LINEAR TITANIUM-OXIDE POLYMER, TITANIUM DIOXIDE COATING, PHOTOCATALYTIC COATING AND PREPARATION METHOD THEREFOR

Abstract

A linear titanium-oxide polymer, a nano-TiO.sub.2 coating structure, a glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure and methods for preparing the same are disclosed. The linear titanium-oxide polymer has the following structural formula:

##STR00001##

The prepared materials can be used for photocatalysis, deodorizing filters, antibacterial filters, indoor air purifying filters, transport vehicle purifying filters, and household appliance purifiers and so on.

Claims

1. A method for preparing a linear titanium-oxide polymer, comprising steps of: 1) adding a titanate to a reaction vessel, and adding a chelating agent to the titanate at 50-90° C. to obtain a first mixture, heating and stirring the first mixture for 0.5-1.5 h; 2) adding a mixed solution of water and alcohol dropwise to the first mixture at 50-90° C. to obtain a second mixture, and stirring the second mixture at 80-110° C. for 1.5-4 h after an addition of the mixed solution is completed, cooling the second mixture, then removing a solvent under a reduced pressure to obtain the linear titanium-oxide polymer; wherein the linear titanium-oxide polymer comprises the following structural formula: ##STR00007## the R.sup.1 is selected from the group consisting of —C.sub.2H.sub.5, —C.sub.3H.sub.7, —C.sub.4H.sub.9, and —C.sub.5H.sub.11; the R.sup.2 is OR′ or a complexing group selected from the group consisting of CH.sub.3COCHCOCH.sub.3 and CH.sub.3COCHCOOC.sub.2H.sub.5, at least 50% of the R.sup.2 are the complexing group by a total number of the R.sup.2; a number average molecular weight (Mn) of the linear titanium-oxide polymer is 2000-3000 when determined by a vapor-pressure osmometry; and a solvent-free pure titanium-oxide polymer has a softening point in a range of 90-127° C. when determined by a ring-and-ball method.

2. The method for preparing the linear titanium-oxide polymer of claim 1, wherein a molar ratio of the titanate, the chelating agent and the water is 1:(0.5-1.4):(0.8-1.3).

3. The method for preparing the linear titanium-oxide polymer of claim 2, wherein a molar ratio of the water to the alcohol in the mixed solution of water and alcohol is 1:(3-20).

4. The method for preparing the linear titanium-oxide polymer of claim 2, wherein in the step 1), the titanate has a structure of Ti(OR.sup.1).sub.4, wherein the R.sup.1 of the Ti(OR.sup.1).sub.4 is selected from the group consisting of —C.sub.2H.sub.5, —C.sub.3H.sub.7, —C.sub.4H.sub.9, and —C.sub.5H.sub.11.

5. A method for preparing a nano-TiO.sub.2 coating structure based on claim 1, comprising steps of: 1) dissolving the linear titanium-oxide polymer in a solvent to prepare a solution, wherein a concentration of the solution is 0.3-2 wt % by titanium; 2) pretreating a surface of a substrate to be coated optionally; 3) applying the solution uniformly on the substrate to obtain a solution-coated substrate, drying and sintering the solution-coated substrate to obtain a nano-TiO.sub.2 coating supported on the substrate; the nano-TiO.sub.2 coating structure comprises the substrate, and the nano-TiO.sub.2 coating supported on the surface of the substrate; wherein the nano-TiO.sub.2 coating comprises a plurality of nano-TiO.sub.2 particles, an average particle size of the plurality of nano-TiO.sub.2 particles is 10-50 nm; and a loading capacity of the nano-TiO.sub.2 coating structure is 1.0-100 μg of nano-TiO.sub.2 coating per cubic centimeter of the substrate.

6. The method for preparing the nano-TiO.sub.2 coating structure of claim 5, wherein the linear titanium-oxide polymer is prepared by a method comprising steps of: a) adding a titanate to a reaction vessel, and adding a chelating agent to the titanate at 50-90° C. to obtain a first mixture, heating and stirring the first mixture for 0.5-5.0 h; b) adding a mixed solution of water and alcohol dropwise to the first mixture at 50-90° C. to obtain a second mixture, and stirring the second mixture at 80-110° C. for 1.5-6 h after an addition of the mixed solution is completed, cooling the second mixture, and then removing a solvent under a reduced pressure to obtain the linear titanium-oxide polymer.

7. The method for preparing the nano-TiO.sub.2 coating structure of claim 5, wherein the substrate comprises silicon-based materials, metals, glass, ceramics, and adsorbent materials, or a combination of the silicon-based materials, the metals, the glass, the ceramics, and the adsorbent materials.

8. The method for preparing the nano-TiO.sub.2 coating structure of claim 7, wherein the metals comprise steel plates, aluminum plates, titanium plates, copper plates, zinc plates, foamed nickels, foamed aluminums and aluminum honeycombs; the glass comprises glass sheets, glass fiber cloths, hollow glass microspheres, glass beads, and glass springs; the ceramics comprise hollow ceramic microspheres, ceramic tiles, ceramic plates and honeycomb ceramics; and the adsorbent materials comprise silicon oxide, silica gels, activated carbons, zeolites, and molecular sieves.

9. The method for preparing the nano-TiO.sub.2 coating structure of claim 5, wherein the nano-TiO.sub.2 coating described in the step 3) is obtained by sintering the solution-coated substrate in air at 450-550° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0103] FIG. 1-1 shows the infrared spectrum of the linear titanium-oxide polymer according to one embodiment of the present invention.

[0104] FIG. 1-2 shows the H-NMR spectrum of the linear titanium-oxide polymer according to one embodiment of the present invention.

[0105] FIG. 1-3 shows the XRD curve of the linear titanium-oxide polymer which is subjected to heat treatment in air at 450° C. for 3 h according to one embodiment of the present invention.

[0106] FIG. 2-1 shows the infrared spectrum of the linear titanium-oxide polymer according to one embodiment of the present invention.

[0107] FIG. 2-2 shows the H-NMR spectrum of the linear titanium-oxide polymer according to one embodiment of the present invention.

