Graphene quantum dot based materials for sensing,bio-imaging and energy storage applications: a review

Graphene quantum dots (GQDs) are an attractive nanomaterial consisting of a monolayer or a few layers of graphene having excellent and unique properties. GQDs are endowed with the properties of both carbon dots (CDs) and graphene. This review addresses applications of GQD based materials in sensing, bioimaging and energy storage. In the first part of the review, different approaches of GQD synthesis such as top-down and bottom-up synthesis methods have been discussed. The prime focus of this review is on green synthesis methods that have also been applied to the synthesis of GQDs. The GQDs have been discussed thoroughly for all the aspects along with their potential applications in sensors, biomedicine, and energy storage systems. In particular, emphasis is given to popular applications such as electrochemical and photoluminescence (PL) sensors, electrochemiluminescence (ECL) sensors, humidity and gas sensors, bioimaging, lithium-ion (Li-ion) batteries, supercapacitors and dye-sensitized solar cells. Finally, the challenges and the future perspectives of GQDs in the aforementioned application fields have been discussed.

Graphene quantum dots (GQDs) are an attractive nanomaterial consisting of a monolayer or a few layers of graphene having excellent and unique properties.     

A critical review of silicon nanowire electrodes and their energy storage capacities in Li-ion cells

The electrochemical performances of silicon nanowire (SiNW) electrodes with various nanowire forms, intended as potential negative electrodes for Li-ion batteries, are critically reviewed. The lithium storage capacities, cycling performance, and how the volume expansion is possibly accommodated in these structures are discussed. The SiNW morphology can have a greater impact on the energy storage capacity and cycling performance if the parameters affecting the performance are clearly identified, which is the objective of this review. It is shown that the specific capacity measure is not adequate to truly assess the potential of an electrode and the necessity of the areal capacity measure is highlighted. It is shown that both measures are essential for the assessment of the true potential of a SiNW electrode relative to competing electrodes. Si mass loading in SiNWs has been found to be important for areal and specific capacities. An increase of mass loading of SiNWs is shown to increase the areal capacity significantly, but the specific capacity is found to decrease in thicker Si electrodes. Further, modifications of SiNW electrodes, with coating and doping, have shown significant increases in the performance of these electrodes in Li-ion batteries. The SiNW electrodes, to date, are far below the areal capacity of 3 mA h cm⁻², which may be the minimum threshold capacity for a promising SiNW electrode with respect to Li-ion batteries.

Si nanowire electrodes have great potential as high-capacity anodes for Li-ion batteries. This review provides a comprehensive evaluation of the Li-storage capacity of various Si nanowire electrodes based on both specific and areal capacity.     

Ionic self-assembled organogel polyelectrolytes for energy storage applications

High performance organogel polyelectrolytes were synthesized by super acid catalyst step-growth polycondensation of isatin and the non-activated multiring aromatic p-terphenyl. Subsequently, a chemical modification reaction was carried out to obtained quaternary ammonium functionalized polyelectrolytes through a nucleophilic substitution reaction with (3-bromopropyl)trimethylammonium bromide and potassium carbonate at room temperature. Different functionalization degrees were obtained by controlling the molar ratio of the polymer and the modification agent. The organogel polyelectrolytes were formed due to the high phase segregation and self-assembling observed owing to the amphiphilic character of the material (hydrophobic backbone and hydrophilic fragment grafted). The organogel polyelectrolytes were used to fabricate supercapacitors using two commercial graphite electrodes. These polyelectrolytes displayed good ionic conductivity without the use of another doping agent such as salts, acids or ionic liquids. In this work, a strong correlation of functionalization degree and ionic conductivity of the polyelectrolytes and capacitance of the supercapacitors was observed. The ionic conductivity of the polyelectrolytes reached 0.46 mS cm⁻¹ for the 100% functionalization degree, meanwhile the polyelectrolyte with the 10% functionalization degree shows 0.036 mS cm⁻¹. Li-doped polyelectrolytes showed higher ionic conductivity due the presence of extra ionic charges (2.26 and 0.2 mS cm⁻¹ for the polyelectrolytes with the 100% and 10% of functionalization degree, respectively). The principal novelty of this work lies in the possibility of modulating the ionic conductivity of organogels and the capacitance of supercapacitors by chemical modifications. The capacitance of the supercapacitors was 1.17 mF cm⁻² for the 100% functionalized polyelectrolyte and is higher in comparison with the polyelectrolyte with 10% functionalization degree (0.68 mF cm⁻²) measured at a discharge current of 52 μA cm⁻² by galvanostatic charge discharge technique. Additionally, when lithium salt (lithium triflate) was added, the polyelectrolytes retained a gel consistency, increasing the ionic conductivity and capacitance. For the doped polyelectrolytes, the areal capacitance reaches 1.37 mF cm⁻² for the 100% functionalization degree polyelectrolyte with lithium triflate. These organogel polyelectrolytes open the possibility to design flexible and all solid-state supercapacitors without the risk of leakage.

