Anatase type TiO2 nanorods and their preparation method

• US 7,887,780 B2
• Filed: 05/26/2009
• Issued: 02/15/2011
• Est. Priority Date: 05/26/2008
• Status: Active Grant

• Current Assignee: Korea Research Institute of Chemical Technology
• Original Assignee: Korea Research Institute of Chemical Technology
• Inventors: Baek, In Chan, Chang, Jeong Ah, Seok, Sang Il
• Primary Examiner(s): Silverman; Stanley
• Assistant Examiner(s): Zimmer; Anthony J
• Application Number:
  US12/471,854
• Publication Number:
  US 20090291044A1
• Time in Patent Office: 630 Days
• Field of Search: 423610-616, 977/762, 977/773, 977/811
• US Class Current: 423/612
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 23/04 Oxides; Hydroxides
• CPC Class Codes: C01G 23/0536 by hydrolysing chloride-containing salts
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/16 Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
• CPC Class Codes: H01G 9/2031 comprising titanium oxide, e.g. TiO2 H01G9/2036 takes precedence
• CPC Class Codes: H01L 31/0352 characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
• CPC Class Codes: Y02E 10/542 Dye sensitized solar cells
• CPC Class Codes: Y10S 977/762 Nanowire or quantum wire, i.e. axially elongated structure having two dimensions of 100 nm or less

Abstract

Provided is a process which includes slowly adding dropwise chilled distilled water to titanium tetrachloride to prepare solution of titanium oxychloride; adding basic solution thereto to maintain pH of the titanium oxychloride solution within a range from 3.5 to 4, thereby providing a suspension of titanium oxyhydroxide precipitate; adding basic solution thereto to adjust the suspension of titanium oxyhydroxide precipitate to be weakly basic, and heating and stirring the mixture at 80 to 100° C.; isolating and collecting dihydroxy-oxotitanium from the heated and stirred suspension of titanium oxyhydroxide precipitate, and washing it with weakly basic aqueous solution; and adding distilled water and 20 to 500 folds of hydrogen peroxide on the basis of 1 mole of Ti⁴⁺ in titanium oxyhydroxide to the washed titanium oxyhydroxide, and heat-treating the mixture at a temperature of 90 to 100° C. for 1 to 7 days to prepare titania nanorods having the mean length of 100 nm to 300 nm.

Claims

1. A process for preparing titania nanorods for dye sensitized or quantum-dot nanoparticle sensitized solar cells, comprising:

(a) slowly adding dropwise chilled distilled water to titanium tetrachloride (TiCl₄) to prepare a solution of titanium oxychloride (TiOCl₂);

(b) adding basic solution the solution of titanium oxychloride to maintain pH of the titanium oxychloride solution within a range from 3.5 to 4, thereby providing a suspension of titanium oxyhydroxide (TiO(OH)₂) precipitate;

(c) adding basic solution the suspension of titanium oxyhydroxide precipitate to adjust the suspension of titanium oxyhydroxide precipitate to be weakly basic, and heating and stirring the mixture at 80 to 100°

C.;

(d) isolating and collecting titanium oxyhydroxide from the heated and stirred suspension of titanium oxyhydroxide precipitate, and washing the collected titanium oxyhydroxide with a weakly basic aqueous solution; and

(e) adding distilled water and 20 to 500 fold of hydrogen peroxide (H₂O₂) on the basis of 1 mole of Ti⁴⁺ in the titanium oxyhydroxide to the washed titanium oxyhydroxide to form a mixture, and heat-treating the mixture at a temperature of 90 to 100°

C. for 1 to 7 days to prepare titania nanorods having a mean length of 100 nm to 300 nm.

2. The process of claim 1, wherein the molar concentration of the Ti⁴⁺ ion of the titanium oxychloride solution in (a) is from 2 to 3 M, the process further comprising adjusting the Ti⁴⁺ ion concentration of the titanium oxychloride solution to 0.3 to 0.8 M by adding distilled water after step (a).

3. The process of claim 2, wherein the weakly basic suspension of titanium oxyhydroxide precipitate of (c) has pH of 8 to 10.

4. The process of claim 1, wherein the weakly basic aqueous solution of (d) is aqueous ammonia solution (NH₄OH) of pH 8 to 10, and the washing is repeated 2˜

4 times.

5. The process of claim 1, wherein the basic solution of (b) and (c) is ammonia solution (NH₄OH).

6. The process of claim 2, wherein stage (e) is characterized in that distilled water is added in an amount of 100 to 400 fold on the basis of Ti⁴⁺ molar concentration of the washed titanium oxyhydroxide, and the mixture is stirred, and then 20 to 500 fold of hydrogen peroxide is added to the mixture, and the resultant mixture is stirred again and heat-treated at a temperature of 90 to 100°

C. for 1 to 7 days.

7. The process of claim 2, wherein the aspect ratio of titania nanorods from (e) is from 10 to 30.

8. The process of claim 2, wherein the titania nanorods from (e) have anatase structure.