WO2009015493A1

WO2009015493A1 - Compositions comprising carbon coated, non-noble metal nanoparticles

Info

Publication number: WO2009015493A1
Application number: PCT/CH2007/000372
Authority: WO
Inventors: Evagelos Athanassiou; Norman A. Lüchinger; Wendelin Jan Stark
Original assignee: Eth Zurich
Priority date: 2007-07-27
Filing date: 2007-07-27
Publication date: 2009-02-05

Abstract

The present invention relates to compositions comprising carbon-coated non-noble metal nanoparticles, a liquid carrier and a dispersing additive; to the manufacture of such compositions; to devices containing such compositions; to the manufacture of such devices and to uses of such compositions and devices. The compositions disclosed are stable when exposed to air or to chemical treatment.

Description

Compositions comprising carbon coated, non-noble metal nanopartides

The present invention relates to dispersions and ink formulations ("compositions") of carbon-coated non-noble metal nanoparticles, to the manufacture of such compositions, to devices containing such compositions, to the manufacture of such devices and to uses of such compositions and devices. The compositions disclosed are stable against oxidation by air ("air-stable") or by chemical treatment.

Numerous attempts are known to achieve metallic gloss on surfaces and / or to manufacture lacquers / inks having electrical conductivity. Often, noble metals (such as silver colloids) are used to achieve these objectives. As such compositions are expensive, there is a need for alternatives. It is therefore a technological incentive to prepare similar decorative or electrically conducting surfaces using low-cost materials. As copper is used in large quantities for the manufacturing of electronics, it has been attempted many times to deposit copper in the form of conductive inks or as decorative surfaces. Examples include copper based metal organic inks¹⁶' ¹⁷ or polymeric copper dispersions¹⁸ applied on glass or plastic surfaces by various printing techniques. Unfortunately, these methods of printing copper based inks suffer from the instability of the nanoparticles towards air/oxidation. Due to the small size the copper rapidly reacts with air resulting in copper oxide layers having low conductivity and/or low decorative value .

Schulz et. al.¹⁵ therefore use complex and toxic modification chemistry to remove such oxide layer prior to deposition. Such techniques are regarded unsuitable for large scale production and are expensive. Cook et. al.¹⁷ describe the printing of copper hexanoate and the manufacturing of resulting copper lines. Such material can be used to print copper but suffers from very poor line quality and limited feature size.

Rickerby et. al.¹⁸ describe the use of hexafluoro-acetyl-acetone- Cu (I) poly-vinyl siloxanes as precursor for the deposition and writing of copper. While the authors managed to deposit copper the method suffers from toxic chemistry and the use of expensive materials. Further, the deposition shows a strong tendency of hollowing. This makes deposition of defined pattern a difficult and/or costly issue.

WO2005/044451 describes a method for electroless plating of metals using direct-write technologies. A substrate is selectively coated with metallic copper by depositing a reaction solution of palladium ions and a reducing agent on the surface by ink-jet printing. The reaction is aided by the presence of an activator, which may be deposited also by ink-jet printing. The palladium film is further used as a catalyst for a second metal deposition reaction of copper. Main drawbacks of this process are the control of the thickness of the catalyst layer as thick layers have the tendency to de-laminate from the substrate due to induced stresses and that it concerns a time- intensive multi-step preparation process (3 different layers applied by ink-jet printing on a single surface).

WO03/038002 discloses a method for the deposition of metals on surfaces involving the use of simultaneous reduction and delivering of a reducible metal precursor. This document speculates on the use of copper nanoparticles for coatings having a high electrical conductivity. The exemplified coatings have a conductivity of about 0.002 S/cm only.

However, the process described herein is considered costly, unsuitable for large scale production and only provides low particle concentrations . US2006/0225533 describes paints or inks containing aluminum flake pigments and its use for manufacturing decorative surfaces using such inks / paints. The use of aluminum flakes allows excellent metallic luster, fine graininess and plating-like appearance resulting in a high decorative value of such coatings. Unfortunately, the use of flakes with several micron diameter results in a material that still shows graininess. It would be an incentive to prepare such surfaces with a completely smooth and metal-like appearance. However, such effect is not accessible through aluminum flakes, or metal flakes in general, having a diameter of up to several microns due to light scattering. Such effect therefore requires the use of particles that are considerably smaller than the wavelength of light. However, reducing particle size to the nanometer region results in incredible reactivity of such nanoparticles against air.

Athanassiou et. al.² describe the preparation of carbon-coated copper nanoparticles that are air-stable and their subsequent application for the manufacturing of pressure and temperature sensing materials. This document, however, does not disclose any liquid composition nor any use in relation to liquid compositions.

Luechinger et. al.¹⁹ describe porous metal films and their application for optical humidity sensing. This document discloses use of such paint or printable copper- based porous films as ultra-low cost optical humidity sensors. The document further describes the preparation of stable dispersion of carbon-coated copper in water using specific dispersion agents (BYK 348 and Disperbyk 190). No reference is made for electrical properties of these films beyond color changes of the material upon exposure to solvent or water vapor. The disclosed compositions are not wear-resistant, e.g. they can be rinsed off with water and are therefore considered unsuitable for commercial applications . WO2007/028267 discloses carbon coated nanoparticles and their manufacturing. The nanoparticles have preferable primary particle sizes of .10 - 50 nm, most preferred 20 - 50 nm and exhibit high air stability. However, this document fails to disclose suitable inks / laquers that can be readily applied. Further, no specific uses of the described compositions are provided.

Thus, it is an aim of the present invention to provide compositions that overcome one or more of the above identified problems and to provide corresponding manufacturing processes. It is a further aim of the present invention to provide devices fully or partly coated with the compositions as described herein and to provide corresponding manufacturing processes. Further, it is an aim to provide new uses and applications of the compositions and devices as disclosed herein.

These objectives are achieved by a composition as defined in claim 1, by the devices and manufacturing process and uses as defined in the independent claims. Further aspects of the invention are disclosed in the specification and independent claims, preferred embodiments are disclosed in the specification and the dependent claims.