High performance organogel polyelectrolytes were synthesized by super acid catalyst step-growth polycondensation of isatin and the non-activated multiring aromatic p-terphenyl.     

MXene derivatives: synthesis and applications in energy convention and storage

Transition metal carbides or nitrides (MXene) have shown promising applications in energy convention and storage (ECS), owing to their high conductivity and adjustable surface functional groups. In the past several years, many MXene derivatives with different structures have been successfully prepared and their impressive performance demonstrated in ECS. This review summarizes the progress in the synthesis of MXene and typical Ti₃C₂T_x MXene derivatives with different morphologies, including 0D quantum dots, 1D nanoribbons, 2D nanosheets and 3D nanoflowers. The mechanisms involved and their performance in photocatalysis, electrocatalysis and rechargeable batteries are also discussed. Furthermore, the challenges of MXene derivatives in ECS are also proposed.

MXene derivatives with different morphology and applications in energy convention and storage.     

A SnO2QDs/GO/PPY ternary composite film as positive and graphene oxide/charcoal as negative electrodes assembled solid state asymmetric supercapacitor for high energy storage applications

The work demonstrates tin oxide quantum dots/graphene oxide/polypyrrole (SnO₂QDs/GO/PPY) ternary composite deposited on titanium foil as a positive electrode and graphene oxide (GO)/charcoal on titanium foil as negative electrode separated by polyvinyl alcohol/potassium hydroxide (PVA/KOH) gel-electrolyte as a solid-state asymmetric supercapacitor for high energy storage applications. Here, tin oxide quantum dots (SnO₂QDs) were successfully synthesized by a hydrothermal technique, and SnO₂QDs/GO/PPY ternary composite was synthesized by an in situ method with pyrrole monomer, SnO₂, and GO. A pH value controlled, which maintained the uniform size of SnO₂QDs dispersed on PPY, through GO ternary composite was used for fabricating the asymmetric supercapacitor electrode with the configuration (SnO₂QDs/GO/PPY)/GO/charcoal (85 : 10 : 5). The device achieved the highest specific capacitance of 1296 F g⁻¹, exhibited an energy density of 29.6 W h kg⁻¹ and the highest power density of 5310.26 W kg⁻¹ in the operating voltage from 0 to 1.2 V. The device also possessed excellent reliability and retained the capacitance of 90% after 11 000 GCD cycles. This ternary composite is a prominent material for potential applications in next-generation energy storage and portable electronic devices.

Representation of the synthesis steps of SnO₂QDs/GO/PPY ternary composites and SnO₂QDs/GO/PPY//GO/charcoal asymmetric supercapacitor device.     

Hierarchical Ni–Co–Mn hydroxide hollow architectures as high-performance electrodes for electrochemical energy storage

