Tip-enhanced Raman imaging of plasmon-driven dimerization of 4-bromothiophenol on nickel-decorated gold nanoplate bimetallic nanostructures.

We used tip-enhanced Raman spectroscopy (TERS) to examine plasmon-driven dimerization of 4-bromothiophenol (4-BTP) into thiophenol (TP) and 4,4'-biphenyldithiol (4,4'-BPDT) on Au and Ni@AuNPs. TERS revealed that cross-coupling of these molecular reactants into 4,4'-BPDT occurred primarily on Ni nano islands rather than the surrounding Au on the surface of Ni@AuNPs.

Tip-Enhanced Raman Imaging of Plasmon-Driven Coupling of 4-Nitrobenzenethiol on Au-Decorated Magnesium Nanostructures.

Magnesium nanoparticles (MgNPs) exhibit localized surface plasmon resonances across the ultraviolet, visible, and near-infrared parts of electromagnetic spectrum and are attracting increasing interest due to their sustainability and biocompatibility. In this study, we used tip-enhanced Raman spectroscopy (TERS) to examine the photocatalytic properties of MgNP protected by a thin native oxide layer and their Au-modified bimetallic analogs produced by partial galvanic replacement, Au-MgNPs. We found no reduction of 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobisbenzene (DMAB) when a Au-coated tip was placed in contact with a self-assembled monolayer of 4-NBT molecules adsorbed on MgNPs alone. However, decorating Mg with Au made these bimetallic structures catalytically active. The DMAB signal signature of photocatalytic activity was more delocalized around AuNPs attached to Mg than around AuNPs on a Si substrate, indicating coupling between the Mg core and Au decorations. This report on photocatalytic activity of a bimetallic structure including plasmonic Mg paves the way for further catalyst architectures benefiting from Mg's versatility and abundance.

Zn-ion Batteries: Charge Storing Mechanism and Development Challenges.

Improving the energy share of renewable energy technologies is the only solution to reduce greenhouse gas emissions and air pollution. The high-performing green battery energy storage technologies are critical for storing energy to address the intermittent nature of renewable energy resources. In recent years, aqueous batteries, particularly Zn-ion batteries (ZIBs), have achieved and shown great potential for stationary energy storage systems owing to their low cost and safer operation. However, the practical applications of the ZIBs have significantly been impeded due to the gap between the breakthroughs achieved in academic research and industrial developments. The present review discusses the ZIB's advantages, possibilities, and shortcomings for stationary energy storage systems. The Review begins with a brief introduction to the ZIBs and their charge storage mechanisms based on the structural properties of cathode materials. The scientific and technical challenges that obstruct the commercialization of the ZIBs are discussed in detail concerning their impact on accelerating the utilization of the ZIBs for real-life applications. The final section highlights the outlook on research in this flourishing field.

All Transition Metal Selenide Composed High-Energy Solid-State Hybrid Supercapacitor.

Transition metal selenides (TMSs) have enthused snowballing research and industrial attention due to their exclusive conductivity and redox activity features, holding them as great candidates for emerging electrochemical devices. However, the real-life utility of TMSs remains challenging owing to their convoluted synthesis process. Herein, a versatile in situ approach to design nanostructured TMSs for high-energy solid-state hybrid supercapacitors (HSCs) is demonstrated. Initially, the rose-nanopetal-like NiSe@Cu2 Se (NiCuSe) positive electrode and FeSe nanoparticles negative electrode are directly anchored on Cu foam via in situ conversion reactions. The complementary potential windows of NiCuSe and FeSe electrodes in aqueous electrolytes associated with the excellent electrical conductivity results in superior electrochemical features. The solid-state HSCs cell manages to work in a high voltage range of 0-1.6 V, delivers a high specific energy density of 87.6 Wh kg-1 at a specific power density of 914.3 W kg-1 and excellent cycle lifetime (91.3% over 10 000 cycles). The innovative insights and electrode design for high conductivity holds great pledge in inspiring material synthesis strategies. This work offers a feasible route to develop high-energy battery-type electrodes for next-generation hybrid energy storage systems.

