PROCESS FOR PRODUCING COMPOSITE MATERIAL

Abstract

A process is disclosed comprising, providing a source of graphene, providing a particulate material, dispersing a mixture of the source of graphene and the particulate material in a first dispersion fluid to form a dispersion mixture, and providing a source of a base in the first dispersion fluid, thereby causing the source of graphene and particulate material in the dispersion mixture to interact forming a composite. The particulate material is preferably titanium dioxide comprising anatase and/or rutile which provides an effective photocatalytic composite. Also disclosed is apparatus to remove pollutants from fluids using the photocatalytically active material.

Claims

1. A process for producing a composite, the process comprising: a) providing a source of graphene, b) providing a particulate material, c) dispersing a mixture of the source of graphene and the particulate material in a first dispersion fluid to form a dispersion mixture, and d) providing a source of a base in the first dispersion fluid, thereby causing the source of graphene and particulate material in the dispersion mixture to interact forming a composite.

2. The process of claim 1, wherein the process comprises a) providing a first dispersion fluid comprising graphene or partially oxidised graphene, b) providing a particulate material, c) dispersing the particulate material in the first dispersion fluid comprising graphene or partially oxidised graphene, to form a dispersion mixture, and d) providing a base in the dispersion mixture, thereby causing the graphene and particulate material in the dispersion mixture to interact forming a composite.

3. The process according to claim 1, the process comprising a) providing graphite flakes or partially oxidised graphite flakes, b) dispersing the graphite flakes or partially oxidised graphite flakes in a first dispersion fluid, c) exfoliating the graphite flakes or partially oxidised graphite flakes in the first dispersion fluid to provide a first dispersion fluid comprising graphene or partially oxidised graphene; d) providing a particulate material, e) dispersing the particulate material in the dispersion comprising graphene or partially oxidised graphene to form a dispersion mixture, and f) providing a base in the dispersion mixture, thereby causing the graphene or partially oxidised graphene and particulate material in the dispersion mixture to interact forming a composite.

4. The process of claim 1, wherein the process comprises; a) providing graphite or partially oxidised graphite flakes, b) dispersing the graphite or partially oxidised graphite flakes in a first dispersion fluid, c) dispersing a particulate material in the first dispersion fluid to form a dispersion mixture, e) subjecting the dispersion mixture to energy to form a dispersion comprising graphene or partially oxidised graphene and the particulate material in the dispersion mixture, and f) providing a base in the dispersion mixture, thereby causing the graphene and particulate material in the dispersion mixture to interact forming a composite.

5. The process according to claim 1, wherein the source of graphene is graphene or graphite.

6. The process as claimed in claim 1, wherein the particulate material is a metal oxide.

7. The process as claimed in claim 6, wherein the metal oxide comprises titanium dioxide.

8. The process as claimed in claim 1, wherein the particulate material comprises a polysaccharide, or another polymeric material selected from polyurethane, aramid (meta- or para-), polycarbonate, PMMA, nylon (PET), PTFE, PVDF, polyaryletherketone, polypropylene carbonate, polyester, polylactic acid, polyurethane, poly(methyl methacrylate), polyvinyl alcohol, polyvinyl acetate and/or polyvinyl ester.

9. The process as claimed in claim 1, wherein the process is performed in the absence of a surfactant.

10. The process as claimed in claim 1, further comprising homogenising the dispersion mixture, preferably with a high shear mixer.

11. The process as claimed in claim 1, further comprising homogenising the source of graphene in a graphene dispersion fluid.

12. The process as claimed in claim 1, further comprising homogenising the particulate material in a material dispersion fluid.

13. The process as claimed in claim 1, further comprising sonicating the dispersion mixture.

14. The process as claimed in claim 1, further comprising sonicating the source of graphene in the graphene dispersion fluid.

15. The process as claimed in claim 1, further comprising sonicating the particulate material in the material dispersion fluid.

16. The process as claimed in claim 1, wherein the graphene and particulate material are mixed in a ratio of 3 to 500 parts by weight particulate material to 1 part by weight source of graphene.

17. The process as claimed in claim 1, wherein composite has a an I(D)/I(G) ratio at a laser excitation wavelength of 532 nm (2.33 eV), of less than 0.75.

18. The process as claimed in claim 1, wherein the source of base comprises a source of a Brønsted base and/or a source of a Lewis base.

19. The process as claimed in claim 18, wherein the source of base comprises a source of hydroxide ions.

20. The process as claimed in claim 19, wherein the source of hydroxide ions comprises an ion exchange resin, ammonia solution or an alkali solution.

21. The process as claimed in claim 18, wherein the source of hydroxide is provided at an amount of 0.5 millimoles to 20 millimoles per 10 g of metal oxide.

22. The process as claimed in claim 18, wherein the source of base comprises a ketone.

23. The process as claimed in claim 22, wherein the first dispersion fluid dispersion fluid comprises acetone.

24. The process as claimed in claim 23, wherein the first dispersion fluid comprises a mixture of acetone and water with a weight ratio of acetone to water of 0.5:1 to 6:1.

25. The process as claimed in claim 1, further comprising providing a surfactant in the first dispersion fluid.

26. The process as claimed in claim 1, wherein the first dispersion fluid comprises one or more of DMSO, acetone, water, THF, Chloroform, NMP, DMF, DMA, GBL, DMEU, Benzyl Benzoate, NVP, N12P, n-propanol, isopropanol, and/or N8P.

27. The process as claimed in claim 1, wherein the source of graphene comprises one or more of graphite flakes or graphene flakes.

28. The process as claimed in claim 27, wherein the source of graphene comprises graphite flakes and the process further comprises providing a graphite dispersion of graphite flakes in a graphene dispersion fluid and homogenising the graphite dispersion, thereby forming a dispersion comprising graphene.

29. The process as claimed in claim 1, wherein the particulate material has a particle size in the range 5 nm to 1 μm.

30. The process as claimed in claim 1, further comprising recovering the composite, and optionally recovering the dispersion fluid.

