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The end-cap removal of carbon nanotubes (CNTs) refers to the structural modification method that makes inner-core spaces and voids between walls accessible. Specifically, the accommodation of alkali metal cations in those hidden surfaces for electrochemical energy storage has been a challenging task. Here we present open-ended vertically aligned CNTs (VA-CNTs) as an ideal structure for Li+ accommodation, which were produced by chemical vapor deposition, followed by CF4 reactive ion etching. A model study suggests a link between Li+ capacity and the surface area, more specifically, allows us to estimate the amount of additional Li+ accommodation, which is 2.3 times increased after end-cap removal. The relatively high capacity (889 mAh/g) has confirmed that open-ended VA-CNTs are highly active for Li+ intercalation as well as exposing interior surfaces, which can be compared to the control (338 mAh/g). The microstructural change observation combined with spectroscopic studies reveals that poor Li+ reversibi...

Pt-based catalysts are suffering from the intrinsic high cost and poor stability for practical use in fuel cells. We develop a free-standing fabric type Pt-free high-performance oxygen reduction reaction (ORR) catalyst, consisting of N, Fe-codoped carbon nanofibers and graphene (N/Fe-CG) hybrids. Electrospinning is used to synthesize the free-standing fabric catalysts. Incorporation of graphene into the nanofiber structure greatly increases the electrical conductivity and catalytic surface area. X-ray photoelectron spectroscopy (XPS) analysis provides evidence that Fe-N4 active centers are possibly formed in the catalyst, as is confirmed by electrochemical tests also. Compared to commercial Pt/C, our N/Fe-CG exhibits a similar level of catalytic activity but superior stability and methanol tolerance in both alkaline and acidic media, making it a good candidate for an ORR electrocatalyst in energy storage/conversion and other relevant applications.

A monovalent sodium-functionalized graphene oxide fiber (Na–GO) structure was synthesized via facile and simple liquid coagulation of a graphene oxide solution. Supported by the stable GO framework, the readily accessible sodium site of this alkali-metal–carbon heterostructure allows effective removal of Cs+ in aqueous medium with a rapid equilibrium time (∼30 min) and a large adsorption capacity (220 mg g−1). Na–GO possesses physical and chemical integrity in a broad pH range (4–10), and the adsorption behavior is influenced by the hydration radius of the targeting cation, charge effect, π–M+ interaction, and pH-dependent GO hydrophilicity. In utilizing the chemical potential effect of Na–GO, a simple regeneration process with NaOH solution selectively releases captured Cs+ and replenishes functional sodium sites within the Na–GO structure, providing a rechargeable Cs+ remediation functionality. This study demonstrates the successful adaptation of the alkali-metal-induced reversible ion-exchange principle for a versatile GO fiber structure.

Customized assembly of nanomaterials into three-dimensional macroscopic objects may offer versatile functional nanostructures. Gelation is a common route to this end, but unstable assembly of typical one-dimensional nanomaterials arising from their non-flat geometry of weakly interacting building blocks has remained a significant challenge. We report versatile reliable open nanoporous graphene nanoribbon hydrogel formation via straightforward interfacial layer-by-layer self-assembly. Atomically flat surface of graphene nanoribbon enables a stable gelation, overcoming the geometrical penalty of one-dimensional building blocks. The resultant hydrogel readily provides compact open porous web-like gel framework along with a wide range of controllability in the engineering of surface functionality, composite preparation and three-dimensional customized morphology formation. Large surface area and open porosity of the synergistic hydrogel structure simultaneously attain fast responsivity and high sensitivity in enzymatic biosensor application as well as fast rate capability and high capacitance in supercapacitor application.

Metal oxide nanoparticles supported on heteroatom-doped graphitic surfaces have been pursued for several decades for a wide spectrum of applications. Despite extensive research on functional metal oxide nanoparticle/doped carbon nanomaterial hybrids, the role of the heteroatom dopant in the hybridization process of doped carbon nanomaterials has been overlooked. Here, the direct growth of MnOx and RuOx nanoparticles in nitrogen (N)-doped sites of carbon nanotubes (NCNTs) is presented. The quaternary nitrogen (NQ) sites of CNTs actively participate in the nucleation and growth of the metal nanoparticles. The evenly distributed NQ nucleation sites mediate the generation of uniformly dispersed &lt, 10 nm diameter MnOx and RuOx nanoparticles, directly decorated on NCNT surfaces. The electrochemical performance of the resultant hybridized materials was evaluated using cyclic voltammetry. This novel hybridization method using the dopant-mediated nucleation and growth of metal oxides suggests ways that heteroatom dopants can be utilized to optimize the structure, interface and corresponding properties of graphitic carbon-based hybrid materials.