The present invention will be described in more detail below. It' is understood that the various embodiments, preferences and ranges as provided / disclosed in this specification may be combined at will. Further, depending on the specific embodiment, selected definitions, embodiments or ranges may not apply.

Unless otherwise stated, the following definitions shall apply in this specification: The term nanoparticles is known in the field. In particular, nanoparticles are particles having a diameter in the submicron size range and can be either crystalline or amorphous. Such nanoparticles have preferable primary particle sizes of 10 - 50 nm, most preferred 20 - 50 nm of an agglomerate size measured as hydrodynamic particle size distributions below 200 nm. Suitable methods for the determination of primary particle sizes and agglomerate diameter can be found by Limbach et. al . ^x

The term non-noble metal is known in the field. In particular, it denotes metals or metal alloys, in particular metals. The metal (s), either alone or in an alloy, have a standard potential between +0.52 and -0.41 V as defined in Riedel 1999³. Copper is the most electropositive metal within the context of the present invention. Suitable meals are, for example, Cu, Mo, Ni, Co in particular Cu. Suitable alloys are, for example, Ni-Mo, Cu- Ni, Co-Ni.

The term carbon-coated non-noble metal nanoparticles denotes nanoparticles of a core-shell type where the core consists of a non-noble metal as defined above. Such non-noble metal nanoparticles are protected against oxidation by air through deposition of a carbon- coating (the "shell") on their surfaces. Suitable carbon- coatings consist of at least one graphene layer and can contain up to several dozen graphene layers. Most suitable coatings consist of 3 - 10 graphene layers reaching layer thicknesses of 1 - 5 nm carbon. Such coatings are sufficient to protect the non-noble metal core against spontaneous ignition (pyrophoric) or oxidation, e.g. by air or chemical treatment.

In a first aspect, the invention relates to a composition comprising (i.e. containing or consisting of) carbon-coated non-noble metal nanoparticles; liquid carrier; dispersing additive.

Without being bound to theory, it is believed that the thin carbon coating protects the non-noble nanoparticles from oxidation by air or chemical treatment. Such compositions are sometimes referred to as "dispersion" or "ink".

The compositions as described herein may be directly used as a dispersion (e.g. for decorative purposes) or as an ink (e.g. for manufacturing an electrically conductive substrate / surface or printed circuit) . Alternatively, customary additives, such as viscosity modifiers, fillers, colorants, humectants, adhesion promoters, may be added to fine-tune the properties of the dispersion / ink to the desired substrate / surface and/or the intended manufacturing process.

In an advantageous embodiment, the metal is selected from the group consisting of Cu, Mo, Ni, Co, in particular Cu. It was found that these metals show particular beneficial optical, electrical and magnetic properties and/or stability. Further, nanoparticles of these metals result in a very robust carbon coating, particular Co and Cu.

In an advantageous embodiment, the carrier contains at least 50 wt-% water, in particular at least 90 wt-% water. Purified water is preferred, for example having an electrical resistivity of > 18MΩcm.

In an advantageous embodiment, provided the carrier contains at least 50 wt-% water, the dispersing additive is a tenside with at least one hydrophilic and one lipohilic group. Advantageous tensides are those, wherein the lipophilic group is selected from the group consisting of aromatic groups (such as styrene-based groups), saturated, unsaturated or partly unsaturated aliphatic groups, siloxane based groups, fluoro-carbon based aliphatic groups. Advantageous tensides are further those, wherein the hydrophilic group contains one or more functional moieties selected from the group consisting of sulphonates, phosphonates, substituted and unsubstituted ammonia, hydroxy, hydroxy- (poly) ether (such as glycols), carboxylic acids and its salts. Examples of useful additives for water- based compositions include: Disperbyk, Disperbyk-190 Disperbyk-180, Disperbyk-190, Disperbyk-170, Disperbyk-140, BYK-154, BYK-162, BYK-180, BYK-181, BYK-190, BYK-192, BYK- 333, BYK-348, SMA 1000NA, SMA 100OH, SDS, AOT, Tamol, T1124, Tween 20, Tween 80, L-Il, Betaine, Sodium Laureth Sulfosuccinate and Sulfate, Tego 735W, Tego 740 W, Tego 750 W, Disperbyk, PDAC (poly (diallyldimethylammonium chloride)), Nonidet, CTAC, Daxad 17 and 19 (sodium salt of naphthalene sulfonate formaldehyde condensate), BASF 104, Solspers 43000, Solspers 44000, Atlox 4913, PVP K-30, PVP K-15, Joncryl 537, Joncryl 8003, Ufoxan, STTP, CMC, Morwet, LABS W-100A, Tamol 1124

In an advantageous embodiment, provided the carrier contains at least 50 wt-% water, the composition further contains a humectant. Humectants are known in the field, suitable humectants for water-based compositions include: PMA, glycerol, DPM, diethylene glycol, SuIfolam, triethanolamine, Dowanol DB, DMF (dimethyl formamide) , isopropanol, n-propanol, PM (l-methoxy-2-propanol) , Diglyme (di (ethylene glycol) diethyl ether), NMP (1-methyl pyrrolidinone) .

In an alternative advantageous embodiment, the carrier contains at least 50 wt-% organic solvent, preferably at least 90 wt-% organic solvent.- Such organic solvent is advantageously selected from the group consisting of alcohols (including glycols), ethers, esters, ketones, glycols or combinations thereof. Examples of organic solvents include: ethanol, DPM (di (propyleneglycol) methyl ether), ethyleneglycol, PMA (1, 2-propanediol monomethyl ether acetate) , 2-butoxyethanol, n-butanol, 2-ethylhexanol and its mixtures.

In an advantageous embodiment, provided the carrier contains at least 50 wt-% organic solvent, the dispersing additive is a dispersing polymer. Advantageous dispersing polymers are selected from the group consisting of a PVP polymer, an acrylic polymer, a PVP co-Polymer, an acrylic copolymer and mixtures thereof. Examples of useful additives for solvent-based compositions include: BYK-9077, Disperbyk-163, PVP K-15.

