ART PROTECTION WITH THE USE OF GRAPHENE MATERIALS

Abstract

The inventive method for applying a protective graphene coating onto a surface, especially onto a two- or three dimensional artwork or colored surface, comprises the following steps: a) depositing, preferably by chemical vapor deposition (CVD), graphene onto a at least one side of a supporting substrate to produce a graphene/substrate composite including a continuous graphene membrane formed on at least one side of said substrate; b) removing the substrate, or lifting off the graphene from the substrate and c) depositing the graphene membrane onto the surface. A protective graphene coating prepared and deposited by this method provides protection for a surface, especially a two- or three-dimensional artwork or a colored surface, against color degradation, especially fading, yellowing and discoloration due to exposure to UV radiation, dirt, dust, moisture, chemical and/or oxidizing agents.

Claims

1.-16. (canceled)

17. A method for protecting a two- or three dimensional artwork or a colored surface against color degradation, the method comprising the steps of: a) depositing graphene onto at least one side of a supporting substrate to produce a graphene/substrate composite comprising a continuous graphene membrane formed on at least one side of the substrate; b) removing the substrate, or lifting off the graphene membrane from the substrate; and c) depositing the graphene membrane onto the two- or three dimensional artwork or colored surface.

18. A method according to claim 17, wherein the substrate is selected from the group consisting of a metal, polymer and non-metal material.

19. A method according to claim 17, further comprising the step of: after step a), applying a supporting layer onto the graphene membrane bearing side of the graphene/substrate composite to produce a supporting layer/graphene/substrate composite.

20. A method according to claim 19, wherein the supporting layer is selected from the group consisting of a polymer-based backing substrate and adhesive film.

21. A method according to claim 20, wherein the polymer-based backing substrate or the adhesive film is at least one member selected from the group consisting of a flexible material and transparent.

22. A method according to claim 17, wherein the color degradation is fading, yellowing or discoloration due to exposure to UV radiation.

23. A method according to claim 17, wherein additionally an oxygen plasma treatment is performed after step a).

24. A method according to claim 17, wherein, in step c, depositing of the graphene membrane onto the surface is performed via a roll-to-roll coating or unrolling process.

25. A method according to claim 24, wherein the roll-to-roll coating or unrolling process are performed under at least one of the following conditions: a temperature of 45 to 70° C., a pressure of 0.1 to 10 MPa, and a rolling speed of 0.1 to 5 mm/sec.

26. A method according to claim 17, wherein the protective graphene coating is a continuous graphene membrane having dimensions from a few centimeters up to several meters is deposited to fully or at least partially cover the surface or artwork.

27. A method according to claim 17, wherein in step a) a continuous graphene monolayer or multilayer membrane is formed, the membrane preferably having a thickness of from 0.33 nm (monolayer) to n×0.33 nm (multilayer).

28. A method according to claim 17, wherein the surface to be coated exhibits a surface roughness from 1 nm to 10 μm and/or a surface energy of 17 to 64 mN/m.

29. A method according to claim 17, wherein the surface to be coated comprises a member selected from the group consisting of canvas, paper, cardboard, photographic paper, wood, a polymer, a painting, papyrus, a cover of old music vinyl records, a cover page of a magazine, an interior page of a magazine, a book cover, a page of a book, a mural, artistic masonry and an art installation.

30. A method according to claim 17, further comprising protection for the artwork or colored surface against dirt, dust, moisture, chemical and/or oxidizing agents.

31. A method according to claim 18, wherein the supporting substrate is selected from the group consisting of a flexible sheet and a foil material.

32. A method according to claim 19, wherein the supporting layer is a pressure-sensitive adhesive film.

33. A method according to claim 17, wherein applying the supporting layer is performed via a roll-to-roll coating process.

34. A method according to claim 17, wherein applying the support layer is performed via direct compression transfer.

35. A method according to claim 20, wherein the polymer-based backing substrate or the adhesive film is at least one member selected from the group consisting of a PET-, PMMA-, and PET/silicone film or membranes.

36. A method according to claim 17, wherein in step a) a graphene monolayer or multilayer membrane is formed, the graphene monolayer or membrane having a thickness of from 0.33 nm to n×0.33 wherein n is a number of layers in the multilayer membrane.

