Hybrid Materials: A Metareview.

The field of hybrid materials has grown so wildly in the last 30 years that writing a comprehensive review has turned into an impossible mission. Yet, the need for a general view of the field remains, and it would be certainly useful to draw a scientific and technological map connecting the dots of the very different subfields of hybrid materials, a map which could relate the essential common characteristics of these fascinating materials while providing an overview of the very different combinations, synthetic approaches, and final applications formulated in this field, which has become a whole world. That is why we decided to write this metareview, that is, a review of reviews that could provide an eagle's eye view of a complex and varied landscape of materials which nevertheless share a common driving force: the power of hybridization.

Polyoxometalate-Decorated Gold Nanoparticles Inhibit ß-Amyloid Aggregation and Cross the Blood-Brain Barrier in a µphysiological Model.

Alzheimer's disease is characterized by a combination of several neuropathological hallmarks, such as extracellular aggregates of beta amyloid (Aß). Numerous alternatives have been studied for inhibiting Aß aggregation but, at this time, there are no effective treatments available. Here, we developed the tri-component nanohybrid system AuNPs@POM@PEG based on gold nanoparticles (AuNPs) covered with polyoxometalates (POMs) and polyethylene glycol (PEG). In this work, AuNPs@POM@PEG demonstrated the inhibition of the formation of amyloid fibrils, showing a 75% decrease in Aß aggregation in vitro. As it is a potential candidate for the treatment of Alzheimer's disease, we evaluated the cytotoxicity of AuNPs@POM@PEG and its ability to cross the blood-brain barrier (BBB). We achieved a stable nanosystem that is non-cytotoxic below 2.5 nM to human neurovascular cells. The brain permeability of AuNPs@POM@PEG was analyzed in an in vitro microphysiological model of the BBB (BBB-on-a-chip), containing 3D human neurovascular cell co-cultures and microfluidics. The results show that AuNPs@POM@PEG was able to cross the brain endothelial barrier in the chip and demonstrated that POM does not affect the barrier integrity, giving the green light to further studies into this system as a nanotherapeutic.

Polyoxometalate-Stabilized Silver Nanoparticles and Hybrid Electrode Assembly Using Activated Carbon.

The intersection between the field of hybrid materials and that of electrochemistry is a quickly expanding area. Hybrid combinations usually consist of two constituents, but new routes toward more complex and versatile electroactive hybrid designs are quickly emerging. The objective of the present work is to explore novel triple hybrid material integrating polyoxometalates (POMs), silver nanoparticles (Ag0 NPs), and activated carbon (AC) and to demonstrate its use as a hybrid electrode in a symmetric supercapacitor. The tri-component nanohybrid (AC/POM-Ag0 NPs) was fabricated through the combination of AC with pre-synthesized ∼27 nm POM-protected Ag0 NPs (POM-Ag0 NPs). The POM-Ag0 NPs were prepared using a green electrochemical method and characterized via UV-vis and IR spectroscopy, electron microscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Afterward, the AC/POM-Ag0 NPs ternary nanocomposite material was constructed and characterized. The electrochemical behavior of AC/POM-Ag0 NPs' modified electrodes reveal that the nanomaterial is electroactive and exhibits a moderately higher specific capacitance (81 F/g after 20 cycles) than bare AC electrodes (75 F/g) in a symmetrical supercapacitor configuration in the voltage range 0 to 0.75 V and 20 mV/s, demonstrating the potential use of this type of tri-component nanohybrid for electrochemical applications.

Nanostructured Thick Electrode Strategies toward Enhanced Electrode-Electrolyte Interfaces.

This article addresses the issue of bulk electrode design and the factors limiting the performance of thick electrodes. Indeed, one of the challenges for achieving improved performance in electrochemical energy storage devices (batteries or supercapacitors) is the maximization of the ratio between active and non-active components while maintaining ionic and electronic conductivity of the assembly. In this study, we developed and compared supercapacitor thick electrodes using commercially available carbons and utilising conventional, easily scalable methods such as spray coating and freeze-casting. We also compared different binders and conductive carbons to develop thick electrodes and analysed factors that determine the performance of such thick electrodes, such as porosity and tortuosity. The spray-coated electrodes showed high areal capacitances of 1428 mF cm-2 at 0.3 mm thickness and 2459 F cm-2 at 0.6 mm thickness.

