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The morphological and structural design provides an efficient protocol to optimize the performance of gas sensing materials. In this work, a gas sensor with high sensitivity for triethylamine (TEA) detection is developed based on p-type NiCo2O4 hierarchical microspheres. The NiCo2O4 microspheres, synthesized by a hydrothermal route, have a three-dimensional (3D) urchin-like structure assembled by nanorod building blocks. The structure-property correlation has been investigated by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscope, scanning electron microscope, N2 adsorption-desorption tests and comprehensive gas sensing experiments. The influence of calcination temperature on the morphological structure and sensing performances has been investigated. Results reveal that the material annealed at 300 °C has a very large specific surface area of 125.27 m2/g, thereby demonstrating the best TEA sensing properties including high response and low limit of detection (145 ppb), good selectivity and stability. The further increase of the calcination temperature leads to the collapse of the 3D hierarchical structure with significantly decreased surface area, which is found to decline the sensing performances. This work indicates the promise of ternary p-type metal oxide nanostructures for application in highly sensitive gas sensors.

Detection of volatile organic compounds (VOCs) at room temperature (RT) currently remains a challenge for metal oxide semiconductor (MOS) gas sensors. Herein, for the first time, we report on the utilization of porous SnO2 thin films for RT detection of VOCs by defect engineering of oxygen vacancies. The oxygen vacancies in the three-dimensional-ordered SnO2 thin films, prepared by a colloidal template method, can be readily manipulated by thermal annealing at different temperatures. It is found that oxygen vacancies play an important role in the RT sensing performances, which successfully enables the sensor to respond to triethylamine (TEA) with an ultrahigh response, for example, 150.5-10 ppm TEA in a highly selective manner. In addition, the sensor based on oxygen vacancy-rich SnO2 thin films delivers a fast response and recovery speed (53 and 120 s), which can be further shortened to 10 and 36 s by elevating the working temperature to 120 °C. Notably, a low detection limit of 110 ppb has been obtained at RT. The overall performances surpass most previous reports on TEA detection at RT. The outstanding sensing properties can be attributed to the porous structure with abundant oxygen vacancies, which can improve the adsorption of molecules. The oxygen vacancy engineering strategy and the on-chip fabrication of porous MOS thin film sensing layers deliver great potential for creating high-performance RT sensors.

Design of metal/semiconductor hybrid nanostructures provides an important strategy for developing efficient chemical gas sensors. Herein, a highly sensitive gas sensing material for detection of triethylamine is designed by loading Au nanoparticles on porous In2O3 microspheres. The In2O3 microspheres are prepared by thermally annealing the precursor of 3D nanosheets assembled In2S3 microspheres. Then, Au nanoparticles are functionalized onto In2O3 to obtain a novel Au/In2O3 hybrid microspheres. The morphological structure and chemical composition of the prepared materials were studied in detail by different techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The gas sensing properties of the Au/In2O3 microspheres have been systematically investigated. Results reveal that the amount of Au has a large influence on the sensor performances. The Au/In2O3 sensor with Au content of 0.53 at.% exhibits the best response to triethylamine at 280 °C. An extremely high response of 648.2 is registered on exposure to 100 ppm triethylamine. The sensor also possess fast response-recovery and very stability, as well as a low detection limit of 108 ppb. The sensing mechanism behind the enhanced sensor performances are also discussed.

Heterostructures of metal oxide semiconductors present great potential for chemical sensor devices due to the fascinating properties endowed by the multiple materials and the heterointerface. In the present work, W18O49/α-Fe2O3 hollow heterostructures with different α-Fe2O3 contents are prepared by a hydrothermal method. The chemical composition and structure properties are characterized by multiple techniques. The gas sensing study demonstrates that the W18O49/α-Fe2O3 hollow heterostructures exhibit superior sensing performances toward acetone against pure W18O49. The composite containing 6.3 wt% α-Fe2O3 delivers the best sensor response and fast response–recovery speed (10 and 31 s), good selectivity, and low limit of detection (86 ppb). The superior gas sensing performance is interpreted by the functions of porous hollow structure and heterojunctions when introducing α-Fe2O3. This work provides a novel structure design for synthesis of high performances gas sensing materials for ppb-level acetone detection.

