Iridium oxide-based non-enzymatic glucose sensor: Superior electro-catalytic performance in biological environmental media.

Nanostructured inorganic materials have potential advantages as glucose-sensing elements in diabetes care, thereby circumventing the need for expensive enzymatic agents. However, many nonenzymatic sensors face challenges related to selectivity and reliability, reducing their efficacy in body fluids. In this study, we introduce an Iridium oxide (IrO2)-based non-enzymatic glucose sensor. This sensor demonstrates exceptional electro-catalytic properties in human serum, characterized by high sensitivity (638 µA µM-1cm2) and a consistent recovery rate (∼104%) across 15 cycles in saline. Furthermore, its impressive performance in human serum, as evidenced by a low relative standard deviation (RSD <1.57%), underscores its applicability in biological matrices such as interstitial fluids. Overall, the IrO2 sensor is a promising, highly reversible, economical, and simple method for detecting glucose in continuous monitoring systems.

Advanced Magnetic Actuation: Harnessing the Dynamics of Sm2Fe17-xCuxN3 Composites.

Recently, there has been an escalating demand for advanced materials with superior magnetic properties, especially in the actuator domain. High coercivity (Hci), an essential magnetic property, is pivotal for programmable shape changes in magnetic actuators and profoundly affects their performance. In this study, a new Sm2Fe17-xCuxN3 magnet with a high Hci was achieved by modifying the temperature of the reduction-diffusion process─lowering it from 900 to 700 °C through the introduction of Cu and finer control over the structure and morphology of the Sm2Fe17-xCuxN3 magnetic component within the actuator composite. Consequently, the Sm2Fe17-xCuxN3 magnet demonstrated a remarkable Hci of 11.5 kOe, eclipsing the value of 6.9 kOe attained by unalloyed Sm2Fe17N3 at reduced temperatures. By capitalizing on the enhanced magnetic properties of the Sm2Fe17-xCuxN3 composite and incorporating poly(ethylene glycol) into the elastomer matrix, we successfully fabricated a robust actuator. This innovative approach harnesses the strengths of hard magnets as actuators, offering stability under high-temperature conditions, precision control, longevity, wireless functionality, and energy efficiency, highlighting the vast potential of hard magnets for a range of applications.

Water-Based Generators with Cellulose Acetate: Uncovering the Mechanisms of Power Generation.

Power generation technologies based on water movement and evaporation use water, which covers more than 70% of the Earth's surface and can also generate power from moisture in the air. Studies are conducted to diversify materials to increase power generation performance and validate energy generation mechanisms. In this study, a water-based generator was fabricated by coating cellulose acetate with carbon black. To optimize the generator, Fourier-transform infrared spectroscopy, specific surface area, zeta potential, particle size, and electrical performance analyses were conducted. The developed generator is a cylindrical generator with a diameter of 7.5 mm and length of 20 mm, which can generate a voltage of 0.15 V and current of 82 µA. Additionally, we analyzed the power generation performance using three factors (physical properties, cation effect, and evaporation environment) and proposed an energy generation mechanism. Furthermore, we developed an eco-friendly and low-cost generator using natural fibers with a simple manufacturing process. The proposed generator can contribute to the identification of energy generation mechanisms and is expected to be used as an alternative energy source in the future.

Enhanced capacitive pressure sensing performance by charge generation from filler movement in thin and flexible PVDF-GNP composite films.

