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Silicon (Si) has attracted considerable attention due to its high theoretical capacity compared to conventional graphite anode materials. However, Si-based anode materials suffer from rapid capacity loss due to mechanical failure caused by large volume change during cycling. To alleviate this phenomenon, crosslinked polymeric binders with strong interactions are highly desirable to ensure the electrode integrity. In this study, thermally crosslinked polyimide binders were used for Si-alloy anodes in Li-ion batteries. The crosslinked polyimide binder was found to have high adhesion strength, resulting in enhanced electrode integrity during cycling. Therefore, the Si-alloy anodes with crosslinked polyimide binder provide enhanced electrochemical performance, such as Coulombic efficiency, capacity retention, and cycle stability.

Current research has focused on effective solutions to mitigate global warming and the accelerating greenhouse gas emissions. Compared to most cooling methods requiring energy and resources, passive daytime radiative cooling (PDRC) technology offers excellent energy savings as it requires no energy consumption. However, existing PDRC materials encounter unprecedented problems such as complex structures, low flexibility, and performance degradation after stretching. Thus, this study reports a porous structured thermoplastic polyurethane (TPU) film with bimodal pores to produce high-efficiency PDRC with efficient solar scattering using a simple process. The TPU film exhibited an adequately high solar reflectivity of 0.93 and an emissivity of 0.90 in the atmospheric window to achieve an ambient cooling of 5.6 °C at midday under a solar intensity of 800 W m

Current research has focused on effective solutions to mitigate global warming and the accelerating greenhouse gas emissions. Compared to most cooling methods requiring energy and resources, passive daytime radiative cooling (PDRC) technology offers excellent energy savings as it requires no energy consumption. However, existing PDRC materials encounter unprecedented problems such as complex structures, low flexibility, and performance degradation after stretching. Thus, this study reports a porous structured thermoplastic polyurethane (TPU) film with bimodal pores to produce high-efficiency PDRC with efficient solar scattering using a simple process. The TPU film exhibited an adequately high solar reflectivity of 0.93 and an emissivity of 0.90 in the atmospheric window to achieve an ambient cooling of 5.6°C at midday under a solar intensity of 800 W/m2. Thus, the highly elastic and flexible TPU film was extremely suitable for application on objects with complex shapes. The radiative cooling performance of 3D-printed models covered with these TPU films demonstrated their superior indoor cooling efficiency compared to commercial white paint (8.76°C). Thus, the proposed design of high-efficiency PDRC materials is applicable in various urban infrastructural objects such as buildings and vehicles.

Oil spill rapidly destroys aquatic system and threatens humans, requiring fast and efficient remedy for removal of oil. The conventional remedy employs water-floating oil adsorbents whose volume should be large enough to accommodate all oil ingredients. Here, we suggest a new concept for efficient oil-spill remediation, which combines solar-driven evaporation of light oil components and simultaneous adsorption of heavy oil components, namely, solar-driven evaporation of oil combined with adsorption (SEOA). To design photothermal oil absorbents for the efficient SEOA, we designed carbonaceous fabrics with high photothermal heating performance and oil-adsorption capacity by carbonizing nonwoven cotton fabrics. For three model organic solvents of octane, decane, and dodecane floating on water, the fabrics, respectively, accelerated the evaporation in factors of 2.0, 4.4, and 2.3 through photothermal heating under simulated sunlight condition. For the 1.18 mm thick crude oil floating on water, 70 and 77 wt % of crude oil were evaporated within 2 and 16 h, respectively, with the photothermal fabrics, whereas only 22 and 34 wt % was evaporated in the absence of the fabrics, indicating the dramatic enhancement of oil removal by solar-driven evaporation. The remaining heavy oil components were accommodated in the pores of the fabrics, removal of which showed an additional 18 wt % reduction; that is, a total 95 wt % of the crude oil was removed. The oil-treatment capacity is as high as 110 g g-1, which has never been achieved with conventional oil adsorbents to the best of our knowledge. We believe that our combinatorial SEOA approach potentially contributes to minimizing the environmental disaster through a fast and efficient oil-spill remediation.

To develop highly sensitive updatable hologram materials, an azobenzene monomer was synthesized herein that supports effective photoisomerization under visible green beam irradiation. Furthermore, an acetylene group was introduced via Sonogashira coupling for higher birefringence. Polymerization was performed on the synthesized azobenzene monomer and on the methyl methacrylate (MMA) monomer, which serves as the skeleton of the film. The structures of all molecules were characterized by nuclear magnetic resonance (NMR) spectroscopy, and UV-Visible absorption spectroscopy was performed to analyze their optical properties. The holographic writing and rewriting capabilities of the newly synthesized azobenzene side-chain polymer were characterized by using a green laser as a writing beam, which showed that a high diffraction efficiency was reliably achievable under low-energy laser irradiation when evaluated with a four-wave-mixing optical scheme. In this study, high birefringent acetylene group containing azobenzene-based polymers were synthesized as materials for rewritable green-laser holograms, and their properties were evaluated. Birefringence change of polymer, which has an absorption wavelength suitable for green laser (532 nm), is 0.018. The diffraction efficiency of polymer was 72% under low-energy irradiation (7 J/cm2). These results show that the hologram recording material made in this study with high birefringent azobenzene are stable, without undergoing decomposition even when repeated recording and rewriting were performed.

