In article number 2419790, Il-Doo Kim and co-workers demonstrate that ultrafast photothermal annealing enables the synthesis of metastable transition metal dichalcogenides (TMDs) and carbides (TMCs) with precise structural and phase control. By reaching temperatures above 3000 K within milliseconds under ambient conditions, the method facilitates the formation of core@shell heterostructures and phase-transformed nanomaterials, which exhibit excellent catalytic performance for energy and environmental applications. Based on this concept, the proposed image visually captures the central concept of the study: the rapid formation of core@shell heterostructures comprising TMD shells and diverse core materials via millisecond-scale thermal shock.

The synthesis of high-entropy alloy nanoparticles (HEA NPs) on oxide supports with a uniform and homogeneous distribution has been a significant challenge in traditional carbothermal shock (CTS) methods. In this study, we introduce a carbide-induced thermal shock (CITS) process for synthesizing HEA NPs anchored on tungsten trioxide (WO3) nanofibers. Utilizing one-dimensional (1D) tungsten carbide (WC) nanofibers (NFs) as scaffolds, we facilitated their oxidation to WO3 while preserving structural integrity. This approach resulted in the formation of ultrasmall HEA NPs (1–3 nm) strongly anchored on the WO3 NFs, preventing grain growth and enabling a core–shell microstructure. The functionalized WO3 NFs with homogeneously distributed HEA NPs demonstrated significantly enhanced gas sensing performance, especially for hydrogen sulfide (H2S), with a response (Rair/Rgas) of 22.1 at 5 ppm. This improvement is attributed to the CITS process, which enhances the chemisorption of oxygen species and increases the density of Lewis acid sites, leading to superior catalytic performance and stability. The findings from this study demonstrate the effectiveness of the CITS method in synthesizing highly active oxide-based catalysts and its potential applications in advanced gas sensing technologies under extreme conditions.

Liquid organic hydrogen carrier (LOHC) technology makes it possible to safely and easily store and transport hydrogen in large quantities for extended periods of time. To improve the efficiency of hydrogen supply via LOHC, there is a growing need for new LOHCs that exhibit high hydrogen storage capacity per unit volume and weight, efficient hydrogen release, low melting points for easy transport, and high boiling points for simplifying hydrogen purification, as well as cost-effective and large-scale production. Herein, we propose a promising LOHC candidate, 1-(n-phenylethyl)naphthalene (PEN), which has a high hydrogen storage capacity (60.8 kgH2·m–3), superior physical properties (wide liquid range, from −21 to 350 °C), and mass-produced compounds at low cost. PEN exhibited reversible hydrogen storage and release performance in consecutive cycles. Furthermore, we suggest an effective way to increase dehydrogenation performance by controlling the composition of stereoisomers generated during hydrogenation.

In article number 2105199, Yeon Sik Jung and co-workers achieve highly selective, quantitative, and multiplex detection of mixed trace level aromatic compound gases through synergistically integrated multimodal sensing. The design of the 3D cross-point multifunctional nanoarchitecture (3D-CMA) significantly enhances both chemoresistive sensing and surface-enhanced Raman spectroscopy simultaneously. 3D-CMA multimodal sensors accurately identify the composition and concentrations of mixed gases with very similar molecular structures.

It is evident that the exhaustive use of fossil fuels for decades has significantly contributed to global warming and environmental pollution. To mitigate the harm on the environment, lithium–oxygen batteries (LOBs) with a high theoretical energy density (3458 Wh kg–1Li2O2) compared to that of Li-ion batteries (LIBs) have been considered as an attractive alternative to fossil fuels. For this purpose, porous carbon materials have been utilized as promising air cathodes owing to their low cost, lightness, easy fabrication process, and high performance. However, the challenge thus far lies in the uncontrollable formation of Li2CO3 at the interface between carbon and Li2O2, which is detrimental to the stable electrochemical performance of carbon-based cathodes in LOBs. In this work, we successfully protected the surface of the free-standing carbon nanofibers (CNFs) by coating it with a layer of iridium metal through direct sputtering (CNFs@Ir), which significantly improved the lifespan of LOBs. Moreover, the Ir would play a secondary role as an electrochemical catalyst. This all-in-one cathode was evaluated for the formation and decomposition of Li2O2 during (dis)charging processes. Compared with bare CNFs, the CNFs@Ir cathode showed two times longer lifespan with 0.2 VLi lower overpotentials for the oxygen evolution reaction. We quantitatively calculated the contents of CO32– in Li2CO3 formed on the different surfaces of the bare CNFs (63% reduced) and the protected CNFs@Ir (78% reduced) cathodes after charging. The protective effects and the reaction mechanism were elucidated by ex situ analyses, including scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy.

