Two renewable, structurally analogous monomers, isosorbide undecenoate (IU) and glucarodilactone undecenoate (GDLU) reacted with pentaerythritol tetrakis(3-mercaptopropio8 nate) (PETT) via thiol−ene photopolymerization to form IU−PETT and GDLU−PETT thermosets. Despite their chemical similarity, uniaxial tensile testing showed that GDLU−PETT exhibited a strain-hardening behavior and is significantly tougher
12 than IU−PETT. To understand this observation, in situ tensile testing and wide-angle X-ray scattering experiments (WAXS) were conducted. While the 2D WAXS patterns of IU−PETT displayed an isotropic halo during uniaxial deformation, they exhibited a change from an isotropic halo to a pair of scattering arcs for the GDLU−PETT samples. Density functional theory calculations further revealed that the alkyl chains on GDLU adopt a linear conformation, while the alkyl chains on IU are angled. Based on these results, we postulate that the linear GDLU molecules can more easily order and align during uniaxial deformation, hence, increasing intermolecular interactions between the GDLU molecules and contributing to the observed strain hardening behavior of their thermosets. This study exemplifies how molecules with subtle differences in their chemical structures can alter the structures and thermophysical properties of the resulting polymers in unpredictable ways.
A layered graphene oxide/ethylenediamine (GO/EDA) composite film was developed by exposing aqueous GO liquid crystal (GOLC) coating to EDA vapor and its effects on the gas barrier performance of GO film were systematically investigated. When a GO/EDA coating with a thickness of approximately 1 μm was applied to a neat polyethylene terephthalate (PET) film, the resultant film was highly impermeable to gas molecules, particularly reducing the gas permeance up to 99.6% for He and 98.5% for H2 in comparison to the neat PET film. The gas barrier properties can be attributed to the long diffusion length through stacked GO nanosheets. The EDA can crosslink oxygen-containing groups of GO, enhancing the mechanical properties of the GO/EDA coating with hardness and elastic modulus values up to 1.14 and 28.7 GPa, respectively. By the synergistic effect of the viscoelastic properties of GOLC and the volatility of EDA, this coating method can be applied to complex geometries and EDA intercalation can be spontaneously achieved through the scaffold of the GOLC.
Lignin is a biorenewable precursor source suitable for the production of low-cost carbon fibers. In this work, softwood lignin was chemically modified with fatty acids to employ UV-triggered oxidative reactions occurring at long alk(en)yl chains as a pretreatment prior to thermostabilization. The chemical transformation of oleic acid-functionalized lignin (OAFL) under the UV irradiation was the free radical-based cross-linking reaction assisted by atmospheric oxygen, which successfully formed oxidatively cross-linked networks of lignin derivatives at the surface of the fiber. We observed that OAFL showed more rapid oxidative cross-linking than stearic acid-functionalized lignin (SAFL) because the presence of carbon–carbon double bond in OAFL contributed to the formation of more stable allyl radicals in addition to alkyl radicals under the UV irradiation. This UV pretreatment played a pivotal role in the conversion of flexible pristine OAFL fibers into infusible fibers during the subsequent thermostabilization step at the elevation rate of 2 °C/min without melt deformation. As the elevation rate of 2 °C/min is among the fastest thermostabilization process for lignin-derived carbon fibers, the duration of the thermostabilization of the OAFL-derived fibers in this study (∼2 h) is considerably less than previously reported ones. In addition, the UV irradiation process in this study requires less power (150 W) and exposure time (8 min), which can be appreciated by carbon fiber manufacturers aiming to reduce the fabrication cost. Therefore, the chemical functionalization with fatty acids envisages the possibility to produce carbon fibers from lignin precursors via a rapid stabilization step with spending less amount of time and energy.