The compositions (dispersions/inks) may be applied on substrates (i.e. to the surface of a substrate) by a variety of methods such as by roll coating, drop on demand printing techniques, gravure printing, planographic printing, offset printing screen printing, most preferred by ink-jet printing or brush applications as described in further detail below. There is a wide range of possible substrates including flexible, rigid, elastic ones. Specific examples include paper, polymer films, textiles, plastics, glass, fabrics, printed circuit boards, epoxy resins, ceramic and metallic substrates.

In a second aspect, the invention relates to a method for manufacturing a composition as described herein, comprising the steps of combining at least one liquid carrier and at least one dispersing additive until a homogeneous phase is obtained; dispersing the nanoparticles as defined herein until a stable dispersion is obtained; optionally removing agglomerates and/or other impurities from the obtained dispersion. The individual steps of this process are known in the field. The first step, obtaining a homogeneous phase from a carrier and one or more dispersing additives may be achieved by using standard laboratory / manufacturing equipment, such as a conventional stirrer or ultrasonication. Typically, the additive is added to the stirred carrier. The third step, removal of impurities, is also known in the field, and may be achieved by filtration or centrifugation, preferably by centrifugation.

In an advantageous embodiment, the invention relates to a method as described herein, wherein the stable dispersion is obtained by means of ultrasonication. To include an ultrasonication step for dispersing the nanoparticles (2^nd step of the method as described above) , either alone or in combination with conventional mixing, provides very stable dispersions.

In a third aspect, the invention relates to a device (article) consisting of: at least a substrate and a further layer comprising a composition as described herein. It is further understood that said article may contain additional layers below said layer (e.g. a primer) or on top of said layer (e.g. a protection layer or other functional layer) . Thus, the invention relates to a device / article partly or fully coated with a composition as described in the "first aspect". Said device / article may have a number of applications as further described in this specification.

In one embodiment, the device / article comprises a substrate ; a first layer comprising either an amorphous polymer layer or a mixture of a polymer and a surface-active additive; a second layer comprising a composition as described herein; whereby said second layer is directly adjacent to said first layer. The polymers of the first layer may be amorphous, crystalline or partly crystalline. The terms are known in the field; such properties may be identified according to standard processes. It is believed that additives are not necessary when amorphous polymers are used; this is attributed to the smooth surface of amorphous polymers. In turn, when crystalline or partly crystalline polymers are used, additives are beneficial. Acrylic based polymers are a typical example for amorphous polymers. Polyether modified silicon tensides, fluoro-carbon tensides or modified acrylic tensides are typical examples of suitable additives in this context. It is further understood that said article may contain additional layers below said first layer (e.g. a primer) or on top said 2^nd layer (e.g. a protection layer or other functional layer) . The use of a 1^st layer as described herein results in articles with an improved wear resistance. At the same time, it is possible to maintain the beneficial optical and electrical properties of the coating. Furhter, it is possible to manufacture such articles with standard equipment, making it suitable for large scale production.

In an alternative embodiment, the substrate and first layer of the article as described herein are identical. Consequently, the invention relates to an article, wherein the substrate comprises or consists of an amorphous polymer layer or a mixture of a polymer and a surface-active additive; and a layer comprising a composition as described herein; whereby said layer is directly adjacent to the substrate . It was surprisingly found that a composition as described herein may be directly applied to a substrate having all the beneficial properties as described above, in particular wear resistance, high gloss and electrical conductivity. Articles made of such specific substrates are in particular suitable for mass production. It was found that a polymer layer results in a substantially improved coating of a substrate when the applied composition is additionally heated. The thus obtained devices / articles are substantially stable against removal with water ("water proof"),, they are substantially stable against mechanical stress ("wear resistant", no wipe- off with finger) , they show a homogeneous gloss ("mirror- type") and a very high distinctiveness of image (DOI) . This can be measured quantitatively by measuring diffuse scattering reflectivity. A suitable measurement for such surfaces includes measuring the intensity of the reflected light under specific angles. Such measurement is preferably done on a surface of more than 3 cm² and on several spots. Suitable instruments to measure the quality of such surfaces are Gardco glossmeters (Micro-Wave-Scan) according to DIN EN ISO 2813, DIN 67530.

In an advantageous embodiment, the invention relates to a device as described herein wherein the substrate/article is a chassis or body of a vehicle or of a consumer electronics device or a part thereof. The term vehicle in the context of this invention relates to any vehicle suitable for transportation of humans or goods, such as cars, trucks, bikes, motorbikes, planes, ships, submarines, in particular chassis or rims of a car. The term consumer electronics device in the context of this invention relates to all electrical equipment used in private, commercial and public environment, such as phones (in particular mobile phones), home electronics (such as mobile players or TV sets) , kitchen equipment, surgical equipment and the like.

In principle, any surface of a device / article may be coated with a composition as described herein. Particular suitable substrates are selected from the group consisting of glass, plastic, metal, paper, textile, ceramic, polymer, rubber, wood materials and the like as well as circuit boards.

Decorative surfaces on devices / articles obtainable by the use of this invention are characterized by complete loss of graininess where the unaided human eye can not distinguish any features in the here accessible surfaces. Such surfaces have been called liquid metal surfaces since they can not be distinguished from molten metal or liquid mercury. Such reflectivity can be measured quantitatively by measuring diffuse scattering. A suitable measurement for such surfaces would include measuring the intensity of the reflected light under specific angles. Such measurements should be done on a surface of more than 3 cm² and on several spots . Suitable instruments to measure the quality of such surfaces are Gardco glossmeters (Micro-Wave- Scan) according to DIN EN ISO 2813, DIN 67530. The surface of such liquid metal decorative coating appears feature-less e.g. shows a homogeneous smooth surface. Such surfaces appear to the unaided eye like highly polished metal surfaces. Typically, no further process steps, e.g. polishing, are required to obtain the desired surface appearance. In contrast to this, currently existing flake- based pigments show clear features under a conventional optical microscope or when any of the above methods is applied.

