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In the present study, we used the electrochemical transparency of graphene to show that the direct intercalation of alkali-metal cations is not a prerequisite for the redox reaction of Prussian blue (PB). PB thin films passivated with monolayer graphene still underwent electrochemical redox reactions in the presence of alkali-metal ions (K

Tissue microarchitecture imposes physical constraints to the migration of individual cells. Especially in cancer metastasis, three-dimensional structural barriers within the extracellular matrix are known to affect the migratory behavior of cells, regulating the pathological state of the cells. Here, we employed a culture platform with micropillar arrays of 2 μm diameter and 16 μm pitch (2.16 micropillar) as a mechanical stimulant. Using this platform, we investigated how a long-term culture of A549 human lung carcinoma cells on the (2.16) micropillar-embossed dishes would influence the pathological state of the cell. A549 cells grown on the (2.16) micropillar array with 10 μm height exhibited a significantly elongated morphology and enhanced migration even after the detachment and reattachment, as evidenced in the conventional wound-healing assay, single-cell tracking analysis, and

Structural analysis of proteins using X-ray crystallography is crucial for discovering their biochemical functionalities. However, growing X-ray-quality crystals of proteins is often a challenging ...

In the present study, we showed that hydrophilic graphene can serve as an ideal imaging plate for biological specimens. Graphene being a single-atom-thick semi-metal with low secondary electron emission, array tomography analysis of serial sections of biological specimens on a graphene substrate showed excellent image quality with improved z-axis resolution, without including any conductive surface coatings. However, the hydrophobic nature of graphene makes the placement of biological specimens difficult; graphene functionalized with polydimethylsiloxane oligomer was fabricated using a simple soft lithography technique and then processed with oxygen plasma to provide hydrophilic graphene with minimal damage to graphene. High-quality scanning electron microscopy images of biological specimens free from charging effects or distortion were obtained, and the optical transparency of graphene enabled fluorescence imaging of the specimen; high-resolution correlated electron and light microscopy analysis of the specimen became possible with the hydrophilic graphene plate.

The development of promising separator candidates, offering both great physical rigidity and high thermal resistance, is still a global challenge to guarantee high-performance electrochemical cells. Freestanding hexagonal boron nitride (h-BN) separators are developed using strategically combined synthetic steps with liquid and thermal expansion exfoliation methods, which can simply fabricate the largely yielded h-BN nanosheets. The as-prepared freestanding h-BN nanosheet separator presents better ionic conductivity than commercial polymer separators and further provides excellent stability of Li ion cells by suppressing the protruding dendritic Li growth during cycles on the electrodes, as well as the high thermal and electrochemical stabilities of h-BN nanosheet separators even after the aging process at high temperatures of 80–120 °C. Furthermore, lithium titanate (LTO) batteries with the freestanding h-BN separators maintain an outstanding reversible Coulombic efficiency of ∼99% after 600 cycles, as well as high cycling retention, indicating the significant improvement in battery performance compared to the LTO batteries with commercial polymer separators. Thus, the freestanding h-BN separators may provide a new strategic way for the efficient storage of charge in next-generation rechargeable batteries and high-safety energy storage applications.

Dopamine produces neuromodulation throughout the basal ganglia, cortex and other brain regions, and is implicated in movement control, neural mechanisms of reward and actions of misused substances. The efferent projections of dopaminergic neurons with somata in the substantia nigra pars compacta and ventral tegmental area strongly innervate different striatal subregions. While much is known about the function of these neurons, there is a relative deficiency of information aboutin vivodopamine dynamics in the nigrostriatal projections, especially those to the dorsolateral striatum (DLS). In past studies, subsecond dopamine changes were measured predominantly with fast-scan cyclic voltammetry (FSCV) both in brain slices andin vivo. However, traditional FSCV has limitations in discriminating among catecholamines, and cannot be used for simultaneous measurement of both slow and fast/phasic dopamine changes. In addition, FSCV has been most useful for measuring dopamine in the ventral striatumin vivowith less utility for measurement in dorsolateral striatum. The development of genetically encoded dopamine sensors has provided a new approach to measuring slow and fast dopamine dynamics both in brain slices andin vivo, raising the hope of more facile measurement ofin vivodopamine measurements, including in areas where measurement was previously difficult with FSCV. To this end, we first evaluated dLight photometry in brain slices with simultaneous FSCV. We found that both techniques yielded comparable findings. However, differences were noted in responses to dopamine transporter inhibitors, including cocaine. We then usedin vivofiber photometry with dLight to examine responses to cocaine in DLS and compared responses during Pavlovian conditioning in DLS to two other striatal subregions. These experiments show that dopamine increases are readily detectable in DLS and provide new information about dopamine transient kinetics and slowly developing signaling during conditioning. Overall, our findings indicate that dLight photometry is well suited to measuring dopamine dynamics in a striatal region of great interest where such measurements were difficult previously.

