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In this study, a novel high length-diameter ratio NiO nanorods decorated with uniformly ZnO nanoparticles was synthesized via a facile one-step hydrothermal process. • A novel NiO nanorods decorated with uniformly ZnO nanoparticles was synthesized. • The NiO/ZnO composites based sensor show excellent ethanol gas response. • The p-n heterojunction and astonishing synergistic played an essential role in tgas-sensing performance. In this study, a novel high length-diameter ratio NiO nanorods decorated with uniform ZnO nanoparticles was synthesized via a facile one-step hydrothermal process. It was a surprise to find that the NiO/ZnO nanorods heterostructure based sensor demonstrated much more excellent ethanol gas sensing properties than that of undoped NiO nanorods. This enhancement of sensing properties may be attributed to their synergetic effect as well as the heterojunction at interface between the NiO nanorods and ZnO nanoparticles. [ABSTRACT FROM AUTHOR]

Novel loosely and tightly arranged nanosheet-assembled flower-like WO 3 nanostructures were controllably synthesized under hydrothermal conditions. Through gas-sensing experiments towards NH 3 , it was found that the loosely-arranged WO 3 nanostructures exhibited a higher NH 3 response. This difference was due to the sparse cross-arrangement of the nanosheets on the surface of the sample and the larger specific surface area of the loosely-arranged structure. • Novel loosely and tightly arranged nanosheet-assembled flower-like WO 3 were synthesized. • The loosely-arranged WO 3 nanostructures exhibited the superior NH 3 sensing performance. • The factors affecting NH 3 -sensing properties are discussed in detail. Novel loosely and tightly arranged nanosheet-assembled flower-like WO 3 nanostructures were controllably synthesized via a facile hydrothermal approach. Additionally, NH 3 -sensing measurements were performed based on both samples. Remarkably, the loosely-arranged WO 3 nanostructures, which possess an abundance of semi-closed spaces and a larger specific surface area, exhibited improved NH 3 -sensing properties compared to that of the tightly-arranged WO 3 nanostructures. This discovery can provide guidance for improving the gas-sensing properties of nanosheet-assembled hierarchical MO x flower-like nanostructures. [ABSTRACT FROM AUTHOR]

Abstract An intricate sea-urchin-like hexagonal WO 3 nanostructure was synthesized by a facile hydrothermal approach. Sensing properties of the as-fabricated sensor exhibited surpassing response and selectivity for NO 2 in comparison of H 2 after corroborating the composition, phase-purity and surface morphology using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Formation of the urchin-like structure was ascribed to the capping effects of potassium sulfate that prompts the anisotropic growth of WO 3 , leading to hierarchical complex with a large surface-volume ratio. In particular, first-principle calculation had provided a new perspective for us to delve into the sensing process of H 2 and NO 2 from an atomic level. It was found that the sensing properties mainly arose from the tuning of electronic structure and electrons transfer between the adsorbed gas and the sensitized surface along with the charge relocation between them. Finally, a plausible mechanism was proposed as theoretical guidance for achieving high-performance sensors experimentally and supposedly. [ABSTRACT FROM AUTHOR]

Abstract In this work, hollow MoO 3 microcages were triumphantly synthesized using a facile hydrothermal method without any template, and a possible growth mechanism of this microstructure arising from the co-effect of inside-out Ostward-ripening mechanism and the acidic etching was speculated. Subsequently, gas sensor based on such MoO 3 with hollow characteristic was fabricated to investigate the gas-sensing properties for ethanol as compared to solid MoO 3 polyhedrons. It was found that the hollow cages exhibited lager ethanol gas response than that of solid polyhedrons. The enhanced sensing behavior may originate from its unique hollow structures, leading to sufficient sensing reaction on the surface as well as abundant gas diffusion. Graphical abstract The hollow MoO 3 microcages were successfully synthesized via a simple hydrothermal method without any template. Such hollow structure based sensor presented enhanced gas response to ethanol than that of solid MoO 3 polyhedrons based sensor. The hollow nature led to sufficient sensing reaction on the surface as well as abundant gas diffusion. Image 1 Highlights • Hollow MoO 3 microcages were successfully synthesized. • The gas sensor based on the MoO 3 presented enhanced gas response to ethanol. • The hollow structure of the MoO 3 cages enhanced surface sensing reaction. [ABSTRACT FROM AUTHOR]

