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Porous Fe 2 O 3 -loaded NiO nanosheets were obtained by the thermal decomposition nanosheets of iron element-loaded Ni(OH) 2 synthesized via microwave-assisted liquid-phase synthesis under atmospheric condition. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM) and Brunauer Emmett Teller (BET) N 2 adsorption–desorption analysis were used to characterize the as-prepared products. Gas sensing measurement indicated that the sensor based on the 1.5% Fe 2 O 3 -loaded NiO nanosheets exhibits untrafast response speed as well as short recovery time and high responses to ethanol and methanol (the response/recovery time of the gas sensor are 0.5/14.6 s and 0.1/11.4 s with the responses of 170.7 and 107.9–100 ppm ethanol and methanol, respectively). In addition, the 1.5% Fe 2 O 3 -loaded NiO nanosheets-based sensor can detect ethanol and methanol at a detection limit of well below 200 ppb (the responses are 6.88 and 6.82–200 ppb ethanol and methanol, respectively). The enhanced sensing behaviors can be attributed to the nanosheet-like structure and n-type Fe 2 O 3 /p-type NiO heterojunction. The time-saving method developed by us is easy to control to produce the nano-particulate composites without high experimental requirement and make it possible in commercial applications. Our work may explore a possibility to synthesize nanomaterial with ultrafast responding and fast recovering behaviors for real-time monitoring gas sensor. [ABSTRACT FROM AUTHOR]

Hollowed-out hierarchical Co 3 O 4 microrods has been synthesized via the interfacial-reaction of CoC 2 O 4 ·2H 2 O with NaOH. Field emission scanning electron microscopic and transmission electron microscopic results revealed that the Co 3 O 4 samples were hollowed-out hierarchical microrod-like structure assembled by interlaced thin nanosheets (with thickness of around 7 nm). The gas sensing properties of the porous microrods Co 3 O 4 were evaluated. The response/recovery time of the gas sensor to 100 ppm methanol and ethanol are 0.8/7.2 s and 0.8/10.8 s, respectively. Gas sensing measurement revealed that the hollowed-out hierarchical Co 3 O 4 microrods exhibit high performance, especially fast response/recovery characteristics to methanol and ethanol. The enhancement of gas sensing properties is attributed to the thin thickness of nanosheets, large specific surface area, loose interior and through-pore structure. The good sensing performance suggests this hollowed-out hierarchical Co 3 O 4 microrods could be a promising candidate as a sensing material for real-time monitoring gas sensor. [ABSTRACT FROM AUTHOR]

Binder-free CeO 2 coated/Pd-decorated Cu x O nanowires (Cu x O/Pd/CeO 2 _NWs) based on Cu foam were synthesized using a four-step process: electrochemical nanoengineering for preparing Cu nanowires, galvanic replacement between Cu nanowires and H 2 PdCl 4 , soaking in cerous nitrate solution and followed thermal annealing. Due to the optimized Pd thin layer, followed coating of the moisture-blocking CeO 2 overlayer, the binder-free Pd-decorated Cu x O nanowires exhibit a prominently enhanced sensing properties to H 2 S. The Cu x O/Pd/CeO 2 _NWs sensor exhibits a high response of 36.69 to 50 ppm H 2 S with rapid response/recovery speed (48.9 s/59.1 s), good selectivity and humidity-independent sensing properties at room temperature. Therefore, this work shows promising potential in detecting H 2 S and a new insight is opened up in designing binder-free devices based on metal substrate for indoor/outdoor environmental monitoring regardless of humidity fluctuations. • Binder-free CeO 2 coated/Pd-decorated Cu x O nanowires (Cu x O/Pd/CeO 2 _NWs) synthesized based on foam. • Cu x O/Pd/CeO 2 _NWs sensor with response of 36.69 and response/recovery times (48.9 s/59.1 s) to 50 ppm H 2 S at room temperature. • Good selectivity. • Excellent humidity-independent sensing properties due to the coating of CeO 2 overlayer. [ABSTRACT FROM AUTHOR]

