Claims:1) A composition comprising nanotized graphene oxide, filler, binder and stabilizing agent.
2) The composition as claimed in claim 1, wherein the nanotized graphene oxide comprises functional group selected from a group comprising alcohol (–OH), ether (>O), aldehyde (–HC=O), ketone (>C=O), and carboxylic acid (–COOH) or any combination thereof.
3) The composition as claimed in claim 1, wherein the nanotized graphene oxide comprises graphene layers ranging from about 1 to 15; and wherein thickness of graphene layers in the nanotized graphene oxide ranges from about 0.335nm to about 5.5nm; and the nanotized graphene oxide has particle size ranging from about 10nm to 50nm,
4) The composition as claimed in claim 1, wherein the filler is selected from a group comprising sand, sand, crushed pebbles or any combination thereof.
5) The composition as claimed in claim 4, wherein the sand is concrete sand or mason sand or a combination thereof, comprising gneiss, trap rock, limestone or granite or any combination thereof.
6) The composition as claimed in claim 1, wherein the binder is cement.
7) The composition as claimed in claim 6, wherein the cement is selected from a group comprising portland cement comprising calcium oxide, silica, alumina, ferric oxide and gypsum, high alumina cement comprising calcium oxide, alumina and ferric oxide, sulphate resisting Portland cement comprising calcium oxide, silica, alumina, ferric oxide and gypsum or any combination thereof.
8) The composition as claimed in claim 1, wherein the stabilizing agent comprises acrylic acid and carbohydrate; wherein the carbohydrate is dispersed in the acrylic acid.
9) The composition as claimed in claim 1, wherein the composition further comprises water; wherein the water is tap water or distilled water or a combination thereof.
10) The composition as claimed in claim 1, wherein concentration of the nanotized graphene oxide ranges from about 0.3 % w/w to 5 % w/w; concentration of the binder ranges from about 30 % w/w to 40 % w/w; concentration of the filler ranges from about 45% w/w to 60% w/w; concentration of the stabilizing agent ranges from about 0.03% to 0.5%.
11) The composition as claimed in claim 9, wherein pH of the composition ranges from about 9 to about 11.5.
12) A method of preparing the composition as claimed in claim 1, wherein said method comprises steps of
nanotizing graphite to obtain nanotized graphene oxide; and
mixing the nanotized graphene oxide, the filler, the binder and the stabilizing agent to obtain the composition.
13) The method as claimed in claim 12, wherein the nanotizing of graphite comprises step of:
agitating graphite to obtain nanotized graphene oxide comprising functional group(s) selected from a group comprising alcohol (–OH), ether (>O), aldehyde (–HC=O), ketone (>C=O), and carboxylic acid (–COOH).
14) The method as claimed in claim 13, wherein the graphite is subjected to agitation in presence of oxidizing agent or under oxidizing atmosphere or a combination thereof.
15) The method as claimed in claim 14, wherein the oxidizing agent is selected from a group comprising phosphoric acid and nitric acid or a combination thereof.
16) The method as claimed in claim 13, wherein the agitation is carried out by mechanical attrition milling, thermo mechanical attrition milling or planetary ball milling.
17) The method as claimed in claim 12, wherein concentration of the nanotized graphene oxide ranges from about 0.3 % w/w to 5 % w/w; concentration of the binder ranges from about 30 % w/w to 40 % w/w; concentration of the filler ranges from about 45% w/w to 60% w/w; and concentration of the stabilizing agent ranges from about 0.03% to 0.5%.
18) The method as claimed in claim 12, wherein the method further comprises step of mixing the composition with water to obtain slurry; wherein the water is tap water, distilled water or a combination thereof, and the pH of the slurry is ranging from about 9 to 11.5.
19) The method as claimed in claim 18, wherein volume of the water ranges from about 250 ml to 500 ml per litre of slurry; and wherein the mixing is carried out at a temperature ranging from about 20°C to 60°C.
20) The method as claimed in claim 12 or claim 18, wherein the mixing is by mechanical technique; wherein the mechanical technique is stirring.
21) A coated article comprising-
a substrate; and
coating of the composition as claimed in claim 1 or 9 on the substrate.
22) The coated article as claimed in claim 21, wherein inner surface or outer surface or both the surfaces of the substrate comprises coating of the composition
23) The coated article as claimed in claim 21, wherein the substrate is selected from a group comprising pipe, tube, reservoir, tank, culverts, and walls; wherein the substrate is composed of material selected from a group comprising steel, zinc, tin, nickel, and chromium or any combination thereof.
24) The coated article as claimed in claim 21, wherein the coating of the composition has thickness ranging from about 100 microns to 4cms.
25) The coated article as claimed in claim 21, wherein bactericidal activity of the coating article ranges from about 82% to 100%.
26) The coated article as claimed in claim 21, wherein corrosion rate of the coated article ranges from about 0.001 g/cm2 to 0.009 g/cm2 per 90 days.
27) A method of preparing the coated article defined in claim 21, wherein said method comprises steps of:
applying the composition defined in claim 9 to at least one surface of the substrate; and
subjecting the coated surface of the substrate to heating, followed by curing the coat on the substrate to obtained coated article.
28) The method as claimed in claim 27, wherein the method comprises a step of cleaning the substrate prior to applying the composition.
29) The method as claimed in claim 28, wherein the substrate is subjected to cleaning with alkali, wetting agent or surfactant or any combination thereof; wherein the alkali is alkaline salt selected from a group comprising silicate, phosphate and caustic soda or any combination thereof; wherein the cleaning is conducted at a temperature ranging from about 55°C to 65°C, for time ranging from about 2 minutes to 3 minutes.
30) The method as claimed in claim 27, wherein the composition is applied to the substrate by means selected from a group comprising immersing the substrate in the composition, applying the composition on the substrate by brush and applying the composition on the substrate by centrifugal force, or any combination thereof.
31) The method as claimed in claim 27, wherein the heating is carried out by technique selected from a group comprising resistance heating and hot air heating; at a temperature ranging from about 45°C to 75°C; for time ranging from about 2 minutes to 10 minutes.
32) The method as claimed in claim 27, wherein the curing is carried out at a temperature ranging from about 20°C to 40°C; for time ranging from about 0.5 hours to 4 hours.
, Description:TECHNICAL FIELD
The present disclosure relates to the field of graphene, in combination with microbiology. The disclosure specifically describes a composition comprising nanotized graphene oxide and binder, optionally along with filler and stabilizing agent, wherein the said composition exhibits germicidal activity including but is not limited to bactericidal activity and fungicidal activity, when coated on metallic surfaces. The present disclosure further describes a method of preparing said composition, describes a coated article and describes a method of preparing said coated article.