Hierarchical 3D flower-like MoS 2 nanospheres with the diameter of about 300 nm were successfully synthesized via a facile hydrothermal process assisted with CTAB. And we found that CTAB played a vital role on the formation of MoS 2 architectures. As the concentration of CTAB increasing, MoS 2 nanopowders with sheet-like, flower-like, large size spherical morphologies were synthesized. And particle sizes of synthesized powders also increased. The optimum concentration of CTAB for the well-defined 3D hierarchical spherical morphology of MoS 2 was 6 g/L. In addition, a feasible formation mechanism of the morphology evolution was put forward in detail on the basis of the experimental results. The gas–sensing properties of flower-like MoS 2 nanospheres were tested. The result indicated that the sensor exhibited high response and selectivity towards NO 2, which may be related to the open and well-defined structures and the abundant micro reaction rooms assembled by ultrathin nanosheets. [ABSTRACT FROM AUTHOR]

3D hierarchical porous MoS 2 microspheres assembled by nanosheets were successfully fabricated via a facile yet efficient hydrothermal process using an assistance of CTAB as soft template which had significant effects on the final morphology of MoS 2 products. The possible formation mechanism of the harvested porous MoS 2 microspheres were preliminarily presented on the basis of the experimental results. Moreover, the gas sensing properties of the samples were investigated. The hierarchical porous MoS 2 microspheres are found to exhibit an excellent gas response capability, good response-recovery properties, reproducibility and selectivity, which provides further evidence that assistance CTAB is critical for governing the morphology and properties of the MoS 2 . [ABSTRACT FROM AUTHOR]

This work presented highly sensitive coral rock-like ZnO to investigate the sensing performances for volatile organic compounds (VOCs), including formaldehyde, methylbenzene, methanol and acetone. The coral rock-like ZnO with porous structure was synthesized using a solvothermal process and subsequent calcination. The gas response of the sensor based on the coral rock-like ZnO was reported for the four types of VOC vapors at different operating temperatures and gas concentrations. It was found that the fabricated sensor was sensitive to the four gases, revealing large gas response as well as fast response and recovery speed, which was ascribed to its distinctive porous nanostructure, resulting in adequate surface sensing reaction and effective gas diffusion. [ABSTRACT FROM AUTHOR]

In this work, hierarchical WO 3 ·H 2 O porous microspheres and conventional smooth WO 3 ·H 2 O microspheres were successfully fabricated via a simple hydrothermal process. The products were characterized by X-ray diffraction and scanning electron microscope. Meanwhile, the possible evolution processes of the two products were discussed based on time-dependent experiments. Remarkably, hierarchical porous spherical architectures which possess abundant micro reaction rooms, exhibited improved gas-sensing performance compared to smooth sphere-like structures. It is believed that this unique nanostructure has great potential to enhance the gas-sensing properties of tungsten oxides and other semiconductor materials. [ABSTRACT FROM AUTHOR]

A facile hydrothermal route was developed for the preparation of well-aligned hierarchical flower-like NiO nanostructure with the assistance of SDS that served as a structure-directing agent as well as a capping agent in the process of aggregation and assembly. Notably, the NiO sensors exhibit enhanced gas-sensing performance towards ethanol, which could be explained in association with the ultrathin nanosheets that are close to Debye length (L D ) scale and thus get the majority carriers fully depleted due to the ionization of adsorbed oxygen, abundant effective gas diffusion paths as well as high surface-to-volume ratio to promote sufficient contact and reaction between the NiO sample and ethanol molecules, and numerous miniature reaction rooms assembled with nanosheets to make the test gas molecules stay long enough for completed gas-sensing reactions. Besides, a novel growth mechanism with the passage of reaction time was also proposed in detail. [ABSTRACT FROM AUTHOR]

A novel WO 3 ·H 2 O nanostructure assembled by numerous one-dimensional nanorods as building units were synthesized successfully through a facile hydrothermal process. As a comparison, we also prepared the monodispersed WO 3 ·H 2 O nanorods. The crystal structures and morphologies of two products were characterized by X-ray diffraction and scanning electron microscope. Furthermore, gas sensing experiments indicated that a superior gas-sensing property of aligned WO 3 ·H 2 O nanorods occurs over that of the monodispersed WO 3 ·H 2 O nanorods, which is likely attributed to large effective surface areas and abundant accessible diffusion channels provided by this special structure for sufficient gas reactions. [ABSTRACT FROM AUTHOR]

Herein, a novel hierarchical cactus-like WO 3 -SnO 2 nanocomposite was synthesized by a one-step hydrothermal route. It was a surprise to find that such nanostructure consisting of diminutive SnO 2 nanospheres decorated bulky WO 3 nanosphere exhibited a high gas response and fast response-recovery speed towards acetone, mainly attributed to their synergetic effect as well as the heterojunction at the interface between the bulky WO 3 nanosphere and diminutive SnO 2 nanosphere, resulting in adequate surface adsorption and efficient electron transport. [ABSTRACT FROM AUTHOR]