This study introduces an approach to overcome the limitations of conventional pressure sensors by developing a thin and lightweight composite film specifically tailored for flexible capacitive pressure sensors, with a particular emphasis on the medium and high pressure range. To accomplish this, we have engineered a composite film by combining polyvinylidene fluoride (PVDF) and graphite nanoplatelets (GNP) derived from expanded graphite (Ex-G). A uniform sized GNPs with an average lateral size of 2.55av and an average thickness of 33.74 av with narrow size distribution was obtained with a gas-induced expansion of expandable graphite (EXP-G) combined with tip sonication in solvent. By this precisely controlled GNP within the composite film, a remarkable improvement in sensor sensitivity has been achieved, surpassing 4.18 MPa-1 within the pressure range of 0.1 to 1.6 MPa. This enhancement can be attributed to the generation of electric charge from the movement of GNP in the polymer matrix. Additionally, stability testing has demonstrated the reliable operation of the composite film over 1000 cycles. Notably, the composite film exhibits exceptional continuous pressure sensing capabilities with a rapid response time of approximately 100 milliseconds. Experimental validation using a 3 × 3 sensor array has confirmed the accurate detection of specific contact points, thus highlighting the potential of the composite film in selective pressure sensing. These findings signify an advancement in the field of flexible capacitive pressure sensors that offer enhanced sensitivity, consistent operation, rapid response time, and the unique ability to selectively sense pressure.

Anodic Aluminum Oxide-Based Chemi-Capacitive Sensor for Ethanol Gas.

Alcohol ingested by humans can be analyzed via breath tests; however, approximately 1% can be excreted via the skin. In this paper, we present a capacitive sensor using hydrophobically treated anodic aluminum oxide (AAO) capable of detecting alcohol excreted through the epidermis. The degree of hydrophobicity based on the duration of exposure to 3-aminopropyltriethoxysilane vapor comprising a small number of Si-NH2 functional groups on the AAO surface was confirmed and the optimal exposure time was confirmed to be 60 min. The hydrophobized AAO showed a 4.8% reduction in sensitivity to moisture. Simultaneously, the sensitivity of the sensor to ethanol decreased by only 12%. Lastly, the fabricated sensor was successfully operated by attaching it to an ankle-type breathalyzer.

Tuning the sensing responses towards room-temperature hypersensitive methanol gas sensor using exfoliated graphene-enhanced ZnO quantum dot nanostructures.

A suitable and non-invasive methanol sensor workable in ambient temperature conditions with a high response has gained wide interest to prevent detrimental consequences for industrial workers from its low-level intoxication. In this work, we present a tunable and highly responsive ppb-level methanol gas sensor device working at room temperature via a bottom-up synthetic approach using exfoliated graphene sheet (EGs) and ZnO quantum dots (QDs) on an aluminum anodic oxide (AAO) template. It is verified that EGs-supported AAO with a vertical electrode configuration enabled high and fast-responsive methanol sensing. Moreover, the hydroxyl and carboxyl groups of the high surface area EGs and ZnO QDs with a 3.37 eV bandgap efficiently absorbing UV light led to 56 times high response due to the enhanced polarization on the sensor surface compared to non-UV-radiated EGs/AAO at 800 ppb of methanol. The optimal resonance frequency of methanol is determined to be 100 kHz, which could detect methanol with high response of 2.65% at 100 ppm. The limit of detection (LOD) concentration is obtained at 2 ppb level. This study demonstrates the potential of UV-assisted ZnO, EGs, and AAO-based capacitance sensor material for rapidly detecting hazardous gaseous light organic molecules at ambient conditions, and the overall approach can be easily expanded to a novel non-invasive monitoring strategy for light and hazardous volatile organic exposures.

Microstructure Evolution in Plastic Deformed Bismuth Telluride for the Enhancement of Thermoelectric Properties.

Thermoelectric generators are solid-state energy-converting devices that are promising alternative energy sources. However, during the fabrication of these devices, many waste scraps that are not eco-friendly and with high material cost are produced. In this work, a simple powder processing technology is applied to prepare n-type Bi2Te3 pellets by cold pressing (high pressure at room temperature) and annealing the treatment with a canning package to recycle waste scraps. High-pressure cold pressing causes the plastic deformation of densely packed pellets. Then, the thermoelectric properties of pellets are improved through high-temperature annealing (500 ∘C) without phase separation. This enhancement occurs because tellurium cannot escape from the canning package. In addition, high-temperature annealing induces rapid grain growth and rearrangement, resulting in a porous structure. Electrical conductivity is increased by abnormal grain growth, whereas thermal conductivity is decreased by the porous structure with phonon scattering. Owing to the low thermal conductivity and satisfactory electrical conductivity, the highest ZT value (i.e., 1.0) is obtained by the samples annealed at 500 ∘C. Hence, the proposed method is suitable for a cost-effective and environmentally friendly way.

