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Integrating real‐time electrical gas sensing and highly identifiable surface‐enhanced Raman spectroscopy (SERS) for volatile organic compounds (VOCs) monitoring holds significant potential for safeguarding public health and safety. However, this technique remains in the proof‐of‐concept stage because the performance and reproducibility of devices fall short of meeting the practical application requirements. This work addresses this challenge by employing vortex engineering on a bifunctional dual‐layer array of Ni‐doped SnO2 (Ni‐SnO2) bowl‐coated on Ni‐SnO2/Au/SiO2 and developing highly reproducible device fabrication. In the dual‐layer array, vortices generated in upper Ni‐SnO2 bowls slow down the VOC flow and direct its delivery to gaps between lower Ni‐SnO2/Au/SiO2 units that are critical to SERS and electrical sensing. Experimental results show that the vortex effect in the array enables a low limit of detection of 10 ppb with a response and recovery in seconds. The excellent practicality of the array has been demonstrated through a ca. 100 hours of quantitative dual‐monitoring of styrene in a spacious environment (~60 m3) with a 5‐meter distance between the leakage source and the array. This work advances dual‐monitoring sensors for practical applications and offers insights for designing gas‐sensing materials and devices. [ABSTRACT FROM AUTHOR]

Rapid urban development in China has aggravated land subsidence, which poses a potential threat to sustainable urban development. It is imperative to monitor and predict land subsidence over large areas. To address these issues, we chose Henan Province as the study area and applied small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) technology to obtain land deformation information for monitoring land subsidence from November 2019 to February 2022 with 364 multitrack Sentinel-1A satellite images. The current traditional time-series deep learning models suffer from the problems of (1) poor results in extracting a sequence of information that is too long and (2) the inability to extract the feature information between the influence factor and the land subsidence well. Therefore, a long short-term memory-temporal convolutional network (LSTM-TCN) deep learning model was proposed in order to predict land subsidence and explore the influence of environmental factors, such as the volumetric soil water layer and monthly precipitation, on land subsidence in this study. We used leveling data to verify the effectiveness of SBAS-InSAR in land subsidence monitoring. The results of SBAS-InSAR showed that the land subsidence in Henan Province was obvious and uneven in spatial distribution. The maximum subsidence velocity was −94.54 mm/a, and the uplift velocity was 41.23 mm/a during the monitoring period. Simultaneously, the land subsidence in the study area presented seasonal changes. The rate of land subsidence in spring and summer was greater than that in autumn and winter. The prediction accuracy of the LSTM-TCN model was significantly better than that of the individual LSTM and TCN models because it fully combined their advantages. In addition, the prediction accuracies, with the addition of environmental factors, were improved compared with those using only time-series subsidence information. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) provides an unprecedented opportunity for fingerprinting identification and trace-level detection in chemistry, biomedicine, materials, and so on. Although great efforts have been devoted to fabricating sensitive plasmonic nanomaterials, it is still challenging to batch-produce a SERS substrate with high sensitivity, good reproducibility, and perfect recyclability. Here, we describe a facile fabrication of three-dimensional (3D) hierarchical Au/CuS nanocomposites, in which high-density Au nanotips enable highly SERS-active sensing, and the well-defined microflower (MF) geometry produces perfect signal reproducibility (RSD < 5%) for large laser spot excitations (>50 μm2), which is particularly suitable for practical on-site detection with a handheld Raman spectrometer. In addition, a self-cleaning ability of this Au/CuS Schottky junction photocatalyst under sunlight irradiation allows complete removal of the adsorbed analytes, realizing perfect regeneration of the SERS substrates over many cycles. The mass-production, ultra-sensitive, high-reproducibility, and fast-recyclability features of hierarchical Au/CuS MFs greatly facilitate cost-effective and field SERS detection of trace analytes in practice. [ABSTRACT FROM AUTHOR]

