Highly Sensitive and Selective Real-Time Breath Isoprene Detection using the Gas Reforming Reaction of MOF-Derived Nanoreactors.

Real-time breath isoprene sensing provides noninvasive methods for monitoring human metabolism and early diagnosis of cardiovascular diseases. Nonetheless, the stable alkene structure and high humidity of the breath hinder sensitive and selective isoprene detection. In this work, we derived well-defined CoO@polyoxometalate yolk-shell structures using a metal-organic framework template.

Exclusive detection of volatile aromatic hydrocarbons using bilayer oxide chemiresistors with catalytic overlayers.

The accurate detection and identification of volatile aromatic hydrocarbons, which are highly toxic pollutants, are essential for assessing indoor and outdoor air qualities and protecting humans from their sources. However, real-time and on-site monitoring of aromatic hydrocarbons has been limited by insufficient sensor selectivity. Addressing the issue, bilayer oxide chemiresistors are developed using Rh-SnO gas-sensing films and catalytic CeO overlayers for rapidly and cost-effectively detecting traces of aromatic hydrocarbons in a highly discriminative and quantitative manner, even in gas mixtures.

MOF-Based Chemiresistive Gas Sensors: Toward New Functionalities.

The sensing performances of gas sensors must be improved and diversified to enhance quality of life by ensuring health, safety, and convenience. Metal-organic frameworks (MOFs), which exhibit an extremely high surface area, abundant porosity, and unique surface chemistry, provide a promising framework for facilitating gas-sensor innovations. Enhanced understanding of conduction mechanisms of MOFs has facilitated their use as gas-sensing materials, and various types of MOFs have been developed by examining the compositional and morphological dependences and implementing catalyst incorporation and light activation.

Designing oxide chemiresistors for detecting volatile aromatic compounds: recent progresses and future perspectives.

Oxide chemiresistors have mostly been used to detect reactive gases such as ethanol, acetone, formaldehyde, nitric dioxide, and carbon monoxide. However, the selective and sensitive detection of volatile aromatic compounds such as benzene, toluene, and xylene, which are extremely toxic and harmful, using oxide chemiresistors remains challenging because of the molecular stability of benzene rings containing chemicals. Moreover, the performance of the sensing materials is insufficient to detect trace concentration levels of volatile aromatic compounds, which lead to harmful effects on human beings.

Highly Selective and Sensitive Detection of Breath Isoprene by Tailored Gas Reforming: A Synergistic Combination of Macroporous WO Spheres and Au Catalysts.

Precise detection of breath isoprene can provide valuable information for monitoring the physical and physiological status of human beings or for the early diagnosis of cardiovascular diseases. However, the extremely low concentration and low chemical reactivity of breath isoprene hamper the selective and sensitive detection of isoprene using oxide semiconductor chemiresistors. Herein, we report that macroporous WO microspheres whose inner macropores are surrounded by Au nanoparticles exhibit a high response (resistance ratio = 11.

Naturally diffused sintering aid for highly conductive bilayer electrolytes in solid oxide cells.

Solid oxide cells (SOCs) are promising sustainable and efficient electrochemical energy conversion devices. The application of a bilayer electrolyte comprising wide electrolytic oxide and highly conductive oxide is essential to lower the operating temperatures while maintaining high performance. However, a structurally and chemically ideal bilayer has been unattainable through cost-effective conventional ceramic processes.

Exclusive and ultrasensitive detection of formaldehyde at room temperature using a flexible and monolithic chemiresistive sensor.

Formaldehyde, a probable carcinogen, is a ubiquitous indoor pollutant, but its highly selective detection has been a long-standing challenge. Herein, a chemiresistive sensor that can detect ppb-level formaldehyde in an exclusive manner at room temperature is designed. The TiO sensor exhibits under UV illumination highly selective detection of formaldehyde and ethanol with negligible cross-responses to other indoor pollutants.

Visible-Light-Activated Type II Heterojunction in Cu(hexahydroxytriphenylene)/FeO Hybrids for Reversible NO Sensing: Critical Role of π-π* Transition.

Metal-organic frameworks (MOFs) with high surface area, tunable porosity, and diverse structures are promising platforms for chemiresistors; however, they often exhibit low sensitivity, poor selectivity, and irreversibility in gas sensing, hindering their practical applications. Herein, we report that hybrids of Cu(HHTP) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanoflakes and FeO nanoparticles exhibit highly sensitive, selective, and reversible detection of NO at 20 °C. The key parameters to determine their response, selectivity, and recovery are discussed in terms of the size of the Cu(HHTP) nanoflakes, the interaction between the MOFs and NO, and an increase in the concentration and lifetime of holes facilitated by visible-light photoactivation and charge-separating energy band alignment of the hybrids.

