SYNTHESIS OF OXYGEN AND BORON TRIHALOGENIDE FUNCTIONALIZED TWO-DIMENSIONAL LAYERED MATERIALS IN PRESSURIZED MEDIUM

Abstract

A method that uses a pressurized reactive medium composed of inert solvents such as pressurized liquid or supercritical fluid carbon dioxide (C02), and sulfur hexafluoride (SF6) and reactive dissolved species ozone (03) and/or boron trifluoride (BF3) and general boron trihalogenides (BX3) to react with two-dimensional (2D) layered materials and thereby synthesize covalently oxygen and/or BX3 functionalized exfoliated 2D layered materials. When 2D layered materials are dispersed in these reactive liquids or fluids by ultrasound sonication or high shear mixing, a simultaneous covalent functionalization and exfoliation of the 2D layered materials happens. Following attainment of the required extent of functionalization and exfoliation, the unreacted 03, BX3, SF6 and C02 can be easily removed as gases by decompression leaving behind the solid phase, thereby leading to efficient and economical production of functionalized and exfoliated 2D layered materials.

Claims

1. A method for the synthesis of covalently or charge transfer functionalized and exfoliated two-dimensional layered materials comprising: providing a two-dimensional (2D) layered material; providing an inert solvent comprising chemical species that do not participate in any reactions during the synthesis; providing a primary mixture comprising a plurality of components including at least one of the inert solvent and at least one reactive component, the at least one reactive component including at least one of ozone (O.sub.3) and boron trihalogenide, the boron trihalogenide represented by BX.sub.1X.sub.2X.sub.3, where X.sub.1, X.sub.2, and/or X.sub.3 are selected from the group consisting of fluorine, chlorine, bromine, and iodine; setting a temperature and pressure of the primary mixture, wherein the primary mixture is one of liquid and supercritical fluid at the set temperature and pressure; providing a secondary mixture comprising the two-dimensional layered material and the primary mixture, wherein the secondary mixture is configured to allow a chemical reaction between the 2D layered material and the at least one reactive component of the primary mixture; applying mechanical agitation to the secondary mixture promoting mixing of the primary mixture and dispersion and exfoliation of the 2D layered material; allowing time for the reaction to proceed based on a desired extent of functionalization and exfoliation of the 2D layered material; and isolating the functionalized and exfoliated 2D layered material from a reaction product.

2. The method of claim 1, wherein the inert solvent is at least one of carbon dioxide (CO.sub.2) and sulfur hexafluoride (SF.sub.6).

3. The method of claim 1, wherein the mechanical agitation is ultrasound sonication.

4. The method of claim 1, wherein the mechanical agitation is high shear mixing.

5. The method of claim 1, wherein the two-dimensional layered material is from a periodic table class of III-V group materials.

6. The method of claim 5, wherein the two-dimensional layered material from the class of periodic table III-V group materials is selected from the group consisting of hexagonal boron nitride (BN), boron carbon nitride (BCN), boron phosphide (BP), boron arsenide (BAs), aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), and gallium phosphide (GaP).

7. The method of claim 1, wherein the two-dimensional layered material is selected from the group consisting of a class of graphite and a class of xenes.

8. The method of claim 1, wherein the two-dimensional material is selected from the group consisting of graphene, silicene, and stanene.

9. The method of claim 1, wherein the two-dimensional layered material is from the class of transition metal dichalcogenides of a general formula TX.sub.2.

10. The method of claim 9, wherein in the general formula TX.sub.2, T selected from the group consisting of molybdenum, tungsten, scandium, titanium, hafnium, zirconium, vanadium, chromium, manganese, iron, cobalt, nickel, niobium, technetium, tantalum, rhenium, palladium, and platinum and X is selected from the group consisting of sulfur, selenium, and tellurium.

11. The method of claim 1, wherein the two-dimensional layered material is from classes of mxenes.

12. The method of claim 11, wherein the two-dimensional material from classes of mxenes is selected from the group consisting of Ti.sub.2C, (Ti.sub.0.5,Nb.sub.0.5).sub.2C, V.sub.2C, Nb.sub.2C, Mo.sub.2C, Ti.sub.3C.sub.2, Ti.sub.3CN, Zr.sub.3C.sub.2, Ti.sub.4N.sub.3, Nb.sub.4C.sub.3, Ta.sub.4C.sub.3, Mo.sub.2TiC.sub.2, Cr.sub.2TiC.sub.2, and Mo.sub.2Ti.sub.2C.sub.3.

13. The method of claim 1, wherein the two-dimensional layered material is from classes of MAX-Phases, wherein the classes of MAX-Phases includes at least one of intercalated layered and non-intercalated layered 2D ternary transition metal carbides and nitrides.

14. The method of claim 1, wherein the primary mixture comprises CO.sub.2 and O3 and the two-dimensional layered material is one of graphite and graphene.