Morphology control of a graphene nanosheet (GNS) is important for graphene-based battery electrodes to exhibit the increased practical surface area and the enhanced ion diffusion into the nanosheets. Nevertheless, it is very difficult to minutely control the shape of graphene nanosheets based on the conventional GNS suspension methods. In this work, we fabricated wrinkle textures of free-standing GNS for large area using Langmuir–Schaefer technique. The wrinkles are oriented vertically to the direction of the monolayer compression. The textured structure of GNS was obtained by cross-deposition of each layer with controlling the orientation of the wrinkle direction. These wrinkles can cause Li-ion to diffuse into the voids created by them and raise the specific surface area between the GNSs. Consequently, as a prospective anode for Li-ion battery, the wrinkled GNS multilayer, exhibits the high specific capacity of ~ 740 mAh g−1 at 100 mA g−1 and the great power capability with ~ 404 mAh g−1 being delivered even at 2 A g−1. Furthermore, outstanding cycle performance of the wrinkled GNS multilayer is achieved over 200 cycles at 300 mA g−1 with high Coulombic efficiency of ~ 96%.

In this study, we developed a facile and template-free strategy for the preparation of activated porous carbon beads (APCBs) from polyacrylonitrile. The chemical activation with KOH was found to enhance the pore properties, such as specific surface area (SSA), pore volume, and pore area. The APCBs exhibited a large SSA of 1147.99 m2/g and a pore area of 131.73 m2/g. The APCB-based electrodes showed a good specific capacitance of 112 F/g at 1 A/g in a 6 M KOH electrolyte, and excellent capacitance retention of 100% at a current density of 5 A/g after 1000 cycles. Therefore, the APCBs prepared in this study can be applied as electrode materials for electric double-layer capacitors.

An eco-friendly method for the preparation of porous carbon monoliths (PCMs) with a high surface area and excellent electrochemical performance was demonstrated. Porous carboxymethyl cellulose monoliths (CMCMs) were prepared by ice-templating technique. PCMs were fabricated by the carbonization of ice-templated porous CMCMs. The prepared PCMs exhibited a high specific surface area of 724.35 m2 g–1 with multi-modal pore structures. The PCM-based electrode showed a high specific capacitance of 210 F g–1 at 1 A g–1 in a 6.0 M KOH electrolyte, and an excellent cycle stability of almost 100% at 10 A g–1 after 10,000 cycles. Therefore, the PCMs prepared in this study are a promising electrode material for high-performance supercapacitors.

Hexagonally-arranged porous carbon films (HaPCFs) were prepared by proton beam irradiation and carbonization of hexagonally-arranged porous polystyrene films (HaPPSFs). HaPPSFs prepared by an improved phase separation method were irradiated with 150-keV proton beam at a fluence of 4 × 1016 ions cm−2 to enhance the thermal stability for high-temperature carbonization. Proton beam irradiation of HaPPSFs was found to induce crosslinking and surface oxidation reactions. The proton beam-irradiated HaPPSFs were carbonized at 800 °C under an inert atmosphere, resulting in the formation of HaPCFs. The prepared HaPCFs were found to have pseudo-graphitic structures containing both ordered and disordered graphitic structures. The prepared HaPCFs showed a good electrical conductivity.

In this study, the fabrication of a wettability patterned surface for cellular micropatterning was investigated using step-wise ion beam processing. A perfluorinated poly(ethylene-co-propylene) (FEP) film was first irradiated using accelerated Xe+ ions with 100 keV of energy at the low current density of 1 μA/cm² over the entire surface. Second, its confined regions were irradiated at the higher current density of 15 μA/cm² at various ion fluences through the pattern mask to generate patterns with big differences in wettability. From the analytic results, it was clearly verified that the step-wise irradiation induced effective chemical and morphological changes on the FEP surface, resulting in the successful formation of well-defined micropatterns with relatively hydrophilic and superhydrophobic surfaces. Moreover, the results of in-vitro cell culture showed well-resolved formation of 200 μm cell micropatterns on the wettability patterned FEP surface due to the individual effects of the relatively hydrophilic and superhydrophobic properties on the cell adhesiveness and proliferation.

We present a simple and facile approach to creating asymmetrically modified graphene oxide sheets by grafting polymers with different polarities. Single-layered Janus graphene derivatives were prep...

