A Fe Single Atom Seed-Mediated Strategy Toward Fe3 C/FeNC Catalysts with Outstanding Bifunctional ORR/OER Activities.

The discovery of low-cost and high-performance bifunctional oxygen electrocatalysts is vital to the future commercialization of rechargeable zinc-air batteries (ZABs). Herein, a Fe single atom seed-mediated strategy is reported for the fabrication of Fe3 C species closely surrounded by FeN4 C active sites with strong electronic interactions built between them and more importantly, creating optimized coordination environment, via subtly adjusting their ratio, for favorable adsorption energies of oxygen intermediates formed during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Concretely, the voltage difference (ΔE) between the ORR half-wave and OER potential at a current density of 10 mA cm-2 for the compositionally-optimized FeNC/Fe3 C-op electrocatalyst is only 0.668 V, endowing itself one of the best bifunctional OER/ORR benchmarks. As a demo, ZABs assembled with FeNC/Fe3 C-op as the air cathode deliver a remarkable specific capacity (818.1 mAh gZn -1 ) and a power density (1013.9 mWh gZn -1 ), along with excellent long-term durability (>450 h). This work extends the methodology to modulate the activity of FeN4 C atomic site, undoubtedly inspiring wide explorations on the precise design of bifunctional oxygen electrocatalysts.

Enhanced ammonia sensing response based on Pt-decorated Ti3C2Tx/TiO2composite at room temperature.

Herein, we report a Pt-decorated Ti3C2Tx/TiO2gas sensor for the enhanced NH3sensing response at room temperature. Firstly, the TiO2nanosheets (NSs) arein situgrown onto the two-dimensional (2D) Ti3C2Txby hydrothermal treatment. Similar to Ti3C2Txsensor, the Ti3C2Tx/TiO2sensor has a positive resistance variation upon exposure to NH3, but with slight enhancement in response. However, after the loading of Pt nanoparticles (NPs), the Pt-Ti3C2Tx/TiO2sensor shows a negative response with significantly improved NH3sensing performance. The shift in response direction indicates that the dominant sensing mechanism has changed under the sensitization effect of Pt NPs. At room temperature, the response of Pt-Ti3C2Tx/TiO2gas sensor to 100 ppm NH3is about 45.5%, which is 13.8- and 10.8- times higher than those of Ti3C2Txand Ti3C2Tx/TiO2gas sensors, respectively. The experimental detection limit of the Pt-Ti3C2Tx/TiO2gas sensor to detect NH3is 10 ppm, and the corresponding response is 10.0%. In addition, the Pt-Ti3C2Tx/TiO2gas sensor shows the fast response/recovery speed (23/34 s to 100 ppm NH3), high selectivity and good stability. Considering both the response value and the response direction, the corresponding gas-sensing mechanism is also deeply discussed. This work is expected to shed a new light on the development of noble metals decorated MXene-metal oxide gas sensors.

[A cross-sectional study of early-onset epilepsy of intracerebral hemorrhage and construction of a risk prediction model].

OBJECTIVE: To study the early-onset epilepsy of intracerebral hemorrhage and build a prediction model to evaluate its prediction efficiency. METHODS: A cross-sectional investigation was conducted to construct a specialized optimized prediction model. The prediction model was converted into a visual optimized scoring scale, so as to quantify the probability of secondary epilepsy after intracerebral hemorrhage. Based on the current prediction model of acute cerebral infraction and post-stroke seizure (AIS-PSS), the evaluation efficacy of optimized score for secondary epilepsy after hemorrhagic stroke was explored. RESULTS: (1) After sample size calculation and sufficient inclusion and exclusion, 159 patients with cerebral hemorrhage were continuously selected as the model group of this cross-sectional study. A total of 29 patients with early-onset epilepsy and 130 patients without secondary epilepsy were enrolled. The time span was from January 2021 to August 2021. In addition, 77 patients with acute cerebral hemorrhage from August 2021 to February 2022 were selected as the verification group, among which 12 patients had early-onset epilepsy and 65 patients had not any secondary epilepsy. (2) There were significant differences in demographic characteristics such as diabetes history, cerebral infarction history, smoking history, National Institutes of Health Stroke Scale (NIHSS) score, intracerebral hemorrhage hematoma volume, serum creatinine (SCr), neuron-specific enolase (NSE), S-100 protein and intracerebral hemorrhage site between the two model groups with different prognosis (all P < 0.05). (3) The above indexes were included in univariate and multivariate Poisson regression analysis, and the results showed that the duration of diabetes [relative risk (RR) = 1.229, 95% confidence interval (95%CI) was 1.065-1.896, P = 0.036], smoking history (RR = 1.419, 95%CI was 1.133-2.160, P = 0.030), history of cerebral infarction (RR = 1.634, 95%CI was 1.128-2.548, P = 0.041), hematoma volume of cerebral hemorrhage (RR = 1.222, 95%CI was 1.024-2.052, P = 0.041), NES content (RR = 1.146, 95%CI was 1.041-1.704, P = 0.032), were independent influencing factors to constitute the prediction model. The prediction model was converted into a visual optimized scoring scale in the form of a line diagram to obtain the prediction probability corresponding to the corresponding score. (4) Receiver operator characteristic curve (ROC curve) was used to test the evaluation efficiency of optimized score and AIS-PSS score for early-onset cerebral hemorrhage epilepsy. Relevant data of patients in the verification group were extracted according to the information of two scores, and the final score of each patient in the verification group was obtained. The score and prognosis were put into the ROC curve to evaluate the predictive ability of different prediction models. The results showed that the cut-off value of the optimized score and the AIS-PSS score were 144 points and 7 points, respectively, and the area under the ROC curve (AUC) and the Yoden index of the optimized score were slightly lower than the AIS-PSS score. However, compared with AIS-PSS score, there was no significant difference in the evaluation efficiency of optimized score for early-onset epilepsy (Z = 1.874, P > 0.05). CONCLUSIONS: This study constructed a specific early-onset epilepsy prediction model for patients with hemorrhagic stroke, and transformed it into an optimized score that is easy for clinical use, and its evaluation efficiency is reliable.