BACKGROUND OF THE DISCLOSURE
Antibacterial materials are of great interest for various applications ranging from hospital beds to kitchen counter tops, especially in the era of multi-drug resistant pathogens. Consequently, treatment with antibiotics has been a serious challenge and there is a constant search for finding environmental friendly and cost effective alternative ways for antibacterial treatment. Nanomaterials such as silver nanoparticles and graphene based composite materials are known to exhibit biocidal activities. However, these materials need to be supported on bulk substrates and matrix material for their effective uses. Apart from particulate form, large area graphene films produced by chemical vapor deposition (CVD) method on Cu has also shown antibacterial properties. However, they possess limitation in their application such as it is very difficult and expensive to stabilize large area graphene films and the transfer of large area graphene films from growth substrate to target substrate is challenging accompanied by ineffectiveness of the final product.
It has been found that Graphene Oxide (GO) film on certain metallic surfaces shows excellent antibacterial properties relative to bare metal surfaces. However, GO alone cannot form long range films over most substrates. Although graphene/ and or graphene oxide has been mixed with cement for different applications in the prior art (eg: as building material for improvement in mechanical properties), it has never been reported for its antibacterial properties. Further, applications of Graphene oxide per se, in prior art, has been primarily limited to use in biomedical applications such as bone cement and dental cement.
The need of the hour is a composition that can be efficiently coated on a substrate to form a long- range coating on a substrate and be preserved in said form over extended periods of time possessing enhanced antimicrobial properties.

STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure provides a composition comprising nanotized graphene oxide, filler, binder and stabilizing agent.

In an embodiment, the nanotized graphene oxide comprises functional group selected from a group comprising alcohol (–OH), ether (>O), aldehyde (–HC=O), ketone (>C=O), and carboxylic acid (–COOH) or any combination thereof.

The present disclosure provides a method of preparing the composition comprising nanotized graphene oxide, filler, binder and stabilizing agent, wherein said method comprises steps of
nanotizing graphite to obtain nanotized graphene oxide; and
mixing the nanotized graphene oxide, the filler, the binder and the stabilizing agent to obtain the composition.

The present disclosure further provides a coated article comprising-
a substrate; and
coating of the composition comprising nanotized graphene oxide, filler, binder and stabilizing agent on the substrate.
Furthermore, the present disclosure provides a method of preparing the coated article, wherein said method comprises steps of:
applying the composition comprising nanotized graphene oxide, filler, binder and stabilizing agent to at least one surface of the substrate; and
subjecting the coated surface of the substrate to heating, followed by curing the coat on the substrate to obtained coated article.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

Figure 1 represents the schematic diagram showing synthesis of graphene oxide directly from graphite.

Figure 2 represents (a) FESEM image of graphene oxide on the steel substrate. (b) TEM image of powder sample obtained by scribing and (c) SAED pattern confirming crystalline graphene oxide structure.

Figure 3 represents Growth Inhibition Assay on E.coli colonies on LB agar plates over wherein (a) illustrates rich growth bacterium on coated glass substrate; (b) illustrates no growth in agar plate having coated article having steel substrate and growth observed on plate comprising bare metal (c) illustrates no growth in agar plate having coated article having tin substrate and growth observed on plate comprising bare metal (d) illustrates no growth in agar plate having coated article having nickel substrate and growth observed on plate comprising bare metal ; and (e) illustrates no growth in agar plate having coated article having zinc substrate and growth observed on plate comprising bare metal

Figures 4 represents Viability Assay: The percentage of reduction in cell viability is calculated, as the viable CFU/ml over the initial CFU/ml seeded on bare substrates and coated articles of the present invention. Error bars represent standard deviation from three independent sets of experiments.