Polyoxometalate intercalated MXene with enhanced electrochemical stability.

MXene/polyoxometalate (POM) hybrids are useful target materials for a variety of applications. Yet, the goal of preparing simple binary hybrids by intercalation of POMs into MXene has not been achieved. We propose and demonstrate here a method to intercalate POMs (phosphotungstate, PW12) into Ti3C2Tx MXene through the interaction between POM anions and pre-intercalated surfactant cations. A variety of quaternary ammonium cations have been used to expand Ti3C2Tx interlayer spacing. Cetyltrimethylammonium cations (CTA+) lead to an expansion of 2 nm while allowing intercalation of a considerable load (10 wt%) thanks to their tadpole-like shape and size. CTAPW12 has a layered structure compatible with Ti3C2Tx. The CTA+-delaminated Ti3C2Tx keeps the large interlayer spacing after being coupled with PW12. The PW12 clusters are dispersed and kept isolated thanks to CTA surfactant and the confinement into Ti3C2Tx layers. The redox reactions in CTA+-delaminated Ti3C2Tx/PW12 are diffusion-controlled, which proves the well-dispersed PW12 clusters are not adsorbed on the surface of Ti3C2Tx particles but within Ti3C2Tx layers. The CTA+- delaminated Ti3C2Tx/PW12 shows superior electrochemical stability (remaining redox active after 5000 cycles) over the other MXene/POM hybrids prepared in this work (inactive after 500 cycles). We associate this improved stability to the effective intercalation of PW12 within Ti3C2Tx layers helped by the CTA cations, as opposed to the external aggregation of PW12 clusters into micro or nanocrystals taking place for the other cations. The results provide a solid guide to help develop high-performance MXene/POM hybrid materials for a variety of applications.

Coherent Integration of Organic Gel Polymer Electrolyte and Ambipolar Polyoxometalate Hybrid Nanocomposite Electrode in a Compact High-Performance Supercapacitor.

We report a gel polymer electrolyte (GPE) supercapacitor concept with improved pathways for ion transport, thanks to a facile creation of a coherent continuous distribution of the electrolyte throughout the electrode. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was chosen as the polymer framework for organic electrolytes. A permeating distribution of the GPE into the electrodes, acting both as integrated electrolyte and binder, as well as thin separator, promotes ion diffusion and increases the active electrode-electrolyte interface, which leads to improvements both in capacitance and rate capability. An activation process induced during the first charge-discharge cycles was detected, after which, the charge transfer resistance and Warburg impedance decrease. We found that a GPE thickness of 12 µm led to optimal capacitance and rate capability. A novel hybrid nanocomposite material, formed by the tetraethylammonium salt of the 1 nm-sized phosphomolybdate cluster and activated carbon (AC/TEAPMo12), was shown to improve its capacitive performance with this gel electrolyte arrangement. Due to the homogeneous dispersion of PMo12 clusters, its energy storage process is non-diffusion-controlled. In the symmetric capacitors, the hybrid nanocomposite material can perform redox reactions in both the positive and the negative electrodes in an ambipolar mode. The volumetric capacitance of a symmetric supercapacitor made with the hybrid electrodes increased by 40% compared to a cell with parent AC electrodes. Due to the synergy between permeating GPE and the hybrid electrodes, the GPE hybrid symmetric capacitor delivers three times more energy density at higher power densities and equivalent cycle stability compared with conventional AC symmetric capacitors.

Dual Carbon Potassium-Ion Capacitors: Biomass-Derived Graphene-like Carbon Nanosheet Cathodes.

Potassium-ion storage devices are attracting tremendous attention for wide-ranging applications on account of their low cost, fast charge transport in electrolytes, and large working voltage. However, developing cost-effective, high-energy electrodes with excellent structural stability to ensure long-term cycling performance is a major challenge. In this contribution, we have derived two different forms of carbon materials from almond shells using different chemical treatments. For instance, hard carbon (HC) and graphene-like activated carbon (AC) nanosheets are developed by employing simple carbonization and chemical activation routes, respectively. The resultant hard carbon (AS-HC) and activated carbon (AS-AC) exhibit outstanding electrochemical performance as negative and positive electrodes in a potassium-ion battery (KIB), respectively, through their tailor-made surface properties. These promising benefits pave a way to construct a biomass-derived carbon potassium-ion capacitor (KIC) by employing AS-HC as the negative electrode and AS-AC as the positive electrode in a K-based electrolyte. The as-fabricated KIC delivers a reasonable specific energy of 105 Wh/kg and excellent cycling life with negligible capacitance fading over 10 000 cycles. This "waste-to-wealth" approach can promote the development of sustainable KICs at low cost and inspire their use for fast-rate K-based energy storage applications.