Description

DESCRIPTION OF THE FIGURES

[0039] The included figures show the following:

[0040] FIG. 1A: Transmittance spectra of a graphene veil with increasing number of layers, synthesized with CVD method. Inset: The corresponding absorption spectra in absorbance units (a.u.).

[0041] FIG. 1B: Schematic illustration of the roll-to-roll method used to transfer graphene onto mockups and real artworks.

[0042] FIG. 2: A further schematic illustration of the inventive method.

[0043] FIG. 3: The fluctuation of several parameters related to the growth of CVD graphene onto copper foil.

[0044] FIG. 4: Final configuration for the laminator. The modified laminator was the basic instrument for dry roll-to-roll graphene transfer onto artworks.

[0045] FIG. 5A: A scheme showing the deposition and subsequent removal of graphene from “Biplane, Handley Page H. P. 42” using a soft rubber eraser.

[0046] FIG. 5B: Colorimetric data acquired during the process of graphene deposition and removal, clearly showing that the veil is almost not visible or just noticeable on different colors, and it can be removed without damaging the optical integrity of the artwork.

[0047] FIG. 6: A Collage showing paper mockups featuring a pink dye, which were protected with graphene and then aged under white light. The color that was not protected by graphene displayed a ΔE* of about 10.2 (Sketch 1) after 70 hours. When graphene is present, the ΔE* at the end of the aging is around 4.6 (Sketch 2). Just after the removal of graphene using a rubber eraser (FIG. 3), a similar ΔE* of 5.4 was recorded, which clearly demonstrates that the presence of graphene did not have any deleterious effect on the color underneath (Sketch 3).

[0048] FIG. 7: Contact angle of water on cardboard with monolayer CVD graphene. The angle reaches 128° when the monolayer is deposited onto the paper, from full wetting and absorption (0°) when graphene is absent.

[0049] FIG. 8A: The painting entitled “Triton and Nereid”* before and after 130 hours of aging under visible light. A central area was covered during the aging to be used as a reference. The difference induced in the light blue areas (upper left, protected, and in the middle and right, not protected) is shown after 130 hours of artificial aging.

[0050] FIG. 8B: Colorimetric data acquired on pink (middle-up on the left, protected, and in the middle-down on the right, not protected) and light blue (the one described in FIG. 8A) dyes upon aging, on not protected (left) and protected with graphene (right) areas.

[0051] FIG. 9A: The painting entitled “Resistance”* before and after 4 weeks of aging under neon light. A central area was covered during the aging to be used as a reference. The difference induced in the pink areas (upper left, protected, and lower right, not protected) is shown after 4 weeks of artificial aging.

[0052] FIG. 9B: Colorimetric data acquired on blue (up at the middle on the left, protected, and in the up at the middle on the right, not protected) and pink (the one described in FIG. 9A) dyes upon aging, on not protected (left) and protected with graphene (right) areas.

[0053] FIG. 10A: Paper mockups dyed with blue ink (Ultramarine) of Pelikan brand featuring graphene. Up: From left to right, a reference sample (without graphene) and samples with 0.1% w/w and 1% w/w graphene powder dispersion. Down: The same dyed papers after an aging of 200 hours with white/visible light. Please note that the lower part of the samples was covered by a thick cardboard paper in order to have an unaged area, as reference. It is obvious that all samples are faded, but as graphene concentration increases, the fading is less.

[0054] FIG. 10B: Paper mockups dyed with pink ink (Carmine) of Pelikan brand featuring graphene. Up: From left to right, a reference sample (without graphene) and samples with 0.1% w/w and 1% w/w graphene powder dispersion. Down: The same dyed papers after an aging of 390 hours with white/visible light. Please note that the lower part of the samples was covered by a thick cardboard paper in order to have an unaged area, as reference. It is obvious that all samples are faded, but as graphene concentration increases, the fading is less.

[0055] FIG. 11A: The absorbance of blue tempera solutions including increasing amounts of graphene

[0056] FIG. 11B: The absorbance of red tempera solutions including increasing amounts of boron nitride powder.

[0057] FIG. 11C: Contact angle measurements for a blue oil paint containing increasing amounts of graphene.

[0058] FIG. 11D: Contact angle measurements for a red oil paint containing increasing amounts of graphene.

