Redox-switchable materials

• US 20050227071A1
• Filed: 12/30/2002
• Published: 10/13/2005
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Board of Regents Nevada System of Higher Education (State of Nevada)
• Original Assignee: Board of Regents Nevada System of Higher Education (State of Nevada)
• Inventors: Gillett, Stephen L., Bell, Thomas W., Muraoka, Masahiro
• Granted Patent: US 7,435,362 B2
• Time in Patent Office: Days
• US Class Current: 428/403
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: H01M 14/005 Photoelectrochemical storage cells light sensitive devices H01G9/20, semiconductors sensitive to light H01L31/00
• CPC Class Codes: H10K 10/701 Organic molecular electronic devices
• CPC Class Codes: H10K 85/331 Metal complexes comprising an iron-series metal, e.g. Fe, Co, Ni
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

The invention relates to redox-switchable material comprising a redox-active moiety adsorbed, bonded or both, to a semiconductor material. Among the preferred redox-active moieties disclosed herein are ferrocenes, acridines, and quinones though any such moiety may be employed. The redox-switchable material of this invention may be used to selectively remove one or more selected solutes from an aqueous solution wherein adsorption/complexation of the solute is influenced by the oxidation state of the redox-active moiety. In an alternative embodiment, inclusion moieties that are covalently bound to the redox-active moiety are employed to achieve selective complexation of the desired solute. Other possible applications of the disclosed materials are photoerasable writing media, electrochromic or photochromic materials, catalysis, and solar energy storage.

Claims

1. A redox-switchable material which comprises:

a solid semiconductor; and

a redox-active moiety adsorbed, bonded or both to the surface of the solid semiconductor.

2. The material of claim 1 wherein the redox-active moiety also comprises a selective complexing moiety.

3. The material of claim 2 wherein the selective complexing moiety is a cryptand.

4. The material of claim 3 wherein the selective complexing moiety is a crown ether.

5. The material of any of claims 1 wherein the semiconductor is hydrophobic.

6. The material of claims 5 wherein the redox-active moiety is covalently bonded to the surface of the hydrophobic semiconductor.

7. The material of claim 6 wherein the redox-active moiety is covalently bonded to the surface of the hydrophobic semiconductor through a linker group.

8. The material of claim 7 wherein the linker group is a hydrocarbon linker group.

9. The material of any of claims 1 wherein the redox-active moiety comprises a ferrocene.

10. The material of any of claims 1 wherein the redox-active moiety comprises an acridine.

11. The material of any of claims 1 wherein the redox-active material comprises a quinone.

12. The material of any of claims 1 wherein the hydrophobic solid semiconductor comprises particles of semiconductor coated with surfactant

13. The material of claims 1 wherein the hydrophobic solid semiconductor comprises particles of semiconductor covalently bonded to hydrophobic moieties.

14. A reversible redox system which comprises a redox-switchable material of any of claims 1 in contact with a source of electrons.

15. The reversible redox system of claim 14 also in contact with an electron acceptor.

16. The reversible redox system of claim 14 further comprising a light source to irradiate the semiconductor to generate electron-hole pairs.

17. The reversible system of claim 14 in contact with an aqueous solution containing an oxidizing agent wherein the redox-active moiety in its oxidized state can be photoreduced upon irradiation of the semiconductor and in its reduced state can be oxidized by the oxidizing agent.

18. The system of claim 17 wherein the oxidizing agent is oxygen.

19. The system of claim 18 wherein the oxygen is present during photoreduction of the redox-active moiety.

20. A method for extraction of a selected solute from an aqueous solution which comprises the steps of:

(a) contacting the redox-switchable material of any of claims 1 with the aqueous solution, and thereafter

(b) irradiating the semiconductor particles thereof to photoreduce the redox-active moiety of the material wherein solute is selectively adsorbed or complexed to the semiconductor on irradiation and wherein solute is thereby extracted in whole or in part from the aqueous solution.

21. The method of claim 20 further comprising the steps of:

(c) separating the irradiated semiconductor material and adsorbed solute from the aqueous solution, and thereafter

(d) contacting the semiconductor material and adsorbed or complexed solute with an oxidizing agent to oxidize the redox-active moiety and release adsorbed or complexed solute from the semiconductor material.

22. The method of claim 19 further comprising repeating steps a, b, and c as many times as needed to extract a desired amount of solute from the aqueous solution.

23. The method of claim 19 wherein released solute is collected further comprising repeating steps a, b, c and d as many times as needed to collect a desired amount of solute from the aqueous solution.

24. A photoerasable writing media comprising the redox-switchable material of any of claims 1.

25. A electrochromic or photochromic material which comprises the redox-switchable material of any of claims 1.

26. A catalyst which comprises the redox-switchable material of any of claims 1.

27. A method for storage of light energy which comprises the step of employing a redox-switchable material which comprises a redox-active moiety adsorbed, bonded or both to the surface of a photoactive solid semiconductor to mediate or catalyze a chemical reaction.

28. The method of claim 27 wherein the redox switchable moiety is selected from the group consisting of a cryptand and a crown ether.