Photocatalyst

1. A photocatalyst comprising a composite fiber including at least three n-type crystalline semiconductor materials, wherein

the n-type crystalline semiconductor materials form a heterojunction structure in the composite fiber, and

the n-type crystalline semiconductor materials include bismuth oxide, titanium dioxide, and zinc oxide.

2. The photocatalyst of claim 1 , wherein the n-type crystalline semiconductor materials have band position alignments which allow vectorial displacement of electrons and holes.

3. The photocatalyst of claim 1 , wherein the composite fiber includes a p-type semiconductor material selected from the group consisting of copper (I) oxide, copper (II) oxide, cadmium telluride, and combinations thereof.

4. The photocatalyst of claim 1 , wherein the n-type crystalline semiconductor materials are prepared from a precursor solution including bismuth oxide in a concentration from about 0.1% to about 1%, a precursor solution including zinc oxide in a concentration from about 0.1% to about 1%, and a precursor solution including titanium dioxide in a concentration from about 1% to about 10%.

5. The photocatalyst of claim 1 , wherein the composite fiber has a nanostructure.

6. The photocatalyst of claim 1 , wherein

the photocatalyst is capable of removing a contaminant from a fluid stream, and

the contaminant comprises a pollutant.

7. The photocatalyst of claim 1 , wherein the composite fiber further comprises a polymer coating.

8. The photocatalyst of claim 1 , further comprising a substrate holding the composite fiber.

9. The photocatalyst of claim 8 , wherein the substrate is transparent to light and is gas permeable.

10. The photocatalyst of claim 8 , wherein the substrate is flexible.

11. The photocatalyst of claim 8 , wherein the substrate is a network with a nanostructure.

12. The photocatalyst of claim 11 , wherein the network structure consists of polymeric fibers.

13. The photocatalyst of claim 12 , wherein the polymeric fibers include nylon.

14. The photocatalyst of claim 8 , wherein the composite fiber is selected from the group consisting of nanofibers, truncated nanofibers, nanowires, nanorods, and combinations thereof.

15. A photocatalyst comprising a composite fiber including at least two crystalline semiconductor materials, wherein

the at least two crystalline semiconductor materials form a heterojunction structure in the composite fiber, and

one of the at least two crystalline semiconductor materials is prepared from a precursor solution including bismuth oxide in a concentration from about 0.1% to about 1%, a precursor solution including zinc oxide in a concentration from about 0.1% to about 1%, and a precursor solution including titanium dioxide in a concentration from about 1% to about 10%.

16. The photocatalyst of claim 15 , wherein one of the crystalline semiconductor materials is a p-type semiconductor material selected from the group consisting of copper (I) oxide, copper (II) oxide, cadmium telluride, and combinations thereof.

17. The photocatalyst of claim 15 , wherein the composite fiber further comprises a polymer coating.

18. A photocatalyst comprising a composite fiber including at least two n-type crystalline semiconductor materials, wherein

the at least two n-type crystalline semiconductor materials form a heterojunction structure in the composite fiber,

the at least two n-type crystalline semiconductor materials have band position alignments which allow vectorial displacement of electrons and holes,

one of the at least two n-type semiconductor materials is bismuth oxide, and

the composite fiber includes a p-type semiconductor material selected from the group consisting of copper (I) oxide, copper (II) oxide, cadmium telluride, and combinations thereof.

19. The photocatalyst of claim 18 , wherein the at least two n-type crystalline semiconductor materials include titanium dioxide, zinc oxide, and bismuth oxide.

20. The photocatalyst of claim 19 , wherein the n-type crystalline semiconductor materials are prepared from a precursor solution including bismuth oxide in a concentration from about 0.1% to about 1%, a precursor solution including zinc oxide in a concentration from about 0.1% to about 1%, and a precursor solution including titanium dioxide in a concentration from about 1% to about 10%.

21. The photocatalyst of claim 18 , wherein the composite fiber has a nanostructure.

22. The photocatalyst of claim 18 , wherein

the photocatalyst is capable of removing a contaminant from a fluid stream, and

the contaminant comprises a pollutant.

23. The photocatalyst of claim 18 , wherein the composite fiber further comprises a polymer coating.

24. The photocatalyst of claim 18 , further comprising a substrate holding the composite fiber.

25. The photocatalyst of claim 24 , wherein the substrate is transparent to light and is gas permeable.

26. The photocatalyst of claim 24 , wherein the substrate is flexible.

27. The photocatalyst of claim 24 , wherein the substrate is a network with a nanostructure.

28. The photocatalyst of claim 27 , wherein the network structure consists of polymeric fibers.

29. The photocatalyst of claim 28 , wherein the polymeric fibers include nylon.