Fabrication of 3D binder-free graphene NiO electrode for highly stable supercapattery.

Electrochemical stability of energy storage devices is one of their major concerns. Polymeric binders are generally used to enhance the stability of the electrode, but the electrochemical performance of the device is compromised due to the poor conductivity of the binders. Herein, 3D binder-free electrode based on nickel oxide deposited on graphene (G-NiO) was fabricated by a simple two-step method. First, graphene was deposited on nickel foam via atmospheric pressure chemical vapour deposition followed by electrodeposition of NiO. The structural and morphological analyses of the fabricated G-NiO electrode were conducted through Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). XRD and Raman results confirmed the successful growth of high-quality graphene on nickel foam. FESEM images revealed the sheet and urchin-like morphology of the graphene and NiO, respectively. The electrochemical performance of the fabricated electrode was evaluated through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in aqueous solution at room temperature. The G-NiO binder-free electrode exhibited a specific capacity of ≈ 243 C g-1 at 3 mV s-1 in a three-electrode cell. A two-electrode configuration of G-NiO//activated charcoal was fabricated to form a hybrid device (supercapattery) that operated in a stable potential window of 1.4 V. The energy density and power density of the asymmetric device measured at a current density of 0.2 A g-1 were estimated to be 47.3 W h kg-1 and 140 W kg-1, respectively. Additionally, the fabricated supercapattery showed high cyclic stability with 98.7% retention of specific capacity after 5,000 cycles. Thus, the proposed fabrication technique is highly suitable for large scale production of highly stable and binder-free electrodes for electrochemical energy storage devices.

Modification of the Raman Spectra in Graphene-Based Nanofluids and Its Correlation with Thermal Properties.

It is well known that by dispersing nanoparticles in a fluid, the thermal conductivity of the resulting nanofluid tends to increase with the concentration of nanoparticles. However, it is not clear what the mechanism behind this phenomenon is. Raman spectroscopy is a characterization technique connecting the molecular and macroscopic world, and therefore, it can unravel the puzzling effect exerted by the nanomaterial on the fluid. In this work, we report on a comparative study on the thermal conductivity, vibrational spectra and viscosity of graphene nanofluids based on three different amides: N, N-dimethylacetamide (DMAc); N, N-dimethylformamide (DMF); and N-methyl-2-pyrrolidinone (NMP). A set of concentrations of highly stable surfactant-free graphene nanofluids developed in-house was prepared and characterized. A correlation between the modification of the vibrational spectra of the fluids and an increase in their thermal conductivity in the presence of graphene was confirmed. Furthermore, an explanation of the non-modification of the thermal conductivity in graphene-NMP nanofluids is given based on its structure and a peculiar arrangement of the fluid.

Fully printed one-step biosensing device using graphene/AuNPs composite.

Driven by the growing need of simple, cost efficient and flexible sensing systems, we have designed here a fully printed Reduced Graphene Oxide (rGO) based impedimetric sensor for one step sensing of DNA. The DNA sensor was fabricated by stamping of layered rGO and rGO/gold nanoparticles/single stranded DNA (rGO/AuNPs/ssDNA) composites over PET substrates using wax-printing technique. rGO works as an excellent working electrode, while the AuNPs create a suitable environment for ssDNA immobilization. Counter and reference electrodes were previously screen-printed on the plastic substrate, making thus a compact and highly integrated sensing platform. The change in electron transfer resistance after hybridization with a target ssDNA specific of Coxsackie B3 virus was monitored using electrochemical impedance spectroscopy (EIS), finding a linear response in the range of concentrations 0.01-20 µM. The novel, simple and straightforward one-step printing process for fabrication of a biosensing device developed keeps in mind the growing need of large scale device manufacturing. The successful proof-of-concept for the detection of DNA hybridization can be extended to other affinity biosensors, taking advantage of the integration of the bioreceptor on the sensor surface. Such ready-to-use biosensor would lead to a one-step electrochemical detection.