The development of carbon structures in mesophase pitch fibers was studied with controlling the initial temperature (Ti) of the stabilization process to optimize the mechanical properties of final carbon/graphite fibers. To understand the relationship between Ti and chemical structural change by thermostabilization, the pitch fiber was thermally treated from various Tis up to 350 °C with an elevation rate of 2 °C/min. Various analyses of the oxygen species in the fiber revealed that changing Ti governed the amount and distribution of oxygen in the stabilized fibers, while determining the effective duration of thermostabilization and preserving hydroxyl groups originally present in the precursor fiber. Among various samples, stabilized fibers with Ti of 150 °C contained the largest amount of oxygen in the fiber, resulting in the highest degree of polyaromatic inner structure after the subsequent carbonization and graphitization to show the best tensile strength and modulus. We also demonstrated that the optimal mechanical, electrical, and thermal properties of the resulting graphite fiber were comparable to those of commercially available fiber products (XN-80-60s), indicating that Ti should be carefully considered to enhance the properties of carbon and graphite fibers.
The preparation of carbon materials based hydrogels and their viscoelastic properties are essential for their broad application and scale-up. However, existing studies are mainly focused on graphene derivatives and carbon nanotubes, and the behavior of graphene nanoribbon (GNR), a narrow strip of graphene, remains elusive. Herein, we demonstrate the concentration-driven gelation of oxidized GNR (graphene oxide nanoribbon, GONR) in aqueous solvents. Exfoliated individual GONRs sequentially assemble into strings (∼1 mg/mL), nanoplates (∼20 mg/mL), and a macroporous scaffold (50 mg/mL) with increasing concentration. The GONR hydrogels exhibit viscoelastic shear-thinning behavior and can be shear-coated to form large-area GONR films on substrates. The entangled and stacked structure of the GONR film contributed to outstanding nanofiltration performance under high pressure, cross-flow, and long-term filtration, while the precise molecular separation with 100% rejection rate was maintained for sub-nanometer molecules.
During the course of studying silicon-containing diblock copolymers, it was discovered that poly(3,5-di(trimethylsilyl)styrene)-block-poly(3,4-methylenedioxystyrene) (PDTMSS-b-PMDOS) showed very unusual thermal properties. The material can be recovered as a free-flowing powder despite heating above 250 °C. To better understand this behavior, homopolymers of the 3,5-disubstituted styrenes, poly(3,5-di(trimethylsilyl)styrene) (PDTMSS) and poly(3,5-di-tert-butylstyrene) (PDtBS), were prepared. These polymers are soluble in common organic solvents and formed clear, glassy thin films upon spin coating. These homopolymers were studied by differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS), dynamic mechanical analysis (DMA), and temperature-programmed ellipsometry. These experiments document the lack of a conventional glass transition in these materials below their decomposition temperature. A series of statistical copolymers of PDTMSS and PDtBS with styrene was synthesized and studied by DSC in an attempt to establish the Tg of the homopolymers by model-based extrapolation.
Structural inhomogeneity of stabilized polyacrylonitrile (PAN) fibers was systematically investigated. When the temperature was not high enough (below 200 °C in an air atmosphere) to initiate either cyclization or oxidation, absorbed oxygen related functional groups on the surface of PAN fibers were observed. However, when the temperature was above 200 °C, oxygen started to penetrate into PAN fibers through the skin, resulting in an increase in the oxygen content and significant relaxation of molecular structure. As expected, oxygen was diffused from the skin to the core with increasing temperature. At 240 °C, Raman spectroscopy confirmed that cyclization homogeneously occurred in the whole cross-section of fibers. However, higher temperature (≥260 °C) resulted in different ratios of D and G bands depending on both position and temperature, indicating that inhomogeneous structures were obtained due to temperature gradient by exothermic reactions. In addition, oxygen level in the core was much less than that on the surface. This provides evidence that there is a limit to equalize oxygen content across the fiber. Therefore, cyclization, dehydrogenation, and oxidation as critical reactions in the stabilization of PAN fibers started simultaneously. Above a certain temperature, in particular, increased activation energy due to oxidation at the surface can cause significant inhomogeneity of the resulting fibers.