An effective pathway to build macroscopic scale functional architectures bearing diverse structural dimensions is one of the critical challenges in the two-dimensional (2D) MXene research area. Unfortunately, assembling MXene without adhesive binder is largely limited due to its innate brittle nature and the relatively weak inter-flake van der Waals contact, in contrast to other mechanically compliant 2D materials such as graphene. Herein, an electrochemical self-assembly of pure Ti

Hybridization of low-dimensional components with diverse geometrical dimensions should offer an opportunity for the discovery of synergistic nanocomposite structures. In this regard, how to establish a reliable interfacial interaction is the key requirement for the successful integration of geometrically different components. Here, we present 1D/2D heterodimensional hybrids via dopant induced hybridization of 2D Ti

Nanoscale engineering of carbon materials is immensely demanded in various scientific areas. We present highly ordered nitrogen-doped carbon nanowire arrays via block copolymer (BCP) self-assembly under an electric field. Large dielectric constant difference between distinct polymer blocks offers rapid alignment of PMMA-b-PAN self-assembled nanodomains under an electric field. Lithographic patterning of the graphene electrode as well as straightforward thermal carbonization of the PAN block creates well-aligned carbon nanowire device structures. Diverse carbon nanopatterns including radial and curved arrays can be readily assembled by the modification of electrode shapes. Our carbon nanopatterns bear a nitrogen content over 26%, highly desirable for NO2 sensing, as the nitrogen element acts as adsorption sites for NO2 molecules. Aligned carbon nanowire arrays exhibits a 6-fold enhancement of NO2 sensitivity from a randomly aligned counterpart. Taking advantage of well-established benefits from device-oriented BCP nanopatterning, our approach proposes a viable route to highly ordered carbon nanostructures compatible to next-generation device architectures.

Unzipping of the basal plane offers a valuable pathway to uniquely control the material chemistry of 2D structures. Nonetheless, reliable unzipping has been reported only for graphene and phosphorene thus far. The single elemental nature of those materials allows a straightforward understanding of the chemical reaction and property modulation involved with such geometric transformations. Here we report spontaneous linear ordered unzipping of bi-elemental 2D MX2 transition metal chalcogenides as a general route to synthesize 1D nanoribbon structures. The strained metallic phase (1T′) of MX2 undergoes highly specific longitudinal unzipping owing to the self-linearized oxygenation at chalcogenides. Stable dispersions of 1T′ MoS2 nanoribbons with widths of 10–120 nm and lengths up to ~4 µm are produced in water. Edge abundant 1T′ MoS2 nanoribbons reveal the hidden potential of idealized electrocatalysis for hydrogen evolution reactions at a competitive level with the precious Pt catalyst., Reliable unzipping of the basal plane of mono-elemental graphene and phosphorene has only been reported thus far. Here, the authors demonstrate the unzipping of bi-elemental 2D MX2 transition metal chalcogenides as a general route to synthesize 1D nanoribbon structures.

Two-dimensional (2D) MXene has shown enormous potential in scientific fields, including energy storage and electromagnetic interference (EMI) shielding. Unfortunately, MXene-based material structures generally suffer from mechanical fragility and vulnerability to oxidation. Herein, mussel-inspired dopamine successfully addresses those weaknesses by improving interflake interaction and ordering in MXene assembled films. Dopamine undergoes

Passive component-based soft resonators have been spotlighted in the field of wearable and implantable devices due to their remote operation capability and tunable properties. As the output signal of the resonator-based wireless communication device is given in the form of a vector (

Graphite is ubiquitous as the anode material in lithium-ion batteries, but offers relatively low volumetric capacity (330 to 430 mAh cm-3). By contrast, Tellurene (Te) is expected to alloy with alkali metals with high volumetric capacity (~2620 mAh cm-3), but to date there is no detailed study on its alloying behavior. In this work, we have investigated the alloying response of a range of alkali metals (A = Li, Na or K) with few-layer Te. In-situ transmission electron microscopy and density functional theory both indicate that Te alloys with alkali metals forming A2Te. However, the crystalline order of alloyed products varied significantly from single-crystal (for Li2Te) to polycrystalline (for Na2Te and K2Te). It is well established that typical alloying materials (e.g., silicon, tin, black phosphorous) lose their crystallinity when reacted with Li. The ability of Te to retain its crystallinity is therefore surprising. Nudged elastic band calculations and ab-initio molecular dynamics simulations reveal that compared to Na or K, the migration of Li is highly “isotropic” in Te, enabling its crystallinity to be preserved. Such isotropic Li transport is made possible by Te’s peculiar structure comprised of chiral chains bound by van der Waals forces. To evaluate the electrochemical performance of Te, we tested Te electrodes in half-cells vs Li/Na/K metal. While alloying with Na and K showed poor performance, with Li, the Te electrode exhibited a volumetric capacity of ~700 mAh cm-3, which is about two-times the practical capacity of commercial graphite. Such Te based batteries could play an important role in applications where high volumetric energy and power density are of paramount importance.

Organic-inorganic hybrid solid electrolytes (HSEs) are expected to overcome the inherent limitations of rigid fragile inorganic electrolytes for solid state batteries. Li-ion conductive filler such as garnet Li7La3Zr2O12 (LLZO) is proposed for the high performance of HSEs, unfortunately, which suffers from native surface layer resistance to Li-ion transport. Here we present highly conductive polyvinylidene fluoride (PVDF)-based HSEs incorporating LLZO fillers, whose resistive barriers are eliminated by dry etching. Our optimal composition of etched LLZO fillers (30 wt%) leads to ionic conductivity of 4.05 x 10-4 S cm-1, about two-fold improvement from non-etched counterpart. Li symmetric cells with etched fillers exhibit low interfacial resistance of 110 Ω cm2 and minimal overpotential of 46 mV. Moreover, high capacity of 79 mA h g-1 is highlighted at 4C, comparable or superior to liquid electrolyte or sulfide-based electrolyte devices. Interfacial environment in HSEs ideally modified for Li-ion transport is identified by 7Li NMR measurements.

