Heterosupramolecular optical write–read–erase device

Abstract

A covalently linked ruthenium tris(bipyridyl) complex and viologen have been chemisorbed at the surface of the constituent nanocrystals of a transparent nanostructured TiO₂ film supported on conducting glass. This resulting heterosupramolecular assembly, when incorporated as the working electrode in a sealed two-electrode cell, yields a device which can be written to using blue–green light, read using red light and erased by applying a voltage.

References

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20. A transparent nanostructured TiO₂ film (25 mm × 25 mm active area, 4 µm thick, 10 nm diameter nanocrystals) was prepared on fluorine doped SnO₂ glass (30 mm × 30 mm substrate area, 0.5 mm, 8 Ω□^–1, supplied by Glastron).⁷ The linked ruthenium tris(bipyridyl) complex and viologen, RV, was irreversibly chemisorbed at the surface of a constituent nanocrystal of the nanostructured TiO₂ film (5 × 10^–4 mol dm^–3 in methanol, 24 h) to yield the heterosupramolecular assembly TiO₂–RV.^5,6 A conducting glass counter electrode (30 mm × 30 mm substrate area, 0.5 mm, 8 Ω□^–1, supplied by Glastron) was mounted over the working electrode and sealed using a proprietary adhesive supplied by Donnelly Mirrors (Ireland) Ltd. The above adhesive, which contained 80 µm polystyrene beads to maintain a constant separation between the working and counter electrodes, was cured at 130 °C for 1 h. One corner of the device was kept free of adhesive to permit subsequent introduction, by vacuum back filling under argon, of the following electrolyte: acetonitrile–ethanol (73:30, v/v), TBAP (0.10 mol dm^–3) and TEOA (0.05 mol dm^–3). Finally, this opening was sealed using proprietary UV rapid-cure adhesive, again supplied by Donnelly Mirrors (Ireland) Ltd. The device was connected to a Thompson Electrochem Ministat 251, configured to act as a precision voltage source.
21. The device in ref. 20 was written to using the defocused blue–green (488 and 514 nm, 8 mm diameter) output of an argon-ion laser (70 mW cm^–2, 0.5 cm² area, 3 s).
22. The device in ref. 20 was read using the defocused red (633 nm) output of He–Ne laser (5 mW cm^–2, 0.5 cm² area, 3 s).
23. A voltage of + 1.00 V was applied to the device in ref. 20 for 15 s. The working electrode was biased positive with respect to the counter electrode.