[0108] FIG. 2-3 shows the XRD curve of the linear titanium-oxide polymer which is subjected to heat treatment in air at 500° C. for 2 h according to one embodiment of the present invention.

[0109] FIG. 3 shows the XRD curve of the linear titanium-oxide polymer which is subjected to heat treatment in air at 400° C. for 2 h according to one embodiment of the present invention.

[0110] FIG. 4 shows the XRD curve of the linear titanium-oxide polymer which is subjected to heat treatment in air at 550° C. for 1.5 h according to one embodiment of the present invention.

[0111] FIG. 5-1 shows the scanning electron micrograph of the coating structure taken from an angle according to one embodiment of the present invention.

[0112] FIG. 5-2 shows the scanning electron micrograph of the coating structure taken from another angle according to one embodiment of the present invention.

[0113] FIG. 6 shows the scanning electron micrograph of the coating structure according to another embodiment of the present invention.

[0114] FIG. 7 shows the scanning electron micrograph of the coating structure according to still another embodiment of the present invention.

[0115] FIG. 8 shows the scanning electron micrograph of the coating structure according to yet another embodiment of the present invention.

[0116] FIG. 9-1, FIG. 9.2 and FIG. 9-3 show the scanning electron micrographs of the glass fiber mat-nano-TiO.sub.2 coating structure under different magnifications according to one embodiment of the present invention; wherein the loading capacity of the TiO.sub.2 is 10.5 wt % by the weight of the glass fiber mat.

[0117] FIG. 10 shows a flowchart of a method to prepare linear titanium-oxide polymer, titanium dioxide coating, and photocatalytic coating according to yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0118] The technical solutions of the present invention are further described below with reference to the specific examples, but the present invention is not limited thereto.

[0119] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. In the event of any contradiction, the definitions in this specification shall prevail.

Unless otherwise stated, all percentages, parts, ratios and the like are expressed by weight.

Example 1

[0120] The method for preparing a titanium-oxide polymer provided in this example was conducted according to the following steps: m1) 1 mol tetraisobutyl titanate was added to a reaction vessel, followed by 0.8 mol acetylacetone; then the mixture was heated and stirred at 50° C. for 1 h; m2) the temperature was adjusted to 80° C., and a mixed solution of 0.8 mol water and 2.5 mol isobutanol was added dropwise; the mixture was heated and stirred at 90° C. for 2 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain a yellow titanium-oxide polymer.

[0121] The softening point was 92° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2750 as measured by the vapor-pressure osmometry.

[0122] The obtained yellow titanium-oxide polymer (1-2 mg) and pure KBr (200 mg) were ground finely and uniformly, placed in a mold, and pressed into a transparent sheet on a tableting machine for IR spectrum characterization, as shown in FIG. 1-1. In FIG. 1-1, the peaks at 2959 cm.sup.−1, 2922 cm.sup.−1 and 2872 cm.sup.−1 are C—H stretching vibration peaks; and the peaks at 1592 cm.sup.−1 and 1531 cm.sup.−1 belong to the absorption peaks of C═O (keto form) and C═C (enol form) at 425 cm.sup.−1 and 543 cm.sup.−1 in the acetylacetone ligand, proving the presence of Ti—O bonds in the structure of the polymer.

[0123] The obtained yellow titanium-oxide polymer was dissolved in deuterated chloroform for NMR characterization, and the results are shown in FIG. 1-2.

[0124] The obtained yellow titanium-oxide polymer was treated in air at 450° C. for 2 h to obtain a TiO.sub.2 photocatalyst, part of which was used for XRD test and characterization, as shown in FIG. 1-3. It can be seen from the figure that the TiO.sub.2 obtained after cracking of the titanium-oxide polymer is the anatase TiO.sub.2.

[0125] 50 mg of the TiO.sub.2 photocatalyst obtained by treatment in air at 450° C. for 2 h was weighed and added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 82.8% after illumination by a 500W mercury lamp for 2.5 h. It can be seen that the TiO.sub.2 has a significant photocatalytic performance.

Example 2

[0126] The method for preparing a titanium-oxide polymer provided in this example was conducted according to the following steps: m1) 1 mol tetrabutyl titanate was added to a reaction vessel, followed by 0.5 mol acetylacetone, then the mixture was heated and stirred at 90° C. for 1.5 h; m2) the temperature was adjusted to 70° C., and a mixed solution of 1.2 mol water and 6 mol n-butanol was added dropwise; the mixture was stirred at 100° C. for 2.5 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain the titanium-oxide polymer.

[0127] The softening point was 98° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2930 as measured by the vapor-pressure osmometry.

The obtained titanium-oxide polymer (1-2 mg) and pure KBr (200 mg) were ground finely and uniformly, placed in a mold, and pressed into a transparent sheet on a tableting machine for IR spectrum characterization, as shown in FIG. 2-1.

[0128] The obtained titanium-oxide polymer was dissolved in deuterated chloroform for NMR characterization, and the results are shown in FIG. 2-2.

[0129] The obtained titanium-oxide polymer was treated in air at 500° C. for 1 h to obtain a TiO.sub.2 catalyst, part of which was used for XRD test and characterization, as shown in FIG. 2-3.

[0130] 50 mg of the catalyst obtained by treatment in air at 500° C. for 1 h was weighed and added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 79.3% after illumination by a 500W mercury lamp for 2.5 h. It can be seen that the TiO.sub.2 has a significantly photocatalytic performance.

Example 3

[0131] The method for preparing a titanium-oxide polymer provided in this example was conducted according to the following steps: m1) 1 mol tetrapropyl titanate was added to a reaction vessel, followed by 1.4 mol ethyl acetoacetate; then the mixture was heated and stirred at 60° C. for 1 h; 2) the temperature was adjusted to 80° C., and a mixed solution of 0.8 mol water and 2.5 mol n-propanol was added dropwise; the mixture was continued to be heated and stirred at 80° C. for 3 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain the titanium-oxide polymer.

[0132] The softening point was 107° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2200 as measured by the vapor-pressure osmometry.

[0133] The obtained titanium-oxide polymer was treated in air at 400° C. for 1 h to obtain a TiO.sub.2 catalyst, and part of the powder was used for XRD test, as shown in FIG. 3.

