Polycrystalline Few-Layer Graphene as a Durable Anticorrosion Film for Copper.

Corrosion of metals in atmospheric environments is a worldwide problem in industry and daily life. Traditional anticorrosion methods including sacrificial anodes or protective coatings have performance limitations. Here, we report atomically thin, polycrystalline few-layer graphene (FLG) grown by chemical vapor deposition as a long-term protective coating film for copper (Cu). A six-year old, FLG-protected Cu is visually shiny and detailed material characterizations capture no sign of oxidation. The success of the durable anticorrosion film depends on the misalignment of grain boundaries between adjacent graphene layers. Theoretical calculations further found that corrosive molecules always encounter extremely high energy barrier when diffusing through the FLG layers. Therefore, the FLG is able to prevent the corrosive molecules from reaching the underlying Cu surface. This work highlights the interesting structures of polycrystalline FLG and sheds insight into the atomically thin coatings for various applications.

Enhanced dielectric performance in polymer composite films with carbon nanotube-reduced graphene oxide hybrid filler.

The electrical conductivity and the specific surface area of conductive fillers in conductor-insulator composite films can drastically improve the dielectric performance of those films through changing their polarization density by interfacial polarization. We have made a polymer composite film with a hybrid conductive filler material made of carbon nanotubes grown onto reduced graphene oxide platelets (rG-O/CNT). We report the effect of the rG-O/CNT hybrid filler on the dielectric performance of the composite film. The composite film had a dielectric constant of 32 with a dielectric loss of 0.051 at 0.062 wt% rG-O/CNT filler and 100 Hz, while the neat polymer film gave a dielectric constant of 15 with a dielectric loss of 0.036. This is attributed to the increased electrical conductivity and specific surface area of the rG-O/CNT hybrid filler, which results in an increase in interfacial polarization density between the hybrid filler and the polymer.

Enhancement of the electrical properties of graphene grown by chemical vapor deposition via controlling the effects of polymer residue.

Residual polymer (here, poly(methyl methacrylate), PMMA) left on graphene from transfer from metals or device fabrication processes affects its electrical and thermal properties. We have found that the amount of polymer residue left after the transfer of chemical vapor deposited (CVD) graphene varies depending on the initial concentration of the polymer solution, and this residue influences the electrical performance of graphene field-effect transistors fabricated on SiO2/Si. A PMMA solution with lower concentration gave less residue after exposure to acetone, resulting in less p-type doping in graphene and higher charge carrier mobility. The electrical properties of the weakly p-doped graphene could be further enhanced by exposure to formamide with the Dirac point at nearly zero gate voltage and a more than 50% increase of the room-temperature charge carrier mobility in air. This can be attributed to electron donation to graphene by the -NH2 functional group in formamide that is absorbed in the polymer residue. This work provides a route to enhancing the electrical properties of CVD-grown graphene even when it has a thin polymer coating.

Inductive tuning of Fano-resonant metasurfaces using plasmonic response of graphene in the mid-infrared.

Graphene is widely known for its anomalously strong broadband optical absorptivity of 2.3% that enables seeing its single-atom layer with the naked eye. However, in the mid-infrared part of the spectrum graphene represents a quintessential lossless zero-volume plasmonic material. We experimentally demonstrate that, when integrated with Fano-resonant plasmonic metasurfaces, single-layer graphene (SLG) can be used to tune their mid-infrared optical response. SLG's plasmonic response is shown to induce large blue shifts of the metasurface's resonance without reducing its spectral sharpness. This effect is explained by a generalized perturbation theory of SLG-metamaterial interaction that accounts for two unique properties of the SLG that set it apart from all other plasmonic materials: its anisotropic response and zero volume. These results pave the way to using gated SLG as a platform for dynamical spectral tuning of infrared metamaterials and metasurfaces.

Nitrogen-Doped Activated Hollow Carbon Nanofibers with Controlled Hierarchical Pore Structures for High-Performance, Binder-Free, Flexible Supercapacitor Electrodes.