In this study, hierarchical Ni–Co–Mn hydroxide hollow architectures were successfully achieved via an etching process. We first performed the synthesis of NiCoMn-glycerate solid spheres via a solvothermal route, and then NiCoMn-glycerate as the template was etched to convert into hierarchical Ni–Co–Mn hydroxide hollow architectures in the mixed solvents of water and 1-methyl-2-pyrrolidone. Hollow architectures and high surface area enabled Ni–Co–Mn hydroxide to manifest a specific capacitance of 1626 F g⁻¹ at 3.0 A g⁻¹, and it remained as large as 1380 F g⁻¹ even at 3.0 A g⁻¹. The Ni–Co–Mn hydroxide electrodes also displayed notable cycle performance with a decline of 1.6% over 5000 cycles at 12 A g⁻¹. Moreover, an asymmetric supercapacitor assembled with this electrode exhibited an energy density of 44.4 W h kg⁻¹ at 1650 W kg⁻¹ and 28.5 W h kg⁻¹ at 12 374 W kg⁻¹. These attractive results demonstrate that hierarchical Ni–Co–Mn hydroxide hollow architectures have broad application prospects in supercapacitors.

An effective etching method is developed for the synthesis of hierarchical Ni–Co–Mn hydroxide hollow architectures, which exhibit high performance in electrochemical energy storage.     

An expeditious and efficient bromomethylation of thiols: enabling bromomethyl sulfides as useful building blocks

A facile and highly efficient method for the bromomethylation of thiols, using paraformaldehyde and HBr/AcOH, has been developed, which advantageously minimizes the generation of highly toxic byproducts. The preparation of 22 structurally diverse α-bromomethyl sulfides illustrates the chemo-tolerant applicability while bromo-lithium exchange and functionalization sequences, free radical reductions, and additions of the title compounds demonstrate their synthetic utility.

A new method for the bromomethylation of thiols using paraformaldehyde and HBr/AcOH, minimizes the generation of toxic byproducts. Synthetic utility of α-bromomethyl sulfides was demonstrated through umpolung and free radical chemistry.

Heteroatom halomethylations¹ have proven to be extremely useful for the generation of valuable synthetic intermediates.² Halomethylation of thiols provides synthetically valuable chloromethylated intermediates (chloromethyl sulfides), which are typically prepared by condensation with bromochloromethane in basic media,³ or with HCl and a formaldehyde source (paraformaldehyde, polyoxymethylene, etc.).⁴ While chloromethyl sulfides have been traditionally used as alkylating reagents, the analogous bromomethyl counterparts offer superior electrophilicity, recognized since the earliest report describing their syntheses using hydrogen bromide and paraformaldehyde,⁵ yet they are often overlooked in this role. Moreover, the reactivity scope of bromomethyl thiol derivatives remains largely unexplored, despite a potentially broader synthetic range (e.g. for the generation of organometallics by metal–halogen exchange).⁶Other methods for the generation of bromomethylated thiol derivatives consist of replacing hydrogen bromide gas with concentrated aqueous hydrobromic acid, along with a formaldehyde source (usually paraformaldehyde),⁷ or by using dibromomethane⁸ in basic media.⁹ Two or three-step procedures consisting of hydroxymethylation followed by substitution have also been developed.¹⁰ A desilylative rearrangement of α-TMS sulfides has also been used for the generation of bromomethylsulfides.¹¹As part of our interest in the preparation and application of structurally diverse sulfur-based building blocks,¹² we investigated the preparation of benzyl(bromomethyl)sulfane (2a), previously used as an olefination reagent.¹³ However, several attempts to prepare 2a through exposure of benzylmercaptan (1a) to paraformaldehyde and hydrobromic acid,^7b led to a ca. 1.5 : 1 mixture of 2a (32%) and bis(benzylthio)methane 3a (21%, Scheme 1a). Iterations of the experiment always delivered important and variable amounts of the dithioacetal by-product 3a. On the other hand, an alternate approach to the bromomethylation of a cyclohexanethiol bromomethyl derivative 2b, using dibromomethane and K₂CO₃, resulted in trace amounts of the dithioacetal derivative 3b only (Scheme 1b).¹⁴Open in a separate windowScheme 1Attempts for the bromomethylation of 1a or 1b under (a) acidic or (b) basic media. (c) and (d) A highly efficient and direct approach for thiol bromomethylation (this work).HBr/AcOH is a convenient hydrogen bromide source that minimizes exposure to risky set-ups and has been employed as a surrogate to highly corrosive and toxic hydrogen bromide gas in numerous applications.¹⁵ Although this reagent has been used previously in the generation of bromomethyl sulfides, installation of the methylene bridge required first a S-pivaloxymethylation of a mercaptan, followed by cleavage by HBr/AcOH.¹⁶Surprisingly, sequential exposure of thiols 1a or 1b to paraformaldehyde and HBr/AcOH,¹⁷ rapidly delivered bromomethylated derivatives 2a and 2b with outstanding yields (Scheme 1). The simple experimental setup and straightforward purification procedure offer methodological utility; in most cases extraction with a low-boiling point hydrocarbon such as pentane or hexanes is sufficient to recover the material in high purity (>95%).¹⁸ Traces of impurities can be easily discarded through bulb-to-bulb vacuum distillation.The reaction scope was explored with a series of structurally diverse thiols (19 was prepared satisfactorily in 76% yield. Fluorinated bromomethyl 2e has been used for the preparation of fluorinated surfactants,^10a,20 which some exhibit antimicrobial activity. As a previous method involves a 2-step sequence involving thiol hydroxymethylation and substitution by PBr₃, our method directly delivered 2e in 88% yield.Thiol bromomethylation with HBr/paraformaldehyde^a