Neural cell differentiation has been extensively studied in two-dimensional (2D) cell culture plates. However, the cellular microenvironment and extracellular matrix (ECM) are much more complex and flat 2D surfaces are hard to mimic in ECM. Carbon nanotubes (CNTs) and graphenes are multidimensional carbon-based nanomaterials and may be able to provide extra dimensions on cell growth and differentiation. To determine the effect of CNTs and graphene surfaces on the growth, gene expression, differentiation and functionality of neuroblastoma to a neural cell, SH-SY5Y cells were grown on a 2D (control) surface, a CNT network and a graphene film. The data suggest that SH-SY5Y cells grown on CNT surfaces show an average 20.2% increase in cell viability; 5.7% decrease in the ratio of cells undergoing apoptosis; 78.3, 43.4 and 38.1% increases in SOX2, GFAP and NeuN expression, respectively; and a 29.7% increase in mean firing rate on a multi-electrode array. SH-SY5Y cells grown on graphene film show little or no changes in cell properties compared to cells grown in 2D. The data indicate that the three-dimensional (3D) surface of CNTs provides a favorable environment for SH-SY5Y cells to proliferate and differentiate to neurons.

A high-performance machine learning-assisted gas sensor strategy based on the integration of supervised and unsupervised learning with a gas-sensitive semiconductor metal oxide (SMO) gas sensor array is introduced. A 4-SMO sensor array was chosen as a test sensor system for detecting carbon monoxide (CO) and ethyl alcohol (C2H5OH) mixtures using 15 different combinations. Gas sensing detection/classification was performed with different numbers of gas sensor and machine learning algorithms. K-Means clustering was successfully employed to rationally identify the similarity features of targeted gases among 4 different groups, i.e., matrix gas, two single-component gases, and one two-gas mixture, based on only unlabeled voltage-based gas sensing information. Detailed classification was performed through a multitude of supervised algorithms, i.e., 2-layer artificial neural networks (ANNs), 4-layer deep neural networks (DNNs), 1-dimensional convolutional neural networks (1D CNNs), and 2-dimensional CNNs (2D CNNs). The numerical-based DNNs and image-based CNNs are shown to be excellent approaches for gas detection and classification, as indicated by the highest accuracy and lowest loss indicators. Through the analysis of the influence of the number of sensors on the arrayed gas sensor system, the application of machine learning methodology to an arrayed gas sensor system demonstrates four unique features, i.e., a data augmentation methodology, machine learning approach of combining K-means clustering and neural networks, and a systematic approach to optimized sensor combinations, potentially leading to the practical sensor networks based on chemical sensors. Even two SMO sensor combinations are shown to be highly effective in gas discrimination against diverse gas environments assisted through numeric-based DNNs and image-based 1D CNNs, overcoming the simple clustering proposed through the unsupervised K-means clustering.

The excellent physical and chemical properties of carbon nanomaterials render them suitable for application in gas sensors. However, the synthesis of carbon nanomaterials using high-temperature furnaces is time consuming and expensive. In this study, we synthesize a carbon nanomaterial using local laser-scribing on a substrate coated with a Cu-embedded polyimide (PI) thin film to reduce the processing time and cost. Spin coating using a Cu-embedded PI solution is performed to deposit a Cu-embedded PI thin film (Cu@PI) on a quartz substrate, followed by the application of a pulsed laser for carbonization. In contrast to a pristine PI solution-based PI thin film, the laser absorption of the Cu-embedded PI thin film based on Cu@PI improved. The laser-scribed carbon nanomaterial synthesized using Cu@PI exhibits a three-dimensional structure that facilitates gas molecule absorption, and when it is exposed to NO2 and NH3, its electrical resistance changes by −0.79% and +0.33%, respectively.

