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We propose a magnetron sputtering technique to enhance HER and OER performance with a bifunctional vanadium-substituted NiFe-based catalyst electrode formed into a NiFeV-oxide thin film. The sputtering approach generates oxygen vacancies by creating nonstoichiometric oxidation phases, i.e., Fe3O4−x and VO2−y. Operando Raman spectroscopy reveals a synergistic effect between active metal sites and oxygen vacancies to promote the formation of a reconstructed active layer, i.e., NiFe(oxy)hydroxyl, during anodic oxidation. This phase transition optimizes the adsorption energy of water intermediates to accelerate the water splitting. Moreover, the leaching of vanadium also plays a vital role in the activation and surface restructuring processes of the NiFeV-oxide pre-catalyst during OER electrocatalysis. Feasibility studies for an NFV-0.7(−)‖NFV-0.7(+) stack-cell electrolyzer indicate that it delivers a high current density of 1000 mA cm−2 at low cell potentials of 2.00 V (without cell heating) and 1.84 V (at 60 °C) and exhibits excellent stability at 1000 mA cm−2 over 100 h. Our work offers a new paradigm for designing efficient bifunctional electrocatalysts, holding great promise for industrial-scale water splitting. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS2) have received a great deal of attention for high-performance gas sensing applications. Unfortunately, before their translation to commercial use, several scientific problems remain to be solved. The challenges include poor stability in a humid environment, random deposition manner of MoS2 flakes that makes the process unscalable, and incomplete recovery at room temperature. Herein, we report a strategy for the room-temperature volatile organic compound (VOC) sensor using the optical microfiber sensing technology. We demonstrated well-controlled immobilization of MoS2 nanosheets onto the optical sensing region using the optical deposition technique. The experimental results show that the MoS2-functionalized optical microfiber sensor achieves high selectivity to polar aprotic and nonpolar VOCs. The sensor demonstrated high sensitivity of 0.0195, 0.0143, 0.0072, and 0.0058 nm/ppm to acetone, ethyl acetate, cyclohexane, and IPA, respectively. Finally, the repeatability and complete recovery capabilities of the sensor have also been validated in this work. [ABSTRACT FROM AUTHOR]

This study proposes the use of thiomalic acid-modified Au and Ag nanoparticle mixtures (TMA-Au/AgNP mixes) for the selective detection of tricyclazole. Upon the addition of tricyclazole, the color of TMA-Au/AgNP mixes solution changes from orange-red to lavender (red-shift). According to the density-functional theory calculations, tricyclazole-induced aggregation of TMA-Au/AgNP mixes through electron donor-acceptor interactions was proved. The sensitivity and selectivity of the proposed method are affected by the amount of TMA, volume ratio of TMA-AuNPs to TMA-AgNPs, pH value, and buffer concentration. The ratio of absorbance (A 654 /A 520 ) of TMA-Au/AgNP mixes solution is proportional to the concentration of tricyclazole over the range 0.1-0.5 ppm with a linear correlation (R 2 = 0.948). Moreover, the limit of detection was estimated at 0.028 ppm. The practicality of TMA-Au/AgNP mixes was validated for the determination of tricyclazole concentration in real samples (spiked recovery was 97.5%-105.2%), demonstrating its advantages of simplicity, selectivity, and sensitivity.

T follicular helper (Tfh) cells are defined by a Bcl6 + CXCR5 hi PD-1 hi phenotype, but only a minor fraction of these reside in germinal centers (GCs). Here, we examined whether GC-resident and -nonresident Tfh cells share a common physiology and function. Fluorescently labeled, GC-resident Tfh cells in different mouse models were distinguished by low expression of CD90. CD90 neg/lo GCTfh cells required antigen-specific, MHCII + B cells to develop and stopped proliferating soon after differentiation. In contrast, nonresident, CD90 hi Tfh (GCTfh-like) cells developed normally in the absence of MHCII + B cells and proliferated continuously during primary responses. The TCR repertoires of both Tfh subsets overlapped initially but later diverged in association with dendritic cell-dependent proliferation of CD90 hi GCTfh-like cells, suggestive of TCR-dependency seen also in TCR-transgenic adoptive transfer experiments. Furthermore, the transcriptomes of CD90 neg/lo and CD90 hi GCTfh-like cells were enriched in different functional pathways. Thus, GC-resident and nonresident Tfh cells have distinct developmental requirements and activities, implying distinct functions., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Fenton's reagent provides a method to produce active hydroxyl radicals (˙OH) for chemical oxidation by mixing iron oxide and hydrogen peroxide, which divides into homogeneous and heterogeneous Fenton's reagent. Heterogeneous Fenton's reagent is fabricated from H 2 O 2 and various iron oxide solid materials, such as α-FeOOH, α-Fe 2 O 3 , and Fe 3 O 4 . Fe 3 O 4 possesses the Fe 2+ /Fe 3+ mixed valence oxidational state and has been reported to have good catalytic activity. However, the reaction mechanism of H 2 O 2 decomposition on Fe 3 O 4 surfaces is still unclear. In this work, we performed DFT calculations to investigate the H 2 O 2 decomposition mechanisms over the Fe 3 O 4 (311) surface. There are two iron environments for H 2 O 2 adsorption and decomposition on the Fe 3 O 4 (311) surface, a Fe 2+ /Fe 3+ environment and a Fe 3+ /Fe 3+ environment. We found that the H 2 O 2 can adsorb on the Fe 2+ /Fe 3+ environment by molecular adsorption but by dissociative adsorption on the Fe 3+ /Fe 3+ environment. Our results show that both adsorption structures can produce two OH groups on the Fe 3 O 4 (311) surface thermodynamically. In addition, based on the electronic property analysis, H 2 O 2 on the Fe 2+ /Fe 3+ environment follows the Haber-Weiss mechanism to form one OH anion and one OH radical. On the other hand, H 2 O 2 on the Fe 3+ /Fe 3+ environment follows the radical mechanism to form two OH radicals. In particular, the OH radical formed on Fe 2+ /Fe 3+ has energy levels on both sides of the Fermi energy level. It can be expected that this OH radical has good redox activity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Janus 2D transition metal dichalcogenide (TMD) is a new generation 2D material with a unique asymmetric structure. This asymmetric structure (or out-off plane symmetric geometry) of Janus 2D TMD has been reported to yield tunable electronic properties through strain and electric field, which can also be applied in gas sensing. In this work, we performed DFT calculations to investigate the gas sensing property of cyclohexane and acetone on MoS 2 and Janus MoSSe monolayers under external electric fields. Our results show that cyclohexane possesses slightly larger adsorption energy on pristine MoS 2 and Janus MoSSe monolayers than acetone without external electric fields. After applying the external electric fields, the adsorption energy for cyclohexane on MoS 2 shows no enhancement. However, the adsorption energy of acetone shows the most substantial enhancement on the Janus MoSSe monolayer. We found that the dipole moment orientations of adsorbates and the monolayer can strongly interact with the external electric fields. Hence, the combination of polar adsorbate and polar material, i.e. , acetone and Janus MoSSe, demonstrates the most vital sensitivity under the applied bias. On the other hand, the non-polar adsorbate and non-polar material combination show a negligible effect on external bias. These findings can be applied to the design of gas sensors in the future through polar materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)