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Example 12

Atomic Force Microscopy (AFM) Characterization of Graphene Flakes.

For graphene flake characterization, a sample of graphene/EC dispersion in ethanol was deposited onto Si/SiO₂ for AFM characterization. Prior to sample deposition, Si/SiO₂ wafers were immersed in 2.5 mM 3-aminopropyl triethoxysilane (Aldrich, 99%) in 2-propanol (Macron Chemicals, 99.5%) for 30 minutes, after which they were rinsed with 2-propanol and blown dry under a stream of N₂. A diluted graphene dispersion was dropcast onto the wafers and left for 10 minutes, after which it was blown dry with N₂ and rinsed with 2-propanol. To remove ethyl cellulose and residual 3-aminopropyl triethoxysilane, the samples were annealed at 400° C. in a tube furnace for 30 minutes. AFM images were obtained using a Bruker ICON PT AFM System in tapping mode with a Veeco Model RTESP (MPP-11100-10) cantilever. The images were collected with 2 μm×2 μm scans, and particle characteristics were determined using Nanoscope Analysis software. Flake thickness was determined from line scans, and flake area was measured automatically using the software. Flake thickness was measured for 355 flakes, and flake area was measured for 216 flakes. (See FIGS. 9A-C.)

Example 12

Atomic Force Microscopy (AFM) Characterization of Graphene Flakes.

For graphene flake characterization, a sample of graphene/EC dispersion in ethanol was deposited onto Si/SiO₂ for AFM characterization. Prior to sample deposition, Si/SiO₂ wafers were immersed in 2.5 mM 3-aminopropyl triethoxysilane (Aldrich, 99%) in 2-propanol (Macron Chemicals, 99.5%) for 30 minutes, after which they were rinsed with 2-propanol and blown dry under a stream of N₂. A diluted graphene dispersion was dropcast onto the wafers and left for 10 minutes, after which it was blown dry with N₂ and rinsed with 2-propanol. To remove ethyl cellulose and residual 3-aminopropyl triethoxysilane, the samples were annealed at 400° C. in a tube furnace for 30 minutes. AFM images were obtained using a Bruker ICON PT AFM System in tapping mode with a Veeco Model RTESP (MPP-11100-10) cantilever. The images were collected with 2 μm×2 μm scans, and particle characteristics were determined using Nanoscope Analysis software. Flake thickness was determined from line scans, and flake area was measured automatically using the software. Flake thickness was measured for 355 flakes, and flake area was measured for 216 flakes. (See FIGS. 9A-C.)

Example 5

Characterization of Printed Patterns: The width of the printed lines was measured from optical micrographs obtained on an Olympus optical microscope. The line thickness was measured using a Bruker Contour GT 3D Optical Microscope. For line thickness measurements and height profiles, the height data were averaged over 0.3 to 2 mm of line length to average out the substrate roughness. Statistics for line thickness were based on ˜25 measurements for each data point, and statistics for line width were based on 10 measurements for each data point. For electrical measurements and AFM/SEM images, the patterns were annealed at 250° C. for 30 minutes in a tube furnace, with a stepped temperature ramp to avoid temperature overshoot. For SEM images, a 5 nm film of Au was sputtered onto the samples to mitigate charging effects. SEM images were obtained on a Hitachi SU8030 Field Emission SEM. AFM images were obtained using a Bruker ICON PT AFM System in tapping mode with a Veeco Model RTESP (MPP-11100-10) cantilever. Line resistance was measured using a two-probe measurement technique with Au probes, such that the contact resistance was negligible. Measurements of the evolution of film thickness with annealing were performed on inkjet-printed films on Si/SiO₂ using a Dektak 150 Stylus Surface Profiler.