EXAMPLES

Example 1

[0059] Production of Graphene Veils

[0060] The graphene monolayers are synthesized on copper foils in an AIXTRON® BM Pro CVD chamber. A high quality copper substrate supplied by Viohalco® was used as the catalyst substrate. For the graphene production, the foil is cut into 7×7 cm2, cleaned by isopropanol to remove any organic contamination and introduced into CVD chamber. After the closure of the chamber, it is immediately pumped down to 0.1 mbar and then a mixture of argon/hydrogen (Ar/H2) gases is introduced (250 sccm/50 sccm) with a pressure below 25 mbar. The foil is heated in 1000° C. and is kept there for 5 min for annealing. Afterwards the sample is cooled down to 925° C., while methane (CH4) is introduced into chamber (10 sccm) as carbon feedstock to initiate the graphene growth on copper foil surface. After 5 min, the H.sub.2 flow is terminated, the chamber is cooled down to 650° C. and the CH.sub.4 flow is also terminated. Then the chamber is cooled down to room temperature under an Ar atmosphere. FIG. 3 illustrates the fluctuation of applied pressure, temperature and gases flow.

Example 2

[0061] Graphene Transfer Method

[0062] The roll-to-roll method (Kim, S. J., et al., Ultraclean Patterned Transfer of Single-Layer Graphene by Recyclable Pressure Sensitive Adhesive Films. Nano Letters, 2015. 15(5): p. 3236-3240) without the use of solvents or chemicals is ideal for graphene deposition without damaging the artworks. For that reason, a tailor-made roll-to-roll machine based on a commercial laminator was designed and built. The whole procedure is shown in FIG. 1B. Firstly, CVD graphene is cleaned from dust, dirt or/and water molecules by purging nitrogen gas on its surface. Then, the specimen is attached to one side of a commercial flexible PET/Silicone membrane by employing the roll-to-roll machine (FIG. 4), at a rolling speed of 0.195-0.325 mm/sec and pressure of 0.1-0.5 MPa. The PET/Silicone film was chosen as a backing substrate because it adheres well to the copper sheet with the graphene on top of it and is transparent and flexible. Also, it is resistant to aggravating agents of subsequent processing steps (oxygen plasma, etching, and pressure—transfer temperature). Then, the graphene deposited on the other side of the membrane is removed by oxygen plasma. Subsequently a water solution of 0.1 M ammonium persulfate is used to etch the copper, and afterwards, deionized water is used to clean any remaining dirt or residue of the ammonium persulfate. The PET/Silicone/graphene membrane is left for at least 8 hours inside a vacuum chamber in order to be de-hydrated. Afterwards, the membrane is ready to be transferred onto paper substrate. For the graphene transfer, the reverse procedure of rolling, i.e. unrolling (FIG. 1B), is performed, using the same parameters indicated above, at a temperature of 50-55° C. For the deposition of bi-, tri- or multi-layered membranes, we iterated the same procedure so to have non-Bernal stacked multilayers.

[0063] The dry transfer method is based on the use of pressure-sensitive adhesive films (PSAF), like the PET/Silicone membrane as supporting layer. It takes advantage of the difference in wettability and adhesion energy of graphene with respect to PSAF and the target substrate. Then, the PSAF layer is simply peeled off from the target substrate, thus leaving the graphene membrane on the substrate. The basic parameters which define the success of the transfer process are estimated to be the transfer rate, temperature and pressure. Empirically, we have observed that the lower the transfer rate, the more effective the graphene transfer is. Finally, it was observed that mild heating to 50-55° C. has positive effect on the transfer quality. Such an effect is attributed to the change of surface properties of PET/Silicone since its surface energy decreases by the thermal treatment. For the graphene membranes, the transfer process must be performed at a slow rate to ensure the homogeneous heating to the desirable temperature by the laminator's rollers of graphene and the substrates. Regarding the transfer pressure, it is noticed that application of high pressure between the rollers results in a homogeneously transferred graphene film. Hence, the design of the laminator has been performed based on the above parameters and findings. A commercial cold/hot laminator FJK 320 was modified in order to be used as the roll-to-roll transfer system. The system could operate up to 180° C. and the initial motor's speed was 3.5 rpm which corresponds to a linear velocity of 9.2 mms.sup.−1, since the rollers' diameter is 2.5 cm. The measured speed was much higher than that required for the given application, so the initial motor was replaced by the NEMA-17 stepper motor with an integrated planetary gearbox with a 99.51:1 drive ratio. The final configuration of the as-modified laminator is presented at FIG. 4.