Topographically designed hybrid nanostructures via nanotransfer printing and block copolymer self-assembly.

Nanotransfer printing (nTP) has attracted much attention due to its high pattern resolution, simple process, and low processing cost for useful nanofabrication. Here, we introduce a thermally assisted nTP (T-nTP) process for the effective fabrication of various periodic three-dimensional (3D) nanosheets, such as concavo-convex lines, spine lines, square domes, and complex multi-line patterns. The T-nTP method allows continuous nanoscale 3D patterns with functionality to be transferred onto both rigid and flexible substrates by heat without any collapse of uniform convex nanostructures with nanochannels.

A Transparent Nanopatterned Chemiresistor: Visible-Light Plasmonic Sensor for Trace-Level NO Detection at Room Temperature.

The highly selective detection of trace gases using transparent sensors at room temperature remains challenging. Herein, transparent nanopatterned chemiresistors composed of aligned 1D Au-SnO nanofibers, which can detect toxic NO gas at room temperature under visible light illumination is reported. Ten straight Au-SnO nanofibers are patterned on a glass substrate with transparent electrodes assisted by direct-write, near-field electrospinning, whose extremely low coverage of sensing materials (≈0.

Highly Selective Detection of Benzene and Discrimination of Volatile Aromatic Compounds Using Oxide Chemiresistors with Tunable Rh-TiO Catalytic Overlayers.

Volatile aromatic compounds are major air pollutants, and their health impacts should be assessed accurately based on the concentration and composition of gas mixtures. Herein, novel bilayer sensors consisting of a SnO sensing layer and three different Rh-TiO catalytic overlayers ( = 0.5, 1, and 2 wt%) are designed for the new functionalities such as the selective detection, discrimination, and analysis of benzene, toluene, and -xylene.

Tailored Graphene Micropatterns by Wafer-Scale Direct Transfer for Flexible Chemical Sensor Platform.

2D materials, such as graphene, exhibit great potential as functional materials for numerous novel applications due to their excellent properties. The grafting of conventional micropatterning techniques on new types of electronic devices is required to fully utilize the unique nature of graphene. However, the conventional lithography and polymer-supported transfer methods often induce the contamination and damage of the graphene surface due to polymer residues and harsh wet-transfer conditions.

General Strategy for Designing Highly Selective Gas-Sensing Nanoreactors: Morphological Control of SnO Hollow Spheres and Configurational Tuning of Au Catalysts.

Catalyst-loaded hollow spheres are effective at detecting ethanol with high chemical reactivity. However, this has limited the widespread use of catalyst-loaded hollow spheres in designing highly selective gas sensors to less-reactive gases such as aromatics (e.g.

Functionalized Sulfide Solid Electrolyte with Air-Stable and Chemical-Resistant Oxysulfide Nanolayer for All-Solid-State Batteries.

Sulfide solid electrolytes (SEs) with high Li-ion conductivities (σ) and soft mechanical properties have limited applications in wet casting processes for commercial all-solid-state batteries (ASSBs) because of their inherent atmospheric and chemical instabilities. In this study, we fabricated sulfide SEs with a novel core-shell structure via environmental mechanical alloying, while providing sufficient control of the partial pressure of oxygen. This powder possesses notable atmospheric stability and chemical resistance because it is covered with a stable oxysulfide nanolayer that prevents deterioration of the bulk region.

Rational Design of Semiconductor-Based Chemiresistors and their Libraries for Next-Generation Artificial Olfaction.

Artificial olfaction based on gas sensor arrays aims to substitute for, support, and surpass human olfaction. Like mammalian olfaction, a larger number of sensors and more signal processing are crucial for strengthening artificial olfaction. Due to rapid progress in computing capabilities and machine-learning algorithms, on-demand high-performance artificial olfaction that can eclipse human olfaction becomes inevitable once diverse and versatile gas sensing materials are provided.

Highly Conductive and Flexible Dopamine-Graphene Hybrid Electronic Textile Yarn for Sensitive and Selective NO Detection.

Graphene-based electronic textile (e-textile) gas sensors have been developed for detecting hazardous NO gas. For the e-textile gas sensor, electrical conductivity is a critical factor because it directly affects its sensitivity. To obtain a highly conductive e-textile, biomolecules have been used for gluing the graphene to the textile surface, though there remain areas to improve, such as poor conductivity and flexibility.

Thermally assisted nanotransfer printing with sub-20-nm resolution and 8-inch wafer scalability.

Nanotransfer printing (nTP) has attracted considerable attention due to its good pattern resolution, process simplicity, and cost-effectiveness. However, the development of a large-area nTP process has been hampered by critical reliability issues related to the uniform replication and regular transfer printing of functional nanomaterials. Here, we present a very practical thermally assisted nanotransfer printing (T-nTP) process that can easily produce well-ordered nanostructures on an 8-inch wafer via the use of a heat-rolling press system that provides both uniform pressure and heat.

