Sequential Dual Coating with Thermosensitive Polymers for Advanced Fiber Optic Temperature Sensors.

We systematically designed dual polymer Fabry-Perrot interferometer (DPFPI) sensors, which were used to achieve highly sensitive temperature sensors. The designed and fabricated DPFPI has a dual polymer coating layer consisting of thermosensitive poly (methyl methacrylate) (PMMA) and polycarbonate (PC) polymers. Four different DPFPI sensors were developed, in which different coating optical path lengths and the resultant optical properties were generated by the Vernier effect, changing the sequence of the applied polymers and varying the concentration of the coating solutions. The experimental results confirmed that the PC_PMMA_S1 DPFPI sensor delivered a temperature sensitivity of 1238.7 pm °C-1, which was approximately 4.4- and 1.4-fold higher than that of the PMMA and PMMA_PC_S1-coated sensor, respectively. Thus, the results reveal that the coating sequence, the compact thickness of the dual polymer layers, and the resultant optical parameters are accountable for achieving sensors with high sensitivity. In the PC_ PMMA-coated sensor, the PMMA outer layer has comparatively better optical properties than the PC, which might produce synergistic effects that create a large wavelength shift with small temperature deviations. Therefore, it is considered that the extensive results with the PC_PMMA_S1 DPFPI sensor validate the efficacy, repeatability, reliability, quick reaction, feasibility, and precision of the temperature readings.

Vanadium Ferrocyanides as a Highly Stable Cathode for Lithium-Ion Batteries.

Owing to their high redox potential and availability of numerous diffusion channels in metal-organic frameworks, Prussian blue analogs (PBAs) are attractive for metal ion storage applications. Recently, vanadium ferrocyanides (VFCN) have received a great deal of attention for application in sodium-ion batteries, as they demonstrate a stable capacity with high redox potential of ~3.3 V vs. Na/Na+. Nevertheless, there have been no reports on the application of VFCN in lithium-ion batteries (LIBs). In this work, a facile synthesis of VFCN was performed using a simple solvothermal method under ambient air conditions through the redox reaction of VCl3 with K3[Fe(CN)6]. VFCN exhibited a high redox potential of ~3.7 V vs. Li/Li+ and a reversible capacity of ~50 mAh g-1. The differential capacity plots revealed changes in the electrochemical properties of VFCN after 50 cycles, in which the low spin of Fe ions was partially converted to high spin. Ex situ X-ray diffraction measurements confirmed the unchanged VFCN structure during cycling. This demonstrated the high structural stability of VFCN. The low cost of precursors, simplicity of the process, high stability, and reversibility of VFCN suggest that it can be a candidate for large-scale production of cathode materials for LIBs.

Metal salt-modified biochars derived from agro-waste for effective congo red dye removal.

Anionic Congo red dye (CR) is not effectively removed by conventional adsorbents. Three novel biochars derived from agro-waste (Acacia auriculiformis), modified with metal salts of FeCl3, AlCl3, and CaCl2 at 500 °C pyrolysis have been developed to enhance CR treatment. These biochars revealed significant differences in effluents compared to BC, which satisfied initial research expectations (P < 0.05). The salt concentration of 2 M realized optimal biochars with the highest CR removal of 96.8%, for AlCl3-biochar and FeCl3-biochar and 70.8% for CaCl2-biochar. The modified biochars were low in the specific surface area (137.25-380.78 m2 g-1) compared normal biochar (393.15 m2 g-1), had more heterogeneous particles and successfully integrated metal oxides on the surface. The CR removal increased with a decrease in pH and increase in biochar dosage, which established an optimal point at an initial loading of 25 mg g-1. Maximum adsorption capacity achieved 130.0, 44.86, and 30.80 mg g-1 for BFe, BCa, and BAl, respectively. As magnetic biochar, which is easily separated from the solution and achieves a high adsorption capacity, FeCl3-biochar is the preferred biochar for CR treatment application.

Simply Fabricated Inexpensive Dual-Polymer-Coated Fabry-Perot Interferometer-Based Temperature Sensors with High Sensitivity.