15. The method of claim 1, wherein the primary mixture comprises CO.sub.2 and O3 and the two-dimensional layered material is hexagonal boron nitride.

16. The method of claim 14, further comprising: adding catalytic amounts of boron trihalogenide to the primary mixture.

17. The method of claim 15, further comprising: adding catalytic amounts of boron trihalogenide to the primary mixture.

18. The method of claim 1, wherein the primary mixture comprises of O.sub.3 and BX.sub.3 and the two-dimensional layered material is hexagonal boron nitride.

19. The method of claim 1, wherein: the primary mixture comprises one of boron trihalogenide and a mixture of CO.sub.2 and boron trihalogenide; and the two-dimensional layered material is a transition metal disulfide.

20. The method of claim 1, wherein the isolation of the functionalized and exfoliated 2D layered material comprises decompressing and evaporating the remainder of the primary mixture through a filter that holds the solid particle products back.

21. The method of claim 1, wherein the primary mixture comprises boron trihalogenide only and the 2D layered material is one of graphite and hexagonal boron nitride.

22. The method of claim 14, wherein the CO.sub.2 provides a long term storage medium for graphene oxide and for other oxygen functionalized carbonaceous 2D layered materials.

23. The method of claim 1, wherein the inert solvent is present in any percentage of the 0 to 100 percentage range of a total of all molecules of the primary mixture.

24. The method of claim 1, wherein the at least one reactive component is present in any percentage up to 100 percentage range of a total of all molecules of the primary mixture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The various features, advantages, and other uses of the method will become more apparent by referring to the following detailed description and drawings, wherein like reference numerals refer to like parts.

[0027] FIG. 1. depicts Fourier-Transform Infrared (FT-IR) spectra of oxygen functionalized h-BN as obtained by ozonation of h-BN in ultrasonicated liquid CO.sub.2 and that of untreated hexagonal boron nitride. The spectra were obtained from solid samples deposited on ZnSe plates from diethyl-ether slurry and dried in vacuum. It can clearly be seen that the two spectra are very similar, except the peaks in the regions of about 900-1200 cm-1 and 2800-3000 cm-1 which are signatures of covalent oxygen-functionalization of boron atoms in h-BN.

DETAILED DESCRIPTION

[0028] The present disclosure makes use of a mechanically agitated reactive medium composed of inert solvent species such as pressurized liquid or supercritical fluid carbon dioxide (CO.sub.2) or sulfur hexafluoride (SF.sub.6), and reactive species of ozone (O.sub.3) and boron trifluoride (BF.sub.3) and general boron trihalogenides BX.sub.3 to react with two-dimensional (2D) layered materials and thereby synthesize covalently oxygen and/or BF.sub.3 functionalized exfoliated 2D layered materials. The reason for coupling these four types of species together for the synthesis is based on (a) the almost identical critical temperature and pressure of O.sub.3 and BF.sub.3 and the sufficiently close critical points of SF.sub.6 and CO.sub.2, (b) the similar catalytic effect and intermolecular interactions of BX.sub.3 with 2D layered materials and ozone, and (c) the existence of liquid phases of BX.sub.3 under the typical ozonation and exfoliation temperature/pressure conditions. Various combinations of these species may be used for specific targeted syntheses. For example, some preferred combinations include O.sub.3/CO.sub.2, O.sub.3/BX.sub.3 or BX.sub.3/CO.sub.2. The BX.sub.3 may also be used by itself. When 2D layered materials are dispersed in these reactive liquids or fluids by ultrasound sonication or high shear mixing, a simultaneous covalent functionalization and exfoliation of the 2D layered materials happens. After reaching the required extent of functionalization and exfoliation, the unreacted species can easily be removed by decompressing the medium thereby leading to efficient and economic production of functionalized and exfoliated 2D layered materials.

[0029] The present disclosure utilizes the liquid and supercritical phases that can be made of inert solvents such as liquid or supercritical fluid SF.sub.6 and CO.sub.2 and reactive species O.sub.3 and general boron trihalogenides, BX.sub.3. The good mixing and solubility of these species in each other is ensured by the almost identical critical points of O.sub.3 and BF.sub.3 which allows for mixing O.sub.3 and BF.sub.3 in any ratio in the supercritical phase, as well as by the existence of liquid phases of BX.sub.3 and the solubility of ozone in them. The critical points of SF.sub.6 and CO.sub.2 are somewhat different from those of O.sub.3 and BF.sub.3, however, as described in previous works cited above, O.sub.3 dissolves in large concentrations in lqCO.sub.2 and lqSF.sub.6. Furthermore, SF.sub.6, CO.sub.2, O.sub.3 and BX.sub.3 do not react with each other, instead they form loose van der Waals complexes and adducts, as also pointed out in literature cited above. When these reactive phases are brought in contact with layered 2D materials they functionalize the surface and the edges of layers of these materials. Mechanical agitation using ultrasound sonication or high shear mixing is applied to disperse and exfoliate the 2D layered materials in these reactive media resulting in the exfoliated functionalized 2D layered materials. The exfoliated and functionalized material can be collected after the medium is decompressed and all gaseous/liquid molecules leave through a filter that holds back the solid particles.