Figure 5 represents FESEM analysis data of E.coli cells, inoculated on different surfaces of coated article, such as (e) GO.Zn (coated article having zinc substrate), (d) GO. Ni (coated article having Nickel substrate), (c) GO.Sn (coated article having tin substrate), (b) GO.Steel (coated article having steel substrate). Cells are showing alterations in cell morphology, membrane damage and cytoplasm leakage under high and low magnifications (red arrows). Cells on (a) GO-Glass (coated article having glass substrate) are healthy and uniform looking without any evidence of membrane damage (black arrow).

DETAILED DESCRIPTION OF THE DISCLOSURE
As used herein, the abbreviation GO represents Graphene Oxide.

As used herein, the term ‘slurry’ has been used to define the form of the composition obtained post mixing with water, which is used for coating the substrate.
The present disclosure relates to a composition.

In an embodiment, the composition of the present disclosure comprises nanotized graphene oxide (GO) and binder, optionally along with filler and stabilizing agent.

In another embodiment, the composition of the present disclosure comprises nanotized graphene oxide, filler, binder and stabilizing agent.

In an embodiment, the nanotized graphene oxide comprises functional group selected from a group comprising alcohol (–OH), ether (>O), aldehyde (–HC=O), ketone (>C=O) and carboxylic acid (–COOH), or any combination thereof.

In a further embodiment, the nanotized graphene oxide comprises graphene layers ranging from about 1 to 15.

In a non-limiting embodiment, the nanotized graphene oxide comprises about 1, about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14 or about 15 graphene layers.

In an embodiment, thickness of the graphene layers in the nanotized graphene oxide ranges from about 0.335 nm to 5.5 nm.

In a non-limiting embodiment, thickness of the graphene layers in the nanotized graphene oxide is about 0.3nm, about 0.335 nm, about 0.35nm, about 0.5nm, about 1nm, about 1.5nm, about 2nm, about 2.5nm, about 3nm, about 3.5nm, about 4nm, about 4.5nm, about 5nm or about 5.5nm.

In an embodiment, nanotized graphene oxide has particle size ranging from about 10nm to 50nm,

In another embodiment, nanotized graphene oxide has particle size of about 10nm, about 15nm, about 20nm, about 25nm, about 30nm, about 35nm, about 40nm, about 45nm or about 50nm.

In another embodiment, graphene oxide particles are present in the form of oxidized flakes of graphite, reduced graphene oxide or graphene nanoparticles.

In an embodiment, the filler in the composition of the present disclosure is selected from a group comprising sand and crushed pebbles, or a combination thereof.

In a further embodiment, the sand is concrete sand or mason sand or a combination thereof, comprising gneiss, trap rock, limestone or granite or any combination thereof.

In a non-limiting embodiment, the concrete sand is crushed at quarry and then washed through a screen to eliminate large pieces of rock.

In another non-limiting embodiment, the mason sand is crushed at quarry finer than concrete sand and then washed through a screen to ensure uniformity of the grains.

In an embodiment, the binder in the composition of the present disclosure is cement.

In a further embodiment, the cement is selected from a group comprising portland cement comprising calcium oxide, silica, alumina, ferric oxide and gypsum, high alumina cement comprising calcium oxide, alumina and ferric oxide, sulphate resisting Portland cement comprising calcium oxide, silica, alumina, ferric oxide and gypsum, or any combination thereof.

In a non-limiting embodiment, the portland cement is manufactured by grinding and mixing lime or calcium oxide (CaO), obtained from limestone, chalk, shells, shale or calcareous rock; Silica (SiO2), obtained from sand, old bottles, clay or argillaceous rock; Alumina (AlO2), obtained from bauxite, recycled aluminium, clay; and Iron (Fe2O3), obtained from clay, iron ore, scrap iron and fly ash, the ground and blended components are fed through a kiln at a temperature of about 1400°C to obtain greyish-black pellets called clinkers; wherein the clinker is then cooled, pulverized, followed by adding gypsum to obtain a mixture and the mixture is ground to extremely fine powder to obtain portland cement.

In another non-limiting embodiment, the high alumina cement is manufactured by crushing, milling and proportioning lime or calcium oxide (CaO), obtained from limestone, chalk, shells, shale or calcareous rock; Alumina (AlO2), obtained from bauxite, recycled aluminium, clay; and Iron (Fe2O3), obtained from clay, iron ore, scrap iron and fly ash, and the components are fused together in a kiln to obtain basalt-like pellets called clinkers. The clinker is then ground to extremely fine powder to obtain alumina cement.

In yet another non-limiting embodiment, the sulphate resisting portland cement is manufactured by grinding and mixing lime or calcium oxide (CaO), obtained from limestone, chalk, shells, shale or calcareous rock; Silica (SiO2), obtained from sand, old bottles, clay or argillaceous rock; Alumina (AlO2), obtained from bauxite, recycled aluminium, clay; Iron (Fe2O3), obtained from clay, iron ore, scrap iron and fly ash; the ground and blended components are fed through a kiln at a temperature of about 1400°C to obtain greyish-black pellets called clinkers; wherein the clinker is then cooled, pulverized, followed by adding gypsum to obtain a mixture and the mixture is ground to extremely fine powder to obtain sulphate resisting portland cement, wherein the percentage of tricalcium aluminate is restricted to below 6%.

