FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION: Photocatalytic composite layer coating
APPLICANT(S):
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030. Maharashtra, India, an Indian Company
lNVENTOR(S):
Shukla Gaurav and Roy Pradip; both of Crompton Greaves Ltd, Advance Material Process and Technology Centre, CG Global R&D Centre, Kanjurmarg (E), Mumbai - 400042, Maharashtra, India; both Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
The present invention relates to coating and to its environmental applications.
Particularly, the present invention relates to photo catalytic composite layer coating exhibiting enhanced photo catalytic action upon irradiation with visible light and ultraviolet light, and films made thereof.
The present invention also relates to substrate coated with the photocatalytic composite layer coating of the invention which is capable of killing bacteria and purifying air upon irradiation with visible light as well as ultraviolet light.
BACKGROUND OF THE INVENTION:
Removing organic pollutants in the air and killing bacteria efficiently is always a challenge. Various organic pollutants and a great number of bacteria fill the environment.
It is known that Titanium dioxide (Ti02) can effectively decompose organic pollutants in air and water under ultra violet and kill bacteria therein. Therefore, a simple and feasible way is to have nano-phase Ti02 immobilised on the surface of a substrate such as glass, metals and constructive materials, and then exposes the substrate under ultraviolet to catalytically kill the bacteria.
Nano Ti02 Photocatalyst coating is a revolutionary purifying coating technology based on the most advanced nano-science: photocatalysis. Photocatalyst coating is a "green" technology that can be applied on walls, ceiling, floor carpets, curtains,

car interior, toilet seats etc. and all kind of surfaces to form an invisible film. The film can work all day to decompose all kinds or micro-organic matters, like bacteria, viruses, mold, formaldehyde, benzene, xylene, ammonia, volatile organic compounds (VOC's), tough odours etc.
Researchers have used photocatalytic oxidation (PCO) to break down and destroy many types of organic pollutants. It has been used to purify drinking water, destroy bacteria and viruses, remove metals from waste streams, and breakdown organics into simpler components of water and C02.
Since photocatalysis has been realized to be a great oxidation mechanism, researchers began testing it on many different compounds, and in many different processes. To date, this technology has been used to detoxify drinking water, decontaminate industrial waste water, and purify air streams.
US publication 2004202723 provide a process for preparing a Ti02 thin film. However, this method of using Ti02 thin films for killing bacteria and viruses is activated in an environment under ultraviolet irradiation.
JP 10128154 describes a dust collecting electrode with photocatalyst membrane comprising anatase type titanium oxide, synthetic zeolite and Si02 type matter. The coating in this patent was UV activated environment.
Research has been always carried out with new compositions which can be used for enhancing the photocatalytic activity and effective killing of bacteria thus leading to air purification.

However, there is a need for coating that enables the activation of Ti02 in ultraviolet as well as visible light with enhanced photocatalytic activity and efficient bacteria killing and air purification improvement.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a photocatalytic composite layer coating having enhanced photocatalytic activity upon irradiation of Ultra Violet and Visible light.
Another object of the invention is to provide the photocatalytic composite layer coating for any suitable substrate requiring anti bacterial and air purifying activity.
Yet another object of the invention is to provide the photcatalytic composite layer coating that can be applied onto any suitable substrate where a self cleaning hydrophobic coat required.
Still another object of the invention is to provide a "Green Technology Product".
An additional object of the invention is to provide the substrate coated with the said photocatalytic composite layer coating with enhanced photocatalytic activity under both ultraviolet and visible light.
Another additional object of the invention is to provide the photocatalytic lamp coated with the said photocatalytic composite layer coating with enhanced photocatalytic activity under both ultraviolet and visible light.