Nickel-adsorbed two-dimensional Nb2C MXene for enhanced energy storage applications

Owing to the tremendous energy storage capacity of two-dimensional transition metal carbides (MXenes), they have been efficiently utilized as a promising candidate in the field of super-capacitors. The energy storage capacity of MXenes can be further enhanced using metal dopants. Herein, we have reported the synthesis of pristine and nickel doped niobium-carbide (Nb₂C) MXenes, their computational and electrochemical properties. Upon introduction of nickel (Ni) the TDOS increases and a continuous DOS pattern is observed which indicates coupling between Ni and pristine MXene. The alterations in the DOS, predominantly in the nearby region of the Fermi level are profitable for our electrochemical applications. Additionally, the Ni-doped sample shows a significant capacitive performance of 666.67 F g⁻¹ which can be attributed to the additional active sites generated by doping with Ni. It is worth noting that doped MXenes exhibited a capacitance retention of 81% up to 10 000 cycles. The current study unveils the opportunities of using MXenes with different metal dopants and hypothesize on their performance for energy storage devices.

Owing to the tremendous energy storage capacity of two-dimensional transition metal carbides (MXenes), they have been efficiently utilized as a promising candidate in the field of super-capacitors.     

Low-cost diatomite supported binary transition metal sulfates: an efficient reusable solid catalyst for biodiesel synthesis

Using a simple method of impregnation and then calcination, diatomite supported binary transition metal sulfates (Fe and Zr, designated as Fe₂(SO₄)₃&Zr(SO₄)₂@diatomite) were prepared and used as a catalyst in the preparation of renewable biofuels. The synthesised Fe₂(SO₄)₃&Zr(SO₄)₂@diatomite catalyst (Fe₂(SO₄)₃ : Zr(SO₄)₂ : diatomite = 1 : 2 : 6, mass ratio) was thoroughly characterised using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, microbeam X-ray fluorescence (μ-XRF) spectroscopy and thermogravimetric analysis (TG). The results demonstrated that the sulfate was successfully loaded onto the diatomite with a uniform distribution. The N₂ adsorption/desorption analysis indicated that the catalyst''s specific surface area was 1.54 m² g⁻¹. The catalyst exhibited outstanding performance in the preparation of renewable biofuel (biodiesel) from waste fatty acids and the optimal parameters were methanol-to-oil 1.25 : 1, reaction temperature 70 °C, catalyst concentration 10 wt%, reaction time 4 h. The conversion was found to reach 98.90% under optimal parameters, which is better than that of Fe₂(SO₄)₃·xH₂O, Zr(SO₄)₂·4H₂O, Fe₂(SO₄)₃@diatomite and Zr(SO₄)₂@diatomite. Moreover, the catalyst can be recycled by simple filtration and reused for three cycles after regeneration without noticeable reduction in catalytic activity.

A new catalyst: diatomite supported binary transition metal sulfates (Fe₂(SO₄)₃ and Zr(SO₄)₂) was prepared. It exhibited excellent catalytic activity in the synthesis of biodiesel from waste fatty acids (conversion close to 100%).     

