Herein, a new carbon-based graphitic membrane composed of laminated graphitic nanoribbons with a nanometer-scale width and micrometer-scale length, the graphitic nanoribbon membrane, is reported. Compared to the existing graphitic membranes, such as those composed of graphene oxide and carbon nanotubes, the developed membrane exhibits several unique characteristics in pressure-driven systems. First, the short diffusion length through its interlayer and the free volume of its stacked nanoribbons result in high solvent flux regardless of solvent polarity (water: 25-250 L m h bar; toluene: ∼975 L m h bar; hexane: ∼240 L m h bar). The flux value for water is one order of magnitude higher, while that for nonpolar organic solvents is two to three orders of magnitude greater than the corresponding flux values obtained through commercially available nanofiltration membranes. Second, the membrane exhibits good separation performance, particularly with organic dye molecules (∼100%) and trivalent ions (∼60%), maintaining high solvent flux during extended filtration. Finally, the membrane exhibits high stability in various fluids, e.g., 1 M HCl solution, 1 M NaOH solution, toluene, ethanol, and water, as well as under hydraulic pressures of up to 50 bar. Electron microscopy observation and simulation results suggest that such distinctive features of the membrane are related to the entangled thin multilayers of the graphitic nanoribbons, which possibly originate from the high aspect ratio and narrow width of the nanoribbons.
the range of aligned molecules may be limited to those possessing strong π-π interactions with 2D materials. [19][20][21] In this regard, grooved surfaces can provide a powerful approach, because the anchoring energy and anchoring direction of their patterned surface can be artificially designed by controlling the direction, amplitude, and period of the patterned substrate according to Berreman's theory. [22][23][24] Despite the success achieved with aligning lyotropic chromonic liquid crystals (LC) by introducing patterned surfaces with high aspect ratio, [22] the anchoring energy of the grooved surfaces used in these attempts is still low for anchoring of various soft materials such as polymeric materials and dendrimers. This limitation is due to the restriction of the surface anchoring energy of the patterned surface to above 20 nm by the resolution of current lithographic techniques. [22][23][24] Here, we demonstrate for the first time that black phosphorus (BP) with atomic-scale grooves and a puckered honeycomb structure of adjacent phosphorus atoms enables alignment of a wide range of soft materials, including thermotropic LCs such as 4-cyano-4′-alkylbiphenyl (nCB) and 4-cyano-4′-alkyloxybiphenyl (nOCB), the lyotropic LC sunset yellow (SSY), and fluorinated dendrimers. Especially, SSY and dendrimer molecules are difficult to align through known surfaceanchoring techniques. We found that the planar direction of the aligned soft materials is fixed in a single direction, following the direction of the atomic grooves of BP. This result is attributed to the regular and atomic-scale grooves of BP with height of 2 Å and period of 4.33 Å. [26] These induce an ultrastrong azimuthal anchoring energy of soft materials, ≈0.235 N m −1 (for 5CB), which is two orders of magnitude higher than that of previously reported anchoring methods. Thus, our surface-anchoring technology represents a new approach for aligning a wide range of soft materials using well-designed atomic-scale grooves of BP. Such an approach can be used in various methods for realizing high-performance optoelectronic devices and biotechnological applications.The overall procedure for aligning various soft materials on the BP surface is illustrated in Figure 1. Briefly, BP flakes were exfoliated through a mechanical method using commercial 3M tape and then transferred onto SiO 2 /Si substrates for polarized optical microscopy (POM) observations and onto a Si nitride (SiN) grid for transmission electron microscopy (TEM) observations (Figure 1a). [27] The BP substrate was coated with various soft materials, namely, nCB, nOCB, SSY, and fluorinated dendrimer, by either spin-coating or a sandwiched-cell or solution-casting method, depending on the materials and observation tools (for specific experimental conditions, see the Experimental Section; Figure 1b). Thermotropic nCBs, nOCBs, and lyotropic SSY were used because the anchoring behavior of Controlling the molecular orientation of soft materials is one of the most important issues in physical and materials ...
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