A novel method was developed to design highly sensitive ethanol gas sensor based on the mechanism of ethanol quasi molecular imprinting. SnO 2 nanoparticles E and W were prepared by incorporating liquid ethanol which is the tested objective gas with deionized water thermal method and pure deionized water thermal method respectively. SnO 2 nanoparticle films WW and EW for ethanol gas sensor were obtained by mixing pure deionized water with the as-prepared powders W and E, and WE and EE were prepared by mixing liquid ethanol with W and E powders respectively. The ethanol gas sensing properties of these films were evaluated. Testing results reveal that the sensor S EE based on film EE which was fabricated by mixing liquid ethanol with E nanoparticles exhibits the most excellent sensing performance to ethanol gas and the response descended in the order of S WE , S EW and S WW . It proves that the introduced objective gas in the procedure of device fabrication plays a very important role for design a highly sensitive gas sensor. In addition, we consider that pore diameter of about 4.3 nm may be the critical size for the smooth adsorption and desorption of ethanol gas. [ABSTRACT FROM AUTHOR]

Metal-organic framework (MOF)-derived ZnCo 2 O 4 was synthesized by utilizing the template agent 2-methylimidazole, zinc and cobalt nitrate by an easy solvothermal process followed by annealing for the first time. The porous hierarchical ZnCo 2 O 4 microstructure possesses a microflower structure assembled by 3D nanosheets. The obtained flower-like structure has abundant open spaces between nanosheets, which allows for facile gas diffusion while providing plentiful active sites for gas adsorption. The hierarchical ZnCo 2 O 4 microflower-based sensor exhibits a high response of 32.32 and fast response/recovery rates (2.6/8.8 s) at 200 °C to 100 ppm acetone gas. In addition, the porous hierarchical ZnCo 2 O 4 microflower-based sensor has a detection limit below 50 ppb with a response of 2.51 to acetone gas. The excellent sensing performance of this porous hierarchical structure-based sensor is ascribed to the good gas accessibility of the microflower morphology with a high specific surface area, small particle size and highly porous structure. This work explores an efficient way to synthesize MOF-derived bimetallic oxides with microflower structures assembled by 3D nanosheets for gas sensing applications. [ABSTRACT FROM AUTHOR]

• Cu-supported Ag Nanowires (Cu@AgNAs 1-5) are prepared under green solution. • Ag loading of Cu@AgNAs 1-5 is above 81 mg cm−2. • Cu@AgNAs 1-5 -Zn battery demonstrates an areal capacity of 36.8 mAh cm−2 at 10 mA cm−2. As one of the most mature battery systems, the silver-zinc battery holds huge promise in the field of aqueous rechargeable batteries due to superior performance, high safety and environmental friendliness. It is urgent to improve the areal capacity of silver-zinc batteries so far. This study reports a novel Cu-supported Ag Nanowires (Cu@AgNAs 1-5: abbreviation of Cu@AgNAs 1 , Cu@AgNAs 2 , Cu@AgNAs 3 , Cu@AgNAs 4 and Cu@AgNAs 5) as binder-free cathodes for high performance rechargeable aqueous silver-zinc batteries. Cu@AgNAs 1-5 are successfully prepared by two steps of electrochemical nanoengineering and mild galvanic replacement between Cu and [Ag(NH 3) 2 ]+ chelate ions under green solution. With ultrahigh Ag loading of above 81 mg cm−2, the Cu@AgNAs 5 cathode achieves ultrahigh areal capacity of above 36 mAh cm−2 at current density of 10 mA cm−2. Benefiting from synergistic effect of Ag and Cu, multiply twinned structure accompanied by lattice defections (such as lattice distortion, mismatch and dislocation) and heterostructures, the Cu@AgNAs 1-5 cathodes achieve excellent Ag utilization and cycling stability. Furthermore, the aqueous rechargeable Cu@AgNAs 5 -Zn battery demonstrates an excellent areal capacity of 36.80 mAh cm−2 at 10 mA cm−2. This work offers a promising pathway to greatly enhance areal capacity of bimetallic nanostructure-based electrodes and the Cu@AgNAs 1-5 -Zn batteries are attractive for large-scale energy-storage application. [ABSTRACT FROM AUTHOR]

