2-dimensional carbon material

Abstract

2-dimensional carbon thin films are described, as well as their processes of preparation, and their specific uses. The 2-dimensional carbon thin films are fabricated by preparing an organic polymeric thin film precursor, which is then subjected to a carbonisation process to remove at least some of the non-carbon atoms. Using the disclosed process, 2-dimensional carbon thin films having improved dimensional characteristics can be reliably prepared, which presents clear advantages in applications which have until now been restricted to the use of 2-dimensional carbon thin films having less useful dimensions.

Claims

1. A continuous 2-dimensional carbon thin film wherein the thin film has a thickness of less than 20 nm and an area divided by thickness ratio (A/T) of greater than 10.sup.10 nm, and wherein the thin film has an elemental composition of: 85 to 95% carbon, and 2 to 13% oxygen; or; 88 to 98% carbon, 1 to 6% oxygen, and 0.5 to 6% nitrogen.

2. The continuous 2-dimensional carbon thin film of claim 1, wherein the thin film has a thickness of less than 10 nm.

3. The continuous 2-dimensional carbon thin film of claim 1, wherein the thin film has a thickness of less than 6 nm.

4. The continuous 2-dimensional carbon thin film of claim 1, wherein at least a portion of the thin film has a structure corresponding to graphene, graphene oxide or reduced graphene oxide.

5. The continuous 2-dimensional carbon thin film of claim 1, wherein the thin film comprises 50-70 atomic % of sp.sup.2 carbon atoms.

6. The continuous 2-dimensional carbon thin film of claim 1, wherein the thin film has a light transmittance at a wavelength of 550 nm of 75% at a film thickness of 2-5 nm.

7. The continuous 2-dimensional carbon thin film of claim 1, wherein, the continuous 2-dimensional carbon thin film has a sheet resistance of 10 k/square.

8. The continuous 2-dimensional carbon thin film of claim 1, wherein the continuous 2-dimensional carbon thin film has an area greater than 0.001 cm.sup.2.

9. A process for the preparation of the continuous 2-dimensional carbon thin film of claim 1, the process comprising the steps of: a) providing an organic polymeric thin film formed by an interfacial polymerisation process, said organic polymeric thin film having a thickness of less than 100 nm; and b) subjecting the organic polymeric thin film of step a) to a carbonisation process.

10. The process of claim 9, wherein in step a), the organic polymeric thin film is formed by interfacial polymerisation on a supporting substrate.

11. The process of claim 9, wherein prior to step b), the organic polymeric thin film is separated from the supporting substrate by contacting the supported organic polymeric thin film with a solvent in which the supporting substrate is soluble and the organic polymeric thin film is insoluble.

12. The process of claim 9, wherein in step a), the organic polymeric thin film is prepared by interfacial polymerisation at the interface of two immiscible liquids.

13. The process of claim 9, wherein prior to step b), the organic polymeric thin film is placed on a carbonisation support, and wherein the carbonisation support is selected from silicon, copper, carbon fiber mat, carbon nanotube mat, alumina, or quartz.

14. The process of claim 9, wherein step b) comprises heating the organic polymeric thin film of step a) to a temperature greater than 300 C. in the absence of oxygen.

15. The process of claim 9, wherein step b) comprises heating the organic polymeric thin film of step a) to a temperature greater than 900 C. in the absence of oxygen.

16. The process of claim 9, wherein step b) comprises heating the organic polymeric thin film of step a) to a temperature greater than 1500 C. in the absence of oxygen.

17. The process of claim 9, wherein step b) comprises heating the organic polymeric thin film of step a) under vacuum.

18. The process of claim 9, wherein step b) comprises heating the organic polymeric thin film of step a) in an atmosphere comprising greater than 5 vol % hydrogen.

19. The process of claim 9, wherein the process further comprises contacting the product of carbonisation step b) with a reducing agent, and wherein the reducing agent is selected from hydrazine, chlorine, fluorine, bromine, iodine, hydrogen chloride, hydrogen bromide or hydrogen iodide.

20. The process of claim 9, wherein the organic polymeric thin film comprises one or more polymers selected from polyamides, polyurea, polypyrrolidines, polyesters, polyurethanes, polyketones, polysiloxanes, poly(amide imide), poly(ether amide) and poly(urea amide).

21. The process of claim 9, wherein the organic polymeric thin film is a polyamide.

Description

EXAMPLES

(1) Examples of the invention will now be described by reference to the accompanying figures, in which:

(2) FIG. 1 is a schematic presentation of the fabrication process of a free-standing polymer thin film via the interfacial polymerization process.

(3) FIG. 2 is an atomic force microscopic image of a polymer thin film fabricated from 0.1 wt % m-phenylenediamine and 0.005 wt % 1,3,5-benzenetricarbonyl chloride. A thickness of approximately 8.4 nm was measured.

(4) FIG. 3 shows a smooth polymer thin film fabricated from 0.1 wt % m-phenylenediamine and 0.005 wt % 1,3,5-benzenetricarbonyl chloride and transferred to a wire lasso; although the film is only ca. 8 nm thick, it forms an integral surface across the whole 1.5 cm diameter of the lasso.

(5) FIG. 4 shows a) the scanning electron microscopic images of crumpled polymer thin film on silicon wafer and b) the resulting 2-dimensional carbon thin film material after the polymer thin film was carbonised by hydrogen carbonisation (argon:hydrogen=9:1) for 1 hour at 900 C. under a hydrogen atmosphere (right). The polymer thin film was a polyamide thin film made from 3 wt % m-phenylenediamine in an aqueous phase and 0.15 wt % 1,3,5-benzenetricarbonyl chloride in a hexane phase, reacted for 1 min at the interface between the aqueous saturated nanostrand layer and the hexane phase. The resulting polyamide thin films were transferred onto silicon wafers for carbonisation.

(6) FIG. 5 shows a) the surface morphology of the 2-dimensional carbon thin film material prepared from a 0.1 wt % water solution of m-phenylenediamine and 0.005 wt % 1,3,5-benzenetricarbonyl chloride in hexane and reacted for 10 min b) the atomic force microscopic height image of 2-dimensional carbon thin film material resulting from carbonising a polyamide thin film about 8 nm thick and c) the height profile of the section of a smooth 2-dimensional carbon thin film material on silicon wafer (in FIG. 5b) showing 3 nm thickness of the 2-dimensional carbon thin film.

(7) FIG. 6 shows a Raman spectra of 2-dimensional carbon thin film material fabricated from smooth and crumpled polymer thin films which were transferred to silicon wafers and carbonised under hydrogen atmosphere (argon:hydrogen=9:1) for 1 h at 900 C. All Raman spectra were collected at 514 nm laser line excitation. The polymer thin films were fabricated by interfacial polymerisation between TMC in hexane either m-phenylenediamine (MPD) or 4-(aminomethyl) piperidine (AMP) in the aqueous phase.

(8) FIG. 7 shows a) the crumpled polyamide thin film powder prepared from interfacial polymerisation at a liquid interface in a liquid-liquid (aqueous-hexane) system followed by drying and b) the crumpled surface texture 2-dimensional carbon thin film material powder prepared by carbonising the polyamide thin film powder under a hydrogen atmosphere (argon:hydrogen=9:1) for 1 h at 900 C.

(9) FIG. 8 is the Raman spectra of crumpled 2-dimensional carbon thin film material powder, derived from polyamide thin film powder. All Raman spectra were collected at 514 nm laser line excitation.

(10) FIG. 9 shows a TEM image of crumpled 2-dimensional carbon thin film material prepared from MPD: 6 wt % and TMC: 3 wt %. Inset shows a large free-standing area on a copper grid.

(11) FIG. 10 shows a thermogravimetric spectra and the resulting derivative spectra, showing the degradation temperature (535 C.) of various polyamide thin film powders shown in Table 3 (derived from different ratios of MPD to TMC) recorded under a nitrogen environment.

(12) FIG. 11 is the ATR-FTIR spectra of several polyamide thin film powders and 2-dimensional carbon thin film material powders shown in Table 3 (derived from different ratios of MPD to TMC) showing the unique signature vibrational bands of polyamide. For carbonised samples, carbonisation was conducted under hydrogen atmosphere (argon:hydrogen=9:1) for 1 h at 900 C.

(13) FIG. 12 is a combined spectra of nitrogen adsorption and desorption for polymer thin film powders (left) and the 2-dimensional carbon thin film material powders (right) derived from the polymer thin film powders by carbonisation under hydrogen atmosphere (argon:hydrogen=9:1) for 1 h at 900 C. shown in Table 3.

