Display omitted
•ZnO nanorods, Silver-doped ZnO nanoflower and nanoellipsoids were successfully synthesized.•SZO nanoellipsoids had wider optical absorption region than ZnO nanorods.•Silver-doped ZnO ...showed fast gas response and recovery time at 10ppm of ammonia concentration.•Silver-doped ZnO (6%) showed maximum response of 29 for 100ppm at 150°C.
High sensitivity ammonia gas sensor based on Ag/ZnO composite (SZO) nanostructures and their structural, optical, morphological and gas sensing properties were investigated. Field- emission scanning electron microscopy and high- resolution transmission electron microscopy revealed that pure ZnO flower-like nanorods transformed into nanoellipsoids upon adding of silver (Ag). Scanning transmission electron microscopy (STEM) analysis showed clear flower-like morphology of Ag/ZnO composite. STEM-mapping measurement showed that Zn, Ag and O were homogeneously distributed. The ammonia gas sensing analysis revealed that the Ag/ZnO (6wt%) showed higher gas response compared with other content of Ag wt%. Ag/ZnO (6wt%) exhibited the highest response of 29.5 when exposed to 100ppm ammonia gas. Interestingly, Ag/ZnO (6wt%) possessed good response and recovery property of 13 and 20s at low concentration of ammonia at 10ppm, respectively. The mechanism of gas sensing and enhanced gas response of pure ZnO and Ag/ZnO composite was discussed.
The supercapacitors have been widely used in the field of electronics appliances and automobiles, but its utility is limited by low energy density and poor specific capacitance. Energy density and ...specific capacitance of the supercapacitor is invariably determined by the electrode materials. Herein, a novel 3D flower-like CuO/Co3O4/r-GO heterostructure was synthesized by the hydrothermal method and used as an anode material for high-performance supercapacitors in an alkaline electrolyte solution. The as-prepared 3D flower-like CuO/Co3O4/r-GO heterostructure with high surface area provides vast interfacial contact area between electrode and electrolyte solution which offers a fast surface reaction kinetics and improved conductivity, thereby the remarkable electrochemical performance is achieved. The prepared CuO/Co3O4/r-GO heterostructure material shows an ultra-high specific capacitance of 1458 Fg-1 at a current density of 0.5 Ag-1, exceptional rate capability, and stable long- term cycling performance (97% retention after 10000 successive charge-discharge cycles at 5 Ag-1). In as-assembled asymmetric supercapacitor, CuO/Co3O4/r-GO heterostructure is an anode material and r-GO is a cathode material. The assembled device shows a high specific capacitance of 198 Fg-1 at 2 Ag-1, an ultra-high power density of 10510.30 W kg−1, and a high energy density of 34.20 Wh kg−1. Meanwhile, the ASC device exhibits excellent rate capability (97%) after 10000 successive charge-discharge cycles at 5 Ag-1 in the PVA-KOH gel electrolyte.
•3D CuO/Co3O4/r-GO heterostructure was synthesized by a hydrothermal method.•Heterostructure material shows an ultra-high specific capacitance value.•Solids state ASC device was constructed using CuO/Co3O4/r-GO heterostructure.•ASC device provides an Ultra-high power and a high energy densities.
Exploring highly efficient visible-light-driven photocatalyst for the elimination organic pollutants is a great concern for constructing sustainable green energy systems. In the current work, a novel ...hybrid ternary WO3@g-C3N4@MWCNT nanocomposites have been fabricated for visible-light-driven photocatalyst by self-assembly method. The as-prepared photocatalyst was examined by XRD, Raman, FESEM, HRTEM, XPS EDS, EIS, UV–visible DRS, and PL analysis. The experimental results revealed that the photocatalytic activity of WO3@g-C3N4@MWCNT nanocomposites on the degradation of Tetracycline (TC) is 79.54% at 120 min, which is higher than the binary WO3@g-C3N4 composite and pristine WO3. The improved degradation performance towards TC is recognized for its higher surface area, intense light absorption towards the visible region, and enhanced charge separation efficiency. Consequently, the fabricated catalyst endows a promising application for antibiotic degradation.
Display omitted
•We fabricated WO3/g-C3N4/MWCNT hybrid nanostructure by simple low temperature hydrothermal process.•Photocatalytic degradation of TC were observed under visible light.•WO3/g-C3N4/MWCNT sample showed excellent degradation of tetracycline.•WO3/g-C3N4/MWCNT hybrid structure has been probed as a potential applicant for visible light driven photocatalyst.
•The decoration of CuO on the surface of ZnO were synthesized by hydrothermal growth.•The functional properties of the ZnO/CuO nanostructures were extensively studied.•The formation of ZnO/CuO ...hetero-junction improved the separation of photogenerated electrons and holes which results in enhanced activity.•The enhanced photocatalytic activity is 10 times higher than pure ZnO.