Carbon nanomaterials have attracted significant research attention as core materials in various industrial sectors owing to their excellent physicochemical properties. However, because the preparation of carbon materials is generally accompanied by high-temperature heat treatment, it has disadvantages in terms of cost and process. In this study, highly sensitive carbon nanomaterials were synthesized using a local laser scribing method from a copper-embedded polyacrylonitrile (CuPAN) composite film with a short processing time and low cost. The spin-coated CuPAN was converted into a carbonization precursor through stabilization and then patterned into a carbon nanomaterial of the desired shape using a pulsed laser. In particular, the stabilization process was essential in laser-induced carbonization, and the addition of copper promoted this effect as a catalyst. The synthesized material had a porous 3D structure that was easy to detect gas, and the resistance responses were detected as −2.41 and +0.97% by exposure to NO2 and NH3, respectively. In addition, the fabricated gas sensor consists of carbon materials and quartz with excellent thermal stability, therefore, it is expected to operate as a gas sensor even in extreme environments.

We report on the modulation of the electrical properties of graphene-based transistors that mirror the properties of a few nanometers thick layer made of dipolar molecules sandwiched in between the 2D material and the SiO2 dielectric substrate. The chemical composition of the films of quinonemonoimine zwitterion molecules adsorbed onto SiO2 has been explored by means of X-ray photoemission and mass spectroscopy. Graphene-based devices are then fabricated by transferring the 2D material onto the molecular film, followed by the deposition of top source-drain electrodes. The degree of supramolecular order in disordered films of dipolar molecules was found to be partially improved as a result of the electric field at low temperatures, as revealed by the emergence of hysteresis in the transfer curves of the transistors. The use of molecules from the same family, which are suitably designed to interact with the dielectric surface, results in the disappearance of the hysteresis. DFT calculations confirm that the dressing of the molecules by an external electric field exhibits multiple minimal energy landscapes that explain the thermally stabilized capacitive coupling observed. This study demonstrates that the design and exploitation of ad hoc molecules as an interlayer between a dielectric substrate and graphene represents a powerful tool for tuning the electrical properties of the 2D material. Conversely, graphene can be used as an indicator of the stability of molecular layers, by providing insight into the energetics of ordering of dipolar molecules under the effect of electrical gating.

Reduced graphene oxide (rGO) has potential as a mass-producible and cost-effective substitute for graphene, but displays poor crystal quality due to various types of structural defects. Though many attempts have been reported to improve the quality of rGO, most of them require sophisticated equipment or severe conditions such as toxic chemicals, high temperature, and electron beam or plasma treatment in ultra-high vacuum (UHV) conditions. Here, we report a mild and simple solution-based healing method for obtaining high-quality rGO, with this method involving the use of a simple camera flash light treatment and the nontoxic chemicals l -ascorbic acid and ethanol. Exposing a GO solution containing l -ascorbic acid and ethanol to the flash light irradiation for a short amount of time (

Our growing energy demands must be met by a sustainable supply with reduced carbon intensity. One of the most exciting prospects to realize this goal is the photocatalyst-biocatalyst integrated artificial photosynthesis system which affords solar fuel/chemicals in high selectivity from CO2. Graphene based photocatalysts are highly suitable for the system, but their industrial scale use requires immobilization for improved separation and recovery of the photocatalyst. Therefore for practical purposes, design and fabrication of film type graphene photocatalyst with higher solar energy conversion efficiency is an absolute necessity. As a means to achieve this, we report herein the successful development of a new type of flexible graphene film photocatalyst that leads to >225% rise in visible light harvesting efficiency of the resultant photocatalyst-biocatalyst integrated artificial photosynthesis system for highly selective solar fuel production from CO2 compared to conventional spin coated graphene film photocatalyst. It is an important step towards the design of a new pool of graphene film based photocatalysts for artificial photosynthesis of solar fuels from CO2.