(14) FIG. 13 (a) is a schematic illustrating that the nanostrand layer is saturated with an aqueous solution of diamine and contacted with a hexane layer containing trimesoyl chloride, enabling the formation of polyamide nanofilms. (b) Interfacial polymerisation at the bulk interface in a beaker.

(15) FIG. 14 shows a schematic presentation of the formation of free-standing polymer nanofilm via controlled interfacial polymerisation on a sacrificial Cd(OH).sub.2 nanostrand layer or at the interface of two immiscible bulk liquids enabling the formation of polymer nanofilms (see FIG. 13). 2D carbon nanofilm was fabricated by transferring free-standing polymer nanofilm onto a substrate (Si@SiO.sub.2, quartz, Cu, etc) followed by carbonisation at high temperature under diluted H2 atmosphere.

(16) FIG. 15(a) shows AFM surface and (b), height profile of the polyamide nanofilm (PNF.sub.MPD 0.1-22-0.005-10 m) on Si@SiO.sub.2 wafer. Polyamide nanofilm was fabricated on the nanostrand surface by reacting mphenylenediamine (MPD) and trimesoyl chloride (TMC)

(17) FIG. 16(a) AFM surface and (b), height profile of the 2D carbon nanofilm on Si@SiO.sub.2 wafer fabricated by reducing the polymer nanofilm, presented in FIG. 15(a), under diluted H.sub.2 atmosphere at 900 C. (2DC.sub.MPD 0.122-0.005-10 m900 C..sub.R1-H2+Ar-1 h).

(18) FIG. 17 shows a photograph of a 2D carbon nanofilm (2DC.sub.MPD 0.05-22-0.005-10 m1100 C..sub.R1-H2+Ar-1 h) onto a 76 mm diameter Si@SiO.sub.2 wafer. Inset shows the photograph of the 2D carbon nanofilm on quartz microscope slide and compared with a substrate covered with the polymer nanofilm.

(19) FIG. 18(a) shows an optical microscopic image of a 2D carbon nanofilm on quartz substrate (2DC.sub.MPD 0.1-22-0.1-1 m900 C..sub.R1-H2+Ar-1 h). Arrow indicates the region where the polymer layer was peeled off before carbonisation process. (b) SEM image of a carbon nanofilm (2DC.sub.MPD 0.1-22-0.1-1 m900 C..sub.R1-H2+Ar-1 h) fabricated on a copper TEM grid, showing the transparency of carbon nanofilm under electron beam. (i), (j) Optical microscope images of free-standing polymer nanofilm (2DC.sub.MPD 0.1-22-0.1-1 m) fabricated at the interface of two immiscible liquid and transferred onto a copper mesh and obtained 2D carbon nanofilm (2DC.sub.MPD 0.1-22-00.1-1 m900 C..sub.R1-H2+Ar-1 h).

(20) FIG. 19(a) shows Raman spectra of carbon nanofilms fabricated on quartz substrate showing the characteristic D, G, 2D and G peaks of nano-graphitic carbon. (b) Raman map for 1596 cm.sup.1 in the selected region (top) and the Raman spectra (bottom) for carbon nanofilm fabricated from PIP.

(21) FIG. 20 shows Raman spectra of 2D carbon nanofilms on different support. (a and b) Nanofilms were prepared on cadmium hydroxide nanostrand surface and freestanding nanofilms were transferred on different substrates. (c) Nanofilms are in powder form. (d-f) Floating nanofilms were prepared at the bulk liquid-liquid interface.

(22) FIG. 21 shows HRTEM image of a free-standing carbon nanofilm fabricated at the bulk liquid interface and transferred on Ni grid (2DC.sub.MPD 0.1-22-0.1-1 m1100 C..sub.R1-H2+Ar-1 h). An inter-planer spacing of 0.34 nm for sp.sup.2 carbons is marked on the image.

(23) FIG. 22 (a), (b) TEM and HRTEM images of crumpled carbon nanofilm (2DC.sub.MPD 6-22-3-1 m1100 C..sub.R1-H2+Ar-1 h). Polymer nanofilm was fabricated at the bulk liquid interface and collected as powder.

(24) FIG. 23 shows SEM images of polymer nanofilm (PNF.sub.MPD 6-22-3-1 m) prepared from m-phenylenediamine and derived 2D carbon nanofilms carbonised at different temperatures. (a, c, e and g) Morphology of the nanofilms on silicon wafer, (b, d, f, h) Morphology of the nanofilms on porous alumina (smartPor; 20 nm top pore diameter).

(25) FIG. 24 (a) XPS survey spectra for the nanofilms made at different carbonisationcarbonisation temperature and (b) narrow scan spectra of carbon nanofilm powder prepared from the carbonisation of polymer nanofilm powder collected by shaking the interface (2DC.sub.MPD 6-22-3-1 m1100 C..sub.R1-H2+Ar-1 h) and collected as precipitates.

(26) FIG. 25 shows X-ray photoelectron spectra of GO flakes for Sigma Aldrich-GO 763713. (a) Survey spectrum and narrow scan spectra for (b) C1s, (c) O1s and (d) N1s, respectively. Note that the N1s peak in the survey spectrum in (a) was barely detected, but a very small amount (0.3 at. wt %) was calculated from the narrow scan spectrum.

(27) FIG. 26 shows X-ray photoelectron spectra of 2D carbon nanofilm powder. Carbon nanofilm powder was prepared from the carbonisation of polymer nanofilm powder collected by shaking the interface (2DC.sub.PIP 6-22-3-1 m900 C..sub.R1-H2+Ar-1 h) and collected as precipitates.

(28) FIG. 27 shows X-ray photoelectron spectra of 2D carbon nanofilm powder. (a) Survey spectrum and narrow scan spectra for (b) O1s and (c) N1s, respectively. Carbon nanofilm powder was prepared from the carbonisation of polymer nanofilm powder collected by shaking the interface (2DC.sub.MPD 6-22-3-1 m1100 C..sub.R1-H2+Ar-1 h) and collected as precipitates.

(29) FIG. 28 shows the possible chemical structure of the membrane inferred from the XPS narrow scan analysis of C1s, O1s and N1s.

(30) FIG. 29 shows contact angle measured for the polymer nanofilms and carbonised 2D carbon nanofilms fabricated on quartz substrate. Nanofilms were carbonised at different temperature (600-1100 C.) under diluted H.sub.2 and/or pure Ar atmosphere.

(31) FIG. 30 shows optical and electrical properties of 2D carbon nanofilm as conducting electrode. (a) Optical transmittance spectra of polyamide nanofilms and 2D carbon nanofilms derived from the carbonisation of polyamide nanofilms. (b) Plot of normalized resistance measured with two-probe contact with probe distance. Square Au point contact of dimension 2 mm2 mm were sputtered deposited on the 2D carbon nanofilm (2DC.sub.MPD 0.05-22-0.05-1 m1100 C..sub.R1-H2+Ar-1 h) fabricated on quartz substrate. I-V characteristics at the inset show the Ohmic contact between 2D carbon nanofilm and Au probe/electrode. (c) Trade-off curve of transmittance vs sheet resistance for 2D carbon nanofilms measured with four-probe technique [see Table 5].

(32) FIG. 31 shows UV-vis transmittance spectra of the polymer nanofilms and 2D carbon nanofilms. Free-standing polymer nanofilm was transferred onto a quartz substrate and carbonised at 900 C. under diluted H.sub.2 and pure Ar atmosphere

(33) FIG. 32 shows UV-vis transmittance spectra of the polymer nanofilms and 2D carbon nanofilms. Free-standing polymer nanofilm was transferred onto a quartz substrate and carbonised under diluted hydrogen.

(34) FIG. 33 shows sheet resistance of carbon nanofilms fabricated on quartz substrate.

(35) FIG. 34 shows nitrogen adsorption and desorption isotherm (left) and pore size distribution calculated using 2D-NLDFT method (right) for two types of carbon nanofilm powders prepared from MPD-TMC and PIP-TMC and carbonised under Ar+H.sub.2 (9:1) flow at 900 C. for 1 h.

METHODS AND MATERIALS

(36) Chemicals and Materials

(37) Polyimide (PI) polymer (P84) was purchased from HP Polymer GmbH (Austria). All solvents used in this study were HPLC grade. Methanol, ethanol, 1-propanol, 1-butanol, acetonitrile, acetone, tetrahydrofuran (THF), ethyl methyl ketone (MEK), N,N-dimethylformamide (DMF), heptane, toluene and hexane were purchased from VWR International Ltd. Trimesoyl chloride (TMC) 98%, m-phenylenediamine (MPD) flakes99%, p-phenylenediamine (PPD)99%, piperazine (PIP) ReagentPlus 99%, 4-(Aminomethyl) piperidine (AMP) 96% and 1,6-hexanediamine (HDA) 99.5% were purchased from Sigma Aldrich, UK. MPD was purified under vacuum sublimation (110.sup.2 mbar) at 75 C. fitted with a cold water trap and used fresh each time. Cadmium chloride hydrate, Puratronic, 99.998% (metals basis) was purchased from Alfa Aesar, UK. 2-aminoethanol (98%) was received from Sigma-Aldrich, UK. Asymmetric alumina support membranes of diameter 50 mm with pore size between 18-150 nm were supplied from Smart Membrane GmBH, Germany and Synkera Technologies, Inc. USA.