[0030] In one implementation, the method of mechanical agitation includes the use of high shear mixing that generates shear forces on the layers of the 2D layered materials and thereby translates them relative to each other parallel with the basal planes of these materials. This results in a reduced energy need of exfoliation and a better preservation of the lateral size of exfoliated particles, while also reducing the amount of lattice defects due to ultrasound sonication. High shear mixing is especially advantageous when the liquid/fluid medium has sufficiently large viscosity. Otherwise, in an alternate implementation, the method of mechanical agitation includes ultrasound sonication that creates cavities in the medium and opens gaps between layers of 2D layered materials that will be penetrated by molecules of the medium leading to the separation of layers.

[0031] In a first embodiment, graphite or hexagonal boron nitride is immersed in a mechanically agitated liquid or supercritical mixture of CO.sub.2 with large concentration of O.sub.3 resulting in oxygen functionalized exfoliated 2D particles. Note that a large concentration of CO.sub.2, in other words, a CO.sub.2 solvent, is always recommended when graphite or graphene or other carbonaceous particles are oxygen functionalized. The high concentration of CO.sub.2 and the relatively low temperature of the reaction with O.sub.3 is important to avoid thermal decomposition of large fractions of the oxygen functionalized exfoliated carbonaceous species. BCN is another example of 2D layered carbonaceous species besides graphite that can be functionalized by this method.

[0032] In a second embodiment, a catalytic amount of BF.sub.3 is added to the mixture of CO.sub.2 and O.sub.3 to carry out the first embodiment. In this case the final product will partially be functionalized by BF.sub.3 as well.

[0033] In a third embodiment, a mixture of BF.sub.3 and O.sub.3 is used in the liquid or supercritical phase with mechanical agitation to functionalize and exfoliate h-BN and other binary III-V group materials.

[0034] In a fourth embodiment, mechanically agitated liquid or supercritical BF.sub.3 is used to BF.sub.3 functionalize and exfoliate transition metal chalcogenides.

[0035] In a fifth embodiment, xenes, mxenes and MAX-Phases are oxygen and/or BF.sub.3 functionalized using a liquid or supercritical mixture of CO.sub.2, O.sub.3 and BF.sub.3, following the above general methods.

[0036] In a sixth embodiment, graphite, h-BN, BNC and other III-V group 2D layered materials are exfoliated and functionalized in mechanically agitated liquid or supercritical BF.sub.3. Note that in some cases, such as for graphite and h-BN, only a small amount of functionalization will happen, mostly on the edges of the 2D layers, in the BF.sub.3 medium, while exfoliation may become complete to monolayers, depending on the reaction time given.

[0037] An exemplary experiment of oxygen functionalization of h-BN using O.sub.3 dissolved in lqCOz is as follows: the same apparatus has been used as in U.S. Pat. No. 8,801,939 cited above. Before the O.sub.3 addition, the BN sample (about 200 mg) has been soaked in lqCOz for about an hour at a temperature of T=10 C. and a pressure of p=800 psi (or 55 bar). Then O.sub.3 has been added at T=12 C. and p=1310 psi (or 90 bar). This was followed by ultrasound sonication for 62 minutes at pulsed ultrasound power that kept the pressure below 1500 psi (103 bar) while the temperature rose to between 35 and 36 C. Finally the system was decompressed and the solid particles collected for analysis. Fourier Transform Infrared Spectroscopy (FT-IR) indicates successful oxygen functionalization of h-BN, as shown in FIG. 1. It is to be understood that various changes in the details, materials, arrangements of parts and components and methods which have been described and illustrated herein in order to explain the nature of the synthesis of oxygen and BF.sub.3 functionalized materials that may be made by those skilled in the art within the principle and scope of the synthesis of oxygen and BF.sub.3 functionalized materials as expressed in the appended claims. Furthermore, while various features have been described with regard to particular embodiments and methods, it will be appreciated that features described for one embodiment also may be incorporated with the other described embodiments.

[0038] All publications and patent documents cited in this application are incorporated herein by reference in their entirety for all purposes to the same extent as if each individual publication or patent document were so individually denoted.

[0039] Any element in a claim that does not explicitly state means for performing a specified function, or step for performing a specific function, is not to be interpreted as a means or step clause as specified in 35 U.S.C. 112, 6. In particular, the use ofstep of in the claims herein is not intended to invoke the provisions of 35 U.S.C. 112, 6.

[0040] While the present disclosure has been described in connection with certain embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.