[0134] 50 mg of the TiO.sub.2 catalyst obtained by treatment in air at 400° C. for 1 h was weighed and added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 60.2% after illumination by a 500W mercury lamp for 2.5 h. It can be seen that the TiO.sub.2 has a significantly photocatalytic performance.

Example 4

[0135] The method for preparing a titanium-oxide polymer provided in this example was conducted according to the following steps: 1) 1 mol tetraethyl titanate was added to a reaction vessel, followed by 0.8 mol acetylacetone, then the mixture was heated and stirred at 50° C. for 1 h; 2) the temperature was adjusted to 60° C., and a mixed solution of 0.8 mol water and 2.5 mol ethanol was added dropwise; the mixture was continued to be heated and stirred at 60° C. for 4 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain the titanium-oxide polymer.

[0136] The softening point was 115° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2050 as measured by the vapor-pressure osmometry.

[0137] The obtained titanium-oxide polymer was subjected to heat treatment in air at 550° C. for 2 h to obtain a TiO.sub.2 photocatalyst, and part of the powder was used for XRD test, as shown in FIG. 4. It can be seen from the figure that the TiO.sub.2 of rutile phase appeared.

[0138] 50 mg of the TiO.sub.2 catalyst obtained by treatment in air at 550° C. for 1 h was weighed and added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 59.2% after illumination by a 500W mercury lamp for 2.5 h; this is due to the appearance of the TiO.sub.2 of rutile phase, which leads to a reduced degradation rate.

Example 5: Preparation of a Linear Titanium-Oxide Polymer

[0139] 1 mol tetraisobutyl titanate was added to a reaction vessel, and the temperature was adjusted to 50° C.; then 0.8 mol acetylacetone was added, and the mixture was heated and stirred at 50° C. for 1 h; 2) the temperature was adjusted to 80° C., and a mixed solution of 0.8 mol water and 2.5 mol isobutanol was added dropwise; the mixture was continued to be heated and stirred at 80° C. for 2 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain a yellow titanium-oxide polymer.

[0140] The softening point was 92° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2750 as measured by the vapor-pressure osmometry.

[0141] The obtained yellow titanium-oxide polymer (1-2 mg) and pure KBr (200 mg) were ground finely and uniformly, placed in a mold, and pressed into a transparent sheet on a tableting machine for IR spectrum characterization. The peaks at 2959 cm.sup.−1, 2922 cm.sup.−1 and 2872 cm.sup.−1 are C—H stretching vibration peaks; and the peaks at 1592 cm.sup.−1 and 1531 cm.sup.−1 belong to the absorption peaks of C═O (keto form) and C═C (enol form) at 425 cm.sup.−1 and 543 cm.sup.−1 in the acetylacetone ligand, proving the presence of Ti—O bonds in the structure of the polymer.

Example 6: Preparation of a Linear Titanium-Oxide Polymer

[0142] 1) 1 mol tetrabutyl titanate was added to a reaction vessel, followed by 0.5 mol acetylacetone, then the mixture was heated and stirred at 90° C. for 1.5 h; 2) the temperature was adjusted to 70° C., and a mixed solution of 1.2 mol water and 6 mol n-butanol was added dropwise; the mixture was stirred at 100° C. for 2.5 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain the titanium-oxide polymer.

[0143] The softening point was 98° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2930 as measured by the vapor-pressure osmometry.

Example 7: Preparation of a Nano-TiO.SUB.2 .Coating Structure Supported on a Silicon Slice

[0144] 1) The linear titanium-oxide polymer prepared in Example 6 was dissolved in ethanol to prepare a solution having a concentration of 0.4 wt % by Ti; 2) A silicon slice was ultrasonically cleaned in acetone, absolute ethanol and deionized water for 15 min respectively, and dried in air; 3) The silicon slice (2 cm×2 cm) was coated with the titanium-oxide polymer solution by spin coating, dried, and subjected to heat treatment in air at 500° C. for 30 min to obtain the nano-TiO.sub.2 coating structure supported on the silicon slice uniformly.

[0145] The TiO.sub.2 in the obtained coating structure was analyzed by XRD, confirming that the TiO.sub.2 obtained after heat treatment of the linear titanium-oxide polymer was the anatase TiO.sub.2.

[0146] The electron micrographs of the coating structure taken from different angles are shown in FIG. 5-1 and FIG. 5-2. It can be seen from the figures that the obtained coating has a flat surface, uniform thickness and porous structure, and the average particle size of the TiO.sub.2 particles is about 20 nm. The experimental results show that the titanium-oxide polymer has a good film-forming property, and the TiO.sub.2 coating obtained afterheat treatment is well supported on the Si slice.

Example 8: Preparation of a Nano-TiO.SUB.2 .Coating Structure Supported on a Silicon Slice

[0147] The preparation procedure was carried out according to the same steps as in Example 7, except that the prepared linear titanium-oxide polymer solution has a concentration of 0.8 wt % by Ti. The silicon slice was subjected to spin coating, drying, and heat treatment under the same conditions, to obtain the nano-TiO.sub.2 coating structure supported on the silicon slice uniformly.

[0148] The electron micrograph of the coating structure is shown in FIG. 6, and the resulting coating has a thickness of 50 nm.

Example 9: Preparation of a Nano-TiO.SUB.2 .Coating Structure Supported on a Quartz Glass Sheet

[0149] The titanium-oxide polymer prepared in Example 5 was dissolved in ethanol to prepare a solution having a concentration of 0.4 wt % by Ti; 2) A quartz glass sheet was ultrasonically cleaned in acetone, absolute ethanol and deionized water for 15 min respectively, and dried in air; 3) The quartz glass sheet (2 cm×2 cm) was coated with the titanium-oxide polymer solution by spin coating, and dried (the thickness of the wet film was 80 nm as measured by a step profiler); then the quartz glass sheet coated with wet film was subjected to heat treatment in air at 500° C. for 30 min to obtain the nano-TiO.sub.2 coating structure supported on the quartz glass sheet uniformly, with a coating thickness of 30 nm.