Fluorine Engineered Self-Supported Ultrathin 2D Nickel Hydroxide Nanosheets as Highly Robust and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Urea Oxidation Reactions.

Developing highly efficient noble-metal-free electrocatalysts with a scalable and environmentally friendly synthesis approach remains a challenge in the field of electrocatalytic water splitting. To overcome this problem, self-supported fluorine-modified 2D ultrathin nickel hydroxide (F-Ni(OH)2 ) nanosheets (NSs) for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) are prepared with a scalable and ascendant one-step synthesis route. The enhanced redox activity, electrical conductivity and a great number of exposed active sites of the heterogeneous catalysts improve charge migration for the electrocatalytic reactions. The density of states of the d orbitals of the Ni atoms significantly increases near the Fermi level, thereby indicating that the Ni atoms near the F-dopants promote electrical conduction in the Ni(OH)2 monolayer. The F-Ni(OH)2 electrocatalyst exhibits notable OER and UOR activity with onset potentials of 1.43 and 1.16 V versus RHE, respectively required to reach 10 mA cm-2 , which are comparable to those of commercial noble-metal-based electrocatalysts. With RuCo-OH nanospheres, the settled F-Ni(OH)2 ||RuCo-OH cell requires merely 1.55 and 1.37 V to reach 10 mA cm-2 with superb durability for 24 h in overall water and urea electrolysis, respectively. Overall, high-quality, and efficient noble-metal-free electrocatalysts for overall water and urea electrolysis can be prepared with a simple, scalable, and reproducible preparation method.

Bottom-up Approach for Designing Cobalt Tungstate Nanospheres through Sulfur Amendment for High-Performance Hybrid Supercapacitors.

Nanofabrication of heteroatom-doped metal oxides into a well-defined architecture via a "bottom-up" approach is crucial to overcome the boundaries of the metal oxides for energy storage systems. In the present work, this issue was addressed by developing sulfur-doped bimetallic cobalt tungstate (CoWO4 ) porous nanospheres for efficient hybrid supercapacitors via a single-step, ascendable bottom-up approach. The combined experimental and kinetics studies revealed enhanced electrical conductivity, porosity, and openness for ion migration after amendments of the CoWO4 via sulfur doping. As a result, the sulfur-doped CoWO4 nanospheres exhibited a specific capacity of 248.5 mA h g-1 with outstanding rate capability and cycling stability. The assembled hybrid supercapacitor cell with sulfur-doped CoWO4 nanospheres and activated carbon electrodes could be driven reversibly in a voltage of 1.6 V and exhibited a specific capacitance of 177.25 F g-1 calculated at 1.33 A g-1 with a specific energy of 63.41 Wh kg-1 at 1000 W kg-1 specific power. In addition, the hybrid supercapacitor delivered 94.85 % initial capacitance over 10000 charge-discharge cycles. The excellent supercapacitive performance of sulfur-doped CoWO4 nanospheres may be credited to the sulfur doping and bottom-up fabrication of the electrode materials.

Two-Dimensional Materials for High-Energy Solid-State Asymmetric Pseudocapacitors with High Mass Loadings.

A porous nanostructure and high mass loading are crucial for a pseudocapacitor to achieve a good electrochemical performance. Although pseudocapacitive materials, such as MnO2 and MoS2 , with record capacitances close to their theoretical values have been realized, the achieved capacitances are possible only when the electrode mass loading is less than 1 mg cm-2 . Increasing the mass loading affects the capacitance as electron conduction and ion diffusion become sluggish. Achieving fast ion and electron transport at high mass loadings through all active sites remains a challenge for high-mass-loading electrodes. In this study, 2D MnO2 nanosheets supported on carbon fibers (MnO2 @CF) as well as MoS2 @CF with high mass loadings (6.6 and 7.2 mg cm-2 , respectively) were used in a high-energy pseudocapacitor. These hierarchical 2D nanosheets yielded outstanding areal capacitances of 1187 and 495 mF cm-2 at high current densities with excellent cycling stabilities. A pliable pseudocapacitive solid-state asymmetric supercapacitor was designed using MnO2 @CF and MoS2 @CF as the positive and negative electrodes, respectively, with a high mass loading of 14.2 mg cm-2 . The assembled solid-state asymmetric cell had an energy density of 2.305 mWh cm-3 at a power density of 50 mW cm-3 and a capacitance retention of 92.25 % over 11 000 cycles and a very small diffusion resistance (1.72â€…Ω s-1/2 ). Thus, it is superior to most state-of-the-art reported pseudocapacitors. The rationally designed nanostructured electrodes with high mass loading are likely to open up new opportunities for the development of a supercapacitor device capable of supplying higher energy and power.