31. The process as claimed in claim 1, wherein the process is conducted at a temperature in the range 0° C. to 260° C.

32. (canceled)

33. A process for producing a photocatalytically active composite, the process comprising: a) providing a source of graphene, b) providing titanium dioxide in particulate form, c) dispersing a mixture of the source of graphene and titanium dioxide in a first dispersion fluid to form a dispersion mixture, and d) providing a source of a base in the first dispersion fluid, thereby causing the source of graphene and titanium dioxide in the dispersion mixture to interact forming a photocatalytically active composite.

34-36. (canceled)

Description

[0115] Embodiments of the present invention will now be described with reference to the following figures, in which:

[0116] FIG. 1 shows a graph of reduction of methylene blue concentration against UV irradiation time for Example 1, Example 2 and a control (particulate anatase, 25 nm particle size)

[0117] FIG. 2 shows graphs of (a) UV visible reflectance for Example 1, and (b) UV visible reflectance for Example 2.

[0118] FIG. 3 shows (a) an XPS survey of Example 1, and (b) detail of the XPS results for Example 1.

[0119] FIG. 4 shows a normalised Raman spectrum of Example 1.

[0120] FIG. 5 shows an IR spectrum of Example 2.

[0121] FIG. 6. Extended Raman spectrum of a titanium dioxide-graphene composite of Example 1. The data is the same as for FIG. 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0122] FIG. 7. Raman spectrum of a titanium dioxide-graphene composite produced via the process described in Example 1, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0123] FIG. 8. Extended Raman spectrum of a zirconium oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0124] FIG. 9. Raman spectrum of a zirconium oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0125] FIG. 10. Raman spectrum of a zirconium oxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0126] FIG. 11. Extended Raman spectrum of an antimony tin oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0127] FIG. 12. Raman spectrum of an antimony tin oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0128] FIG. 13. Raman spectrum of an antimony tin oxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0129] FIG. 14. Extended Raman spectrum of a barium titanate (cubic structure)-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0130] FIG. 15. Additional extended Raman spectrum of a barium titanate (cubic structure)-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0131] FIG. 16. Raman spectrum of a barium titanate (cubic structure)-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0132] FIG. 17. Raman spectrum of a barium titanate (cubic structure)-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0133] FIG. 18. Extended Raman spectrum of a tungsten trioxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0134] FIG. 19. Additional extended Raman spectrum of a tungsten trioxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0135] FIG. 20. Raman spectrum of a tungsten trioxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0136] FIG. 21. Raman spectrum of a tungsten trioxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks.

[0137] Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0138] FIG. 22. Extended Raman spectrum of an aluminium oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0139] FIG. 23. Raman spectrum of an aluminium oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0140] FIG. 24. Raman spectrum of an aluminium oxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0141] FIG. 25. Extended Raman spectrum of a copper oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0142] FIG. 26. Raman spectrum of a copper oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0143] FIG. 27. Extended Raman spectrum of a zinc oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0144] FIG. 28. Raman spectrum of a zinc oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0145] FIG. 29. Raman spectrum of a zinc oxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0146] FIG. 30. Extended Raman spectrum of a tin oxide-graphene composite produced via the process described in method 4. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0147] FIG. 31. Raman spectrum of a tin oxide-graphene composite produced via the process described in method 4, highlighting the 2D graphene peak. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0148] FIG. 32. Raman spectrum of a tin oxide-graphene composite produced via the process described in method 4, highlighting the D, G and D′ graphene peaks. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0149] FIG. 33. X-ray powder diffraction pattern of a zirconium oxide-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0150] FIG. 34. X-ray powder diffraction pattern of an antimony tin oxide-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0151] FIG. 35. X-ray powder diffraction pattern of a barium titanate (cubic structure)-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0152] FIG. 36. X-ray powder diffraction pattern of a tungsten trioxide-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0153] FIG. 37. X-ray powder diffraction pattern of an aluminium oxide-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0154] FIG. 38. X-ray powder diffraction pattern of a copper oxide-graphene composite produced via the process described in method 4. Pattern was collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 A°).

[0155] FIG. 39: Raman spectrum of an aluminium oxide-xGNP composite produced via the process described in method 8. Spectrum was collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm.

[0156] FIG. 40: Photos of graphene/metal oxide composite synthesis procedure detailed in method 4, with antimony-doped tin oxide as the model metal oxide. Similar behaviours are seen for different metal oxides—all tested with method 4 formed a flocculated product, which could be collected and characterised with Raman Spectroscopy.

Photos show:
a) 50 mg of the initial metal oxide powder,
b) The mixture of metal oxide powder and the graphene dispersion (5 ml),
c) The composite settling/flocculating out of dispersion once the base (50 microlitres of 1M NaOH) is added. The transparent nature of the supernatant indicates that the base has caused the previously dispersed graphene to interact with the metal oxide material, to form a flocculated product.

[0157] FIG. 41: photos of graphene/polymer composite procedure detailed in example 9, with PVA-stabilised PLA as the model polymer. Photos show:

a) The mixture of PLA and graphene dispersion after 2 minutes sonication, where the mixture is homogeneous and stable.
b) The mixture 3 minutes after adding base (˜50 microlitres of saturated ammonium carbonate solution), where some precipitated composite is seen on the sides of the glass tube, likely deposited from the mixture solution during the sonication and agitation step. A darker mass is seen at the bottom of the tube, indicating the formation of a flocculated product.
c) A clearer image of the flocculated product, taken 5 minutes after the addition of base. Some of the supernatant has been removed to allow easier identification of the flocculated product. Here, gelled/coagulated composite is seen on the tube walls, the solution has turned semitransparent, and a darker material is observed at the bottom of the tube. This indicates the formation of a homogeneous composite of graphene and PLA.

[0158] FIG. 42: the rubbery grey solid formed using the method described in example 5. Most of the supernatant has been removed to facilitate better viewing of the product formed.