We designed simply fabricated, highly sensitive, and cost-effective dual-polymer-coated Fabry-Perot interferometer (DFPI)-based temperature sensors by employing thermosensitive polymers and non-thermosensitive polymers, as well as different two successive dip-coating techniques (stepwise dip coating and polymer mixture coating). Seven sensors were fabricated using different polymer combinations for performance optimization. The experiments demonstrated that the stepwise dip-coated dual thermosensitive polymer sensors exhibited the highest sensitivity (2142.5 pm °C-1 for poly(methyl methacrylate)-polycarbonate (PMMA_PC) and 785.5 pm °C-1 for poly(methyl methacrylate)- polystyrene (PMMA_PS)). Conversely, the polymer-mixture-coated sensors yielded low sensitivities (339.5 pm °C-1 for the poly(methyl methacrylate)-polycarbonate mixture (PMMA_PC mixture) and 233.5 pm °C-1 for the poly(methyl methacrylate)-polystyrene mixture (PMMA_PS mixture). Thus, the coating method, polymer selection, and thin air-bubble-free coating are crucial for high-sensitivity DFPI-based sensors. Furthermore, the DFPI-based sensors yielded stable readouts, based on three measurements. Our comprehensive results confirm the effectiveness, reproducibility, stability, fast response, feasibility, and accuracy of temperature measurements using the proposed sensors. The excellent performance and simplicity of our proposed sensors are promising for biomedical, biochemical, and physical applications.

Enhancing Temperature Sensitivity of the Fabry-Perot Interferometer Sensor with Optimization of the Coating Thickness of Polystyrene.

The exploration of novel polymers for temperature sensing with high sensitivity has attracted tremendous research interest. Hence, we report a polystyrene-coated optical fiber temperature sensor with high sensitivity. To enhance the temperature sensitivity, flat, thin, smooth, and air bubble-free polystyrene was coated on the edge surface of a single-mode optical fiber, where the coating thickness was varied based on the solution concentration. Three thicknesses of the polystyrene layer were obtained as 2.0, 4.1, and 8.0 µm. The temperature sensor with 2.0 µm thick polystyrene exhibited the highest temperature sensitivity of 439.89 pm °C-1 in the temperature range of 25-100 °C. This could be attributed to the very uniform and thin coating of polystyrene, along with the reasonable coefficient of thermal expansion and thermo-optic coefficient of polystyrene. Overall, the experimental results proved the effectiveness of the proposed polystyrene-coated temperature sensor for accurate temperature measurement.

FexSnyOz Composites as Anode Materials for Lithium-Ion Storage.

A novel composite, FexSnyOz, consisting of tin oxide and iron oxide was developed via a galvanic replacement reaction. The morphology, crystalline structure, and composition of the FexSnyOz composite were investigated by employing X-ray diffraction, energy dispersive X-ray spectroscopy, and transmission electron microscopy. When evaluated as an anode material using different binders, namely, polyvinylidene fluoride (PVDF) and poly(acrylic acid) (PAA), the composite blended with the PAA binder displayed a high coulombic efficiency and excellent cycling stability compared to the composite mixed with the PVDF binder. The excellent electrochemical performance could be attributed to the different interactions between the current collector and the binders, as well as the volume accommodation during cycling. Therefore, the results indicated that the application of an appropriate binder could lead to a significant improvement in the electrochemical performance of FexSnyOz composite anodes for lithium-ion batteries.

Electrochemical Performance of Sn/SnO/Ni3Sn Composite Anodes for Lithium-Ion Batteries.

We have synthesized a novel composite material Sn/SnO/Ni3Sn via galvanic replacement reaction between Sn and Ni2+ ions in triethylene glycol medium and at high temperature. The reaction time affected structure, particle size, and composition of Sn/SnO/Ni3Sn composites, which were analyzed by high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The active component (Sn) reacts with Li+ ions while inactive component (Ni) acts as a metal framework to support the electrochemically active Sn, a buffer to reduce volume change during cycling, and the electron conductor. Among electrodes, the Sn/SnO/Ni3Sn-6h electrode demonstrated stable cycling and reversible capacity of 246 mAh g-1 even after 300 cycles owing to the advantages from the unique hybrid structure.