(38) Characterisation Methods

(39) Carbonisation Process to Form 2D Carbon Nanofilm

(40) Pre-treatment: Purging alumina tube with Ar @ 2 L/min for 1 hr followed by the carrier gas @ 2 L/min for 1 hr (gas velocity in the sample zone is 45 cm.Math.min.sup.1)

(41) Ramp 1 (R1): Room temperature (RT) to T.sub.p C. @ 5 C./min and soak at T.sub.p for 0.4-5 hr

(42) Ramp 2 (R2): 1) RT to 125 C. @ 5 C./min and soak for 15 min

(43) 2) 125 C. to 325 C. @ 5 C./min and soak for 5 min 3) 325 C. to 425 C. @ 2 C./min and soak for 5 min 4) 425 C. to 550 C. @ 1 C./min and soak for 5 min 5) 550 C. to 600 C. @ 0.5 C./min and soak for 2 h
Ramp 3 (R3): 1) RT to 125 C. @ 5 C./min and soak for 15 min 2) 125 C. to 375 C. @ 5 C./min and soak for 5 min 3) 375 C. to 525 C. @ 1 C./min and soak for 5 min 4) 525 C. to 600 C. @ 0.5 C./min and soak for 2 h
Cooling: 1) T.sub.p C. to 700 C. @ 5 C./min (when T.sub.p>700 C.) 2) 700 C. to 300 C. @ natural cooling 3) 300 C. to RT @ natural cooling (swap carrier gas with Ar).
Scanning Electron Microscopy (SEM)

(44) Thin films were analyzed by high resolution scanning electron microscope (SEM), LEO 1525, Karl Zeiss with an accelerating voltage of 5 kV. A 5 nm thick (measured with attached QCM thickness monitor) coating of chromium was sputtered (Q150T turbo-pumped sputter coater, Quorum Technologies Ltd.) under an Ar atmosphere (2102 mbar) to achieve a minimum conductivity for reliable SEM information.

(45) Atomic Force Microscopy (AFM) Study

(46) Multimode 4 and 8 (Bruker, Calif., USA) atomic force microscope (AFM) equipped with E-type or J-type pizzo scanner was used to measure the thickness and surface roughness of the thin films. Samples were attached onto a magnetic sample disk using double sided adhesive tape. The images were captured under tapping mode or peak tapping mode using PointProbe Plus silicon-SPM probes (PPP-NCH, Nanosensors, Switzerland) with typical tip radius of less than 7 nm. Cantilever resonance frequency was in the range of 204-497 kHz with a nominal spring constant of 42 N m-1. A sampling resolution of at least 512 points per line and a speed of 0.2-1 Hz were used. Bruker NanoScope Analysis beta or Gwyddion 2.38 SPM data visualization and analysis software was used to process the AFM images. Surface roughness is presented as average roughness (Ra), root-mean-square roughness (Rrms), and peak-to-valley height (Rh), respectively. Surface morphology, roughness parameters and the thickness was estimated from the AFM scans of thin films on different substrates. To measure the thickness from AFM, free-standing thin films were transferred to silicon wafers and dried at room temperature. A scratch was made to expose the wafer surface and allow measurement of the height from the silicon wafer surface to the upper thin film surface. The thickness of the thin film was estimated from the height difference between the silicon and the thin film using a one dimensional statistical function.

(47) Polymer thin film material fabricated on silicon wafers was studied using atomic force microscopy (AFM).

(48) 2-dimensional carbon thin film material fabricated on silicon wafers was studied using atomic force microscopy (AFM).

(49) Raman Spectroscopy Study

(50) Raman measurements were carried out with a spectrometer (Renishaw RM2000 CCD) using a 514 nm laser excitation, laser power of 0.5 mW and 10 s integration time. The laser was focused onto the sample using a 50 times short working distance objective. Chemical structures of 2-dimensional carbon thin film material prepared from different monomers and with different surface morphologies on silicon wafer were studied using Raman spectra. The letters D and G, as presented in the graph of FIG. 6, stand for two characteristic Raman active modes for many carbon allotropes and the ratio D/G is a measure of the density of defects present in the 2-dimensional carbon thin films.

(51) X-Ray Photoelectron Spectroscopy (XPS)

(52) Polymer thin films were floated on an acidic water surface to render them free-standing and transferred onto a PLATYPUS gold coated silicon wafer, washed in water and dried. The survey spectra and core level XPS spectra were recorded from at least two different spots of size 400 m. Samples supported on carbon pads on stubs were introduced into the instrument via a turbo molecular pumped entry lock. The entry lock was pumped for about 15 minutes before the sample was introduced into the analysis chamber. XPS was performed in an ion pumped VG Microtech CLAM 4 MCD analyzer system. 200 Watt unmonochromated Mg X-ray excitation was used. The analyzer was operated at constant pass energy of 200 eV for wide scans and 20 eV for narrow scans setting the C1s peak at BE 285 eV to overcome any sample charging. Data was obtained using the SPECTRA version 8 operating system. Data processing was performed using CasaXps. Peak areas were measured after satellite subtraction and background subtraction either with a linear background or following the methods of Shirley. (D. A. Shirley, High-resolution X-ray photoemission spectrum of the valence bands of gold. Phys. Rev. B 5, 4709, 1972).

(53) Polymer thin film material fabricated on gold coated silicon wafers was studied using XPS.

(54) 2-dimensional carbon thin film material fabricated on silicon wafers was studied using XPS.

(55) Contact Angle Measurement

(56) Contact angle with water was measured with a standard ram-hart contact angle measurement system with DROPimage Advanced analysis software. At least three separate drops on each sample were analyzed and the average values are presented with standard deviation.

(57) UV-Vis Transmission Measurement

(58) The UV-vis transmittance of the polyamide nanofilms and the derived carbon nanofilms was measured through transmission mode with quartz as substrate. Polymer nanofilm was made either at the nanostrand interface or at the bulk liquid interface and was transferred on to a quartz substrate. Polymer nanofilm was carbonised under diluted gas environment and at different temperature conditions to form 2D carbon with different chemical composition. A high transmittance of more than 90% at 515 nm wavelength was obtained for the carbon nanofilm made from a very low concentration (0.05 wt %) MPD and TMC reacted at the bulk interface and carbonised under Ar/H.sub.2 at 900 C. for 1 h. The transmittance spectra for different polyamide nanofilms and 2D carbon nanofilms are shown in FIGS. 30-32.

(59) Sheet Resistance Measurement

(60) The sheet resistance is a measure of the resistivity per unit thickness of 2D thin film materials and is a special case of resistivity for a uniform sheet thickness. The 2D carbon nanofilm was fabricated on quartz substrate and the sheet resistance was measured with four-point-probe method. The measured sheet resistance was within few tens of K/. The best combination of transmittance and sheet resistance was 90% transmittance at 550 nm wavelength and less than 2 K/ of sheet resistance. The values of sheet resistance for different carbon nanofilms are presented in FIG. 30.

(61) Spectroscopic Ellipsometry

(62) Spectroscopic ellipsometry was carried out on a Woollam M-2000 DI (J. A. Woollam Co. Inc., NE, USA) with three incidence angles of 65, 70 and 75 to the surface normal in order to measure thickness of the thin films. Free-standing thin films were transferred to UV/ozone cleaned silicon wafers and dried under room temperature. Measurements were taken at multiple points to confirm the uniformity of the thickness of the thin films and the average values are presented. Ellipsometric data were fitted to a three-layer model using CompleteEASE data analysis software (J. A. Woollam Co. Inc., NE, USA).

(63) Polymer thin film material fabricated on silicon wafers was studied using ellipsometry.

(64) 2-dimensional carbon thin film material fabricated on silicon wafers was studied using ellipsometry.

Example 1

(65) Preparation of Polymer Thin Film on Nanostrand Layer

(66) Preparation of Free-Standing Polymer Thin Film on Silicon Wafer, Porous Support or Copper Foil

(67) A variety of sub-10 nm polyamide thin films were fabricated from differing concentrations of amine and acyl chloride on nanostrand layers formed on an ultrafiltration support membranes through controlled interfacial polymerization. A standard procedure for the polyamide thin film fabrication is detailed below.