In this study, the hollow MoO 3 microcages were successfully synthesized using a one-step hydrothermal route, and their gas-sensing properties towards ethanol were further investigated. It was found that such MoO 3 microcages possessed excellent ethanol gas response, which benefited from their unique hollow structure with a less stacking aggregation, offering sufficient pathways for gas diffusion as well as abundant adsorption sites for surface chemical reaction. [ABSTRACT FROM AUTHOR]

ZnO nanorods and nanosheets were synthesized via a facile hydrothermal route, and their gas sensing properties were tested to figure out the effect of surface morphologies on gas sensing performance. It was surprisely found that the ZnO nanorods exhibit quicker response and recovery speed towards ethanol, which may be ascribed to the better conductivity and lower potential barrier, whereas the nanosheets display larger ethanol gas response owing to its higher specific surface area. [ABSTRACT FROM AUTHOR]

We report on the synthesis of pristine and Cu-doped SnO 2 spheres using a facile hydrothermal method and investigate their microstructures and gas-sensing response. We focus on how Cu doping can have an impact on gas-sensing behavior of SnO 2 -based sensors toward H 2 S. We find that Cu doping can enhance significantly the gas response of SnO 2 toward H 2 S, the origin of which can be clarified with a proposed adsorption model. First-principles calculations reveal that adsorption energy of H 2 S on Cu-doped surface is lower than that on undoped one and the interaction between adsorbed H 2 S and Cu-doped surface is stronger than that between adsorbed H 2 S and pure surface, which consequently improves gas-sensing performances of SnO 2 toward H 2 S. Such a combined experimental and calculational study offers an explanation on how Cu doping affects gas-sensing performances of SnO 2 . [ABSTRACT FROM AUTHOR]

Sparsely and closely flower-like WO 3 ·H 2 O hierarchical architectures were successfully synthesized via a one-step hydrothermal process. The obtained samples are both WO 3 ·H 2 O nanoflowers assembled by ultrathin nanosheets with the thickness less than electron deletion layer. And the possible formation processed was proposed based on the comparative studies. Furthermore, gas sensing experiments demonstrated that the closely WO 3 ·H 2 O nanoflowers which possess numerous semi-closed spaces have a superior gas-sensing performance compared with the sparsely one. We believe this unique structure will critically enhance the gas sensing properties of WO 3 ·H 2 O nanomaterials. [ABSTRACT FROM AUTHOR]

Nanomaterials with hierarchical architectures consisting of two-dimensional nanostructures have attracted considerable attention for their potential applications in recent years. In current work, flake-flower NiO architectures self-assembled by aggregative nanosheets have been successfully synthesized via the hydrothermal route. It is notable that the NiO sensors exhibit excellent gas sensing performances owing to the open and well-defined structure as well as abundant micro reaction rooms built by two-dimensional ultrathin nanosheets, which are thinner than the thickness of electron depletion layer. Moreover, a possible growth mechanism for the interactions between PVP and Ni 2+ ions in the synthesis of the precursors Ni(OH) 2 and the novel morphology evolution of the NiO nanoflowers are proposed in detail. [ABSTRACT FROM AUTHOR]

In this paper, WO 3 ·H 2 O with different nanostructures from 0D to 3D were successfully synthesized via a simple yet cost-effective hydrothermal method with the assistance of surfactants. The structures and morphologies of products were investigated by XRD and SEM. Besides, we systematically explained the evolution process and formation mechanisms of different WO 3 ·H 2 O morphologies. It is noted that both the kinds and amounts of surfactants strongly affect the formation of WO 3 ·H 2 O crystals, as reflected in the tailoring of WO 3 ·H 2 O morphologies. Furthermore, the gas sensing performance of the as-prepared samples towards methanol was also investigated. 3D flower-like hierarchical architecture displayed outstanding response to target gas among the four samples. We hoped our results could be of great benefit to further investigations of synthesizing different dimensional WO 3 ·H 2 O nanostructures and their gas sensing applications. [ABSTRACT FROM AUTHOR]

We report the synthesis of novel nest-like MoO 3 hierarchical structures with nanobelts as building blocks via a facile hydrothermal process. A comparison study reveals that an enhanced gas sensing performance for the sensor made of nanobelt-assembled nest-like MoO 3 towards ethanol occurs over that of the monodispersed MoO 3 nanobelts. The improved gas sensing properties are mainly attributed to the well-aligned nanoporous structures with a less stacking configuration, which provides sufficient nano or micro reaction rooms for chemical reaction as well as effective diffusion channels for gases. [ABSTRACT FROM AUTHOR]