[0159] FIG. 43: Photos detail of method 6, the formation of a graphene/metal oxide product using volatile ammonium salts. Photos show:

a) Mixture of TiO2 (50 mg) and graphene dispersion (5 ml) after 2 min sonication.
b) The mixture after adding the base (saturated ammonium carbonate solution, 50 microlitres). A floc forms rapidly, and in this case, the floc is grey due to the combination of graphene (black) and TiO2 (white).
c) An image of the flocculated product after the solution was left to stand for 2 minutes after addition of base and sonication. An additional source of light is used to illuminate the glass cylinder from below, to help view the flocculated product.

[0160] FIG. 44. Curve fitting of the measured Raman D peak (Curve 1) of an aluminium oxide-graphene composite produced via method 4. I(D) is taken to be the height of Curve 1 (=4738.26) for ratio calculations.

[0161] FIG. 45. Curve fitting and deconvolution of the measured Raman G peak (Curve 1) and D′ peak (Curve 2) of an aluminium oxide-graphene composite produced via method 4. I(G) is taken to be the height of Curve 1 (=14324.2), and I(D′) is taken to be the height of Curve 2 (=1470.11) for ratio calculations.

[0162] FIG. 46. Curve fitting of the measured Raman D peak (Curve 1) of an antimony tin oxide-graphene composite produced via method 4. I(D) is taken to be the height of Curve 1 (=2584.33) for ratio calculations.

[0163] FIG. 47. Curve fitting and deconvolution of the measured Raman G peak (Curve 1) and D′ peak (Curve 2) of an antimony tin oxide-graphene composite produced via method 4. I(G) is taken to be the height of Curve 1 (=5425.51), and I(D′) is taken to be the height of Curve 2 (=841.649) for ratio calculations.

[0164] FIG. 48. Curve fitting of the measured Raman D peak (Curve 1) of a barium titanate (cubic structure)-graphene composite produced via the method 4. I(D) is taken to be the height of Curve 1 (=9677.43) for ratio calculations.

[0165] FIG. 49. Curve fitting and deconvolution of the measured Raman G peak (Curve 1) and D′ peak (Curve 2) of a barium titanate (cubic structure)-graphene composite produced via method 4. I(G) is taken to be the height of Curve 1 (=18809.9), and I(D′) is taken to be the height of Curve 2 (=2841.43) for ratio calculations.

[0166] FIG. 50. Curve fitting of the measured Raman D peak (Curve 1) of a titanium dioxide-graphene composite produced via method 4. I(D) is taken to be the height of Curve 1 (=1285.44) for ratio calculations.

[0167] FIG. 51. Curve fitting and deconvolution of the measured Raman G peak (Curve 1) and D′ peak (Curve 2) of a titanium dioxide-graphene composite produced via method 4. I(G) is taken to be the height of Curve 1 (=5067.33), and I(D′) is taken to be the height of Curve 2 (=508.08) for ratio calculations.

[0168] FIG. 52. Curve fitting of the measured Raman D peak (Curve 1) of a zirconium oxide-graphene composite produced via method 4. I(D) is taken to be the height of Curve 1 (=1934.54) for ratio calculations.

[0169] FIG. 53. Curve fitting and deconvolution of the measured Raman G peak (Curve 1) and D′ peak (Curve 2) of a zirconium oxide-graphene composite produced via method 4. I(G) is taken to be the height of Curve 1 (=6466.57), and I(D′) is taken to be the height of Curve 2 (=685.583) for ratio calculations.

[0170] FIG. 54. Curve fitting of the measured Raman 2D peak (Curve 1) of an aluminium oxide-graphene composite produced via method 4. Peak centre=2698.62 cm.sup.−1.

[0171] FIG. 55. Curve fitting of the measured Raman 2D peak (Curve 1) of an antimony tin oxide-graphene composite produced via method 4. Peak centre=2700.95 cm.sup.−1.

[0172] FIG. 56. Curve fitting of the measured Raman 2D peak (Curve 1) of a barium titanate (cubic structure)-graphene composite produced via method 4. Peak centre=2698.28 cm.sup.−1.

[0173] FIG. 57. Curve fitting of the measured Raman 2D peak (Curve 1) of a titanium dioxide-graphene composite produced via method 4. Peak centre=2693.87 cm.sup.−1.

[0174] FIG. 58. Curve fitting of the measured Raman 2D peak (Curve 1) of a zirconium oxide-graphene composite produced via method 4. Peak centre=2696.75 cm.sup.−1.

[0175] FIG. 59. Raman spectrum of a tin oxide-xGNP composite produced via method 8, highlighting the D, G and D′ graphene peaks. Laser excitation wavelength=532 nm.

[0176] FIG. 60. Raman spectrum of a tin oxide-xGNP composite produced via method 8, highlighting the 2D graphene peak. Laser excitation wavelength=532 nm.

[0177] FIG. 61. Extended Raman spectrum of a tin oxide-xGNP composite produced via method 8. Laser excitation wavelength=532 nm.

[0178] FIG. 62. Raman spectrum of a polyurethane-graphene composite produced via example 5. Laser excitation wavelength=532 nm.

[0179] FIG. 63. Raman spectrum of a polyurethane-graphene composite produced via example 5. Laser excitation wavelength=532 nm.

[0180] FIG. 64. Extended Raman spectrum of a polyurethane-graphene composite produced via example 5. Laser excitation wavelength=532 nm.

[0181] FIG. 65. Raman spectrum of a chitosan-graphene composite produced via example 4. Laser excitation wavelength=532 nm.

[0182] FIG. 66. Raman spectrum of a Poly(methyl methacrylate)-graphene composite produced via example 8. Laser excitation wavelength=532 nm.

[0183] FIG. 67. Raman spectrum of a Poly(methyl methacrylate)-graphene composite produced via example 8. Laser excitation wavelength=532 nm.