[0150] The obtained nano-TiO.sub.2-quartz glass coating structure was subjected to transmission test under visible light, and the transmittance was determined to be 89.2%.

[0151] In the room temperature, the contact angles of five different positions of the quartz glass sheet were measured by a contact angle measuring device before the quartz glass sheet was coated with the titanium-oxide polymer solution, and the contact angle was measured to be 72°.

[0152] The contact angles of five different positions at the surface of the coating structure were measured after the quartz glass sheet was loaded with TiO.sub.2 coating, and the contact angle was measured to be 5°. This indicated that the TiO.sub.2 coating prepared by the method of the present invention has super-hydrophilicity, which makes the TiO.sub.2 coating structure have performances of self-cleaning and decontamination, easy to clean, water-proof and fog-proof, etc.

Example 10: Preparation of a Nano-TiO.SUB.2 .Coating Structure Supported on a Quartz Glass Sheet

[0153] The titanium-oxide polymer prepared in Example 5 was dissolved in ethanol to prepare a solution having a concentration of 0.8 wt % by Ti; 2) A quartz glass sheet was ultrasonically cleaned in acetone, absolute ethanol and deionized water for 15 min respectively, and dried in air; 3) The quartz glass sheet (2 cm×4 cm) was coated with the titanium-oxide polymer solution by impregnation, and dried; then the quartz glass sheet coated with wet film was subjected to heat treatment in air at 500° C. for 60 min to obtain the nano-TiO.sub.2 coating structure supported on the quartz glass sheet uniformly.

[0154] 5 pieces of the obtained nano-TiO.sub.2-quartz glass coating structure were taken, and the surface of the coating structure was scratched in grids by the grid-scratching method. Then the transparent tape was repeatedly pasted and peeled off to observe the integrity of the TiO.sub.2 coating, and the adhesive force of the TiO.sub.2 coating to the surface of the coating structure was evaluated by the number of times of pasting. Thereafter, the contact angle of the water droplet on the surface of the coating structure was observed; or the integrity of the water film on the surface of the coating was observed when the coating structure was inserted into water and then pulled out.

TABLE-US-00001 Adhesive force Coating (the number structure of a of times of Hydrophilicity glass sheet Appearance pasting) (contact angle) 1 qualified 100 0 2 qualified 100 0 3 qualified 100 0 4 qualified 100 0 5 qualified 100 0

[0155] The contrast test was carried out between the nano-TiO.sub.2-quartz glass coating structure obtained in this example and the uncoated quartz glass: tap water was sprayed on the surface of the nano-TiO.sub.2-quartz glass coating structure obtained in this example, then a continuous water film was formed on the surface of the coating when the spraying was completed, and there were no water marks on the surface of the coating when the entire water film flowed down the substrate; however, when the uncoated quartz glass was sprayed with water, the water droplets were formed on the surface of the quartz glass, and water marks were left on the surface of the substrate after the water flowed away. This indicates that the coating of the present invention has a good hydrophilicity.

[0156] Due to the super-hydrophilicity, the nano-TiO.sub.2-quartz glass coating structure of this example can act as an automobile rearview mirror, moisture-resistant glass and anti-fouling glass which do not need to be wiped, particularly suitable for outdoor architectural glass. In addition, the photocatalytic property of the nano-TiO.sub.2-quartz glass coating structure can also be used to develop various products such as anti-fouling liquid crystal displays.

[0157] At present, the self-cleaning glass is used in the construction industry, but in fact it can also be applied in the field of super glass used in solar cells.

[0158] The above nano-TiO.sub.2-quartz glass coating structure (2 cm×4 cm) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate of the methyl orange solution was tested to be 50% after illumination by a 500W mercury lamp for 5 h; and the degradation rate of the methyl orange solution reached 80% after illumination for 8 h.

[0159] As can be seen from the above test, the self-cleaning function of the super-hydrophilic self-cleaning glass was as follows: by virtue of the affinity of the coating surface for water, the contact angle of the water droplets on the surface of the coating tended to zero; when the water came into contact with the coating, it spread rapidly on the surface of the coating, and then a uniform water film was formed, indicating that the coating has a super-hydrophilic property, and most of the organic or inorganic stains can be removed by the gravity drop of the uniform water film.

[0160] The above technical solution adopted by the present invention achieves the following beneficial effects: the present invention mainly solves the problems of uneven coating and poor coating appearance quality caused during the large-scale production of the self-cleaning glass and the like; moreover, the coating can be more firmly bonded to the surface of the glass substrate, ensuring the service life of the coating structure. The self-cleaning glass coating prepared in the present invention has a clear appearance and an effect of increasing transmittance.

Example 11: Preparation of a Nano-TiO.SUB.2 .Coating Structure Supported on an Aluminum Sheet

[0161] The linear titanium-oxide polymer prepared in Example 6 was dissolved in ethanol to prepare a solution having a concentration of 0.4 wt % by Ti; 2) An aluminum sheet (9 cm×2 cm×0.1 cm) was ultrasonically cleaned in acetone and absolute ethanol for 15 min respectively to remove the oil stain on the surface, then the aluminum sheet was oxidized in phosphoric acid; after the oxidation was completed, the residues on the surface were washed away with deionized water, and then the aluminum sheet was dried in air; 3) The aluminum sheet was coated with the titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 500° C. for 2 h to obtain the nano-TiO.sub.2 coating structure supported on the aluminum sheet uniformly.

[0162] The SEM micrograph of the coating structure is shown in FIG. 7. It can be seen from FIG. 7 that the obtained coating has a flat surface, with a uniform thickness and good transparency. The particle size of the TiO.sub.2 particles is 20 nm, and the thickness of the coating is 30 nm.

[0163] The above nano-TiO.sub.2-aluminium sheet coating structure (1.4407 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the methyl orange solution was illuminated by a 500W mercury lamp for 5 h, then the absorption spectrum of the methyl orange solution was tested, and degradation rate was tested to be 67.5%; and the degradation rate was tested to be 79.3% after degradation for 8 h.

[0164] 0.0019 g of TiO.sub.2 was coated on the aluminum sheet as described above, and 5.8 μg of TiO.sub.2 was coated on average per cm.sup.2 of aluminum sheet irrespective of the roughness of the surface.