This work proposes a novel and simple synthesis method for microporous‐ceria‐wrapped gold (Au@mp‐CeO2) nanoparticles (NPs) based on linker molecule‐induced stacking of ultrafine CeO2 particles (or beads) on the surface of pre‐prepared gold NPs. The resulting NPs have a uniform size and microporous CeO2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick. This method is universal and suitable for other metal@mp‐oxide nanoarchitectures (such as Au@mp‐CuO NPs, Au@mp‐Cr2O3 NPs, Ag@mp‐CeO2 NPs, and Ag@mp‐CeO2 nanowires) simply via changing the pre‐prepared metal cores or shell precursors. Most significantly, the as‐prepared Au@mp‐CeO2 NPs can be used for accurate monitoring of toluene vapor (10 ppm level) at room temperature based on their conductometric and surface‐enhanced Raman spectroscopy (SERS) dual response. Moreover, these NPs can be also used for other hazardous gases, such as chlorobenzene, hydrogen sulfide, and 1‐dodecanethiol. This excellent performance benefits from the micropore‐enhanced interaction between CeO2 and gas molecules. This work not only provides new and controllable preparation for metal@mp‐oxide nanoarchitectures, but also demonstrates the great potential applications of these materials in real‐time and identifiable monitoring of hazardous gases. [ABSTRACT FROM AUTHOR]

Silver (Ag)-based Janus nanoparticles (NPs) are of broad interest for extensive applications due to their excellent photoelectric performances and special structure. However, it still remains challenging to prepare this type of Janus NP with high uniformity in a large scale. Here, we present a facile wet-chemical strategy to synthesize Ag-MoS2 Janus NPs via adding an appropriate amount of AgNO3 into the MoS2 nanosphere (200 nm in size)-contained aqueous solution. These Janus NPs represent a new type of heterogeneous nanostructure. Each Janus NP is made up of one tiny-Ag-dot-decorated MoS2 nanosphere and one polyhedral Ag single crystal (∼100 nm in size), and both of them attach together, showing a snowman-like dimer. Such Janus NPs or dimers can not be detached by the ultrasonic vibration even with a high power, showing strong adhesion between them. Further, the morphology and size of the polyhedral Ag nanocrystals attached on MoS2 nanospheres can be controlled by the AgNO3 addition amount, reaction time, and temperature. A growth model is proposed to understand the formation of these Janus NPs, which is based on the tiny Ag dots' aggregation and oriented connection mechanism. Importantly, such Ag-MoS2 Janus NPs can be used as nanomotors, due to their asymmetric catalytic component structure, and self-propelled in H2O2 fuel solutions. They show good directional motion and significant dependence of their speed on fuel concentration. This study expands our understanding of the formation of heterogeneous Janus particles and provides a promising platform to investigate active colloids as nanomotors. [ABSTRACT FROM AUTHOR]

Here an alternative preparation route, pulsed laser ablation in liquid (LAL) of FeCl3 solution, is reported to facilely synthesize crystalline iron oxychloride (FeOCl) nanosheets at ambient conditions. Well-dispersed spherical gold (Au) nanoparticles (NPs) are simultaneously decorated on surface of the FeOCl nanosheets, which possess (010) preferred orientations with microsized dimensions in planar and tens of nanometers in thickness. The crystalline size and composition of the Au/FeOCl can be effectively modulated by simply changing FeCl3 concentrations. Technical observations illustrate that the nanocomposites possess good thermal stability and surface of which adsorbs abundant H2O molecularly and oxygen species chemically. The FeOCl nanosheets are formed through chemical side hydrolysis reaction in the localized liquid region with gradient temperature, which is derived from thermal transfer of LAL-induced plasma plume. The Au/FeOCl nanocomposites, as chemiresistors, show exceptionally high sensing response and perfect selectivity to HCl gas at room temperature. The excellent sensing behavior is ascribed to the Au-NP-enhanced surface chemisorption of oxygen species and selective adsorption of HCl for FeOCl nanosheets. The synthesized Au/FeOCl nanocomposites provide a new candidate for exclusive HCl detection. And the proposed LAL-assisted fabrication routes might open new perspectives for formation of other metal oxychloride compounds. [ABSTRACT FROM AUTHOR]