2D black phosphorus (BP) and MXenes have triggered enormous research interest in catalysis, energy storage, and chemical sensing. Unfortunately, the low stability of these materials under practical operating conditions remains a critical bottleneck, particularly as they are prone to oxidization under moisture. In this work, the design and application of stable 2D heterostructures obtained from decorating BP and MXene (Ti3 C2 Tx ) with few-layer holey graphene oxide (FHGO) membranes are presented. In the resulting heterostructured systems, FHGO serves as a multifunctional passivation layer that shields BP or MXene from oxidative degradation, while allowing the selective diffusion of target gas molecules through its micropores and toward the underlying 2D material. Through a case study of dilute NO2 sensing, it is demonstrated that these heterostructures show a greatly enhanced sensing performance under humid conditions, where fast sensing speed and response are consistently observed, and high stability is impressively retained upon repetitive sensing cycles for 1000 min. These results corroborate the efficacy of material decoration with porous FHGO membranes and suggest that this is a generalizable strategy for reliable high-performance applications of 2D materials.

Graphene and graphene-based systems have recently been recognized as promising platforms for energy harvesting, microelectronic components and energy storage owing to their excellent electrical and thermal conductivity, outstanding mechanical properties, good chemical stability, area adaptability, among other significant properties. Integration of energy harvesting systems relying on the graphene/graphene-based materials in contact with fluids has been emphasized in recent years, as well as their potential impact on electric energy generation for a wide range of applications (e.g. innovative medical devices, advanced electronic systems and highly-efficient transduction systems for renewable energy). This review summarizes, for the first time, major breakthroughs carried out in the scope of energy harvesting exploiting graphene-based material systems (comprising graphene films, graphene grids, graphene membranes, 3D graphene composites and tribological structures) in contact with ionic and non-ionic fluids. Several transduction mechanisms for energy harvesting have been thoroughly analyzed. Energy outputs, materials and structures, substrates, types of fluid, manufacture methodologies, and experimental test methodologies are systematically highlighted in this review. Finally, future research directions and innovative applications of these harvesters are proposed.

Graphene oxide liquid crystallinity (GO LC) has been widely exploited for high-performance graphene-based applications. In this regard, colloidal stability of GO LC suspension is a crucial requirement, particularly while polymers are often added to the GO LC. Unfortunately, current level of knowledge on how polymers influence the structure and properties of GO LC is not sufficient to systematically guide the development of applications. Here, we investigate the microstructure and rheological properties of GO LC suspensions in the presence of polymer additives with varying molecular weights and concentrations. Similar to conventional colloidal systems, non-negligible polymer-induced interactions are found in GO LC suspensions, which can effectively modulate the interaction among GO platelets and the relevant physical properties. On the basis of extensive small-angle X-ray scattering and rheological measurements, we demonstrate that, contrary to the general perception, polymer-induced depletion attraction can increase the colloidal stability of GO, while also preventing the vitrification of GO LC. In addition, a proper level of polymer additive can reduce the viscosity of GO LC suspensions by orders of magnitude, providing an effective route to GO LC-based solution processing. After all, the colloidal stability and rheological properties of GO can significantly impact the quality of GO. Therefore, we believe that our finding will be of great interest in the field of graphene-based applications, as it presents effective strategies for improving properties.

This paper reports photoexcitation-enhanced magnetization in γFe2O3–graphene (zero dimensional–two dimensional) van der Waals heterostructure based on the experimental studies of steady-state pump–probe measurements in magnetic field. It is observed that applying a magnetic field on the γ-Fe2O3/graphene material suspended in an organic solvent can cause a light scattering on the probe beam in the absence of pump beam, leading to a magnetic field effect of light scattering. This result shows that the magnetization on the γ-Fe2O3 nanoparticles can lead to a partial orientation of Fe2O3–graphene heterostructure components suspended in liquid. This effect of magnetic field on light scattering is caused by the dynamic magnetization of the superparamagnetic–semiconducting hybrid material. Interestingly, applying the pump beam functioning as photoexcitation can lead to an enhancement on the scattering of probe beam, increasing magnetic field effect of light scattering. The increased magnetic field effect of ligh...

Laser photothermal annealing is emerging as a promising strategy for directed self-assembly of block copolymers along with its unique advantages, such as area selectivity, solvent-free ultrafast process, and highly oriented nanopattern formation without substrate prepatterning. We investigate laser-induced highly aligned lamellar and cylindrical self-assembled nanostructure formation by means of simulation as well as experiment. Self-assembled surface-perpendicular lamellar or surface-parallel cylindrical nanodomains in PS-b-PMMA thin films could be aligned by lateral steady scan of focused laser irradiation to attain excellent long-range order over 10 μm length scale. For the systematic understanding of the experimental observation, quasi-static simulation employing successive self-consistent field theory calculation has been developed. Miniaturized simulations of experimental systems could confirm a strong tendency for lamellar domains to grow in the direction of laser scanning. Cylindrical self-assembl...

Owing to unique potential for high color purity luminance based on low-cost solution processes, organic/inorganic hybrid perovskite light-emitting diodes (PeLEDs) are attracting a great deal of research attention. For high performance PeLEDs, optimum control of the perovskite film morphology is a critical parameter. Here, we introduce a reliable and well-controllable PeLED crystallization process based on beam-damage-free near-infrared laser (λ = 808 nm) irradiation. Morphology of the CH3NH3PbBr3 films can be precisely controlled by laser irradiation condition parameters: power density and beam scan rate. We systematically investigate the perovskite film morphology and device performance of the PeLEDs under different processing conditions. In the optimum power density and high beam scan rate (30 W cm–2, 0.1 mm s–1), a dense and smooth perovskite film is attained with a small crystal grain size. The critical relationship between the crystal grain size and LED efficiency is established while attaining the d...

