Electrostatic-induced assembly of graphene-encapsulated carbon@nickel-aluminum layered double hydroxide core-shell spheres hybrid structure for high-energy and high-power-density asymmetric supercapacitor

Achieving high energy density while retaining high power density is difficult in electrical double-layer capacitors and in pseudocapacitors considering the origin of different charge storage mechanisms. Rational structural design became an appealing strategy in circumventing these trade-offs between energy and power densities. A hybrid structure consists of chemically converted graphene-encapsulated carbon@nickel-aluminum layered double hydroxide core–shell spheres as spacers among graphene layers (G-CLS) used as an advanced electrode to achieve high energy density while retaining high power density for high-performance supercapacitors. The merits of the proposed architecture are as follows: (1) CLS act as spacers to avoid the close restacking of graphene; (2) highly conductive carbon sphere and graphene preserve the mechanical integrity and improve the electrical conductivity of LDHs hybrid. Thus, the proposed hybrid structure can simultaneously achieve high electrical double-layer capacitance and pseudocapacitance resulting in the overall highly active electrode. The G-CLS electrode exhibited high specific capacitance (1710.5 F g−1 at 1 A g−1) under three-electrode tests. An ASC fabricated using the G-CLS as positive electrode and reduced graphite oxide as negative electrode demonstrated remarkable electrochemical performance. The ASC device operated at 1.4 V, and delivered a high energy density of 35.5 Wh kg−1 at a 670.7 W kg−1 power density at 1 A g−1 with an excellent rate capability, as well as a robust long-term cycling stability of up to 10 000 cycles

A novel approach to fabricate carbon-sphere-intercalated holey graphene electrode for high-energy-density electrochemical capacitors

Desirable porous structure and huge ion-accessible surface area are crucial for rapid electronic and ionic pathway electrodes in high-performance graphene-based electrochemical capacitors. However, graphene nanosheets tend to aggregate and restack because of van der Waals interaction among graphene sheets, resulting in the loss of ion-accessible surface area and unsatisfactory electrochemical performance. To resolve this daunting challenge, a novel approach is developed for the self-assembly of holey graphene sheets intercalated with carbon spheres (H-GCS) to obtain freestanding electrodes by using a simple vacuum filtration approach and a subsequent KOH activation process. Through the introduction of carbon spheres as spacers, the restacking of reduced graphene oxide (rGO) sheets during the filtration process is mitigated efficiently. Pores on rGO sheets produced by subsequent KOH activation also provide rapid ionic diffusion kinetics and high ion-accessible electrochemical surface area, both of which favor the formation of electric double-layer capacitance. Furthermore, a higher degree of graphitization of CSs in H-GCS thin film improves the electrical conductivity of the H-GCS electrode. The H-GCS electrode exhibits 207.1 F g−1 of specific capacitance at a current density of 1 A g−1 in 6 M KOH aqueous electrolyte. Moreover, the symmetric electrochemical capacitor assembled with H-GCS electrodes and organic electrolyte is capable of delivering a maximum energy density of 29.5 Wh kg−1 and a power density of 22.6 kW kg−1

Three-Dimensional Self-Standing and Conductive MnCO3@Graphene/CNT Networks for Flexible Asymmetric Supercapacitors

The practical applications of flexible supercapacitor depend strongly on the successful fabrication of advanced electrode materials with high electrochemical performance. Herein, three-dimensional conductive network-based self-standing MnCO3@graphene/CNT hybrid film fabricated through a combination of a hydrothermal method and vacuum filtration for flexible solid-state supercapacitors is reported. The MnCO3@graphene structure is embedded in a CNT network, in which monodispersed MnCO3 nanorod is well confined in graphene nanosheets. This hierarchical structure provides rapid electron/electrolyte ion transport pathways and exhibits excellent structural stability, resulting in rapid kinetics and a long life cycle. The MnCO3@graphene/CNT electrode delivers high specific capacity (467.2 F g–1 at 1 A g–1). Asymmetric supercapacitor (ASC) devices are assembled with the MnCO3@graphene/CNT film as positive electrode and activated carbon/carbon cloth as negative electrode, which exhibits a high energy density of 27 W h kg–1. Remarkably, 93% capacitance retention is obtained for the ASC devices after 6000 cycles