Actualidades en el tratamiento farmacológico a largo plazo de la obesidad. ¿Una opción terapéutica? / Up-to-date in the long-term pharmacological treatment of obesity. A therapeutic option?

Resumen La obesidad es una enfermedad crónica, con afección sistémica y de carácter multifactorial que constituye un grave problema de salud pública, considerada por la Organización Mundial de la Salud una epidemia global. La obesidad es resultado del equilibrio energético positivo por tiempo prolongado, donde la energía derivada de los alimentos excede la energía gastada en la vida cotidiana. En vía de poner fin a este problema de salud pública se han buscado opciones de tratamiento, si bien las modificaciones al estilo de vida, incluida la dieta y el ejercicio, siguen siendo la piedra angular del tratamiento de la obesidad, estas modificaciones no han permitido mantener resultados a largo plazo, por esta razón los medicamentos contra la obesidad se vuelven una opción viable. Son cinco los medicamentos aprobados por la Dirección de Alimentos y Fármacos de Estados Unidos para el tratamiento a largo plazo de la obesidad: orlistat, fentarmina/topiramato de liberación prolongada, lorcarserina, naltrexona/bupropión de liberación prolongada y liraglutida, mismos que han demostrado eficacia y seguridad necesaria para tomarse en cuenta como una opción terapéutica. En este artículo revisaremos la eficacia y seguridad de cada uno los medicamentos aprobados contra la obesidad que se encuentran disponibles.

Abstract Obesity is a chronic disease, with systemic affection and of multifactorial character that constitutes a serious problem of public health, being considered by the World Health Organization a global epidemic. Obesity is the result of a positive energy balance by a long time, where the energy derived from food exceeds the energy expended in everyday life. In order to put an end to this public health problem, treatment options have been sought, although the modifications to the lifestyle included diet and exercise are still the cornerstone of the treatment for obesity, these modifications have not allowed to maintain long-term results; for this reason anti-obesity drugs become a viable option. There are five drugs approved by the FDA nowadays for the long-term treatment of obesity: orlistat, phentermine/topiramate prolonged release, lorcarserin, naltrexone/bupropion prolonged release, and liraglutide, which have shown efficacy and the necessary safety to be taken into account as a therapeutic option. In this article we will review the effectiveness and safety of each of the approved anti-obesity drugs that are available.

Design and Fabrication of Printed Paper-Based Hybrid Micro-Supercapacitor by using Graphene and Redox-Active Electrolyte.

Inspired by future needs of flexible, simple, and low-cost energy storage devices, smart graphene-based micro-supercapacitors on conventional Xerox paper substrates were developed. The use of redox-active species (iodine redox couple) was explored to further improve the paper device's performance. The device based on printed graphene paper itself already had a remarkable maximum volumetric capacitance of 29.6 mF cm-3 (volume of whole device) at 6.5 mA cm-3 . The performance of the hybrid electrode with redox-active potassium iodide at the graphene surface was tested. Remarkably, the hybrid device showed improved volumetric capacitance of 130 mF cm-3 . The maximum energy density for a graphene+KI device in H2 SO4 electrolyte was estimated to be 0.026 mWh cm-3 . Thus, this work offers a new simple, and lightweight micro-supercapacitor based on low-cost printed graphene paper, which will have great applications in portable electronics.

Consumo de sustancias en adolescentes: consideraciones para la práctica médica / Substance use in adolescents: Considerations for medical practice

Resumen El consumo de sustancias entre jóvenes y adolescentes representa un importante problema de salud que se relaciona con lesiones y accidentes graves, discapacidad, trastornos por consumo de sustancias y otros trastornos psiquiátricos, ideación y conducta suicida, conductas sexuales de riesgo, entre otros. Se trata de un problema de salud pública que se ha incrementado de manera considerable en los últimos años. El objetivo de este artículo es revisar los aspectos generales del consumo de sustancias de abuso en adolescentes, como: epidemiología, factores de riesgo, tamizaje, evaluación, diagnóstico, algunas consideraciones para la referencia y tratamiento en un hospital general. Como resultado, se identificó que existen múltiples factores de riesgo del inicio del consumo de sustancias, así como de la aparición de un trastorno por consumo de sustancias. Entre éstos destacan factores individuales, familiares y medioambientales. Asimismo, se identificaron estrategias para la detección temprana, orientación y referencia a tratamiento integral, conocidos como SBIRT (de sus siglas en inglés de Screnning, Brief Intervention, Reference to Treatment). Por último se concluye que la implementación de programas SBIRT en un hospital general es eficaz para mejorar el vínculo entre los servicios del hospital y los programas especializados para tratamiento de los trastornos por consumo de sustancias.