Research progress in transition metal chalcogenide based anodes for K-ion hybrid capacitor applications: a mini-review

Metal ion capacitors have gained a lot of interest as a new kind of capacitor-battery hybrid energy storage system because of their high power density while maintaining energy density and a long lifetime. Potassium ion hybrid capacitors (PIHCs) have been suggested as possible alternatives to lithium-ion/sodium-ion capacitors because of the plentiful potassium supplies, and their lower standard electrode potential and low cost. However, due to the large radius of the potassium ion, PIHCs also face unsatisfactory reaction kinetics, low energy density, and short lifespan. Recently, transition metal chalcogenide (TMC)-based materials with distinctive structures and fascinating characteristics have been considered an emerging candidate for PIHCs, owing to their unique physical and chemical properties. This mini-review mainly focuses on the recent research progress on TMC-based materials for the PIHC applications summarized. Finally, the existing challenges and perspectives are given to improve further and construct advanced TMC-based electrode materials.

Metal ion capacitors have gained a lot of interest as a new kind of capacitor-battery hybrid energy storage system because of their high power density while maintaining energy density and a long lifetime.     

Synergy ascension of SnS/MoS2 binary metal sulfides on initial coulombic efficiency and stable capacity for lithium storage

Numerous efforts have been devoted to capability improvement and cycling stability in the past decades, and these performances have been significantly enhanced. Low initial coulombic efficiency is still a problem in the metal sulfide-based anode materials. This study developed a strategy to achieve high initial coulombic efficiency and superior capacity retention by interpenetrating binary metal sulfides of SnS and MoS₂ in a conductive carbon matrix. The synergy ascension of electrochemical performances for the metal sulfides is attributed to their mutual impeding effects on coarsening of metal grains and the capsule-shaped coating structure embedded in the carbon sheet architecture. The SnS/MoS₂/C composite was prepared by a simple NaCl template-assisted ball milling method, and showed excellent electrochemical performances in terms of a high initial coulombic efficiency up to 90.2% and highly stable reversibility with a specific capacity of 515.4 mA h g⁻¹ after 300 cycles at 1.0 A g⁻¹. All of these characteristics suggest that the proposed materials are superior among the previously reported metal sulfide-based anode materials for lithium-ion batteries.

Binary metal sulfides of SnS and MoS₂ interpenetrated in carbon sheets achieve high initial coulombic efficiency and superior capacity retention.     

Molecular dynamics simulations of phase change materials for thermal energy storage: a review

Phase change materials (PCM) have had a significant role as thermal energy transfer fluids and nanofluids and as media for thermal energy storage. Molecular dynamics (MD) simulations, can play a significant role in addressing several thermo-physical problems of PCMs at the atomic scale by providing profound insights and new information. In this paper, the reviewed research is classified into five groups: pure PCM, mixed PCM, PCM containing nanofillers, nano encapsulated PCM, and PCM in nanoporous media. A summary of the equilibrium and non-equilibrium MD simulations of PCMs and their results is presented as well. The primary results of the simulated systems are demonstrated to be efficient in manufacturing phase change materials with better thermal energy storage features. The goals of these studies are to achieve higher thermal conductivity, higher thermal capacity, and lower density change, determine the melting point, and understand the molecular behaviors of PCM composites. A molecular dynamics-based grouping (PCM simulation table) was presented that is very useful for the future roadmap of PCM simulation. In the end, the PCFF force field is presented in detail and a case problem is studied for more clarity. The results show that simulating the PCMs with a similar strategy could be performed systematically. Results of investigations of thermal conductivity enhancement showed that this characteristic can be increased at the nano-scale by the orientation of PCM molecules.

Phase change materials (PCM) have had a significant role as thermal energy transfer fluids and nanofluids and as media for thermal energy storage.     

Moisture affinity of HDPE/phase-change material composites for thermal energy storage applications

Moisture adsoprtion can degrade the structural integrity of thermal energy storage devices and can negatively impact the capacity and charging/discharging behaviour. Steady-state and transient experiments are conducted at various operating temperatures to evaluate the moisture affinity of organic phase-change material (PCM) shape stabilized with high-density polyethylene (HDPE).