Various intriguing quantum transport measurements for carbon nanotubes (CNTs) based on their unique electronic band structures have been performed adopting a field-effect transistor (FET), where the contact resistance represents the interaction between the one-dimensional and three-dimensional systems. Recently, van der Waals (vdW) gap tunneling spectroscopy for single-walled CNTs with indium–metal contacts was performed adopting an FET device, providing the direct assignment of the subband location in terms of the current–voltage characteristic. Here, we extend the vdW gap tunneling spectroscopy to multi-walled CNTs, which provides transport spectroscopy in a tunneling regime of ~1 eV, directly reflecting the electronic density of states. This new quantum transport regime may allow the development of novel quantum devices by selective electron (or hole) injection to specific subbands.

Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of the FET with a specific antibody against SARS-CoV-2 spike protein. The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect the SARS-CoV-2 spike protein at concentrations of 1 fg/mL in phosphate-buffered saline and 100 fg/mL clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 × 101 pfu/mL) and clinical samples (LOD: 2.42 × 102 copies/mL). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.

Head-fixation of awake rodents is a method that allows for sophisticated investigation and manipulation of neural circuits in vivo, that would otherwise be impossible in completely freely moving animals. However, while it is known that head-fixation induces stress, its scale and habituation dynamics remain unclear. Thus, interpretation of physiological and behavioral experiments would greatly benefit from the characterization of the stress response. In our study, we used the Mobile HomeCage system (Neurotar, Finland) where animals are head-fixed to an aluminum frame, but otherwise freely moving in an ultralight carbon container floating above an air-dispensing base. To better understand this experimental environment, we analyzed locomotion and stress during an extended habituation protocol. For 25 consecutive days, mice were prepared as they would be for recording experiments, i.e. head-fixed while standing on the air-lifted platform for 2 hours per day. Throughout 25 days, blood samples were taken periodically from the tail vein to measure variation in the stress-related hormone, corticosterone. These data were compared and contrasted with behavioral data including locomotion during the 2-hours head-fixed habituation sessions and several classical behavioral measurements known to be affected by chronic mild stress.

In the present study, phase-dependent gas sensitivities of MoS

Manual restriction of head movement, or head-fixation, of awake rodents allows for sophisticated investigation of neural circuits in vivo, that would otherwise be impossible in completely freely moving animals. While it is known that head-fixation induces stress, the scale of this stress and habituation dynamics remain unclear. We used the Mobile HomeCage system (Neurotar Ltd, Finland) where animals have their heads fixed to an aluminum frame but are otherwise freely moving in an ultralight carbon container floating above an air-dispensing base. For 25 consecutive days, mice were head-fixed while standing on the air-lifted platform for 2 h per day and blood samples were taken periodically to measure variation in the stress-related hormone, corticosterone. We showed that the initial increase in corticosterone concentration is followed by a return to control level throughout the days of head-fixed training. We also found a locomotor correlate of this drop. We conducted a battery of stress-sensitive behavioral paradigms in freely-moving mice that revealed minor differences following chronic head-fixation. Finally, we analyzed motor-skill learning in the head-fixed setup with a floating container. We believe that our results may contribute to better interpretation of past literature and future in vivo experiments using head-fixed animals.

The topoisomerase I inhibitors SN-38 and camptothecin (CPT) have shown potent anticancer activity, but water insolubility and metabolic instability limits their clinical application. Utilizing carbon nanotubes as a protective shell for water-insoluble SN-38 and CPT while maintaining compatibility with aqueous media via a carboxylic acid-functionalized surface can thus be a strategy to overcome this limitation. Through hydrophobic-hydrophobic interactions, SN-38 and CPT were successfully encapsulated in carboxylic acid functionalized single-walled carbon nanotubes and dispersed in water. The resulting cell proliferation inhibition and drug distribution profile inside the cells suggest that these drug-encapsulated carbon nanotubes can serve as a promising delivery strategy for water-insoluble anticancer drugs.

An inability to precisely control doping has hindered the development of electrically reliable and predictable low-dimensional devices. Here, we demonstrated a modulation of electronic bands of one-dimensional carbon nanotubes (CNTs) over a wide range by using metal electrodes having almost the same work function as the CNT in a dual-gate mode. Gate-response curves obtained from Ti versus In metal-contacted devices showed opposite behaviors in shape and magnitude in an ambipolar state, which was shown to be due to the difference between the pinned positions of their Fermi levels in the band gap of the CNT with different work functions of the metals. By varying the gate-bias voltages of the dual gates, we successfully demonstrated that the electronic band profile of the CNT can be modulated precisely and over a wide range to higher and lower energy levels, resulting in the ability to have it form p-metal, p-type semiconductor, ambipolar, n-type semiconductor, and n-metallic electronic states.