Yet additional object of the invention is to provide the photo catalytic film having composite layers with enhanced photocatalytic activity under both ultraviolet and visible light.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates XRD spectra of Ti02 based photocatalytic compositions according to examples 2a, 2b, 3a, 3b, 5a and 6a to confirmed presence of anatase phase Ti02 and no change in lattice structure upon doping into Ti02.
Figure 2 illustrates absorbance spectra of undoped Anatase Ti02 film according to example 7, 0.5 % Fe doped TiO2 film according to examples 5a and 6a and 0.5% Pt doped Ti02 film according to examples 2a and 3a.
Figure 3 illustrates experimental Setup for measuring the Photo-catalytic Efficiency of Ti02 photocatalytic compositions.
Figure 4 illustrates graphical representation of evaluation of photo-catalytic . degradation efficiency of Ti02 based coatings using Methylene Blue (MB) under exposure of broadband fluorescent light.
Figure 5 illustrates graphical representation of comparative evaluation of photo¬catalytic degradation efficiency of Ti02 based coatings with and without exposure of broadband fluorescent light.

DETAILED DESCRIPTION OF THE INVENTION:
Before the present invention is described, it is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.
Before the present invention is described, it is to be understood that 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 this invention belongs. Further, it is to be understood that the present invention is not limited to the methodologies and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described, as these may vary within the specification indicated. Unless stated to the contrary, any use of the words such as "including," "containing," "comprising," "having" and the like, means "including without limitation" and shall not be construed to limit any general statement that it follows to the specific or similar items or matters immediately following it. Embodiments of the invention are not mutually exclusive, but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth the appended claims. Further the terms disclosed embodiments are merely exemplary methods of the invention, which may be embodied in various forms.

The term "luminaire" or "luminaries" as used herein intend to cover all kind of lamps, tube lights, or any other kind of lights or light source.
The term "substrate" as used herein should not be restricted to luminaire including all kind of lamps, tube lights, or any other kind of lights or light source but also cover glass, metal, wall, ceramics, appliances, or any other substrate where a photocatlytic activity including anti bacterial and air purifying activity as well as self cleaning hydrophobic coat is required, depending upon its use.
According to one of the embodiments of the invention, there is provided a composite layer coating to enhance photocatalytic activity; said composite layer coating comprising :
a. First layer comprising anatase metal doped nano-Ti02 /β-zeolite on the
outer surface of a substrate; said layer having thickness in the range of 1 to
3 µm;
and
b. Second layer comprising energy storage material like Tungsten oxide (W03)
or Nickel hydroxide (Ni(OH)2) on top of the first layer: said second layer
having a thickness in the range of 50 to 300 nm.
Particularly, the first layer comprises the composition of nano-titanium oxide (Ti02) in anatase form in the range of 80 to 90 %, (3-zeolite in the range of 5 to 15 % and metal doped titanium oxide (Ti02) such as precious metal, [platinum (Pt)] or iron (Fe) in the range of 0.1 to 1.0 %.
Particularly, the second layer comprising the energy storage materials [WO3 or Ni(OH)2] in the range of 1.0 to 3.0 %.

Preferably, the component, nano-Titanium dioxide (Ti02) in anatase form used in the first layer of the invention is about 88 %.
Preferably, the component, β-zeolite used in the first layer of the invention is about
10%.
Preferably, the components, precious metal [platinum (Pt)] or iron (Fe) doped
Titanium dioxide (Ti02) used in the first layer of the invention is about 0.5 %.
Preferably, the energy storage materials used in the second layer of the invention is about 1.5%.
Particularly, said substrate may be luminaire including all kind of lamps, tube lights, or any other kind of lights or light source, glass, metal, wall, ceramics, appliances, or any other suitable substrate or any other suitable appliances where photocatalytic activity is required.
More particularly, said substrate is luminaire including all kind of lamps, tube lights, or any other kind of lights or light source.
The composite layer coating or film can be applied onto any suitable substrate where a self cleaning hydrophobic coat is required.
According to another embodiment of the invention, there is provided a luminaire coated with composite layer coating of the invention with enhanced photocatalytic activity with added advantage of reductive or oxidative energy storage.