Self-assembly of one-dimensional nanoscale building blocks into functional three-dimensional super-structures has attracted vast interests. In current work, novel NiO flower-like architectures have been successfully synthesized via a facile hydrothermal method and subsequent calcination. Notably, it has been observed that the sodium oxalate plays a vital role on the aggregation of needles and a novel growth mechanism of needle-flower NiO has been proposed in detail based on the experimental results. More importantly, it is noted that the gas sensing properties of the flower-like architectures are superior to needle-like structures on the basis of the investigation. Such a synthetic way may open up an avenue to tailor the morphologies of some other metal oxides and enhance their gas sensing performance. [ABSTRACT FROM AUTHOR]

Hollow spheres are usually fabricated by hard template methods or soft template methods with soft surfactants, which is quiet tedious and time-consuming. In this paper, NiO hollow spheres with fluffy surface were successfully synthesized by a facile hydrothermal method and subsequent calcination, where bubbles acted as the template. NiO hollow spheres exhibited excellent gas sensing performances, which results from its hollow structure and high specific surface area. In addition, a possible evolution mechanism of NiO hollow spheres was proposed based on experimental results. [ABSTRACT FROM AUTHOR]

Nanorod arrays possess a large surface area due to the orderly arrangement of monomers, and thus are considered as an ideal microstructure to be utilized in the interface-related process such as the gas-sensing reaction. But their adoption is plagued by the complicated synthesis route in which the substrate is usually necessary. Here we propose a substrate-free fabrication of WO 3 nanorod arrays through the facile hydrothermal method. Subsequent measurements testify the superior NH 3 -sensing property of WO 3 nanorod arrays. The corresponding response is as high as 8.3 at a concentration of 50 ppm and a temperature of 200 °C, surpassing other WO 3 -based NH 3 sensors reported. [ABSTRACT FROM AUTHOR]

The monodisperse hexagonal WO 3 (h-WO 3 ) nanowires were synthesized using hydrothermal treatment through the acidification of Na 2 WO 4 · 2H 2 O by addition of K 2 SO 4 and Na 2 SO 4 . The obtained products were characterized using X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy. It showed a high crystallinity and good dispersity of nanowire structure with the exposure of < 200 > crystal facets. Based on h-WO 3 products, thin film sensors were prepared. The gas-sensing properties to various concentrations (10, 20, 50, 100, and 200 ppm) of ethanol and formaldehyde were investigated. The h-WO3 nanowires exhibited high responses to both ethanol and formaldehyde gas. The sensor exhibited remarkably good response and fast response/recovery time, which were as short as 6–8 s. A possible reason for the influence of oxide structure on the sensing properties of thin film sensors is proposed. This work shows great potential for the preparation of 1D h-WO 3 nanostructures and their application in the detection of toxic gases. [ABSTRACT FROM AUTHOR]

Monodisperse hexagonal tungsten oxide (h-WO 3 ) nanowires were novelly prepared on a large scale by the hydrothermal method with the assistance of K 2 SO 4 and Na 2 SO 4 . The morphologies and structures of the nanowires were characterized by X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (TEM). These nanowires with a diameter of 80 nm and high crystallinity are especially bundles-like structure, which are growth from primary particles with same growth direction of [001] and the exposure to 〈200〉 facets. These primary nanoparticles are believed to have a crystal structure of hexagonal prism morphology. Based on the TEM characterizations and crystal structure analyses, the morphology evolvement and is given and the growth mechanism is discussed. This research is potentially applied to controlled synthesis 1D semiconductor oxides through hydrothermal route. [ABSTRACT FROM AUTHOR]

Nanoneedle-assembled hierarchical and nanosheet-assembled hierarchical NiO nanoflowers were successfully synthesized via a facile hydrothermal method and subsequent calcination. And we proposed their growth mechanisms and the influences on gas-sensing properties. The results indicated that the gas sensing properties of NiO nanocrystals can be dramatically enhanced by tailoring the nanoscale building blocks. In addition, it was surprisingly noticed that the nanoneedle-assembled hierarchical NiO structures exhibited quicker gas response and recovery than the nanosheet-assembled ones. While nanosheet-assembled hierarchical NiO nanoflowers demonstrated higher gas response towards ethanol. [ABSTRACT FROM AUTHOR]

Novel sparse-type and close-type NiO nanoflowers have been controllably synthesized via hydrothermal process assisted with CTAB and SDS, respectively. The sensing performance of the close-type NiO was superior to the other, which benefits from the following factors: In the close-type nanoflower, (1) the architecture is more porous and closer; (2) more nanojunctions between adjacent nanosheets are formed; (3) abundant micro reaction rooms are assembled by nanosheets; (4) the thickness of nanosheets are much smaller than twice Debye length. [ABSTRACT FROM AUTHOR]