Recently, three-dimensional (3D) printing has garnered tremendous amounts of attention in various applications. In this study, we suggest a facile means of creating 3D-printed foldable electrodes on paper via the direct printing of composite pastes consisting of conductive fillers and a thermoplastic elastomer. The 3D-printability of the prepared composite pastes is investigated depending on the rheological properties. It is revealed that the composite paste with a high storage modulus would enable the formation of highly conductive features with a resistance of 0.4 Ω cm−1 on three-dimensional paper structures. The mechanical bending/folding stability levels of the printed electrodes are evaluated to judge the possibility of realizing 3D-printed origami electronics. The resistance is changed slightly with a normalized resistance value of 2.3, when the printed electrodes are folded with a folding angle of 150°. It is demonstrated that the 3D-printed composite electrodes are applicable to various origami electronics, including electrical circuits, strain sensors and electrochemical sensors.

Decorating graphene with nanoparticles is an effective method for improving gas selectivity and sensitivity of graphene-based chemical sensors. We report herein the enhancement of the gas selectivity and improved response of a graphene-based chemical sensor by decorating the graphene with synthesized Ag2S nanoparticles. To synthesize uniformly sized Ag2S nanoparticles, we used the ultrasonic irradiation method, and then the synthesized Ag2S nanoparticles were decorated onto graphene uniformly, by using a simple spin coating method. Gas responses of the resulting chemical sensor were tested for volatile organic compounds (VOCs) such as acetone, ethanol, and hexane. While no noticeable gas response changes were obtained for ethanol and hexane vapors, a dramatic increase of ~660% resulted from exposure of the sensor to acetone vapor. In order to determine the mechanism behind the excellent acetone response of graphene decorated with Ag2S nanoparticles, density functional theory (DFT) calculations were performed, and showed higher binding energies and electron transfer between Ag2S and acetone than between Ag2S and the other VOCs. This result indicated that decorating graphene with nanoparticles displaying a high binding energy for the target gas is an efficient way to improve the gas selectivity and response levels of graphene-based chemical sensors.

As a consequence of their unique electronic band structures, low-dimensional materials such as one-dimensional (1D) single-wall carbon nanotubes (SWCNTs), 2D graphene and various 2D transition-metal dichalcogenides have exhibited intriguing electrical transport properties when incorporated into field-effect transistors. Meanwhile, the van-der-Waals (vdW) interfaces between top-contacted metals and low-dimensional materials have become a challenging issue for future high-performance electronics. Here, we report a new aspect of vdW interface that offers vdW-gap tunneling spectroscopy by adopting indium (In) as a top-contacted metal on SWCNTs without an artificial insulating tunnel barrier. We show that multiple differential conductance peaks for varying bias voltages correspond to the van Hove singularities existing in the electronic density of states of SWCNTs. Our first-principles calculations reveal that In forms a physisorption interface with a considerable vdW gap, which causes little disruption to the density of states of the SWCNTs near the metal interface and which thus allows vdW-gap tunneling spectroscopy.

We obtained preferential in-plane molecular orientation and charge-transport anisotropy in pentacene thin-film transistors (TFTs) on conventional SiO 2 /Si substrates. The nanoscale SiO 2 grooves with depths of 1–3 nm were prepared by a simple scratching process with diamond powder to create a new type of alignment template for inducing the aligned growth of pentacene with in-plane anisotropy. Results of atomic force microscopy and grazing-incidence X-ray diffraction showed that the nanogrooved SiO 2 structure could control the alignment and growth mode of pentacene, and it remarkably decreased the grain size of the pentacene crystals. The charge-carrier mobility along the parallel axis of the nanogrooved structure (0.392 ± 0.039 cm 2 /(V·s)) was more than four-fold higher than that perpendicular to the alignment (0.104 ± 0.048 cm 2 /(V·s)). In addition, we investigated the effect of nanogrooved SiO 2 's surface roughness on the electrical properties of the pentacene TFT and found out that the surface roughness of SiO 2 dielectric layer was more crucial factor on the device performance compared to the preferential alignment of the pentacene molecule.

