Promoted Overall Water Splitting Catalytic Activity and Durability of Ni3Fe Alloy by Designing N-Doped Carbon Encapsulation.

Combining an electrochemically stable material onto the surface of a catalyst can improve the durability of a transition metal catalyst, and enable the catalyst to operate stably at high current density. Herein, the contribution of the N-doped carbon shell (NCS) to the electrochemical properties is evaluated by comparing the characteristics of the Ni3Fe@NCS catalyst with the N-doped carbon shell, and the Ni3Fe catalyst. The synthesized Ni3Fe@NCS catalyst has a distinct overpotential difference from the Ni3Fe catalyst (ηOER = 468.8 mV, ηHER = 462.2 mV) at (200 and -200) mA cm-2 in 1 m KOH. In stability test at (10 and -10) mA cm-2, the Ni3Fe@NCS catalyst showed a stability of (95.47 and 99.6)%, while the Ni3Fe catalyst showed a stability of (72.4 and 95.9)%, respectively. In addition, the in situ X-ray Absorption Near Edge Spectroscopy (XANES) results show that redox reaction appeared in the Ni3Fe catalyst by applying voltages of (1.7 and -0.48) V. The decomposition of nickel and iron due to the redox reaction is detected as a high ppm concentration in the Ni3Fe catalyst through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis. This work presents the strategy and design of a next-generation electrochemical catalyst to improve the electrocatalytic properties and stability.

Toward alert triage: scalable qualitative coding framework for analyzing alert notes from the Telehealth Intervention Program for Seniors (TIPS).

Objective: Combined with mobile monitoring devices, telehealth generates overwhelming data, which could cause clinician burnout and overlooking critical patient status. Developing novel and efficient ways to correctly triage such data will be critical to a successful telehealth adoption. We aim to develop an automated classification framework of existing nurses' notes for each alert that will serve as a training dataset for a future alert triage system for telehealth programs. Materials and Methods: We analyzed and developed a coding framework and a regular expression-based keyword match approach based on the information of 24 931 alert notes from a community-based telehealth program. We evaluated our automated alert triaging model for its scalability on a stratified sampling of 800 alert notes for precision and recall analysis. Results: We found 22 717 out of 24 579 alert notes (92%) belonging to at least one of the 17 codes. The evaluation of the automated alert note analysis using the regular expression-based information extraction approach resulted in an average precision of 0.86 (SD = 0.13) and recall 0.90 (SD = 0.13). Discussion: The high-performance results show the feasibility and the scalability potential of this approach in community-based, low-income older adult telehealth settings. The resulting coded alert notes can be combined with participants' health monitoring results to generate predictive models and to triage false alerts. The findings build steps toward developing an automated alert triaging model to improve the identification of alert types in remote health monitoring and telehealth systems.

Development of Cellulose Nanofiber-SnO2 Supported Nanocomposite as Substrate Materials for High-Performance Lithium-Ion Batteries.

The large volumetric expansion of conversion-type anode materials (CTAMs) based on transition-metal oxides is still a big challenge for lithium-ion batteries (LIBs). An obtained nanocomposite was established by tin oxide (SnO2) nanoparticles embedding in cellulose nanofiber (SnO2-CNFi), and was developed in our research to take advantage of the tin oxide's high theoretical specific capacity and the cellulose nanofiber support structure to restrain the volume expansion of transition-metal oxides. The nanocomposite utilized as electrodes in lithium-ion batteries not only inhibited volume growth but also contributed to enhancing electrode electrochemical performance, resulting in the good capacity maintainability of the LIBs electrode during the cycling process. The SnO2-CNFi nanocomposite electrode delivered a specific discharge capacity of 619 mAh g-1 after 200 working cycles at the current rate of 100 mA g-1. Moreover, the coulombic efficiency remained above 99% after 200 cycles showing the good stability of the electrode, and promising potential for commercial activity of nanocomposites electrode.

