Flash silica

Flash silica (high-purity grade, Sigma-Aldrich), HAuCl₄.3H₂O (hydrogen tetrachloroaurate trihydrate, 48% in gold, Sigma-Aldrich), AgNO₃ (silver nitrate, ≥99%, Sigma-Aldrich), C₆H₆N₂O₂ (2-nitroaniline, 98%, Sigma-Aldrich), C₆H₈N₂ (o-phenylenediamine, ≥99%, Sigma-Aldrich), NaBH₄ (sodium borohydride, powder, ≥98%, Sigma-Aldrich). All chemicals were analytical grade reagents. Deionized water (18.2 MΩ) was used throughout the experiments.

Oleic acid (90%), 4-aminophenyl disulfide (98%), 2,2′-ethylendianiline (97%), trimethyl orthoformate (99%), 1,6-hexanediol (97%), 1-methylimidazole (99%), meta-chloroperoxybenzoic acid (77%), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (98%), dichloromethane (≥99%), ethyl acetate (≥99%), diethyl ether (≥99%), hexane (≥99%), methanol (≥99%), ethanol (96%), tetrahydrofuran (99%), tetrafluoroboric acid (57% in Et₂O), sulfuric acid (99%), NaCl (≥99%), NaHCO₃ (≥99%), Na₂SO₄ (≥99%) and Na₂SO₃ (≥99%) were purchased from Sigma-Aldrich Co., St. Louis, MO, USA, and all of them were used without further purification. All solvents used were of technical and analytical grade. Flash silica (High-purity grade, pore size 60 Å, 230–400 mesh particle size, 40–63 μm particle size, Sigma-Aldrich Co.) was used for purification. Thin-layer chromatography (TLC) was carried out by using silica gel on TLC plates (5 cm × 20 cm, silica gel matrix, fluorescent indicator, Sigma-Aldrich Co.)