Hierarchical SnO2nanoflower sensitized by BNQDs enhances the gas sensing performances to BTEX.

In this study, the SnO2nanoflowers with hierarchical structures sensitized by boron nitride quantum dots (BNQDs) were prepared through a simple hydrothermal method. It was applied for the detection of the BTEX vapors. Further investigation showed that the response value of SnO2sensitized by different amounts of BNQDs to the BTEX gases have a certain improvement. Especially 10-BNQDs/SnO2gas sensor exhibited a significant improvement in gas sensing performance and its response values to different BTEX gases was increased up to 2-4 folds compared with the intrinsic SnO2sensor. In addition, SnO2nanoflowers based gas sensor showed surprisingly fast response and recovery time for BTEX gases with 1-2 s. That can be attributed to the sensitization of BNQDs and the hierarchical structure of SnO2nanoflowers, which provided an easy channel for the gas diffusion. An economically viable gas sensor based on BNQDs sensitized SnO2nanoflowers exhibited a great potential in BTEX gas detection due to the simple synthesis method, environmentally friendly raw materials and excellent gas sensing performance.

Synthesis, structure and physical properties of the new layered oxyselenides Bi2LnO4Cu2Se2 (Ln = rare earth).

We have synthesized a new series of layered oxyselenides Bi2LnO4Cu2Se2 (Ln=Nd, Sm, Eu, Dy, Er, Yb). Their crystal structures and physical properties were studied through X-ray diffraction, electric transport measurements, bulk magnetization and first-principle calculation. All these compounds have a tetragonal structure with space group I4/mmm. They exhibit hole-type metallic behaviours which is also verified by the DFT calculation. The new Bi2LnO4-type block in these compounds may give people some enlightenment in synthesizing new iron-based superconductors or other layered compounds.

The tunable negative thermal expansion covering a wide temperature range around room temperature in Sn, Mn co-substituted Mn3ZnN.

Based on anti-perovskite Mn3ZnN, the negative thermal expansion (NTE) temperature can be effectively broadened via co-substituting Sn, Mn. Using optimized components, the room-temperature NTE effect covering a wide temperature range can be realized. Both the competing ferromagnetic order from Mn and local lattice disorder from Sn should be the reason for the physical origination of the broadening of the NTE temperature. By compositing with epoxy, the low thermal expansion could be achieved around room temperature, which exhibits great potential in the field of electronic packaging.

Fabrication of ZnO Nanoparticles Modified by Uniformly Dispersed Ag Nanoparticles: Enhancement of Gas Sensing Performance.

Zinc oxide (ZnO) nanoparticles modified with uniformly dispersed silver (Ag) nanoparticles (Ag-ZnO) were prepared in one step by calcining precursor electrospun nanofibers. The molar ratios of Ag to Zn in the precursor solutions were 0, 1, 3, and 5%. The microstructure of the Ag-ZnO sensor was characterized by scanning electron microscopy and transmission electron microscopy. The existence of metallic Ag was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy, and the gas sensing properties of Ag-ZnO were investigated. The results showed that the ZnO nanoparticles after Ag nanoparticles modification exhibited excellent gas sensing performance to ethanol and hydrogen sulfide (H2S). The optimal working temperature of the Ag-ZnO sensor significantly decreased for ethanol compared with pure ZnO. The 3% Ag-ZnO sensor exhibited the fastest response to ethanol with the response/recovery times of only 5 and 9 s, respectively. However, all the Ag-ZnO-based gas sensors showed a high response value to H2S, especially the 3% Ag-ZnO gas sensor exhibited a maximum response value of 298 at 10 ppm H2S. These results could be attributed to the spillover effect and electron sensitization effect of Ag nanoparticles, which led to more absorbed oxygen species and active sites, and thereby can further enhance the gas sensing performances of ZnO-based gas sensors.