Electrochemical Performance of FeSb2-P@C Composites as Anode Materials for Lithium-Ion Storage.

We have synthesized a novel composite material, FeSb2 alloy with red phosphorus (P) dispersed in a conductive carbon matrix, using high-energy ball milling (HEBM). The introduction of red P into FeSb2 alloy led to a formation of Sb phase along with FeSb2 phase due to the difference of binding energy between the elements. The morphology and structure were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The active components (Sb and P) react with Li+ ions while inactive element (Fe) and carbon matrix act as a metal framework to support the electrochemically active Sb and as a buffer to reduce volume change during cycling, respectively. Among electrodes (FeSb2, FeSb2-P, FeSb2-P@C), the FeSb2-P@C electrode demonstrated high reversible capacity of 400 mAh g-1 with a good capacity retention of ~68% at 50 cycles and high rate reversible capacity of ~470 mAh g-1 at a current rate of 3000 mA g-1.

Crab-Shell Biotemplated SnO2 Composite Anodes for Lithium-Ion Batteries.

SnO2 composite materials infiltrated into the hollow carbon channels of a crab-shell biotemplate were hydrothermally synthesized and utilized as anodes for lithium-ion batteries. Varying the reaction temperatures and times of the hydrothermal reaction yielded different SnO2 nanoparticle shapes, characterized by scanning electron microscopy and transmission electron microscopy. The materials prepared at 100 °C (sample S100) were spherical, amorphous in nature, and successfully infiltrated into the hollow carbon channels, while those prepared at 180 °C (sample S180) yielded many rod-like particles on the outer surfaces of the channels. The S100 electrode exhibited better cyclability, corresponding to a capacity of 298 mAh g-1 at 100 cycles, and high rate capability with a capacity retention of 54% at 3 A g-1. The enhanced electrochemical performance of S100 could be attributed to the configuration of the SnO2 particles infiltrating the carbon-coated hollow channels, which accommodated large volume changes during (de)lithiation.

Fabrication of Self-Healable and Patternable Polypyrrole/Agarose Hybrid Hydrogels for Smart Bioelectrodes.

We present a new class of electrically conductive, mechanically moldable, and thermally self-healable hybrid hydrogels. The hybrid gels consist of polypyrrole and agarose as the conductive component and self-healable matrix, respectively. By using the appropriate oxidizing agent under conditions of mild temperature, the polymerization of pyrrole occurred along the three-dimensional network of the agarose hydrogel matrix. In contrast to most commercially available hydrogels, the physical crosslinking of agarose gel allows for reversible gelation in the case of our hybrid gel, which could be manipulated by temperature variation, which controls the electrical on/off behavior of the hybrid gel electrode. Exploiting this property, we fabricated a hybrid conductive hydrogel electrode which also self-heals thermally. The novel composite material we report here will be useful for many technological and biological applications, especially in reactive biomimetic functions and devices, artificial muscles, smart membranes, smart full organic batteries, and artificial chemical synapses.

High-performance FeSb-TiC-C nanocomposite anodes for sodium-ion batteries.

Antimony-based alloy anodes with a Fe metal support dispersed in a conductive matrix consisting of TiC and carbon have been developed by high energy mechanical milling (HEMM) for sodium-ion batteries. The samples have been characterized by X-ray diffraction before and after sodiation at different C rates and by high-resolution transmission electron microscopy before and after cycling for 100 cycles. Electrochemical charge-discharge cycling at various rates and electrochemical impedance spectroscopy measurements have been carried out with and without 2 vol% of the fluoroethylene carbonate (FEC) additive in the electrolyte. With well-defined crystalline FeSb and TiC structures, the FeSb-TiC-C nanocomposite anodes demonstrate superior rate capability with good capacity retention at 10,000 mA g(-1) for sodium-ion storage, which could be ascribed to the novel nanocomposite structure consisting of a good metal (Fe) framework and a combination of conductive TiC and carbon as a matrix. The FEC additive particularly leads to a longer cycle life with high rate capability due to the formation of a stable, thin SEI layer and a smaller charge-transfer resistance.