In Situ Synthesis of a Bi2Te3-Nanosheet/Reduced-Graphene-Oxide Nanocomposite for Non-Enzymatic Electrochemical Dopamine Sensing.

Dopamine is a neurotransmitter that helps cells to transmit pulsed chemicals. Therefore, dopamine detection is crucial from the viewpoint of human health. Dopamine determination is typically achieved via chromatography, fluorescence, electrochemiluminescence, colorimetry, and enzyme-linked methods. However, most of these methods employ specific biological enzymes or involve complex detection processes. Therefore, non-enzymatic electrochemical sensors are attracting attention owing to their high sensitivity, speed, and simplicity. In this study, a simple one-step fabrication of a Bi2Te3-nanosheet/reduced-graphene-oxide (BT/rGO) nanocomposite was achieved using a hydrothermal method to modify electrodes for electrochemical dopamine detection. The combination of the BT nanosheets with the rGO surface was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry were performed to analyze the electrochemical-dopamine-detection characteristics of the BT/rGO nanocomposite. The BT/rGO-modified electrode exhibited higher catalytic activity for electrocatalytic oxidation of 100 µM dopamine (94.91 µA, 0.24 V) than that of the BT-modified (4.55 µA, 0.26 V), rGO-modified (13.24 µA, 0.23 V), and bare glassy carbon electrode (2.86 µA, 0.35 V); this was attributed to the synergistic effect of the electron transfer promoted by the highly conductive rGO and the large specific surface area/high charge-carrier mobility of the two-dimensional BT nanosheets. The BT/rGO-modified electrode showed a detection limit of 0.06 µM for dopamine in a linear range of 10-1000 µM. Additionally, it exhibited satisfactory reproducibility, stability, selectivity, and acceptable recovery in real samples.

Sub-10 nm Precision Engineering of Solid-State Defects via Nanoscale Aperture Array Mask.

Engineering a strongly interacting uniform qubit cluster would be a major step toward realizing a scalable quantum system for quantum sensing and a node-based qubit register. For a solid-state system that uses a defect as a qubit, various methods to precisely position defects have been developed, yet the large-scale fabrication of qubits within the strong coupling regime at room temperature continues to be a challenge. In this work, we generate nitrogen vacancy (NV) color centers in diamond with sub-10 nm scale precision using a combination of nanoscale aperture arrays (NAAs) with a high aspect ratio of 10 and a secondary E-beam hole pattern used as an ion-blocking mask. We perform optical and spin measurements on a cluster of NV spins and statistically investigate the effect of the NAAs during an ion-implantation process. We discuss how this technique is effective for constructing a scalable system.

CaFe-Based Layered Double Oxides With Superior Iron Alloy Corrosion Inhibition Behaviors in Aggressive Seawater Environment.

Reinforced concrete is among the most multifaceted materials used in the construction field. Maintaining the resistance of reinforced concrete to weathering, abrasion, and chemical attack, particularly in aggressive natural conditions such as seawater environments, is challenging. The main factor in the degradation of reinforced-concrete durability is chloride penetration, which accelerates iron alloy corrosion and facilitates structural degradation. In this study, calcium-iron-based layered double hydroxides (CaFe-LDHs) were fabricated at room temperature, followed by structural modulation, and their effectiveness in mitigating iron alloy corrosion due to chloride ions (in 3.5 wt% of NaCl) was investigated. The synthesized CaFe-LDHs with phase transfer notably improved the Cl- removal capacity (Qmax) to 881.83 mg/g, which is more than three times that reported based on previous studies. The novelty of this research lies in the sophisticated structural and phase transformations of the as-synthesized CaFe-LDHs, determination of crucial factors for chloride ion removal, and suggestion of calcium-iron-based layered double oxide (CaFe-LDO)-based chloride ion removal mechanisms considering chemical and ion-exchange reactions. Moreover, when the phase-transformed LDHs, C-700 LDOs, were applied to inhibit iron alloy corrosion, a noticeable inhibition efficiency of 98.87% was obtained, which was an 11-fold improvement compared to the case of iron alloys without LDOs. We believe this work can provide new insights into the design of CaFe-LDOs for the enhancement of the lifespan of reinforced concrete structures.

