HYDROTHERMAL SYNTHESIS OF NANOCUBES OF SILLENITE TYPE COMPOUNDS FOR PHOTOVOLTAIC APPLICATIONS AND SOLAR ENERGY CONVERSION OF CARBON DIOXIDE TO FUELS

• US 20110155971A1
• Filed: 12/14/2010
• Published: 06/30/2011
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: Board of Regents Nevada System of Higher Education (State of Nevada)
• Original Assignee: On Behalf of The University of Nevada Reno, Board of Regents Nevada System of Higher Education (State of Nevada)
• Inventors: Subramanian, Vaidyanathan, Murugesan, Sankaran
• Granted Patent: US 8,709,304 B2
• Time in Patent Office: Days
• US Class Current: 252/582
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 29/00 Compounds of bismuth
• CPC Class Codes: C01P 2002/76 by a space-group or by other symmetry indications
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/38 cube-like
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer

Abstract

The present invention relates to formation of nanocubes of sillenite type compounds, such as bismuth titanate, i.e., Bi₁₂TiO₂₀, nanocubes, via a hydrothermal synthesis process, with the resulting compound(s) having multifunctional properties such as being useful in solar energy conversion, environmental remediation, and/or energy storage, for example. In one embodiment, a hydrothermal method is disclosed that transforms nanoparticles of TiO₂ to bismuth titanate, i.e., Bi₁₂TiO₂₀, nanocubes, optionally loaded with palladium nanoparticles. The method includes reacting titanium dioxide nanotubes with a bismuth salt in an acidic bath at a temperature sufficient and for a time sufficient to form bismuth titanate crystals, which are subsequently annealed to form bismuth titanate nanocubes. After annealing, the bismuth titanate nanocubes may be optionally loaded with nano-sized metal particles, e.g., nanosized palladium particles.

Claims

1. A method of making bismuth titanate nanocubes comprising:

reacting titanium dioxide nanotubes with a bismuth salt in an acidic bath at a temperature sufficient and for a time sufficient to form bismuth titanate crystals having the formula Bi₁₂TiO₂₀, where Bi is bismuth;

Ti is titanium or a fraction thereof between 0 and 1; and

O is oxygen; and

annealing the bismuth titanate crystals to form bismuth titanate nanocubes.

2. The method of claim 1 wherein the acidic bath has a pH of 0 to 2.

3. The method of claim 1 wherein the temperature sufficient is from about 110°

C. to about 175°

C.

4. The method of claim 1 wherein the time sufficient is from about 24 hours to about 72 hours.

5. The method of claim 1 wherein the acidic bath has a bismuth salt concentration of from about 0.1 M to 3 M.

6. The method of claim 1 wherein the bismuth titanate nanocubes define an elongated cube-like structure having a length of about 200 nm to about 1 micron.

7. The method of claim 1 further comprising, after annealing the bismuth titanate crystals to form bismuth titanate nanocubes, loading the bismuth titanate nanocubes with nano-sized metal particles.

8. The method of claim 7 wherein the nanosized metal particles include palladium (Pd) nanosized metal particles.

9. The method of claim 7 wherein the nanosized metal particles range in size from about 10 to about 20 nm.

10. A method of making bismuth titanate nanocubes comprising:

mixing titanium dioxide nanotubes and a bismuth salt in an acidic bath having a pH of 0 to 1;

reacting the titanium dioxide nanotubes and the bismuth salt in the acidic bath at a temperature from about 110°

C. to about 175°

C. and for a time sufficient to form bismuth titanate crystals having the formula Bi₁₂TiO₂₀, where Bi is bismuth;

Ti is titanium or a fraction thereof between 0 and 1; and

O is oxygen; and

annealing the bismuth titanate crystals at a temperature sufficient and for a time sufficient to form bismuth titanate nanocubes.

11. The method of claim 10 wherein the time sufficient for reacting the titanium dioxide nanotubes and the bismuth salt is from about 24 hours to about 72 hours and the time sufficient for annealing the bismuth titanate crystals is from about 1 hour to about 24 hours.

12. The method of claim 10 wherein the temperature sufficient for annealing the bismuth titanate crystals is from about 100°

C. to about 500°

C.

13. The method of claim 10 wherein the acidic bath has a bismuth salt concentration of from about 0.1 M to 3 M.

14. The method of claim 10 wherein the bismuth titanate nanocubes define an elongated cube-like structure having a length of about 200 nm to about 1 micron.

15. The method of claim 10 further comprising, after annealing the bismuth titanate crystals to form bismuth titanate nanocubes, loading the bismuth titanate nanocubes with nano-sized metal particles.

16. The method of claim 10 wherein the nanosized metal particles include palladium (Pd) nanosized metal particles.

17. The method of claim 10 further comprising, after annealing the bismuth titanate crystals to form bismuth titanate nanocubes, placing the bismuth titanate nanocubes in a metal salt solution and subjecting the mixture to ultrasonication for a time sufficient to load the bismuth titanate nanocubes with the metal salt;

and

annealing the loaded bismuth titanate nanocubes to reduce the metal salt thereby forming bismuth titanate nanocubes that are loaded with nano-sized metal particles.

18. The method of claim 17 wherein the metal salt solution is a palladium salt solution and the nanosized metal particles are palladium (Pd) nanosized metal particles.

19. The method of claim 18 wherein the nanoparticles range in size from about 10 to about 20 nm.

20. A method of making nanocubes of a sillenite type compound comprising:

reacting oxide nanotubes with a salt in an acidic bath at a temperature sufficient and for a time sufficient to form crystals having the general formula (I) A₁₂RO₂₀, where A is bismuth, strontium, tin, nickel, aluminum, titanium, iron, silicon, barium, manganese, zinc, cadmium, calcium, copper, cobalt, vanadium, gallium, yittrium, lanthanum, cerium, hafnium, niobium, europium, samarium, or gadolinium, or a fraction thereof between 0 and 1;

R is lead, nickel, aluminum, titanium , iron, silicon, barium, manganese, zinc, cadmium, calcium, copper, gallium, or vanadium, or a fraction thereof between 0 and 1; and

O is oxygen; and

annealing the crystals to form nanocubes of the general formula (I).