Integrated graphene films (IGFs) with self-assembled single-layer graphene as a channel and multi-layer graphene as an electrode material were synthesized simultaneously using a one-step process by thermal chemical vapor deposition. The prominent difference in graphene growth rate between Ni and Cu catalytic substrates made enable to synthesize the IGFs with self-assembled single-layer and multi-layer graphene on a Cu foil with pre-patterned Ni films. The thickness of multi-layer graphene for IGFs was precisely controlled by optimizing conditions including the injection temperature of carbon feedstock and the surface concentration of Ni atoms affected by the inter-diffusion related to the growth temperature and time. The thickness and crystallinity of synthesized IGFs were evaluated by resonant Raman spectroscopy. We fabricated the IGFs-based field effect transistors (FETs) to examine electrical transport properties of the films. These results suggest that the synthesis technique for IGFs could lead to mass fabrication of wearable graphene-based FETs in the near future.

Semiconductor gas sensors are advantageous in miniaturization and can be used in a wide range of applications, yet consume large power due to high operating temperature. Here we demonstrated the ability of nanoscale scratches produced with mechanical abrasion to enhance the chemical sensitivity of thin-film-type semiconductor sensors. Well-aligned arrays of scratches parallel to the electrical current direction between the source and drain electrodes were made, using typical polishing machines with diamond suspensions, on semiconductor thin films produced with various deposition methods such as atomic layer deposition (ALD), sputtering, and the sol–gel technique. Processing with sharp diamond microparticles left nano-grooves on the surface, together with changes in chemical composition. For all of the tested metal oxide thin films, the introduction of scratches yielded increased quantities of oxygen vacancies and metallic components. Scratched ZnO devices exhibited superior performance even at room temperature, as predicted by a computational simulation that showed increased binding energy of gas molecules on defects. The scratch technique shown in the present study may be used to produce dense arrays of nanometer-scale, chemically functionalized line patterns on substrates larger than a few tens of centimeters with minimum cost, which in turn may be used in a variety of applications including massive arrays of sensors displaying high sensitivity.

The electrical properties of a single-walled carbon nanotube network were investigated after photoresist treatment with the pristine device. Atomic force microscopy found that the diameters of the single-walled carbon nanotubes were increased after photoresist treatment and that the photoresist could not be completely removed from nanotube surfaces by using a simple cleaning process with an organic solvent. Although the presence of a residual photoresist had no noticeable effects on the Raman spectrum of single-walled carbon nanotubes in our devices, the charge carrier mobilities and the on/off ratios of the single-walled carbon nanotube devices were lowered due to the photoresist treatment, and the gate-hysteresis behavior in the devices that had undergone photoresist treatment was found to be different from that of pristine devices.

We show that graphene device could be controllably doped by the bottom substrate by inserting atomic layer deposition grown ZnO between graphene and SiO 2 substrate. To clarify the effect of bottom ZnO, length of the graphene transistor channel was varied from 20 to 200 μm, while that of ZnO was fixed to 10 μm. Graphene devices supported on ZnO film show marked difference from those supported on SiO 2 substrates; bottom ZnO layer behave as an electron donor. UV illumination experiment on hybrid graphene-ZnO device reveals that the effect of doping from ZnO becomes negligible when the graphene channel length made about four times larger than that of ZnO stripe.

Multifunctional zinc oxide (ZnO) has been generated as nanoparticles or nanorods and applied to various medical purposes since it exhibits several biological actions including anticancer activity. Especially, due to antibacterial activity and effects on bone regeneration, ZnO is widely used in implants and scaffolds in the orthopedic and dental fields. However, concerns over side effects have been raised recently in the clinical use of ZnO, and it is necessary to assess the safety of ZnO regarding its inflammatory potential in the bone environment. This made us hypothesize that the inflammatory activity of zinc ions released from ZnO NPs could be harmful to induce bone resorption but that their cytotoxicity would be beneficial to kill osteosarcoma. To clarify this hypothesis, in the present work, the effects of ZnO on bone matrix and abnormal bone environments were investigated quantitatively using ZnO chips, filter paper, or glass slides coated with thin films of ZnO grown via atomic layer deposition (ALD). ALD-grown ZnO thin films exhibit thickness with atomic precision, which enables the quantitative analysis of the effects of ZnO.