Transparent conducting electrodes (TCEs) are essential components in various optoelectronic devices. Nanostructured metallic thin film is one of the promising candidates to complement current metal oxide films, such as ITO, where high cost rare earth elements have been a longstanding issue. Herein, we present that multiscale porous metal nanomesh thin films prepared by bimodal self-assembly of block copolymer (BCP)/homopolymer blends may offer a new opportunity for TCE. This hierarchical concurrent self-assembly consists of macrophase separation between BCP and homopolymer as well as microphase separation of BCP, and thus provides a straightforward spontaneous production of a highly porous multiscale pattern over an arbitrary large area. Employing a conventional pattern transfer process, we successfully demonstrated a multiscale highly porous metallic thin film with reasonable optical transparency, electro-conductance, and large-area uniformity, taking advantage of low loss light penetration through microscale pores and significant suppression of light reflection at the nanoporous structures. This well-defined controllable bimodal self-assembly can offer valuable opportunities for many different applications, including optoelectronics, energy harvesting, and membranes.

Rational design of nanoscale structures can greatly strengthen heterogeneous catalysis with the maximal utilization of active sites. Single atom catalysts (SACs) are recently emerging but a systematic design of nanostructured SAC has rarely been demonstrated yet. Here, distinct architectural structure-dependence of electrochemical CO2 reduction (CO2RR) on Ni-based SACs is presented. Starting from Ni-imidazolate coordination polymers (Ni-Im) and their supported counterparts with a carbon nanotube (CNT) and a zeolite imidazolate framework (ZIF-8), the respective derivatives, i.e. Ni-SAC, Ni-SAC-CNT, and Ni-SAC-ZIF8, are obtained after pyrolysis. The presence of substrates ultimately results in large surface porous N-doped carbon nanostructures, which facilitate the diffusion of etchants to remove undesired Ni nanoparticles effectively. The dense Ni single atomic sites contained within the nanostructure are easily accessible to CO2 reactants during CO2RR, thus promoting high utilization of active sites even at large current densities. Electro-conductive CNT substrates mediate fluent charge transfer and stimulates the intrinsic activity of catalytic sites. Consequently, operating at 400 mA cm−2, Ni-SAC-CNT attains a high faradaic efficiency of 99% toward CO at a low overpotential of 0.24 V, equivalent to a record cathodic energetic efficiency and turnover frequency of 83.4% and 439,000 h−1, respectively.

3D printing of fiber‐reinforced composites is expected to be the forefront technology for the next‐generation high‐strength, high‐toughness, and lightweight structural materials. The intrinsic architecture of 3D‐printed composites closely represents biomimetic micro/macrofibril‐like hierarchical structure composed of intermediate filament assembly among the micron‐sized reinforcing fibers, and thus contributes to a novel mechanism to simultaneously improve mechanical properties and structural features. Notably, it is found that an interfacial heterogeneity between numerous inner interfaces in the hierarchical structure enables an exceptional increase in the toughness of composites. The strong interfacial adhesion between the fibers and matrix, with accompanying the inherently weak interfacial adhesion between intermediate filaments and the resultant interfacial voids, provide a close representation of the toughness behavior of natural architectures relying on the localized heterogeneity. Given the critical embedment length of fiber reinforcement, extraordinary improvement has been attained not only in the strength but also in toughness taking advantage of the synergy effect from the aforementioned nature‐inspired features. Indeed, the addition of a small amount of short fiber to the brittle bio‐filaments results in a noticeable increase of more than 200% in the tensile strength and modulus with further elongation increment. This article highlights the inherent structural hierarchy of 3D‐printed composites and the relevant sophisticated mechanism for anomalous mechanical reinforcement., Here, the authors present that the intrinsic architecture of 3D‐printed composites closely represents biomimetic hierarchical structure composed of intermediate filament assembly among the reinforcing fibers, and thus contribute to a novel mechanism to simultaneously improve mechanical properties and structural features. Notably, the authors find that an interfacial heterogeneity between numerous inner interfaces in the hierarchical structure enables an exceptional increase in the toughness of composites.

Omnidirectional deformability is an unavoidable basic requirement for wearable devices to accommodate human daily motion particularly at human joints. We demonstrate omnidirectionally bendable and stretchable textile-based electrochemical capacitor that retains high power performance under complex mechanical deformation. Judicious synergistic hybrid structure of woven elastic polymer yarns with carbon nanotubes and conductive polymers offers reliable electrical and electrochemical activity even under repeated cycles of severe complex deformation modes. The textile-based electrochemical capacitors exhibit omnidirectional stretchability with 93% of capacitance retention under repeated 50% omnidirectional stretching condition while demonstrating excellent specific capacitance (412 mF cm-2) and cycle stability (>2000 stretch). The wearable power source stably powers red LED under omnidirectional stretching that accompanies human elbow joint motion.