Abstract Substance abuse among young adults and teenagers represents a considerable health issue, as substance use can be associated to serious injuries, accidents, disabilities, substance use and other psychiatric disorders, suicidal ideation and suicidal behavior, sexual risk practices, among others. In the last years, this health problem has been increasing significantly. The objective of this article is to present a review of general aspects of substance abuse in adolescents, such as: epidemiology, risk factors, screening, evaluation, diagnosis, some considerations for referral and general hospital treatment. As a result, it was found that several risk factors have been identified, such as individual, family and environmental factors. Also, strategies for early detection, counsel and reference to integrated treatment known as SBIRT (Screnning, Brief Intervention, Reference to Treatment) were identified. Finally, it is concluded that the implementation of SBIRT programs in general hospital are effective to improve the link between general hospital services to specialized programs for the treatment of substance use disorders.

Ultrathin Hierarchical Porous Carbon Nanosheets for High-Performance Supercapacitors and Redox Electrolyte Energy Storage.

The design of advanced high-energy-density supercapacitors requires the design of unique materials that combine hierarchical nanoporous structures with high surface area to facilitate ion transport and excellent electrolyte permeability. Here, shape-controlled 2D nanoporous carbon sheets (NPSs) with graphitic wall structure through the pyrolysis of metal-organic frameworks (MOFs) are developed. As a proof-of-concept application, the obtained NPSs are used as the electrode material for a supercapacitor. The carbon-sheet-based symmetric cell shows an ultrahigh Brunauer-Emmett-Teller (BET)-area-normalized capacitance of 21.4 µF cm-2 (233 F g-1 ), exceeding other carbon-based supercapacitors. The addition of potassium iodide as redox-active species in a sulfuric acid (supporting electrolyte) leads to the ground-breaking enhancement in the energy density up to 90 Wh kg-1 , which is higher than commercial aqueous rechargeable batteries, maintaining its superior power density. Thus, the new material provides a double profits strategy such as battery-level energy and capacitor-level power density.

Towards flexible solid-state supercapacitors for smart and wearable electronics.

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal-organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field.

Hybrid Graphene-Polyoxometalates Nanofluids as Liquid Electrodes for Dual Energy Storage in Novel Flow Cells.

Solid Hybrid materials abound. But flowing versions of them are new actors in the materials science landscape and in particular for energy applications. This paper presents a new way to deliver nanostructured hybrid materials for energy storage, namely, in the form of nanofluids. We present here the first example of a hybrid electroactive nanofluid (HENFs) combining capacitive and faradaic energy storage mechanisms in a single fluid material. This liquid electrode is composed of reduced graphene oxide and polyoxometalates (rGO-POMs) forming a stable nanocomposite for electrochemical energy storage in novel Nanofluid Flow Cells. Two graphene based hybrid materials (rGO-phosphomolybdate, rGO-PMo12 and rGO-phosphotungstate, rGO-PW12 ) were synthesized and dispersed with the aid of a surfactant in 1 M H2 SO4 aqueous electrolyte to yield highly stable hybrid electroactive nanofluids (HENFs) of low viscosity which were tested in a home-made flow cell under static and continuous flowing conditions. Remarkably, even low concentration rGO-POMs HENFs (0.025 wt%) exhibited high specific capacitances of 273 F/g(rGO-PW12 ) and 305 F/g(rGO-PMo12 ) with high specific energy and specific power. Moreover, rGO-POM HENFs show excellent cycling stability (∼95 %) as well as Coulombic efficiency (∼77-79 %) after 2000 cycles. Thus, rGO-POM HENFs effectively behave as real liquid electrodes with excellent properties, demonstrating the possible future application of HENFs for dual energy storage in a new generation of Nanofluid Flow Cells.

BiVO4 Fern Architectures: A Competitive Anode for Lithium-Ion Batteries.

