Titanium 4 tetraisopropoxide

Zn(CH₃COO)₂·2H₂O, 2-methylimidazole (2-MeIm), Co(NO₃)₂·6H₂O, Cu(NO₃)₂·3H₂O, ethyl cellulose, terpineol (C₁₀H₁₈O), acetone, acetonitrile, ethanol, 2-propanol, I₂, LiI, SiO₂, HCl, 4-tert-butyl pyridine, titanium(iv) tetra-isopropoxide (Ti[OCH(CH₃)₂]₄), H₂PtCl₆–6H₂O, and N719 dye were provided by the Sigma-Aldrich and Merck Companies and used exactly as they were delivered. Solaronix Company provided the Surlyn spacer and conductive FTO (80% transparency in visible region, ∼30 Ω cm⁻²) coated glasses.

Nickel (II) nitrate hexahydrate (Ni(NO₃)₂ • 6H₂O), trioctylphosphine (TOP, 97%), titanium (IV) tetraisopropoxide (TTIP, >98%), 2-methoxyethanol (CH₃OCH₂CH₂OH, ≥99.5%), lithium perchlorate (LiClO₄, ≥98.0%), ethanol (EtOH, 99.5%) and isopropyl alcohol (IPA, 99.5%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Iodine (I₂, synthetic grade), lithium iodide (LiI, synthetic grade), and poly(ethylene glycol) (PEG, MW~20,000) were supplied by Merck (Rahway, NJ, USA). Acetone ( $\ge$ 99%), 4-tert-butylpyridine (tBP, 96%), and tert-butyl alcohol (tBA, 96%) were acquired from Acros, and 3-methoxypropionitrile (MPN, 99%) was bought from Fluka (Buchs, Switzerland). Transparent titanium dioxide (TiO₂) paste (TL paste, Ti-nanoxide HT/SP, 13 nm), cis-diisothiocyanato-bis(2,2′-bipyridyl-4,4′-dicarboxylato) ruthenium (II) bis(tetrabutylammonium) (N719 dye), and 1,2-dimethyl-3-propylimidazolium iodide (DMPII) were obtained from Solaronix (S.A., Aubonne, Switzerland). Commercial light-scattering TiO₂ particles (ST-41 with 200 nm) were procured from Ishihara Sangyo, Ltd. (Nishi-ku, Osaka, Japan). Nitric acid (HNO₃, 65% solution in water), acetonitrile (ACN, 99.99%) was received from J. T. Baker. Polyester tape (1350F-1, 63 μm) was from the 3M Company (St. Paul, MN, USA).

All the chemicals employed were reagent grade or higher in quality. OFL, zeolite Y in sodium form, sepiolite powder, titanium (IV) tetraisopropoxide (97% v/v), and 2-propanol (99.5% v/v) were purchased from Sigma–Aldrich (Milano, Italy). High Performance Liquid Chromatography (HPLC) gradient grade acetonitrile (ACN) was purchased by VWR International (Milano, Italy), H₃PO₄ (85% w/w) and ammonia solution (30% w/w) were purchased by Carlo Erba Reagents (Cornaredo, Milano, Italy). Aqueous OFL solutions were prepared and stored in the dark at 4 °C before use.