According to yet another embodiment of the invention, there is provided a photocatalytic film having enhanced photocatalytic activity, said film made of the composite layer of the invention.
According to still another embodiment of the invention, there is provided a method for preparing the composite layer coating to enhance photocatalytic activity; said method comprising :
A. Preparing a first layer of coating of anatase metal-doped nano-Ti02/β-zeolite
by
(i) preparing anatase nano- Ti02 solution,
(ii) preparing titanium complex by mixing β-zeolite into the solution of step
(i) to support nano-Ti02, (iii) hydrolyzing the titanium complex with water to obtain gel solution, and (iv) doping Ti02by subjecting the gel solution of hydrolyzed titanium
complex of step (iii) to obtain the anatase metal -doped nano-Ti02/β-
zeolite;
B. Preparing a second layer of energy storage material of W03 or Ni(OH)2;
and
C. Applying the first layer on the substrate followed by second layer on top of
the first layer by conventional method.
Particularly, anatase nano-Ti02 solution is prepared by mixing of Titanium tetraisopropoxide [Ti{OCH(CH3)2}4] with a chelating agent, isopropyl acetate [CH3C{0}CH2C{0}CH3], followed by the addition of alcoholic solvent such as isopropanol, isobutanol, etc.
The mole ratio of [CH3C{0}CH2C{0}CH3] /Ti{OCH(CH3)2}4 used is in the range

of 1 to 50: 1to 10.
The mole ratio of solvent to chelating agent used is around 10 to 1 : 100 to 1.
Particularly, "titanium complex" is prepared by adding β-zeolite into the anatase
nano-Ti02 solution and stirring slowly for 2 to 4 hours at a speed of 10 to 50 rpm to prepare the titanium complex.
The β-zeolite provides support nano-Ti02 and substantially eliminates the agglomeration.
The mole ratio of β-zeolite to Titanium tetraisopropoxide used is around 1 to 20 : 1 to 2.
The concentration of β-zeolite used is in the range of 5 to 15 % by weight.
Particularly, the complex is hydrolyzed by treating it with cold water to obtain gel solution.
Particularly, the ratio of water to titanium complex used is around 50 to 1: 200 to 1.
Preferably doping of Ti02 is carried out by treating the hydrolyzed complex in the form of gel solution with chloroplatinic acid (H2PtCl6.4H20) to achieve 0.1 to 0.6 % of platinum doping on Ti02; stirring constantly and heating the gel solution up to 100° C; adjusting a pH of the gel solution to less than 2 by adding acid like HC1

and other suitable acid and heating the gel solution up to 240° C to 250° C to obtain a slightly yellowish transparent solution of anatase platinum-doped nano-Ti02/β-zeolite.
Preferably doping of Ti02 is carried out by treating the hydrolyzed complex in the form of gel solution with Ferric chloride (FeCl3) to achieve 0.1 to 0.6 % of Iron doping on Ti02; stirring constantly and heating the gel solution up to 100° C; adjusting a pH of the gel solution to less than 2 by adding acid like HC1 and other suitable acid and heating the gel solution up to 240° C to 250° C to obtain a light brown transparent solution of anatase Iron-doped nano-Ti02/β-zeolite.
The anatase metal-doped nano-Ti02/β-zeolite like anatase platinum-doped nano-Ti02/β-zeolite or anatase Iron-doped nano-Ti02/β-zeolite was used to dip-coat or multiple coat the substrates to achieve a layer of thickness of around 1 to 3 µm, After coatings, coated substrates were allowed to dry.
Particularly, preparing a second layer of energy storage material of W03 or Ni(OH)2 by conventional method.
More particularly, preparing a second layer of energy storage material of W03 by dipping into sol-gel solution of an energy storage material like W03 to apply a thin layer on the top of the first layer.
Alternatively, preparing a second layer of energy storage material of Ni(OH)2 by depositing layer of Ni(OH)2 either by cathodic deposition method or any other conventional method on the top of the first layer.