Carbon nanofibers (CNFs) are a fascinating electrode material for energy storage devices due to their one-dimensionality, interconnected networks, and chemical stability. However, a relatively low specific surface area of CNFs hinders their use as supercapacitor electrodes. Here, nitrogen-doped hollow CNFs with hierarchical pore structures are prepared via electrospinning of core-shell polymer nanofibers and subsequent carbonization and activation under an ammonia atmosphere. Hierarchical pore structures with micro-, meso-, and macropores are controlled by an ammonia etching effect during the carbonization of polymer nanofibers. In addition, a hollow structure in CNFs is obtained by thermal decomposition of the core polymer during the carbonization/activation. The nitrogen-doped activated hollow CNFs (ahCNFs) exhibited an exceptionally high specific surface area of 3618 m2/g with increased mesopores. Thus, a symmetric supercapacitor using ahCNFs electrodes with a 6 M KOH aqueous electrolyte provides a high specific capacitance of 208 F/g at a current density of 1 A/g, a high energy density of 7.22 W h/kg at a power density of 502 W/kg, a good rate capability, and cyclic stability. Moreover, the freestanding ahCNFs are used for flexible supercapacitor electrodes without any binder. This work demonstrates the great potential of highly porous ahCNFs for high-performance energy storage devices.

Neural Responses to Intranasal Oxytocin in Youths With Severe Irritability.

OBJECTIVE: The authors investigated the neural impact of intranasal oxytocin on emotion processing areas in youths with severe irritability in the context of disruptive mood and behavior disorders. METHODS: Fifty-two participants with severe irritability, as measured by a score ≥4 on the Affective Reactivity Index (ARI), with diagnoses of disruptive behavior disorders (DBDs) and/or disruptive mood dysregulation disorder (DMDD) were randomly assigned to treatment with intranasal oxytocin or placebo daily for 3 weeks. Assessments were conducted at baseline and at the end of the trial; the primary outcomes were measures of irritability on the ARI and ratings on the Clinical Global Impressions severity scale (CGI-S) focusing on DBD and DMDD symptoms, and secondary outcomes included the CGI improvement scale (CGI-I) and ratings of proactive and reactive aggressive behavior on the Reactive-Proactive Aggression Questionnaire. Forty-three participants (22 in the oxytocin group and 21 in the placebo group) completed pre- and posttreatment functional MRI (fMRI) scans with the affective Stroop task. RESULTS: Youths who received oxytocin showed significant improvement in CGI-S and CGI-I ratings compared with those who received placebo. In the fMRI data, blood-oxygen-level-dependent (BOLD) responses to emotional stimuli in the dorsomedial prefrontal cortex and posterior cingulate cortex were significantly reduced after oxytocin compared with placebo. These BOLD response changes were correlated with improvement in clinical severity. CONCLUSIONS: This study provides initial and preliminary evidence that intranasal oxytocin may induce neural-level changes in emotion processing in youths with irritability in the context of DBDs and DMDD. This may lead to symptom and severity changes in irritability.

Electron Release via Internal Polarization Fields for Optimal S-H Bonding States.

Transition metal dichalcogenides (TMDs) have received considerable attention as promising electrocatalysts for the hydrogen evolution reaction (HER), yet their potential is often constrained by the inertness of the basal planes arising from their poor hydrogen adsorption ability. Here, the relationship between the electronic structure of the WS2 basal plane and HER activity is systemically analyzed to establish a clear insight. The valance state of the sulfur atoms on the basal plane has been tuned to enhance hydrogen adsorption through sequential engineering processes, including direct phase transition and heterostructure that induces work function-difference-induced unidirectional electron transfer. Additionally, an innovative synthetic approach, harnessing the built-in internal polarization field at the W-graphene heterointerface, triggers the in-situ formation of sulfur vacancies in the bottom WSx (x < 2) layers. The resultant modulation of the valance state of the sulfur atom stabilizes the W-S bond, while destabilizing the S-H bond. The electronic structural changes are further amplified by the release and transfer of surplus electrons via sulfur vacancies, filling the valance state of W and S atoms. Consequently, this work provides a comprehensive understanding of the interplay between the electronic structure of the WS2 basal plane and the HER activity, focusing on optimizing S-H bonding state.

Selective-area fluorination of graphene with fluoropolymer and laser irradiation.

We have devised a method to selectively fluorinate graphene by irradiating fluoropolymer-covered graphene with a laser. This fluoropolymer produces active fluorine radicals under laser irradiation that react with graphene but only in the laser-irradiated region. The kinetics of C-F bond formation is dependent on both the laser power and fluoropolymer thickness, proving that fluorination occurs by the decomposition of the fluoropolymer. Fluorination leads to a dramatic increase in the resistance of the graphene while the basic skeletal structure of the carbon bonding network is maintained. Considering the simplicity of the fluorination process and that it allows patterning with a nontoxic fluoropolymer as a solid source, this method could find application to generate fluorinated graphene in graphene-based electronic devices such as for the electrical isolation of graphene.

Improved electrical conductivity of graphene films integrated with metal nanowires.