In a fourth aspect, the invention relates to a method of manufacturing a device as described herein ("third aspect") comprising the step of optionally applying a first layer as described herein on a substrate and applying a second layer, said layer comprising a composition as described herein, on top of said first layer. It was found that the application of said first and second layer may be accomplished by any suitable method known in the art ("conventional application method") . Further, standard equipment may be used. These methods include, for example hydraulic or pneumatic or electrostatic spray coating methods .

In an advantageous embodiment, the second layer is applied after the first layer is substantially or fully dried. In a further embodiment, the coated device is subjected to an additional drying step. Drying conditions, for first and second layer, in particular time / temperature may vary on the polymer used, the thickness of said layer and the material of the substrate. Such conditions may be determined by routine experiments. Typical condition are drying temperatures between r.t. and 200⁰C, preferably between 50⁰C and 150⁰C. Drying times may vary between one second and one hour, preferably between lOsec and lOmin.

In a fifth aspect, the invention relates to an electrical circuit consisting of a composition as described herein which is deposited, in particular printed, on a substrate. Said substrate may be optionally coated with a polymer layer prior to deposition of the composition as described herein. Said polymer layer is preferably a "first layer" as described above.

The present invention thus provides electrically conductive surfaces based on copper or other non-noble metal nanoparticles that are carbon^coated. Such surfaces being accessible by known deposition techniques, such as conventional ink-jet printing, spray techniques, lithography, drop on demand, roll coating, gravure printing, letter-less printing, planographic printing, offset printing, screen printing or brush application. Such electrically conductive layers are characterized by the ease of handling during manufacturing, e.g. no protection against air is required during preparation in any step and no precautions against ignition have to be taken during preparation because these non-noble metals are protected against its pyrophoric nature by the suitable carbon layer. Such electrically conductive layers are further characterized by a high stability against abrasion and stability against wash-off by water. Further, such layers are characterized by an electrical conductivity of above 1 S/cm.

Electrically conductive metal layers up to now have been prepared on the basis of silver and gold nanoparticles . Examples of such processes and inventions are numerous and described e.g. '^'in ^4"15. Dispersions containing gold nanoparticles are mainly stabilized by thiolorganic⁶ components whereas in silver based inks, the nanoparticles are coated by polymers⁹' ¹⁰' ¹²' ¹³' ¹⁵ to avoid agglomeration. Further various spray¹⁶, lithographic⁶ or printing techniques such as ink-jet⁸' ^{10/ 13} and direct-printing¹⁵ are used to print conducting lines or wires on glassy, or polymer-based surfaces. An additional heating treatment is used to improve the electrical properties of the conducting lines. The use of silver and gold nanoparticles for the manufacturing of such surfaces results in high quality materials but suffers from inherently high raw material costs. The present invention therefore provides alternative conductive layers and electrical circuits based on electrically conducting ink-jet printable patterns.

In a sixth aspect, the invention relates to the manufacture of an electrical circuit as described herein comprising the step of printing a desired pattern on a substrate.

The compositions as described herein can be applied using ink-jet printers and other printing technologies and result in electrically conductive layers on various substrates. The thickness of the layers can be varied by printing specific patterns several times. This method is considered very versatile and cost-efficient when compared to standard technologies.

Such patterns are applicable for flexible electronic or ultra low-cost electronic or sensing devices.

In a seventh aspect, the invention relates to an optical sensor, to the manufacture of such a sensor and to the use of compositions as described herein for the manufacture of such sensors.

The use as a humidity sensor is based on the change in color of the dried metallic film as described herein upon exposure to certain conditions, in particular vapor pressure of water or volatile organic substances, such as solvent vapors. It is believed that the coloration mechanism is attributed to the formation of a thin interference layer on top of the metallic film when the humidity or the solvent vapor concentration is increased. This interference layer consists of a mixture of the additive and water (or solvent vapor respectively) . Depending on the humidity or solvent vapor concentration the thickness of the interference layer changes causing a change in the resulting coloration.

A suitable composition described herein for the manufacture of an optical sensor comprises at least one surface active additive with a melting temperature lower than 20 °C and a high affinity for water or solvent vapors. A suitable surface active additive with a melting point lower than 20⁰C can be a polyether modified silicone tenside. Such additives are also called slip-additives, leveling agents, wetting agents. For examples of compositions suitable for the manufacture of a humidity or solvent vapor sensor see example 1 and example 2. The ink suitable for the manufacture of an optical sensor is applied on a substrate such as glass or on a polymer with a very low surface roughness (i.e. amorphous polymers) .

The ink can be applied using ink-jet printing, spray techniques, lithography, drop on demand, roll coating, gravure printing, letter-less printing, planographic printing, offset printing, screen printing or brush application.

After application on a smooth substrate the composition is dried, preferably at room temperature, which results in a film with metallic luster and high reflectivity.

Such humidity or vapor sensing films are typically not wear-resistant. It is therefore beneficial to protect such films by a transparent spacer from any undesired mechanical contact.

A sensitivity of over 50 nm color change per % relative humidity (RH) can be obtained allowing measuring accuracies well below +/- 0.5 % RH when the color is determined by an optical spectrometer. Commercial low-cost humidity sensors in contrast have a low accuracy of +/- 2 % relative humidity (R. H.).

This new type of humidity or solvent vapor sensing allows the manufacture of highly sensitive and ultra-low cost sensors without a need of an electric circuit, a display or an energy supply.

Suitable applications of such printable or paintable sensors could be in food packaging, consumer goods or pharma industry. Furthermore an application is possible in fluid dynamics visualization for the aerodynamic shape optimization of a vehicle as in automotive or aviation industry.

In an eighth aspect, the invention relates to the uses / method of use of a composition as described herein and to the uses / methods of use of devices as described herein. The uses of the compositions basically become apparent when reading the specification. Particular uses of the composition as described herein are the manufacturing

• a decorative coating

• a conductive ink

• a RFID tag

• a sensor

• a humidity sensitive device

• a solvent sensitive device.

