chemicals, including chitosan (Sinopharm Chemical Reagent Co., Ltd. China), sulfuric acid (H₂SO₄; Beijing Chemical Works, China), sodium hydroxide (NaOH; Beijing Chemical Works, China) and phosphate buffer saline (PBS; Leagene, China), were in analytical grade and used without further purification. Deionized water was used throughout the whole experiment.

Thirty-four PAs analytical standards were all sourced from Phytolab (Vestenbergsgreuth, Germany), the structures of these compounds are shown in Figure S1 (Supplementary Material). Formic acid (HPLC grade) was obtained from DIKMA Technologies Inc. (Lake Forest, CA, USA) and ammonium bicarbonate (99% purity, HPLC grade) from MREDA Technologies Inc. (Beijing, China). Both ammonium hydroxide in water (NH₄OH, 25%) and sulfuric acid (H₂SO₄, 98%) were purchased from Beijing Chemical Works (Beijing, China). Methanol (MeOH, UPLC/MS grade) was purchased from Thermo Fisher Scientific (Shanghai, China) and water from Wahaha Company (Hangzhou, China). Stock solutions of the 34 available PAs standards were prepared in acetonitrile (100 μg/mL) and stored at –20 °C. The standard working solution (1 µg/mL) consisted of mixed respective PAs reference standards in MeOH (HPLC grade) and stored at 4 °C.