A Study to Improve the Performance of Mixed Cation-Halide Perovskite-Based UVC Photodetectors.

Photodetectors convert optical signals into electrical signals and demonstrate application potential in various fields, such as optical communication, image detection, environmental monitoring, and optoelectronics. In this study, a mixed cation-halide perovskite-based ultraviolet C photodetector was fabricated using a solution process. The higher the mobility of the perovskite carrier, which is one of the factors affecting the performance of electronic power devices, the better the carrier diffusion. The on/off ratio and responsivity indicate the sensitivity of the response, and together with the detectivity and external quantum efficiency, these parameters demonstrate the performance of the detector. The detector fabricated in this study exhibited a mobility of 202.2 cm2/Vs and a high on/off ratio of 105% at a -2 V bias, under 254 nm light irradiation with an intensity of 0.6 mW/cm2. The responsivity, detectivity, and external quantum efficiency of the as-fabricated detector were 5.07 mA/W, 5.49 × 1011 Jones, and 24.8%, respectively. These findings demonstrate that the solution process employed in this study is suitable for the fabrication of mixed cation-halide perovskites which show immense potential for use as photodetectors.

A Study on UVC Photodetector Using Mixed-Cation Perovskite with High Detection Rate as Light-Absorption Layer.

In this study, a mixed-cation perovskite ultraviolet (UV) C photodetector was fabricated using a simple formamidinium iodide (FAI) post-treatment process. The fabricated device uses FAxMA1-xPbI3 perovskite as a light-absorption layer and SnO2, which has high transmittance in the UVC wavelength region, as an electron-transport layer. The fabricated device exhibited a response of 50.8 mA/W, detectability of 4.47 × 1013 Jones, and external quantum efficiency of 53%. Therefore, the approach used in this study is promising for many applications in the UVC wavelength region.

Recent advances in self-powered and flexible UVC photodetectors.

Ultraviolet-C (UVC) radiation is employed in various applications, including irreplaceable applications in military and civil fields, such as missile guidance, flame detection, partial discharge detection, disinfection, and wireless communication. Although most modern electronics are based on Si, UVC detection technology remains a unique exception because the short wavelength of UV radiation makes efficient detection with Si difficult. In this review, recent challenges in obtaining ideal UVC photodetectors with various materials and various forms are introduced. An ideal photodetector must satisfy the following requirements: high sensitivity, fast response speed, high on/off photocurrent ratio, good regional selectivity, outstanding reproducibility, and superior thermal and photo stabilities. UVC detection is still in its infancy compared to the detection of UVA as well as other photon spectra, and recent research has focused on different key components, including the configuration, material, and substrate, to acquire battery-free, super-sensitive, ultra-stable, ultra-small, and portable UVC photodetectors. We introduce and discuss the strategies for fabricating self-powered UVC photodetectors on flexible substrates in terms of the structure, material, and direction of incoming radiation. We also explain the physical mechanisms of self-powered devices with various architectures. Finally, we present a brief outlook that discusses the challenges and future strategies for deep-UVC photodetectors.

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.

Study on Performance Improvements in Perovskite-Based Ultraviolet Sensors Prepared Using Toluene Antisolvent and CH3NH3Cl.

In this study, a simply structured perovskite-based ultraviolet C (UVC) sensor was prepared using a one-step, low-temperature solution-processing coating method. The UVC sensor utilized CH3NH3PbBr3 perovskite as the light-absorbing layer. To improve the characteristics of CH3NH3PbBr3, an antisolvent process using toluene and the addition of CH3NH3Cl were introduced. The device with these modifications exhibited a response rise/fall time of 15.8/16.2 ms, mobility of 158.7 cm2/V·s, responsivity of 4.57 mA/W, detectivity of 1.02 × 1013 Jones, and external quantum efficiency of 22.32% under the 254-nm UV illumination. Therefore, this methodology could be a good approach in facilitating UVC detection.

A Study on the Characteristics of Perovskite/ZnO-Based Ultraviolet Sensors.