Biomechanical Characterization of Cardiomyocyte Using PDMS Pillar with Microgrooves.

This paper describes the surface-patterned polydimethylsiloxane (PDMS) pillar arrays for enhancing cell alignment and contraction force in cardiomyocytes. The PDMS micropillar (µpillar) arrays with microgrooves (µgrooves) were fabricated using a unique micro-mold made using SU-8 double layer processes. The spring constant of the µpillar arrays was experimentally confirmed using atomic force microscopy (AFM). After culturing cardiac cells on the two different types of µpillar arrays, with and without grooves on the top of µpillar, the characteristics of the cardiomyocytes were analyzed using a custom-made image analysis system. The alignment of the cardiomyocytes on the µgrooves of the µpillars was clearly observed using a DAPI staining process. The mechanical force generated by the contraction force of the cardiomyocytes was derived from the displacement of the µpillar arrays. The contraction force of the cardiomyocytes aligned on the µgrooves was 20% higher than that of the µpillar arrays without µgrooves. The experimental results prove that applied geometrical stimulus is an effective method for aligning and improving the contraction force of cardiomyocytes.

A Wireless Pressure Sensor Integrated with a Biodegradable Polymer Stent for Biomedical Applications.

This paper describes the fabrication and characterization of a wireless pressure sensor for smart stent applications. The micromachined pressure sensor has an area of 3.13 × 3.16 mm² and is fabricated with a photosensitive SU-8 polymer. The wireless pressure sensor comprises a resonant circuit and can be used without the use of an internal power source. The capacitance variations caused by changes in the intravascular pressure shift the resonance frequency of the sensor. This change can be detected using an external antenna, thus enabling the measurement of the pressure changes inside a tube with a simple external circuit. The wireless pressure sensor is capable of measuring pressure from 0 mmHg to 230 mmHg, with a sensitivity of 0.043 MHz/mmHg. The biocompatibility of the pressure sensor was evaluated using cardiac cells isolated from neonatal rat ventricular myocytes. After inserting a metal stent integrated with the pressure sensor into a cardiovascular vessel of an animal, medical systems such as X-ray were employed to consistently monitor the condition of the blood vessel. No abnormality was found in the animal blood vessel for approximately one month. Furthermore, a biodegradable polymer (polycaprolactone) stent was fabricated with a 3D printer. The polymer stent exhibits better sensitivity degradation of the pressure sensor compared to the metal stent.

Nanoflake-Modulated La2 Se3 Thin Films Prepared for an Asymmetric Supercapacitor Device.

La2 Se3 nanoflakes were prepared from an aqueous medium by means of a chemical-bath deposition method and were later utilized as a supercapacitor electrode. X-ray diffraction (XRD), Fourier transform Raman (FT Raman), field-emission scanning electron microscopy (FESEM), and contact-angle measurement techniques were used to study the structural, morphological, and wettability properties of La2 Se3 films. The XRD study confirmed the cubic crystal structure of the La2 Se3 film. The surface morphology and wettability studies revealed the nanoflake morphology with a hydrophilic surface, which could be beneficial to electrochemical reactions. The electrochemical performance of the La2 Se3 nanoflakes was evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The La2 Se3 nanoflake electrode exhibited a maximum specific capacitance of 331 F g-1 at a scan rate of 5 mV s-1 . An electrochemical impedance study confirmed that the La2 Se3 nanoflake electrode has a better supercapacitive behavior in an aqueous electrolyte. The asymmetric supercapacitor device based on the La2 Se3 electrode in aqueous electrolyte exhibited good specific capacitance, excellent charge/discharge properties, and superior long-term cycling stability.