A composite HDPE/PCM filament for 3D printing thermal energy storage systems is naturally hydrophobic.     

Janus transition metal dichalcogenides in combination with MoS2 for high-efficiency photovoltaic applications: a DFT study

Exotic features of two-dimensional materials have been demonstrated, making them particularly appealing for both photocatalytic and photovoltaic applications. van der Waals corrected density functional theory calculations were performed on AAII-Se MoSSe, AAII-Te MoSTe, and AAII-Se WSSe heterostructures in this study. Our findings reveal that the heterostructures have high stability due to the tiny lattice mismatch and binding energy, which is extremely favorable for epitaxial growth of these heterostructures. According to the electronic band gap calculation, AAII-Se MoSSe and AAII-Se WSSe are semiconducting materials, while AAII-Te MoSTe has metallic properties. Interestingly, all three heterostructures have type II band gap alignment, which is advantageous for photovoltaic and photocatalytic applications. Furthermore, it was discovered that AAII-Se MoSSe and AAII-Se WSSe heterostructures exhibit high power conversion efficiency of up to 12.15% and 9.37%, respectively. Based on these intriguing features, the two heterostructures are excellent prospects for photovoltaic applications. The heterostructures have no appropriate band edge sites for overall water splitting at pH = 0, but they are good for the oxygen evolution process. It is feasible to alter the position of the band edges using strain resulting in improved overall water splitting by the heterostructures.

MoS₂/Janus TMDC heterostructure stacking patterns with different stacking orientations.     

Vanillin decorated chitosan as electrode material for sustainable energy storage

Energy storage materials made from bioresources are crucial to fulfil the need for truly sustainable energy storage. In this work, vanillin, being a lignin-derived molecule, is coupled to chitosan, a biobased polymer backbone, and used as a redox active electrode material. The structure of those electrodes is highly defined, leading to better product security than in lignin based electrodes, which have been presented as sustainable electrodes in the past. With over 60% of saccharide units in chitosan functionalised by vanillin, the concentration of redox functionalities in the copolymer is significantly higher than in lignin materials. Composites with carbon black require no further binders or additives to be used as electrode material and show reversible charge storage up to 80 mA h g⁻¹ (respective to the total electrode material) and good stability. Consequently, these electrodes are amongst the best performing electrodes made from regrown organic matter.

To replace dangerous and rare components in battery electrodes, more sustainable energy storage materials made from biowaste and wood-based vanillin are presented.     

Polytriphenylamine composites for energy storage electrodes: effect of pendant vs. backbone polymer architecture of the electroactive group

Polymers are an increasingly used class of materials in semiconductors, photovoltaics and energy storage. Polymers bearing triphenylamine (TPA) or its derivatives in their structures have shown promise for application in electrochemical energy storage devices. The aim of this work is to systematically synthesize polymers bearing TPA units either as pendant groups or directly along the backbone of the polymer and evaluate their performance as electrochemical energy storage electrode materials. The first was obtained via radical polymerization of an acrylate monomer bearing TPA as a side group, resulting in a non-conjugated polymer with individual redox active sites (rP). The latter was obtained by oxidative polymerization of a substituted TPA, resulting in a conjugated polymer with TPA units along its backbone (cP). These polymers were then developed into electrodes by separately blending them with multi-wall carbon nanotubes (rC and cC). The electrodes were characterized and their charge storage stability and mechanical properties were investigated for up to 1000 cycles by cyclic voltammetry, galvanostatic charge–discharge measurements and nanoindentation. The results show that cC offers a higher initial charge capacity than rC as well as improved carbon nanotube dispersion due to its conjugated structure. Although the improved dispersion results in a higher elastic modulus for cC (compared to rC), the stiffer nature of cP made it more vulnerable to degrade upon repetitive volumetric change, while with rP, the decoupled acrylate monomer remained more protected when its redox active units of TPA underwent charge–discharge cycling.

Interaction between (a) CNT-rP-CNT with CNTs sliding next to each other, (b) CNT-cP-CNT with CNTs repulsed via steric hinderance.     