In an embodiment, the stabilizing agent in the composition of the present disclosure comprises acrylic acid and carbohydrate, wherein the carbohydrate is dispersed in acrylic acid. The carbohydrate is selected from a group comprising starch and glycogen.
In another embodiment, the stabilizing agent in the composition of the present disclosure comprises acrylic acid and carbohydrate, wherein the carbohydrate is dispersed in acrylic acid. The carbohydrate is any polysaccharide with hydrolyzed alpha bonds.

In a non-limiting embodiment of the present disclosure, the stabilizing agent functions as a plasticizer, thereby eliminating need for addition of separate plasticizers while preparing slurry of the composition.

In another non-limiting embodiment, the composition further comprises water, wherein the water is tap water or distilled water, or a combination thereof.

In an embodiment, the composition comprising water is in a form of a slurry.

In an embodiment, concentration of the nanotized graphene oxide ranges from about 0.3 % w/w to 5 % w/w.
In a non-limiting embodiment, concentration of the nanotized graphene oxide in the composition is about 0.3 % w/w, about 0.5% w/w, about 1% w/w, about 1.5% w/w, about 2% w/w, about 2.5% w/w, about 3% w/w, about 3.5% w/w, about 4% w/w, about 4.5% w/w or about 5% w/w.

In an embodiment, concentration of the binder ranges from about 30 % w/w to 40 % w/w.

In a non-limiting embodiment, concentration of the binder in the composition is about 30% w/w, about 31% w/w, about 32% w/w, about 33% w/w, about 34% w/w, about 35% w/w, about 36% w/w, about 37% w/w, about 38% w/w, about 39% w/w or about 40% w/w.

In an embodiment, concentration of the filler ranges from about 45% w/w to 60% w/w.

In a non-limiting embodiment, concentration of the filler in the composition is about 45% w/w, about 46% w/w, about 47% w/w, about 48% w/w, about 49% w/w, about 50% w/w, about 51% w/w, about 52% w/w, about 53% w/w about 54% w/w, about 55% w/w, about 56% w/w, about 57% w/w, about 58% w/w, about 59% w/w or about 60% w/w.

In an embodiment, concentration of the stabilizing agent ranges from about 0.03% to 0.5%.

In a non-limiting embodiment, concentration of the stabilizing agent in the composition is about 0.03%, about 0.05%, about 0.1%, about 0.15%, about 0.2%, about 0.25%, about 0.3%, about 0.35%, about 0.4%, about 0.45% or about 0.5%.

In an embodiment, the concentration of the stabilizing agent is less than or equal to 10% of the amount of the graphene oxide in the composition.

In an embodiment, pH of the composition comprising nanotized graphene oxide, filler, binder, stabilizing agent and water ranges from about 9 to about 11.5, wherein the pH of the composition is maintained by the alkalis present in the constituents of the binder.

In a non-limiting embodiment, pH of the composition is about 9, about 9.5, about 10, about 10.5, about 11 or about 11.5.

In an embodiment, the basic pH of the composition enhances the efficacy of the stabilizing agent to disperse the graphene oxide particles in the coating.

In an embodiment, the disclosure provides a method of preparing the composition, wherein said method comprises steps of-
nanotizing graphite to obtain nanotized graphene oxide; and
mixing the filler, the binder, stabilizing agent and nanotized graphene oxide to obtain the composition.

In an embodiment, the graphite is beneficiated by techniques including but is not limited to chemical treatment by oxidizing agent, followed by attrition and attrition under oxygen atmosphere, to obtain nanotized graphene oxide comprising functional groups selected from a group comprising alcohols (-OH), ethers (>O), aldehydes (-HC=O), ketones (>C=O), and carboxylic acids (-COOH), or a combination thereof.

In another embodiment, graphite is chemically beneficiated to add oxygen functional groups selected from a group comprising alcohols (-OH), ethers (>O), aldehydes (-HC=O), ketones (>C=O), and carboxylic acids (-COOH), or a combination thereof, to individual layers of covalently bonded carbon atoms. The beneficiated graphite is subjected to mechanical attrition mills to obtain nanoparticle graphene oxide, wherein the thickness of the graphene layers ranges from about 1 to 15.

In another embodiment, graphite is beneficiated by agitating in thermos mechanical attrition mills or planetary ball mills in presence of oxidizing atmosphere to obtain nanoparticle graphene oxide having functional groups selected from a group comprising alcohols (-OH), ethers (>O), aldehydes (-HC=O), ketones (>C=O), and carboxylic acids (-COOH), or a combination thereof, attached to individual layers of covalently bonded carbons atoms in the graphene oxide, wherein the thickness of graphene layers ranges from about 1 to 15.

In another embodiment, graphite is chemically beneficiated to add oxygen functional groups selected from a group comprising alcohols (-OH), ethers (>O), aldehydes (-HC=O), ketones (>C=O), and carboxylic acids (-COOH), or a combination thereof, to individual layers of covalently bonded carbon atoms. The beneficiated graphite is subjected to agitation using ultra sonicators to separate the individual layers and to obtain nanoparticle graphene oxide, wherein the thickness of the graphene layers ranges from about 1 to 15.

In an embodiment, the oxidizing agent is selected from a group comprising phosphoric acid and nitric acid or a combination thereof.

In an embodiment, the nanotization of graphite to nanotized graphene oxide, increases the surface area per volume on the nanotized graphene oxide. Increased surface area means enhanced germicidal activity. The germicidal activity includes but is not limited to bactericidal activity and fungicidal activity.