(68) Aqueous amine solution was passed through the nanostrand layer under suction to impregnate the amine within the porous channel of the nanostrand layer. Immediately, the hexane solution of trimesoyl chloride was added on the top of the nanostrand layer to create the interface and the polymerization was allowed to continue for 1-10 min. Polyamide thin film was transferred onto a silicon wafer or copper foil by dissolving the nanostrand layer and floating the polymer thin film on a water surface.

(69) FIG. 1 depicts the schematic of the formation of polyamide thin films from different amine monomers, e.g. MPD, AMP and PIP and the transfer of the resulting polyamide thin film onto different supports.

(70) The morphology of the polyamide was controlled by varying the concentration of amine-TMC concentration. Crumpled polyamide was formed using 3 wt % MPD and 0.15 wt % TMC and the free-standing thin film was transferred onto a different substrate.

(71) Properties of polymer thin films fabricated under different interfacial reaction conditions and with both aromatic and semi-aromatic diamines are listed in Table 1.

(72) Amine concentration was found to be key in controlling surface morphology, with increasing amine concentration the thin film appears crumpled (FIG. 4a).

(73) TABLE-US-00001 TABLE 1 Composition and surface properties of free-standing polymer thin films fabricated by interfacial polymerization (IP). ND refers to data not determined. ACT refers to activated thin films, wherein the polymeric thin films were dipped in dimethylformamide for 4 h before being dipped in methanol for 15 min to wash them. Flip refers to the reverse side of the thin film. IP reaction conditions Overall TMC in thickness RMS Free-standing polymer Aqueous hexane from roughness thin films amine phase phase IP time SEM/AFM R.sub.rms (amine-wt %-IP time) [wt. %] [wt. %] (min) (nm) (nm) MPD-0.05%-10 min MPD [0.05] 0.0025 10 8.4 0.4 0.63 0.03 MPD-0.1%-1 min MPD [0.1] 0.005 1 7.5 0.4 0.52 0.04 MPD-0.1%-1 min-ACT MPD [0.1] 0.005 1 7.8 0.2 0.69 0.05 MPD-0.1%-10 min MPD [0.1] 0.005 10 8.4 0.5 0.60 0.05 MPD-0.1%-10 min-ACT MPD [0.1] 0.005 10 8.0 0.3 0.51 0.05 MPD-3%-1 min MPD [3.0] 0.15 1 94 7 78.0 1.9 MPD-3%-1 min-ACT MPD [3.0] 0.15 1 95 10 64.8 1.7 MPD-3%-1 min-Flip MPD [3.0] 0.15 1 ND 11.2 0.7 MPD-4%-1 min MPD [4.0] 0.2 1 63 5 56.2 2.8 MPD-4%-1 min-ACT MPD [4.0] 0.2 1 52 8 42.6 3.7 MPD-10%-1 min MPD [10.0] 0.5 1 64 3 23.9 3.0 MPD-10%-1 min-ACT MPD [10.0] 0.5 1 47 6 24.5 2.7 PIP-0.1%-10 min .sup.PIP [0.1] 0.02 10 33.2 1.1 4.66 0.25 PIP-0.1%-10 min-ACT .sup.PIP [0.1] 0.02 10 ND ND AMP-0.1%-10 min AMP [0.1] 0.02 10 14.5 0.5 2.31 0.88 AMP-0.1%-10 min-ACT AMP [0.1] 0.02 10 ND ND

(74) Table 1 shows that the thickness of the smooth polyamer thin films fabricated from MPD was approximately constant after 1 min, whereas their mass measured with a quartz crystal microbalance (QCM) increased three-fold with prolonged reaction time (1-10 min).

(75) TABLE-US-00002 TABLE 2 Further composition and surface properties of free-standing polymer thin films fabricated by interfacial polymerization (IP). ND refers to data not determined. ACT refers to activated thin films, wherein the polymeric thin films were dipped in dimethylformamide for 4 h before being dipped in methanol for 15 min to wash them. Flip refers to the reverse side of the thin film. Degree of network cross-linking is calculated as, $\left[\mathrm{DNC}=\frac{X}{X+Y}100\%\right]$where $\left[\frac{O}{N}=\frac{3X+4Y}{3X+2Y}\right].$ Free-standing Degree of network polymer thin films Atomic composition from XPS (%) crosslinking Contact (amine-wt %-IP time) C O N COOH (DNC) (%) angle () MPD-0.05%-10 min ND ND ND ND ND 58.2 1.6 MPD-0.1%-1 min 73.3 14.3 12.4 3.0 78.6 56.8 3.2 MPD-0.1%-1 min-ACT 73.5 14.5 12.0 2.9 71.7 56.6 2.4 MPD-0.1%-10 min 73.7 14.3 12.0 3.7 73.8 58.7 1.5 MPD-0.1%-10 min-ACT 74.0 14.6 11.4 3.3 63.1 59.1 1.9 MPD-3%-1 min 73.6 13.8 12.6 3.2 86.4 51.2 1.9 MPD-3%-1 min-ACT 73.0 14.7 12.3 3.2 73.3 49.3 2.4 MPD-3%-1 min-Flip 72.5 14.7 12.8 3.2 79.3 ND MPD-4%-1 min 73.3 14.7 12.0 3.4 69.7 53.6 2.9 MPD-4%-1 min-ACT 73.2 14.5 12.3 3.4 75.4 53.1 1.8 MPD-10%-1 min 74.5 12.8 12.7 1.8 98.8 60.6 4.0 MPD-10%-1 min-ACT 74.7 12.9 12.4 2.2 94.1 57.6 2.4 PIP-0.1%-10 min 73.2 14.2 12.6 2.0 82.1 44.1 1.1 PIP-0.1%-10 min-ACT 72.7 14.6 12.7 2.1 79.1 41.9 1.5 AMP-0.1%-10 min 75.5 13.1 11.4 1.7 79.2 55.7 1.4 AMP-0.1%-10 min-ACT 75.0 13.2 11.5 1.6 79.3 56.2 1.7

(76) Table 2 shows the carbon, oxygen and nitrogen content in the thin films estimated by X-ray photoelectron spectroscopy (XPS). The extent of chemical cross-linking (DNC) was calculated from the relative values of N and O measured from XPS.

(77) The thicknesses for smooth thin films fabricated from MPD were estimated by Ar sputtering in XPS and spectroscopic ellipsometry, confirming a sub-10 nm thickness.

(78) The contact angles for all polyamide thin films were in the range 50-60, which suggests similar polarity (surface energy) of the surfaces of all the thin films formed.

(79) Atomic Force Microscopy (AFM) Study

(80) To measure the thickness from AFM, free-standing thin films were transferred to silicon wafers and dried at room temperature. A scratch was made to expose the wafer surface and allow measurement of the height from the silicon wafer surface to the upper thin film surface. The thickness of the thin film was estimated from the height difference between the silicon and the thin film using a one dimensional statistical function.

(81) FIG. 2 shows the AFM image measured for the polyamide thin film fabricated from 0.1 wt % MPD and 0.005 wt % TMC and reacted for 10 min. A thickness of approximately 8.4 nm was measured.

(82) FIG. 3 shows a smooth polymer thin film (fabricated from 0.1 wt % MPD and 0.005 wt % TMC and reacted for 10 min) transferred to a wire lasso; although the thin film is only ca. 8 nm thick, it forms an integral surface across the whole 1.5 cm diameter of the lasso.

(83) Scanning Electron Microscopy (SEM) Study

(84) A crumpled structure of polymer thin films was observed when prepared from high concentration MPD-TMC (MPD: 3 wt % and TMC: 0.15 wt %, reacted for 1 min). The SEM image of free-standing crumpled polyamide thin film transferred onto a silicon wafer is shown in FIG. 4a.

(85) Carbonisation of Polyamide Thin Film

(86) Polyamide thin film on silicon wafer was converted to 2-dimensional carbon thin film material via high temperature carbonisation under hydrogen (argon:hydrogen=9:1) for 1 h at 900 C. Polyamide thin films were placed inside a ceramic crucible in an electrical furnace and the temperature was increased at 5 C. per min under the said gas atmosphere. After the carbonisation process, the furnace was allowed to cool down to room temperature under nitrogen atmosphere.

(87) Atomic Force Microscopy (AFM) Study

(88) 2-Dimensional carbon thin film material fabricated on silicon wafers was studied using atomic force microscopy (AFM). For a 2-dimensional carbon thin film material prepared from polyamide thin film (MPD: 0.1 wt % and TMC: 0.005 wt %, reacted for 10 min) the surface morphology and cross-sectional image with height profile is shown in FIG. 5. Very smooth surface of the 2-dimensional carbon thin film material with sub-nm rms roughness and a thickness of about 3 nm was measured with AFM.