[0184] FIG. 68. A version of FIG. 6 with labelled Raman peaks of interest.

[0185] The present invention is further illustrated by the following examples.

EXAMPLES

[0186] Composites of graphene and other materials were produced using the following methods. Table 1, below indicates the amount of starting materials and method for each Example.

Method 1.

[0187] Graphite flakes (25 g) were dispersed in 500 ml DMSO via high-shear homogenisation (Silverson LSM, with 25 mm square-hole screen, used at 5000 RPM) for 20 min, followed by centrifugation at 420 g for 20 min. Anatase nanoparticles (25 nm, Sigma, 0.1 g) were added to the resulting supernatant (40 ml) to produce graphene/titanium dioxide dispersions. The dispersions were further dispersed for 10 minutes with sonication. Base (0.01-1 ml, NaOH, 1M in water) was added to the dispersions, yielding a precipitate. The precipitate was left to settle. The supernatant was then removed and the material separated and washed with water.

Method 2.

[0188] Graphite flakes (0.2 g) and titanium dioxide particles (10 g, Titanium dioxide, 25 nm, sigma) were added to a mixture of 500 ml DMSO and 0.1M NaOH in water (10 ml), and exfoliated with high-shear homogenization (Silverson LSM, with 25 mm square-hole screen, used at 5000 RPM) for 30 min. The precipitate was left to settle for a further 30 minutes, and collected.

Method 3.

[0189] Graphite flakes (0.5 g) and Chitosan (1 g, dispersion in 1% acetic acid in water) were added to a mixture of 500 ml DMSO, and the graphite exfoliated with high-shear homogenization (Silverson L5M-A, with 25 mm square-hole screen, used at 5000 RPM) for 30 min. 0.1M NaOH in water (10 ml) was added. The precipitate was left to settle for a further 30 minutes, and separated. The supernatant can, if desired, be neutralized with an appropriate amount of acid and re-used.

Method 4—Acetone/Water-Based Metal Oxide/Graphene Synthesis

[0190] This method was used to prepare 6 metal oxide/graphene composites from graphene and: zirconium oxide, <100 nm, (sigma-aldrich); antimony tin oxide, <50 nm (sigma-aldrich); barium titanate, cubic crystalline phase, <100 nm, (sigma-aldrich); tungsten (VI) trioxide, <100 nm, (sigma-aldrich); aluminium oxide, <13 nm, (sigma-aldrich); copper (II) oxide, <50 nm, (sigma-aldrich); zinc oxide, <50 nm, (sigma-aldrich); tin oxide, <100 nm, (sigma-aldrich).
Graphene dispersion was prepared using the following procedure adapted from Paton et al.
50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml dispersion fluid, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed at maximum homogenising power for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This method typically yields a graphene concentration of 0.01-0.05 mg/ml.
50 mg of a metal oxide and 5 ml graphene dispersion were mixed, and sonicated for 30 seconds. Some metal oxides are not easily dispersed in the acetone/water mixture, and settled out rapidly without forming a composite with the graphene. 50 microlitres of 1M sodium hydroxide solution was then added to the mixture, which was then sonicated for a further 30 seconds to yield a homogeneous mixture. A homogenous precipitate was observed within a few minutes, which was collected and analysed with pXRD and Raman spectroscopy—FIGS. 8-38.
The general appearance of solutions for preparing metal oxide/graphene composites with this method can be followed in FIG. 40—Antimony oxide/Tin oxide is used as a model metal oxide.
Method 5—Synthesis with Barium Hydroxide
Cubic barium titanate was contacted with graphene dispersion in the same manner as example 1, but 600 microlitres of 0.1M barium hydroxide aqueous solution was used instead of 1M sodium hydroxide aqueous solution. This yielded a product free of sodium ion contamination.

Method 6—Synthesis to Yield Product Using Volatile Salts

[0191] A metal oxide/graphene composite was prepared with titanium dioxide as the metal oxide, contacted with graphene dispersion in the same manner as method 4, but using 50 microlitres of saturated ammonium carbonate aqueous solution instead of 1M sodium hydroxide aqueous solution. The process can be followed in FIG. 43.
Method 7—Synthesis with Organic Base

[0192] A metal oxide/graphene composite was prepared with titanium dioxide as the metal oxide, contacted with 5 ml graphene dispersion in the same manner as method 4, but using 1000 microlitres of 1M sodium citrate aqueous solution instead of 1M sodium hydroxide aqueous solution.

Method 8—Synthesis to Yield Product with xGNP Nanoplatelets

[0193] This method was used to prepare composites of xGNP with aluminium oxide and tin oxide, characterised with raman spectroscopy in FIGS. 39 (Aluminium oxide) and 59 (tin oxide).

[0194] xGNP dispersion was prepared using the following procedure:

[0195] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of xGNP flakes were prepared by sonicating a mixture of 0.02 g xGNP in 200 ml dispersion fluid, with a Cole-Parmer 100 W ultrasonic cleaner. Sonicating was performed for 20 minutes in a water bath at 21 degrees centigrade. This sonicated mixture was used directly as an xGNP dispersion.

[0196] 10 ml xGNP dispersion was contacted with 0.01 g metal oxide (tin oxide or aluminium oxide) and sonicated for 2 minutes. To this mixture, 50 microlitres of 1M NaOH aqueous solution was added, and the resulting mixture sonicated for 2 minutes. The product was left to settle for 30 minutes, collected, and dried.

Example 1

[0197] Example 1 was produced using method 1.

Example 2

[0198] Example 2 was produced using method 1 and then heat treated at 300° C. for 3 hours under vacuum.