To utilize human heat energy as a permanent power source, we demonstrate, for the first time, an intrinsically highly foldable and stretchable thermoelectric generator that is based upon chemically exfoliated 1T-transition metal dichalcogenide (TMDC) nanosheets (NSs) for self-powered wearable electronics. The power factors of WS2 (n-type) and NbSe2 (p-type) NS films were evaluated to be 5–7 μ K−2 m−1 and 26–34 μW K−2 m−1, respectively, near room temperature. With these films, parallel-connected thermoelectric generators that were fabricated were able to constantly produce up to 38 nW of output power at Δ60 K. The thermoelectric device stably sustained its performance, even after 100 bending cycles and after 100 stretching cycles (50% strain). By direct observation, we found that the film is highly stretched by partial tearing and folding but still maintains an electrical percolation pathway. The morphology then is quickly recovered by a plug-in contact between the torn parts as the external strain is released. Finally, we demonstrate the electric power generation from a prototype wearable thermoelectric generator that was woven into a wristband fitted on a real human body.

We report anti-cancer activity of ZnO thin-film-coated chips by sustained release of zinc ions. ZnO chips were fabricated by precisely tuning ZnO thickness using atomic layer deposition, and their potential to release zinc ions relative to the number of deposition cycles was evaluated. ZnO chips exhibited selective cytotoxicity in human B lymphocyte Raji cells while having no effect on human peripheral blood mononuclear cells. Of importance, the half-maximal inhibitory concentration of the ZnO chip on the viability of Raji cells was 121.5 cycles, which was comparable to 65.7 nM of daunorubicin, an anti-cancer drug for leukemia. Molecular analysis of cells treated with ZnO chips revealed that zinc ions released from the chips increased cellular levels of reactive oxygen species, including hydrogen peroxide, which led to the down-regulation of anti-apoptotic molecules (such as HIF-1a, survivin, cIAP-2, claspin, p-53, and XIAP) and caspase-dependent apoptosis. Because the anti-cancer activity of ZnO chips and the mode of action were comparable to those of daunorubicin, the development and optimization of ZnO chips that gradually release zinc ions might have clinical anti-cancer potential. A further understanding of the biological action of ZnO-related products is crucial for designing safe biomaterials with applications in disease treatment. (C) 2016 The Authors. Published by Elsevier Ireland Ltd.

Automated semantic segmentation is applied to the quantification of microstructural features in three-phase composite cathode materials of solid oxide fuel cells (SOFCs), i.e., GDC/LSC/Pore where GDC stands for Gd2O3-doped CeO2 and LSC for La0.6Sr0.4CoO3-δ. Our aim is to eliminate the tedious involvement of human experts and the associated errors. The high volume of image information sets is generated using automatic acquisition systems involving focused-ion beam scanning electron microscopy through a so-called slice-view procedure. Through the integration of semantic segmentation with image processing-assisted stereography tools, the following detailed microstructural features are quantitatively extracted automatically and objectively without any human involvement: size distribution, surface (or equivalently, volume) fraction, lengths of two-phase boundaries, and density of triple-phase boundaries based on two-dimensional images. The extracted two-dimensional information is connected with three-dimensional reconstruction analysis. The implications of semantic segmentation in SOFCs are discussed considering efficient analysis and design of high-performance electrode structures in energy-oriented devices.

In the present study, phase-dependent gas sensitivities of MoS2 chemical sensors were examined. While 1T-phase MoS2 (1T-MoS2) has shown better chemical sensitivity than has 2H-phase MoS2 (2H-MoS2), the instability of the 1T phase has been hindering applications of 1T-MoS2 as chemical sensors. Here, the chemical sensitivity of MoS2 locked in its 1T phase by using a ZnO phase lock was investigated. To develop MoS2 chemical sensors locked in the 1T phase, we synthesized a multi-dimensional nanomaterial by growing ZnO nanorods onto MoS2 nanosheets (ZnO@1T-MoS2). Raman spectroscopy and x-ray photoelectron spectroscopy analyses of such phase-locked 1T-MoS2 subjected to flash light irradiation 100 times confirmed its robustness. ZnO nanomaterials hybridized on MoS2 nanosheets not only froze the MoS2 at its 1T phase, but also increased the active surface area for chemical sensing. The resulting hybridized material showed better response, namely better sensitivity, to NO2 gas exposure at room temperature than did 1T-MoS2 and 2H-MoS2. This result indicated that increased surface area and heterojunction formation between MoS2 and ZnO constitute a more promising route for improving sensitivity than using the 1T phase itself.