• a transistor

In one embodiment, composition as described herein can be used as a base material for the preparation of decorative coatings . Such coatings can be made by appropriate spraying of the ink or lacquer on the surface of polymers, glass or metal substrates. The decorative patterns show high reflectivity and uniformity, in particular when applied on substrates with low surface roughness.

These dispersions/inks as disclosed herein may be applied by various methods on surfaces of substrates^' and ^• find numerous industrial applications including the following

• electronic-circuit-free optical humidity sensors, suitable for food and pharma storage, packaging, handling

• organic solvent chemical sensors, suitable for detection of organic solvents or for visualization of gas fluid dynamics in shape optimization of vehicles or airplanes. • printable electronics for the manufacture of printable displays, photovoltaics, radio frequency identification tags (RFID tags), computer memory devices, electronic circuits, processors, photodiodes, high electron mobility transistors (HEMTs) , semiconductor field-effect transistors, printable electronic spools, printable hard-drives .

• decorative substrates / surfaces exhibiting metallic gloss in automotive industry.

Further, these dispersions/inks as disclosed herein may be used in numerous industrial applications including the following:

• as a replacement for metal coatings on non-metal surfaces;

• as a decorative coating on metal substrates.

• as a fiber coating for clothing manufacturing.

• as a paint;

• as a magnetic black ink in printing industry;

• as infrared (IR) light reflecting devices;

• as ultra-violet (UV) protective devices ;

• as a nail polish in cosmetics;

• as a marine antifouling coating.

Examples

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. The examples given below are intended to further illustrate the invention, without any intend to a limitation.

All following examples consist of the following steps: i) Preparation of the non-noble metal carbon coated nanoparticles ii) Preparation and application of the metal based ink

I. Preparation of the carbon coated metal nanoparticles

The preparation of the carbon coated non-noble nanoparticles is known and described e.g. in WO2007/028267 which is incorporated by reference, in particular example 14 and fig. 20. In summary a stable non-noble metal precursor is dispersed by an oxygen jet (e.g. 5 1/min) in a flame under a nitrogen atmosphere. The flame is encased in a sinter metal tube. This tube is used for cooling of the flame with a mixture of nitrogen (e.g. 30 1/min) and acetylene (e.g. 51/min) . The application of acetylene promotes the formation of the carbon coating round the particles. Suitable carbon coated nanoparticles to be used in the context of this invention are also obtainable from a range of other preparation methods, such as liquid phase chemical methods, described e.g. in ²⁰' ²¹ which are incorporated by reference.

II. Preparation and application of the metal based ink.

Example 1 (H20 sensor)

A dispersion was prepared consisting of 7.9 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Milipore, electrical resistivity > 18 MΩcm) and a high-molecular-weight, block-copolymeric additive with acidic, pigment-affinic groups (8.3 wt % relative to C/Cu, Disperbyk 190, BYK Chemie) and an amphiphilic silicon tenside (11.7 wt % relative to C/Cu, BYK 348, a polyether- modified poly (dimethyl siloxane) ) . The dispersion was prepared by manually mixing the 2 additives with the deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra- sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles. The dispersion was applied onto glass using a brush. On glass the obtained copper films exhibited high metallic luster.

The glass was placed in a closed glass chamber. By addition of 0.1 ml water soaked cotton balls containing various concentrations of MgCl2 (_aqj (21.6 wt%-25.6 wt%, Magnesium chloride purum, Fluka-Chemie AG) resulted in the formation of different levels of relative humidity (R. H.) (73.8-63.7 % R. H.) in the closed glass chamber. This resulted in a coloration of the copper film. For each humidity level the color changed for a certain amount. The coloration mechanism is attributed to the formation of a thin interference layer on top of the metallic film when the humidity is increased. This interference layer consists of a mixture of the silicone tenside and water. Depending on the humidity the thickness of the interference layer changes which causes a change in the resulting coloration.

Example 2 (H2O sensor)

The procedure of ex. 1 was followed. The obtained coated glass was placed in a closed glass chamber. By addition of 0.1 ml water soaked cotton balls containing various concentrations of NaCl _(aq) (25.9 wt%-18.5 wt%, • sodium chloride purum, Fluka-Chemie AG) resulted in the formation of different levels of relative humidity (R. H.) (76.2-85.6 % R. H.) in the glass chamber. For each humidity level the color changed for a certain amount. A sensitivity of over 50 nm color change per % relative humidity was obtained around 70-80% RH which was determined by UV/Visible optical spectroscopy (Shimadzu UV/visible Spectrophotometer, UV-1650PC, 2mm aperture, 5° incident radiation angle, 25 ⁰C) . This resulted in a rapid and reversible coloration, readily visible by the human eye.

Example 3 (solvent sensor)

A dispersion was prepared consisting of 7.2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Millipore, electrical resistivity > 18 MΩcm) and a high-molecular-weight, block-copolymeric additive with acidic, pigment-affinic groups (7.7 wt % relative to C/Cu, Disperbyk 190, BYK Chemie) and an amphiphilic silicon tenside (10.5 wt % relative to C/Cu, BYK 348, a polyether- modified poly (dimethyl siloxane) ) . The dispersion was prepared by manually mixing the 2 additives with the deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra- sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles.

The dispersion was applied onto glass using a brush. On glass the obtained copper films exhibited high metallic luster. Exposure of the glass to a stream of ethanol (Ethanol purum, 96%, Fluka-Chemie AG) vapor resulted in rapid and reversible coloration.

This resulted in a rapid and reversible coloration, readily visible by the human eye.

Example 4 (conductive layer)

A dispersion was prepared consisting of 4 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water and 10 % of the anionic surfactant SDS relative to the C/Cu nanoparticles. The dispersion was prepared by manually mixing the dispersing agent SDS with deionized water (Millipore, electrical resistivity > 18 MΩcm) , then adding the carbon coated copper nanoparticles . The nanoparticles were dispersed by ultra-sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles. The dispersion was printed in a Hewlett-Packard Deskjet 2360 ink-jet printer on glossy photo paper (HP Premium Plus Photo Paper) . The printed pattern produced hereby is printed several times to increase the printed film thickness and electrical conductivity.