(89) FIG. 5 shows a) the surface morphology of the 2-dimensional carbon thin film material prepared from a 0.1 wt % water solution of m-phenylenediamine (MPD) and 0.005 wt % trimesoyl chloride (TMC) in hexane and reacted for 10 min, b) the height profile of a section of a smooth 2-dimensional carbon thin film material on silicon wafer, and c) the atomic force microscopic image of 2-dimensional carbon thin film material resulting from carbonising a polyamide thin film about 8 nm thick.

(90) The measured thicknesses of the carbon thin film material were in the range of 1-3 nm. The average area of the flakes of carbon thin film material was bigger than 20,000,00020,000,000 nm.sup.2.

(91) Scanning Electron Microscopy (SEM) Study

(92) The 2-dimensional carbon thin film material generated after carbonisation of the crumpled polyamide thin film (MPD: 3 wt % and TMC: 0.15 wt %, reacted for 1 min) at 900 C. for 1 h is also shown in FIG. 4b. Interestingly, the surface features of the polyamide was almost retained after carbonisation, although the features were flattened.

(93) Raman Spectroscopy Study

(94) Raman measurements were carried out with a spectrometer (Renishaw RM2000 CCD) using a 514 nm laser excitation, laser power of 0.5 mW and 10 s integration time. The laser was focused onto the sample using a 50 times short working distance objective. Chemical structures of 2-dimensional carbon thin film material prepared from different monomers and with different surface morphologies on silicon wafer were studied using Raman spectra. The letters D and G, as presented in the graph of FIG. 6, stand for two characteristic Raman active modes for many carbon allotropes and the ratio D/G is a measure of the density of defects present in the 2-dimensional carbon thin films. The structure observed from the Raman spectra confirms the graphitisation of the carbon structure when carbonised at high temperature under hydrogen.

Example 2

(95) Preparation of Polymer Thin Film at the Interface of Two Immiscible Liquids

(96) Transfer of the Polymer Thin Film on Silicon Wafer and Copper Foil

(97) Polyamide thin film was prepared in a beaker by carefully pouring TMC-hexane solution on the surface of aqueous MPD solution. A relatively flat thin film of thickness about 15 nm with local protuberance structures was formed when reacting with 3 wt % MPD and 0.15 wt % TMC at room temperature. The polymer thin film was then picked up on a silicon wafer or on copper foil.

(98) Carbonisation of Polyamide Thin Film

(99) Polymer thin films on silicon wafer or copper foil were converted to 2-dimensional carbon thin film material via high temperature carbonisation under hydrogen (argon:hydrogen=9:1) for 1 h at 900 C. Polymer thin films were placed inside a ceramic crucible in an electrical furnace and the temperature was increased at 5 C. per min under the said gas atmosphere. After the carbonisation process, the furnace was allowed to cool down to room temperature under nitrogen atmosphere.

Example 3

(100) Production of Polyamide Thin Film Powder at the Interface of Two Immiscible Liquids

(101) The polymer thin film powder was prepared by slowly adding TMC-hexane solution on top of the aqueous MPD solution and rigorously shaking the solution for at least 1 min. The vigorous shaking promoted formation of a large amount of polymer thin film swollen in the solvent. The excess MPD was removed by washing the polymer in water several times. Excess TMC was then removed by washing with excess amount of acetone several times. Highly swelled polymer thin film was then dried either by freeze-drying or in a vacuum oven at 50 C. overnight after hand squeezing the swelled polymer. The photograph of a petri-dish containing polymer thin film powder is shown in FIG. 7. Table 3 represents a list of polyamide thin film powders prepared at liquid interfaces under different experimental conditions. The temperature of the MPD solution was increased to increase the rate of reaction at the interface and to form different crumpling of the thin film.

(102) TABLE-US-00003 TABLE 3 Preparation condition of thin films at the interface Polymerization condition Polymer thin film as Aqueous amine powder and derived MPD Temperature TMC carbon powder (wt %) ( C.) (wt %) BL-PA-01-Carbon 6.0 22 0.6 BL-PA-02-Carbon 22 3.0 BL-PA-03-Carbon 50 BL-PA-04 22 6.0 BL-PA-05 50 BL-PA-06 22 3.0 BL-PA-07 50 BL-PA-08 22 0.6 BL-PA-09 50
Conversion of Polymer Thin Film Powder to 2-Dimensional Carbon Thin Film Powder Under High Temperature Carbonisation

(103) Polymer thin film powder was converted to 2-dimensional carbon thin film residue powder via high temperature carbonisation under hydrogen (argon:hydrogen=9:1) for 1 h at 900 C. Polymer thin film powder was placed inside a ceramic crucible in an electrical furnace and the temperature was increased at 5 C. per min under the said gas atmosphere. After the carbonisation process, the furnace was allowed to cool down to room temperature under nitrogen atmosphere. The photograph of a petri-dish containing 2-dimensional carbon thin film material powder is shown in FIG. 7.

(104) The Raman spectra of the crumpled 2-dimensional carbon thin film material prepared from the carbonisation of the crumpled polyamide (MPD: 6 wt % and TMC: 3 wt %, reacted for 1 min) thin film powder formed at the interface is shown in FIG. 8. The temperature of MPD solution doesn't make a significant difference to the Raman result and confirms the identical chemical structure of 2-dimensional carbon thin film materials.

(105) Transmission Electron Microscopy (TEM)

(106) Transmission electron microscopy (TEM) was carried out using JEOL JEM-2010 or JEM-2000 FX II operated at 200 kV. Gatan ES500W Erlangshen (model 782) and MultiScan MSC 600HP (Model 794) CCD cameras were used for wide range TEM and high resolution TEM (HRTEM) imaging, respectively. A piece of the free-standing polymer thin film was transferred to a copper grid and dried at room temperature and employed for TEM characterization.

(107) The TEM image of the crumpled 2-dimensional carbon thin film material produced at the interface (MPD: 6 wt % and TMC: 3 wt %) is shown in FIG. 9. The inset shows the large area of the crumpled 2-dimensional carbon on the copper mesh.

(108) Thermogravimetric (TGA) Study of Polymer Thin Film Powder

(109) TGA was carried out at a heating rate of 10 C. per minute under nitrogen atmosphere between 30 to 950 C. using TGA Q500 (TA Instruments). Typical TGA curve of the polyamide thin film powder prepared at the interface is shown in FIG. 10. The derivative spectra indicates the water loss from the polymer powder at 75 C. and a decomposition peak at 535 C. The peak 395 C. could be due to the decomposition of excess MPD or TMC remained within the samples.

(110) ATR-FTIR Study of Polyamide Thin Film Powder

(111) The ATR-FTIR spectra were recorded on a PerkinElmer Spectrum 100 spectrometer equipped with a Universal ATR sampling accessory (diamond crystal). The collective scans (typically 10) were recorded for each sample in the spectral range of 4000-400 cm.sup.1. To improve the signal-to-noise ratios, spectra were recorded with an incident laser power of 1 mW and a resolution of 0.5 cm.sup.1.

(112) FTIR spectra are presented in FIG. 11. Typical absorption peaks corresponding to polyamide is clearly evident from the spectra. All spectra correspond to different thin films prepared under different interfacial reaction conditions (see Table 1) shows identical absorption peak position, confirmed the identical chemical structure of all polyamide formed at the interface.

(113) Gas Adsorption Study of Polymer Thin Film Powder and 2-Dimensional Carbon Thin Film Material Powder

(114) Nitrogen adsorption and desorption spectra was recorded with Micromeritics using TriStar 3000 V6.07 A software. Samples were dried at 50 C. under nitrogen for at least 4 h before the measurement. Specific surface area, S.sub.BET, was determined by BET analysis of N.sub.2 adsorption isotherm at 77 K. Microporous area and volume were measured from the t-plot. Average pore diameter, D.sub.A and D.sub.D, were determined by BJH analysis of N.sub.2 adsorption and desorption isotherms, respectively. V.sub.meso and V.sub.macro are cumulative pore volumes in the radius ranges of 1-300 nm, respectively.

(115) FIG. 12 shows the combined spectra of nitrogen adsorption and desorption for polymer thin film powder (left) and the 2-dimensional carbon thin film material powder (right) derived from the polymer thin film powder by carbonisation under hydrogen atmosphere (argon:hydrogen=9:1) for 1 h at 900 C.