[0165] 5 pieces of the obtained nano-TiO.sub.2— aluminum sheet coating structure were taken, and the surface of the coating structure was scratched in grids by the grid-scratching method. Then the transparent tape was repeatedly pasted and peeled off to observe the integrity of the TiO.sub.2 coating, and the adhesive force of the TiO.sub.2 coating to the surface of the coating structure was evaluated by the number of times of pasting. Thereafter, the contact angle of the water droplet on the surface of the coating structure was observed; or the integrity of the water film on the surface of the coating was observed when the coating structure was inserted into water and then pulled out.

TABLE-US-00002 Adhesive force Coating (the number structure of an of times of Hydrophilicity aluminum sheet Appearance pasting) (contact angle) 1 qualified 150 0 2 qualified 150 0 3 qualified 150 0 4 qualified 150 0 5 qualified 150 0

[0166] The hydrophilic experiment of the TiO.sub.2 coating on the aluminum sheet was carried out: a continuous water film can be formed on the surface of the coating, and when the entire water film flowed down the surface of the coating, there were no water marks on the surface of the coating; however, when the aluminum sheet without TiO.sub.2 coating was sprayed with water, the water droplets were formed on the surface of the aluminum sheet, and water marks were left on the surface of the substrate after the water flowed away. This indicates that the coating of the present invention has a good hydrophilicity.

[0167] It can be seen from the above test that the nano-TiO.sub.2 coating structure of the present invention not only can degrade organic substances, but also has hydrophilicity; it has a certain self-cleaning function, and thus can be applied to indoor household appliances; moreover, it has the functions of purifying air, deodorizing, sterilizing and self-cleaning.

Example 12: Preparation of a Nano-TiO.SUB.2.Coating Structure Supported on a Titanium Sheet

[0168] The linear titanium-oxide polymer prepared in Example 6 was dissolved in ethanol to obtain a solution having a concentration of 0.4 wt % by Ti; 2) A titanium sheet (9 cm×2 cm×0.1 cm) was ultrasonically cleaned in acetone, absolute ethanol and pure water for 15 min respectively, and then blow-dried; 3) The titanium sheet was coated with the titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 500° C. for 30 min to obtain the nano-TiO.sub.2 coating structure supported on the titanium sheet uniformly.

[0169] The above coating structure (1.3459 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the methyl orange solution was illuminated by a 500W mercury lamp for 5 h, and the degradation rate of the methyl orange solution was tested to be 82%; and methyl orange was completely degraded after being illuminated for 8 h. 0.0020 g of TiO.sub.2 was coated on the titanium sheet as described above, and 6.2 μg of TiO.sub.2 was coated on average per cm.sup.2 of titanium sheet irrespective of the roughness of the surface.

[0170] 5 pieces of the obtained nano-TiO.sub.2— titanium sheet coating structure were taken, and the surface of the coating structure was scratched in grids by the grid-scratching method. Then the transparent tape was repeatedly pasted and peeled off to observe the integrity of the TiO.sub.2 coating, and the adhesive force of the TiO.sub.2 coating to the surface of the coating structure was evaluated by the number of times of pasting. Thereafter, the contact angle of the water droplet on the surface of the coating structure was observed; or the integrity of the water film on the surface of the coating was observed when the coating structure was inserted into water and then pulled out.

TABLE-US-00003 Coating Adhesive force structure of a (the number of Hydrophilicity titanium sheet Appearance times of pasting) (contact angle) 1 qualified 100 0 2 qualified 100 0 3 qualified 100 0 4 qualified 100 0 5 qualified 100 0

[0171] The hydrophilic experiment of the TiO.sub.2 coating on the titanium sheet was carried out: a continuous water film can be formed on the surface of the coating, and when the entire water film flowed down the surface of the coating, there were no water marks on the surface of the coating; however, when the titanium sheet without coating was sprayed with water, water droplets were formed on the surface of the aluminum sheet, and water marks were left on the surface of the substrate after the water flowed away. This indicates that the coating of the present invention has a good hydrophilicity.

[0172] It can be seen from the above test that the nano-TiO.sub.2 coating structure supported on the titanium sheet not only can degrade organic substances, but also has hydrophilicity; it has a certain self-cleaning function, and thus can be applied to indoor household appliances; moreover, it has the functions of purifying air, deodorizing, sterilizing and self-cleaning.

Example 13: Preparation of a Nano-TiO.SUB.2.Coating Structure Supported on a Foamed Nickel

[0173] The linear titanium-oxide polymer prepared in Example 1 was dissolved in ethanol to obtain a solution having a concentration of 0.4 wt % by Ti; 2) A foamed nickel (9 cm long, and 2 cm wide) was ultrasonically cleaned in acetone, absolute ethanol and pure water for 15 min respectively, and then blow-dried; 3) The foamed nickel was coated with the linear titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 500° C. for 30 min to obtain the nano-TiO.sub.2 coating structure supported on the foamed nickel uniformly.

[0174] The above coating structure (0.5525 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the methyl orange solution was illuminated by a 500W mercury lamp for 8 h, and the degradation rate of the methyl orange solution was tested to be 57.2%.

[0175] The coating structure described above was subjected to ultrasonic treatment for 2 h by an ultrasonic instrument with a working frequency of 20 kHz, and almost no powder shed off.

[0176] The nano-TiO.sub.2 coating structure supported on the foamed nickel prepared in this example has a good stability. When it is used repeatedly, its photocatalytic activity can be completely recovered and regenerated by simple methods such as heating and washing with water, and it can continue to maintain its good stability.

[0177] By utilizing the TiO.sub.2 photocatalytic coating, the coating structure can be used for degradation of organic substances and indoor formaldehyde, and also can be used for sterilization, deodorization and filtration, etc.

Example 14: Preparation of a Nano-TiO.SUB.2.Coating Structure Supported on a Glass Fiber Cloth

[0178] The linear titanium-oxide polymer prepared in Example 6 was dissolved in ethanol to obtain a solution having a concentration of 0.4 wt % by Ti; 2) A glass fiber cloth was cut into a square with a side length of 2 cm, and activated in hot water; 3) The glass fiber cloth was coated with the titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 480° C. for 30 min to obtain the nano-TiO.sub.2 coating structure supported on the glass fiber cloth uniformly.