In this study, a UVC sensor was implemented using CH3NH3PbI3, a perovskite material. The UV sensor made with a p-i-n structure uses PEDOT:PSS as the p-type material and ZnO as the n-type material. The fabricated device shows a responsivity of 1.60 mA/W and a detectivity of 2.25×1010 Jones under 254 nm illumination with a power density of 1.02 mW/cm² at 2 V. In addition, the manufactured UV sensor is a self-powered perovskite-based UV sensor that can operate without external bias. Therefore, this UVC sensor can have applications in various fields.

Application of ZnGa2O4:Mn Down-Conversion Layer to Increase the Energy-Conversion Efficiency of Perovskite Solar Cells.

The perovskite solar cell is capable of energy conversion in a wide range of wavelengths, from 300 nm to 800 nm, which includes the entire visible region and portions of the ultraviolet and infrared regions. To increase light transmittance of perovskite solar cells and reduce manufacturing cost of perovskite solar cells, soda-lime glass and transparent conducting oxides, such as indium tin oxide and fluorine-doped tin oxide are mainly used as substrates and light-transmitting electrodes, respectively. However, it is evident from the transmittance of soda-lime glass and transparent conductive oxides measured via UV-Vis spectrometry that they absorb all light near and below 310 nm. In this study, a transparent Mn-doped ZnGa2O4 film was fabricated on the incident surface of perovskite solar cells to obtain additional light energy by down-converting 300 nm UV light to 510 nm visible light. We confirmed the improvement of power efficiency by applying a ZnGa2O4:Mn down-conversion layer to perovskite solar cells.

Characteristics of Perovskite Solar Cells (PSCs) with Various Metal Electrode Deposited Using Thermal Evaporators.

Organic material-based solar cell devices such as perovskite solar cells (PSCs) have attracted attention as renewable energy resources with low production cost, lightweight, wearable device applications, and large-area processability. To enhance device performance, many research groups have attempted to develop new materials and structures. Metal electrode materials play an important role in solar energy conversion in PSCs, owing to the ohmic contact and contact resistance between metal negative electrodes and photoactive layers. Until recently, conventional metal sources such as Ag, Au, or Cu have been used as electrodes. In this study, PSCs were employed in various metal negative electrodes using a thermal evaporator. The authors investigated the effect of metal negative electrodes on PSCs.

Characteristics of Perovskite Solar Cells with Methylammonium Iodide-Added Anti-Solvent.

The perovskite film-manufactured via a one-step method-was superficially improved through an anti-solvent process to increase solar cell efficiency. Although perovskite synthesis proceeds rapidly, a significant amount of lead iodide residue remains. Well-placed lead iodide in perovskite grains prevents electron-hole recombination; however, when irregularly placed, it interferes with the movement of electron and holes. In this study, we focused on improving the crystallinity of the perovskite layer, as well as reducing lead iodide residues by adding a methylammonium halide material to the anti-solvent. Methylammonium iodide in chlorobenzene used as an anti-solvent reduces lead iodide residues and improves the crystallinity of formamidinium lead iodide perovskite. The improved crystallinity of the perovskite layer increased the absorbance and, with reduced lead iodide residues, increased the efficiency of the perovskite solar cell by 1.914%.

Characteristics of Ultraviolet Sensor Based on PEDOT:PSS/Al Doped ZnO Film.

Ultraviolet (UV) sensors have application in many different areas such as flame and hightemperature detection, space research, environmental monitoring, ozone layer monitoring, and missile warning systems. Among them, ZnO thin-film-based UV sensors have been attracting attention among research groups and are being continuously studied. The incorporation of ZnO/organic hybrid structures into solar cells and other photoelectrochemical applications has been extensively reported. However, little research has been performed on ZnO/polymer-based UV sensors. In this study, a simple UV sensor based on an Al:ZnO/polymer is demonstrated. Al-doped ZnO enables effective UV detection with excellent performance at low operating voltages using a simple and inexpensive process.