In an embodiment, during the method of preparing the composition, the stabilizing agent is added before mixing nanotized graphene oxide with filler and binder. During the preparation of the slurry, the stabilizing agent causes stable dispersion of nanotized graphene oxide in the aqueous medium.

In an embodiment, concentration of the nanotized graphene oxide ranges from about 0.3 % w/w to 5 % w/w.

In a non-limiting embodiment, concentration of the nanotized graphene oxide in the composition is about 0.3 % w/w, about 0.5% w/w, about 1% w/w, about 1.5% w/w, about 2% w/w, about 2.5% w/w, about 3% w/w, about 3.5% w/w, about 4% w/w, about 4.5% w/w or about 5% w/w.

In an embodiment, concentration of the binder ranges from about 30 % w/w to 40 % w/w.

In a non-limiting embodiment, concentration of the binder in the composition is about 30% w/w, about 31% w/w, about 32% w/w, about 33% w/w, about 34% w/w, about 35% w/w, about 36% w/w, about 37% w/w, about 38% w/w, about 39% w/w or about 40% w/w.

In an embodiment, concentration of the filler ranges from about 45% w/w to 60% w/w.

In a non-limiting embodiment, concentration of the filler in the composition is about 45% w/w, about 46% w/w, about 47% w/w, about 48% w/w, about 49% w/w, about 50% w/w, about 51% w/w, about 52% w/w, about 53% w/w about 54% w/w, about 55% w/w, about 56% w/w, about 57% w/w, about 58% w/w, about 59% w/w or about 60% w/w.

In an embodiment, concentration of the stabilizing agent ranges from about 0.03% to 0.5%.

In a non-limiting embodiment, concentration of the stabilizing agent in the composition is about 0.03%, about 0.05%, about 0.1%, about 0.15%, about 0.2%, about 0.25%, about 0.3%, about 0.35%, about 0.4%, about 0.45% or about 0.5%

In an embodiment, the method of the present disclosure further comprises step of mixing the composition with water to obtain slurry.
In a non-limiting embodiment, the water is tap water or distilled water or a combination thereof.

In a further embodiment, volume of the water added to the composition ranges from about 250 ml to 500 ml per litre of the slurry.

In an embodiment, the mixing of the composition with water is carried out at a temperature ranging from about 20°C to 60°C.

In a non-limiting embodiment, the mixing of the composition with water is carried out at a temperature of about 20°C, about 25°C, about 30°C, about 35°C, about 40°C, about 45°C, about 50°C, about 55°C or about 60°C.

In another non-limiting embodiment, the mixing is performed by mechanical stirring.
In an embodiment, pH of the slurry ranges from about 9 to 11.5.

In a non-limiting embodiment, pH of the slurry is about 9, about 9.5, about 10, about 10.5, about 11 or about 11.5.

In an embodiment, the viscosity of the slurry ranges from about 30cp to 70cp.

In a non-limiting embodiment, the viscosity of the slurry ranges from about 30cp, about 40cp, about 50cp, about 60cp or about 70cp.

The present disclosure further describes a coated article comprising-
a substrate; and
coating of the composition on the substrate.

In an embodiment, the substrate is coated with the composition on at least one surface.

In an embodiment, the inner surface or outer surface or both the surfaces of the substrate comprises coating of the composition.

In an embodiment, the substrate is selected from a group comprising pipe, tube, reservoir, tank, culverts, and walls.
In an embodiment, the substrate is composed of metals selected from a group comprising steel, zinc, tin, nickel, and chromium, or any combination thereof.

In a preferred embodiment, the substrate is a pipe, more preferably a ductile iron pipe.

In an embodiment, in the coated article, the coating has thickness ranging from about 100 microns to about 4cm

In another embodiment, in the coated article, the coating has thickness ranging from about 1cm to 2cm.

In a non-limiting embodiment, in the coated article, the coating has thickness of about 100 microns, about 500 microns, about 1000 microns, about 1500 microns, about 2000 microns, about 2500 microns, about 3000 microns, about 3500 microns, about 4000 microns, about 4500 microns, about 5000 microns, about 1cm, about 1.5cm, about 2cm, about 2.5cm, about 3cm, about 3.5cm, about 4cm, about 4.5cm or about 5cm.

In an embodiment, the coated article exhibits antibacterial property.

In an embodiment, the coating imparts germicidal activity including but is not limited to bactericidal activity and fungicidal activity to the coated article.

In another embodiment, the coating on the metallic surface of the substrate in the coated article exhibits higher germicidal activity including but is not limited bactericidal activity and fungicidal activity than that of the underlying metallic surface which have been separately been known to exhibit antibacterial property.

In an embodiment, coating on the article inhibits propagation of water borne pathogens including but is not limited to bacteria and fungi in the coated article.

In an embodiment, the germicidal activity of the coated article ranges from about 82% to 100%.

In an embodiment, bactericidal activity of the coated article ranges from about 82% to 100%.
In a non-limiting embodiment, the bactericidal activity of the coated article is about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99% or about 100%.

In an embodiment, the coated article causes reduction in cell viability by about 82% to 100%.

In a non-limiting embodiment, the coated article causes reduction in cell viability by about 82%, about 83%, about 84%, about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%, about 92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about 99% or about 100%.
In an embodiment, the coated article exhibits resistance to corrosion.