[0179] The electron micrograph of the coating structure is shown in FIG. 8. It can be seen from FIG. 8 that the obtained coating has a flat surface with a uniform thickness.

[0180] The above coating structure (0.2859 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the methyl orange solution was illuminated by a 500W mercury lamp for 8 h, and the degradation rate of the methyl orange solution was tested to be 88.8%.

[0181] The glass fiber cloth coated with TiO.sub.2 coating was subjected to ultrasonic treatment for 2 h by an ultrasonic instrument with a working frequency of 20 kHz, and the shed rate of the powder was 0.1 wt %.

[0182] The TiO.sub.2 coating structure supported on the glass fiber cloth prepared in this example can be used as filter materials to degrade the pollutants in water, and such glass fiber cloth can also be used for sterilization, deodorization and the like.

Example 15: Preparation of a Nano-TiO.SUB.2.Coating Structure Supported on a Porous Ceramic

[0183] The linear titanium-oxide polymer prepared in Example 5 was dissolved in ethanol to obtain a solution having a concentration of 0.9 wt % by Ti; 2) A porous ceramic was washed; 3) The porous ceramic was coated with the linear titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 520° C. for 1.5 h to obtain the nano-TiO.sub.2 coating structure supported on the porous ceramic.

[0184] The above coating structure (6.1924 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate of the methyl orange solution was 58.0% after illumination by a 500W mercury lamp for 5 h; and the degradation rate of the methyl orange solution was 78.0% after illumination for 8 h.

[0185] The porous ceramic coated with TiO.sub.2 coating was subjected to ultrasonic treatment for 120 min by a ultrasonic instrument with a working frequency of 20 kHz, and almost no powder shed off.

[0186] By utilizing the TiO.sub.2 photocatalytic coating, the nano-TiO.sub.2 coating structure supported on the porous ceramic prepared in this example can be used for degradation of indoor formaldehyde, as well as sterilization and deodorization, etc.

Example 16: Preparation of a Nano-TiO.SUB.2.Coating Structure Supported on a Molecular Sieve

[0187] The linear titanium-oxide polymer prepared in Example 5 was dissolved in ethanol to obtain a solution having a concentration of 0.2 wt % by Ti; 2) A molecular sieve was washed; 3) The molecular sieve was coated with the linear titanium-oxide polymer solution by impregnation, dried, and subjected to heat treatment in air at 500° C. for 1.0 h to obtain thenano-TiO.sub.2 coating structure supported on the molecular sieve uniformly.

[0188] The above coating structure (0.2500 g) was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate of the methyl orange solution was 76.2% after illumination by a 500W mercury lamp for 4 h.

[0189] By utilizing the TiO.sub.2 photocatalytic coating, the nano-TiO.sub.2 coating structure supported on the molecular sieve prepared in this example can be used for degradation of indoor organic and inorganic substances in water, and also can be used for sterilization and deodorization, etc.

Example 17: Preparation of a Linear Titanium-Oxide Polymer

[0190] 1 mol tetraisobutyl titanate was added to a reaction vessel, and the temperature was adjusted to 50° C.; then 0.8 mol acetylacetone was added, and the mixture was heated and stirred at 50° C. for 1 h; 2) The temperature was adjusted to 80° C., and a mixed solution of 0.8 mol water and 2.5 mol isobutanol was added dropwise; the mixture was continued to be heated and stirred at 80° C. for 2 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain a yellow titanium-oxide polymer.

[0191] The softening point was 92° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2750 as measured by the vapor-pressure osmometry.

[0192] The obtained yellow titanium-oxide polymer (1-2 mg) and pure KBr (200 mg) were ground finely and uniformly, placed in a mold, and pressed into a transparent sheet on a tableting machine for IR spectrum characterization. The peaks at 2959 cm.sup.−1, 2922 cm.sup.−1 and 2872 cm.sup.−1 are C—H stretching vibration peaks; and the peaks at 1592 cm.sup.−1 and 1531 cm.sup.−1 belong to the absorption peaks of C═O (keto form) and C═C (enol form) at 425 cm.sup.1 and 543 cm.sup.1 in the acetylacetone ligand, proving the presence of Ti—O bonds in the structure of the polymer.

Example 18: Preparation of a Linear Titanium-Oxide Polymer

[0193] 1 mol tetrabutyl titanate was added to a reaction vessel, followed by 0.5 mol acetylacetone, then the mixture was heated and stirred at 90° C. for 1.5 h; 2) the temperature was adjusted to 70° C., and a mixed solution of 1.2 mol water and 6 mol n-butanol was added dropwise; the mixture was stirred at 100° C. for 2.5 h after the addition was completed; after the mixture was cooled, the solvent was removed under reduced pressure to obtain the titanium-oxide polymer.

[0194] The softening point was 98° C. as measured by the ring-and-ball method; and the number average molecular weight (Mn) was 2930 as measured by the vapor-pressure osmometry.

Example 19: Preparation of a Glass Fiber Mat-Nano-TiO.SUB.2 .Photocatalytic Coating Structure

[0195] A glass fiber mat (18 cm×9 cm×0.8 cm) (purchased from Hubei Feilihua Quartz Glass Co., Ltd) was subjected to heat treatment in a muffle furnace at 500° C. for 1 h; then the treated glass fiber mat was activated in hot water at 90° C. for 1 h; the activated glass fiber mat was impregnated in an equal volume of the solution of the linear titanium-oxide polymer (obtained in Example 17) in ethanol (at a concentration of 0.8 wt %), and then lifted and pulled, dried, and sintered at 500° C. for 1 h, to obtain the glass fiber mat-nano-TiO.sub.2 photocatalyst coating structure with nano-TiO.sub.2 loading capacity of 10.5 wt % by weight of the glass fiber mat.