For depositing second layer of Ni(OH)2, 0.01 M to 0.2 M of aqueous solution of Ni (N03)2 was used for a time period of 100 to 1000 s at a current density of ~ 1 mA/cm .
The second layer is a thin layer having a thickness of around 50 to 300 nm.
According to still another embodiment of the invention, there is provided a method for preparing a film having enhanced photocatalytic activity; said method comprising :
a. Preparing a first layer of film of anatase metal -doped nano-Ti02/ β-zeolite
and
b. Preparing a second layer of film of storage material of WO3 or Ni(OH)2.
According to still another embodiment of the invention, there is provided a method for applying the composite layer coating on outer surface of the substrate to enhance photocatalytic activity; said method comprising :
a. Preparing a first layer of coating of anatase metal-doped nano-Ti02/ β-zeolite
and applying the layer of thickness of around 1 to 3 µm by suitable
conventional methods including but not limited to dip coating, spraying, spin
coating, screen printing, electroplating, etc. followed by drying the same;
and
b. Preparing a second layer of energy storage material of WO3 or Ni(OH)2 and
applying the layer of thickness of around 50 to 300 nm by suitable
conventional methods including but not limited to cathodic deposition,
electrophoretic deposition, sol-gel deposition, etc .

The film can be prepared by any conventional method such as casting, dip coating or spray coating.
The composition of the invention gets activated under visible light and UV light as compared to the composition comprising only of Ti02. which is activated only under UV light.
Further, the composition of the invention comprises energy storage materials such as tungsten oxide (W03) and Nickel hydroxide Ni(OH)2 thus allowing enhancement in photocatalytic activity by reserving energy for some time even in dark conditions. Oxidative energy of Ti02 photocatalyst can be stored in Ni(OH)2 under UV irradiation, while WO3 coatings can store energy via reductive energy storage. W03 is also an efficient photocatalyst under visible light which can, in turn, increase the photocatalytic efficacy of proposed fluorescent lamps.
The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
Example 1:
Anatase nano-TiO2 solution
1 mole of Titanium tetraisopropoxide [Ti{OCH(CH3)2}4] was mixed with 0.2 mole of a chelating agent, isopropyl acetate [CH3C{0}CH2C{0}CH3]. 10 M of isopropanol was added to the mixture to obtain anatase nano-Ti02 solution.
"Titanium complex"
5 % of |β -zeolite was mixed into the anatase nano-Ti02 solution to prepare titanium

complex. The complex was slowly stirred for 2 hours at a speed of 50 rpm. Gel solution comprising hydrolyzed titanium complex
The complex was hydrolyzed by treating it with 100 M of cold water (<10° C) to obtain gel solution comprising hydrolyzed titanium complex.
Anatase Pt-doped nano-TiO2
The hydrolyzed gel solution was treated with 0.5mM_chloroplatinic acid (H2PtCl6.4H20) to achieve 0.5 % of platinum doping on Ti02. The gel solution was constantly stirred and heated up to 100° C. After that, 2N HCL was slowly added to maintain a pH of less than 2 and solution was further heated up to 240° C. A slightly yellowish transparent solution was obtained which was used to dip-coat the fluorescent lamps.
Example 2:
Applying composite layer coat on the lamp
a) Coating of anatase Pt-doped nano-Ti02
Multiple coats of the first layer containing anatase Pt-doped nano-Ti02 were
applied by dip coating using the solution of anatase Pt-doped nano-Ti02 prepared
according to example 1 to achieve a coating thickness of around 1 \xm on the lamp.
The coated lamp was air dried and baked at a temperature of 240° C. The coated
lamp so obtained was used in step (b) for further coating with W03.
The x-ray diffraction (XRD) spectra (A) of the said coating is shown in Figure 1,

confirming the presence of only anatase phase and no change in lattice structure was observed upon Pt doping into Ti02.
b) Coating of W03 over anatase Pt-doped nano-Ti02
The coated fluorescent lamps were dipped into sol-gel solution of an energy
storage material like W03 to apply a thin layer having a thickness of around 100
nm.
The x-ray diffraction (XRD) spectra (C) of the said coating is shown in Figure 1,
confirming the presence of only anatase phase and no change in lattice structure
was observed upon Pt doping into Ti02.
Example 3:
Applying composite layer coat on the lamp
a) Coating of anatase Pt-doped nano-Ti02
Multiple coats of the first layer containing anatase Pt-doped nano-Ti02 were applied by dip coating using the solution of anatase Pt-doped nano-TiO2 prepared according to example 1 to achieve a coating thickness of around 1 urn on the lamp. The coated lamp was air dried and baked at a temperature of 240° C. The coated lamp so obtained was used in step (b) for further coating with Ni(OH)2. The x-ray diffraction (XRD) spectra (A) of the said coating is shown in Figure 1, confirming the presence of only anatase phase and no change in lattice structure was observed upon Pt doping into Ti02.
b) Coating of Ni(OH)2 over anatase Pt-doped nano-Ti02
The coated fluorescent lamps were coated with the second layer of Ni(OH)2 by