Carbohydrate-derived monomers were synthesized and thiol-ene photopolymerization was employed to produce thermoset films and fibers from the biobased dienes isosorbide 10-undecenoate (IU) and glucarodilactone 10-undecenoate (GDLU) and multifunctional thiols. The resulting materials, comprising up to 94% biorenewable content, were flexible, crosslinked, and had mechanical and thermal properties that varied with IU and GDLU content (e.g., rubbery plateau storage moduli = 6.1 to 10.5 MPa at 40 °C above the glass transition temperature; glass transition temperatures = -9.9 to 27 °C by differential scanning calorimetry; degradation temperatures = 238 to 347 °C by thermogravimetric analysis). By combining electrospinning with in-situ UV irradiation and carefully controlling the monomer mixture viscoelasticity and orifice-to-collector flight time, uniformly-cured fibers were produced directly from the monomer feed when the ene monomers contained either 100% GDLU or 50% GDLU/50% IU. The resulting GDLU-containing thermoset films and fibers were readily decomposed into soluble small molecule fragments in basic aqueous media due to the intrinsic degradability of the GDLU unit. This study highlights the potential advantages of using carbohydrate-derived monomers for producing thermoset fibers and nonwovens that are both renewable and degradable.
The ability to organize metal nanoparticles over the macroscopic length scale has fundamental implications for advanced plasmonic applications. In particular, linear assemblies of anisotropic nanorods (NRs) may represent a dichroic superstructure, in which plasmonic extinction is inherently dependent on the direction of light polarization. As plasmonic properties are interconnected with optics, electronics, catalysis, and sensing, dichroism in plasmonic systems can stimulate interesting opportunities in many fields of chemistry. However, the preparation of dichroic structures with a single orientation at the centimeter scale remains a significant challenge. Herein, directed self‐assemblies of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) diblock copolymers on lithographical patterns are applied to produce a linear pattern of Au NRs. Periodic nanogrooves from plasma‐etched PS‐b‐PMMA nanodomains facilitate the dense packing of Au NRs into end‐to‐end alignment, which entail strong plasmonic coupling among longitudinal plasmonic modes. Because the resulting NR assemblies have uniform orientation, their dichroic functions can be examined by conventional UV–vis spectroscopy without the aid of single‐particle measurements. Interestingly, both transverse and longitudinal localized surface plasmonic resonance peaks can be turned on and off under two polarized lights in orthogonal directions. Moreover, the resulting superstructures can be transferred onto various substrates, allowing the implantation of dichroic functions for numerous plasmonic applications.
Despite a rich choice of two-dimensional materials, which exists these days, heterostructures, both vertical (van der Waals) and in-plane, offer an unprecedented control over the properties and functionalities of the resulted structures. Thus, planar heterostructures allow p-n junctions between different two-dimensional semiconductors and graphene nanoribbons with well-defined edges; and vertical heterostructures resulted in the observation of superconductivity in purely carbon-based systems and realisation of vertical tunnelling transistors. Here we demonstrate simultaneous use of in-plane and van der Waals heterostructures to build vertical single electron tunnelling transistors. We grow graphene quantum dots inside the matrix of hexagonal boron nitride, which allows a dramatic reduction of the number of localised states along the perimeter of the quantum dots. The use of hexagonal boron nitride tunnel barriers as contacts to the graphene quantum dots make our transistors reproducible and not dependent on the localised states, opening even larger flexibility when designing future devices.