[0196] The scanning electron microscopy analysis of the obtained glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure under different magnifications was carried out, and the results are shown in FIG. 9-1, FIG. 9-2 and FIG. 9-3. FIG. 10 also shows a flowchart of a method to prepare linear titanium-oxide polymer, titanium dioxide coating, and photocatalytic coating according to yet another embodiment of the present invention.

[0197] The XRD analysis of the obtained glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was carried out, and the results confirmed that the TiO.sub.2 obtained after heat treatment of the linear titanium-oxide polymer was of anatase phase.

[0198] 0.5 g of the obtained glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate (i.e., the photocatalytic efficiency of the coating structure) of methyl orange was 83.3% after illumination by a 500W mercury lamp for 2.5 h.

Comparative Example 1: Catalytic Efficiency of Unsupported TiO.SUB.2 .Photocatalyst

[0199] The unsupported linear titanium-oxide polymer of Example 17 was sintered at 500° C. for 1 h to obtain 50 mg of TiO.sub.2 powder; then the obtained powder was added to 50 ml of methyl orange solution with a concentration of 15 mg/L, and the mixture was illuminated by a 500W mercury lamp for 2.5 h. The degradation rate of methyl orange was 69.5%.

[0200] It can be seen from the comparative example that the photocatalytic efficiency (the degradation rate of methyl orange) of the glass fiber mat-nano-TiO.sub.2 photocatalyst coating structure in Example 19 of the present invention is significantly higher than that of the unsupported TiO.sub.2 powder. This is due to the fact that the glass fiber mat can implement rapid surface enrichment of methyl orange and thus can provide a high concentration environment for the photocatalytic reaction of TiO.sub.2; in addition, the photocatalytic reaction belongs to the first-order reaction, thereby the local high concentration can effectively improve the photocatalytic reaction rate.

Example 20: The Reusability of a Glass Fiber Mat-Nano-TiO.SUB.2 .Photocatalytic Coating Structure

[0201] The reusability of the obtained glass fiber mat-nano-TiO.sub.2 photocatalyst coating structure was determined as follows: the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure (0.6517 g) obtained in Example 17 was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the methyl orange solution was illuminated by a 500W mercury lamp for 2.5 h, and the photocatalytic efficiency (i.e., the degradation rate of methyl orange) was 89.3%. The glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure after photodegradation of methyl orange was washed with deionized water for 5-8 times, and dried at 100° C. Then the photodegradation experiment for the methyl orange solution was carried out again under the same conditions, and the photocatalytic efficiency was calculated. The above operation was repeated 10 times.

[0202] In the prior art, the surface of the glass fiber mat-TiO.sub.2 coating structure in which the TiO.sub.2 coating is coated by a binder may adsorb part of methyl orange and impurities after photocatalytic reaction, leading to contamination of the TiO.sub.2 photocatalyst and reduced effective area of photocatalytic reaction. In addition, part of the unsteadily loaded TiO.sub.2 particles may shed off due to washing in the stirring process, such that the photocatalytic activity of the glass fiber mat tends to decrease gradually. After the above operation was repeated 10 times, the photocatalytic efficiency of the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure of the present invention still remained above 80.2%, indicating that the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure of the present invention has excellent reusability.

Example 21: Preparation of a Glass Fiber Mat-Nano-TiO.SUB.2.Photocatalyst Coating Structure

[0203] A glass fiber mat (18 cm×9 cm×0.8 cm) (purchased from Hubei Feilihua Quartz Glass Co., Ltd) was subjected to heat treatment in a muffle furnace at 550° C. for 30 min; then the treated glass fiber mat was activated in hot water at 80° C. for 1 h; the activated glass fiber mat was impregnated in an equal volume of the solution of the linear titanium-oxide polymer (prepared in Example 18) in ethanol (at a concentration of 1.3 wt %), and then lifted and pulled, dried, and sintered at a high temperature, to obtain thenano-TiO.sub.2 photocatalytic coating structure with TiO.sub.2 loading capacity of 16.7% by weight of the glass fiber mat.

[0204] 0.5000 g of the above glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 91.9% after illumination by a 500W mercury lamp for 2.5 h.

Example 22: Preparation of a Glass Fiber Mat-Nano-TiO.SUB.2 .Photocatalytic Coating Structure

[0205] A glass fiber mat (18 cm×9 cm×0.8 cm) (purchased from Hubei Feilihua Quartz Glass Co., Ltd) was subjected to heat treatment in a muffle furnace at 550° C. for 1.5 h; then the treated glass fiber mat was activated in hot water at 100° C. for 2 h; the activated glass fiber mat was impregnated in an equal volume of the solution of the linear titanium-oxide polymer (prepared in Example 17) in ethanol (at a concentration of 1.15 wt %), and then lifted and pulled, dried, and sintered at a high temperature, to obtain the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure with TiO.sub.2 loading capacity of 15.1 wt % by weight of the glass fiber mat.

[0206] 0.5000 g of the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure obtained above was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the photocatalytic efficiency (the degradation rate of methyl orange) was 86.8% after illumination by a 500W mercury lamp for 2.5 h.

[0207] The load stability of the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure obtained above was determined as follows: the obtained glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was immersed in deionized water by using the method of ultrasonic washing, then subjected to ultrasonic treatment at 40 kHz for 1 h, and then filtered and dried. The load stability of the sample was measured by the change in the mass of the TiO.sub.2 that was loaded effectively. After the first ultrasonic treatment, the weight of TiO.sub.2 was only reduced by 1.15 wt %.

Example 23: Preparation of a Glass Fiber Mat-Nano-TiO.SUB.2 .Photocatalytic Coating Structure

[0208] A glass fiber mat (18 cm×9 cm×0.8 cm) (purchased from Hubei Feilihua Quartz Glass Co., Ltd) was subjected to heat treatment in a muffle furnace at 450° C. for 2 h; then the treated glass fiber mat was activated in hot water at 90° C. for 1 h; the activated glass fiber mat was impregnated in an equal volume of the solution of the linear titanium-oxide polymer (obtained in Example 18) in ethanol (at a concentration of 2.5 wt %), and then lifted and pulled, dried, and sintered, to obtain the glass fiber mat-nano-TiO.sub.2 photocatalyst coating structure with TiO.sub.2 loading capacity of 32.3 wt % by weight of the glass fiber mat.