Highly Water-Dispersible Graphene Nanosheets From Electrochemical Exfoliation of Graphite.

The electrochemical exfoliation of graphite has been considered to be an effective approach for the mass production of high-quality graphene due to its easy, simple, and eco-friendly synthetic features. However, water dispersion of graphene produced in the electrochemical exfoliation method has also been a challenging issue because of the hydrophobic properties of the resulting graphene. In this study, we report the electrochemical exfoliation method of producing water-dispersible graphene that importantly contains the relatively low oxygen content of <10% without any assistant dispersing agents. Through the mild in situ sulfate functionalization of graphite under alkaline electrochemical conditions using a pH buffer, the highly water-dispersible graphene could be produced without any additional separation processes of sedimentation and/or centrifugation. We found the resulting graphene sheets to have high crystalline basal planes, lateral sizes of several µm, and a thickness of <5 nm. Furthermore, the high aqueous dispersion stability of as-prepared graphene could be demonstrated using a multi-light scattering technique, showing very little change in the optical transmittance and the terbiscan stability index over time.

One-step synthesis of black TiO2-x microspheres by ultrasonic spray pyrolysis process and their visible-light-driven photocatalytic activities.

Black TiO2-x has recently emerged as one of the most promising visible-light-driven photocatalysts, but current synthesis routes that require a reduction step are not compatible with cost-effective mass production and a relatively large particle such as microspheres. Herein, we demonstrate a simple, fast, cost-effective and scalable one-step process based on an ultrasonic spray pyrolysis for the synthesis of black TiO2-x microspheres. The process utilizes an oxygen-deficient environment during the pyrolysis of titanium precursors to directly introduce oxygen vacancies into synthesized TiO2 products, and thus a reduction step is not required. Droplets of a titanium precursor solution were generated by ultrasound energy and dragged with continuous N2 flow into a furnace for the decomposition of the precursor and crystallization to TiO2 and through such a process spherical black TiO2-x microspheres were obtained at 900 °C. The synthesized black TiO2-x microsphere with trivalent titanium/oxygen vacancy clearly showed the variation of physicochemical properties compared with those of white TiO2. In addition, the synthesized microspheres presented the superior photocatalytic activity for degradation of methylene blue under visible light irradiation. This work presents a new methodology for a simple one-step synthesis of black metal oxides microspheres with oxygen vacancies for visible-light-driven photocatalysts with a higher efficiency.

Segregation-controlled self-assembly of silver nanowire networks using a template-free solution-based process.

Metal conductive patterning has been studied as an alternative to the most commonly used indium tin oxide electrodes. Printed electrodes are fabricated by several complicated processes including etching, photolithography, and laser- and template-based techniques. However, these patterning methods have increasingly encountered critical issues of long manufacturing times and high equipment costs that necessitate vacuum and high-temperature conditions. In this study, we present a template-free solution-based patterning method for the fabrication of transparent electronics by inducing segregation-based networks of silver nanowires (SGAgNWs); this is a potential method to fabricate cost effective and scalable optoelectronics. Micro-dimensional fine-patterned segregated networks with conductive cells are created by the self-assembly of one-dimensional nanomaterials under optimal ink conditions wherein different types of solvents and aspect ratios of silver nanowires (AgNWs) are formulated. Photoelectric properties can be controlled by adjusting the size of the cell, which is an empty domain surrounded by the AgNW assembly with microscale cell-to-cell distance dimensions ranging between 4 to 345 µm. The as-obtained AgNW metal grid-formulated on a polyethylene terephthalate film-was identified as a high-performance transparent electrode (TE) device with excellent optoelectronic properties of 87.08% transmittance and 50 Ω â–¡-1 resistance. In addition, the electrical conductivity of the TE film is enhanced with a very low haze of less than 4% because of the intense pulsed light treatment that diminished the sheet resistance to 21.36 Ω â–¡-1, which is attributed to the creation of welded silver networks. The SGAgNW concept for TE technology demonstrates a very promising potential for use in next-generation flexible electronic devices.