Cu/CuO@ZnO Hollow Nanofiber Gas Sensor: Effect of Hollow Nanofiber Structure and P–N Junction on Operating Temperature and Sensitivity

For the fast and easy detection of carbon monoxide (CO) gas, it was necessary to develop a CO gas sensor to operate in low temperatures. Herein, a novel Cu/CuO-decorated ZnO hollow nanofiber was prepared with the electrospinning, calcination, and photodeposition methods. In the presence of 100 ppm CO gas, the Cu/CuO-photodeposited ZnO hollow nanofiber (Cu/CuO@ZnO HNF) showed twice higher sensitivity than that of pure ZnO nanofiber at a relatively low working temperature of 300◦ C. The hollow structure and p–n junction between Cu/CuO and ZnO would be considered to contribute to the enhancement of sensitivity to CO gas at 300◦ C due to the improved specific surface area and efficient electron transfer. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. T.1

Toe Tissue Transfer for Reconstruction of Damaged Digits due to Electrical Burns

BackgroundElectrical burns are one of the most devastating types of injuries, and can be characterized by the conduction of electric current through the deeper soft tissue such as vessels, nerves, muscles, and bones. For that reason, the extent of an electric burn is very frequently underestimated on initial impression.MethodsFrom July 1999 to June 2006, we performed 15 cases of toe tissue transfer for the reconstruction of finger defects caused by electrical burns. We performed preoperative range of motion exercise, early excision, and coverage of the digital defect with toe tissue transfer.ResultsWe obtained satisfactory results in both functional and aesthetic aspects in all 15 cases without specific complications. Static two-point discrimination results in the transferred toe cases ranged from 8 to 11 mm, with an average of 9.5 mm. The mean range of motion of the transferred toe was 20° to 36° in the distal interphalangeal joint, 16° to 45° in the proximal interphalangeal joint, and 15° to 35° in the metacarpophalangeal joint. All of the patients were relatively satisfied with the function and appearance of their new digits.ConclusionsThe strategic management of electrical injury to the hands can be both challenging and complex. Because the optimal surgical method is free tissue transfer, maintenance of vascular integrity among various physiological changes works as a determining factor for the postoperative outcome following the reconstruction

Potential effectiveness of digital therapeutics specialized in executive functions as adjunctive treatment for clinical symptoms of attention-deficit/hyperactivity disorder: a feasibility study

IntroductionThe role of digital therapeutics (DTx) in the effective management of attention deficit/hyperactivity disorder (ADHD) is beginning to gain clinical attention. Therefore, it is essential to verify their potential efficacy.MethodWe aimed to investigate the improvement in the clinical symptoms of ADHD by using DTx AimDT01 (NUROW) (AIMMED Co., Ltd., Seoul, Korea) specialized in executive functions. NUROW, which consists of Go/No-go Task- and N-Back/Updating-based training modules and a personalized adaptive algorithm system that adjusts the difficulty level according to the user’s performance, was implemented on 30 Korean children with ADHD aged 6 to 12 years. The children were instructed to use the DTx for 15 min daily for 4 weeks. The Comprehensive attention test (CAT) and Childhood Behavior Checklist (CBCL) were used to assess the children at baseline and endpoint. In contrast, the ADHD-Rating Scale (ARS) and PsyToolkit were used weekly and followed up at 1 month, for any sustained effect. Repeated measures ANOVA was used to identify differences between the participants during visits, while t-tests and Wilcoxon signed-rank tests were used to identify changes before and after the DTx.ResultsWe included 27 participants with ADHD in this analysis. The ARS inattention (F = 4.080, p = 0.010), hyperactivity (F = 5.998. p < 0.001), and sum (F = 5.902, p < 0.001) significantly improved. After applying NUROW, internalized (t = −3.557, p = 0.001, 95% CI = −3.682-−0.985), other (Z = −3.434, p = 0.001, effect size = −0.661), and sum scores (t = −3.081, p = 0.005, 95% CI = −10.126-−2.022) were significantly changed in the CBCL. The overall effect was confirmed in the ARS sustained effect analysis even after 1 month of discontinuing the DTx intervention.DiscussionAccording to caregivers, the findings indicate that DTx holds potential effect as an adjunctive treatment in children with ADHD, especially in subjective clinical symptoms. Future studies will require detailed development and application targeting specific clinical domains using DTx with sufficient sample sizes.Clinical trial registration: KCT0007579