[0209] 0.5000 g of the above glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 75.9% after illumination by a 500W mercury lamp for 2.5 h. This is due to the following fact: although the loading rate is high, the TiO.sub.2 particles are agglomerated together, resulting in less effective active centers and less free radicals attracted and thus lower catalytic efficiency.

Example 24: Preparation of a Glass Fiber Mat-Nano-TiO.SUB.2.Photocatalyst Coating Structure

[0210] A glass fiber mat (27 cm×27 cm×0.8 cm) (purchased from Hubei Feilihua Quartz Glass Co., Ltd.) was subjected to heat treatment in a muffle furnace at 550° C. for 30 min; then the treated glass fiber mat was activated in hot water at 100° C. for 30 min; the activated glass fiber mat was impregnated in an equal volume of the solution of the titanium-oxide polymer (obtained in Example 1) in ethanol (at a concentration of 0.8 wt %), and then lifted and pulled, dried, and sintered, to obtain the glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure with TiO.sub.2 loading capacity of 10.5 wt % by weight of the glass fiber mat.

[0211] 0.5000 g of the above glass fiber mat-nano-TiO.sub.2 photocatalytic coating structure was added to 50 ml of methyl orange solution (at a concentration of 15 mg/L), and the degradation rate was 84.1% after illumination by a 500W mercury lamp for 2.5 h.

[0212] A method for preparing a linear titanium-oxide polymer is disclosed. The method is comprising steps of: 1) adding a titanate to a reaction vessel, and adding a chelating agent to the titanate at 50-90° C. to obtain a first mixture, heating and stirring the first mixture for 0.5-1.5 h; 2) adding a mixed solution of water and alcohol dropwise to the first mixture at 50-90° C. to obtain a second mixture, and stirring the second mixture at 80-110° C. for 1.5-4 h after an addition of the mixed solution is completed, cooling the second mixture, then removing a solvent under a reduced pressure to obtain the linear titanium-oxide polymer; wherein the linear titanium-oxide polymer comprises the following structural formula:

##STR00006##

the R.sup.1 is selected from the group consisting of —C.sub.2H.sub.5, —C.sub.3H.sub.7, —C.sub.4H.sub.9, and —C.sub.5H.sub.11; the R.sup.2 is OR.sup.1 or a complexing group selected from the group consisting of CH.sub.3COCHCOCH.sub.3 and CH.sub.3COCHCOOC.sub.2H.sub.5, at least 50% of the R.sup.2 are the complexing group by a total number of the R.sup.2; a number average molecular weight (Mn) of the linear titanium-oxide polymer is 2000-3000 when determined by a vapor-pressure osmometry; and a solvent-free pure titanium-oxide polymer has a softening point in a range of 90-127° C. when determined by a ring-and-ball method.

[0213] A molar ratio of the titanate, the chelating agent and the water is 1:(0.5-1.4):(0.8-1.3).

[0214] A molar ratio of the water to the alcohol in the mixed solution of water and alcohol is 1:(3-20).

[0215] In the step 1), the titanate has a structure of Ti(OR.sup.1).sub.4, wherein the R.sup.1 of the Ti(OR.sup.1).sub.4 is selected from the group consisting of —C.sub.2H.sub.5, —C.sub.3H.sub.7, —C.sub.4H.sub.9, and —C.sub.5H.sub.11.

[0216] A method for preparing a nano-TiO.sub.2 coating structure based is disclosed. The method is comprising steps of: 1) dissolving linear titanium-oxide polymer in a solvent to prepare a solution, wherein a concentration of the solution is 0.3-2 wt % by titanium; 2) pretreating a surface of a substrate to be coated optionally; 3) applying the solution uniformly on the substrate to obtain a solution-coated substrate, drying and sintering the solution-coated substrate to obtain a nano-TiO.sub.2 coating supported on the substrate; the nano-TiO.sub.2 coating structure comprises the substrate, and the nano-TiO.sub.2 coating supported on the surface of the substrate; wherein the nano-TiO.sub.2 coating comprises a plurality of nano-TiO.sub.2 particles, an average particle size of the plurality of nano-TiO.sub.2 particles is 10-50 nm; and a loading capacity of the nano-TiO.sub.2 coating structure is 1.0-100 μg of nano-TiO.sub.2 coating per cubic centimeter of the substrate.

[0217] The linear titanium-oxide polymer is prepared by a method comprising steps of: a) adding a titanate to a reaction vessel, and adding a chelating agent to the titanate at 50-90° C. to obtain a first mixture, heating and stirring the first mixture for 0.5-5.0 h; b) adding a mixed solution of water and alcohol dropwise to the first mixture at 50-90° C. to obtain a second mixture, and stirring the second mixture at 80-110° C. for 1.5-6 h after an addition of the mixed solution is completed, cooling the second mixture, and then removing a solvent under a reduced pressure to obtain the linear titanium-oxide polymer.

[0218] The substrate comprises silicon-based materials, metals, glass, ceramics, and adsorbent materials, or a combination of the silicon-based materials, the metals, the glass, the ceramics, and the adsorbent materials.

[0219] The metals comprise steel plates, aluminum plates, titanium plates, copper plates, zinc plates, foamed nickels, foamed aluminums and aluminum honeycombs; the glass comprises glass sheets, glass fiber cloths, hollow glass microspheres, glass beads, and glass springs; the ceramics comprise hollow ceramic microspheres, ceramic tiles, ceramic plates and honeycomb ceramics; and the adsorbent materials comprise silicon oxide, silica gels, activated carbons, zeolites, and molecular sieves.

[0220] The nano-TiO.sub.2 coating described in the step 3) is obtained by sintering the solution-coated substrate in air at 450-550° C.

[0221] The basic principle, primary characteristics and advantages of the present invention have been described above by way of the examples. It should be understood by those skilled in the art that the present invention is not limited to the foregoing examples, and the above examples and the contents described in the specification are merely used for illustrating the principle of the present invention. There will be various variations and modifications of the present invention without departing from the spirit and scope of the present invention.