Structure-modulated CaFe-LDHs with superior simultaneous removal of deleterious anions and corrosion protection of steel rebar.

The three anionic species; chloride (Cl-), sulfate (SO4 2-), and carbonate (CO3 2-), are typical chemical factors that environmentally accelerate failure of concrete structures with steel rebar through long-term exposure. Efficient removal of these deleterious anions at the early stage of penetration is crucial to enhance the lifespan and durability of concrete structures. Here, we synthesize CaFe-layered double hydroxide (CaFe-LDHs) by a simple one-step co-precipitation technique and structural modulation by calcination process. It is applied for the removal of Cl-, SO4 2-, and CO3 2- anions as well as corrosion inhibition on steel rebar in aqueous solutions. The synthesized CaFe-LDHs with phase transfer show notable improvement of removal capacity (Q max) toward Cl- and SO4 2- over 3.4 times and over 5.69 times, respectably, then those of previous literatures. Furthermore, the steel rebar exposed to an aqueous solution containing the three anionic sources shows a fast corrosion rate (1876.56 × 10-3 mm per year), which can be remarkably inhibited showing 98.83% of corrosion inhibition efficiency when it is surrounded by those CaFe-LDHs. The novel adsorption mechanisms of these CaFe-LDHs-induced crystals and corresponding corrosion protection properties are elucidated drawing on synergy of memory effects and chemical reactions.

In situ exfoliation and modification of graphite foil in supercapacitor devices: a facile strategy to fabricate high-performance supercapacitors.

Graphite foils (GFs) are emerging as a new class of electrodes in supercapacitors (SCs) based on their light weight, and high electrical conductivity, although the surface area remains low. A novel method of, in situ electrochemical exfoliation and modification of GF in the assembled SCs, showed high energy density and power density of the SC devices.

Anisotropic characteristics and improved magnetic performance of Ca-La-Co-substituted strontium hexaferrite nanomagnets.

Recent studies on next-generation permanent magnets have focused on filling in the gap between rare-earth magnets and rare-earth-free magnets, taking into account both the cost-effectiveness and magnetic performance of the magnetic materials. As an improved rare-earth-free magnet candidate, here, Ca-substituted M-type Sr-lean hexaferrite particles within a nano- to micro-scale regime, produced using an ultrasonic spray pyrolysis method, are investigated. Theoretically, the maximum coercivity (Hc) can be achieved in submicron Sr-ferrite crystals (i.e., 0.89 µm). The plate-like resultants showed a significant enhancement in Hc, up to a record high of 7880.4 Oe, with no deterioration in magnetization (M: 71-72 emu/g). This resulted in more favorable magnetic properties than those of the traditional Sr-La-Co ferrites. On the basis of microstructural analysis and fitting results based on the law of approach to saturation method, the Ca-substitution effects on the change in size and anisotropic characteristics of the ferrite particles, including pronounced lateral crystal growth and a strong increase in magnetocrystalline anisotropy, are clearly demonstrated. The cost-effective, submicron, and Ca-substituted Sr-ferrite is an excellent potential magnet and moreover may overcome the limitations of traditional hard magnetic materials.

All-printed nanomembrane wireless bioelectronics using a biocompatible solderable graphene for multimodal human-machine interfaces.

Recent advances in nanomaterials and nano-microfabrication have enabled the development of flexible wearable electronics. However, existing manufacturing methods still rely on a multi-step, error-prone complex process that requires a costly cleanroom facility. Here, we report a new class of additive nanomanufacturing of functional materials that enables a wireless, multilayered, seamlessly interconnected, and flexible hybrid electronic system. All-printed electronics, incorporating machine learning, offers multi-class and versatile human-machine interfaces. One of the key technological advancements is the use of a functionalized conductive graphene with enhanced biocompatibility, anti-oxidation, and solderability, which allows a wireless flexible circuit. The high-aspect ratio graphene offers gel-free, high-fidelity recording of muscle activities. The performance of the printed electronics is demonstrated by using real-time control of external systems via electromyograms. Anatomical study with deep learning-embedded electrophysiology mapping allows for an optimal selection of three channels to capture all finger motions with an accuracy of about 99% for seven classes.