A series of covalently cross-linked poly(ionic liquid) networks were prepared using thiol–ene “click” photopolymerization. In these networks, imidazolium groups are placed in the backbone and pendant to the main chain, creating a “hybrid”-type network architecture. The pendant imidazolium groups were incorporated into the networks from monofunctional “ene” monomers that contained either a terminal alkyl group at the imidazolium N-3 position of variable length (R = C1, C4, C8, C12, C16, or C20) or a variable alkyl tether spacer (n = 6 or 10) between the newly formed sulfide and the imidazolium ring. Thermal characterization of these networks indicated a general decrease in Tg as the length of the terminal alkyl chain length increased from C1 to C8, followed by an abrupt increase in Tg up to C20 due to increased van der Waals interactions between longer chains. X-ray scattering data confirmed the presence of chain-extended crystallites within the network cavities for the C16 and C20 systems, leading to the observed increase in Tg and the appearance of a melting transition for both systems. Ionic conductivities of the PIL networks were determined from dielectric relaxation spectroscopy (10–6 to 10–7 S/cm at 30 °C, 30% RH), and a direct correlation with polymer Tg was found.
A series of isotactic polypropylene (iPP) and polyethylene (PE) diblock, tetrablock, and hexablock copolymers (BCPs) were synthesized with tunable molecular weights using a hafnium pyridylamine catalyst. The BCPs were melt blended with 70 wt % high-density PE (HDPE) and 30 wt % iPP commercial homopolymers at concentrations between 0.2 and 5 wt %. The resulting blend morphologies were investigated using TEM, revealing uniformly dispersed iPP droplets ranging progressively in size with increasing BCP content from three-quarters to one-quarter of the diameter of the uncompatibilized mixture. Tensile tests revealed a dramatic enhancement in toughness based on the strain at break which increased from 10% for the unmodified blend to more than 300% with just 0.2 wt % BCP and over 500% with the addition of 0.5 wt % BCP or greater. Incorporation of BCPs in blends also improved the impact toughness, doubling the Izod impact strength to a level comparable to the neat HDPE with just 1 wt % additive. These improved blend properties are attributed to enhanced interfacial strength, which was independently probed using T-peel adhesion measurements performed on laminates composed of HDPE/BCP/iPP trilayers. Thin (ca. ≤100 nm thick) BCP films, fabricated by high-temperature spin coating and molded between the homopolymer films, significantly altered the laminate peel strength, depending on the molecular weight and molecular architecture of the block copolymer. Multilayer laminates containing no BCP or low molecular weight diblock copolymer separated by adhesive failure during peel testing. Sufficiently high molecular weight iPP–PE diblock copolymers and iPP–PE–iPP–PE tetrablock copolymers with significantly lower block molecular weights exhibited cohesive failure of the HDPE film rather than adhesive failure. We propose adhesion mechanisms based on molecular entanglements and cocrystallization for tetrablocks and diblocks, respectively, to account for these findings. These results demonstrate exciting opportunities to recycle the world’s top two polymers through simple melt blending, obviating the need to separate these plastics in mixed waste streams.
Melt blowing is a process in which liquid polymer is extruded through orifices and then drawn by hot air jets to produce nonwoven fibers with average diameters typically greater than one micron. Melt-blown nonwoven fiber products constitute a significant fraction (i.e., more than 10%) of the $50 billion global nonwovens market. Thermoplastic feedstocks, such as polyethylene, polypropylene, poly(phenylene sulfide), and poly(butylene terephthalate), have dominated melt-blown nonwovens because of their combined cost, good chemical resistance, and high-temperature performance. Cross-linked nonwovens from other commodity polymers (e.g., (meth)acrylates, styrenics, silicones, etc.) could be attractive alternatives; however, no commercial cross-linked nonwovens currently exist. Here, cross-linked fibers were produced via one-step melt blowing of thermoreversible Diels–Alder polymer networks comprised of furan- and maleimide-functional methacrylate-based polymer backbones. These dynamic networks de-cross-link and flow like viscous liquids under melt-blowing conditions and then revert to a network via cooling-induced cross-linking during/after melt blowing. Finally, the resulting cross-linked fibers can be recycled after use because of their reversible dynamic nature, which may help address microfiber waste as a significant source of microplastic pollution.