• Unique CdS quantum dots (˜4.5 nm) supported by ultrathin porous nanosheets assembled into hollowed-out Co 3 O 4 microspheres is successfully synthesized via a simple and energy-efficient room temperature in situ growth strategy. • This work explored an efficient method to fabricate room-temperature gas sensors with a high response and ultrafast response/recovery rates by integrating quantum dots with hollowed-out nanostructures, the resulting sensors overcame the temperature issues of gas sensors and realized reproducible room-temperature gas sensing capabilities. • The gas sensor based on CdS QDs/Co 3 O 4 HMSs exhibits a high response and ultra-fast response/recovery speed at room temperature when detecting H 2 S (the response and response/recovery times of the gas sensor to 100 ppm H 2 S at room temperature are 12.7 and 0.6/1.0 s, respectively). With the urgent need to improve societal security, semiconductor-based gas sensors have received substantial attention for their efficiency and accuracy in the detection of harmful gases. However, challenging existed to develop sensors that exhibit both high response and rapid response/recovery rates at room temperature. Herein, we present a simple and energy-efficient room-temperature in situ growth strategy to prepare CdS quantum dots supported by ultrathin porous nanosheets assembled into hollowed-out Co 3 O 4 microspheres (CdS QD/Co 3 O 4 HMSs). XRD, EDX, BET, SEM, TEM and HRTEM analysis confirmed that the interconnected CdS QDs (˜4.5 nm) were well dispersed on the ultrathin porous nanosheet of Co 3 O 4 HMSs. The fabricated CdS QD/Co 3 O 4 HMS sensor exhibited high response (12.7) and ultra-fast response/recovery rates (0.6/1.0 s) to 100 ppm H 2 S at 25 °C, which is ascribed to high active quantum dots and hollowed-out nanostructure. In addition, the sensor exhibited a low detection limit (1–5 ppm), good reversibility and exceptional long-term stability. This work explores an efficient way to fabricate high-response and ultra-fast response/recovery room-temperature gas sensors by integrating quantum dots with hollowed-out nanostructures. [ABSTRACT FROM AUTHOR]

Highlights • Hierarchical hollow ZnO nanocages with quantum dots were prepared based on metal–organic framework (MOF) strategy. • The gas sensor based on hierarchical hollow ZnO nanocubes exhibits relatively high response of 139.41 with response/recovery time of 2.8/56.4 s to 100 ppm ethanol gas at 325 °C. • The HHQD-ZnO nanocages-based sensor can detection limit of well below 25 ppb with the response of 5.1. Abstract As an important semiconductor metal oxide, zinc oxide has been intensely investigated for the application of gas-sensing. Herein, we developed a metal–organic framework (MOF)-based strategy to synthesize novel hierarchical hollow ZnO nanocages with quantum dots (denoted as HHQD-ZnO nanocages). For comparison, solid ZnO and hollow ZnO nanocages derived from the rhombic dodecahedral (RD) ZIF-8 and 470-ZIF-8, respectively have also been synthesized. Gas sensing measurement indicated that the sensor based on the HHQD-ZnO nanocages exhibits super high response of 139.41 upon 100 ppm ethanol at 325 °C. In addition, the HHQD-ZnO nanocages-based sensor can detect ethanol gas at a detection limit of well below 25 ppb with the response of 5.1. Such excellent performance, especially the ultrahigh response to ethanol is explained with respect to particle-interpenetrating framework with good connectivity, hierarchical porous hollow nanostructure and quantum dots. [ABSTRACT FROM AUTHOR]

Development of high-performance p-type semiconductor gas sensors especially the fast response/recovery speed and high response based on inexpensive non-noble metal oxides without doping or noble metal decoration for the practical applications of gas sensor are highly desirable. In this work, the rapid room-temperature synthesis of innovative and unique parallel copper oxide nanowires assembled microspheres (CuO NMs) with excellent gas sensing property is reported. The morphological characteristics, surface area, porosity, chemical composition and the chemical conversion process are studied carefully. As a result, the CuO NMs exhibit a relatively high gas response, especially the fast response and recovery time to 100 ppm n-propanol vapor at relatively low operating temperature of 190 °C, respectively. This new rapid self-template derived functional nanomaterials will offer a promising platform for highly sensitive and real-time monitoring p-type gas sensors. [ABSTRACT FROM AUTHOR]