A unique nanoflower assembled from porous nanosheets was synthesized successfully via a novel one-step hydrothermal method for the first time. Namely, there was no calcination conducted on the whole preparation process, which was different from what the previous researches did. The unique architecture was characterized in detail using X-ray diffractometer, field-emission electron microscope. A possible growth mechanism was further proposed. We find that the obtained material shows a very excellent gas-sensing performance due to unique architecture with lots of pores on the petals. [ABSTRACT FROM AUTHOR]

Nanomaterials with low-dimensional architectures frequently exhibit novel functional properties. In current work, NiO nanobelts with well-defined morphologies and uniform size have been successfully synthesized via a facile hydrothermal method. Furthermore, a novel growth mechanism of NiO nanobelts has been proposed in detail. Surprisingly, it is worth mentioning that the sodium oxalate is of great benefit to the formation of NiO one-dimensional nanostructures and plays a vital role on tailoring morphologies of nanobelts on the basis of further comparative experiments. Such a synthetic way may open up an avenue to prepare some other oxides. [ABSTRACT FROM AUTHOR]

Molybdenum trioxides (MoO 3 ) with flower-like hierarchical structure and distinct nanobelts have been synthesized via a hydrothermal method. A series of comparative experiments show that cetyltrimethyl ammonium bromide (CTAB) and HNO 3 have evident impact on forming the morphologies of MoO 3 . Interestingly, the add order of CTAB and HNO 3 can be also a determinant factor in the assemble process. This research is of great significance in the preparations, characterizations and applications of various 1D and 3D semiconductor metal oxides. The possible growth mechanism is also proposed. [ABSTRACT FROM AUTHOR]

The selection of electrode materials and the optimization of electrode configurations are two effective approaches to achieve high-performance energy storage. As a representative ternary metal oxide, CoMoO 4 has been directly grown on the carbon cloth via a facile hydrothermal method and subsequent calcination, forming a binder-free electrode. Further measurements reveal that this electrode is composed of CoMoO 4 nanosheets assembled 3D-framworks (NAFs) and thereby shows a superb electrochemical property in KOH solution. It is worth mentioning that the specific capacitance reaches as high as 1234 F/g at the current density of 1 A/g, which exceeds most of CoMoO 4 and CoMoO 4 -based composites reported so far. Meanwhile, when the current density increases to 10 A/g, a considerable specific capacitance of 446 F/g is still obtained and can maintain nearly unchanged after 5000 cycles. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles, nanoplates and nanoflowers have been successfully synthesized via a facile hydrothermal route, and their microstructures and gas-sensing properties to ethanol were investigated. Among all the nanostructures, the nanoplates-assembled nanoflowers exhibited significantly higher gas-sensing performances than the others, which may ascribe to their hierarchical architectures with large specific area and abundant spaces for gas diffusion. Furthermore, we surprisingly found that the concentration of surfactant CTAB used had an essential effect on the ultimate morphology of the hierarchical nanoflowers. We hoped our findings could be in favor of further investigations on the fabrication of perfect hierarchical architectures. [ABSTRACT FROM AUTHOR]

Nanomaterials with three-dimensional architectures, frequently exhibiting novel functional properties, have attracted considerable attention of the researchers. In current work, we have successfully synthesized the NiO flower-like microspheres with abundant nanoparticles adhering to the petals via a facile hydrothermal method. Interestingly, it is found that the excellent gas sensing properties of the samples towards ethanol are likely attributed to the well-aligned porous architectures as well as great amounts of nanoparticles adhering to the petals, considered as active sites. Meanwhile, we also elaborated a distinctive growth mechanism of such a unique architecture and a plausible gas sensing mechanism, respectively. [ABSTRACT FROM AUTHOR]

We report the successful synthesis of novel Sn 2 O 3 with hierarchical 3D nanostructures via a facile hydrothermal method for the first time. The as-prepared Sn 2 O 3 products transform into SnO 2 after calcinations (800 °C) and a simultaneous TGA and DSC analysis of the as-prepared Sn 2 O 3 sample determines that the main increment of mass takes place in the temperature range 534–800 °C. The well-defined nanostructures are composed of thin nanosheets. The growth mechanisms are also discussed by observing the morphology revolution at various reaction times. Furthermore, the oxidation states of the Sn 2 O 3 hierarchical nanostructures are confirmed by the shape analysis of corresponding XPS O 1 s and Sn 3 d peaks using the decomposition procedure. [ABSTRACT FROM AUTHOR]

The thorn-like surface can avert the compact stacking of nanoparticles through the mutual supporting of thorns, while the hollow structure can provide more active sites by the utilization of the inner surface. On account of these, we reported the facile synthesis of self-supporting MnCo 2 O 4 hollow structures using a hydrothermal way and subsequent calcination. Fluorine-coordinated metal ions (Mn 2+ and Co 2+ ) react with OH − and CO 3 2− , generating the initial nanoparticles. Nanoparticles then go through a two-step assembly and a gas-driven deformation, ultimately forming the aforementioned morphology. In this process, the fluorine ion and the urea are regarded to play significant roles. [ABSTRACT FROM AUTHOR]