Example 5 (decorative coating)

A dispersion was prepared consisting of 2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Millipore, electrical resistivity > 18 MΩcm) and 10 % of the non-ionic surfactant BYK-348 relative to the C/Cu nanoparticles. The dispersion was prepared by manually mixing the dispersing agent BYK-348 with deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra-sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles .

The dispersion was printed in a Hewlett-Packard Deskjet 2360 ink-jet printer on glossy photo paper (HP Premium Plus Photo Paper) , on overhead projector transparencies (laser/copier transparencies, Type C, Xerox) . The dispersion was also applied onto glass and steel using an airbrush gun (HP-101, Conrad electronics) , a brush or a spreading knife. On glass and overhead transparencies the obtained copper films exhibited high metallic luster and a mirror-like appearance.

On steel, the obtained copper films exhibited a characteristic metallic color, but no mirror-like appearance .

Example 6 (decorative layer)

A dispersion was prepared consisting of 12 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Millipore, electrical resistivity > 18 MΩcm) and 5 % of the cationic surfactant SMAlOOOH (sartomer, www.sartomer.com) relative to the C/Cu nanoparticles. The dispersion was prepared by manually mixing the dispersing agent with deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra-sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminant like dust particles. The dispersion was printed,., i-n a Hewlett-Packard Deskjet 2360 thermal ink-jet printer on glossy photo paper (HP Premium Plus Photo Paper) .

The obtained copper film exhibited a characteristic metallic color, but no mirror-like appearance .

Example 7

The dispersion of example 3 containing 12 wt% carbon coated copper nanoparticles and 5 wt% SMA 1000 H relative to the C/Cu nanoparticles was further modified by manually admixing 0.13 % by weight (1.1 wt% relative to C/Cu) of the radically curable wetting agent- BYK UV 3530 for the enhancement of substrate wetting.

After the addition of the wetting agent the dispersion was applied onto glass and steel using application methods such as an airbrush gun (HP-IOl, Conrad electronics), a brush or a spreading knife.

On glass, the obtained copper films exhibited high metallic luster and a mirror-like appearance. On steel, the obtained copper films exhibited a characteristic metallic color, but no mirror-like appearance.

Example 8

The dispersion of example 4 containing SMA 1000 H dispersing agent and BYK UV 3530 uv-curable wetting agent was modified by 30 wt% EG (ethylene-glycol) in order to lower the evaporation rate of the dispersion.

After the addition of the wetting agent the dispersion was applied onto glass and steel using application methods such as an airbrush gun (HP-101, Conrad electronics), a brush or a spreading knife.

Example 9

A dispersion was prepared consisting of 7.2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Milipore, electrical resistivity > 18 MΩcm) and 4.5 % of the cationic surfactant SMAlOOOH (sartomer, www.sartomer.com) relative to the C/Cu nanoparticles. The dispersion was prepared by manually mixing the dispersing agent with deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra-sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminant like dust particles. Then 3 wt% of the silicone tenside (BYK 348 ) was added relative to C/Cu. This resulted in improved substrate wetting.

The obtained ink was applied onto a polymeric substrate using a spreading knife with a gap of 24 microns. In more detail the polymeric substrate was a film of a transparent resin with high gloss (Bricacryl Acryl-Klarlack, www.farbladen.ch) which was applied on a sheet of steel 2 days in advance using a spreading knife with a gap of 50 microns. A heat gun (Steinel HG 3000 SLE, 2000W) was used in order to accelerate the evaporation of water of the wet and black ink film. During the drying process the air temperature at the position of the ink was kept 70⁰C for about 30 seconds and afterwards HO⁰C for about 15 seconds. The resulting copper film exhibited high metallic gloss and a mirror-like appearance. By using an increased drying temperature the copper film became more wear-resistant and rigid compared to a copper film of the same ink applied directly on a glass substrate.

The copper film exhibited a dark layer (very thin tenside film) on the surface resulting in a reduced gloss and reflectance. By rubbing the copper film with woven cotton, the dark layer could be removed which caused a higher reflectance and gloss.

Example 10

A dispersion was prepared consisting of 7.2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267 ) in deionized water (Milipore, electrical resistivity > 18 MΩcm) and a high-molecular-weight, block-copolymeric additive with acidic, pigment-affinic groups (7.7 wt % relative to C/Cu, Disperbyk 190, BYK Chemie) and an amphiphilic silicon tenside (10.5 wt % relative to C/Cu, BYK 348, a pόlyether- modified poly (dimethyl siloxane) ) . The dispersion was prepared by manually mixing the 2 additives with the deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra- sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles. The obtained ink was applied onto a polymeric substrate using a spreading knife with a gap of 24 microns. In more detail the polymeric substrate was a film of a transparent resin with high gloss (Bricacryl Acryl- Klarlack, www.farbladen.ch) which was applied on a sheet of steel 2 days in advance using a spreading knife with a gap of 50 microns. A heat gun (Steinel HG 3000 SLE, 2000W) was used in order to accelerate the evaporation of water of the wet and black ink film. During the drying process the air temperature at the position of the ink was kept 70⁰C for about 30 seconds and afterwards 110⁰C for about 15 seconds. The resulting copper film exhibited high metallic gloss and a mirror-like appearance. By using an increased drying temperature the copper film became more wear-resistant and rigid compared to a copper film of the same ink applied directly on a glass substrate. Compared to Example 10 the copper film is more glossy, has a higher reflectance and exhibits no greyisch and darkening layer.