While a number of vegetable oil derivatives have been integrated with petroleum-based materials to prepare thermosetting polymers, existing examples usually incorporate low total biorenewable content into the final product. With the goal of generating thermosets with high biorenewable content, two different soybean oil derivatives with multifunctional thiol and acrylate groups were photocured via thiol-acrylate photopolymerization. For this purpose, L-cysteine, a nonhazardous amino acid, was coupled with epoxidized soybean oil to synthesize a mercaptanized soybean oil derivative containing multiple thiol groups. Following mixing with acrylate counterparts suitable for performing thiol-ene photopolymerizations, these monomer mixtures were processed into thermoset films (via monomer mixture film casting followed by photopolymerization) and fibers (via simultaneous electrospinning of the monomer mixture and photopolymerization in-flight). The resulting materials possessed high biobased carbon content (BCC; over 90%) and higher elasticity than cross-linked acrylated epoxidized soybean oil without the thiol-containing component. This can be attributed to a change in the cross-link density that is controlled by different photopolymerization mechanisms (e.g., step-growth polymerization vs. chain-growth homopolymerization). We anticipate that the approaches outlined in this study could be generalized to other bioderived triglyceride oils for increasing the BCC and imparting biodegradability in a number of materials applications.
We report the synthesis of arrayed nanorings with tunable physical dimensions from thin films of polystyrene-block-poly(4-vinylpyridine) (PS-P4VP) micelles. For accurate control of the inner and outer diameters of the nanorings, we added imidazolium-based ionic liquids (ILs) into the micellar solution, which were eventually incorporated into the micellar cores. We observed the structural changes of the micellar cores coated on a substrate due to the presence of ILs. The spin-coated micellar cores were treated with an acidic precursor solution and generated toroid nanostructures, of which size depended on the amount of IL loaded into the micelles. We then treated the transformed micellar films with oxygen plasma to produce arrays of various metal and oxide nanorings on a substrate. The spacings and diameters of nanorings were governed by the molecular weight of the PS-P4VP and the amount of IL used. We also demonstrated that arrayed Pt nanorings enabled the fabrication of reduced graphene oxide (rGO) anti-nanoring arrays via a catalytic tailoring process.
We report the growth and transfer of centimeter-sized, epitaxial hexagonal boron nitride (h-BN) few-layer films using Ni(111) single-crystal substrates. The h-BN films were heteroepitaxially grown on 10 × 10 mm2 or 20 × 20 mm2 Ni(111) substrates using atmospheric pressure chemical vapor deposition with a single ammonia-borane precursor. The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and the remaining Ni(111) substrates were repeatedly re-used. A careful analysis of the growth parameters revealed that the crystallinity and area coverage of the h-BN films were mostly sensitive to the sublimation temperature of the ammonia-borane source. Moreover, various physical characterizations confirmed that the grown films exhibited the typical characteristics of hexagonal boron nitride layers over the entire area. Furthermore, the heteroepitaxial relationship between h-BN and Ni(111) and the overall crystallinity of the film were thoroughly investigated using a synchrotron radiation X-ray diffraction analysis including θ–2θ scans, grazing incident diffraction, and reciprocal space mapping. The crystallinity at the microscopic scale was further investigated using transmission electron microscopy (TEM)-based techniques, including selective area electron diffraction pattern mapping, electron back-scattered diffraction, and high-resolution TEM.
