Diamond electron emitter using amino-termination
Methods for the photoreduction of molecules are provided, the methods comprising illuminating an amino-terminated diamond surface comprising amino groups covalently bound to the surface of diamond with light comprising a wavelength sufficient to excite an electronic transition defined by the energy band structure of the amino-terminated diamond, thereby inducing the emission of electrons from the amino-terminated diamond surface into a sample comprising molecules to be reduced, wherein the emitted electrons induce the reduction of the molecules to form a reduction product; and collecting the reduction product.
1. A method for the photoreduction of molecules, the method comprising:
(a) illuminating an amino-terminated diamond surface comprising amino groups directly covalently bound to the surface of diamond with light comprising a wavelength sufficient to excite an electronic transition defined by the energy band structure of the amino-terminated diamond, thereby inducing the emission of electrons from the amino-terminated diamond surface into a sample comprising molecules to be reduced, the molecules capable of reduction via a one-electron reduction process or a proton-coupled electron transfer process, wherein the emitted electrons induce the reduction of the molecules to form a reduction product; and
(b) collecting the reduction product.
2. The method of claim 1 , wherein the amino groups are selected from the group consisting of primary amino groups, secondary amino groups, tertiary amino groups, protonated primary amino groups, protonated secondary amino groups, protonated tertiary amino groups, quaternary amino groups, and combinations thereof.
3. The method of claim 1 , wherein the amino groups are selected from
—NR 1 R 2 groups, NR 1 R 2 R 3 + groups, and combinations thereof, wherein R 1 , R 2 and R 3 are independently selected from hydrogen, alkyl and aryl groups.
4. The method of claim 3 , wherein R 1 , R 2 and R 3 are independently selected from hydrogen and alkyl groups.
5. The method of claim 4 , wherein the alkyl groups are linear alkyl groups in which the number of carbons ranges from 2 to 6.
6. The method of claim 1 , wherein the amino groups are selected from —NH 2 , —NH 3 + , —N(CH 3 ) 2 , —N(CH 3 ) 2 H + , —N(CH 3 ) 3 + and combinations thereof.
7. The method of claim 1 , wherein the diamond is p-type diamond.
8. The method of claim 1 , wherein the diamond is not in contact with another photoactive material.
9. The method of claim 8 , wherein the diamond is not in contact with silicon.
10. The method of claim 1 , wherein the diamond is provided as an electrode which is not in contact with another photoactive material.
11. The method of claim 10 , wherein the diamond electrode is substantially free of silicon.
12. The method of claim 1 , wherein substantially all of the reduction product is formed via the electrons excited by the electronic transition.
13. The method of claim 1 , wherein the light comprises a wavelength which substantially matches the bandgap of the diamond.
14. The method of claim 13 , wherein the light comprises a wavelength of about 230 nm or less.
15. The method of claim 13 , wherein the light further comprises a wavelength which is longer than the bandgap of the diamond.
16. The method of claim 15 , wherein the light comprises a wavelength of about 550 nm or less.
17. The method of claim 1 , wherein the light is selected to maximize the photoemission efficiency of the amino-terminated diamond.
18. The method of claim 1 , wherein the amino groups are selected from —NR 1 R 2 groups, —NR 1 R 2 R 3 + groups, and combinations thereof, wherein R 1 , R 2 and R 3 are independently selected from hydrogen, alkyl and aryl groups, with the proviso that the amino groups do not comprise —NH 2 and do not comprise —NH 3 + .
19. The method of claim 18 , wherein R 1 , R 2 and R 3 are independently selected from hydrogen and alkyl groups.
20. The method of claim 19 , wherein the alkyl groups are linear alkyl groups in which the number of carbons ranges from 2 to 6.
21. The method of claim 1 , wherein the amino groups are selected from —N(CH 3 ) 2 , —N(CH 3 ) 2 H + , —N(CH 3 ) 3 + and combinations thereof.
22. The method of claim 1 , wherein the amino-terminated diamond surface is characterized by a surface coverage of oxygen that increases by no more than a factor of 1.25 after continuous illumination by a 450 W HgXe lamp for 12 hours in water saturated with N 2 .
23. A reduction system for the photoreduction of molecules, the reduction system comprising:
(a) a reduction cell comprising amino-terminated diamond comprising amino groups directly covalently bound to the surface of diamond, the reduction cell further comprising a sample comprising the molecules to be reduced, wherein the amino groups are selected from —NR 1 R 2 groups, —NR 1 R 2 R 3 + groups, and combinations thereof, wherein R 1 , R 2 and R 3 are independently selected from hydrogen, alkyl and aryl groups, with the proviso that the amino groups do not comprise —NH 2 and do not comprise —NH 3 + ;
(b) a light source configured to illuminate at least a portion of the reduction cell with light having a wavelength sufficient to excite an electronic transition defined by the energy band structure of the amino-terminated diamond, thereby inducing the emission of electrons from the amino-terminated diamond surface into the sample to induce the reduction of the molecules to form a reduction product; and
(c) a reduction product collection cell configured to collect the reduction product generated in the reduction cell.