Conversion Reaction Mechanism of Ultrafine Bimetallic Co-Fe Selenides Embedded in Hollow Mesoporous Carbon Nanospheres and Their Excellent K-Ion Storage Performance.

Potassium-ion batteries (KIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundance and affordability of potassium. However, the development of suitable electrode materials that can stably store large-sized K ions remains a challenge. This study proposes a facile impregnation method for synthesizing ultrafine cobalt-iron bimetallic selenides embedded in hollow mesoporous carbon nanospheres (HMCSs) as superior anodes for KIBs.

A New Strategy for Detecting Plant Hormone Ethylene Using Oxide Semiconductor Chemiresistors: Exceptional Gas Selectivity and Response Tailored by Nanoscale CrO Catalytic Overlayer.

A highly selective and sensitive detection of the plant hormone ethylene, particularly at low concentrations, is essential for controlling the growth, development, and senescence of plants, as well as for ripening of fruits. However, this remains challenging because of the non-polarity and low reactivity of ethylene. Herein, a strategy for detecting ethylene at a sub-ppm-level is proposed by using oxide semiconductor chemiresistors with a nanoscale oxide catalytic overlayer.

Superionic Halogen-Rich Li-Argyrodites Using In Situ Nanocrystal Nucleation and Rapid Crystal Growth.

Although several crystalline materials have been developed as Li-ion conductors for use as solid electrolytes in all-solid-state batteries (ASSBs), producing materials with high Li-ion conductivities is time-consuming and cost-intensive. Herein, we introduce a superionic halogen-rich Li-argyrodite (HRLA) and demonstrate its innovative synthesis using ultimate-energy mechanical alloying (UMA) and rapid thermal annealing (RTA). UMA with a 49 G-force milling energy provides a one-pot process that includes mixing, glassification, and crystallization, to produce as-milled HRLA powder that is ∼70% crystallized; subsequent RTA using an infrared lamp increases this crystallinity to ∼82% within 25 min.

Investigation of Binary Metal (Ni, Co) Selenite as Li-Ion Battery Anode Materials and Their Conversion Reaction Mechanism with Li Ions.

Highly efficient anode materials with novel compositions for Li-ion batteries are actively being researched. Multicomponent metal selenite is a promising candidate, capable of improving their electrochemical performance through the formation of metal oxide and selenide heterostructure nanocrystals during the first cycle. Here, the binary nickel-cobalt selenite derived from Ni-Co Prussian blue analogs (PBA) is chosen as the first target material: the Ni-Co PBA are selenized and partially oxidized in sequence, yielding (NiCo)SeO phase with a small amount of metal selenate.

Metal Oxide Gas Sensors with Au Nanocluster Catalytic Overlayer: Toward Tuning Gas Selectivity and Response Using a Novel Bilayer Sensor Design.

Noble metals or oxide catalysts have traditionally been loaded or doped to enhance the gas sensing properties of oxide semiconductor chemiresistors. However, the selective detection of various chemicals for a wide range of new applications remains a challenging problem. In this paper, we propose a novel bilayer design with an oxide chemiresistor sensing layer and nanoscale catalytic Au overlayer to provide high controllability for gas sensing characteristics.

Humidity-Independent Gas Sensors Using Pr-Doped InO Macroporous Spheres: Role of Cyclic Pr/Pr Redox Reactions in Suppression of Water-Poisoning Effect.

Pure and 3-12 at. % Pr-doped InO macroporous spheres were fabricated by ultrasonic spray pyrolysis and their acetone-sensing characteristics under dry and humid conditions were investigated to design humidity-independent gas sensors. The 12 at.

Synthesis Process of CoSeO Microspheres for Unordinary Li-ion Storage Performances and Mechanism of Their Conversion Reaction with Li ions.

Multicomponent materials with various double cations have been studied as anode materials of lithium-ion batteries (LIBs). Heterostructures formed by coupling different-bandgap nanocrystals enhance the surface reaction kinetics and facilitate charge transport because of the internal electric field at the heterointerface. Accordingly, metal selenites can be considered efficient anode materials of LIBs because they transform into metal selenide and oxide nanocrystals in the first cycle.

Gas sensors using ordered macroporous oxide nanostructures.

Detection and monitoring of harmful and toxic gases have gained increased interest in relation to worldwide environmental issues. Semiconducting metal oxide gas sensors have been considered promising for the facile remote detection of gases and vapors over the past decades. However, their sensing performance is still a challenge to meet the demands for practical applications where excellent sensitivity, selectivity, stability, and response/recovery rate are imperative.