Photocatalytic Activity

[0199] The photocatalytic activity of the composites of graphene with titanium dioxide was determined as follows.
0.7 mg/ml material was dispersed by sonication in 100 ml aqueous solution of 2.15 mg/dm.sup.3 methylene blue, and left to equilibrate overnight. Material dispersions were added to a Pyrex UV batch photoreactor (120 ml capacity) equipped with a 125 W medium-pressure mercury lamp. Material dispersions were exposed to UV light for 35 minutes. 2 ml aliquots were removed from the reactor at 0, 10, 20, and 35 minutes. A Shimadzu UV2700 UV-Vis spectrometer was used to record the transmittance of the aliquots at 665 nm. Graph fitting done with Origin software. The results for two composite materials (Examples 1 and 2) according to the invention and controls (anatase 25 nm particle size and methylene blue) are shown in FIG. 1. A measure of the effectiveness of photocatalytic activity was determined from the reduction in the measured concentration of methylene blue and is as indicated in Table 1, below with the values being a time constant.

TABLE-US-00001 TABLE 1 Value Material (min) Anatase 25 nm particle size 25.4 (Control) Example 1 8.2 Example 2 8.8

[0200] Reflectance spectra of Examples 1 and 2 are shown in FIGS. 2(a) and (b) respectively.

[0201] XPS spectra of Example 1 is shown in FIG. 3 showing an XPS survey scan in FIG. 3(a) and in detail (FIG. 3(b)—indicating very few impurities within the material. XPS was obtained by KE Energy Step in eV 0.5, Number of Sweeps 2, Dwell Time per Sweep in s 0.25, Excitation Source Al Kα; Excitation Energy in eV 1486.7; Exit Slit 5×11 mm.

[0202] A typical normalised Raman spectrum of Example 1 is shown in FIG. 4 with (left-right) the D peak, the G peak, and the 2D peak of graphene (or few-layer graphene). The sharpness of 2D peak indicates the number of layers, showing at least few-layer graphene. Raman was obtained with a Renishaw InVia Confocal Raman Microscope.

[0203] FIG. 5 shows an IR spectrum of Example 2 (obtained with a Perkin Elmer Spectrum Two FT-IR Spectrometer). The two peaks either side of 1500 cm.sup.−1 may be C═C peaks (contributions from graphene and titania), the large broad peak to the left is from titanium dioxide (anatase). The absence of strong carbonyl peaks indicates the high quality of the graphene.

Example 3—Chitosan with DMSO and NaOH

[0204] Graphene dispersion was prepared using the following procedure adapted from Paton et al (Nature Materials volume 13, pages 624-630 (2014), or WO2014140324A1):

[0205] A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml DMSO, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed at max homogenising power for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This yielded ˜160 ml graphene dispersion. This method typically yields a graphene concentration of 0.01-0.05 mg/ml.

[0206] 1% Chitosan in 1% acetic acid solution was prepared by adding 0.5 g chitosan and 0.5 ml acetic acid into 49.5 ml distilled water. 1 ml of this chitosan solution was then added to 1 ml graphene dispersion and sonicated for 2 minutes to form a mixture. To this mixture, 50 microlitres of 1M sodium hydroxide solution was added, under vigorous agitation. This resulted in the formation of a flocculated composite product.

Example 4—Chitosan with Acetone/Water Cosolvent Mixture and Sodium Citrate

[0207] Graphene dispersion was prepared using the following procedure adapted from Paton et al (Nature Materials volume 13, pages 624-630 (2014), or WO2014140324A1):

[0208] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml dispersion fluid, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This yielded ˜160 ml graphene dispersion. This method typically yields a graphene concentration of 0.01-0.05 mg/ml.

[0209] 1% Chitosan in 1% acetic acid solution was prepared by adding 0.5 g chitosan and 0.5 ml acetic acid into 49.5 ml distilled water. 1 ml of this chitosan solution was then added to 3 ml graphene dispersion and sonicated for 2 minutes to form a mixture. To this mixture, 50 microlitres of 1M sodium citrate aqueous solution was added, under vigorous agitation. This resulted in the formation of a flocculated composite product characterised by Raman spectroscopy in FIG. 65.

Example 5—Polyurethane (PU), DMSO, and Ammonium Carbonate

[0210] Graphene dispersion was prepared using the following procedure adapted from Paton et al or WO2014140324A1):

[0211] A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml DMSO, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This yielded ˜160 ml graphene dispersion. This method typically yields a graphene concentration of 0.01-0.05 mg/ml.

[0212] A water-based biodegradable polyurethane nanoparticle emulsion was synthesised following the protocol described by Chen et al (2014).

[0213] Under inert atmosphere, 10.24 g of Poly-e-caprolactone diol (5 mmol) and 3.99 ml IPDI (19 mmol) were reacted for 3 hours (180 rpm) at 75 C. Approximately 0.8 ml of 2-Butanol and 0.71 g of DMPA (5 mmol) were then added against high nitrogen flow. The reaction was cooled down to 45 C, 0.696 ml triethylamine (TEA, 5 mmol) was syringed into the reaction flask and the mixture was stirred for 30 minutes. 36 ml DI water was quickly added against vigorous sitting (1200 rpm) for 2 minutes, after which the stirring was brought back to 180 rpm. 0.51 ml ethylenediamine (EDA, 8 mmol) was added and the reaction was stirred for further 30 minutes. The milky colloidal dispersion was collected, centrifuged and washed twice with DI water (3000 rpm, for 15 and 30 minutes) to yield a 15 w % emulsion.

[0214] Adapted from Chen, Y.-P., & Hsu, S. (2014). ‘Preparation and characterization of novel water-based biodegradable polyurethane nanoparticles encapsulating superparamagnetic iron oxide and hydrophobic drugs.’ J. Mater. Chem. B, 2(21), 3391-3401. Doi:10.1039/c4tb00069b

[0215] 1 ml PU emulsion and 3 ml graphene dispersion were added into a test tube and mixed together. The mixture was sonicated for 2 minutes. 1 ml saturated ammonium bicarbonate solution in DI water was added to the mixture, which was sonicated for a further 2 minutes. A grey/black floc was observed (FIG. 42), which was collected and characterised with raman spectroscopy (FIG. 64).

