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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]

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]

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]

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]

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]

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]