Composition for use as NO

1. A composition capable of forming a translucent coating on a construction material surface, comprising:

a) photocatalytic titanium dioxide particles having a de-NO x activity, the photocatalytic titanium dioxide particles consisting essentially of at least 50% by mass of an anatase crystalline form having a mean size range of from 1 nm up to 150 nm and a surface area per gram of at least 30 m 2 /g,

b) a silicon based-material in which said photocatalytic titanium dioxide particles are dispersed, wherein said silicon based material includes at least one polysiloxane derivative having the formula

wherein

R 1 and R 2 are alkyl radicals of from 1 to 20 carbon atoms or phenyl, and

c) de-HNO 3 particles having a de-HNO 3 activity, wherein the de-HNO 3 particles are selected from the group consisting of calcium carbonate, magnesium carbonate and mixtures thereof, wherein

(i) the photocatalytic titanium dioxide particles and the de-HNO 3 particles are present in an amount lower than 20% by weight of the total weight of said composition, and the photocatalytic titanium dioxide particles are present in an amount of at least 5% by weight of the total weight of said composition,

(ii) the ratio of de-HNO 3 particles to photocatalytic titanium dioxide particles is in the range of from 0.05 to 2.

2. The composition according to claim 1 , wherein the photocatalytic titanium dioxide particles exhibit a mean size from 5 nm to 20 nm.

3. The composition according to claim 1 , wherein the photocatalytic titanium dioxide particles are present in an amount up to 15% by weight (as expressed in dry matter) of the total weight of said composition.

4. The composition according to claim 1 further including a solvent.

5. A method for imparting self-cleaning properties against NO x and HNO 3 atmospheric contaminants on a surface of a material, said method comprising applying onto the surface of said material a composition according to claim 1 , and drying or curing the composition on the surface to obtain a thin film coating thereon thereby imparting de-NO x and de-HNO 3 properties to the surface of the material.

6. A composition capable of forming a translucent coating on a construction material surface, comprising:

a) photocatalytic titanium dioxide particles having a de-NO x activity, the photocatalytic titanium dioxide particles consisting essentially of at least 80% by mass of an anatase crystalline form having a mean size range of from 1 nm up to 150 nm and a surface area per gram of at least 30 m 2 /g,

b) a silicon based-material in which said photocatalytic titanium dioxide particles are dispersed, wherein said silicon based material includes at least one polysiloxane derivative having the formula

wherein

R 1 and R 2 are alkyl radicals of from 1 to 20 carbon atoms or phenyl, and

c) de-HNO 3 particles having a de-HNO 3 activity, wherein the de-HNO 3 particles are selected from the group consisting of calcium carbonate, magnesium carbonate and mixtures thereof, wherein

(i) the photocatalytic titanium dioxide particles and the de-HNO 3 particles are present in an amount lower than 20% by weight of the total weight of said composition, and the photocatalytic titanium dioxide particles are present in an amount of at least 5% by weight of the total weight of said composition; and

(ii) the ratio of de-HNO 3 particles to photocatalytic titanium dioxide particles is in the range of from 0.05 to 2.

7. An improved translucent thin film adhered to a construction material surface, comprising:

a) photocatalytic titanium dioxide particles having at least a de-NO x activity, the photocatalytic titanium dioxide particles consisting essentially of at least 80% by mass of an anatase crystalline form, said photocatalytic titanium dioxide particles having a mean size range of from 1 nm up to 150 nm and a surface area per gram of at least 30 m 2 /g,

b) a silicon based-material in which said photocatalytic titanium dioxide particles are dispersed, wherein said silicon based material includes at least one polysiloxane derivative having the formula

wherein

R 1 and R 2 are alkyl radicals of from 1 to 20 carbon atoms or phenyl, and

c) de-HNO 3 particles having a de-HNO 3 activity, wherein the de-HNO 3 particles are selected from the group consisting of calcium carbonate, magnesium carbonate and mixtures thereof wherein

(i) the photocatalytic titanium dioxide particles and the de-HNO 3 particles are present in the dispersion in an amount lower than 20% by weight of the total weight of said dispersion, and the photocatalytic titanium dioxide particles are present in an amount of at least 5% by weight of the total weight of said dispersion; and

(ii) the ratio of de-HNO 3 particles to photocatalytic titanium dioxide particles is in the range of from 0.05 to 2.

8. The composition according to claim 6 , wherein the photocatalytic titanium dioxide particles exhibit a mean size from 5 nm to 20 nm.

9. The composition according to claim 6 , wherein the photocatalytic titanium dioxide particles are present in an amount up to 15 % by weight (as expressed in dry matter) of the total weight of said composition.

10. The composition according to claim 6 further including a solvent.

11. A method for imparting self-cleaning properties against NO x and HNO 3 atmospheric contaminants on a surface of a material, said method comprising applying onto the surface of said material a composition according to claim 6 , and drying or curing the composition on the surface to obtain a thin film coating thereon thereby imparting de-NO x and de-HNO 3 properties to the surface of the material.