The development of high-performance anode materials for lithium-ion batteries (LIBs) is currently subject to much interest. In this study, BiVO4 fern architectures are introduced as a new anode material for LIBs. The BiVO4 fern shows an excellent reversible capacity of 769 mAh g-1 (ultrahigh volumetric capacity of 3984 mAh cm-3 ) at 0.12 A g-1 with large capacity retention. A LIB full cell is then assembled with a BiVO4 fern anode and LiFePO4 (LFP, commercial) as cathode material. The device can achieve a capacity of 140 mAh g-1 at 1C rate, that is, 81 % of the capacity of the cathode and maintained to 104 mAh g-1 at a high rate of 8C, which makes BiVO4 a promising candidate as a high-energy anode material for LIBs.

Asymmetric Supercapacitors Based on Reduced Graphene Oxide with Different Polyoxometalates as Positive and Negative Electrodes.

Nanofabrication using a "bottom-up" approach of hybrid electrode materials into a well-defined architecture is essential for next-generation miniaturized energy storage devices. This paper describes the design and fabrication of reduced graphene oxide (rGO)/polyoxometalate (POM)-based hybrid electrode materials and their successful exploitation for asymmetric supercapacitors. First, redox active nanoclusters of POMs [phosphomolybdic acid (PMo12 ) and phosphotungstic acid (PW12 )] were uniformly decorated on the surface of rGO nanosheets to take full advantage of both charge-storing mechanisms (faradaic from POMs and electric double layer from rGO). The as-synthesized rGO-PMo12 and rGO-PW12 hybrid electrodes exhibited impressive electrochemical performances with specific capacitances of 299 (269 mF cm-2 ) and 370 F g-1 (369 mF cm-2 ) in 1 m H2 SO4 as electrolyte at 5 mA cm-2 . An asymmetric supercapacitor was then fabricated using rGO-PMo12 as the positive and rGO-PW12 as the negative electrode. This rGO-PMo12 ∥rGO-PW12 asymmetric cell could be successfully cycled in a wide voltage window up to 1.6 V and hence exhibited an excellent energy density of 39 Wh kg-1 (1.3 mWh cm-3 ) at a power density of 658 W kg-1 (23 mW cm-3 ).

V2O5 encapsulated MWCNTs in 2D surface architecture: Complete solid-state bendable highly stabilized energy efficient supercapacitor device.

A simple and scalable approach has been reported for V2O5 encapsulation over interconnected multi-walled carbon nanotubes (MWCNTs) network using chemical bath deposition method. Chemically synthesized V2O5/MWCNTs electrode exhibited excellent charge-discharge capability with extraordinary cycling retention of 93% over 4000 cycles in liquid-electrolyte. Electrochemical investigations have been performed to evaluate the origin of capacitive behavior from dual contribution of surface-controlled and diffusion-controlled charge components. Furthermore, a complete flexible solid-state, flexible symmetric supercapacitor (FSS-SSC) device was assembled with V2O5/MWCNTs electrodes which yield remarkable values of specific power and energy densities along with enhanced cyclic stability over liquid configuration. As a practical demonstration, the constructed device was used to lit the 'VNIT' acronym assembled using 21 LED's.

Ultrathin Mesoporous RuCo2 O4 Nanoflakes: An Advanced Electrode for High-Performance Asymmetric Supercapacitors.

A new ruthenium cobalt oxide (RuCo2 O4 ) with a unique marigold-like nanostructure and excellent performance as an advanced electrode material has been successfully prepared by a simple electrodeposition (potentiodynamic mode) method. The RuCo2 O4 marigolds consist of numerous clusters of ultrathin mesoporous nanoflakes, leaving a large interspace between them to provide numerous electrochemically active sites. Strikingly, this unique marigold-like nanostructure provided excellent electrochemical performance in terms of high energy-storage capacitance (1469 F g-1 at 6 A g-1 ) with excellent rate proficiency and long-lasting operating cycling stability (ca. 91.3 % capacitance retention after 3000 cycles), confirming that the mesoporous nanoflakes participate in the ultrafast electrochemical reactions. Furthermore, an asymmetric supercapacitor was assembled using RuCo2 O4 (positive electrode) and activated carbon (negative electrode) with aqueous KOH electrolyte. The asymmetric design allowed an upgraded potential range of 1.4 V, which further provided a good energy density of 32.6 Wh kg-1 (1.1 mWh cm-3 ). More importantly, the cell delivered an energy density of 12.4 Wh kg-1 even at a maximum power density of 3.2 kW kg-1 , which is noticeably superior to carbon-based symmetric systems.