The rational design of heterostructures is highly important for innovative sensor technology to acquire efficient gas detection with optimized gas sensing properties. In the present work, a novel heterostructure of Au/Co3O4/W18O49 hollow spheres is constructed and applied for gas sensor application. The structure-property correlation has been studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, Scanning electron microscope and Transmission electron microscope, as well as comprehensive gas sensing tests. Experiments demonstrate that the Au/Co3O4/W18O49 heterostructure delivers outstanding performances in terms of high sensitivity, fast response-recovery, good selectivity, and very low limit of detection against pristine W18O49 and Co3O4/W18O49. Notably, a very high response (16.7) to 2 ppm triethylamine and a state-of-the-art limit of detection (81 ppb) are obtained. The superior gas sensing properties are attributed to a synergistic combination of the unique porous structure, the p-n heterojunctions between Co3O4/W18O49, and the catalytic spillover effect of Au nanoparticles.

Metal sulfides are interesting materials for utilization as anodes in Li-ion Batteries (LIBs). However, the poor conductivity and huge volume change during the discharge/charge cycles severely limit their potential application. In the present work, a sheet-on-fiber structure of In2S3@N-doped carbon (In2S3@N-Carbon) is designed through a hydrothermal method, and the materials were characterized by methods of scanning electron microscopy, X-ray diffraction and transmission electron microscopy. When applied to LIBs, In2S3@N-Carbon shows better electrochemical performances in comparison to pristine In2S3. In2S3@N-Carbon retains a reversible capacity of 485 mA h g−1 after 200 cycles at 0.1 A g−1, which is significantly higher than that (34.6 mA h g−1) of pure In2S3. The enhanced electrochemical properties of In2S3@N-Carbon nanocomposite are attributed to the N-doped carbon fibers, which enhances the conductivity and relaxes the volume expansion of electrodes. This study provides a rational design of nanostructure for high-performance anode materials.

Transition metal dichalcogenides (TMDs, typically MoS2) have shown great promise as anodes for high-performance lithium-ion batteries (LIBs) due to the layered structure. However, the low electric and ionic conductivities and the large volume expansion of MoS2 during lithiation inevitably result in a fast capacity decrease and limited cycling life. In this work, a unique sheet-on-tube micro/nanostructure was designed and realized to tackle the above mentioned drawbacks. In detail, MoS2 nanosheets are perpendicularly anchored on the N-doped carbon microtubes (NCMs) by a facile approach. NCMs was selected as the support to prevent aggregation of MoS2 nanosheets, and serve as the pathway for electron conduction, as well as a media to alleviate the volume change of MoS2 during lithiation/delithiation. Due to the advantageous structure, the MoS2@NCMs show significantly enhanced lithium storage properties in comparison to pure MoS2. The design strategy and mechanism demonstrated in this work is potentially useful for developing high-capacity electrode materials for LIBs.

Metal oxide semiconductor (MOS) nanomembranes hold a great potential for electronic devices. In this work, tubular SnO2 nanomembranes were fabricated by the rolled-up technology and investigated as the sensing element for chemiresistive gas sensors. Due to the high accessibility to both surfaces of nanomembranes and the large amount of adsorbed oxygen species, the sensor based on SnO2 nanomembranes displayed high and fast response for selective detection of acetone, as well as good repeatability, stability and low detection limit of ppb-level. The very good sensing performances derived from the tubular nanomembrane structure suggests a new platform that can be used for chemical gas sensors. This work will drive the integration of tubular MOS nanomembranes into a real microsensor based on the lab-in-tube concept.

Graphene/metal oxide (MO) nanocomposites hold great promise for application as anodes in lithium-ion batteries (LIBs). However, the restacking of graphene during subsequent processing remains a challenge to overcome for enhanced lithium storage properties. Herein, the fabrication of sandwich-architecture carbon-riveted graphene/SnO2 nanorods, in which the SnO2 nanorods are confined in the nanospaces formed by the carbon layers on graphene, by a two-step hydrothermal process followed by thermal treatment, is reported. Electrochemical tests show that the carbon-riveted nanolayers significantly improve the lithium storage performance of graphene/SnO2 . The nanocomposite displays a high reversible capacity of 815 mAh g-1 after 150 cycles at 100 mA g-1 and high cycling stability at 1000 mA g-1 . This work provides an efficient way to manipulate graphene/MO-based nanocomposites for LIBs with improved performance.