We report graphene@polymer core-shell fibers (G@PFs) composed of N and Cu codoped porous graphene fiber cores uniformly coated with semiconducting polymer shell layers with superb electrochemical characteristics. Aqueous/organic interface-confined polymerization method produced robust highly crystalline uniform semiconducting polymer shells with high electrical conductivity and redox activity. When the resultant core-shell fibers are utilized for fiber supercapacitor application, high areal/volume capacitance and energy densities are attained along with long-term cycle stability. Desirable combination of mechanical flexibility, electrochemical properties, and facile process scalability makes our G@PFs particularly promising for portable and wearable electronics.

Liquid phase exfoliation (LPE) is a promising method for graphene production particularly in terms of cost effectiveness and scale up. Nonetheless, it is still challenging to synchronize prime goals of high quality, good yield, large sheet size, stable long term storage and low cost eco-friendly processing. We present a simple and inexpensive green route for large scale production of exfoliated graphene dispersions exploiting the non-covalent surface chemistry between graphene and perylene tetracarboxylate (PTCA) aromatic semiconducting surfactant. Direct sonication of graphite flakes in aqueous PTCA solutions produced high yield of single and few-layer graphene sheets with minimal basal plane defects as revealed by XPS, Raman and FTIR spectroscopy. Uniquely for LPE protocol, the lateral graphene flake dimensions extended upto 10–12 μm range. The exfoliated dispersions exhibited high colloidal stability with shelf-life exceeding a year. Facile re-dispersibility of the dried graphene/PTCA powders was observed in water as well as many polar organic solvents. Significantly, pure aromatic semiconducting nature of surfactant without dielectric moiety ensures tight electrical contact among graphene sheets in thin films. The approach exploiting the simple molecular design of aromatic charged surfactants for graphene exfoliation holds a great prospect for solution processed graphene based nanomaterials and devices.

We present high performance multilayer organic/inorganic nanostructured dielectric films including well dispersed chemically modified graphene (CMG) charge polarization layers based on single step solution self-assembly. Multilayer film structures of alternating aluminosilicate and amphiphilic block copolymer (BCP) lamellar layers intercalated with CMG in the hydrophilic aluminosilicate domains are prepared by simple solution casting process. The resultant composite dielectric film attains a high dielectric constant (∼30) along with low dielectric loss (

The development of solar energy conversion in the production of fuels, water splitting and water purification systems, has become an important sidestep for traditional fossil energy. Herein we have investigated the coupling effect of a Photo-Fenton system on a conventional photocatalytic reaction with a novel Fe-doped C 3 N 4 /WO 3 hybrid structure. The decomposition of p -nitrophenol was selected as a model reaction in the context of the degradation of organic pollutants. Heterojunction nanocomposites consisting of g-C 3 N 4 nanosheets and WO 3 nanoparticles were shown to facilitate the separation of photo-induced electron and hole pairs. The photocatalytic activity was further maximized as a result of a synergism of the ‘Photo-Fenton cycle’ with Fe(II) or Fe(III)-doping in the presence of H 2 O 2 to generate additional hydroxyl radicals. As a result, after 4 h under visible light the degradation of p -nitrophenol could be remarkably enhanced from 10 to 90% compared to the g-C 3 N 4 reference. To the best of our knowledge, this is the first time such a striking increase is reported with a Photo-Fenton system applied in the present photocatalytic system. The significance of the presence of hydroxyl radicals in the photo-Fenton performance of Fe-doped C 3 N 4 /WO 3 was assessed by scavenger and fluorescence tests. Additional light was shed into the reaction mechanism via spin trapping enabled by in-situ electron paramagnetic resonance.

The attachment of flexible spacers into aromatic polymers is a molecular design approach that is used for improving processability of aromatic polymers. The concept is attractive because it enables not only the creation of aromatic polymers with improved processability but it is also possible to control phase morphology by simply introducing pendant side chains. Here we report new bisphenol A derivatives bearing alkyl chains of different lengths obtained by an addition reaction can readily make novel poly(arylene sulfone)s with aromatic dihalides and aromatic dioles. They were observed using two-dimension diffusion-ordered spectroscopy nuclear magnetic resonance (2D DOSY NMR) spectra. Attaching flexible alkyl groups into sulfonated poly(arylene sulfone)s allows for increased control of glass transition temperatures, T g , of sulfonated poly(arylene sulfone)s. The alkylated sulfonated poly(arylene sulfone)s had flexibility, increased surface contact angle, improved methanol permeability, and high ion conductivity compared to the neat polymer. Due to the creation of aromatic polymers with improved processability by simply introducing pedant side chains, this novel alkylation method is expected to be applicable to other arylene based proton conductive polymers.

We introduce a facile and effective fabrication of complex multimetallic nanostructures through block copolymer self-assembly. Two- and three-dimensional complex nanostructures, such as “nanomesh,” “double-layered nanomeshes,” and “surface parallel cylinders on nanomesh,” can be fabricated using the self-assembly of perforated lamellar morphology in block copolymer thin films. Simultaneous integration of various metallic elements, including Pt, Au, and Co, into the self-assembled morphologies generates multimetal complex nanostructures with highly interconnected morphology and a large surface. The resultant metal nanostructures with a large surface area, robust electrical connectivity, and well-defined alloy composition demonstrate a high-performance electrochemical catalysis for hydrogen evolution reaction (current density: 6.27 mA/cm2@0.1 V and Tafel slope: 43 mV/dec).