Example 3

[0064] Removal of Graphene Veils

[0065] In art conservation, the reversibility of the treatment is mandatory for any intervention, especially in the case of paintings and graphical artworks. Graphene adheres to surfaces via weak bonds, and this should favor its removability*. Therefore, to verify our hypothesis, we deposited on “Biplane, Handley Page H. P. 42” a single layer of CVD graphene, and then we removed the protective coating, by means of a soft rubber eraser (see FIG. 5A). To assess the effect of removal, colorimetric coordinates (ΔE*) were recorded on three colored spots before and after graphene deposition, and after the removal of the veil (see FIG. 5B). The values measured were close to zero bearing also in mind that the statistical error of the colorimeter is ±0.5, which proves that the process is reversible, and the graphene veil can be easily removed without damaging the optical integrity of the artwork.

Example 4

[0066] Preparation and Characterization of Mockups and Real Artworks

[0067] General Information about Colorimetric Measurements:

[0068] Colorimetric coordinates are extracted from reflectance spectra using standard illuminant D65 and a standard observer at 10° (CIE 1964, G. Wyszecki, W. S. Stiles, Color Science: Concepts and Methods, Quantitative Data and Formulae, John Wiley & Sons, New York, N.Y., ed. 2nd, 2000; http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0471399183.html). The color difference between samples can be expressed in terms of the ΔE* parameter, calculated from the colorimetric coordinates and L*, a*, and b* as follows*:

ΔE*=√{square root over ((L*.sub.2−L*.sub.1).sup.2+(a*.sub.2−a*.sub.1).sup.2+(b*.sub.2−b*.sub.1).sup.2)}

[0069] To compare the colorimetric coordinates after the aging, of not protected and protected with graphene samples, we calculate a Protection Factor (PF), according to:

[00001]$\mathrm{PF}\left(\%\right)=\left(\frac{{\Delta E}_{\mathrm{color}\mathrm{wtihout}\mathrm{graphene}}^{*}-{\Delta E}_{\mathrm{color}\mathrm{with}\mathrm{graphene}}^{*}}{{\Delta E}_{\mathrm{color}\mathrm{without}\mathrm{graphene}}^{*}}\right)*100$

[0070] Detail about the preparation, characterization and aging of mockups and real artworks are reported below.

[0071] Paper Mockups Featuring a Blue Dye: Preparation, Characterization and Aging:

[0072] Filter paper disks (Whatman n.1; 99% made with cotton fibers; paper density=88.0 g/m2; diameter=55 mm) were used to prepare paper mockups. On each disk, 2 mL of a Methyl Blue (Sigma-Aldrich; product number: M6900) aqueous solution at 2.5% (w/w) was applied using a micropipette. Samples were left to dry under the hood for 48 hours.

[0073] On each sample, graphene veils of 1, 2 and 3 layers (3.5×3.5 cm2) were deposited, using the roll-to-roll method described elsewhere. Graphene appears to be following the pattern of the surface with no apparent gaps or cracks. A not protected sample was used as a reference. Before and after deposition, reflectance spectra were acquired using a Cary 100 UV-VIS spectrophotometer, working in a λ range of 400-700 nm (with 1 nm of resolution), equipped with an integrating sphere having a circular sampling spot (diameter=1.5 cm). The error related to ΔE* values obtained using this instrument is ±0.5.

[0074] All the samples were then artificially aged in an in-house built aging chamber, equipped with three Neon Light Color 765 BASIC Daylight Beghelli neon lamps. The average illuminance was 11000 Lux, RH was 40% and temperature was 36° C. The aging lasted 4 weeks. A portion of each sample was covered during the aging, to be used as a reference. Every week, reflectance spectra were acquired as indicated above. Colorimetric coordinates were obtained as described above. After aging, the transferred graphene does not show any macroscopic defects such as cracks or holes. Data obtained on these set of samples are reported in Table 1.

TABLE-US-00001 TABLE 1 ΔE* after graphene deposition and PF for the paper mockups featuring the blue dye. Sample ΔE* after deposition Protection Factor (%) MB + 1 graphene layer 2.2 6.9 MB + 2 graphene layers 3.0 8.0 MB + 3 graphene layers 3.4 9.8

[0075] Paper Mockups Featuring a Pink Dye: Preparation, Characterization and Aging:

[0076] Cardboard (Bristol type) was used to prepare paper mockups. A pink ink Carmine Pelikan drawing ink) was applied on the samples using a paintbrush. Samples were left to dry under the hood for 24 hours. On each sample, a monolayer graphene veil (7×7 cm2) was deposited, using the roll-to-roll method described elsewhere. Some samples were not protected with graphene and were used as references.