(116) Table 4 presents the gas adsorption properties of polyamide thin film powders formed at the liquid interface and derived 2-dimensional carbon thin film material powders carbonised at 900 C. for 1 h under argon/hydrogen atmosphere. From Table 4 it is evident that the polymer thin film powders have very small microporous volume and whereas the 2-dimensional carbon thin film material powders showed a significant microporous surface area with a BET surface area exceeding 500 m.sup.2g.sup.1.

(117) TABLE-US-00004 TABLE 4 shows the gas adsorption properties of polyamide thin film powders formed at the liquid interface and derived 2-dimensional carbon thin film material powders carbonised at 900 C. for 1 h under argon/hydrogen atmosphere. Thin film Polymerization powder and condition derived Aqueous amine Micropore carbon thin MPD Temp TMC S.sub.BET area D.sub.A D.sub.D V.sub.micro V.sub.meso+Macro film powder (wt %) ( C.) (wt %) (m.sup.2 g.sup.1) (m.sup.2 g.sup.1) (nm) (nm) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) BL-PA-01- 6.0 22 0.6 498.9 402.1 11.6 9.2 0.18 0.22 Carbon BL-PA-02- 22 3.0 508.3 406.9 9.4 6.8 0.18 0.20 Carbon BL-PA-03- 50 486.0 393.9 10.5 7.7 0.18 0.20 Carbon BL-PA-04 22 6.0 5.0 0.7 29.5 20.7 0.00 0.03 BL-PA-05 50 13.8 1.3 19.1 18.2 0.00 0.06 BL-PA-06 22 3.0 19.6 1.5 18.5 16.7 0.00 0.08 BL-PA-07 50 24.9 0.8 17.3 15.5 0.00 0.10 BL-PA-08 22 0.6 30.0 0.9 18.5 16.4 0.00 0.14 BL-PA-09 50 24.0 0.8 18.7 16.6 0.00 0.11

Example 4

(118) Further Studies

(119) Highly cross-linked polymer (polyamide) nanofilms were fabricated via interfacial polymerization of a diamine, and an acyl chloride at the interface of a biphasic aqueous-organic mixture. In some cases a sacrificial nanostrand layer was formed on a cross-linked polyimide ultrafiltration support membrane (see FIG. 13) via vacuum filtration of a nanostrand solution.sup.4,5 and then used as a substrate for fabrication of nanofilms with controlled morphology through controlled release of diamine at the water-hexane interface.sup.5. FIG. 14 shows the schematic of the process for fabricating ultrathin and free-standing polymer nanofilms made via both nanostrand assisted interfacial polymerisation and the conventional interfacial polymerisation at the bulk liquid interface. m-Phenylenediamine (MPD) in an aqueous phase was reacted with trimesoyl chloride (TMC) in a hexane phase. The resulting freestanding polymer nanofilm was then transferred onto quartz, metal or Si@SiO.sub.2 wafers (Si wafer with native 2.3 nm oxide layer on surface) and carbonised under an argon-hydrogen environment (Ar:H.sub.2=9:1) at 600-1100 C. for 1 h.

(120) The thickness of the initial polymer nanofilm and the resultant carbonised 2D carbon nanofilm on Si@SiO.sub.2 wafer was determined using atomic force microscopy (AFM). A scratch was made to expose the wafer surface and allow measurement of the height from the silicon wafer surface to the upper nanofilm surface. FIGS. 15a and b show the AFM image and the 1 D statistical analysis from the image to calculate the height difference from the silicon wafer substrate to the polyamide nanofilm surface and hence the thickness of the film. The measured thickness of the smooth polyamide nanofilm was about 8 nm. After carbonisation, an extra-large, defect-free and smooth 2D carbon nanofilm of thickness 2 nm was achieved (FIGS. 16a and b).

(121) FIG. 17 shows a picture of a single sheet of defect-free 2D carbon nanofilm on Si@SiO.sub.2 wafer (2.3 nm oxide layer) with an area of around 45 cm.sup.2, fabricated from the carbonisation of polyamide nanofilm formed at the bulk liquid interface from 0.05 wt % MPD in water and 0.05 wt % TMC in hexane (2DC.sub.MPD 0.05-22-0.05-1 m1100 C..sub.R1-H2+Ar-1 h) (in the aforementioned notation, which is adopted throughout this example, 2DC denotes a 2D carbon film; .sub.MPD denote metaphenylene diamine; .sub.0.05 denotes the wt % of amine-containing reagent used in the interfacial polymerisation step; .sub.22 denotes the temperature of the interfacial polymerisation step; .sub.0.05 denotes the wt % of the carboxy-containing reagent used in the interfacial polymerisation step; .sub.1 m denotes a 1-minute duration of the interfacial polymerisation step; 1100 C. denotes the final temperature at which the carbonisation step was performed; .sub.R1 denotes that Ramp 1, defined herein, was used; .sub.H2+Ar denotes that an atmosphere of H.sub.2 and Ar was used in the carbonisation step; and .sub.1 h denotes a 1 hour soak time for the carbonisation step). Variations in the film thickness and the color contrast in the optical images was not observed, as the light interference on the thin SiO.sub.2 layer was not strong enough and was not modulated by the carbon layers..sup.6,7 Transparency and the thinness of this carbon nanofilm on microscopic quartz substrate are compared with the polymer nanofilm and illustrated in the inset picture. FIG. 18a shows the optical microscope image of the 2D carbon nanofilm which is the part of a continuous sheet of few cm.sup.2 in dimension. The arrow indicates the edge of a tear made in the polymer nanofilm before the carbonisation. It was deduced that the formation of 2D carbon nanofilm by carbonisation does not depend on the property of the support. 2D carbon nanofilms formed on different supports were found to have identical chemical structure.

(122) Carbonisation temperature, temperature ramp, soak time, and gas composition were widely varied to understand their effect on the 2D carbon formation process. In some cases, carbonisation temperature was limited by the temperature stability of the selected support. When using copper as a support for the polymer nanofilm, no catalytic activity of copper was noticed when carbonised under conditions identical to those adopted for CVD graphene fabrication. FIG. 18b shows the SEM image of the edge of a 2D carbon nanofilm fabricated on a copper TEM grid (2DC.sub.MPD 0.1-22-0.1-1 m900 C..sub.R1-H2+Ar-1 h). Polyamide nanofilms were formed at the bulk liquid interface from 0.1 wt % MPD in water and 0.1 wt % TMC in hexane and transferred onto the TEM grid. It was surprising to note that the freestanding polyamide nanofilms on the square hole area (25 m.sup.2) of the TEM grid was converted to the freestanding carbon nanofilm during the carbonisation process without disintegration. This indicates that the mechanical integrity of the polymer nanofilm was preserved during the carbonisation process to 2D carbon nanofilm. FIGS. 18c and d represent the optical microscope image of the polyamide nanofilm and the carbonised 2D carbon nanofilm on a copper grid. The sections were captured with partially uncovered areas on the grid to highlight the nanofilms by contrast. Insets in the figures show the SEM image of the nanofilms covering a single square hole.

(123) It was deduced that the chemical and structural properties of the 2D carbon nanofilms are in the same range as the properties of graphene. The Raman spectra presented in FIG. 19a displays a nano-graphitic-type carbon.sup.8 and resembles the spectra of graphene and reduced graphene oxide materials..sup.9-12 The existence of a mixture of graphitic peak or G peak and a disordered peak or D peak indicate the amorphous content of the 2D carbon nanofilms arising from the edge defects, dangling bonds, and related features. The observed intensity ratio (I.sub.D/I.sub.G) from FIG. 19a and FIG. 20, which is also inversely proportional to the fourth power of E.sub.laser, is about 0.87 to 0.90 for our 2D carbon nanofilms. Such behaviour is common for polycrystalline graphene related materials and the calculated crystallite size is about 18-20 nm which is in agreement with the low temperature treated diamond-like carbon.sup.9 and larger than the other polymer derived carbon films..sup.3 The Raman mapping for the 1596 cm.sup.1 peak and a snapshot of the Raman spectrum is shown in FIG. 19b.

(124) Mapping was carried out on a folded region of a 2D carbon nanofilm which resembles the folded nature of the nanofilm under an optical microscope. As expected from the calculated crystallite size, the nanofilms are polycrystalline in nature and a partial graphitization was noticed in the high resolution transmission electron microscope (HRTEM) as shown in FIG. 21. An inter-planer spacing of 0.34 nm corresponds to the graphitic structure present within the carbon nanofilm carbonised under H.sub.2/Ar at 1100 C. for 1 h on a nickel TEM grid. The manipulation of the surface morphology of the polyamide nanofilms was achieved by controlling the conditions for interfacial polymerization, moving from smooth to crumpled with increasing concentration of MPD and TMC at the interface. SEM images of crumpled polyamide nanofilms fabricated using nanostrand assisted interfacial polymerisation and transferred onto a silicon wafer (PNF.sub.MPD 3-22-0.15-1 m) and the corresponding carbonised 2D carbon nanofilm (2DC.sub.MPD 3-22-0.15-1 m900 C..sub.R1-H2+Ar-1 h) are presented in FIGS. 22a and b. The crumpled surface morphology of the polymer nanofilm was retained in the 2D carbon nanofilm after the carbonisation process (also see FIG. 23). TEM and HRTEM images of crumpled carbon nanofilm (2DC.sub.MPD 3-22-0.15-1 m1100 C..sub.R1-H2+Ar-1 h) are shown in FIG. 22c and again short range crystallinity was observed from the HRTEM image.