In an embodiment, the coated article has corrosion rate ranging from about 0.001 g/cm2 to about 0.009 g/cm2 per 90 days.

In a non-limiting embodiment, the coated article has corrosion rate of about 0.001 g/cm2, about 0.002 g/cm2, about 0.003 g/cm2, about 0.004 g/cm2, about 0.005 g/cm2, about 0.006 g/cm2 about 0.007 g/cm2, about 0.008 g/cm2 or about 0.009 g/cm2, per 90 days

In a further embodiment, the coated article exhibits high hardness and resistance to wear and tear.

In an embodiment, the coated article of the present invention exhibits Hazen Williams C value of about 140 when compared to uncoated article, which exhibits the Hazen Williams C value of about 100.

In a non-limiting embodiment, the coated iron pipe of the present invention exhibits Hazen Williams C value of about 140 when compared to uncoated iron pipe, which exhibits the Hazen Williams C of about 100.
Furthermore, the present disclosure provides a method of preparing the coated article.

In an embodiment, the method of preparing the coated article comprises steps of:
applying the composition to at least one surface of substrate; and
subjecting coated surface of the substrate to heating, followed by curing the coat on the substrate to obtain the coated article.

In a non-limiting embodiment, before applying the composition to at least one surface of the substrate, the substrate is subjected to cleaning with alkali and followed by rinsing with water, wherein the alkali is selected from a group comprising silicate, phosphate and caustic soda, or any combination thereof.

In an alternate embodiment, the substrate is subjected to cleaning with wetting agent/ surfactant or chelating agent or combination of both, wherein the wetting agent/ surfactant is selected from a group comprising alkylbenzene sulfonates (detergents), (fatty acid) soaps, lauryl sulfate (foaming agent), di-alkyl sulfosuccinate (wetting agent), lignosulfonates (dispersants); and chelating agents is selected from a group comprising glucamates, EDTA, etc depending on the metallic substrate.

In an embodiment, the cleaning of the substrate is performed to remove oil and dirt from the surface.

In a further non-embodiment, the cleaning is conducted at a temperature ranging from about 55°C to 65°C, for time ranging from about 2 minutes to 3 minutes.

In yet another non-limiting embodiment, the cleaning is conducted at a temperature of about 55°C, about 56°C, about 57°C, about 58°C, about 59°C, about 60°C, about 61°C, about 62°C, about 63°C, about 64°C or about 65°C and for time of about 2 minutes, about 2.5 minutes or about 3 minutes.

In an embodiment, applying the composition to at least one surface of the substrate is conducted by techniques selected from a group comprising immersing the substrate in the composition, applying the composition by brush and applying the composition by centrifugal force. or any combination thereof.

In another embodiment, the cleaned substrate including but is not limiting to pipe, such as hollow pipe is dip coated with the slurry of the present disclosure, wherein the pipe is immersed in the slurry having temperature ranging from about 70°C to 95°C.

In yet another embodiment, the slurry is placed at the center of the hollow pipe and then rotated at about 30 rpm to 150 rpm per minute for about 30 seconds to 5 minutes.

In an embodiment, the speed of rotation of the hollow pipe upon placing the pipe in the slurry is dependent on the thickness of the pipe.

In an embodiment, after applying the slurry at room temperature on at least one surface of the substrate, the substrate is subjected to heating at a temperature ranging from about 45°C to 75°C, for time ranging from about 2 minutes to 10 minutes.

In another embodiment, after applying the slurry on at least one surface of the substrate, the substrate is subjected to heating at a temperature of about 45°C, about 50°C, about 60°C, about 65°C, about 70°C or about 75°C, for a time of about 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes.

In a non-limiting embodiment, the heating is carried out by technique selected from a group comprising resistance heating and hot air heating, or a combination thereof.

In an embodiment, the curing is carried out at a temperature ranging from about 20°C to 40°C, for time ranging from about 0.5 hours to 4 hours. After curing the pipes or the coated article is subjected to complete internal drying for about 24hrs.

In a non-limiting embodiment, the curing is carried out at a temperature of about 20°C, about 25°C, about 30°C, about 35°C or about 40°C, for time of about 0.5 hours, about 1 hour, about 1.5 hours, about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours or about 4 hours.
In an embodiment, the method of preparing the coated article enables uniform coating of the composition on at least one surface of the substrate.

In another embodiment, the method of preparing the coated article enables uniform coating of the composition on inner linings of hollow cylindrical substrate.

In an embodiment, during the method of preparing the coated article, deposition rate of the composition on the substrate is sensitive to concentration, density and weight of different ingredients in the composition especially when the composition is applied using centrifugal force.

In an embodiment, the methods of the present disclosure allow for a direct coating of the composition/the slurry of the present disclosure over the metallic substrate to impart germicidal activity including but is not limited to bactericidal activity, bacteriostatic activity and fungicidal activity, instead of having to prepare a metal-graphene composite to prevent growth of pathogens.

In an embodiment, figure 1 illustrates the schematic diagram showcasing the synthesis of graphene oxide from graphite.

In an embodiment, figure 2(a) illustrates the Field Emission Scanning Electron Microscope (FESEM) image of graphene oxide on the steel substrate; figure 2(b) illustrates Transmission electron microscopy (TEM) image of powder sample obtained by scribing and figure 2(c) illustrated Selected area electron diffraction (SAED) pattern confirming crystalline graphene oxide structure.