Iron-Vanadium Incorporated Ferrocyanides as Potential Cathode Materials for Application in Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are potential replacements for lithium-ion batteries owing to their comparable energy density and the abundance of sodium. However, the low potential and low stability of their cathode materials have prevented their commercialization. Prussian blue analogs are ideal cathode materials for SIBs owing to the numerous diffusion channels in their 3D structure and their high potential vs. Na/Na+. In this study, we fabricated various Fe-V-incorporated hexacyanoferrates, which are Prussian blue analogs, via a one-step synthesis. These compounds changed their colors from blue to green to yellow with increasing amounts of incorporated V ions. The X-ray photoelectron spectroscopy spectrum revealed that V3+ was oxidized to V4+ in the cubic Prussian blue structure, which enhanced the electrochemical stability and increased the voltage platform. The vanadium ferrocyanide Prussian blue (VFPB1) electrode, which contains V4+ and Fe2+ in the Prussian blue structure, showed Na insertion/extraction potential of 3.26/3.65 V vs. Na/Na+. The cycling test revealed a stable capacity of ~70 mAh g-1 at a rate of 50 mA g-1 and a capacity retention of 82.5% after 100 cycles. We believe that this Fe-V-incorporated Prussian green cathode material is a promising candidate for stable and high-voltage cathodes for SIBs.

Recent Advances in Sodium-Ion Batteries: Cathode Materials.

Emerging energy storage systems have received significant attention along with the development of renewable energy, thereby creating a green energy platform for humans. Lithium-ion batteries (LIBs) are commonly used, such as in smartphones, tablets, earphones, and electric vehicles. However, lithium has certain limitations including safety, cost-effectiveness, and environmental issues. Sodium is believed to be an ideal replacement for lithium owing to its infinite abundance, safety, low cost, environmental friendliness, and energy storage behavior similar to that of lithium. Inhered in the achievement in the development of LIBs, sodium-ion batteries (SIBs) have rapidly evolved to be commercialized. Among the cathode, anode, and electrolyte, the cathode remains a significant challenge for achieving a stable, high-rate, and high-capacity device. In this review, recent advances in the development and optimization of cathode materials, including inorganic, organometallic, and organic materials, are discussed for SIBs. In addition, the challenges and strategies for enhancing the stability and performance of SIBs are highlighted.

Te-rP-C Anodes Prepared Using a Scalable Milling Process for High-Performance Lithium-Ion Batteries.

Red phosphorus (rP) is one of the most promising anode materials for lithium-ion batteries, owing to its high theoretical capacity. However, its low electronic conductivity and large volume expansion during cycling limit its practical applications, as it exhibits low electrochemical activity and unstable cyclability. To address these problems, tellurium (Te)-rP-C composites, which have active materials (Te, rP) that are uniformly distributed within the carbon matrix, were fabricated through a simple high-energy ball milling method. Among the three electrodes, the Te-rP (1:2)-C electrode with a 5% FEC additive delivers a high initial CE of 80% and a high reversible capacity of 734 mAh g-1 after 300 cycles at a current density of 100 mA g-1. Additionally, it exhibits a high-rate capacity of 580 mAh g-1 at a high current density of 10,000 mA g-1. Moreover, a comparison of the electrolytes with and without the 5% FEC additive demonstrated improved cycling stability when the FEC additive was used. Ex situ XRD analysis demonstrated the lithiation/delithiation mechanism of Te-rP (1:2)-C after cycling based on the cyclic voltammetry results. Based on the electrochemical impedance spectroscopy analysis results, a Te-rP-C composite with its notable electrochemical performance as an anode can sufficiently contribute to the battery anode industry.

Development of Efficient Sodium Alginate/Polysuccinimide-Based Hydrogels as Biodegradable Acetaminophen Delivery Systems.