Nanorod-assembled flower-like ZnO was successfully synthesized using a simple hydrothermal method. The measurement results demonstrated that the ethanol sensing properties of the as-prepared ZnO nanostructure were improved once under UV illumination, with higher response and faster response-recovery speed as compared to that in dark condition. The sensing enhancement could be ascribed to the co-effect of the 3D ZnO nanostructure and UV irradiation. Specifically, the 3D framework constructed from 1D nanorods provided plenty of reaction sites and effective gas diffusion pathways. In addition, owing to photo-induced electron-hole pairs under UV irradiation, more energetically free carriers interacted with gas molecules, which accounted for the improvement in ethanol sensing behaviours. [ABSTRACT FROM AUTHOR]

The development of advanced materials for energy storage and gas sensing applications has gained significant attention in recent years. In this study, we synthesized and characterized PANI@MnO 2 @rGO ternary nanocomposites (NCs) to explore their potential in supercapacitors and gas sensing devices. The ternary NCs were synthesized through a multi-step process involving the hydrothermal synthesis of MnO 2 nanoparticles, preparation of PANI@rGO composites and the assembly to the ternary PANI@MnO 2 @rGO ternary NCs. The structural, morphological, and compositional characteristics of the materials were thoroughly analyzed using techniques such as XRD, FESEM, TEM, FTIR, and Raman spectroscopy. In the realm of gas sensing, the ternary NCs exhibited excellent performance as NH 3 gas sensors. The optimized operating temperature of 100 °C yielded a peak response of 15.56 towards 50 ppm NH 3. The nanocomposites demonstrated fast response and recovery times of 6 s and 10 s, respectively, and displayed remarkable selectivity for NH 3 gas over other tested gases. For supercapacitor applications, the electrochemical performance of the ternary NCs was evaluated using cyclic voltammetry and galvanostatic charge-discharge techniques. The composites exhibited pseudocapacitive behavior, with the capacitance reaching up to 185 F/g at 1 A/g and excellent capacitance retention of approximately 88.54% over 4000 charge-discharge cycles. The unique combination of rGO, PANI, and MnO 2 nanoparticles in these ternary NCs offer synergistic advantages, showcasing their potential to address challenges in energy storage and gas sensing technologies. Proposed NH 3 gas sensing mechanism for PANI@MnO 2 @rGO ternary nanocomposite based sensor. [Display omitted] • Synthesized PANI@MnO 2 @rGO NCs in multistep process. • Confirmed successful component integration with characterization techniques. • Explored NCs for supercapacitors and gas sensing applications. • Achieved gas response of 15.56 for 50 ppm NH 3 gas at optimized temperature. • Observed C sp of 185 F/g at 1 A/g with 88.54% retention over 4000 cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract The flower-like hollow CeO 2 spheres decorated MnO 2 composite was successfully prepared by a simple two-step hydrothermal process. When utilized for oxygen reduction reaction (ORR), such electrocatalyst exhibit the highly efficient catalytic activity for ORR than that of flower-like MnO 2 and hollow CeO 2 spheres monomers, which may be attributed to the enhanced mechanism arising from the hierarchical architecture as well as the synergetic effect of the MnO 2 and CeO 2. Highlights • A flower-like hollow CeO 2 spheres decorated MnO 2 composite was synthesized hydrothermally. • The CeO 2 /MnO 2 composite possessed excellent electrocatalytic activities. • The synergistic effect between CeO 2 and MnO 2 plays a vital role in the ORR. Abstract Herein, novel multiple hollow CeO 2 spheres decorated nanosheet-assembled MnO 2 microflower as an electrocatalyst towards oxygen reduction reaction (ORR) was successfully synthesized through a two-step hydrothermal approach. It is surprising to find that this composite with unique architecture exhibits a superior ORR catalytic activity than that of flower-like MnO 2 and hollow CeO 2 spheres monomers. The ORR catalytic activity is also comparable to that of 20 wt% Pt/C. The excellent electrocatalytic performance for ORR attributes to the synergistic effect between the hollow CeO 2 spheres and hierarchical nanosheet-assembled MnO 2. [ABSTRACT FROM AUTHOR]

We present an unusual and unique bismuth oxychloride (BiClO) hollow nanotube fabricated by a facile and simple hydrothermal method without using any surfactant and template, such research are rarely reported to the public. Morphology analysis (SEM, TEM) revealed that the synthesized nanotube had a typical one-dimensional hollow nanostructure with a diameter of 45 nm. XRD result showed that the nanotube was pure BiClO phase without any impurity. Moreover, KMnO 4 served as an effective oxidizing and etching agent in this process, which contributed to the novel and regular hollow structure. The specific growth mechanism is also proposed and discussed systematically and scrupulously. [ABSTRACT FROM AUTHOR]