In an embodiment, figure 3 illustrates Growth Inhibition Assay on E.coli colonies on LB agar plates over wherein (a) illustrates rich growth bacterium on coated glass substrate; (b) illustrates no growth in agar plate having coated article having steel substrate and growth observed on plate comprising bare metal; (c) illustrates no growth in agar plate having coated article having tin substrate and growth observed on plate comprising bare metal; (d) illustrates no growth in agar plate having coated article having nickel substrate and growth observed on plate comprising bare metal; and (e) illustrates no growth in agar plate having coated article having zinc substrate and growth observed on plate comprising bare metal.

In an embodiment, figure 4 illustrates viability assay. The percentage of reduction in cell viability is calculated as the viable CFU/ml over the initial CFU/ml seeded on bare substrates, such as zinc, nickel, tin, steel and coated articles of the present disclosure, such as GO.Zn (coated article having zinc substrate), GO. Ni (coated article having Nickel substrate), GO.Sn (coated article having tin substrate), GO.Steel (coated article having steel substrate) and GO.glass (coated article having glass substrate). Error bars, represent standard deviation from three independent sets of experiments.

In an embodiment, figure 5 illustrates FESEM analysis data of E. coli cells, inoculated on different surfaces of coated article of the present disclosure such as GO.Zn (coated article having zinc substrate), GO. Ni (coated article having Nickel substrate), GO.Sn (coated article having tin substrate), GO.Steel (coated article having steel substrate). The cells on the said coated articles are showing alterations in cell morphology, membrane damage and cytoplasm leakage under high and low magnifications (depicted in red arrows). However, cells on coated article having glass substrate are healthy and uniform appearing without any evidence of membrane damage (depicted in black arrows).

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in the art based upon the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the invention herein provides for examples illustrating the above described embodiments, and in order to illustrate the embodiments of the present invention, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the following examples should not be construed as limiting the scope of the embodiments herein.
EXAMPLES
EXAMPLE 1 - Preparation of Graphene Oxide
The graphite is procured from one of the graphite beneficiation plant in Odisha, India. It contains around 90% carbon and is composed of flaky particles.
The procured graphite is further subjected to grinding and floatation to enrich the carbon value up to 96-97%. It is then treated with about 1M sodium hydroxide and neutralized with dilute hydrochloric acid. During said leaching process the ultrafine gangue particles (mostly silicate minerals) go to aqueous phase in form of sodium silicate and graphite layer emerges out from the gangue minerals. Further, trace elements like calcium, magnesium and iron phase minerals are dissolved during the acid washing. The locked particle either liberates as well as behaves like hydrophobic particles after treatment.

The product obtained after leaching is further subjected to another floatation step to remove gangue particles and locked particles.
The final product (graphite) obtained after the floatation step has enhanced carbon percentage of about 99.99%.

The beneficiated graphite obtained earlier is made to undergo mechanical attrition in a specially designed planetary mill in the presence of oxygen. The planetary rotatory mill provides 2-axis rotation to enable nanotization of the graphite flakes and introduction of oxygen functional groups.

EXAMPLE 2 –Preparation of the coating composition
The coating composition is prepared by mixing 350 gms of cement and 500 gms of sand to 300 ml of water. The mixing is carried out by mechanical stirring for 0.5 hrs at 25 °C temperature. Then 0.5 gms of stabilizing agent is added to the mixture and mechanical stirring is continued for another 10 minutes at 25 °C. Finally, the slurry is completed by adding 5 gms of graphene oxide and mixing the net mixture by mechanical stirring for another 0.5 hrs at 25 °C

EXAMPLE 3 – Evaluation of anti-bacterial property of the coated article- Growth Inhibition Assay

Preparation of cell culture:
Culturing of gram-negative bacteria BL21 (DE3) and Escherichia. coli (E. coli) are started in Luria Bertani (LB) medium at temperature of about 37°C while shaking at about 200rpm. Cell harvesting is done at mid log phase (OD600~ 0.6) by centrifuging at about 5000 rpm for a time of about15 minutes at temperature of about 4°C. Upon harvesting, the cells are washed about twice with 1X PBS to remove soluble contaminants, if any. Final cell suspension is prepared in 1X PBS at about 108 CFU/ml.

Anti-bacterial/bactericidal activity testing:
About 2.5cm×2.5cm of the coated articles having substrate composed of zinc, tin, nickel, steel, iron and glass, respectively are sterilized by autoclaving at temperature of about 121°C and under about 15 lb pressure followed by exposure to UV for about 30 minutes. About 100µl cells at about 107 CFU/ml are applied on the coated articles having substrate composed of zinc, tin, nickel, steel, iron and glass, respectively and bare substrates composed of zinc, tin, steel, iron and nickel, respectively, and incubated inside sterilized petri-plates at temperature of about 37°C for about 15 minutes. Then molten agar having temperature of about 45°C is poured over the coated articles and the substrates, respectively having the cells and allowed to set at temperature of about 20°C to 40°C. The plates are incubated at temperature of about 37°C overnight and bacterial colonies are photographed on the next day. The following results are observed:

Table 1: Growth Inhibition Assay results
Sl. No. Material Incubation Temperature Bacterial Growth
1 Coated article having steel as substrate 370C No growth
2 Coated article having iron as substrate 370C No growth
3 Coated article having Zn as substrate 370C Negligible
4 Coated article having Sn as substrate 370C Negligible
Coated article having Ni substrate 370C Negligible
5 Coated article having glass as substrate 370C Copious cell growth
6 substrates composed of Steel, Fe, Zn, Sn, and Ni, respectively 370C Growth visible

The inhibitory effect of the coated metal sheets is found to be present in all the tested metals i.e. Zn, Ni, Sn, Fe and Steel. However, coated glass surface did not exhibit any such effect.
EXAMPLE 4 – Evaluation of anti-bacterial property of the coated article - Viability assay

To evaluate bactericidal nature of coated articles of the present invention, cell viability is assessed by spread plate method following exposure to coated articles for about 6 hours. Quantitation of viable cells is done by colony counting method. To subtract the effect of desiccation, the experiment is performed under constant humidity.

E. coli cells at about 107CFU/ml are incubated over sterilized coated articles of about 150µl/cm2 inside sterile petriplates at about 370C under constant humidity. The defined condition is maintained by placing the plates in a closed container with autoclaved de-ionized water channels. Cells are taken out periodically at different time points (about 0 hour, about 2 hour, about 4 hour and about 6 hour) and diluted up to about 104 fold in normal saline, followed by plating on to LB-agar plates and incubated at about 370C, overnight. Next day colonies are counted and percentage of reduction in cell viability is calculated as follows:

(CFU/ml at time t0-CFU/ml at time t) X 100
CFU/ml at time t0

The viability results are illustrated below:

Table 2: Viability assay results – 1 hour post incubation
Sl. No. Material Incubation Temperature Reduction in viable cells
1 Coated article having steel as substrate 370C 20%
2 Coated article having Fe as substrate 370C 20%
3 Coated article having Zn as substrate 370C 30% - 40%
4 Coated article having Sn as substrate 370C 30% - 40%
5 Coated article having Ni as substrate 370C 30% - 40%
6 Coated article having glass as substrate 370C 0%
7 Bare glass substrate 370C 0%
8 Bare metal substrate of steel, Fe, Zn, Sn or Ni 370C 0%

Until about 1hour time, coated article having zinc as substrate, tin as substrate and nickel as substrate showed about 30% to about 40% reduction in viability, respectively. Coated article having steel substrate and iron substrate showed about 20% reduction in cell viability, respectively.

Table 3: Viability assay results – 2 hours post incubation
Sl. No. Material Incubation Temperature Reduction in viable cells
1 Coated article having steel as substrate 370C 51%
2 Coated article having Fe as substrate 370C 51%
3 Coated article having Zn as substrate 370C 97%
4 Coated article having Sn as substrate 370C 83%
5 Coated article having Ni as substrate 370C 87%
6 Coated article having glass as substrate 370C 0%
7 Bare glass substrate 370C O%
8 Bare metal substrate of steel, Fe, Zn, Sn or Ni 370C O%

After about 2 hours of incubation, the coated article having zinc as substrate showed about 97% reduction in cell viability, the coated article having nickel as substrate showed about 87% reduction in cell viability, the coated article having tin as substrate showed about 83% reduction in cell viability and the coated article having steel as substrate and iron as substrate showed about 51% reduction in cell viability, respectively. Further, bare metal substrate of Steel, Fe, Zn, Sn or Ni and bare glass substrate showed no reduction in cell viability.

Table 4: Viability assay results – 6 hours post incubation
Sl. No. Material Incubation Temperature Reduction in viable cells
1 Coated article having steel as substrate 370C 82%
2 Coated article having Fe as substrate 370C 82%
3 Coated article having Zn as substrate 370C 100%
4 Coated article having Sn as substrate 370C 100%
5 Coated article having Ni as substrate 370C 100%
6 Coated article having glass as substrate 370C 0%
7 Bare glass substrate 370C 0%
8 Bare metal substrate
of steel, Fe, Zn, Sn or Ni 370C 0%

After about 6 hours of incubation, the coated article having steel as substrate or iron as substrate showed about 82% reduction in cell viability, respectively. Coated article having zinc as substrate, tin as substrate and nickel as substrate showed about 100% reduction in cell viability, respectively. However, coated article having glass as substrate showed no reduction in cell viability. Further, bare metal substrate of Steel, Fe, Zn, Sn or Ni and bare glass substrate showed no reduction in cell viability.

EXAMPLE 5 – FESEM Analysis of bacterial growth on coated articles
In order to mimic the infections in households and in hospital set up, bacterial cells such as E. coli and BL21 (DE3) are seeded onto coated articles of the present disclosure after which they are provided with a nutrient rich medium to promote growth of cells. Next day, cell growth in the form of colonies is analyzed as a measure of antibacterial activity. Coated article having zinc as substrate, tin as substrate, nickel as substrate, iron as substrate and steel as substrate showed no growth of bacterial cells. However, coated article having glass as substrate displayed copious cell growth. These results signify that coated article of the present disclosure exhibit a superior antimicrobial activity as compared to bare metal sheets.
In addition, it is noticed that coated article demonstrated higher inhibitory effect relative to the corresponding bare metals, consistent with the growth inhibition results.