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SUPPLEMENTARY MATERIALLARGE AREA ULTRA-THIN GRAPHENE FILMS FOR FUNCTIONAL PHOTOVOLTIAC DEVICESMallika Dasari, a Matthew Hautzinger, a Haiyan Fan-Hagenstein, b Brice Adam Russell,c Aldo D. Migone,c Punit Kohli a, *aDepartment of Chemistry & Biochemistry and cDepartment of Physics, Southern Illinois University, Carbondale, Illinois 62901, United States.bDepartment of Chemistry, School of Science and Technology, Nazarbayev University, Astana 010000, Kazakhstan.*pkohli@chem.siu.eduPreparation of Large Scale Graphene Using Methyl Cellulose and Filter Paperleft271145Fig. S1.Stepwise procedure of graphene synthesis from cellulose paper. (A) A Whatman filter paper No. 40 was cut into a desired shape and dimension. (B) The filter paper was soaked in iron catalyst solution and was dried at 80oC for 15 min. (C) Graphitic paper was formed at 900oC under the flow of N2 gas. The area of the cellulose paper from (A), (B), and (C) were ~9.7 cm2. (D) TEM of the iron nanoparticles with a size distribution between 5 to 30 nm. (E) UV-Vis spectrum of a graphitic sample prepared at 900oC in ethanol. A peak at 273 nm in the UV region of the spectrum is due to graphene carbon.00Fig. S1.Stepwise procedure of graphene synthesis from cellulose paper. (A) A Whatman filter paper No. 40 was cut into a desired shape and dimension. (B) The filter paper was soaked in iron catalyst solution and was dried at 80oC for 15 min. (C) Graphitic paper was formed at 900oC under the flow of N2 gas. The area of the cellulose paper from (A), (B), and (C) were ~9.7 cm2. (D) TEM of the iron nanoparticles with a size distribution between 5 to 30 nm. (E) UV-Vis spectrum of a graphitic sample prepared at 900oC in ethanol. A peak at 273 nm in the UV region of the spectrum is due to graphene carbon.Moire patterns12701428750Fig. S2. (A) The schematic presentation of the two graphene layers oriented and overlapped at an angle yielding Moire pattern. (B) and (C) show Moire patters formed by multiple graphene layers.00Fig. S2. (A) The schematic presentation of the two graphene layers oriented and overlapped at an angle yielding Moire pattern. (B) and (C) show Moire patters formed by multiple graphene layers.A different type of interference pattern occurred when two or more layers of graphene were stacked on top of one other.?These patterns are called Moire patterns. Triangular and straight bands were observed in few layered graphene samples., We observed similar patterns in our HRTEM images of graphene flakes grown at 900oC (Figs. S2B and S2C). These patterns were not observed in the samples grown below 800oC suggesting lack of ordered structures for the samples grown below 900oC (Fig. 1). XRD left8255Fig. S3. (A) The XRD spectrum of cellulose powder exhibited two peaks at 2θ~8o and ~19o from polymeric chains of cellulose. (B) The XRD spectrum of carbonized cellulose synthesized at T=900oC in the absence of catalyst exhibited non-graphitic, amorphous nature of carbon.0Fig. S3. (A) The XRD spectrum of cellulose powder exhibited two peaks at 2θ~8o and ~19o from polymeric chains of cellulose. (B) The XRD spectrum of carbonized cellulose synthesized at T=900oC in the absence of catalyst exhibited non-graphitic, amorphous nature of carbon.Characterization of Graphene Synthesized as a Function of Synthetic TemperatureThermogravimetric Analysis:center152400Fig. S4. The decomposition phenomenon of cellulose into graphene demonstrated using TGA. TGA shows a complete dehydration and decomposition of the cellulose ~337oC. A second step was observed where Fe (III) reduction occurred at 610oC. The reduction of Fe (III) by carbon yielded elemental Fe and CO2 (Eq.4). At this stage oxygen and carbon derivatives were removed leaving predominantly carbon residues which annealed to highly ordered graphene ~900oC.00Fig. S4. The decomposition phenomenon of cellulose into graphene demonstrated using TGA. TGA shows a complete dehydration and decomposition of the cellulose ~337oC. A second step was observed where Fe (III) reduction occurred at 610oC. The reduction of Fe (III) by carbon yielded elemental Fe and CO2 (Eq.4). At this stage oxygen and carbon derivatives were removed leaving predominantly carbon residues which annealed to highly ordered graphene ~900oC.Surface area of graphene films.971550240665Fig. S5. Nitrogen adsorption isotherm at 77.3?K on the annealed (900oC) sample of graphene powder; the measurements were conducted for?relative pressures between 0 and 1. The substep, indicated by the arrow?corresponds to the formation of a second adsorbed?layer of N2 on the graphene powder.00Fig. S5. Nitrogen adsorption isotherm at 77.3?K on the annealed (900oC) sample of graphene powder; the measurements were conducted for?relative pressures between 0 and 1. The substep, indicated by the arrow?corresponds to the formation of a second adsorbed?layer of N2 on the graphene powder.Brunauer, Emmett and Teller (BET) is an extensively used method to measure the specific surface area of a material. The surface are of graphite synthesis using our synthetic procedure was determined using the BET equation. The surface area of the sample is obtained by plotting the adsorption isotherm data in terms of the BET equation, and obtaining the monolayer capacity from the plot. The N2 adsorption isotherm studies were performed at 77.3 K (liquid nitrogen), and the measurements were conducted for pressures up to the corresponding saturated vapor pressure. The specific surface area of the synthesized graphite that was annealed at 900oC was measured to be 2.8 m2/g (Fig. S5). The N2 adsorption isotherm at 77.3 K on the annealed graphite showed a step at a relative pressure of ~0.3 (Fig. S5). This step corresponds to the formation to the formation of a second layer on the surface of the graphite.left233680Fig. S6. (A) An SEM image of the cross section where EDS spectrum was acquired. (B) EDS shows element C and Fe from CNTs; Au, Ag, and Al were from the conductive metal coating, conductive bridge made between SEM stub and substrate coated with MWCNTs, and Al resulted from the alumina template.0Fig. S6. (A) An SEM image of the cross section where EDS spectrum was acquired. (B) EDS shows element C and Fe from CNTs; Au, Ag, and Al were from the conductive metal coating, conductive bridge made between SEM stub and substrate coated with MWCNTs, and Al resulted from the alumina template.Energy Dispersive Spectroscopy:Photo-electrical characterization left180975Fig. S7. (A) Photo-induced current (PIC)-applied voltage (V) dependence for a two electrode device confirmed that PIC increased as the V was increased. (B) Fluorescence emission spectra of the composite at applied voltage of 0 and 10V, respectively. The fluorescence emission intensity at 10V has decreased by ~4 times compared to the emission intensity at 0V indicating that many excitons were charge separated at 10V. 00Fig. S7. (A) Photo-induced current (PIC)-applied voltage (V) dependence for a two electrode device confirmed that PIC increased as the V was increased. (B) Fluorescence emission spectra of the composite at applied voltage of 0 and 10V, respectively. The fluorescence emission intensity at 10V has decreased by ~4 times compared to the emission intensity at 0V indicating that many excitons were charge separated at 10V. References ................
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