(125) To understand the chemical nature of these carbon nanofilms, XPS study was conducted using a nanofilm powder made via interfacial polymerization carried out while shaking the biphasic liquid system, and collected as a polymer precipitate. An identical carbonisation process was followed to obtain 2D carbon nanofilm powders. XPS survey spectra and narrow scan C1s spectra of 2D carbon nanofilms (2DC.sub.MPD 6-22-3-1 m600-1100 C..sub.R1-H2+Ar-1 h) are shown in FIGS. 24-27 and Table 5 below.

(126) TABLE-US-00005 TABLE 5 XPS results from polyamide nanofilms. Binding energies and plausible species were determined from the deconvolution of C1s, O1s and N1s core level XPS spectra. Energy position was calibrated after charge correction - C1s: 284.7 eV, O1s: 532.8 eV and N1s: 401.2 eV. C1s O1s N1s Nano BE Atomic BE Atomic BE Atomic films (eV) Species (%) (eV) Species (%) (eV) Species (%) @ 900 C. Carbon 92.5 0.6 Oxygen 2.8 0.2 Nitrogen 4.7 0.8 284.6 CC (sp.sup.2) aromatic 58.5 531.0 Carbonyl 18.6 398.2 Pyridinic 17.9 285.2 CC (sp.sup.3) aliphatic 6.0 532.5 Carbonyl (ester, amide & 400.2 Pyrrolic 16.2 286.1 Phenol, alcohol, ether 12.3 anhydride) hydroxyl, ether 48.8 401.2 Quaternary 45.3 287.3 Carbonyl, quinine 10.0 533.5 Ether in ester & anhydride 26.9 402.8 Protonated 289.1 Carboxyl, lactone, ester 4.5 534.2 Carboxyl n/a pyridine/pyrrole 20.6 290.6 Carbonate, COO 2.0 536.1 H.sub.2O 5.7 291.6 Plasmon 6.7 @ 1100 C. Carbon 96.4 0.3 Oxygen 2.0 0.2 Nitrogen 1.6 0.1 284.6 CC (sp.sup.2) aromatic 62.9 531.0 Carbonyl 14.7 398.2 Pyridinic 6.4 285.2 CC (sp.sup.3) aliphatic n/a 532.5 Carbonyl (ester, amide & 400.2 Pyrrolic 5.5 286.1 Phenol, alcohol, ether 13.5 anhydride) hydroxyl, ether 53.0 401.2 Quaternary 52.9 287.3 Carbonyl, quinine 7.7 533.5 Ether in ester & anhydride 23.7 402.8 Protonated 289.1 Carboxyl, lactone, ester 4.7 534.2 Carboxyl n/a pyridine/pyrrole 35.2 290.6 Carbonate, COO 1.7 536.1 H.sub.2O 8.5 291.6 Plasmon 9.6

(127) The binding energies of carbon atoms differ depending on how they are linked with other atoms. Deconvolution of the C1 s spectra gives at seven individual component groups that represent graphitic carbon (284.6 eV), and carbon present in phenol, alcohol or ether (286.10.3 eV), carbonyl or quinine groups (287.30.3 eV), carboxyl, lactone, or ester groups (289.1 eV) and carbonate groups (290.6 eV). The detailed distribution of these functional groups in GO and carbonised samples is listed in Table 5.

(128) The O1s and N1s narrow scan XPS spectrum were deconvoluted for different energy corresponding to different species as shown in Table 5.

(129) The carbon content, in terms of the total atomic composition calculated from XPS survey spectra, is increased and nitrogen and oxygen content was decreased after carbonisation at high temperature. The carbon content in the starting polymer will determine the overall carbon yield (Table 6 below). As shown in FIG. 24b, the deconvolution of narrow scan C1s spectra reveals the existence of different carbon species (Table 5).sup.1,13,14 The detailed analysis of C1s, N1s and O1s narrow scan is presented in Table 5 and a possible chemical structure of the carbon nanofilm is inferred from this data as shown in FIG. 28, with possible nitrogen and oxygen species bonded to the carbon backbone. Due to the existence of the remaining polar oxygen and nitrogen species, the surface of the carbon nanofilm remains relatively hydrophilic when carbonised at lower temperature (FIG. 29).

(130) TABLE-US-00006 TABLE 6 Mass percentage calculation from the probable chemical structure of the nanofilms. Unit Atomic (%) Weight (%) Nanofilm and the nature of cross-linking Chemical weight C O N C O N H (see reference xx) formula (g Mol.sup.1) (%) (%) (%) (%) (%) (%) (%) MPD + TMC Fully cross-linked (Y = 0) C.sub.18H.sub.12O.sub.3N.sub.3 318 75.0 12.5 12.5 67.9 15.1 13.2 3.8 Fully linear (X = 0) C.sub.15H.sub.10O.sub.4N.sub.2 282 71.4 19.1 9.5 63.8 22.7 9.9 3.5 PIP + TMC Fully cross-linked (Y = 0) C.sub.15H.sub.15O.sub.3N.sub.3 285 71.4 14.3 14.3 63.2 16.8 14.7 5.3 Fully linear (X = 0) C.sub.13H.sub.12O.sub.4N.sub.2 260 68.4 21.0 10.5 60.0 24.6 10.8 4.6 AMP + TMC Fully cross-linked (Y = 0) C.sub.18H.sub.21O.sub.3N.sub.3 327 75.0 12.5 12.5 66.1 14.7 12.8 6.4 Fully linear (X = 0) C.sub.15H.sub.16O.sub.4N.sub.2 288 71.4 19.1 9.5 62.5 22.2 9.7 5.6 Hydrogen content within the nanofilms was not taken into consideration for the calculation of atomic percentage to compare with XPS and EDX results.

(131) The UV-vis transmittance spectra of polymer nanofilms transferred onto quartz substrates and the resultant 2D carbon nanofilms are shown in FIG. 30a. Polymer nanofilms showed higher transmittance compared to the carbon nanofilms because of the lower free-electron density in the polymer nanofilms; this also renders them electrically non-conducting. A transmittance of 90% was observed for the 2D carbon nanofilm fabricated from 0.02% MPD and 0.02% TMC reacted for 1 min and carbonised under H.sub.2/Ar environment at 1100 C. for 1 h, resulting in a 3 nm thickness (2DC.sub.MPD 0.02-22-0.02-1 m1100 C..sub.R1-H2+Ar-1 h). Decreased transmittance was observed with increased thickness and roughness of the carbon nanofilms (FIGS. 31 and 32) with increased conductivity. A trade-off relationship of transmittance with the sheet resistance is displayed in FIG. 30c, which clearly demonstrates the 2D carbon nanofilms are a potential candidate for transparent and conducting electrode materials. In some cases the combination of transparency and sheet resistance is much lower than the reduced graphene oxide and very close to the CVD graphene. At the same time the sheet sizes of the 2D carbon nanofilms are much larger than any other 2D materials including those of the graphene related materials.

(132) The measured sheet resistance using two-probe gold contact, where the maximum probe spacing of gold electrode was 46 mm, showed an equivalent values to those measured with the conventional four-probe method (FIG. 30b). The measured sheet resistance of 800/ was unchanged up to a probe spacing of 20 mm below which it increased rapidly as the contact resistance in series with the carbon nanofilm becomes dominant. The linear I-V characteristics presented in the inset of FIG. 30b confirm the Ohmic contact between the gold electrode and the carbon nanofilm across a wide range of applied voltage of up to 30 V. This sheet resistance value is identical with the reported value for a 3-nm-thick transferred CVD graphene film..sup.2

(133) Table 7 below provides a comparison of the properties of graphene, reduced graphene oxide and the 2D carbon nanofilms of the invention.