Cu-doped δ-MnO 2 microspheres are rationally synthesized via a simple and facile hydrothermal process without using any template and surfactant. The samples are characterized by XRD, EDS, SEM, TEM and BET for their structure, morphology, elemental composition and specific surface area. The prepared Cu-doped δ-MnO 2 samples are further investigated as electrodes for solid state flexible supercapacitor, which is expected to deliver a high specific capacitance (300 F g −1 at scan rate of 5 mV s −1 ), a maximum energy density of 47.4 Wh kg −1 at a power density of 259 W kg −1 and long-term cycling stability (89.7% capacitance retention after 5000 times repetition at current density of 5 A g −1 ). Electrochemical impedance spectroscopy (EIS) demonstrates the low resistance nature of the prepared sample. All of the results suggest that the solid state MnO 2 device with excellent electrochemical performance and low cost has a vast potential for significant and clean power source in the future. [ABSTRACT FROM AUTHOR]

In the work, four types of typical morphologies of differently dimensional pure V 2 O 5 nanostructures including nanoflowers, nanoballs, nanowires and nanorods were synthesized through a simple hydrothermal method. The morphology of the product depends on the types of solvent and acid. Hierarchical nanoflowers and zero-dimensional (0D) nanoballs of V 2 O 5 nanocrystals were obtained when using C 2 H 5 OH as solvent. One dimensional (1D) nanowires and nanorods were obtained if H 2 O was used to participate in the reaction. The morphology and structure of the samples were characterized by XRD and SEM, respectively. The electrochemical behaviors of nanoflowers, nanoballs, nanowires and nanorods as electrodes in a supercapacitor device were tested using cyclic voltammetry (CV) curves and galvanostatic charge–discharge (GCD) curves. The electrochemical test results indicate that the rod-like structure leads to a significant improvement of storage capacity, electrochemical kinetics and rate capability. And 1D V 2 O 5 nanorods show the largest specific capacitance of 235 F g −1 at the current density of 1 A g −1 when used as supercapacitor electrode in 1 mol/L Na 2 SO 4 electrolyte. It turns out that 1D V 2 O 5 nanorod is an ideal material compared with other morphologies for supercapacitor electrode. [ABSTRACT FROM AUTHOR]

Urchin-like α-MnO 2 nanostructures were successfully synthesized via a simple hydrothermal process at different synthesis temperatures without using any template or surfactant. The microstructure and morphology of as-synthesized products were systematically investigated by focused ion beam, transmission electron microscopy, and high-resolution transmission electron microscopy. The electrochemical test of the prepared MnO 2 exhibits ideal cyclic voltammetry behavior, high specific capacitance (151.5 F g −1 at a current density of 1 A g −1 ) and excellent cycling stability (93.4% capacitance retention after 1000 cycles) which suggests its promising application as supercapacitor. [ABSTRACT FROM AUTHOR]

In this article, a sealed nanotube of ZnO was successfully obtained by a simple hydrothermal technique, which employed Hexamethylene tetramine (HMT) and Fluorinion (F−) as the active agents. The rod-like nanotubes structures were observed through field-emission scanning electron microscopy. The high-resolution transmission electron microscope exhibited a shell-enclosed nanotube structures. On the basis of experimental observations, including temperature, pH of the solution and acting agents, a growth mechanism was proposed. The as-prepared nanostructures showed excellent gas sensitivities to different gases (ethanol, ammonia gas, formaldehyde gas) with a quite low concentration respectively. [ABSTRACT FROM AUTHOR]

In this work, the pure and Ni-doped Bi 2 WO 6 are successfully synthesized by a one-step hydrothermal method. We apply the various techniques, such as X-ray diffraction (XRD), Scanning Electron Microscope (SEM),Transmission Electron Microscope (TEM), Ultraviolet–visible spectroscopy (UV–vis) and photo luminescence (PL) et al., to characterize the structure, morphology, chemical compositions, optical properties and crystal defects of the prepared samples. Compared with pure Bi 2 WO 6 and other Ni-doped Bi 2 WO 6 , the 4 at% Ni-Bi 2 WO 6 sensor exhibits the highest gas response (31.2), fast response-recovery characteristic, good stability and unique selectivity to 30 ppm n-butanol at 325 ℃. The enhanced gas sensing mechanism could be attributed to its unique hierarchical hydrangea-like structure, the large specific surface area, the low band gap energy, high electron separation efficiency and abundant oxygen vacancies. We have fabricated the pure Bi 2 WO 6 and Ni-doped Bi 2 WO 6 successfully. The as-fabricated 4 at% Ni-doped Bi 2 WO 6 gas sensor shows superior gas-sensing performance toward n-butanol. [Display omitted] • The pure and Ni-doped Bi 2 WO 6 were successfully synthesized by hydrothermal method and the 4 at% Ni-Bi 2 WO 6 exhibits hydrangea-like morphology with hierarchical structures. • The Ni-doped Bi 2 WO 6 gas sensor presented a largely enhanced gas sensing properties to n-butanol. • The 4 at% Ni-doped Bi 2 WO 6 gas sensor showed excellent gas sensing properties to n-butanol. • The introducing Ni into Bi 2 WO 6 can increase oxygen vacancies and improve high electron-hole pairs separation efficiency. [ABSTRACT FROM AUTHOR]