Polycrystalline graphene grown by chemical vapor deposition (CVD) on metals and transferred onto arbitrary substrates has line defects and disruptions such as wrinkles, ripples, and folding that adversely affect graphene transport properties through the scattering of the charge carriers. It is found that graphene assembled with metal nanowires (NWs) dramatically decreases the resistance of graphene films. Graphene/NW films with a sheet resistance comparable to that of the intrinsic resistance of graphene have been obtained and tested as a transparent electrode replacing indium tin oxide films in electrochromic (EC) devices. The successful integration of such graphene/NW films into EC devices demonstrates their potential for a wide range of optoelectronic device applications.

Tunable Interlayer Interactions in Reduced Graphene Oxide Paper.

Free-standing graphene-based paper-like materials have garnered significant interest for various applications because of their tunable physical and chemical properties, along with unique multilayered structures. Because of the layered configuration of graphene paper, characterization of the interactions between graphene sheets is critical for understanding its fundamental properties and applications. We investigate the interlayer cohesion energies in graphene papers using the mode I fracture concept with double cantilever beam specimens. Mechanical separation along the middle of the graphene paper thickness enables the evaluation of interlayer bonding strength in the paper. Starting from graphene oxide paper, the chemical reduction using hydroiodic acid tunes the interlayer cohesion energy from 11.30 ± 0.25 to 4.78 ± 0.18 J/m2 as the reduction time increases. The interlayer cohesion energy is correlated with the oxygen content, interlayer spacing, and electrical conductivity of graphene papers. This work provides a fundamental characterization of the interlayer cohesion energy of graphene paper and establishes the potential for tunability of the interlayer interactions in graphene paper.

Mediating effect of amygdala activity on response to fear vs. happiness in youth with significant levels of irritability and disruptive mood and behavior disorders.

Introduction: Irritability, characterized by a tendency to exhibit increased anger, is a common clinical problem in youth. Irritability is a significant clinical issue in youth with various psychiatric diagnoses, especially disruptive behavior, and mood disorders (Attention-Deficit/Hyperactivity Disorder, Oppositional Defiant Disorder, Conduct Disorder, and Disruptive Mood Dysregulation Disorder). Although there have been previous studies focusing on functional alteration in the amygdala related to irritability, there is no comprehensive model between emotional, neuronal, and behavioral characteristics. Methods: Using an functional magnetic resonance imaging (fMRI) procedure, we investigated the relationships between behavioral irritability, selective impairments in processing facial emotions and the amygdala neural response in youth with increased irritability. Fifty-nine youth with disruptive mood and behavior disorder completed a facial expression processing task with an event-related fMRI paradigm. The severity of irritability was evaluated using the Affective Reactivity Index. Results: In the result of behavioral data, irritability, and reaction time (RT) differences between interpreting negative (fear) and positive (happiness) facial expressions were positively correlated. In the fMRI result, youth showed higher activation in the right cingulate gyrus, bilateral cerebellum, right amygdala, right precuneus, right superior frontal gyrus, right middle occipital gyrus, and middle temporal gyrus, during the happiness condition vs. fear condition. No brain region exhibited greater activation in the fear than in the happiness conditions. In the result of the mediator analysis, increased irritability was associated with a longer RT toward positive vs. negative facial expressions. Irritability was also positively associated with the difference in amygdala blood oxygen level-dependent responses between the two emotional conditions (happiness > fear). This difference in amygdala activity mediated the interaction between irritability and the RT difference between negative and positive facial expressions. Discussion: We suggest that impairment in the implicit processing of facial emotional expressions with different valences causes distinct patterns of amygdala response, which correlate with the level of irritability. These results broaden our understanding of the biological mechanism of irritability at the neural level and provide information for the future direction of the study.

Design and Control of Lightweight Bionic Arm Driven by Soft Twisted and Coiled Artificial Muscles.

Twisted and coiled actuators (TCAs), which are light but capable of producing significant power, were developed in recent times. After their introduction, there have been numerous improvements in performance, including development of techniques such as actuation strain and heating methods. However, the development of robots using TCA is still in its early stages. In this study, a bionic arm driven by TCAs was developed for light and flexible operation. The aim of this study was to gain a foothold in the future of robot development using TCA, which is considered as the appropriate artificial muscle. The main developments were with regard to the design (from actuator design to system design), system configuration for control, and control method. First, a process technology for repeatedly manufacturing TCA, which can be used practically and delivers sufficient performance, was developed. Based on the developed actuator, a joint was designed to move the elbow and hand. The final bionic arm was developed by integrating the TCA, pulley joint, and control system. It moved the elbow up to 100° and allowed the hand to move in three degrees of freedom. Using the control method for each joint, we were able to show the movement by using the hand and elbow.

