Hydroquinone

Ag/Au alloy disks (70 : 30 at%, 5 mm diameter, 200 μm thickness) for npAu preparation were obtained according to a literature procedure.^{18 (link)} 6-Azidohexyl-1-thioacetate^{38–40 (link)} as building block for SAM formation, tris(benzyl-triazolylmethyl)amine (TBTA)^{41,42 (link)} as co-catalyst for the CuAAC reaction and the photosensitizers 2,9,16,23-tetrakis(2-propyn-1-yloxy)phthalocyanine zinc(ii) (ZnPc-3, 1),^{43 (link)} 2,9,16,23-tetrakis(5-hexyn-1-yloxy)phthalocyanine zinc(ii) (ZnPc-6, 2),^{9 (link)} and 5,10,15,20-tetrakis(4-(prop-2-yn-1-yloxy)phenyl)porphyrin zinc(ii) (ZnTPP-3, 3)^{44 (link)} were all synthesized as described elsewhere. The following chemicals and solvents were bought as indicated and were all used as received without further purification: Cu(MeCN)₄PF₆ (97%, Aldrich), hydroquinone (Merck), 2,5-diphenylfuran (DPF, >98.0%, TCI), EtOH (abs., reagent grade, VWR), THF (reagent grade, ≥99.0%, VWR), DMF (analytical reagent grade, ≥99.5%, VWR), HNO₃ (analytical reagent grade, 65%, VWR), HNO₃ (NORMATOM, ultra-pure for trace analysis, 67%, VWR) and HCl (NORMATOM, ultra-pure for trace analysis, 34%, VWR).

The following chemicals of analytical grade (Merck) and tri-distilled water were used for the preparation of photocatalysts and solutions: Phenol (C₆H₆O), Catechol (C₆H₆O₂) Hydroquinone (C₆H₆O₂), Zinc Acetate dihydrate (ZAC, Zn(CH₃COO)₂·2H₂O), Hydrochloric Acid (HCl) potassium dichromate (K₂Cr₂O₇), sulphuric acid (H₂SO₄), Ethanol (95% purity), Sodium Hydroxide (NaOH), Ammonium chloride (NH₄Cl), Ammonium Hydroxide (NH₄OH), Potassium ferricyanide (K₃Fe(CN)₆), and 4-Aminoantipyrine. Duranit inert balls 3–5 mm (80% SiO₂–20% Al₂O₃) were purchased from VEREINIGTE FÜLLKÖRPER-FABRIKEN-VFF (Baumbach, Germany).

Alloy disks with Ag/Au ratio of 70 : 30 at% were prepared within our group according to a previously published procedure.^{63 (link)} American white gold (12 karat, Ag/Au 50 : 50 wt%) as starting alloy for npAu foils was bought at Noris Blattgold GmbH, Schwabach, Germany. For the CuAAC, the catalyst Cu(MeCN)₄PF₆ (97%) from Aldrich, hydroquinone from Merck and the co-catalyst tris(benzyl-triazolylmethyl)amine (TBTA), which was obtained by a literature procedure,^{64,65 (link)} were used. The chemical ¹O₂ quencher 1,3-diphenylisobenzofuran (DPBF, >95%) was received from TCI. All solvents including ethanol (abs., reagent grade), THF (reagent grade, ≥99.0%), DMF (analytical reagent grade, ≥99.5%), HNO₃ (analytical reagent grade, 65% and NORMATOM, ultra-pure for trace analysis, 67%) and HCl (NORMATOM, ultra-pure for trace analysis, 34%) were bought at VWR and were used as received without further purification.

Styrene (C₈H₈) was an Aldrich product (Sigma-Aldrich Inc., St. Louis, MO, USA) and was washed 3 times with 10% aqueous sodium hydroxide (NaOH) solution, dried over calcium dichloride (CaCl₂), and distilled under reduced pressure over calcium hydride (CaH₂) before use. Hydroquinone (C₆H₆O₂), dichloroethane (C₂H₄Cl₂), methacryloyl chloride (C₄H₅ClO), chloroform (CHCl₃), sodium hydrogen carbonate (NaHCO₃), and lead oxide (PbO) were Merck products (Merck & Co. Inc., Kenilworth, NJ, USA). Boron nitride (BN) powder was 1 μm in size and Aldrich product. PEG-1000, PEG-1500, PEG-10,000 were Merck products. The PEG DM-1000, PEG DM-1500, PEG DM-10,000 macro crosslinkers were synthesized from PEG-1000, PEG-1500, PEG-10,000 polymers by our group. PEG-DM is the abbreviation of poly (ethylene glycol dimethylmethacrylate) in PEG DM-1000, PEG DM-1500, PEG DM-10,000 [52 ,53 (link)].

The chemicals used to prepare MDPB were of analytical grade. 1-bromododecane and 3-hydroxypyridine were procured from Spectrochem Pvt. Ltd., Mumbai, India. Hydroquinone, acrylic acid, and benzoyl chloride were procured from Merck, Mumbai, India. MDPB was synthesized by the reaction of hydroxy dodecylpyridinium bromide and methacryloyl chloride.
0.72 g of acrylic acid was dissolved in 10 mL of distilled ethanol. This solution was added to 1.4 g of benzoyl chloride under 5 mL of 0.1 g of Hydroquinone at a temperature of 72‒76°C. The obtained product, acryloyl chloride, was again dissolved in methanol and further subjected to re-distillation at a temperature of 72‒76°C to obtain methacryloyl chloride. Hydroquinone was added as a catalyst to prevent the polymerization of acrylic acid. Hydroxy dodecylpyridinium bromide was prepared from 1-bromododecane and 3-hydroxypyridine by the reflux method. Finally, MDPB was prepared by mixing the prepared hydroxy dodecylpyridinium bromide and methacryloyl chloride at a ratio of 1:1. The obtained product, MDPB, was further confirmed by an infrared (IR) spectrometer. The obtained IR spectrum of the prepared compound was compared with the standard compound, and the frequencies were assigned (Figure 1).

Hydroquinone (HQ) was purchased from Merck and was recrystallized from hot water before use. 4,4′-(4,4′-Sulfonylbis-(1,4-phenylene)bis(oxy)) diphenol was synthesized from 4,4′-difluorodiphenyl sulfone and Hydroquinone. 4,4′-Difluorodiphenyl sulfone was provided from Merck and recrystallized from toluene, and 3,3′-disulfonated-4,4′-difluorodiphenyl sulfone (DFS) was synthesized from nonsulfonated dihalide and recrystallized from (water/2-propanol) mixture. Potassium carbonate (Merck) was dried at 120 °C in a vacuum oven overnight. Dimethylacetamide (DMAc) from Merck was dried over calcium hydride for 12 h and then distilled under reduced pressure and stored over molecular sieves. Ethanol, toluene, 2-propanol, fuming sulfuric acid (30%) (All from Merck) were used as received.