[0077] The samples were then artificially aged in an in-house built aging chamber, equipped with seven lights panel emitting white light. The aging lasted 70 hours. The bottom part of each sample was covered during the aging. At the end of the aging, the graphene was removed from the samples as described in Example 3.

[0078] Before and after deposition, upon aging, and after the removal of graphene, reflectance spectra were acquired using FRU WR-10 portable colorimeter. Colorimetric coordinates were obtained from reflectance spectra as described previously. The error related to ΔE* values obtained using this instrument is ±0.5. In FIG. 6, and Table 2, pictures and data about the experiments conducted on these mockups are reported.

TABLE-US-00002 TABLE 2 ΔE* of paper mockups featuring the pink ink, after aging, before and after the removal of graphene. Please note that the difference in ΔE* between samples before and after removal of the graphene, especially at lower aging times, is close to the experimental error. Nevertheless, the ΔE* are significantly lower than those shown by the unprotected reference system, demonstrating that the color underneath the graphene veil is indeed protected. ΔE* ΔE* ΔE* Sample (20 h) (50 h) (70 h) Reference 5.7 8.4 10.2 Sample protected with 2.2 4.4 4.6 graphene Sample protected with 2.0 3.6 5.4 graphene after its removal

[0079] Contact Angle Measurement of Water on Cardboard with a Deposited Monolayer Graphene:

[0080] Contact angle measurements were performed by a KRÜSS DSA 100 contact angle meter, and, the used liquid was distilled water. Sessile drop method was used while each point was being measured three times to calculate average value. The used cardboard was the same described in the previous paragraph. Graphene was transferred onto the cardboard with the procedure described above in Example 2.

Example 5

[0081] a) “Triton and Nereid”: Characterization and Aging

[0082] “Triton and Nereid” has been donated by a Greek artist (Mrs. Matina Stavropoulou (http://www.gallery7.gr/website/painting/matina-stavropoulou/)). It has been realized with Indian inks on glossy paper placed over a canvas support. It measures approximately 20×20 cm.sup.2. To perform our experiments, half of the artwork was protected with a monolayer graphene using the roll-to-roll method described elsewhere. Graphene appears to be following the pattern of the painting surface with no apparent gaps or cracks.

[0083] The artwork was then artificially aged in an in-house built aging chamber, equipped with seven lights panel emitting white light. The aging lasted 1050 hours. A portion of the artwork was covered during the aging, to be used as a reference. After aging, the transferred graphene does not show any macroscopic defects such as cracks or wrinkles.

[0084] Reflectance spectra were acquired using FRU WR-10 portable colorimeter. Colorimetric coordinates were obtained from reflectance spectra as described in Example 4. The error related to ΔE* values obtained using this instrument is ±0.5. In Table 3, data about the experiments conducted on this artwork are reported.

[0085] The color changes of light blue and pink dyes in the protected and not protected areas were monitored over time and are reported in FIG. 8B. An overall protecting factor (PF) for the light blue dye of about 38.5% was obtained after 130 hours of exposure, as shown in FIG. 8A. The different amount of aging of the two spots can be ascribed to the fact that the light blue one is probably composed of a single dye, while the so-called pink, features different dyes, with different resistance to fading. Nevertheless, PF is about 35% for light blue color after 1050 hours of aging.

TABLE-US-00003 TABLE 3 ΔE* and PF for the selected colors of “Triton and Nereid”. Color ΔE* after aging Protection Factor (%) Violet 16.9 19.0 Graphene/Violet 12.1 Pink 14.0 27.5 Graphene/Pink 10.1 Light Blue 7.8 38.5 Graphene/Light Blue 4.8

[0086] b) “Resistance”: Characterization and Aging:

[0087] “Resistance” has been donated by a Greek artist (Mrs. Matina Stavropoulou (http://www.gallery7.gr/website/painting/matina-stavropoulou/)). It has been realized with Indian inks on glossy paper placed over a canvas support. It measures approximately 20×20 cm2. To perform our experiments, half of the artwork was protected with a monolayer graphene using the roll-to-roll method already described. Graphene appears to be following the pattern of the painting surface with no apparent gaps or cracks.