• Facile hydrothermal synthesis and characterizations of α-MnO 2 nanoparticles. • Utilization of synthesized α-MnO 2 nanoparticles to fabricate ethanol gas sensor. • At temperature of 300 °C and 200 ppm ethanol the gas response was 30.6. • The response and recovery times were 30 s and 40 s, respectively. α-MnO 2 nanoparticles were hydrothermally synthesized and characterized for their various physicochemical properties using different techniques. The average diameter of the nanoparticles was observed to be 70 ± 5 nm along with well-resolved inter-planar spacing of 0.241 nm corresponding to (211) plane for α-MnO 2 crystal phase. Working electrode for ethanol gas sensing fabricated by using α-MnO 2 nanoparticles showed gas response of 30.6 at optimized temperature of 300 °C. The corresponding response and recovery times were 30 s and 40 s, respectively for 200 ppm ethanol at 300 °C. [ABSTRACT FROM AUTHOR]

• The hierarchical WO 3 /NiO porous microsphere and rough microsphere were synthesized via hydrothermal process. • The gas sensor based on the porous microsphere shows more excellent performances to ethanol. • The possible mechanism involved in enhancing the gas sensing performances was discussed in detail. Two novel hierarchical WO 3 /NiO microspheres with porous and rough surface have been prepared through a simple one-stop hydrothermal method. Interestingly, it is a surprise that the introduction of different amounts of WO 3 plays a critical role in the growth and self-assembly of nanosheets and then the morphology of microsphere. Further gas sensing experiment demonstrates that the sensor based on porous microsphere possesses prominent performance towards 100 ppm ethanol at the optimal working temperature of 300 °C compared with that of rough microsphere. It is believed that the enhanced gas sensing properties benefit from the porous structure on the surface with abundant active sites and gas passages for sufficient gas adsorption and diffusion. [ABSTRACT FROM AUTHOR]

The two-dimensional (2D) honeycomb-like nanoplates assembled by nanosheet arrays were synthesized using one-step hydrothermal method and the growth mechanism of this nanostructure was proposed. The sensor based on as-prepared NiO exhibits superior gas-sensing properties to CO. The results verified that the hollow structure of 2D nanoplates could enhance the gas sensing performance by providing sufficient gas diffusion pathways and reaction sites in the gas-sensitive process. • The novel 2D honeycomb-like NiO nanoplates assembled by nanosheet arrays were synthesize. • The possible growth mechanism of the honeycomb-like NiO nanoplates was discussed in detail. • The effect of hollow 2D honeycomb-like nanostructure on gas-sensing properties of NiO nanoplates was discussed. Herein, we successfully prepared the Nickel oxide (NiO) nanomaterials with the structure of two-dimensional (2D) honeycomb-like nanoplates assembled by nanosheet arrays through the hydrothermal synthesis. In addition, the growth mechanism of this unusual nanostructure was proposed. Surprisingly, such NiO nanoplates exhibits superior gas-sensing properties to CO, which is mainly attributed to the hollow structure produced by the arrangement of nanosheets, contributing not only enough gases diffusion pathways but sufficient reaction sites during the gas sensing processes. [ABSTRACT FROM AUTHOR]

In this study, we reported a successful synthesis of a nanocomposite based on SnO2 nanoneedles anchored to NiO microsphere by a simple two-step hydrothermal route. The results show that the SnO2/NiO nanocomposite-based sensor exhibits more prominent performances than the pristine NiO microsphere to NO2 such as larger responses and more outstanding repeatability. The improved properties are mainly attributed to the p–n heterojunctions formed at the SnO2–NiO interface, leading to the change of potential barrier height and the enlargement of the depletion layer. Besides, the novel and unique nanostructure provides large and effective areas for the surface reaction. In addition, a plausible growth mechanism and the enhanced sensing mechanism were proposed to further discuss the special nanostructure which will benefit the exploration of high-performance sensors. [ABSTRACT FROM AUTHOR]