Efficient drug delivery systems are essential for improving patient outcomes. Acetaminophen (AP), which is a kind of oral administration, is a commonly used pain reliever and fever reducer. However, oral administration carries various health risks, especially overdose and frequent use; for instance, AP is administered approximately 4 times per day. Therefore, the aim of this study is to develop an efficient delivery system for once-daily administration by combining sodium alginate and polysuccinimide (PSI) hydrogels to delay the release of analgesic AP. PSI is a biodegradable polymer that can be used safely and effectively in drug delivery systems because it is eliminated by hydrolysis in the intestine. The use of PSI also improves the mechanical properties of hydrogels and prolongs drug release. In this study, hydrogel characterizations such as mechanical properties, drug dissolution ability, and biodegradability were measured to evaluate the hydrolysis of PSI in the intestine. Based on the results, hydrogels could be designed to improve the structural mechanical properties and to allow the drug to be completely dissolved, and eliminated from the body through PSI hydrolysis in the intestines. In addition, the release profiles of AP in the hydrogels were evaluated, and the hydrogels provided continuous release of AP for 24 h. Our research suggests that sodium alginate/PSI hydrogels can potentially serve as biodegradable delivery systems for AP. These findings may have significant implications for developing efficient drug delivery systems for other classes of drugs.

Tailored synthesis of NdMnxFe1-xO3 perovskite nanoparticles with oxygen-vacancy defects for lithium-ion battery anodes.

In this study, we synthesize nanostructured NdMnxFe1-xO3 perovskites using a facile method to produce materials for the high-working-efficiency anodes of Li-ion batteries. A series of characterization assessments (e.g., X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electron microscopy) were conducted, and the results confirmed the efficacious partial replacement of Fe ions with Mn ions in the NdFeO3 perovskite structure, occurrence of both amorphous and crystalline structures, presence of oxygen vacancies (VO), and interconnection between nanoparticles. The possibility of Mn ion replacement significantly affects the size, amount of VO, and ratio of amorphous phase in NdMnxFe1-xO3 perovskites. The NdMnxFe1-xO3 perovskite with x = 0.3 presents a notable electrochemical performance, including low charge transfer resistance, durable Coulombic efficiency, first-rate capacity reservation, high pseudo-behavior, and elongated 150-cycle service life, whereas no discernible capacity deterioration is observed. The reversible capacity of the anode after the 150th-cylcle was 713 mAh g-1, which represents a high-capacity value. The outstanding electrochemical efficiency resulted from the optimum presence of VO, interconnection between the nanoparticles, and distinctive properties of the NdFeO3 perovskite. The interconnection between nanoparticles was advantageous for forming a large electrolyte-electrode contact area, improving Li-ion diffusion rates, and enhancing pseudocapacitive effect. The attributes of perovskite crystals, coexistence of Mn and Fe throughout the charge/discharge process, and optimum VO precluded the electrode devastation that caused the Li2O-phase decomposition catalysis, enabling favorable reversible Li storage.

In Situ Growth of W2C/WS2 with Carbon-Nanotube Networks for Lithium-Ion Storage.

The combination of W2C and WS2 has emerged as a promising anode material for lithium-ion batteries. W2C possesses high conductivity but the W2C/WS2-alloy nanoflowers show unstable performance because of the lack of contact with the leaves of the nanoflower. In this study, carbon nanotubes (CNTs) were employed as conductive networks for in situ growth of W2C/WS2 alloys. The analysis of X-ray diffraction patterns and scanning/transmission electron microscopy showed that the presence of CNTs affected the growth of the alloys, encouraging the formation of a stacking layer with a lattice spacing of ~7.2 Å. Therefore, this self-adjustment in the structure facilitated the insertion/desertion of lithium ions into the active materials. The bare W2C/WS2-alloy anode showed inferior performance, with a capacity retention of ~300 mAh g-1 after 100 cycles. In contrast, the WCNT01 anode delivered a highly stable capacity of ~650 mAh g-1 after 100 cycles. The calculation based on impedance spectra suggested that the presence of CNTs improved the lithium-ion diffusion coefficient to 50 times that of bare nanoflowers. These results suggest the effectiveness of small quantities of CNTs on the in situ growth of sulfides/carbide alloys: CNTs create networks for the insertion/desertion of lithium ions and improve the cyclic performance of metal-sulfide-based lithium-ion batteries.