In this work, the hollow and hollowed-out Co 3 O 4 microspheres (Co 3 O 4 -HHMSs) assembled by porous ultrathin nanosheets with thickness of about 3 nm were synthesized via a new rapid and energy-efficient room temperature interfacial-reaction. The structure and morphology of the as-prepared products were characterized by various methods As expected, the gas sensor based on Co 3 O 4 -HHMSs exhibits high response and ultra-fast response/recovery speed when detecting ethanol. Especially, in our knowledge, both of the response and recovery time in 1 s at the same time for one metal-oxide (MOX) semiconductor film gas sensor was the first time reported up to now. The formation mechanism of Co 3 O 4 -HHMSs and the gas sensing mechanism of high response and the ultra-fast response/recovery speed of the sensor are discussed in detail. Notably, the hollow and hollowed-out nanostructure assembled by porous ultrathin nanosheets with thickness of about 3 nm is mainly responsible for the high response and ultra-fast response/recovery speed of the sensor. [ABSTRACT FROM AUTHOR]

Flexible room-temperature (RT) gas sensors are highly desirable due to their low power consumption and wearability. However, it is very challenging to integrate excellent mechanical flexibility and superior gas sensing properties. Here, polyacrylonitrile (PAN) nanofiber/cobalt-doping SnS 2 nanosheets with nature-inspired "branch-leaf" structure was well tailored by directly grown Co-SnS 2 ultrathin nanosheets on PAN nanofiber for the first time. With the interfacial bonding interaction between PAN substrate and SnS 2 nanosheets, the geometrical deformability of composite structure, the interfacial bonding force, stress distribution, transfer and dissipation will be enhanced. Moreover, the electronic structure and S vacancy are regulated by Co-doping, then improve the gas transmission/diffusion, gas sensitive reactivity and carrier transfer/transport properties. The integrated RT NO 2 gas sensor exhibits excellent flexibility (minimum radius of curvature is 3.9 µm), high response, fast response/recovery speed (6.2 and 27.5/60 s). Meanwhile, it possesses a low detection limit and long-term stability. This comprehensive strategy for the integration of mechanical and gas sensitive properties unlocks the inherent bottlenecks of conventional film-based gas sensors and open a new design avenue for the development of flexible electronics. • Nature inspired polyacrylonitrile nanofiber/Co doping SnS 2 nanosheets was tailored. • The interfacial bonding interaction and geometrical deformability are strengthened. • The electronic structure and S vacancy of SnS 2 are regulated by Co-doping. • This strategy integrates mechanical flexibility and gas sensing properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-supported Ag Nanowires (Cu/Ag_NWs) with areal capacity of 1.42 mAh cm−2. • CuO/Ag 2 O nanosheets (CuO/Ag 2 O_NSs) obtained from spent Cu/Ag_NWs electrode. • CuO/Ag 2 O_NSs based sensor with response of 27.69 and response/recovery speed (0.9/5.2 s) upon 100 ppm benzyl alcohol gas at 300 °. With the development of energy saving and new energy technology, the growing need of rechargeable batteries presents a serious waste-recycling challenge. The recycling issues should be focused on to prevent environmental pollution and huge waste of resources. In this work Cu-supported Ag nanowires (Cu/Ag_NWs) as binder-free electrode are developed for rechargeable aqueous silver-zinc batteries. With the Ag loading of 3.54 mg cm−2, the Cu/Ag_NWs electrode achieves areal capacity of 1.42 mAh cm−2 at a high current density of 10 mA cm−2. After more than 18,000 times galvanostatic charge–discharge (GCD) test, the spent electrode of Cu/Ag_NWs with 20% original capacity transformed into nanosheet structure. Followed facile ultrasonic, cleaning and annealing treatment for the spent Cu/Ag_NWs electrode, the collected CuO/Ag 2 O nanosheets (CuO/Ag 2 O_NSs) are used for gas sensors. The sensor based on the CuO/Ag 2 O_NSs exhibits high response of 27.69 and fast response/recovery speed (0.9/5.2 s) upon 100 ppm benzyl alcohol gas at 300 °C. This work explores an efficient way in turning waste into treasure for the rechargeable battery in gas sensing application. [ABSTRACT FROM AUTHOR]