We present a strategy for avoiding polymeric residues, excessive heating and solvent exposure when transforming large area transferred CVD graphene single layer films into series of planar devices. Such dry process is a key prerequisite for chemical functionalization applications or for organic electronics compatibility, and opens the possibility to integrate graphene electrodes with thermally or chemically sensitive materials, as well as substrates incompatible with lithography processing. Patterning and metal evaporation are performed through a multi-step mechanical stencils methodology, and low temperatures magneto transport measurements are used to validate devices with preserved electrical fingerprints of graphene. This is particularly critical for the argon beam milling process step. Remarkably, the Quantum Hall signature of our devices remains robust, even though defective sample edges result from the beam exposure. Shubnikov-de Hass (SdH) oscillations and weak (anti-) localization signatures of monolayer graphene confirm the excellent intrinsic properties of such processed samples, rarely observed on CVD-processed devices.

The mechanism of charge transfer through nanomaterials such as graphene remains unclear, and the amount of charge that can be transferred from/to graphene without damaging its structural integrity is unknown. In this communication, we show that metallic nanoparticles can be decorated onto graphene surfaces as a result of charge transfer from the supporting substrate to an adjoining solution containing metal ions. Au or Pt nanoparticles were formed with relatively high yield on graphene-coated substrates that can reduce these metal ions, such as Ge, Si, GaAs, Al, and Cu. However, metal ions were not reduced on graphene surfaces coated onto non-reducing substrates such as SiO2 or ZnO. These results confirm that graphene can be doped by exploiting charge transfer from the underlying substrate; thus graphene is not only transparent with respect to visible light, but also with respect to the charge transfer. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Local doping of Al:ZnO into a ZnO matrix was performed vertically at various positions in a thin film using atomic layer deposition, and its influence was investigated by analyzing thin film transistor (TFT) characteristics. The position specific dopant distribution in the films was confirmed by high resolution transmission electron microscopy. It was found that doping specific locations in the active channel layer of a TFT had a different impact on its electrical characteristics. When near the semiconductor/gate dielectric interface, doping had a significant impact on the mobility of the TFT devices, which showed a gradual recovery as the doped region was moved away from the interface. The original characteristics of the device were almost completely restored once the doped region was moved more than 15 nm away from the interface, and when moved further away the output characteristics portrayed a shift in threshold voltage while preserving all other electrical characteristics. Various doping concentrations were implemented in regions both near and far away from the interface to gain a better understanding of the phenomena. The experimental results given here imply that the geographical position of doping is as important as selecting a dopant material in the device optimization of TFTs.

A bipolar strain sensor based on an ultra-thin film of single-walled carbon nanotubes (SWNTs) has been fabricated. First, a random network of SWNTs was grown on a Si substrate with thermal oxide by using chemical vapor deposition and then transferred to a transparent poly(dimethyl)siloxane (PDMS) film. A mechanical load was applied by pressing the PDMS-SWNT film with a blunt micrometer tip, and its electrical conductance was found to decrease linearly with increasing pressure. Upward bending of the flexible PDMS-SWNT film was found to yield increases in conductance whereas downward bending of the film was found to result in decreases in the conductance. We modeled the SWNT network on the PDMS film with a two-dimensional percolation system, and found that the increases (decreases) in the conductance of the film upon bending could be explained in terms of stick-density changes in the 2-D percolation system. Finally, because PDMS swells with certain organic vapors, a PDMS-SWNT film can be used as a chemical sensor for volatile organic compounds. Unlike for three-dimensional composites of SWNTs and polymers, the bipolar response upon bending and simple fabrication process for the system introduced here mean that it is an attractive candidate for tactile and motion sensor applications.