[0088] The artwork was then artificially aged in an in-house built aging chamber, equipped with three Neon Light Color 765 BASIC Daylight Beghelli neon lamps. The average illuminance was 11000 Lux, RH was 40% and average temperature was 36° C. The aging lasted 16 weeks. A portion of the artwork was covered during the aging, to be used as a reference. Every two weeks, colorimetric coordinates on different spots were recorded using a X-RITE SP60 VIS portable spectrophotometer, with an integrating sphere having a circular sampling spot (diameter=1.5 cm). The error related to ΔE* values obtained using this instrument is ±0.75. After aging, the transferred graphene does not show any macroscopic defects such as cracks or holes. In FIG. 9, pictures and data about the experiments conducted on this artwork are shown.

[0089] The color changes of blue and pink dyes in the protected and not protected areas were monitored over time and are reported in FIG. 9B. An overall protecting factor (PF) for the pink dye of about 49% was obtained after four weeks of exposure. PF is about 35% for both colors after four months of aging. This clearly demonstrates the effectiveness of a monolayer graphene in the protection of highly light-sensitive dyes from fading.

TABLE-US-00004 TABLE 4 ΔE* and PF for the selected colors of “Resistance”. Color ΔE* after aging Protection Factor (%) Pink 27.8 46.7 Graphene/Pink 14.8 Dark Blue 17.2 43.6 Graphene/Dark Blue 9.7

Example 6

[0090] Creation of Graphene-Based Inks and Evaluation of their Aging or Fading Under UV Exposure

[0091] For the creation of graphene-based inks, commercial inks of a known brand (Pelikan) were exploited, which are used by many professionals and amateur artists. Particularly, Ultramarine (blue) and Carmine (pink) inks were examined. Firstly the ink, then the graphene nanoplatelets (GNPs, powder) were weighed and afterwards the GNPs were added into the ink. Subsequently, an ultrasonic bath sonication for 3 minutes was performed in order to obtain the graphene-enhanced ink, with a known % w/w concentration. GNPs were Elicarb® graphene nano-powder produced by liquid exfoliation of graphite and supplied by Thomas Swan & Co. Ltd. This material consists of few layer graphene platelets, with typical lateral size of 5 μm [http://thomas-swan.co.uk/wp-content/uploads/2017/09/Elicarb-Graphene-Products-Advanced-Materials-LR.pdf]. From this series, specifically the powder coded as Electrical Grade of smaller flake size (˜3 μm) was used which results from an additional process step for removing any residual surfactant that was employed to assist graphene dispersion.

[0092] For the creation of graphene-oxide based inks, graphene oxide synthesized in the lab was used. The GO was synthesized from natural graphite flakes (NGS Naturgraphit GmbH, Germany) by a two-step oxidation process. At the beginning, 10 g natural graphite flakes were added in 75 ml concentrated sulfuric acid (H.sub.2SO.sub.4 96%) in a flask. The flask was placed in a bath and heated at 80° C. After that, 5 g potassium persulfate (K.sub.2S.sub.2O.sub.5) and 5 g phosphorus pentoxide (P.sub.2O.sub.5) were added in the solution. The mixture was stirred for 1 h at this temperature and then allowed to cool at room temperature in a period of 5 h. The reaction was terminated by carefully adding deionized water (DW), followed by several steps of vacuum filtration with DW, drying. The oxidized graphite was then subjected to oxidation by modified Hummer's method, where the powder was stirred continuously into a flask with 220 ml H.sub.2SO.sub.4 96%, in a water bath. Gradually, 26.7 g potassium permanganate (KMnO.sub.4) was added in the mixture. Thereafter, the mixture was heated to 40° C. for 2 h, where 1.8 liters DW were added carefully, followed by 22 ml hydrogen peroxide (H.sub.2O.sub.2 30%). Then the mixture was filtered and washed with 1:10 HCl solution in order to remove most of the metals ions. The solid product of this process was redispersed in DW to reduce its concentration until its pH becomes the same with DW's pH. Finally, single and few layers of GO were collected by a combination of ultra-sonication and centrifugation steps.