In this study, the large-area tailoring of reduced graphene oxide (rGO) with tunable arrays of Pt nanostructures has been demonstrated. We synthesized arrays of catalytic Pt nanoparticles, nanowires, and their combined nanostructures from self-assembled thin films of polystyrene-block-poly(4-vinylpyridine) copolymers and their micelles. Then, rGO was transferred onto these Pt nanostructures, which were capable of catalyzing the oxidative elimination of carbon atoms from the rGO nanoregions in contact with the Pt, resulting in successful pattern transfer from the Pt nanoarrays onto the rGO, forming various nanostructures, such as nanoholes, nanoribbons, and perforated nanoribbons. Moreover, we transferred the tailored rGO onto a transparent and flexible polymeric substrate. The size and periodicity of the rGO nanostructures were controlled on the nanometer scale by adjusting those of the Pt nanostructures, which were strongly dependent on the molecular weights of the copolymers. In addition, arrayed Pt nanowires were aligned in a topographically patterned substrate by the directed self-assembly of the copolymers, enabling the fabrication of well-aligned rGO nanoribbon and nanosquare arrays.
We report controlled branching and eventual crosslinking in supracolloidal chains by introducing well-defined trifunctional patchy micelles. Uniform micelles having three patches were induced from core-crosslinked micelles of diblock copolymers. Three patches in the micelles served as functional groups for crosslinking as well as branching in supracolloidal polymerization.
We report the construction of non-hexagonal arrays of nanoparticles by the template-assisted self-assembly of polystyrene-block-poly(4-vinylpyridine) copolymer micelles. Diblock copolymers were spin-coated onto nanoscale TiO2 templates, which successfully guided the placement of the micelles to form unconventional assemblies such as linear, zigzag, and Kagome array structures. These arrangements, different from the usual quasi-hexagonal arrays of copolymer micelles spin-coated onto a flat substrate, greatly depended on the physical dimension of both the template and the micelles. Subsequent treatment of the copolymer micelles assemblies with oxygen plasma resulted in various non-hexagonal arrays of Au nanoparticles while preserving the arrangement of the original micelles on the template.
We demonstrate the large-area lithography-free ordered perforation of reduced graphene oxide (rGO) and graphene grown by chemical vapor deposition (CVD) with arrayed Pt nanoparticles (NPs) prepared by using self-patterning diblock copolymer micelles. The rGO layers were perforated by Pt NPs formed either on top or bottom surface. On the other hand, CVD graphene was perforated only when the Pt NPs were placed under the graphene layer. Various control experiments confirm that the perforation reaction of CVD graphene was catalyzed by Pt NPs, where the mechanical strain as well as the chemical reactivity of Pt lowered the activation energy barriers for the oxidation reaction of C═C bonds in graphene. Systematic atomic force microscopy and Raman analyses revealed the detailed perforation mechanism. The pore size and spacing can be controlled, and thus our present work may open a new direction in the development of ordered nanopatterns on graphene using metal NPs.
Superhydrophobic surfaces are normally fixed on the chosen materials. Here, we report transferrable superhydrophobicity which was enabled by fabricating TiO2 nanorods on a reduced graphene oxide (rGO) film. Superhydrophobic TiO2 nanorods were first synthesized from a nanoporous template of block copolymers (BCPs). The controllability over the dimension and shape of nanopores of the BCP template allowed for the adjustment of TiO2 nanostructures for superhydrophobicity. Since the rGO film provided effective transferring, TiO2 nanorods were conveyed onto a flexible polymer film and a metal substrate. Thus, the surface of the designated substrate was successfully changed to a superhydrophobic surface without alteration of its inherent characteristics.
We investigated the electrooxidative dissolution of uniformly distributed Au nanoparticles (NPs) without an extra adhesion layer or capping agent. Diblock copolymer micelles were exploited to fabricate the arrays of Au NPs where not only diameter of the particles but also inter-particle spacing, and thus coverage were finely controlled. The peak potential for electrochemical oxidation shifted greater as a function of coverage of NPs than the size.
