Tetraethyl orthosilicate

Tetraethyl orthosilicate (TEOS), 3-(trimethoxysilyl)propyl methacrylate (3-MPMA), methacrylic acid, and adipic acid dihydrazide (ADH) were purchased from Tokyo Chemical Industry Co., LTD (Tokyo, Japan). Fumed silica with an average diameter of 250 nm and bisphenol A glycerolate dimethacrylate (BisGMA) resin were obtained from Sigma-Aldrich (St. Louis, MO, USA). The aluminum oxide nanopowder dispersion with an average particle size of 10 nm (Al₂O₃ gamma, 20 wt.%) was purchased from US Research Nanomaterials, Inc. (Houston, TX, USA). The ammonia solution (28–30 wt.%) and sodium hydroxide pellets (NaOH) were received from Samchun Pure Chemical Co., Ltd. (Pyeongtaek, Korea). The bisphenol A type epoxy resin (YD-128) was obtained from Kukdo Chemical (Seoul, Korea). Irgacure 651 was received from Ciba Specialty Chemicals (Basel, Switzerland). Drierite (≥98% CaSO₄) was obtained from W.A. Hammond Drierite Co., LTD (Xenia, OH, USA). Deionized (DI) water was used for all experiments.

Tetraethyl orthosilicate
(TEOS; Tokyo Chemical Industry Co., Ltd.) was used as the silica source.
An aqueous phosphoric acid solution (89 wt %, Tokyo Chemical Industry
Co., Ltd.) was used as the catalyst for hydrolysis. An aqueous ammonia
solution (29 wt %, FUJIFILM Wako Chemical Corporation) was used as
the catalyst for the sol–gel reaction. Moreover, bentonite
in the form of Kunipia-F (Kunimine Industries, Co., Ltd.) was used
as a filler in porous silica.

All chemicals were used as received. Rutile TiO₂ (<5 μm, ≥99.9%), tetramethylammonium bromide (TMAB, ≥98.0%), NaNO₃ (≥99.0%), sodium hydroxide (NaOH, 99.9%), hydrochloric acid (HCl, 37%), methanol (99.5%), and ethanol (99.5%) were purchased from Sigma--Aldrich. HNO₃ solution containing Pd(NO₃)₂ (0.216 M) was purchased from Kojima Chemicals Co., Ltd. Tetraethyl orthosilicate (TEOS, >97.0%) was purchased from Tokyo Chemical Industry.