Conductive porous materials having a high surface reactivity offer great promise for a broad range of applications. However, a general and scalable synthesis of such materials remains challenging. In this work, the facile synthesis of catalytic metal nanoparticles (NPs) embedded in 2D metal–organic frameworks (MOFs) is reported as highly active and conductive porous materials. After the assembly of 2D conductive MOFs (C-MOFs), i.e., Cu3(hexahydroxytriphenylene)2 [Cu3(HHTP)2], Pd or Pt NPs are functionalized within the cavities of C-MOFs by infiltration of metal ions and subsequent reduction. The unique structure of Cu3(HHTP)2 with a cavity size of 2 nm confines the bulk growth of metal NPs, resulting in ultra-small (≈2 nm) and well-dispersed metal NPs loaded in 2D C-MOFs. The Pd or Pt NPs-loaded Cu3(HHTP)2 exhibits remarkably improved NO2 sensing performance at room temperature due to the high reactivity of catalytic metal NPs and the high porosity of C-MOFs. The catalytic effect of Pd and Pt NPs on NO2 sensing of Cu3(HHTP)2, in terms of reaction rate kinetics and activation energy, is demonstrated.

Humidity sensors are essential components in wearable electronics for monitoring of environmental condition and physical state. In this work, a unique humidity sensing layer composed of nitrogen-doped reduced graphene oxide (nRGO) fiber on colorless polyimide film is proposed. Ultralong graphene oxide (GO) fibers are synthesized by solution assembly of large GO sheets assisted by lyotropic liquid crystal behavior. Chemical modification by nitrogen-doping is carried out under thermal annealing in H2(4%)/N2(96%) ambient to obtain highly conductive nRGO fiber. Very small (≈2 nm) Pt nanoparticles are tightly anchored on the surface of the nRGO fiber as water dissociation catalysts by an optical sintering process. As a result, nRGO fiber can effectively detect wide humidity levels in the range of 6.1–66.4% relative humidity (RH). Furthermore, a 1.36-fold higher sensitivity (4.51%) at 66.4% RH is achieved using a Pt functionalized nRGO fiber (i.e., Pt-nRGO fiber) compared with the sensitivity (3.53% at 66.4% RH) of pure nRGO fiber. Real-time and portable humidity sensing characteristics are successfully demonstrated toward exhaled breath using Pt-nRGO fiber integrated on a portable sensing module. The Pt-nRGO fiber with high sensitivity and wide range of humidity detection levels offers a new sensing platform for wearable humidity sensors.

The feature describes two different types of chemical sensors, i.e., chemiresistive type sensors and optical sensors. For the chemiresistive type sensors, electrical signals are modulated during the reaction with chemical gas species. On the other hand, distinctive color changes are occurred in the case of optical sensors after the reaction with chemical analytes. The feature is designed for the review paper about one-dimensional nanofibrous sensing structures for chemiresistive type sensors and optical sensors. This is reported by Seon-Jin Choi, Luana Persano, Andrea Camposeo, Ji-Soo Jang, Won-Tae Koo, Sang-Joon Kim, Hee-Jin Cho, Il-Doo Kim and Dario Pisignano, in article number 1600569.

As a futuristic diagnosis platform, breath analysis is gaining much attention because it is a noninvasive, simple, and low cost diagnostic method. Very promising clinical applications have been demonstrated for diagnostic purposes by correlation analysis between exhaled breath components and specific diseases. In addition, diverse breath molecules, which serve as biomarkers for specific diseases, are precisely identified by statistical pattern recognition studies. To further improve the accuracy of breath analysis as a diagnostic tool, breath sampling, biomarker sensing, and data analysis should be optimized. In particular, development of high performance breath sensors, which can detect biomarkers at the ppb-level in exhaled breath, is one of the most critical challenges. Due to the presence of numerous interfering gas species in exhaled breath, selective detection of specific biomarkers is also important.

This Account focuses on chemiresistive type breath sensors with exceptionally high sensitivity and selectivity that were developed by combining hollow protein templated nanocatalysts with electrospun metal oxide nanostructures. Nanostructures with high surface areas are advantageous in achieving high sensitivity because the sensing signal is dominated by the surface reaction between the sensing layers and the target biomarkers. Furthermore, macroscale pores between one-dimensional (1D) nanostructures can facilitate fast gas diffusion into the sensing layers. To further enhance the selectivity, catalytic functionalization of the 1D metal oxide nanostructure is essential. However, the majority of conventional techniques for catalytic functionalization have failed to achieve a high degree of dispersion of nanoscale catalysts due to aggregation on the surface of the metal oxide, which severely deteriorates the sensing properties by lowering catalytic activity. This issue has led to extensive studies on monolithically dispersed nanoscale particles on metal oxides to maximize the catalytic performances.

Achieving an improved understanding of catalyst properties, with ability to predict new catalytic materials, is key to overcoming the inherent limitations of metal oxide based gas sensors associated with rather low sensitivity and selectivity, particularly under highly humid conditions. This study introduces newly designed bimetallic nanoparticles (NPs) employing bimetallic Pt-based NPs (PtM, where M = Pd, Rh, and Ni) via a protein encapsulating route supported on mesoporous WO3 nanofibers. These structures demonstrate unprecedented sensing performance for detecting target biomarkers (even at p.p.b. levels) in highly humid exhaled breath. Sensor arrays are further employed to enable pattern recognition capable of discriminating between simulated biomarkers and controlled breath. The results provide a new class of multicomponent catalytic materials, demonstrating potential for achieving reliable breath analysis sensing.