Secretion of amyloidogenic gelsolin progressively compromises protein homeostasis leading to the intracellular aggregation of proteins.

Familial amyloidosis of Finnish type (FAF) is a systemic amyloid disease associated with the deposition of proteolytic fragments of mutant (D187N/Y) plasma gelsolin. We report a mouse model of FAF featuring a muscle-specific promoter to drive D187N gelsolin synthesis. This model recapitulates the aberrant endoproteolytic cascade and the aging-associated extracellular amyloid deposition of FAF. Amyloidogenesis is observed only in tissues synthesizing human D187N gelsolin, despite the presence of full-length D187N gelsolin and its 68-kDa cleavage product in blood-demonstrating the importance of local synthesis in FAF. Loss of muscle strength was progressive in homozygous D187N gelsolin mice. The presence of misfolding-prone D187N gelsolin appears to exacerbate the age-associated decline in cellular protein homeostasis (proteostasis), reflected by the intracellular deposition of numerous proteins, a characteristic of the most common degenerative muscle disease of aging humans, sporadic inclusion body myositis.

Oxidative doping renders graphene hydrophilic, facilitating its use as a support in biological TEM.

Graphene represents the first practical realization of crystalline supports in biological transmission electron microscopy (TEM) since their introduction over 30 years ago. The high transparency, minimal inelastic cross-section, and electrical conductivity of graphene are highly desirable characteristics for a TEM support. However, without a suitable method for rendering graphene supports, hydrophilic applications are limited. This work describes the in situ functionalization of graphene with minimal structural degradation, rendering TEM supports sufficiently hydrophilic for the mounting of biological samples.

Synthesis and characterization of large-area graphene and graphite films on commercial Cu-Ni alloy foils.

Controlling the thickness and uniformity during growth of multilayer graphene is an important goal. Here we report the synthesis of large-area monolayer and multilayer, particularly bilayer, graphene films on Cu-Ni alloy foils by chemical vapor deposition with methane and hydrogen gas as precursors. The dependence of the initial stages of graphene growth rate on the substrate grain orientation was observed for the first time by electron backscattered diffraction and scanning electron microscopy. The thickness and quality of the graphene and graphite films obtained on such Cu-Ni alloy foils could be controlled by varying the deposition temperature and cooling rate and were studied by optical microscopy, scanning electron microscopy, atomic force microscopy, and micro-Raman imaging spectroscopy. The optical and electrical properties of the graphene and graphite films were studied as a function of thickness.

Graphene Oxide-Chitosan Network on a Dialysis Cellulose Membrane for Efficient Removal of Organic Dyes.

Currently, water pollution is a significant health problem for both humans and animals due to large amounts of dye-containing wastewater. Thus, polymer composite membranes (PCMs) are considered as efficient adsorption/filtration membranes that can be utilized for removing organic dyes from contaminated water/wastewater. In this study, the goal is to explore the modification of the interfacial dialysis cellulose (DC) surface through molecular interactions of an active graphene oxide-chitosan (GO-CTS) composite hydrogel (GCCH) network without the use of an external cross-linker toward an effective dye removal ability using a simple casting process and a low-cost adsorption technique, resulting in the formation of a PCM, i.e., GO/CTS/DC membrane (GCD-mems). Concomitantly, the incorporation of the GCCH network (as an active hybrid network) and DC (as a supporting material) is considered as a promising approach toward a dye-removing PCM. As a result, the GCD-mems showed that cellulose robustly interacted via the chemical bonds of the GCCH network by maintaining the three-dimensional (3D) porous layer structures, and the functional surface of the membrane was enhanced toward specific groups for an effective dye removal approach. In addition, there is a significant improvement in dye removal performance after modification of the interfacial DC surface through molecular interactions of GCCH, i.e., high adsorption capacities of cationic and anionic dye molecules on the GCD-mems, compared to the relevant GO-based adsorbents. Also, the dye flux and rejection of the GCD-mems can simultaneously remove both methylene blue and Congo red. In the adsorption, it is appropriate with the pseudo-second-order and Langmuir models corresponding to chemical adsorption and monolayer approaches, as well as physical sieving through the 3D layers of porous channels of GCD-mems during the filtration process. Moreover, the structural stability and sustainability of the PCMs are enhanced during the recycling process, and the use of ethanol in the recycling process further simplifies the process and reduces the cost of the PCMs. Thus, the GCD-mems are encouraged as potential candidates that can be applied directly in the removal of dyes from the wastewater of textile industries or selective dialysis applications.