Boron Oxide Enhancing Stability of MoS2 Anode Materials for Lithium-Ion Batteries.

Molybdenum disulfide (MoS2) is the most well-known transition metal chalcogenide for lithium storage applications because of its simple preparation process, superior optical, physical, and electrical properties, and high stability. However, recent research has shown that bare MoS2 nanosheet (NS) can be reformed to the bulk structure, and sulfur atoms can be dissolved in electrolytes or form polymeric structures, thereby preventing lithium insertion/desertion and reducing cycling performance. To enhance the electrochemical performance of the MoS2 NSs, B2O3 nanoparticles were decorated on the surface of MoS2 NSs via a sintering technique. The structure of B2O3 decorated MoS2 changed slightly with the formation of a lattice spacing of ~7.37 Å. The characterization of materials confirmed the formation of B2O3 crystals at 30% weight percentage of H3BO3 starting materials. In particular, the MoS2_B3 sample showed a stable capacity of ~500 mAh·g-1 after the first cycle. The cycling test delivered a high reversible specific capacity of ~82% of the second cycle after 100 cycles. Furthermore, the rate performance also showed a remarkable recovery capacity of ~98%. These results suggest that the use of B2O3 decorations could be a viable method for improving the stability of anode materials in lithium storage applications.

Gallium-Telluride-Based Composite as Promising Lithium Storage Material.

Various applications of gallium telluride have been investigated, such as in optoelectronic devices, radiation detectors, solar cells, and semiconductors, owing to its unique electronic, mechanical, and structural properties. Among the various forms of gallium telluride (e.g., GaTe, Ga3Te4, Ga2Te3, and Ga2Te5), we propose a gallium (III) telluride (Ga2Te3)-based composite (Ga2Te3-TiO2-C) as a prospective anode for Li-ion batteries (LIBs). The lithiation/delithiation phase change mechanism of Ga2Te3 was examined. The existence of the TiO2-C hybrid buffering matrix improved the electrical conductivity as well as mechanical integrity of the composite anode for LIBs. Furthermore, the impact of the C concentration on the performance of Ga2Te3-TiO2-C was comprehensively studied through cyclic voltammetry, differential capacity analysis, and electrochemical impedance spectroscopy. The Ga2Te3-TiO2-C electrode showed high rate capability (capacity retention of 96% at 10 A g-1 relative to 0.1 A g-1) as well as high reversible specific capacity (769 mAh g-1 after 300 cycles at 100 mA g-1). The capacity of Ga2Te3-TiO2-C was enhanced by the synergistic interaction of TiO2 and amorphous C. It thereby outperformed the majority of the most recent Ga-based LIB electrodes. Thus, Ga2Te3-TiO2-C can be thought of as a prospective anode for LIBs in the future.

Ga2Te3-Based Composite Anodes for High-Performance Sodium-Ion Batteries.

Recently, metal chalcogenides have received considerable attention as prospective anode materials for sodium-ion batteries (SIBs) because of their high theoretical capacities based on their alloying or conversion reactions. Herein, we demonstrate a gallium(III) telluride (Ga2Te3)-based ternary composite (Ga2Te3-TiO2-C) synthesized via a simple high-energy ball mill as a great candidate SIB anode material for the first time. The electrochemical performance, as well as the phase transition mechanism of Ga2Te3 during sodiation/desodiation, is investigated. Furthermore, the effect of C content on the performance of Ga2Te3-TiO2-C is studied using various electrochemical analyses. As a result, Ga2Te3-TiO2-C with an optimum carbon content of 10% (Ga2Te3-TiO2-C(10%)) exhibited a specific capacity of 437 mAh·g-1 after 300 cycles at 100 mA·g-1 and a high-rate capability (capacity retention of 96% at 10 A·g-1 relative to 0.1 A·g-1). The good electrochemical properties of Ga2Te3-TiO2-C(10%) benefited from the presence of the TiO2-C hybrid buffering matrix, which improved the mechanical integrity and electrical conductivity of the electrode. This research opens a new direction for the improvement of high-performance advanced SIB anodes with a simple synthesis process.