In Situ Growing Double-Layer TiO2 Nanorod Arrays on New-Type FTO Electrodes for Low-Concentration NH3 Detection at Room Temperature.

A novel double-layer TiO2 nanorod array (NRA) gas sensor for room-temperature detection of NH3 was fabricated by employing etched fluorine-doped tin dioxide (FTO) glass as the in situ growing substrate and the new-type gas-sensing electrode via the facile droplet-coating and hydrothermal methods. Due to the synergistic effect of forces, special double-layer TiO2 NRAs with a cross-linked and bridgelike structure is formed, in which adequate point junctions can be generated to construct self-assembled electron pathways required for gas-sensing tests. Gas-sensing tests indicate that all samples obtained at different growth times have an excellent gas-sensing response to low-concentration NH3 at room temperature. Among them, the TiO2 NRAs obtained at 6 h (S2) exhibit the highest gas-sensing response to 100 ppm NH3 with a value of 102%. In addition, the growth mechanism, the gas reaction mechanism, and the effect of humidity on the gas-sensing performance are also discussed in the present paper.

Low-temperature operating ZnO-based NO2 sensors: a review.

Owing to its excellent physical and chemical properties, ZnO has been considered to be a promising material for development of NO2 sensors with high sensitivity, and fast response and recovery. However, due to the low activity of ZnO at low temperature, most of the current work is focused on detecting NO2 at high operating temperatures (200-500 °C), which will inevitably increase energy consumption and shorten the lifetime of sensors. In order to overcome these problems and improve the practicality of ZnO-based NO2 sensors, it is necessary to systematically understand the effective strategies and mechanisms of low-temperature NO2 detection of ZnO sensors. This paper reviews the latest research progress of low-temperature ZnO nanomaterial-based NO2 gas sensors. Several efficient strategies to achieve low-temperature NO2 detection (such as morphology modification, noble metal decoration, additive doping, heterostructure sensitization, two-dimensional material composites, and light activation) and corresponding sensing mechanisms (such as depletion layer theory, grain boundary barrier theory, spill-over effects) are also introduced. Finally, the challenges and future development directions of low-temperature ZnO-based NO2 sensors are outlined.

The 2D Porous g-C3N4/CdS Heterostructural Nanocomposites with Enhanced Visible-Light-Driven Photocatalytic Activity.

In this study, the 2D porous graphitic carbon nitride (g-C3N4) nanosheets were successfully fabricated via a facile thermal decomposition polymerization method without any help of templates, and then novel porous g-C3N4/CdS complex catalysts of different mass fractions were is situ synthesized by a simple solvothermal process. The results of photocatalytic experiments demonstrate that the coupling g-C3N4/CdS cocatalysts exhibit significant enhanced visible-light-driven photocatalytic activity for the decolorization of methyl orange (MO) compared with individual porous g-C3N4 and CdS. In particular, an optimal porous g-C3N4 content in the hybridized composite has been determined to be 70 wt.%, corresponding to pseudo-first-order rate constant of 0.046 min-1, which is 7 and 11 times faster than that of pure porous g-C3N4 and CdS, respectively. Photoluminescence (PL) spectroscopy measurements clearly confirmed that the recombination of photoproduced electrons and holes in g-C3N4/CdS composites was efficiently inhibited due to the formation of heterojunctions. Furthermore, the possible mechanism of enhanced photocatalytic activity and photostability of prous g-C3N4/CdS are also tentatively proposed.

Improving Photocatalytic Degradation Activity of Organic Pollutant by Sn4+ Doping of Anatase TiO2 Hierarchical Nanospheres with Dominant {001} Facets.

Herein, high-energy {001} facets and Sn4+ doping have been demonstrated to be effective strategies to improve the surface characteristics, photon absorption, and charge transport of TiO2 hierarchical nanospheres, thereby improving their photocatalytic performance. The TiO2 hierarchical nanospheres under different reaction times were prepared by solvothermal method. The TiO2 hierarchical nanospheres (24 h) expose the largest area of {001} facets, which is conducive to increase the density of surface active sites to degrade the adsorbed methylene blue (MB), enhance light scattering ability to absorb more incident photons, and finally, improve photocatalytic activity. Furthermore, the SnxTi1-xO2 (STO) hierarchical nanospheres are fabricated by Sn4+ doping, in which the Sn4+ doping energy level and surface hydroxyl group are beneficial to broaden the light absorption range, promote the generation of charge carriers, and retard the recombination of electron-hole pairs, thereby increasing the probability of charge carriers participating in photocatalytic reactions. Compared with TiO2 hierarchical nanospheres (24 h), the STO hierarchical nanospheres with 5% nSn/nTi molar ratio exhibit a 1.84-fold improvement in photodegradation of MB arising from the enhanced light absorption ability, increased number of photogenerated electron-hole pairs, and prolonged charge carrier lifetime. In addition, the detailed mechanisms are also discussed in the present paper.