Research Audit on Clinical Utility of Dimensional Disruptive Mood and Behavior Psychopathologies in Child and Adolescent Psychiatry Practice.

To investigate the utility of dimensional psychopathologies of disruptive mood and behavior disorders (DBDs) by applying latent profile analysis (LPA) for characterization of youth referred to the tertiary outpatient clinic of child and adolescent psychiatry clinic and pharmacological treatment choices. One hundred fifty-eight children and adolescents with significant DBDs symptoms participated. Core dimensional psychopathologies of DBDs (irritability, callous-unemotional trait, and reactive-proactive aggressive behavior), DSM diagnoses, prescribed medications, and behavioral and emotional problems (Child Behavior Checklist, CBCL) were measured at baseline (clinic intake) and at 3-month follow-up. Latent Profile Analysis (LPA) was applied to characterize the study population based on the levels and interrelations among the core dimensional DBDs psychopathologies. Following LPA, the differences in clinical and treatment features between the latent classes were analyzed. LPA revealed two latent classes based on severity of DBDs symptoms. Class 1 (the moderate group) was characterized by relatively low scores on all trans-diagnostic indicators, whereas class 2 (the severe/critical group) showed higher levels of the dimensional psychopathologies and the majority of CBCL subscales. In addition, the severe/critical group was more often prescribed antipsychotic medications, and also experienced more frequent medication changes (addition, increasing the dose, and trial of different medications). Our findings suggested that application of LPA to a cluster of dimensional DBDs psychopathologies may provide valuable characterization of the youths referred to a tertiary outpatient child and adolescent psychiatric clinic, and offer insight into the providers' decision making on psychotropic medications, by overall severity of these psychopathologies rather than by single categorical diagnosis or single externalizing psychopathology.

A general fruit acid chelation route for eco-friendly and ambient 3D printing of metals.

Recent advances in metal additive manufacturing (AM) have provided new opportunities for prompt designs of prototypes and facile personalization of products befitting the fourth industrial revolution. In this regard, its feasibility of becoming a green technology, which is not an inherent aspect of AM, is gaining more interests. A particular interest in adapting and understanding of eco-friendly ingredients can set its important groundworks. Here, we demonstrate a water-based solid-phase binding agent suitable for binder jetting 3D printing of metals. Sodium salts of common fruit acid chelators form stable metal-chelate bridges between metal particles, enabling elaborate 3D printing of metals with improved strengths. Even further reductions in the porosity between the metal particles are possible through post-treatments. A compatibility of this chelation chemistry with variety of metals is also demonstrated. The proposed mechanism for metal 3D printing can open up new avenues for consumer-level personalized 3D printing of metals.

Graphene: Substrate preparation and introduction.

This technical note describes the transfer of continuous, single-layer, pristine graphene to standard Quantifoil TEM grids. We compare the transmission properties of pristine graphene substrates to those of graphene oxide and thin amorphous carbon substrates. Positively stained DNA imaged across amorphous carbon is typically indiscernible and requires metal shadowing for sufficient contrast. However, in a practical illustration of the new substrates properties, positively stained DNA is imaged across pristine graphene in striking contrast without the need of metal shadowing. We go onto discuss technical considerations and the potential applications of pristine graphene substrates as well as their ongoing development.

Direct transfer of alpha-synuclein from neuron to astroglia causes inflammatory responses in synucleinopathies.

Abnormal neuronal aggregation of alpha-synuclein is implicated in the development of many neurological disorders, including Parkinson disease and dementia with Lewy bodies. Glial cells also show extensive alpha-synuclein pathology and may contribute to disease progression. However, the mechanism that produces the glial alpha-synuclein pathology and the interaction between neurons and glia in the disease-inflicted microenvironment remain unknown. Here, we show that alpha-synuclein proteins released from neuronal cells are taken up by astrocytes through endocytosis and form inclusion bodies. The glial accumulation of alpha-synuclein through the transmission of the neuronal protein was also demonstrated in a transgenic mouse model expressing human alpha-synuclein. Furthermore, astrocytes that were exposed to neuronal alpha-synuclein underwent changes in the gene expression profile reflecting an inflammatory response. Induction of pro-inflammatory cytokines and chemokines correlated with the extent of glial accumulation of alpha-synuclein. Together, these results suggest that astroglial alpha-synuclein pathology is produced by direct transmission of neuronal alpha-synuclein aggregates, causing inflammatory responses. This transmission step is thus an important mediator of pathogenic glial responses and could qualify as a new therapeutic target.