Methods of making non-covalently bonded carbon-titania nanocomposite thin films and applications of the same

1. A method of making non-covalently bonded carbon-titania nanocomposite thin films, comprising:

forming a carbon-based ink;

forming a titania (TiO 2 ) solution;

blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films,

wherein the carbon-based ink comprises a concentrated solvent-exfoliated graphene (SEG) ink; and

wherein the forming of the concentrated SEG ink comprises:

adding a first amount of natural graphite to a second amount of N,N-dimethylforamide (DMF) to form a first graphite solution;

sonicating the first graphite solution at a first frequency for a second period of time;

centrifuging the sonicated first graphite solution for a third period of time at a first rotation speed to obtain a SEG supernatant; and

disposing the SEG supernatant in ethyl-cellulose (EC) and terpineol, and evaporating the DMF in the SEG solution to form the concentrated SEG ink.

2. The method of claim 1 , wherein the first temperature is about 350-450° C., and the first period of time is about 20-45 minutes.

3. The method of claim 1 , wherein the first amount is about 2-3 g, the second amount is about 40-60 ml, the second period of time is about 2.5-3.5 hours, the first frequency is about 30-50 kHz, the third period of time is about 3-6 hours, and the first rotation speed is about 6000-9000 rpm.

4. The method of claim 1 , wherein the titania solution comprises a titanium dioxide P25 ink.

5. The method of claim 1 , wherein the titania solution comprises a titania nanosheet (TiNS) ink.

6. The method of claim 5 , wherein the forming of the TiNS ink comprises:

mixing a third amount of titanium butoxide with a fourth amount of hydrofluoric acid for a seventh period of time to form a mixed solution;

heating the mixed solution at a second temperature for an eighth period of time under hydrothermal conditions; and

rinsing the heated mixed solution to obtain the TiNS ink.

7. The method of claim 6 , wherein the third amount is about 15-25 ml, the fourth amount is about 2.5-3.2 ml, the seventh period of time is about 20-45 minutes, the second temperature is about 175-225° C., and the eighth period of time is about 20-28 hours.

8. A method of making non-covalently bonded carbon-titania nanocomposite thin films, comprising:

forming a carbon-based ink;

forming a titania (TiO 2 ) solution;

blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films,

wherein the carbon-based ink comprises a concentrated solvent-exfoliated graphene (SEG) ink; and

wherein the forming of the concentrated SEG ink comprises:

adding natural graphite to an ethyl-cellulose (EC)-ethanol solution to form a second graphite solution;

sonicating the second graphite solution at a second frequency for a fourth period of time;

centrifuging the sonicated second graphite solution for a fifth period of time at a second rotation speed to obtain a SEG supernatant; and

disposing the SEG supernatant in terpineol to perform solvent exchange and to form the concentrated SEG ink.

9. The method of claim 8 , wherein the fourth period of time is about 2.5-3.5 hours, the first frequency is about 30-50 kHz, the fifth period of time is about 3-6 hours, and the second rotation speed is about 6000-9000 rpm.

10. A method of making non-covalently bonded carbon-titania nanocomposite thin films, comprising:

forming a carbon-based ink;

forming a titania (TiO 2 ) solution;

blade-coating a mechanical mixture of the carbon-based ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a first temperature for a first period of time to obtain the carbon-based titania nanocomposite thin films,

wherein the carbon-based ink comprises a concentrated single walled carbon nanotube (SWCNT) ink; and

wherein the forming of the concentrated SWCNT ink comprises:

dispersing SWCNT in an ethyl-cellulose (EC)-ethanol solution to form a SWCNT solution;

sonicating the SWCNT solution for a sixth period of time; and

disposing the sonicated SWCNT solution in terpineol to perform solvent exchange and to obtain the concentrated SWCNT ink.

11. The method of claim 10 , wherein the sixth period of time is about 45-75 minutes.

12. A method of making solvent-exfoliated graphene titania (SEG-TiO2) nanocomposite thin films, comprising:

adding a first amount of natural graphite to a second amount of N,N-dimethylforamide (DMF) to form a graphite solution;

sonicating the graphite solution at a predetermined frequency for a first period of time;

centrifuging the sonicated graphite solution for a second period of time at a predetermined speed to obtain a SEG supernatant;

disposing the SEG supernatant in ethyl-cellulose (EC) and terpineol, and evaporating the DMF in the SEG solution to form a concentrated SEG ink;

forming a titania solution;

blade-coating a mechanical mixture of the concentrated SEG ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a predetermined temperature for a third period of time to obtain the SEG-TiO 2 nanocomposite thin films.