Example 6—xGNP with Chitosan and Sodium Citrate

[0216] xGNP dispersion was prepared using the following procedure:

[0217] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of xGNP flakes were prepared by sonicating a mixture of 0.02 g xGNP in 200 ml dispersion fluid, with a Cole-Parmer 100 W ultrasonic cleaner. Sonicating was performed for 20 minutes in a water bath at 21 degrees centigrade. This sonicated mixture was used directly as an xGNP dispersion.

[0218] 1% Chitosan in 1% acetic acid solution was prepared by adding 0.5 g chitosan and 0.5 ml acetic acid into 49.5 ml distilled water. 1 ml of this chitosan solution was then added to 10 ml xGNP dispersion and sonicated for 2 minutes to form a mixture. To this mixture, 50 microlitres of 1M sodium citrate aqueous solution was added, under vigorous agitation. This resulted in the formation of a black flocculated composite product.

Example 7—xGNP with PU, NaOH, and Limewater

[0219] xGNP dispersion was prepared using the following procedure:

[0220] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of xGNP flakes were prepared by sonicating a mixture of 0.02 g xGNP in 200 ml dispersion fluid, with a Cole-Parmer 100 W ultrasonic cleaner. Sonicating was performed for 20 minutes in a water bath at 21 degrees centigrade. This sonicated mixture was used directly as an xGNP dispersion.

[0221] A water-based biodegradable polyurethane nanoparticle emulsion was synthesised following the protocol described by Chen et al (Chen, Y.-P., & Hsu, S. (2014). Preparation and characterization of novel water-based biodegradable polyurethane nanoparticles encapsulating superparamagnetic iron oxide and hydrophobic drugs. J. Mater. Chem. B, 2(21), 3391-3401. Doi: 10.1039/c4tb00069b). Under inert atmosphere, 10.24 g of Poly-e-caprolactone diol (5 mmol) and 3.99 ml IPDI (19 mmol) were reacted for 3 hours (180 rpm) at 75 C. Approximately 0.8 ml of 2-Butanol and 0.71 g of DMPA (5 mmol) were then added against high nitrogen flow. The reaction was cooled down to 45 C, 0.696 ml triethylamine (TEA, 5 mmol) was syringed into the reaction flask and the mixture was stirred for 30 minutes. 36 ml DI water was quickly added against vigorous sitting (1200 rpm) for 2 minutes, after which the stirring was brought back to 180 rpm. 0.51 ml ethylenediamine (EDA, 8 mmol) was added and the reaction was stirred for further 30 minutes. The milky colloidal dispersion was collected, centrifuged and washed twice with DI water (3000 rpm, for 15 and 30 minutes) to yield a 15 w % emulsion of PU particles in water.

[0222] 200 microlitres of 1M NaOH aqueous solution was contacted with 30 ml graphene dispersion and 200 microlitres of PU emulsion. This mixture was sonicated for 30 seconds. 10 ml saturated Ca(OH)2 solution (limewater) was then added under vigorous agitation. A grey-black flocculated product was observed.

Example 8—PMMA with Acetone/Water Graphene Dispersion Fluid and Saturated Ammonium Carbonate Solution

[0223] Graphene dispersion was prepared using the following procedure adapted from Paton et al (Nature Materials volume 13, pages 624-630 (2014), or WO2014140324A1):

[0224] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml dispersion fluid, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This yielded ˜160 ml graphene dispersion.

[0225] PMMA nanoparticles were synthesised by surfactant-free emulsion, as described by Tahrin et al (2017). In a 250 ml round-bottomed flask equipped with a condenser, 65 ml DI water was heated to 90 C under inert atmosphere. 15 ml MMA monomer was added against high nitrogen flow, followed by 2.85 g of potassium persulfate, The reaction mixture was refluxed for 45 minutes with stirring (300 rpm). The mixture was then let to cool at room temperature and the white colloidal liquid was collected, centrifuged (3000 rpm) and washed with DI water until an opal hue could be observed in the translucent liquid phase of the centrifuge vial. This method typically yielded a 0.2-1 w % solution.

[0226] Tahrin, R. A. A., Azma, N. S., Kassim, S., & Harun, N. A. (2017). Preparation and properties of PMMA nanoparticles as 3 dimensional photonic crystals and its thin film via surfactant-free emulsion polymerization. Doi: 10.1063/1.5002286

[0227] 3 ml of PMMA suspension was added to 3 ml graphene dispersion and sonicated for 2 minutes. To this mixture, 200 microlitres of saturated ammonium carbonate solution was added, and the mixture agitated and sonicated for 2 further minutes. After a few minutes, a black floc was observed. This was collected, dried, and characterised by Raman spectroscopy (FIG. 66-67).

Example 9—Polylactic Acid with Acetone/Water Mixture and Ammonium Carbonate

[0228] Graphene dispersion was prepared using the following procedure adapted from Paton et al (Nature Materials volume 13, pages 624-630 (2014), or WO2014140324A1):

[0229] 50 g distilled water and 150 g acetone were mixed to form a dispersion fluid. A dispersion of graphite and graphene flakes were prepared by homogenising a mixture of 10 g graphite in 200 ml dispersion fluid, with a Silverson L4R high-shear mixer equipped with a ¾″ tubular head and a ‘square hole high shear screen’ attachment. Homogenising was performed for 20 minutes in a water bath at 21 degrees centigrade. This homogenised mixture was then centrifuged for 20 minutes at 3,500 RPM to remove unexfoliated graphite flakes. This yielded ˜160 ml graphene dispersion. This method typically yields a graphene concentration of 0.01-0.05 mg/ml.