Using a simple and facile method, we precisely controlled the two-dimensional layered array structure of graphene oxide (GO)–iron oxide (Fe3O4) nanoparticle hybrid multilayer films and investigated the correlation between the assembled structure of the hybrid films and their magnetic properties. GO–Fe3O4 nanoparticle hybrids were obtained via the ligand exchange of oleic acid-functionalized Fe3O4 nanoparticles with GO at the gas–liquid interface. Hybrids of oriented Fe3O4 nanoparticles and GO monolayers spontaneously formed at the gas–liquid interface, which were subsequently deposited on solid substrates using the Langmuir–Schaefer (LS) technique. Two-dimensional superlattices of GO–Fe3O4 nanoparticle hybrids were fabricated through repeated LS deposition of the nanoparticle monolayer with a hexagonal array structure sandwiched between GO monolayers. The magnetic properties of the GO–Fe3O4 multilayer were measured using SQUID magnetometry. From the field cooling/zero field cooling results, we found that the 2D superlattice-like layered structure of the GO–Fe3O4 multilayer facilitates the layer-dependent properties in the out-of-plane field case due to the dipolar interactions between the top and bottom layers.

Background We investigated whether electrical stimulation via indium tin oxide (ITO) could enhance the in vitro culture of neonatal rat ventricular myocytes (NRVMs), which are important in vitro models for studying the mechanisms underlying many aspects of cardiology. Methods Cardiomyocytes were obtained from 1-day-old neonatal rat heart ventricles. To evaluate function of NRVMs cultured on ITO with electrical stimulation, the cell viability, change of cell morphology, immunochemistry using cardiac-specific antibodies, and gene expression were tested. Results Defined sarcomeric structure, cell enlargement, and increased distribution of NRVMs appeared in the presence of electrical stimulation. These characteristics were absent in NRVMs cultured under standard culture conditions. In addition, the expression levels of cardiomyocyte-specific and ion channel markers were higher in NRVMs seeded on ITO-coated dishes than in the control group at 14 days after seeding. ITO-coated dishes could effectively provide electrical cues to support the in vitro culture of NRVMs. Conclusions These results provide supporting evidence that electrical stimulation via ITO can be effectively used to maintain culture and enhance function of cardiomyocytes in vitro.

Additional file 1: Supplementary 1. Table S1. List of primers used in qRT-PCR

Cell microarray bioplatform have been widely developed for fundamental and advanced biomedical research. However, it is still difficult to achieve site-specific adhesion due to the weak cell repellency of the background regions. Here, a microwell bioplatform with a strong cell-repellent background was newly developed by a sequential ion beam irradiation-induced anchoring and re-irradiation-induced erosion microstructuring of PF-108 thin film on a tissue culture polystyrene (TCPS) substrate. The newly developed bioplatform possesses outstanding optical transparency and well-defined microwells in a variety of sizes and shapes. Its microwells also show cell-adhesiveness (as much as that on the TCPS) with excellent cell-repellency (no cell growth) on the anchored PF-108 film background. As a result, the live-cell culturing of different strains on the developed bioplatform produced two highly resolved cell microarrays (possessing the diverse sizes and shapes corresponding to those of the bioplatform) with a non-specific adhesion-free background. Moreover, different whole-slide GFP and dsRED protein expressions without a non-specific binding background were successfully achieved in the cell microarray. Noticeably, our finding demonstrates that this toxic chemical-free and biocompatible strategy using ion beam-induced solid-state microstructuring provides a non-specific binding-free microwell bioplatform for use in a highly resolved cell microarray for the practical gene expression assay.

In this study, the development of electrically-heatable carbon thin films (CTFs) from water-soluble poly(vinyl alcohol) (PVA) is described. CTFs are easily obtained by room-temperature and solid-state proton irradiation-induced stabilization of PVA thin films followed by carbonization at a high temperature. The results of the chemical, optical, and structural analyses reveal that polyene-network structures, enabling high-temperature dimensional stability, are effectively created in the PVA thin films by combined reactions of crosslinking and dehydration during proton irradiation; these structures are further converted to pseudo-graphitic CTFs by carbonization. The prepared CTFs exhibit the fluence and thickness-dependent electrical conductivity ranging from 0.8 × 102 to 2.63 × 102 S cm−1, and a very low surface roughness of below 0.41 nm. Moreover, the prepared CTFs show excellent electric-heating characteristics and the performance is clearly dependent on the thickness and fluence. The CTFs prepared in this study have good potential for application in the fabrication of automobiles, smart windows, and medical devices for deicing, defrosting, and warming.