Low-Cost and High-Performance ZnO Nanoclusters Gas Sensor Based on New-Type FTO Electrode for the Low-Concentration H2S Gas Detection.

A low-cost and high-performance gas sensor was fabricated by the in-situ growing of ZnO nanoclusters (NCs) arrays on the etched fluorine-doped tin dioxide (FTO) glass via a facile dip-coating and hydrothermal method. Etched FTO glass was used as a new-type gas-sensing electrode due to its advantages of being low cost and having excellent thermal and chemical stability. ZnO NCs are composed of multiple ZnO nanorods and can provide adequate lateral contacts to constitute the paths required for the gas-sensing tests simultaneously, which can provide many advantageous point junctions for the detection of low-concentration gases. The gas-sensing tests indicate that the ZnO NCs gas sensor has good selectivity and a high response for the low-concentration H2S gas. The sensing response has reached 3.3 for 500 ppb H2S at 330 °C. The excellent gas-sensing performances should be attributed to the large specific surface area of in-situ grown ZnO NCs, the perfect ohmic contact between ZnO NCs and FTO electrode and the variation of grain boundary barrier at the cross-linked junctions of multiple nanorods. In addition, the detailed effect of work temperature and gas concentration on gas-sensing, the stability of gas sensors and the corresponding response mechanism are also discussed in the present paper.

Effect of Surfactants on the Microstructures of Hierarchical SnO2 Blooming Nanoflowers and their Gas-Sensing Properties.

Hierarchical SnO2 blooming nanoflowers were successfully fabricated via a simple yet facile hydrothermal method with the help of different surfactants. Here we focus on exploring the promotion effects of surfactants on the self-assembly of 2D SnO2 nanosheets into 3D SnO2 flower-like structures as well as their gas-sensing performances. The polyporous flower-like SnO2 sensor exhibits excellent gas-sensing performances to ethanol and H2S gas due to high porosity when polyvinyl pyrrolidone is added into the precursor solution as a surfactant. The response/recovery times were about 5 s/8 s for 100 ppm ethanol and 4 s/20 s for 100 ppm H2S, respectively. Especially, the maximum response value of H2S is estimated to be 368 at 180 °C, which is one or two orders of magnitude higher than that of other test gases in this study. That indicates that the sensor fabricated with the help of polyvinyl pyrrolidone has good selectivity to H2S.

Tactile-Sensing Based on Flexible PVDF Nanofibers via Electrospinning: A Review.

The flexible tactile sensor has attracted widespread attention because of its great flexibility, high sensitivity, and large workable range. It can be integrated into clothing, electronic skin, or mounted on to human skin. Various nanostructured materials and nanocomposites with high flexibility and electrical performance have been widely utilized as functional materials in flexible tactile sensors. Polymer nanomaterials, representing the most promising materials, especially polyvinylidene fluoride (PVDF), PVDF co-polymer and their nanocomposites with ultra-sensitivity, high deformability, outstanding chemical resistance, high thermal stability and low permittivity, can meet the flexibility requirements for dynamic tactile sensing in wearable electronics. Electrospinning has been recognized as an excellent straightforward and versatile technique for preparing nanofiber materials. This review will present a brief overview of the recent advances in PVDF nanofibers by electrospinning for flexible tactile sensor applications. PVDF, PVDF co-polymers and their nanocomposites have been successfully formed as ultrafine nanofibers, even as randomly oriented PVDF nanofibers by electrospinning. These nanofibers used as the functional layers in flexible tactile sensors have been reviewed briefly in this paper. The ß-phase content, which is the strongest polar moment contributing to piezoelectric properties among all the crystalline phases of PVDF, can be improved by adjusting the technical parameters in electrospun PVDF process. The piezoelectric properties and the sensibility for the pressure sensor are improved greatly when the PVDF fibers become more oriented. The tactile performance of PVDF composite nanofibers can be further promoted by doping with nanofillers and nanoclay. Electrospun P(VDF-TrFE) nanofiber mats used for the 3D pressure sensor achieved excellent sensitivity, even at 0.1 Pa. The most significant enhancement is that the aligned electrospun core-shell P(VDF-TrFE) nanofibers exhibited almost 40 times higher sensitivity than that of pressure sensor based on thin-film PVDF.