[0230] PVA-stabilised polylactic acid nanoparticles were synthesized via O/W emulsion and solvent extraction evaporation technique, as reported by Sathyamoorthy et al. (2017). In a beaker, 0.1 g of the selected polymer was dissolved in 5 ml of methylene chloride. The polymer solution was added in a dropwise manner to 25 ml of 1 wt % PVA solution in water and sonicated in an ice bath for 10 intervals of 5 seconds. The emulsion was then added to 50 ml of 0.5 wt % aqueous PVA in a rate of 2 ml/min. The resulting dispersion was homogenized for 10 minutes, forming a white foam. The reaction mixture was stirred overnight to allow the evaporation of the organic solvent, and was washed with DI water and centrifuged twice at 4500 rpm for 30 minutes. This method typically yields a concentration of 0.8-1.5 w %, most often 1.1 w %.

[0231] Sathyamoorthy, N., Magharla, D., Chintamaneni, P., & Vankayalu, S. (2017). Optimization of paclitaxel loaded poly (e-caprolactone) nanoparticles using Box Behnken design. Beni-Suef University Journal of Basic and Applied Sciences, 6(4), 362-373. Doi: 10.1016/j.bjbas. 2017.06.002

[0232] 1 ml of PLA suspension was added to 3 ml graphene dispersion and sonicated for 2 minutes. To this mixture, 200 microlitres of saturated ammonium carbonate solution was added, and the mixture agitated and sonicated for 2 further minutes. After a few minutes, a black floc was observed. The general process steps can be observed in FIG. 41.

Regarding the experimental methods disclosed herein:
WiRE™ (a dedicated software package for Raman spectroscopy) was used for curve fitting in order to determine Raman peak intensities, widths, positions and areas as shown in FIGS. 44 to 57.

[0233] Raman spectra were collected using a Renishaw inVia Raman microscope with laser excitation wavelength=532 nm. XRD patterns were collected using a STOE diffractometer operated in transmission with a PSD detector and a germanium monochromator (Cu K-alpha1 radiation wavelength=1.540598 Å).

TABLE-US-00002 TABLE 2 calculated I(D)/I(G) and I(D)/I(D′) ratios for 5 different composites produced via method 4 using I(D), I(G) and I(D′) values from FIGS. 44 to 53. Calculated Composite I(D)/I(G) I(D)/I(D′) from FIGS. Titanium dioxide-graphene 0.25 2.53 50 and 51 Antimony tin oxide-graphene 0.48 3.07 46 and 47 Zirconium oxide-graphene 0.30 2.82 52 and 53 Barium titanate 0.51 3.41 48 and 49 (cubic structure)-graphene Aluminium oxide-graphene 0.33 3.22 44 and 45
Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.
Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.
For the avoidance of doubt, it is hereby stated that the information disclosed earlier in this specification under the heading “Background” is relevant to the invention and is to be read as part of the disclosure of the invention.
Where a composition/item is said to comprise a plurality of stipulated ingredients (optionally in stipulated amounts of concentrations), said composition/item may optionally include additional ingredients other than those stipulated. However, in certain embodiments, a composition/item said to comprise a plurality of stipulated ingredients may in fact consist essentially of or consist of all the stipulated ingredients.
Herein, where a composition is said to “consists essentially of” a particular component, said composition suitably comprises at least 70 wt % of said component, suitably at least 90 wt % thereof, suitably at least 95 wt % thereof, most suitably at least 99 wt % thereof. Suitably, a composition said to “consist essentially of” a particular component consists of said component save for one or more trace impurities.
Where the quantity or concentration of a particular component of a given composition is specified as a weight percentage (% weight, wt % or % w/w), said weight percentage refers to the percentage of said component by weight relative to the total weight of the composition as a whole. It will be understood by those skilled in the art that the sum of weight percentages of all components of a composition will total 100 wt %. However, where not all components are listed (e.g. where compositions are said to “comprise” one or more particular components), the weight percentage balance may optionally be made up to 100 wt % by unspecified ingredients (e.g. a diluent, such as water, or other non-essentially but suitable additives).
Herein, unless stated otherwise, the term “parts” (e.g. parts by weight, pbw) when used in relation to multiple ingredients/components, refers to relative ratios between said multiple ingredients/components. Expressing molar or weight ratios of two, three or more components gives rise to the same effect (e.g. a molar ratio of x, y, and z is x1:y1:z1 respectively, or a range x1-x2:y1-y2:z1-z2). Though in many embodiments the amounts of individual components within a composition may be given as a “wt %” value, in alternative embodiments any or all such wt % values may be converted to parts by weight (or relative ratios) to define a multi-component composition. This is so because the relative ratios between components is often more important than the absolute concentrations thereof in the compositions (i.e., solid dosage forms such as the extruded items/embedded items and/or mixtures used to prepare said solid dosage forms such as the extrudable composition/embeddable substance/solidifiable body substance) of the invention. Where a composition comprises multiple ingredients is described in terms of parts by weight alone (i.e. to indicate only relative ratios of ingredients), it is not necessary to stipulate the absolute amounts or concentrations of said ingredients (whether in total or individually) because the advantages of the invention can stem from the relative ratios of the respective ingredients rather than their absolute quantities or concentrations. However, in certain embodiments, such compositions consists essentially of or consist of the stipulated ingredients and a diluents (e.g. water).
The term “mole percent” (i.e. mol %) is well understood by those skilled in the art, and the mol % of a particular constituent means the amount of the particular constituent (expressed in moles) divided by the total amount of all constituents (including the particular constituent) converted into a percentage (i.e. by multiplying by 100). The concept of mol % is directly related to mole fraction.
The term “substantially free”, when used in relation to a given component of a composition (e.g. “a liquid pharmaceutical composition substantially free of compound X”), refers to a composition to which essentially none of said component is present. When a composition is “substantially free” of a given component, said composition suitably comprises no more than 0.001 wt % of said component, suitably no more than 0.0001 wt % of said component, suitably no more than 0.00001 wt %, suitably no more than 0.000001 wt %, suitably no more than 0.0000001 wt % thereof, most suitably no more than 0.0001 parts per billion (by weight).
The term “entirely free”, when used in relation to a given component of a composition (e.g. “a liquid pharmaceutical composition entirely free of compound X”), refers to a composition containing none of said component.
Suitably, unless stated otherwise, where reference is made to a parameter (e.g. pH, pKa, etc.) or state of a material (e.g. liquid, gas, etc.) which may depend on pressure and/or temperature, suitably in the absence of further clarification such a reference refers to said parameter at standard ambient temperature and pressure (SATP). SATP is a temperature of 298.15 K (25° C., 77° F.) and an absolute pressure of 100 kPa (14.504 psi, 0.987 atm).
Suitably, unless stated otherwise, where reference is made to a boiling point, a melting point, or a glass transition (softening) temperature of a component, such reference refers to said parameter being measured at standard ambient pressure. Standard ambient pressure is an absolute pressure of 100 kPa (14.504 psi, 0.978 atm).
The following numbered clauses 1-21 are not claims, but instead serve to define particular aspects and embodiments of the invention.
1. A process for producing a composite, the process comprising:

[0234] a) providing a source of graphene,

[0235] b) providing a particulate material,

[0236] c) dispersing a mixture of the source of graphene and the particulate material in a first dispersion fluid to form a dispersion mixture, and

[0237] d) providing a source of a base in the first dispersion fluid,

thereby causing the source of graphene and particulate material in the dispersion mixture to interact forming a composite.
2. A process of clause 1, wherein the particulate material is a metal oxide.
3. A process of either clause 1 or clause 2, wherein the particulate material is a photocatalytic metal oxide.
4. A process of clause 3, wherein the photocatalytic metal oxide comprises titanium dioxide, preferably titanium dioxide comprising anatase and/or rutile, even more preferably titanium dioxide comprising a mixture of anatase and rutile.
5. A process of any one of the preceding clauses, wherein the particulate material comprises a polysaccharide, preferably chitosan.
6. A process of any one of the preceding clauses, further comprising homogenising the dispersion mixture, preferably with a high shear mixer.
7. A process of any one of the preceding clauses, further comprising homogenising the source of graphene in a graphene dispersion fluid, preferably with a high shear mixer.
8. A process of any one of the preceding clauses, further comprising homogenising the particulate material in a material dispersion fluid, preferably with a high shear mixer.
9. A process of any one of the preceding clauses, further comprising sonicating the dispersion mixture.
10. A process of any one of the preceding clauses, further comprising sonicating the source of graphene in the graphene dispersion fluid.
11. A process of any one of the preceding clauses, further comprising sonicating the particulate material in the material dispersion fluid.
12. A process of any one of the preceding clauses, further comprising forming the mixture of the source of graphene and the particulate material in an amount of 0.01 to 10000 parts by weight particulate material to 1 part by weight source of graphene (calculated as graphene).
13. A process of any one of the preceding clauses, wherein the source of base comprises a source of a Brønsted base and/or a source of a Lewis base.
14. A process of clause 13, wherein the source of base comprises a source of hydroxide ions.
15. A process of clause 14, wherein the source of hydroxide ions comprises an ion exchange resin, ammonia solution or an alkali solution.
16. A process of clause 14 or clause 15, wherein the source of hydroxide is provided at an amount of 0.5 millimoles to 20 millimoles per 10 g of metal oxide, preferably per 10 g titanium dioxide.
17. A process of any one of clauses 13 to 15, wherein the source of base comprises a ketone, preferably acetone.
18. A process of clause 17, wherein the first dispersion fluid dispersion fluid comprises acetone.
19. A process of clause 18, wherein the first dispersion fluid comprises a mixture of acetone and water with a weight ratio of acetone to water of 0.5:1 to 6:1, preferably 1:1 to 5:1, more preferably 2:1 to 4:1 and most preferably about 3:1.
20. A process of any one of the preceding clauses, further comprising providing a surfactant in the first dispersion fluid.
21. A process of any one of the preceding clauses, wherein the graphene dispersing liquid, the particulate material dispersing liquid and/or the first dispersing liquid comprise one or more of DMSO, acetone, water, THF, Chloroform, NMP, DMF, DMA, GBL, DMEU, Benzyl Benzoate, NVP, N12P, n-propanol, isopropanol, and/or N8P.
22. A process of any one of the preceding clauses, wherein the source of graphene comprises one or more of graphite, graphene, graphene oxide, reduced graphene oxide, and functionalised graphene.
23. A process of clause 22, wherein the source of graphene comprises graphite flakes and the process further comprises providing a graphite dispersion of graphite flakes in a graphene dispersion fluid and homogenising the graphite dispersion, preferably under high shear, thereby forming a dispersion comprising graphene.
24. A process of any one of the preceding clauses, wherein the particulate material has a particle size in the range 5 nm to 1 μm, preferably 10 nm to 500 nm, more preferably 15 nm to 250 nm.
25. A process of any one of the preceding clauses, further comprising recovering the composite, and optionally recovering the dispersion fluid, preferably for re-use.
26. A process of any one of the preceding clauses, wherein the process is conducted at a temperature in the range 0° C. to 260° C., preferably 0° C. to 110° C., more preferably 0° C. to 50° C.
27. A process for producing a photocatalytically active composite, the process comprising:

[0238] a) providing a source of graphene,

[0239] b) providing titanium dioxide in particulate form,

[0240] c) dispersing a mixture of the source of graphene and titanium dioxide in a first dispersion fluid to form a dispersion mixture, and

[0241] d) providing a source of a base in the first dispersion fluid,

thereby causing the source of graphene and titanium dioxide in the dispersion mixture to interact forming a photocatalytically active composite.
28. A photocatalytically active composite obtainable by a process of any one of the preceding clauses.
29. Apparatus to remove pollutants from fluids, the apparatus comprising a fluid inlet, a fluid conduit to supply fluid from the fluid inlet to a photocatalytically active composite of clause 27 and a fluid outlet.
30. Apparatus of clause 29, wherein the fluid comprises air or water.