Graphene has been intensively adopted into boosting the electrochemical performances of battery electrode materials due to its superior nature. In the case of Li4Ti5O12 (LTO), the application of graphene has been specifically focused on ameliorating the low electronic conductivity of LTO. So far, these attempts aiming to increase the composite's electronic conductivity involved thick graphene layers, which inevitably hindered Li-ion diffusion and eventually harmed the electrochemical kinetics in LTO's surface. In this work, high quality minimum-impurity graphene oxide was prepared by means of thorough cleaning and dialysis, which enabled each single-layered graphene to successfully wrap individual LTO particles. The resulting single-layer graphene-wrapped LTO exhibits an excellent specific capacity of 130 mAh g−1 even at a lithiation/delithiation of 30 C. Such a high rate capability is one of the highest values among the reported LTO with comparable sizes (∼200 nm). To uncover the reasons for such high performance, electrochemical properties from varied graphene contents were juxtaposed for comparison, and as a result, number of graphene layers and the corresponding kinetic parameters were found correlated. With adequate validity, single graphene layer was revealed to be the uttermost optimum for both Li+ diffusion and electronic conduction.

We investigate the unusually rapid directed self-assembly of block copolymer (BCP) thin films by imposing an in-plane electric field. Blending short chain BCPs dramatically enhances the generically retarded chain diffusivity for BCP self-assembly in thin films. In addition, photopatterned, few-layer solution-cast chemically modified graphene is introduced as a disposable and versatile electrode for electric field applications. A variety of laterally ordered self-assembled lamellar BCP nanopatterns are attained within a 10 min time scale, including an arbitrary large-area unidirectionally oriented lamellar array.

Graphene oxides (GOs), an oxygenated derivative of graphene, spontaneously undergo monolayer exfoliation in water, and thus, form liquid crystalline (LC) suspensions. Unfortunately, the resultant suspensions vitrify at around a 1 wt% composition, which commonly acts as an obstacle for GO-based material fabrication, while degrading the molecular ordering and relevant material properties. Here, we systematically investigate the phase behaviour and structural evolution of GO LC suspensions under various experimental conditions and disclose how the glass transition of GO dispersions is affected particularly in the presence of strongly interacting polymers. The supplementary polymer additives can effectively retard the ‘glass transition’ of a GO suspension, broaden the concentration range for a nematic LC phase toward lower and higher concentration ranges and dramatically decrease the viscosity of the suspension down to the 1/100–1/1000 level. Extensive small-angle X-ray scattering and rheological measurements are employed to characterize the molecular level GO structures in LC suspensions.

Efficient water oxidation remains a principal challenge for clean fuels via water splitting. Polyoxometalates (POMs) are promising water oxidation catalysts in a neutral medium but their application is commonly limited by low electrical conductivity and poor adhesiveness arising from bulky and electrically insulating ligands. Here we report linker-free spontaneous binding of tetracobalt-based polyoxometalates (Co4POMs) on nitrogen-doped carbon nanotubes (NCNTs) via electrostatic hybridization. Protonated nitrogen-dopant sites at NCNTs enable linker-free immobilization of the Co4POMs and fluent electron transfer in the resultant Co4POM/NCNT hybrid structures, as demonstrated by the low overpotential of 370 mV for the water oxidation at pH 7. Accordingly, the hybrids exhibit fast reaction kinetics with a turnover frequency of 0.211 s−1 at 2.01 V vs. RHE. Density functional theory calculation proposes that POMs vertically align at the NCNT surface exposing the maximal catalytic surfaces. This work suggests a reliable route to highly efficient water oxidation catalysis by employing POMs under neutral conditions and NCNTs as self-binding nanoelectrodes in a synergistic well-oriented hybrid structure.

The dimensional stability and barrier properties of proton exchange membranes are critical issues for high-performance proton exchange membrane fuel cells (PEMFCs). In this work, we introduce a viable and effective strategy for preparing high proton-conductive polymer membranes with remarkable dimensional stability and barrier properties. Sulfonated poly(arylene sulfone)s (sPASs) with a UV-crosslinkable monomer, 2,2′-diallylbisphenol A (DABPA), is successfully synthesized via condensation polymerization, showing competitive molecular weights and sulfonation degrees to the neat polymer. Crosslinked nanocomposite membranes can be fabricated by incorporating soft bridge molecules and exfoliated LAPONITE® nanofillers, and subsequent UV-crosslinking. The sPAS–LAPONITE® nanocomposite membranes show greatly improved dimensional stabilities and barrier properties including remarkably reduced swelling ratio in solvent or methanol aqueous solutions. These enhanced properties lead to excellent performance in a direct methanol fuel cell (DMFC) test, surpassing that of a commercially available Nafion membrane based devices.

Rational design of 2D materials is crucial for the realization of their profound implications in energy and environmental fields. The past decade has witnessed significant developments in 2D material research, yet a number of critical challenges remain for real-world applications. Nanoscale assembly, precise control over the orientational and positional ordering, and complex interfaces among 2D layers are essential for the continued progress of 2D materials, especially for energy storage and conversion and environmental remediation. Herein, recent progress, the status, future prospects, and challenges associated with nanoscopic assembly of 2D materials are highlighted, specifically targeting energy and environmental applications. Geometric dimensional diversity of 2D material assembly is focused on, based on novel assembly mechanisms, including 1D fibers from the colloidal liquid crystalline phase, 2D films by interfacial tension (Marangoni effect), and 3D nanoarchitecture assembly by electrochemical processes. Relevant critical advantages of 2D material assembly are highlighted for application fields, including secondary batteries, supercapacitors, catalysts, gas sensors, desalination, and water decontamination.