Characterization of Perovskite Solar Cells According to TiO2 Mesoporous Layer Treated with Ti-Diisopropoxide Bis.

The power conversion efficiency of perovskite solar cells, which are next-generation photovoltaic cells, has rapidly increased up to 20% through ongoing research and development. Recently, various methods have been employed to increase the active area of the mesoporous layer in perovskite solar cells. In this study, the particle aggregation of the TiO2 was controlled by adding Ti-diisopropoxide bis to the mesoporous layer solution; thus, the contact area between the mesoporous layer and perovskite layer was increased. The amount of Ti-diisopropoxide bis added to the mesoporous layer solution was adjusted to prevent the inhibition of electron transport caused by separation of particles and instability of mesoporous layer. To evaluate the changes in the characteristics of the perovskite solar cells due to the TiO2 particle aggregation in the mesoporous layer, X-ray diffraction and spectrophotometric absorbance, as well as cross-sectional and surface scanning electron microscopy measurement were performed, and the current density-voltage curve, power conversion efficiency and other properties were evaluated under solar simulator. It was found that the mesoporous layer was improved due to its enlarged contact area, and hence, can be expected to improve the efficiency of perovskite solar cells.

Improving Heart Disease Risk Through Quality-Focused Diet Logging: Pre-Post Study of a Diet Quality Tracking App.

BACKGROUND: Diet-tracking mobile apps have gained increased interest from both academic and clinical fields. However, quantity-focused diet tracking (eg, calorie counting) can be time-consuming and tedious, leading to unsustained adoption. Diet quality-focusing on high-quality dietary patterns rather than quantifying diet into calories-has shown effectiveness in improving heart disease risk. The Healthy Heart Score (HHS) predicts 20-year cardiovascular risks based on the consumption of foods from quality-focused food categories, rather than detailed serving sizes. No studies have examined how mobile health (mHealth) apps focusing on diet quality can bring promising results in health outcomes and ease of adoption. OBJECTIVE: This study aims to design a mobile app to support the HHS-informed quality-focused dietary approach by enabling users to log simplified diet quality and view its real-time impact on future heart disease risks. Users were asked to log food categories that are the main predictors of the HHS. We measured the app's feasibility and efficacy in improving individuals' clinical and behavioral factors that affect future heart disease risks and app use. METHODS: We recruited 38 participants who were overweight or obese with high heart disease risk and who used the app for 5 weeks and measured weight, blood sugar, blood pressure, HHS, and diet score (DS)-the measurement for diet quality-at baseline and week 5 of the intervention. RESULTS: Most participants (30/38, 79%) used the app every week and showed significant improvements in DS (baseline: mean 1.31, SD 1.14; week 5: mean 2.36, SD 2.48; 2-tailed t test t29=-2.85; P=.008) and HHS (baseline: mean 22.94, SD 18.86; week 4: mean 22.15, SD 18.58; t29=2.41; P=.02) at week 5, although only 10 participants (10/38, 26%) checked their HHS risk scores more than once. Other outcomes, including weight, blood sugar, and blood pressure, did not show significant changes. CONCLUSIONS: Our study showed that our logging tool significantly improved dietary choices. Participants were not interested in seeing the HHS and perceived logging diet categories irrelevant to improving the HHS as important. We discuss the complexities of addressing health risks and quantity- versus quality-based health monitoring and incorporating secondary behavior change goals that matter to users when designing mHealth apps.

SnO2 Nanoflower-Nanocrystalline Cellulose Composites as Anode Materials for Lithium-Ion Batteries.