Example 11

A dispersion was prepared consisting of 7.2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Milipore, electrical resistivity > 18 MΩcm) and 4.5 % of the cationic surfactant SMAlOOOH (sartomer, www.sartomer.com) relative to the C/Cu nanoparticles. The dispersion was prepared by manually mixing the dispersing agent with deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra-sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles. The examples 12 - 20 all contain inks which are prepared from the ink in example 11 (7.2 wt% C/Cu, 4.5 wt% SMA 1000 H relative to C/Cu) by adding other additives. All of those inks were applied on a glass substrate using a spreading knife with a gap of 12 microns.

Example 12

Addition of 4.5 wt% BYK 348 (relative to C/Cu) 12.9 wt% PVP (Polyvinylpyrrolidone K30, Fluka 32250, Mr = 40000) (relative to C/Cu)

Example 13

Addition of 3.2 wt% BYK 348 (relative to C/Cu) additionally 15.3 wt% SMA 1000 H (relative to C/Cu)

Example 14

Addition of 9.6 wt% BYK 348 (relative to C/Cu) additionally 7.8 wt% SMA 1000 H (relative to /Cu)

Example 15

Addition of 6.6 wt% BYK 348 (relative to C/Cu) additionally 9.5 wt% SMA 1000 H (relative to C/Cu)

Example 16

Addition of 10.1 wt% BYK 348 (relative to C/Cu) additionally 10.8 wt% SMA 1000 H (relative to C/Cu)

Example 17

Addition of 34.8 wt% BYK 348 (relative to C/Cu) additionally 10.8 wt% SMA 1000 H (relative to C/Cu)

Example 18

Addition of 3.3 wt% BYK 348 (relative to C/Cu) 7.3 wt% Disperbyk 190 (relative to C/Cu)

Example 19 Addition of 10 wt% Diethyleneglycol- monobutylether (Fluka 32250) 2 wt% BYK 340 (fluoro-tenside BYK Chemie, relative to C/Cu) 12 wt% hobby color acryl (water based acrylic paint, hobby color H30, GSI Creos Corporation, Tokyo, Japan, relative co C/Cu)

Example 20

Addition of 1.3 wt% Diethyleneglycol- monobutylether (Fluka 32250) 4.3 wt% WET510 (Tego Chemie, relative to C/Cu)

Example 21

A dispersion was prepared consisting of 7.2 % by weight of carbon coated copper nanoparticles (particles synthesized as described in WO2007/028267) in deionized water (Milipore, electrical resistivity > 18 MΩcm) and a high-molecular-weight, block-copolymeric additive with acidic, pigment-affinic groups (7.7 wt % relative to C/Cu, Disperbyk 190, BYK Chemie) and an amphiphilic silicon tenside (10.5 wt % relative to C/Cu, BYK 348, a polyether- modified poly (dimethyl siloxane) ) . The dispersion was prepared by manually mixing the 2 additives with the deionized water, then adding the carbon coated copper nanoparticles. The nanoparticles were dispersed by ultra- sonication (Dr. Hielscher, UP400S, 80% intensity, 0.2 cycle) for 10 minutes. The dispersion was further centrifuged at 2000 rpm (MSE Mistral 300E) for 2 minutes in order to remove undispersed large agglomerates and other contaminants like dust particles.

Then 3.8 wt% Diethyleneglycol-monobutylether (Fluka 32250) and 8.2 wt% (relative to C/Cu) Hobby-Color- Acrylate (water based acrylic paint, hobby color H30, GSI Creos Corporation, Tokyo, Japan) was ad-mixed.

The obtained ink was applied onto a glass substrate using a spreading knife with a gap of 12 microns. The results of all examples may be summarized as follows, wherein + denotes "high", o denotes "medium" and - denotes "low":

References

(1) Limbach, L. K.; Li, Y. C; Grass, R. N.; Brunner, T. J.; Hinterrαann, M. A.; Muller, M.; Gunther, D.; Stark, W. J. Environ. Sci. Technol. 2005, 39, 9370.

(2) Athanassiou, E. K.; Grass, R. N.; Stark, W. J. Nanotechnology 2006, 17, 1668.

(3) Erwin, R. Anorganische chemie; Walter de Gruyter: New York, 1999.

(4) Chung, J. W.; Ko, S. W.; Bieri, N. R.; Grigoropoulos, C. P.; Poulikakos, D. Appl. Phys . Lett. 2004, 84, 801.

(5) Ivanisevic, A.; Mirkin, C. A. J. Am. Chem. Soc. 2001, 123, 7887.

(6) Maynor, B. W.; Li, Y.; Liu, J. Langmuir 2001, 17, 2575.

(7) Huang, D.; Liao, F.; Molesa, S.; Redinger, D.; Subramanian, V. J. Electrochem. Soc. 2003, 150, G412.

(8) Kamyshny, A.; Ben-Moshe, M.; Aviezer, S.; Magdassi, S. Macromol. Rapid Commun. 2005, 26, 281.

(9) Fuller, S. B.; Wilhelm, E. J.; Jacobson, J. A. J. Microelectromech. Syst. 2002, 11, 54.

(10) Kim, D.; Jeong, S.; Moon, J.; Kang, K. MoI. Cryst. Liquid Cryst. 2006, 459, 45.

(11) Kim, D.; Moon, J. 2005, 8, J30.

(12) Lee, H. H.; Chou, K. S.; Huang, K. C. Nanotechnology 2005, 16, 2436.

(13) Lee, K. J.; Jun, B. H.; Kim, T. H.; Joung, J. Nanotechnology 2006, 17, 2424.

(14) Magdassi, S.; Bassa, A.; Vinetsky, Y.; Kamyshny, A. Chem. Mat. 2003, 15, 2208.

(15) Park, J. W.; Baek, S. G. 2006, 55, 1139.

(16) Schulz, D. L.; Curtis, C. J.; Ginley, D. S. Electrochem. Solid State Lett. 2001, 4, C58. (17) Cuk, T.; Troian, S. M.; Hong, C. M.; Wagner, S. Appl. Phys. Lett. 2000, 77, 2063.

(18) Rickerby, J.; Simon, A.; Jeynes, C; Morgan, T. J.; Steinke, J. H. G. Chem. Mat. 2006, 18, 2489.