(134) TABLE-US-00007 TABLE 7 Comparison for the sheet resistance and transparency of 2D carbon nanofilms at 550 nm with graphene and reduced graphene oxide films Sheet resistance Process T (%) (/square) Reference Graphene (simulated) Theoretical calculated values were taken from the 72-98 5.2-62.4 Nat. Nanotechnol. 5, 574, 2010 reference Mechanical exfoliation of graphene Micromechanical cleavage 90 5000 Nano Lett. 8, 1704, 2008 CVD graphene film CVD graphene film on Ni films 76-84 278-665 Nature 457, 706, 2009 CVD graphene film on polycrystalline Ni films 90 700 Nano Lett. 9, 30, 2009 Large-area graphene grown on Cu foils by CVD and 90-97 300-2100 Nano Lett. 9, 4359, 2009 transfer CVD graphene film on Ni films and transfer 72-91 210-1350 Appl. Phys. Lett. 95, 063302, 2009 Layer by layer stacking of large area CVD graphene 90-97 40-270 Nat. Nanotechnol. 5, 574, 2010 Solution processed graphene Surfactant-stabilized, oxide-free graphene dispersions 34-92 6150-43500000 Small 6, 458, 2009 Liquid-liquid assembly of graphene platelets 70 100 Nano Lett. 9, 167, 2009 LB film of exfoliated graphene 82-93 7200-150000* Nat. Nanotech. 3, 538, 2008 Solution-processed graphene transparent electrodes 55-92.5 200-6860 ACS Nano, 4, 43, 2010 Graphene oxide (GO) and reduced GO (rGO) Vacuum filtration and reduced with hydrazine and 63-98.8 27275-494763000 Nat. Nanotech. 3, 270, 2008 annealed at 200 C. under nitrogen Spin coated reduced graphene oxide films and treated 2-97 55-906890 ACS Nano 2, 463, 2008 at 1100 C. Dip-coated GO film and thermal annealed at 1100 C. 63 1800 Nano Lett. 8, 323, 2008 under Ar/H.sub.2 Spin assisted self-assembly of reduced graphene 87-95 11300-31700 Appl. Phys. Lett. 95, 103104, 2009 oxide LB assembly of graphite oxide single layer followed by 95 19000000 J. Am. Chem. Soc. 131, 1043, 2009 reduction LB film of ultralarge graphene 54-96 275-350000 ACS Nano, 5, 6039, 2011 GO film reduced with HI at 100 C. 71-87 840-20500 ACS Nano 4, 5245, 2010 GO film via in situ reduction with NaNH.sub.3 solution 80 350 Nat. Commun. 4, 1539, 2013 GO films reduced for 1 h at 100 C. in 55% HI 85 1600 Carbon 48, 4466, 2010 Layer-by-layer assembly of oppositely charged 75-94 2500-6900000 J. Mater. Chem. 21, 3438, 2011 reduced graphene oxides and annealed under hydrogen atmosphere Solution processed rGO for large-area fabrication via 64-92 1540-18850 Adv. Mater. 24, 2874, 2012 rod coating Spray coating from GO/hydrazine solution on 70-90 600-8230 Carbon, 48, 1945, 2010 preheated support Spray coating of chemically modified graphene 96 20000000 Nat. Nanotechnol. 3, 101, 2008 suspension Graphene from solid carbon source Growth of graphene from PMMA, sucrose and 97 1200 Nature 468, 550, 2010 fluorene Carbon nanosheet derived from polymers Pyrolysis of spin-coated PIM-1 polymer at 1200 C. 50-88.5 1500-12000 Nanoscale 6, 678, 2014 Spin-coating of polyacrylonitrile followed by 33-99 100-320000000 Appl. Phys. Lett. 102, 043304, 2013 carbonization Spin-coating of pitch followed by carbonization 52-89 1500-14500 Solar Energy Materials & Solar Cells 115, 1, 2013 Heat-treatment of spin-coated polyacrylonitrile 77-92 4600-13400 Carbon 55, 299, 2013 Spin coated polymer including photoresist 91-95 46000-123000 Appl. Mater. Interface 1, 927, 2009 Carbon nanotube based film SWCNT spray coating 52-98 24-614 J. Am. Chem. Soc. 129, 7758, 2007 ITO films ITO simulated 50-89 3.7-295 Nano Lett. 8, 689, 2008 2D carbon nanofilm (2DC) approx. 2.5-5 nm thick Polymer nanofilms were fabricated using nanostrand This invention layer at the interface MPD 0.5-22-0.05-1 m @ 900 C.-R1-Ar-1 h 73.6 5000 529 MPD 0.5-22-0.05-1 h @ 900 C.-R1-Ar-1 h 51.5 2550 354 MPD 0.1-22-0.02-1 m @ 900 C.-R1-Ar-1 h 80.3 4750 592 Polymer nanofilms were fabricated at the bulk liquid- liquid interface MPD 6-22-3-1 m @ 900 C.-R1-Ar-1 h 62.3 1573 206 MPD 6-22-0.3-1 m @ 900 C.-R1-Ar-1 h 74.0 2212 19 MPD 3-22-0.3-1 m @ 900 C.-R1-Ar-1 h 78.0 1628 78 MPD 3-22-0.15-1 m @ 900 C.-R1-Ar-1 h 76.3 2720 29 MPD 1-22-0.05-1 m @ 900 C.-R1-Ar-1 h 85.6 5193 139 MPD 0.1-22-0.1-1 m @ 900 C.-R1-Ar-1 h 90.1 8976 426 MPD 0.1-22-0.05-1 m @ 900 C.-R1-Ar-1 h 90.7 14481 1294 MPD 0.05-22-0.05-1 m @ 900 C.-R1-Ar-1 h 93.2 20923 4302 MPD 6-22-3-1 m @ 900 C.-R1-H2+Ar-1 h 53.2 1231 94 MPD 6-22-0.3-1 m @ 900 C.-R1-H2+Ar-1 h 71.5 2397 158 MPD 3-22-0.3-1 m @ 900 C.-R1-H2+Ar-1 h 69.0 2069 41 MPD 3-22-0.15-1 m @ 900 C.-R1-H2+Ar-1 h 73.8 3181 23 MPD 1-22-0.05-1 m @ 900 C.-R1-H2+Ar-1 h 84.7 4498 344 MPD 0.1-22-0.1-1 m @ 900 C.-R1-H2+Ar-1 h 88.3 9035 1221 MPD 0.1-22-0.05-1 m @ 900 C.-R1-H2+Ar-1 h 89.6 9370 887 MPD 0.05-22-0.05-1 m @ 900 C.-R1-H2+Ar-1 h 90.8 14475 1923 MPD 0.1-22-0.1-1 m @ 1100 C.-R1-H2+Ar-1 h 84.5 2013 137 MPD 0.1-22-0.005-1 m @ 1100 C.-R1-H2+Ar-1 h 88.2 3204 60 MPD 0.05-22-0.05-1 m @ 1100 C.-R1-H2+Ar-1 h 84.8 2231 65 MPD 0.02-22-0.02-1 m @ 1100 C.-R1-H2+Ar-1 h 90.2 4368 385 MPD 0.1-22-0.1-1 m @ 1100 C.-R1-H2+Ar-5 h 86.0 2102 41 MPD 0.1-22-0.005-1 m @ 1100 C.-R1-H2+Ar-5 h 89.6 3532 98 MPD 0.05-22-0.05-1 m @ 1100 C.-R1-H2+Ar-5 h 87.5 2226 71 MPD 0.02-22-0.02-1 m @ 1100 C.-R1-H2+Ar-5 h 91.3 4725 730 PPD 0.1-22-0.1-1 m @ 1100 C.-R1-H2+Ar-1 h 90.1 3524 959 PIP 0.1-22-0.1-1 m @ 1100 C.-R1-H2+Ar-1 h 87.4 2683 187

(135) The microporous structure was analysed using N.sub.2 adsorption measurement at 77K. Brunauer-Emmett-Teller (BET) surface area, microporous area and volume were calculated from the N.sub.2 adsorption isotherm. Pore size distribution was analysed using 2D-NLDFT method with pores from 0.35 to 25 nm considering 2D model of finite slit pores having a diameter-to-width aspect ratio of 4. Micropore volume was calculated from the t-plot calculation. Polymer nanofilms powder was made at the bulk interface and carbonised under different gas and temperature conditions. The calculated BET surface area was up to 609 m.sup.2g.sup.1 with microporous area of up to 502 m.sup.2g.sup.1 and micropore volume of up to 0.2 cm.sup.3g.sup.1 and total pore volume measured at 0.99 P/P.sub.o was 0.5 cm.sup.3 g.sup.1. Calculated pore size was always about 0.52 nm for all nanofilms however their pore volume changes widely depending on the thickness and crumpleness of the 2D carbon nanofilms. The adsorption isotherm and pore size distribution calculated from 2D-NLDFT model for different carbon nanofilms prepared from MPD-TMC and PIP-TMC are presented in FIG. 34.

(136) While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.

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