cathodic deposition using 0.02 M of aqueous solution of Ni (N03)2 for a time period of 240 s at a current density of ~ 1 mA/cm . The thickness of the coating achieved is around 100 nm.
The x-ray diffraction (XRD) spectra (D) of the said coating is shown in Figure 1, confirming the presence of only anatase phase and no change in lattice structure was observed upon Pt doping into Ti02.
Example 4:
Anatase nano-TiO2 solution
1 mole of Titanium tetraisopropoxide [Ti{OCH(CH3)2}4] was mixed with 0.2 mole of a chelating agent, isopropyl acetate [CH3C{0}CH2C{0}CH3]. 10 M of isopropanol was added to the mixture to obtain anatase nano-Ti02 solution.
"Titanium complex"
5 % of β-zeolite was mixed into the anatase nano-Ti02 solution to prepare titanium complex. The complex was slowly stirred for 2 hours at a speed of 50 rpm.
Gel solution comprising hydrolyzed titanium complex
The complex was hydrolyzed by treating it with 100 M of cold water (<10° C) to obtain gel solution comprising hydrolyzed titanium complex.
Anatase Fe-doped nano-TiO2
The hydrolyzed gel solution was treated with 1.05 g_anhydrous ferric chloride

chloride (FeCl3) to achieve 0.5 % of iron doping on Ti02. The gel solution was constantly stirred and heated up to 100° C. After that, 2N HCL was slowly added to maintain a pH of less than 2 and solution was further heated up to 240° C. A light brown transparent solution was obtained which was used to dip-coat the fluorescent lamps.
Example 5:
Applying composite layer coat on the lamp
a) Coating of anatase Fe-doped nano-Ti02
Multiple coats of the first layer containing anatase Fe-doped nano-Ti02 were applied by dip coating using the solution of anatase Fe-doped nano-Ti02 prepared according to example 4 to achieve a coating thickness of around 1 u.m on the lamp. The coated lamp was air dried and baked at a temperature of 240° C. The coated lamp so obtained was used in step (b) for further coating with W03. The x-ray diffraction (XRD) spectra (B) of the said coating is shown in Figure 1, confirming the presence of only anatase phase and no change in lattice structure was observed upon Fe doping into Ti02.
b) Coating of W03 over anatase Fe-doped nano-Ti02
The coated fluorescent lamps were dipped into sol-gel solution of an energy storage material, W03, to apply a thin layer having a thickness of around 100 nm.
Example 6:
Applying composite layer coat on the lamp a) Coating of anatase Fe-doped nano-Ti02

Multiple coats of the first layer containing anatase Fe-doped nano-Ti02 were applied by dip coating using the solution of anatase Fe-doped nano-Ti02 prepared according to example 4 to achieve a coating thickness of around 1 µm on the lamp. The coated lamp was air dried and baked at a temperature of 240° C. The coated lamp so obtained was used in step (b) for further coating with Ni(OH)2. The x-ray diffraction (XRD) spectra (D) of the said coating is shown in Figure 1, confirming the presence of only anatase phase and no change in lattice structure was observed upon Fe doping into Ti02.
b) Coating of Ni(OH)2 over anatase Fe-doped nano-Ti02
The coated fluorescent lamps were coated with the second layer of Ni(OH)2 by cathodic deposition using 0.02 M of aqueous solution of Ni (N03)2 for a time period of 240 s at a current density of- 1 mA/cm2. The thickness of the coating achieved is around 100 nm.
Example 7:
The lamp is coated with only undoped Ti02 having thickness of around 1 urn. The coated lamp was air dried and baked at a temperature of 240° C.
Absorbance spectra of undoped anatase Ti02 coating (according to example 7), Pt-doped Ti02 coatings (according to examples 2a and 3a) and Fe-doped Ti02 coatings (according to examples 5a and 6a) were measured. Figure 3 illustrates Absorbance spectra of undoped Anatase Ti02 film, 0.5 % Fe doped Ti02 film and 0.5% Pt doped Ti02 film. According to figure 3, absorption edge of undoped Ti02 shifted from UV region, 382 nm, to visible region, 460 nm for Pt-doped Ti02 and 486 nm for Fe doped Ti02 respectively. Thus confirming the visible light activated

