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Zeolitic imidazolate frameworks (ZIFs) are a series of materials composited by metal ions and organic ligands with high specific surface area, which might be great precursors to produce metal oxides by calcination for gas sensor application. However, Zn-ZIF (ZIF-8) is hard to transform as ZnO in air and keeping the unique framework simultaneously. In this work, Fe2+was introduced into the metal node to replace a part of Zn2+ions, and it could be oxidized as Fe3+in the calcination to facilitate the oxidation process of the 2-methylimdazole ligands to give Fe-ZnO complex shell with high specific surface area (108 m2/g) and abundant oxygen vacancies (48%). The micro electro mechanical systems (MEMS) sensor based on the 6%-Fe-ZnO complex shell performed outstanding gas sensing properties to the low-concentration acetone vapor, including high response (ΔR/Rg = 11.2 to 5 ppm acetone), superior selectivity (Sacetone/Sethanol = 5.6) and fast response speed (τres = 2.6 s). This work not only provided the research of an exceptional acetone MEMS sensor, but also induced a strategy to produce metal oxide derived from ZIFs with complex structures for the universal synthesis methodology.

Nanomaterials with natural enzyme-mimicking characteristics have aroused extensive attention in various fields owing to their economical price, ease of large-scale production, and environmental resistance. Previous investigations have demonstrated that composition, size, shape, and surface modification play important roles in the enzymelike activity of nanomaterials; however, a fundamental understanding of the crystal facet effect, which determines surface energy or surface reactivity, has rarely been reported. Herein, fluorite cubic CeO2nanocrystals with controllably exposed {111}, {100}, or {110} facets are fabricated as proof-of-concept candidates to study the facet effect on the peroxidase-mimetic activity. Both experiments and theoretical results show that {110}-dominated CeO2nanorods (CeO2NR) possess the highest peroxidase-mimetic activity due to the richest defects on their surfaces, which are beneficial to capture metal atoms to further enrich their artificial enzymatic functionality for cascade catalysis. For instance, the introduction of atomically dispersed Au on CeO2NR surfaces not only enhances the peroxidase activity but also endows the obtained catalyst with glucose oxidase (GOx)-mimicking activity, which realizes enzyme-free cascade reactions for glucose colorimetric detection. This work not only provides an understanding for crystal facet engineering of nanomaterials to enhance the catalytic activity but also opens up a new way for the design of biomimetic nanomaterials with multiple functions.

By using WCl6as a precursor and absolute ethanol as a solvent, ultrafine W18O49nanowires (UFNWs) were synthesized by a one-pot solution-phase method and used as gas sensing materials. Their crystal structure, morphology, and specific surface area can be regulated by controlling precisely the content of the WCl6precursor in the solution. It has been found that, when the content of the precursor is 4 mg/mL, the formed products are UFNWs with a diameter of about 0.8 nm, only one crystal plane [010] is exposed, and the specific surface area is 194.72 m2/g. After the gas sensing test, we found that they have excellent selectivity to acetone. The response of 50 ppm acetone reaches 48.6, the response and recovery times are 11 and 13 s, respectively. In order to evaluate the interaction between W18O49surfaces and different volatile organic compound (VOC) molecules, we simulated and calculated the adsorption energy (EAds) among different W18O49surfaces and different VOCs by DFT. The calculated results are in agreement with the experimental results, further confirming the ultrahigh selectivity of W18O49UFNWs to acetone. The above results demonstrate that the high selectivity of W18O49UFNWs to acetone is due to the exposure of its single crystal plane [010]. This work has practical significance for better detection of acetone.

CO2injection can simultaneously enhance oil recovery and carbon storage, but the stability of petroleum-water-CO2emulsion affcet the production process and carbon storage. Emulsion characteristics is typically assessed via Nuclear Magnetic Resonance (NMR). It is essential to develop a theory to unlock the mechanisms of experimentation for harnessing the full potential of NMR in assessing emulsion stability and comprehending complex multiphase systems. The theory integrates experiments and a “quasi-lattice wave” physical model to understand the microscale mechanisms in NMR measurements of crude oil emulsion properties, and uncover the “transfer-transition” mode of 1H quantum excited states, explaining T2relaxation. This forms a theoretical basis for numerical simulation of CPMG (Carr-Purcell-Meiboom-Gill) experiments by random walk algorithms and the boundary annihilation hypothesis. A strong link between NMR T2times and various character properties of Petroleum-Water-CO2Emulsion samples is reflected, such as environmental scale, viscosity, CO2adsorption, and molecular thermal motion. Additionally, parameter Θ was proposed to characterize emulsion stability, for penetrating the theory presented in this paper, and to provide a scientifically rigorous representation of crude oil emulsion stability. The experiments with CO2treatment on crude oil emulsions were performed, demonstrating a highly effective theoretical correlation between interfacial tension in crude oil emulsions and CO2pressure, with an exceptional fit to experimental data (R2 > 0.99). When the pressure of CO2treatment exceeds a critical threshold (approximately 17 MPa in this study), there is a substantial reduction in viscosity. Furthermore, a comparative assessment of samples before and after CO2treatment using the parameter Θ demonstrated its reliability as an indicator of emulsion stability. It revealed a significant reduction of over 50% in the linear fit residual variance of Θ before and after subjecting the sample to 10 MPa carbon dioxide treatment, highlighting improved fluctuation stability. The slope of the Θ linear regression function signifies temporal stability. In a sample with 20% water content, the time evolution of the water phase decreases by 3.04%, while the oil phase experiences a substantial 57.77% reduction. Simultaneously, the midpoint of the range of the Θ linear regression function represents the environmental scale. The water phase environment scale increases by 8.72%, while the oil phase environment scale decreases by 8.74%, highlighting spatial evolution patterns.

Developing a facile route to access active and well-defined single atom sites catalysts has been a major area of focus for single atoms catalysts (SACs). Herein, we demonstrate a simple approach to generate atomically dispersed platinum via a thermal emitting method using bulk Pt metal as a precursor, significantly simplifying synthesis routes and minimizing synthesis costs. The ammonia produced by pyrolysis of Dicyandiamide can coordinate with platinum atoms by strong coordination effect. Then, the volatile Pt(NH3)xcan be anchored onto the surface of defective graphene. The as-prepared Pt SAs/DG exhibits high activity for the electrochemical hydrogen evolution reaction and selective oxidation of various organosilanes. This viable thermal emitting strategy can also be applied to other single metal atoms, for example, gold and palladium. Our findings provide an enabling and versatile platform for facile accessing SACs toward many industrial important reactions.

Electroreduction of CO2into value-added products is an effective approach to remit the environmental and energy issues. However, the development of an effective, accessible, and simple method for mass production of electrocatalyst is challenging. Herein, we demonstrate the solid-state diffusion between the N-doped carbon phase and bulk Ni metal can be utilized to synthesize hierarchical, self-supported, and atomistic catalyst. Strikingly, this hierarchical catalyst is programmable and scalable to meet the industrial demand and can be directly used as a binder-free electrode toward the CO2electroreduction, delivering a state-of-the-art current density of 48.66 mA cm−2at −1.0 V versus reversible hydrogen electrode (RHE) and high faradic efficiency of 97% to CO. The selectivity can be retained over 90% in a wide range of working potential of −0.7 to −1.2 V versus RHE. This solid-state diffusion strategy presents great potential to produce hierarchical and atomistic catalysts at industrial levels.