[0093] The graphene-oxide solution with a known concentration in water was weighed, and then incorporated in the same before-mentioned inks, blue and the pink one. Subsequently, an ultrasonic bath sonication for 3 minutes was performed in order to obtain the graphene oxide-enhanced ink, with a known % w/w concentration.

[0094] FIG. 10 shows some samples obtained using such ink before and after exposure to visible light.

[0095] Tables 5 and 6 shows the Delta E values and the protection factor after treatment of samples comprising inks obtained as described above.

TABLE-US-00005 TABLE 5 Aging with strong UV light, from a UV-C lamp (254 nm) with a power of 4 mWatts Delta E after Protection Sample aging/fading Factor Reference sample with blue color 56.10 — Blue colored with 0.1% w.w. Graphene 44.82 20.10 powder dispersion Blue colored with 1% w.w. Graphene 33.66 40.00 powder dispersion Blue colored with 0.1% w.w. Graphene 35.16 37.30 oxide solution Blue colored with 1% w.w. Graphene 27.20 51.50 oxide solution Reference sample with pink color 36.10 — Pink colored with 0.1% w.w. Graphene 24.38 32.46 powder dispersion Pink colored with 1% w.w. Graphene 20.74 42.54 powder dispersion Pink colored with 0.1% w.w. Graphene 25.62 29.04 oxide solution Pink colored with 1% w.w. Graphene 21.73 39.80 oxide solution

TABLE-US-00006 TABLE 6 Aging with visible light, from an in-house built aging chamber, equipped with seven lights panel, with a power of 33 mWatt. Delta E after Protection Sample aging/fading Factor Reference sample with blue color 51.16 — Blue colored with 0.1% w.w. Graphene 45.57 10.90 powder dispersion Blue colored with 1% w.w. Graphene 34.15 33.24 powder dispersion Blue colored with 0.1% w.w. Graphene 41.30 19.31 oxide solution Blue colored with 1% w.w. Graphene 29.62 42.10 oxide solution Reference sample with pink color 36.62 — Pink colored with 0.1% w.w. Graphene 33.25 9.20 powder dispersion Pink colored with 1% w.w. Graphene 25.05 31.60 powder dispersion Pink colored with 0.1% w.w. Graphene 27.12 25.94 oxide solution Pink colored with 1% w.w. Graphene 23.66 35.40 oxide solution

Example 7

[0096] Creation of Graphene-Based Acrylic Paints and Preparation of Samples for UV Exposure

[0097] For the creation of graphene-based acrylic paints, some commercial acrylic paints (temperas) of a well-known brand, Talens Art Creation, were purchased which are used by many professionals and amateur artists. Particularly, art creation No 369, Primary Magenta (red) and art creation No 572, Primary Cyan (blue) were examined. These commercial acrylics were water soluble. For this application, again, GNPs—Electrical grade were used, but this time they were dispersed in distilled water. An amount of 35 mg of GNPs was dissolved in 15 g of distilled water. Then, from this solution, 0.16, 0.33, 0.45 and 0.59 g were added in vials that each one contained 10 ml of distilled water, in order to obtain 5 solutions with increased concentration in graphene. An ultrasonic bath sonication for 30 minutes followed. For the creation of aqua sols with acrylic paint and graphene, 0.5 g of the examined color were dissolved in 400 ml of distilled water. Taking a standard amount of this solution each time, and using the 5 pre-mentioned graphene dispersions, 5 solutions with diluted color and increasing graphene concentration were examined. An ultrasonic bath sonication for 30 minutes was performed, and then the sols were measured in the UV/Vis spectrophotometer for absorbance (FIG. 11A). Exactly the same logic was used for boron nitride which was supplied by Thomas Swan (FIG. 11B).

[0098] For the creation of graphene-based oiled paints, blue oil paint of a well-known brand, “van Gogh” by Talens, which is used by many professionals and amateur artists, was purchased. This commercial oil paint is soluble to turpentine oil. For this application, GNPs—Electrical grade were used. A certain amount of GNPs was added in a standard amount of the paint in order to make 3 new paints with different concentrations, 1, 2 and 3% w/w graphene powder. An ultrasonic bath sonication for 30 minutes followed, and then the contact angle measurements with distilled water (FIG. 11C). The same measurement was performed for a red tempera (as described above) including increasing amounts of 1, 2 and 3% w/w of graphene powder (FIG. 11D).