Block copolymer (BCP) lithography is an effective nanopatterning methodology exploiting nanoscale self-assembled periodic patterns in BCP thin films. This approach has a critical limitation for nonplanar substrate geometry arising from the reflow and modification of BCP films upon the thermal or solvent annealing process, which is inevitable to induce the mobility of BCP chains for the self-assembly process. Herein, reflow-free, 3D BCP nanopatterning is demonstrated by introducing a conformally grown adlayer by the initiated chemical vapor deposition (iCVD) process. A highly cross-linked poly(divinylbenzene) layer was deposited directly onto the BCP thin film surface by iCVD, which effectively prevented the reflow of BCP thin film during an annealing process. BCP nanopatterns could be stabilized on various substrate geometry, including a nonplanar deformed polymer substrate, a pyramid shape substrate, and a graphene fiber surface. A fiber-type hydrogen evolution reaction (HER) catalyst is suggested by stabilizing lamellar Pt nanopatterns on severely rough graphene fiber surfaces.

Aqueous Zn-Br batteries (ZBBs) offer promising next-generation high-density energy storage for energy storage systems, along with distinctive cost effectiveness particularly in membraneless and flowless (MLFL) form. Unfortunately, they generally suffer from uncontrolled diffusion of corrosive bromine components, which cause serious self-discharge and capacity fade. An MLFL-ZBB is presented that fundamentally tackles the problem of bromine crossover by converting bromine to the polybromide anion using protonated pyridinic nitrogen doped microporous carbon decorated on graphite felt (NGF). The NGF electrodes efficiently capture bromine and polybromide anions at the abundant protonated nitrogen dopant sites within micropores and facilitate effective conversion of bromine into polybromides through electrochemical-chemical growth mechanism. The MLFL-ZBBs with NGF exhibit an extraordinary stability over 1000 charge/discharge cycles, with an energy efficiency over 80%, the highest value ever reported among membraneless Zn-Br batteries. Judicious engineering of an atomistically designed nanostructured electrode offers a novel design platform for low cost, high voltage, long-life cycle aqueous hybrid Zn-Br batteries.

We present the formation of a nanobelt by self-assembly of β-benzyl GABA (γ-aminobutyric acid). This simple γ-amino acid building block self-assembled to form a well-defined nanobelt in chloroform. The nanobelt showed distinct optical properties due to π-π interactions. This new-generation self-assembled single amino acid may serve as a template for functional nanomaterials.

We report the synthesis of thiopropionic acid-functionalized polymethacrylate-b-polystyrene (PMATA-b-PS) as a template for patterning Ag nanoarrays. Reversible addition-fragmentation chain transfer (RAFT) polymerization of silyl-protected propagyl methacrylate followed by chain extension with styrene produced a block copolymer precursor. Deprotection of the trimethylsilyl group and subsequent thiol-yne reaction afforded the target, PMATA-b-PS. While the entire series of the precursor was in the disordered phase, microphase separated morphologies were identified from PMATA-b-PS, indicating an increased interaction parameter (χ) as a result of introducing the acid groups. As a preliminary result, we show that an Ag nanoparticle array can be fabricated by selectively associating Ag+ ions to the PMATA cylinders in the thin film of PMATA-b-PS and removing the organic polymer layer by oxygen plasma treatment.

Graphitic carbon nitride (g-C3N4) is a rising two-dimensional material possessing intrinsic semiconducting property with unique geometric configuration featuring superimposed heterocyclic sp(2) carbon and nitrogen network, nonplanar layer chain structure, and alternating buckling. The inherent porous structure of heptazine-based g-C3N4 features electron-rich sp(2) nitrogen, which can be exploited as a stable transition metal coordination site. Multiple metal-functionalized g-C3N4 systems have been reported for versatile applications, but local coordination as well as its electronic structure variation upon incoming metal species is not well understood. Here we present detailed bond coordination of divalent iron (Fe(2+)) through micropore sites of graphitic carbon nitride and provide both experimental and computational evidence supporting the aforementioned proposition. In addition, the utilization of electronic structure variation is demonstrated through comparative photocatalytic activities of pristine and Fe-g-C3N4.