13. The method of claim 12 , wherein the first amount is about 2-3 g, and the second amount is about 40-60 ml.

14. The method of claim 12 , wherein the first period of time is about 2.5-3.5 hours; the second period of time is about 3-6 hours; the third period of time is about 20-45 minutes; the predetermined frequency is about 30-50 kHz; a predetermined speed is about 6000-9000 rpm; and the predetermined temperature is about 350-450° C.

15. The method of claim 12 , wherein the titania solution comprises a titanium dioxide P25 ink.

16. The method of claim 12 , wherein the titania solution comprises a titania nanosheet (TiNS) ink.

17. The method of claim 16 , wherein the forming of the TiNS ink comprises:

mixing a third amount of titanium butoxide with a fourth amount of hydrofluoric acid for about 20-45 minutes to form a mixed solution;

heating the mixed solution at about 175-225° C. for about 20-28 hours under hydrothermal conditions; and

rinsing the heated mixed solution to obtain the TiNS ink.

18. The method of claim 17 , wherein the third amount is about 15-25 ml, and the fourth amount is about 2.5-3.2 ml.

19. A method of making solvent-exfoliated graphene titania (SEG-TiO 2 ) nanocomposite thin films, comprising:

adding a first amount of natural graphite to a second amount of an ethyl-cellulose (EC)-ethanol solution to form a graphite solution;

sonicating the graphite solution at a predetermined frequency for a first period of time;

centrifuging the sonicated graphite solution for a second period of time at a predetermined speed to obtain a SEG supernatant;

disposing the SEG supernatant in terpineol to perform solvent exchange and to form the concentrated SEG ink;

forming a titania solution;

blade-coating a mechanical mixture of the concentrated SEG ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a predetermined temperature for a third period of time to obtain the SEG-TiO 2 nanocomposite thin films.

20. The method of claim 19 , wherein the first period of time is about 2.5-3.5 hours; the second period of time is about 3-6 hours; the third period of time is about 20-45 minutes; the predetermined frequency is about 30-50 kHz; the predetermined speed is about 6000-9000 rpm; and the predetermined temperature is about 350-450° C.

21. The method of claim 19 , wherein the titania solution comprises a titanium dioxide P25 ink.

22. The method of claim 19 , wherein the titania solution comprises a titania nanosheet (TiNS) ink.

23. The method of claim 22 , wherein the forming of the TiNS ink comprises:

mixing a third amount of titanium butoxide with a fourth amount of hydrofluoric acid for about 20-45 minutes to form a mixed solution;

heating the mixed solution at about 175-225° C. for about 20-28 hours under hydrothermal conditions; and

rinsing the heated mixed solution to obtain the TiNS ink.

24. The method of claim 23 , wherein the third amount is about 15-25 ml, and the fourth amount is about 2.5-3.2 ml.

25. A method of making single walled carbon nanotube titania (SWCNT-TiO 2 ) nanocomposite thin films, comprising:

dispersing single walled carbon nanotubes (SWCNTs) in an ethyl-cellulose (EC)-ethanol solution to form a SWCNT solution;

sonicating the SWCNT solution for a first period of time;

disposing the sonicated SWCNT solution in terpineol to perform solvent exchange and to obtain the concentrated SWCNT ink;

forming a titania (TiO 2 ) solution;

blade-coating a mechanical mixture of the concentrated SWCNT ink and the titania solution onto a substrate; and

annealing the blade-coated substrate at a predetermined temperature for a second period of time to obtain the SWCNT-TiO 2 nanocomposite thin films.

26. The method of claim 25 , wherein the first period of time is about 45-75 minutes; the second period of time is about 20-45 minutes; and the predetermined temperature is about 350-450° C.

27. The method of claim 25 , wherein the titania solution comprises a titania nanosheet (TiNS) ink.

28. The method of claim 27 , wherein the forming of the TiNS ink comprises:

mixing a first amount of titanium butoxide with a second amount of hydrofluoric acid for about 20-45 minutes to form a mixed solution;

heating the mixed solution at about 175-225° C. for about 20-28 hours under hydrothermal conditions; and

rinsing the heated mixed solution to obtain the TiNS ink.

29. The method of claim 28 , wherein the first amount is about 15-25 ml, and the second amount is about 2.5-3.2 ml.