The effects of an immiscible, lubricating polydimethylsiloxane fluid, referred to as silicone oil, on the static deformation and on the dynamic motion of a water drop on paper induced by electrowetting were investigated. The deformation of a drop on a hydrophobic film of amorphous fluoropolymers top-coated with less hydrophobic silicone oil was much more predictable, reversible and reproducible than on the uncoated surface. In the dynamic tribological experiment for a sliding drop along an inclined surface, a significant decrease in the friction coefficient, with an unexpected dependency of the contact area, was observed. Based on the curve fitting analysis, the shear stress and the net friction force were estimated quantitatively. Because of the tribological effect and the reduced shear friction force of the oil film, the static and the dynamic electrowetting states of the water drop were enhanced.

In this study, thin carbon films with good electrical properties were prepared using commercial novolac resins by ion beam irradiation and carbonization. Novolac films were irradiated with ion beams and then carbonized under inert atmosphere. Based on the FTIR and UV results, the novolac resins were found to be crosslinked by ion beam irradiation without any additives. The Raman and XRD results indicate that carbon films with pseudo-graphitic structures were formed by carbonization of the ion beam irradiated novolac films. The sheet resistance of the prepared carbon films decreased to 1.35 × 102 Ω/ with an increasing fluence. The prepared carbon films showed a good electrical conductivity of ∼2.34 × 102 S/cm.

In this work, we demonstrated that carbon nanosheet (CNS) can easily be produced by a room-temperature, solid-state proton irradiation-induced clustering of poly(vinyl chloride) (PVC) films followed by carbonization. The results of the optical, chemical, and structural analyses revealed that oxidized and sp2-hybridized carbon clusters were effectively created in the PVC thin film by combined dehydrochlorination and inter-coupling reactions during proton irradiation. This was further converted to pseudo-hexagonally-structured nano-crystalline CNS with 2-D symmetry and metallic transporting character by high-temperature treatment. As a result, the CNS exhibited a very high electrical conductivity (587 S/cm) without a significant change in their thickness, a low surface roughness (0.36 nm), and a high work function (5.11 eV). These findings demonstrate that the radiation-based approach opens new avenues for the design and development of 2-D CNS as a graphene allotrope for the application of electronic devices, including field-effect transistors, electric heating devices, biosensors, supercapacitors, and fuel cells.

Electrically-conductive carbon films were prepared by the thermal treatment of polyacrylonitrile/graphene oxide (PAN/GO) composite films. PAN/GO composite films spin-coated on substrates were stabilized in air and then carbonized under inert atmosphere at 1000 °C to form carbon films. It was found that the cyclization of PAN and the partial reduction of GO occurred simultaneously during stabilization. The incorporation of GO was found to help to lower the energy and temperature of cyclization by an additional ionic reaction mechanism and to form large and compact crystalline structures. The electrical conductivity increased to 5.92 × 102 S/cm with an increasing GO content.

Direct spinning of carbon nanotube (CNT) fibers is a facile method to produce CNT fibers because of its high productivity and the simplicity of the spinning process from CNT aerogels. Directly spun CNT fibers, however, generally include amorphous carbon and weak shear interaction between tubes or bundles, thereby causing insufficient load transfer. Here, we report newly designed polyimide/reduced graphene oxide (PI/RGO)/CNT fiber composites in combination with polymer infiltration followed by photonic flash sintering on a time scale of 0.5 ms to overcome the critical drawbacks in directly spun CNT fibers. The mechanical performances of the CNT fibers were closely related to the junction strength in CNT bundles. In addition, PI can be interlocked with CNT bundles and effectively serve as a binder to link the GO and CNT fibers with strong interfacial interactions. The PI infiltrated CNT fibers showed the highest load transfer, resulting in a significantly enhanced increase of 83% in specific strength (1.1 N/tex) and a 477% increase in tensile strength (800 MPa) compared to pristine CNT fibers. Furthermore, the photonic sintered PI/RGO/CNT fibers improved electrical conductivity by over 244% (5.5 × 103 S cm−1) over pristine CNT fibers without deteriorating mechanical properties. The results demonstrate that the mechanical strength, modulus and electrical conductivity can be enhanced simultaneously by molecular-level coupling of polymer/graphene with CNT fibers via photonic flash sintering.

Porous carbon films (PCFs) are widely used in various application fields, such as separation and water desalination as well as energy storage and conversion. In this study, PCFs were prepared from polyacrylonitrile (PAN) by proton irradiation and carbonization. Porous PAN films were prepared by a non-solvent-induced phase separation process. The porous PAN films were irradiated with proton ions, and then carbonized in a tube furnace at various fluences under an inert atmosphere. It was found that pore structures were well maintained during proton irradiation and high-temperature carbonization processes. The Raman and XRD results showed that pseudo-graphitic structures were formed by the carbonization of proton irradiated porous PAN films. The electrical conductivity of the prepared PCFs increased with an increasing carbonization temperature due to the formation of more graphitic structures at a higher temperature.