With the development of various energy technologies, much interest is focused on the feasibility and efficiency study of energy devices such as fuel cells, batteries, supercapacitors and water electrolysis systems. Among them, polymer electrolyte fuel cell (PEFC), which convert hydrogen into electric energy with zero emission of pollutants, is one of the most promising environmentally friendly technologies. Despite innumerable studies for more than half a century, degradation of the key component, membrane electrode assembly (MEA), is still a big obstacle for the commercialization of PEFC system. For the high performance and long-term stability of Pt/C electrode catalyst, the agglomeration of Pt particles and dissolution or detachment of Pt particles from carbon support have to be improved. For this purpose, we adopted a new shape of nano-carbon material for the surface modification of Pt catalyst. Graphene has been an attractive two-dimensional carbon allotrope having large surface area and electronic conductivity. Graphene also shows high flexibility and mechanical strength so that it can be used for large number of applications such as flexible display or printable electronics, etc [1-2]. In most cases, people need large-area graphene films with little or no defect for high thermal and electronic conductivity. Also, people need to transfer the as-prepared graphene film for each application. All of these processes are not easy or simple, and they are also labor-intensive processes. However, in the case of catalysis, porous graphene films can be synthesized via very simple one-step process and can be used as effective protective layers for Pt catalysts. In this study, we developed porous graphene films in order to improve the long-term stability of Pt catalysts maintaining the high performance of them. The graphene films were synthesized by single-step vaporization process, where the number of graphene layers and the defects in their structure are manipulated by temperature and composition of the precursors. In this process, the amounts of structural defects, pyridine was simultaneously introduced to the vaporization process, which is much easier and cost-effective compared to the conventional NH3-treatment at high temp [3]. Consequently, our Pt/C catalysts coated with porous graphene films showed similar initial activity compared with the commercial catalysts (Pt 40wt%, Johnson Matthey) showing more than 150% higher long-term stability [4]. [1] A.K. Geim and K. S. Novoselov, Nature Mater. 6 (2007) 183. [2] X. L. Li, G. Y. Zhang, X. D. Bai, X. M. Sun, X. R. Wang, E. Wang and H. J. Dai, Nature Nanotech. 3 (2008) 538. [3] Y. Wang, Y. Shao, D. W. Matson, J. Li and Y. Lin, ACS nano 4(4) (2010) 1790. [4] H. Kim, A. Robertson, S. O. Kim, J. M. Kim and J. H. Warner, ACS nano 9(6) (2015) 5947.

Modern flexible consumer electronics require efficient energy storage devices with flexible free-standing electrodes. We report a simple and cost-effective route to a graphene-based composite aerogel encapsulating metal oxide nanoparticles for high energy density, free-standing, binder-free flexible pseudocapacitive electrodes. Hydrothermally synthesized Co3O4 nanoparticles are successfully housed inside the microporous graphene aerogel network during the room temperature interfacial gelation at the Zn surface. The resultant three-dimensional (3D) rGO-Co3O4 composite aerogel shows mesoporous quasiparallel layer stack morphology with a high loading of Co3O4, which offers numerous channels for ion transport and a 3D interconnected network for high electrical conductivity. All solid state asymmetric pseudocapacitors employing the composite aerogel electrodes have demonstrated high areal energy density of 35.92 μWh/cm(2) and power density of 17.79 mW/cm(2) accompanied by excellent cycle life.

Organic-inorganic hybrid perovskites attract enormous research interest for next generation solar energy harvest. Synergistic crystalline structures comprising organic and inorganic components enable solution processing of perovskite films. A reliable crystallization method for perovskites, compatible with fast continuous process over large-area flexible substrates, is crucial for high performance solar cell production. Here, we present laser crystallization of hybrid perovskite solar cells using near-infrared (NIR) laser (λ = 1064 nm). Crystalline morphology of CH3NH3PbI3 (MAPbI3) perovskite films are widely controllable with laser irradiation condition while maintaining film uniformity. Photothermal heating effectively assisted by interfacial photoconversion layers is critical for phase transformation without beam damage of multilayered device structures. Notably, laser crystallization attains higher device performances than conventional thermal annealing. Fast laser crystallization with manufacture level scan rate (1 m min(-1)) demonstrates inverted-type perovskite solar cells with 11.3 and 8.0% efficiencies on typical glass and flexible polymer substrates, respectively, without rigorous device optimization.

Block copolymer lithography exploiting diblock copolymer thin films is promising for scalable manufacture of device-oriented nanostructures. Nonetheless, its intrinsic limitation in the degree of freedom for pattern symmetry within hexagonal dot or parallel line array greatly diminishes the potential application fields. Here, we report multi-level hierarchical self-assembled nanopatterning of diblock copolymers for modified pattern symmetry. Sequential hierarchical integration of two layers of diblock copolymer films with judiciously chosen molecular weights and chemical composition creates nanopatterned morphology with modified pattern symmetry, including sparse linear cylinder or lamellar arrays. Internal structure of the hierarchically patterned morphology is characterized by grazing-incidence small-angle X-ray scattering throughout the film thickness. Pattern transfer of the modified nanopattern generates linear metal nanodot array with uniform size and regular spacing as a typical example of functional nanopatterned structures.

Novel Pt-Co alloyed nanocatalysts are generated via chemical vapor deposition-assisted facile one-pot synthesis. The method guarantees highly monodisperse Pt-Co alloy nanoparticles with precise control of metallic compositions within 1 at%. A significant features is that a perfectly alloyed single-crystal structure is obtained at temperatures as low as 500 °C, which is much lower than conventional alloying temperatures.

In this study, a novel buckled structure of edge-oriented MoS2 films is fabricated for the first time by employing monolayer graphene as the substrate for MoS2 film growth. Compared to typical buckling methods, our technique has several advantages: (1) external forces such as heat and mechanical strain are not applied; (2) uniform and controllable buckling over a large area is possible; and (3) films are able to be transferred to a desired substrate. Dual MoS2 orientation was observed in the buckled film where horizontally aligned MoS2 layers of 7 nm thickness were present near the bottom graphene surface and vertically aligned layers dominated the film toward the outer surface, in which the alignment structure was uniform across the entire film. The catalytic ability of the buckled MoS2 films, measured by performing water-splitting tests in acidic environments, shows a reduced onset potential of -0.2 V versus reversible hydrogen electrode (RHE) compared to -0.32 V versus RHE for pristine MoS2, indicating that the rough surface provided a higher catalytic activity. Our work presents a new method to generate a buckled MoS2 structure, which may be extended to the formation of buckled structures in various 2D materials for future applications.