Pt/Graphene Catalyst and Tellurium Nanowire-Based Thermochemical Hydrogen (TCH) Sensor Operating at Room Temperature in Wet Air.

We present a thermochemical hydrogen (TCH) gas sensor fabricated with Pt-decorated exfoliated graphene sheets and a tellurium nanowire-based thermoelectric (TNTE) layer operating at room temperature in wet air. The sensor device was able to detect 50 ppm to 3% of hydrogen gas within several seconds (response/recovery times of 6/5.1 s at 4000 ppm of hydrogen gas) at room temperature due to the relatively high surface area of homogeneously dispersed Pt nanocrystals (∼8 nm) decorated on graphene sheets and the excellent Seebeck coefficient (428 µV/K) of the TNTE layer. Furthermore, it was observed that the effect of the relative humidity on sensing properties was greatly minimized by incorporating Pt-decorated graphene sheets. These results indicate that our device has great potential as a low power consumption gas sensor for IoTs.

Exchange-Coupling Interaction in Zero- and One-Dimensional Sm2Co17/FeCo Core-Shell Nanomagnets.

Rare-earth-based core-shell spring nanomagnets have been intensively studied in the permanent magnet industry. However, the inherent agglomeration characteristics of zero-dimensional (0-D) magnetic nanoparticles are an issue in practical fabrication of magnetic nanocomposites due to deterioration in exchange-coupling interactions, resulting in inferior magnetic performance. Here, with an aim to overcome the structural limitations, we report a new type of SmCo/FeCo core-shell nanomagnet with a well-dispersed one-dimensional (1-D) structure prepared by a combination of electrospinning and electroless plating processes. An FeCo layer with a tailored thickness on nanoscale SmCo was produced to achieve a sufficient exchange-coupling effect. The influence of electroless plating time on the microstructure of fibers was discussed, and comparisons were made as a function of the magnet shape. A 1-D SmCo/FeCo spring nanomagnet having a core diameter ranging from 150 to 200 nm and a shell thickness of 15-20 nm showed a potent exchange-coupling effect compared with its 0-D counterpart. This effectively reduced self-aggregation and further showed a remarkable enhancement in (BH)max (above 45.7%). We think that this novel structure marks a new era in the exchange-spring magnet industry and may overcome the limitations of traditional core-shell nanomagnets.

Controlled Grafting of Colloidal Nanoparticles on Graphene through Tailored Electrostatic Interaction.

Nanoparticle/graphene hybrid composites have been of great interest in various disciplines due to their unique synergistic physicochemical properties. In this study, we report a facile and generalized synthesis method for preparing nanoparticle/exfoliated graphene (EG) composites by tailored electrostatic interactions. EG was synthesized by an electrochemical method, which produced selectively oxidized graphene sheets at the edges and grain boundaries. These EG sheets were further conjugated with polyethyleneimine to provide positive charges at the edges. The primary organic ligands of the colloidal nanoparticles were exchanged with Cl- or MoS42- anions, generating negatively charged colloidal nanoparticles in polar solvents. By simple electrostatic interactions between the EG and nanoparticles in a solution, nanoparticles were controllably assembled at the edges of the EG. Furthermore, the generality of this process was verified for a wide range of nanoparticles, such as semiconductors, metals, and magnets, on the EG. As a model application, designed composites with size-controlled FeCo nanoparticle/EG were utilized as electromagnetic interference countermeasure materials that showed a size-dependent shift of the frequency ranges on the electromagnetic absorption properties. The current generalized process will offer great potential for the large-scale production of well-designed graphene nanocomposites for electronic and energy applications.