photocatalysis via doped Ti02 coatings. Since broadband fluorescent light contains nearly 5% of UV and rest 95% visible light, visible light activated photocatalysis will be much more efficient compared to only UV activated photocatalysis. The photocatalytic efficiency of the coatings prepared according to examples 2, 3, 5 and 6 were studied and compared with undoped Ti02 coating according to example 7. The glass slides were coated (3) with 7 different photocatalytic coating compositions, namely undoped anatase Ti02 (according to example 7); Pt-doped Ti02 (according to examples 2a and 3a) ; Fe-doped Ti02 (according to examples 5a and 6a); Pt-doped Ti02 + W03 (according to example 2); Pt-doped Ti02 + Ni(OH)2 (according to example 3); Fe-doped Ti02 + W03 (according to example 5); Fe-doped Ti02 + Ni(OH)2) (according to example 6). Photocatalysis activity of the coated glass plates (3) were characterized by estimating the degradation rate of Methylene Blue (MB). The setup used to evaluate the degradation rate of MB is shown in Figure 4. Briefly, a 10 cm x 10 cm glass plate was coated (3) using the method described in examples 2, 3. 5, 6 and 7. The coated plate (3) was placed in between a fluorescent lamp source (4) (6500 K broadband cool white light coming out of a 27 W fluorescent lamp) and a specially designed reaction chamber (2) containing MB solution. The coaled side of the plate was exposed to MB solution while being irradiated by fluorescent source from backside for a total exposure time period varying from 5 min to 90 min at the fixed irradiance of 1 mW/cm . Here the MB solution used was 200 ml of 15 mM solution of MB in water which was kept constant throughout the experiment. The solution was also stirred at a speed of 30 rpm using a motorized stirrer (1) during exposure to lamp irradiation. This was done to bring uniform change in the concentration of MB. The photocatalytic efficiency of the coated material [Pt- or Fe-doped Ti02 + W03 or Ni(OH)2] was estimated by measuring reduction in MB concentration upon UV + visible light irradiation from the lamp. Reduction in MB concentration was

monitored by recording UV-Visible spectra of irradiated MB sample and further determining C/Co ratio, where Co is the absorbance peak area integration at 600 to 700 nm for the untreated MB sample and C is the same for treated MB sample. The change in C/Co ratio with exposure time is shown in Figure 5 for different photocatalytic coating compositions. The results confirmed the better photo-catalytic efficiencies of proposed coating combinations when compared to undoped Ti02 or even Pt/Fe doped Ti02.
In addition to check the effect of energy storage coating, photocatalytic efficiency measurements were also carried out in dark condition i.e. without exposure of broadband fluorescent light and the results are shown in Figure 5. It can be clearly observed that Ti02 coatings combined with energy storage materials showed active photocatalytic degradation of MB for 30 mins after switching off the fluorescent lamp source (exposure time ~ 30 min) in the dark condition.
It was observed that ink degraded (disappeared) is directly proportional to photocatalytic activity of a particular coating.
Thus, the experimental results showed the superior photocatalytic performance of proposed coating in the visible region when compared to undoped Ti02.
The present invention as described above, it is to be understood that this invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.