We demonstrated the fabrication of ZnO nanorods and nanowalls directly on flexible substrates by combining a hydrothermal growth technique with nanoporous templates obtained from block copolymers. First, templates with cylindrical nanopores in two sizes and a template with nanogrooves were fabricated on flexible substrates by employing block copolymers with different molecular weights. From these nanotemplates, we synthesized vertically oriented ZnO nanorods with controlled diameters and ZnO nanostructures in a wall shape. Because the ZnO nanostructures were produced without an electrically insulating epitaxial layer, the semiconducting nature of the ZnO nanorods was characterized as synthesized. Thus, this combined method of hydrothermal growth and block copolymer templates for ZnO nanostructures can be directly applied to flexible electronic devices without alteration of the substrate.
We fabricated a single-layered film consisting of spherical micelles of diblock copolymers and one-dimensional Au nanorods that were surface modified with the same polymer as the corona block of the copolymers. When the diameters of micelles were larger than the lengths of the nanorods, spherical micelles arranged in a hexagonal configuration surrounded by nanorods with their long axes perpendicular to the radial direction of the micelles. This arrangement provided selective organization of the Au nanorods and Ag nanoparticles which were selectively synthesized within the cores of the copolymer micelles. Thus, position-selective arrangement of Au nanorods and Ag nanoparticles was demonstrated at the nanometer scale such that a homogenous distribution of two different nanomaterials over a large area without aggregation was achieved.
Reduced graphene oxide (rGO) films are decorated with non-overlapping Au nanoparticles using diblock copolymer micelles that provide controllability over the number density as well as the diameter of the nanoparticles. This synthetic process produces a pure Au surface without extra layers. Furthermore, the rGO film enables the transferability of the Au nanoparticles without deterioration of their arrays. Thus, the controllability of the Au nanoparticles and their transferability with rGO films allow the effective modification of electrochemical electrodes. With a glassy carbon electrode modified with an rGO film with Au nanoparticles, high electrochemical activity is observed in the oxygen reduction reaction (ORR). Furthermore, it is possible to identify a size-dependent ORR mechanism, showing that Au nanoparticles with an average diameter of 8.6 nm exhibit a 4-electron direct reduction of O2 to H2O.
We report the density- and size-controlled growth of zinc oxide (ZnO) nanorod arrays on arbitrary substrates using reduced graphene oxide (rGO) nanodot arrays. For the controlled growth of the ZnO nanorod arrays, rGO nanodot arrays with tunable density and size were designed using a monolayer of diblock copolymer micelles and oxygen plasma etching. While the diameter and number density of the ZnO nanorods were readily determined by those of the rGO nanodots, the length of the ZnO nanorods was easily controlled by changing the growth time. x-ray diffraction and electron microscopy confirmed that the vertically well-aligned ZnO nanorod arrays were heteroepitaxially grown on the rGO nanodots. Strong, sharp near-band-edge emission peaks with no carbon-related peak were observed in the photoluminescence spectra, implying that the ZnO nanostructures grown on the rGO nanodots were of high optical quality and without carbon contamination. Our approach provides a general and rational route for heteroepitaxial growth of high-quality inorganic materials with tunable number density, size, and spatial arrangement on arbitrary substrates using rGO nanodot arrays.
We have investigated the effect of argon (Ar) plasma treatment on the surface of graphite and the hydrothermal growth of zinc oxide (ZnO) microstructures. With the plasma treatment, the growth behavior of ZnO microrods on the graphite substrates changed drastically. After the graphite surface was exposed to the Ar plasma, the number density of ZnO was one order of magnitude higher than that on the pristine graphite without plasma treatment. Raman spectroscopy revealed that Ar plasma treatment created the structural defects on the graphite surfaces and decreased the mean distance of defects. Surface characterization through atomic force microscopy and X-ray photoelectron spectroscopy showed that the graphite surface was roughened and that oxygen–carbon bonding was formed. The enhanced nucleation of ZnO can be explained by the generation of structural defects, surface roughness, and surface functional groups on the graphite substrate. Therefore, Ar plasma treatment can be used as a simple method to engineer the surface properties of graphite substrates and to control the crystal nucleation and growth of inorganic materials on their surface.
