Sulfuric acid

Hydrofluoric acid (HF, 49 wt%) and potassium hydroxide (KOH, GR 95%) were purchased from Aladdin (Shanghai, China). Hydrogen peroxide (H₂O₂, 30 wt%), sulfuric acid (H₂SO₄, 98 wt%), and ethanol were of analytical grade and received from Guangzhou Chemical Reagent Factory (Guangzhou, China). Photoresist SUN-120P was purchased from Suntific Microelectronic Materials Co., Ltd. (Weifang, Shandong, China) for patterning Si. 4-Methylbenzenethiol (4-MBT, 98%) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Rhodamine 6G (R6G) was purchased from J&K Chemical (Beijing, China). Methyl parathion solution (MPT, C₈H₁₀NO₅PS, 100 μg/mL in methanol) was obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). DP-type (100) 4” Si wafer with a resistivity of 0.001–0.005 Ω·cm was purchased from Lijing Optoelectronics Co., Ltd. (Suzhou, China). Deionized (DI) water (18.25 MΩ·cm at 25 °C) was prepared using a Milli-Q Plus water purification system (Sichuan Wortel Water Treatment Equipment Co., Ltd., Chengdu, Sichuan, China). All chemicals were used as received.

Corncob used in this experiment was harvested from a farm in Dezhou, Shandong Province, China. Corncob was ground to 40–60 mesh and then extracted using the acetone/ethanol solution (2:1, V/V). Acetone (AR) and sulfuric acid (AR) were purchased from Guangzhou Chemical Reagent Factory (Guangzhou, China). Oxalic acid dehydrate (AR), ethanol (AR) and activated carbon (adsorption value of iodine: 100–800 mg/g) were purchased from Tianjin DAMAO (Tianjin, China), Guangdong Guanghua (Guangzhou, China) and Kermel (Tianjin, China), respectively. All the chemical reagents were used without further purification.

Model compounds β-O-4 GG, β-5, and β-β were synthesized according to the reported methods [23 (link),24 (link),25 (link),26 (link)]. GVL (98%) was purchased from Macklin (Shanghai, China), sulfuric acid was obtained from Guangzhou Chemical Reagent (Guangzhou, China). All chemicals were used as received without further purification.