We claim,
1. A composite layer coating to enhance photocatalytic activity;
said composite layer coating comprising :
a. First layer comprising anatase metal doped nano-Ti02 /β-zeolite on the
outer surface of a substrate; said layer having thickness in the range of 1
to 3 µm;
and
b. Second layer comprising energy storage material like W03 or Ni(OH)2
on top of the first layer said second layer having a thickness in the range
of50 to 300nm.
2. The composite layer coating as claimed in claim 1, wherein the first layer comprises the composition of nano-titanium oxide (Ti02) in anatase form in the range of 80 to 90 %, j3-zeolite in the range of 5 to 15 % and metal doped titanium oxide (Ti02) such as precious metal, [platinum (Pt)] or iron (Fe) in the range of 0.1 to 1.0%.
3. The composite layer coating as claimed in claim 1, wherein the second layer comprising the energy storage materials [W03 or Ni(OH)2] in the range of 1.0 to 3.0%.
4. A method for preparing the composite layer coating to enhance photocatalytic activity;
said method comprising :
A. Preparing a first layer of coating of anatase metal-doped nano-Ti02/β-zeolite by

i preparing anatase nano-Ti02 solution by mixing of Titanium
tetraisopropoxide [Ti{OCH(CH3)2}4] with a chelating agent, isopropyl acetate [CH3C{0}CH2C{0}CH3] followed by the addition of alcoholic solvent such as isopropanol or isobutanol,
ii preparing titanium complex by mixing (3-zeolite into the solution of step (i) to support nano-Ti02 with stirring slowly for 2 to 4 hours at a speed of 10 to 50 rpm;
iii hydrolyzing the titanium complex with water to obtain gel solution, and
iv doping Ti02 by subjecting the gel solution of hydrolyzed titanium complex of step (iii) to obtain the anatase metal -doped nano-Ti02/β-zeolite;
B. Preparing a second layer of energy storage material of W03 or
Ni(OH)2;
C. Applying the first layer on the substrate followed by second layer on top
of the first layer by conventional method.
5. The method as claimed in claim 4, wherein the mole ratio of [CH3C{0}CH2C{0}CH3] /Ti{0CH(CH3)2}4 used in step (i) is in the range of 1 to 50: 1 to 10.
6. The method as claimed in claim 4, wherein the mole ratio of solvent to chelating agent, [CH3C{0}CH2C{0}CH3] used in step (i) is in the range of 10 to 1 : 100 to 1.
7. The method as claimed in claim 4, wherein the mole ratio of (3-zeolite to Titanium tetraisopropoxide used is around 1 to 20 : 1 to 2.

8. The method as claimed in claim 4, wherein the concentration of β-zeolite used is in the range of 5 to 15 % by weight.
9. The method as claimed in claim 4, wherein the ratio of water to titanium complex used is around 50 to 1: 200 to 1.
10. The method as claimed in claim 4, wherein the step (iv) comprising treating the hydrolyzed complex in the form of gel solution obtained in step (iii) with chloroplatinic acid (H2PtCl6.4H20) to achieve 0.1 to 0.6 % of platinum doping on Ti02; stirring constantly and heating the gel solution up to 100° C; adjusting pH of the gel solution to less than 2 by adding acid like HC1 and heating the gel solution up to 240° C to 250° C to obtain a slightly yellowish transparent solution of anatase platinum-doped nano-Ti02/ β-zeolite.
11. The method as claimed in claim 4, wherein the step (iv) comprising treating the hydrolyzed complex in the form of gel solution obtained in step (iii) with Ferric chloride (FeCl3) to achieve 0.1 to 0.6 % of Iron doping on Ti02; stirring constantly and heating the gel solution up to 100° C; adjusting pH of the gel solution to less than 2 by adding acid like HC1 and heating the gel solution up to 240 ° C to 250° C to obtain a light brown transparent solution of anatase Iron-doped nano-Ti02/ β-zeolite.
12. A luminare coated with composite layer coating as claimed in claim 1 with enhanced photocatalytic activity with added advantage of reductive or oxidative energy storage.

13. A photocatalytic film having enhanced photocatalytic activity, said film made of the composite layers as claimed in claim 1.