Titanium tetraisopropoxide

TiO_x or TaO_x was coated on the SrTiO₃:Al loaded with Rh, Cr₂O₃, and CoOOH via photodeposition in the same solvent used for Rh, Cr₂O₃, and CoOOH deposition before the filtration^{26 (link)}. For TiO_x coating, titanium tetraisopropoxide (FUJIFILM Wako Pure Chemical Corporation, 11.1 μL, 37 μmol) with 30 vol% H₂O₂ (FUJIFILM Wako Pure Chemical Corporation, 200 μL, 3.2 mmol) was added into the suspension containing SrTiO₃:Al loaded with Rh, Cr₂O₃, and CoOOH. This was then mixed via ultrasonication for 5 min. Subsequently, 1 M NaOH aqueous solution (74.6 μL) was added to the solution where the ratio between the added Na⁺ versus Ti contained in titanium tetraisopropoxide was 2:1. For TaO_x coating, tantalum(V) chloride (MilliporeSigma, 8.0 mg, 22 μmol) with 30 vol% H₂O₂ (FUJIFILM Wako Pure Chemical Corporation, 500 μL, 8.0 μmol) was added to the suspension containing the SrTiO₃:Al loaded with Rh, Cr₂O₃, and CoOOH. This was then mixed with ultrasonication for 5 min. Subsequently, 1 M NaOH aqueous solution (113 μL) was added to the solution where the ratio between the added Na⁺ versus Ta contained in tantalum(V) chloride was 5:1. The resulting suspension was irradiated with 370 nm LED (730 mW) for 12 h, and then the precipitates were separated by filtration and washed with ethanol three times. The collected slurry was not dried further.

Titanium tetraisopropoxide (TTIP, 95%), methylamine aqueous solution (40%), acetonitrile (99.5%), ethanol (99.5%), styrene (St, 99%), p-styrenesulfonic acid sodium salt (NaSS, 80%), potassium persulfate (KPS, 95%), sodium chloride (99.5%), tetraethyl orthosilicate (TEOS, 95%), hydrochloric acid (HCl, 0.10 mol/L), and methylene blue (MB, 98.5%) were purchased from FUJIFILM Wako Pure Chemical Corp. (Osaka, Japan). 3-Methacryloxypropyltrimethoxysilane (MPTMS, 95%) was obtained from Shin-Etsu Chemical Co. (Tokyo, Japan). The inhibitor for the St monomer was removed using an inhibitor removal column. Deionized water (>18.2 MΩ cm) was prepared for experimental use.

The chemicals used in this study were of analytical grade. Oxalic acid dihydrate and 2-propanol were purchased from Kanto Chemical Co., Inc. (Tokyo, Japan). Titanium tetraisopropoxide and butylamine were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). Purified water was purchased from Kyoei Co., Ltd. (Tokyo, Japan). Hydrogen peroxide (31%) was purchased from Santoku Chemical Industries, Ltd. (Tokyo, Japan). Ethanol was purchased from Ueno Chemical Industries, Ltd. (Osaka, Japan) and was dried over 4A molecular sieves prior to use. The other chemicals were used without further purification. The ultraviolet germicidal lamp (GL-15) used for UV irradiation was purchased from Panasonic Co. (Osaka, Japan). The quartz glass substrate was purchased from Akishima-Glass Inc. (Okayama, Japan). The quartz glass substrate of dimensions 20 mm × 20 mm × 1.1 mm was washed in water with a detergent for 30 min through sonicated stirring. These glass substrates were rinsed in 2-propanol for 30 min using sonicated stirring and then dried in a drying oven at 70 °C.