Three-dimensional nanostructures of TIO2 related materials including nanotubes, electron acceptor materials in hybrid polymer solar cells, and working electrodes of dye sensitized solar cells (DSSCs) were visualized by electron tomography as well as TEM micrographs. The regions on the wall of TIO2 nanotubes where the streptavidins were attached were elucidated by electron tomogram analysis. The coverage of TIO2 nanotubes by streptavidin was also investigated. The TIO2 nanostructures in hybrid polymer solar cells made by sol–gel and atomic layer deposition (ALD) methods and the morphologies of pores between TIO2 particles in DSSCs were also observed by reconstructed three-dimensional images made by electron tomography.
Nanostructured graphenes such as nanoribbons, nanomeshes, and nanodots have attracted a great deal of attention in relation to graphene-based semiconductor devices. The block copolymer micellar approach is a promising bottom-up technique for generating large area nanostructures of various materials without using sophisticated electron-beam lithography. Here we demonstrate the fabrication of an array of graphene nanodots with tunable size and inter-distance with the utilization of a monolayer of diblock copolymer micelles. Au nanoparticles were synthesized in the micellar cores and effectively worked as shielding nanostructures in generating graphene nanodots by oxygen plasma etching. We also controlled the radius and inter-distance of graphene nanodots simply through the molecular weight of the copolymers.
리그닌 지방산 유도체, 이를 포함하는 탄소 섬유 제조용 전구체, 상기 전구체로부터 제조된 방사 섬유 및 탄소 섬유, 그리고 상기 리그닌 지방산 유도체의 제조방법 및 이를 이용한 리그닌 유도체 기반 탄소 섬유의 제조방법이 개시된다. 상기 리그닌 지방산 유도체는 페놀화 리그닌(phenolated lignin)이 지방산으로 기능화된 것으로, 이로부터 제조된 방사 섬유는 자외선 가교가 가능하며, 유연성이 개선되어, 자외선을 조사함으로써 표면 가교 반응을 유도하고 이를 통해 가속화된 열안정화 과정을 진행함으로써 융착 및 용융 문제가 전혀 없는 탄소 섬유를 단축된 공정 시간 내에 제조할 수 있다.
나노로드 전사방법이 개시된다. 본 발명의 일 실시예에 따른 나노로드 전사방법은, (a) 상부에 중간층이 형성된 기판을 준비하는 단계; (b) 상기 중간층 상에 그래핀층을 형성하는 단계; (c) 상기 그래핀층 상에 이중블록공중합체(diblock copolymer)층을 형성하는 단계; (d) 상기 이중블록공중합체층에 나노로드 패턴을 형성하는 단계; (e) 상기 나노로드 패턴 내에 산화 금속 나노로드를 형성하는 단계; (f) 상기 이중블록공중합체층을 제거하는 단계; (g) 상기 중간층을 식각함으로써 상기 상부에 산화 금속 나노로드가 형성된 그래핀층을 기판과 분리하는 단계; 및 (h) 상기 그래핀층의 하부를 소정의 물질 표면에 부착하는 단계를 포함하는 것을 특징으로 한다.
나노입자가 장식된 그래핀 제조방법이 개시된다. 본 발명의 일 실시예에 따른 나노입자가 장식된 그래핀(10) 제조방법은, (a) 기판(100)을 준비하는 단계; (b) 기판(100) 상에 그래핀층(200)을 형성하는 단계; (c) 그래핀층(200) 상에 블록공중합체 마이셀(310) 및 블록공중합체 마이셀(310)에 도입된 나노입자(320)를 포함하는 블록공중합체 마이셀(block copolymer micelle)층(300)을 형성하는 단계; 및 (d) 나노입자(320)를 포함하는 블록공중합체 마이셀층(3000을 열처리(H)하여 블록공중합체 마이셀층(300)을 제거함으로써 그래핀층(200) 상에 나노입자(320)를 장식하는 단계를 포함하는 것을 특징으로 한다.