One of the biggest challenges in the commercialization of tin dioxide (SnO2)-based lithium-ion battery (LIB) electrodes is the volume expansion of SnO2 during the charge-discharge process. Additionally, the aggregation of SnO2 also deteriorates the performance of anode materials. In this study, we prepared SnO2 nanoflowers (NFs) using nanocrystalline cellulose (CNC) to improve the surface area, prevent the particle aggregation, and alleviate the change in volume of LIB anodes. Moreover, CNC served not only as the template for the synthesis of the SnO2 NFs but also as a conductive material, after annealing the SnO2 NFs at 800 °C to improve their electrochemical performance. The obtained CNC-SnO2NF composite was used as an active LIB electrode material and exhibited good cycling performance and a high initial reversible capacity of 891 mA h g-1, at a current density of 100 mA g-1. The composite anode could retain 30% of its initial capacity after 500 charge-discharge cycles.

Characteristics of Perovskite Solar Cells According to Thickness of Doped ZnGa2O4 Down-Converting Thin Film.

A ZnGa2O4:Eu3+ layer was deposited on the incident surface of a perovskite solar cell (PSC) to convert ultraviolet rays into current within the solar cell. The ZnGa2O4:Eu3+ layer was deposited using the sol-gel method, and the thickness of the film was controlled using the number of spin coatings. When the coating was applied six times, a layer with almost no oscillation due to reflection was fabricated. It was confirmed that the efficiency of the PSC was not adversely affected by the coating. In addition, generation of a current by converting ultraviolet radiation within the solar cell was confirmed.

Improvement of Characteristics of Metal Doped TiO2 Thin Film and Application to Perovskite Solar Cell.

Over the past three decades, the development of renewable energy technologies has attracted significant attention to overcome both environmental pollution and global warming. Recently, a new type of solar cell based on an organic-inorganic halide perovskite material has been developed. Perovskite solar cells (PSC) were first reported in 2009; their efficiencies increased rapidly from 3.8% to 22%. PSCs have many advantages owing to their use of simple processing technology and stable materials. Perovskite materials have a general formula of ABX, where A is generally methyl ammonium CH3NH3+ (MA), B is a metal ion, such as Pb or Sn, and × represents a halogen ion. A distinct advantage of lead-based perovskites (i.e., MAPbX3) is that their band gaps can be easily tuned, from 1.2 to 2.3 eV, by varying their compositions and anions. Titanium dioxide is as often used as an electron transport layer due to its high chemical and optical stability, non-toxicity, low cost, and resistance to corrosion. TiO2 films can be characterized by the defects in their preparation, such as density fluctuations, pinholes, and cracks; these defects can reduce electrical conductivity and cause recombination. In this study, we have demonstrated that the electrical conductivity of TiO2 thin films is improved by its doping with Al3+. When applied to a PSC, the doped thin film improves the charge transfer of the solar cell and increases its efficiency. Our results suggest that Al3+ nanoparticles in the TiO2 layer may contribute to the improvement of the PSC.

Low-Temperature Thermally Evaporated SnO2 Based Electron Transporting Layer for Perovskite Solar Cells with Annealing Process.

Perovskite solar cells (PSCs) represent the third generation of solar cells that comprise a semiconductor electrode, a counter electrode, and an electrolyte. Perovskite solar cells (PSCs) have been comprehensively researched and led to an impressive improvement in a short period of time as cheaper alternatives to silicon solar cells due to their high energy-conversion efficiency and low production cost. Tin oxide (SnO2) has attracted attention as a promising candidate for electron transport material of perovskite solar cells, because it can be easily processed by low annealing temperature and solution processing method. However, in the fabrication of SnO2 electron transfer layer (ETL) via the conventional solution method, it is greatly difficult to increase the size of the substrate by the solution treatment method or to commercialize it. In this work, we report the photovoltaic characteristics of SnO2 based electron transport layer for perovskite solar cells (PSCs) fabricated by the thermal-evaporation processing method. The deposited SnO2 layer with the thermal evaporator is known to be not crystallographically stable. To solve this problem, we performed the annealing process at relatively low temperature (below 200 °C). As a result, we could confirm the optimum annealing temperature and we could demonstrate PSCs with thermally deposited SnO2 as the compact electron transport layer through a low-temperature annealing process. It would contribute to new opportunities in commercialization and development of perovskite solar cells.

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.