Surface-assembled non-noble metal nanoscale Ni-colloidal thin-films as efficient electrocatalysts for water oxidation

A highly operative and inexpensive water oxidation scheme using an efficient nanoscale electrocatalyst is vastly demanded for optimum H₂ production, CO₂ reduction, and has attracted increased attention for chemical energy conversion. We present here a simple route to make efficient electrocatalytic colloidal nanoparticles of nickel out of mere metal ions in a simple borate buffer system. The simple and annealed Ni-colloidal nanoparticles (Ni-CNPs) resulted in a facile transformation into ultrafine films, which further activated the catalysts, while initiating OER just at the overpotential η = 250 mV (1.48 V vs. RHE) under benign conditions. They also showed high porosity and favorable kinetics while displaying impressive Tafel slopes of just 51 mV dec⁻¹, and a high TOF value of 0.79 s⁻¹ at 0.35 V was observed for Ni-CNPs/FTO₅₀₀. These electrocatalysts also showed long-term stability during the bulk water electrolysis experiment conducted for a continuous 20 hours without notable catalytic degradation, which ensures their economic benefits. The electrochemical data, CVs, kinetic study, short-term durability, extended catalytic stability, SEM analysis, and other supporting data provide compelling evidence that these non-precious, metal-based, electroactive, catalytic, colloidal thin-films (simple and annealed) with nanoscale morphological attributes presented promising catalytic performance under the conditions used herein.

Highly applied and accessible electrocatalytic system derived from simple Ni-colloids has been explored to facilely derive kinetically sluggish water oxidation reaction. Ni-catalysts also present well-balanced kinetics of OER and high durability.     

Transvenous low energy internal cardioversion for atrial fibrillation: a review of clinical applications and future developments

Low energy internal atrial cardioversion can be performed by delivering biphasic shocks between transvenous catheters positioned within the cardiac chambers or great vessels. Delivery of shocks results in effective cardioversion at energies < 6-10 J and the procedure can be effective even when external cardioversion has failed. Shock induced discomfort varies from patient to patient, but the procedure can be usually performed without general anesthesia and eventually under mild sedation. Nevertheless, tolerability has to be improved by obtaining a substantial reduction in defibrillating thresholds. With regard to safety, delivery of shocks for defibrillating the atria implies a potential risk of inducing ventricular fibrillation; to minimize this risk, shock delivery must be synchronous to the QRS and should be avoided during rapid RR cycles (< 300 ms). Presently, transvenous low energy cardioversion is an investigational procedure, but a widening of indications is expected in the near future. The cost of the procedure, which remains invasive and requires a brief hospital stay, must be balanced with the benefit of restoring sinus rhythm and the possibility of maintaining sinus rhythm for the medium- to long-term. Experimental and clinical investigations of low energy internal cardioversion have resulted in the development of devices for atrial defibrillation whose clinical role and cost-benefit ratio is currently under evaluation.     

Liquid metal bath as conformable soft electrodes for target tissue ablation in radio-frequency ablation therapy

Background: Radio-frequency ablation has been an important physical method for tumor hyperthermia therapy. The conventional rigid electrode boards are often uncomfortable and inconvenient for performing surgery on irregular tumors, especially for those tumors near the joints, such as ankles, knee-joints or other facets like finger joints.

Material and methods: We proposed and demonstrated a highly conformable tumor ablation strategy through introducing liquid metal bath as conformable soft electrodes. Different heights of liquid metal bath electrodes were adopted to perform radio-frequency ablation on targeted tissues. Temperature and ablation area were measured to compare the ablation effect with plate metal electrodes.

Results: The recorded temperature around the ablation electrode was almost twice as high as that with the plate electrode and the effective ablated area was 2–3 fold larger in all the mimicking situations of bone tumors, span-shaped or round-shaped tumors. Another unique feature of the liquid metal electrode therapy is that the incidence of heat injury was reduced, which is a severe accident that can occur during the treatment of irregular tumors with plate metal boards.

Conclusions: The present method suggests a new way of using soft liquid metal bath electrodes for targeted minimally invasive tumor ablation in future clinical practice.