(19) Luechinger, N. A.; Loher, S.; Athanassiou, E. K.; Grass, R. N.; Stark, W. J. Langmuir 2007, 23, 3473.

(20) Lu, A. H.; Li, W. C; Matoussevitch, N.; Spliethoff, B.; Bonnemann, H.; Schuth, F. Chem. Commun. 2005, 98.

(21) Zalich, M. A.; Baranauskas, V. V.; Riffle, J. S.; Saunders, M.; Pierre, T. G. S. Chem. Mat. 2006, 18, 2648.

Claims

1. Composition comprising a) carbon-coated non-noble metal nanoparticles; b) liquid carrier c) dispersing additive.

2. Composition according to claim 1 wherein the metal is selected from the group consisting of Cu, Co, Mo, Ni, in particular Cu.

3. Composition according to claim 1 or 2 wherein the carrier contains at least 50 wt-% water, in particular at least 90 wt-% water.

4. Composition according to claim 3 wherein the dispersing additive is a tenside with at least one hydrophilic and one lipophilic group.

5. Composition according to claim 4 wherein the lipophilic group is selected from the group consisting of aromatic groups; saturated, unsaturated or partly unsaturated aliphatic groups; siloxane based groups, fluoro-carbon based aliphatic groups.

6. Composition according to claim 4 wherein the hydrophilic group contains one or more functional moieties selected from the group consisting of sulphonates, phosphonates, substituted and unsubstituted ammonia, hydroxy, hydroxy- (poly) ether, carboxylic acids and its salts.

7. Composition according to claim 1 or 2 wherein the carrier contains at least 50 wt-% organic solvent, preferably at least 90 wt-% organic solvent.

8. Composition according to claim 7 wherein the organic solvent is selected from the group consisting of alcohols, ethers, esters, ketones or combinations thereof.

9. Composition according to claim 7 or 8 wherein the dispersing additive is a dispersing polymer.

10. Composition according to claim 9 wherein the dispersing polymer is a poly-vinyl-pyrrolidone polymer, an acrylic polymer, a poly-vinyl-pyrrolidone copolymer, an acrylic copolymer .

11. Method for manufacturing a composition according to any of claims 1 to 10, comprising the step of

a) combining at least one liquid carrier and at least one dispersing additive to obtain a homogeneous phase; b) dispersing the nanoparticles as defined in claim 1 to obtain a stable dispersion; c) optionally removing agglomerates and/or other impurities from the dispersion obtained.

12. Method according to claim 11 wherein step b) comprises ultrasonication.

13. Method according to claim 11 or 12 wherein step c) comprises centrifugation.

14. Device substrate is partly or fully coated with a coating and wherein said coating contains a composition as defined in any of claims 1-10.

15. Device according to claim 14, having a substrate which comprises one or more of the following materials: a) glass b) plastic c) metal d) paper e) textiles f) ceramic g⁾ polymer h) circuit board i) rubber wood.

16. A method of manufacturing a device according to claim 14 or 15, where the coating method comprises printing techniques, spray techniques, dip coating techniques or brush applications .

17. The manufacture of a device according to any of claims 14 to 16 where an additional heat treatment is applied after the application method.

18. Device according to claim 14 or 15 comprising a) a substrate; b) a first layer comprising either an amorphous polymer layer or a mixture of a polymer and a surface-active additive; c) a second layer comprising a composition as described in any of claims 1 to 10; whereby said second layer is directly adjacent to said first layer or a) a substrate which comprises or consists of an amorphous polymer or a mixture of a polymer and a surface-active additive; b) a layer comprising a composition as described in any of claims 1 - 10; whereby said layer is directly adjacent to the surface.

19. Device according to claim 18 wherein the amorphous polymer is an acrylate based polymer.

20. Device according to claim 18 wherein the surface active additive is selected from the group consisting of polyether modified silicone tensides, a fluoro-carbon tensides and/or modified acrylic tensides.

21. Device according to any of claims 14 - 15 or 18 - 20 wherein the substrate is a chassis or a body of a vehicle or consumer electronics device or a part thereof, in particular the chassis or rims of a car.

22. Method of manufacturing a device according to any of claims 18 to 21 comprising the step of a) optionally applying a first layer, said layer comprising an amorphous polymer or a mixture of a polymer and a surface-active additive according to claim 19 on a substrate and b) applying a second layer, said layer comprising a composition as described in any of claims 1 - 10, on top of said first layer

23. Method of manufacturing a device according to claim 22 wherein said application method is selected from the group consisting of hydraulic, pneumatic, and/or electrostatic spray or dip coating methods, or printing methods .

24. Method of manufacturing a device according to any of claims 22 to 23 wherein an additional heat treatment is applied after step b) .

25. Method of manufacturing a device according to claim 24 wherein the heat treatment comprises an air or nitrogen gas stream having a temperature between r.t. and 200⁰C, preferably between 50⁰C and 150⁰C for a time period of between one second and 1 hour, preferably between 10 sec. and 10 min.

26. Use of a composition according to any of claims 1 - 10 for manufacturing of a) a decorative coating / surface, in particular in automotive industry; b) a conductive pattern, such as an electrical circuit; c) a transistor; d) a humidity sensitive device; e) a solvent sensitive device; f) an electrical circuit; g) printable electronics for the manufacture of printable displays, photovoltaics, radio frequency identification tags (RFID tags) , computer memory devices, electronic circuits, processors, photodiodes, high electron mobility transistors

(HEMTs) , semiconductor field-effect transistors, printable electronic spools, printable hard-drives.

27. Use of a composition according to any of claims 1 - 10 a) as replacement for metal coatings on non-metal surfaces; b) as decorative coating on metal substrates / surfaces; c) as fiber coating for clothing manufacturing; d) as paint; e) as magnetic black ink; f) as infrared (IR) light reflecting devices; g) as ultra-violet (UV) protective devices ; h) as nail polish; i) as marine antifouling coating.