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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]

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]

Molecular-level understandings of gas sensing mechanisms of oxide-based chemiresistors are significant for designing high-performance gas sensors; however, the mechanisms are still controversial due to the lack of direct experimental evidence. This work demonstrates efficient in situ surface-enhanced Raman spectroscopy (SERS) tracing of the highly representative SnO 2 -ethanol gas sensing using Au@SnO 2 nanoparticles (NPs), where the Au core and SnO 2 shell provide SERS activity and a gas sensing response, respectively. The in situ SERS evidence suggests that the sensing follows a Mars-van Krevelen mechanism rather than the prevailing adsorbed oxygen (AO) model. This mechanism is also observed in sensing other gases based on the Au@SnO 2 NPs, showing its universality. This work offers efficient in situ tracing for gas sensing and experimental elucidation of the specific gas sensing mechanism, potentially ending the long-term controversy over the gas sensing mechanisms. Therefore, it is highly significant to this field.

A flexible route is developed for fabrication of large area α-Cu 2 S nanorod arrays (NRAs) on the basis of one-step laser ablation of a copper foil in CS 2 liquid. It has been demonstrated that the obtained products are the high-temperature phase α-Cu 2 S and consist of the nanorods vertically standing on the Cu foil, exhibiting the array. The nanorods were about 1 μm in length and around 100 nm in thickness and built by stacking the nearly spherical and ⟨110⟩-oriented nanoparticles (NPs) up. Such array can be peeled off from the foil and remain freestanding. Further, it has been found that the ablation duration, the laser power, and the foil surface state are crucial to the formation of the Cu 2 S NRA. The formation of such oriented NP-stacked Cu 2 S NRAs is attributed to the laser-induced generation of α-Cu 2 S NPs and the NPs' deposition/oriented connection growth on the surface-vulcanized copper foil. Importantly, the visible photocurrent response of the α-Cu 2 S NRAs is 8 times higher than that of the Cu 2 S NPs' film with the equivalent thickness and also larger than that of previously reported Cu 2 S, showing significantly enhanced photoelectric performances. As an application, such NRAs have exhibited markedly enhanced visible photocatalytic activity and highly stable recycling performances, compared with the α-Cu 2 S NPs. Further studies have revealed that the enhanced performances are attributed to the structurally enhanced light trapping effect of the NRAs as well as short and smooth carrier diffusion path in the oriented NP-stacked nanorods. This work provides a new and simple method for fabrication of the large area Cu 2 S NRAs with high and stable photoelectric performances.

A very simple route is developed for fast fabrication of nanosized amorphous titanium dioxide (TiO 2 ) hollow spheres (THPs) just via dropping the pure four titanium chloride (TiCl 4 ) liquid droplets into deionized water at around room temperature. The THPs, at around 80 nm in mean diameter, can be formed within a few seconds after dropping TiCl 4 droplets into water. The shell layers of the obtained THPs are amorphous and porous in structure with a porosity of 58-80% and show a linear increase in thickness with the size of THPs. Further experiments have revealed that the reaction temperature, initial pH value, and size of the TiCl 4 droplet are crucial to the formation, size, productivity, and microstructure of the THPs. A model is proposed on the basis of the fragmentation of liquid droplets, hydrolysis-induced formation, and inward growth of TiO 2 shell layers, which can well describe the formation of the THPs. Importantly, such amorphous nanoscaled THPs have exhibited some strong hollow structure-enhanced performances. Typically, the THP-built film shows the highest reflectivity in the visible region compared to the other structured TiO 2 films. Especially, if it supports the film of the Au nanoparticle, the surface-enhanced Raman scattering effect is significantly enhanced by more than 1 order of magnitude. This work provides not only a simple and quick fabrication method for the THPs but also a new member for their family.