Nanocomposite of graphene/α-Fe 2 O 3 (G/α-Fe 2 O 3 ) nanospindles was synthesized by a simple hydrothermal assembly method followed by thermal treatment. The α-Fe 2 O 3 nanospindles were evenly enwrapped by the graphene nanosheets. When evaluated as an anode for Li-ion batteries (LIBs), the G/α-Fe 2 O 3 nanocomposite showed enhanced cycling performance and rate capability compared to pure α-Fe 2 O 3 . G/α-Fe 2 O 3 retained a reversible capacity of 607 mAh g −1 after 100 cycles at 100 mA g −1- , which is far higher than that (160 mAh g −1 ) of α-Fe 2 O 3 . The superior electrochemical performance of G/α-Fe 2 O 3 can be attributed to the protection effect of graphene nanosheets to accommodate the volume change of α-Fe 2 O 3 during lithiation/delithiation.

Metal oxide semiconductors (MOS) are important candidates as the sensing layer for chemical gas sensors to detect volatile organic compounds (VOCs). However, the low surface activity limits the use of MOS in future high performance gas sensors. The design of susceptive nanostructures with prominent surface modification can be an effective strategy to achieve high sensitivity and high selectivity. Herein, Pt nanoparticles with a fine size of below 1 nm serving as the sensitizers are functionalized on porous W18O49 nanospheres via atomic layer deposition and investigated for acetone detection. The W18O49/Pt spheres combine the advantages of fast gas diffusion enabled by the porous shells and catalytic properties of Pt nanocatalysts. Gas sensing tests reveal that W18O49/Pt has a very high response to 20 ppm acetone (Ra/Rg = 85), which is ∼40 times higher than that of pure W18O49 (Ra/Rg = 2.1) at a low operating temperature of 180 °C. Meanwhile, W18O49/Pt shows fast response-recovery speed and good stability as well as excellent selectivity to acetone against other interfering gases. In addition, an ultrahigh sensitivity of 1.01 ppm−1 and a very low limit of detection of 52 ppb is obtained. The superior gas sensing performances of the W18O49/Pt materials indicates a strong potential for detection of biomarkers for exhaled breath diagnosis, and also paves the way to manipulate other metal oxide semiconductor-based sensors with high performances.

Efficient electronic sensors for detection of volatile organic compounds are increasingly in great demand due to its indispensable utilization in healthcare and environment monitoring systems. Assembly of complex nanostructures from diverse host and guest materials proves to be an effective way to create new sensing materials with improved performances. Yet it still remains a challenge to manipulate efficient heterostructures for acetone detection to acquire high sensitivity and selectivity. Herein, a high performance nanosensor is realized based on p-type Co3O4 sensitized n-type SnO2 porous nanospheres. The rich grain boundaries between adjacent SnO2 nanoparticles serve as the active sites for molecules adsorption and electron transportation. The p-n heterointerface formed between Co3O4 and SnO2 allows for the fast sensing reactions on materials surface. Consequently, the sensor device delivers outstanding properties in terms of fast response-recovery, low detection limit (103 ppb), high sensitivity and excellent selectivity toward acetone detection. The strategy presented here is generally applicable and can provide some hints to design efficient electronic sensors with an optimized selectivity.

Sensitization of metal oxide semiconductors is crucial for developing high performance electronic gas sensors. Herein, a unique dual sensitization protocol is proposed to boost the sensing performances of metal oxide nanowires. As a proof-of-concept, W18O49 nanowires are selected as the host materials, and Ag, Pt nanoparticles are loaded on W18O49 by an in-situ redox reaction to fabricate the novel Ag/Pt/W18O49 hybrid nanowires. Gas sensing tests demonstrate the superiority of the ternary nanowires in detecting triethylamine vapor against the binary Ag/W18O49 and Pt/W18O49 nanowires. The sensor based on Ag/Pt/W18O49 nanowires manifests fast response and recovery features and very high response over a wide concentration of 0.1–50 ppm, as well as good selectivity and stability. An ultrahigh sensitivity of 1.13 ppm−1 is registered by the Ag/Pt/W18O49 nanowires and a low detection limit of 71 ppb is obtained. The excellent performances are attributed to the dual sensitization mechanism, i.e., a synergy of both electronic and chemical interactions derived from the Ag and Pt functionalization. This work establishes a new strategy for constructing multi-metal functionalized nanowires and their utilization in functional nanodevices with enhanced performances.