Degradation of organic pollutant using ZnO/CuO composites has become an attractive method for detoxification of water. The effect of copper acetate concentration and the functional properties of nanocomposites were investigated. The morphological analysis revealed that CuO nanoparticles dispersed uniformly on the surface of ZnO nanorods. X-ray photoelectron spectra analysis showed peak shift in the electronic states of Zn and Cu states. Elemental clearly confirms the presence of CuO were uniformly distributed on the surface of ZnO. The photocatalytic activity of ZnO/CuO composites was enhanced compared to pure ZnO under visible light irradiation. The optimal CuO content for the photocatalytic activity of the ZnO/CuO composites is 1%, which is almost ten times higher than that of pure ZnO. Owing to these synergic advantages, the degradation efficiency of ZnO/CuO composites reached 92.52% after 5min of irradiation. The synergistic photocatalytic mechanism was proposed based on the photodegradation results.
Numerous inorganic and organic counter electrodes (CEs) have been fabricated for dye-sensitized solar cells (DSSCs) instead of platinum (Pt) CE. However, MoS2 and carbon nanocomposite have played an ...important role in CEs due to their superior electrochemical properties and high chemical stability. N-doped graphene quantum dot (N-GQD) @ MoS2 @ reduced graphene oxide (rGO) nanocomposite was synthesized by the two-step hydrothermal method. The morphology of as-synthesized nanocomposites was studied using field emission scanning electron microscope (FE-SEM) and scanning transmission electron microscopy (STEM). It confirms the formation of sphere-like MoS2 composed of nanosheets on the surface of rGO sheets. The N-GQD@MoS2@rGO composites confirmed the presence of MoS2, rGO, and N-GQD by X-ray diffraction (XRD) and Raman spectra. The chemical composition and purity of N-GQD@MoS2@rGO was examined by the X-ray photoelectron spectroscopy analysis technique. The electrochemical property of the as-fabricated CEs was studied by cyclic voltammetry (CV) analysis by using the iodine-based electrolyte. The N-GQD@MoS2@rGO shows the superior catalytic property due to more electrochemical active site and electrical conductivity property of rGO and MoS2. The DSSCs device assembled with as-fabricated CEs and their photovoltaic power conversion efficiency (η) of MoS2 was 2.01%, MoS2@rGO was 3.92%, N-GQD@MoS2 was 3.53%, N-GQD@MoS2@rGO was 4.65%, and Pt was 5.17%.
schematic diagram of DSSCs fabrication with N-GQD@MoS2@rGO CEs. Display omitted
Ammonia is one of the most hazardous substance and highly toxic to human health when inhaled above the moderate level. Sensing ammonia is one most challenging task at low temperature level and room ...temperature. ZnO and Al-doped ZnO nanostructures were successfully synthesized by sol–gel method, and their structural, optical, morphological, and gas sensing properties were investigated. Field-emission scanning electron microscopy revealed that the ZnO nanorods transformed into particles upon incorporation of Al. Transmission electron microscopy and high-resolution transmission electron microscopy confirmed that both the ZnO nanorods and Al-doped ZnO nanoparticles were crystalline. Fourier transform infrared spectroscopy analysis indicated the presence of Zn–O and Al–O in the nanostructures. Energy-dispersive X-ray spectroscopy revealed the presence of Al in the Al-doped ZnO materials. The ammonia gas sensing analysis revealed that the Al-doped ZnO nanoparticles displayed a higher response than the ZnO nanorods. Moreover, among the doped samples, that containing 6 wt% Al dopant exhibited the highest response of 350 when exposed to 100 ppm ammonia gas. The higher sensing efficiency of the Al-doped ZnO nanostructures was attributed to changes in structural defects in Al-doped ZnO, as confirmed by X-ray photoelectron spectroscopy analysis.
•ZnO nanorods and AZO nanoparticle were synthesized.•AZO nanoparticle had wider optical absorption region than ZnO nanorods.•Sensing response of ammonia was enhanced by the incorporation of Al.•Al-doped ZnO (6%) showed maximum response of 350 for 100 ppm at room temperature.
Display omitted
Phonon scattering by intrinsic defects and nanostructures has been the primary strategy for minimizing the thermal conductivity in thermoelectric materials. In this work, we present ...the effect of Isovalent substitution as a method to decouple the Seebeck coefficient and the thermal conductivity of antimony (Sb) substituted bismuth selenide (Bi2Se3). Transmission electron microscopy studies present the nanostructured Bi2-xSbxSe3 thermoelectric system represents the coexistence of hierarchical defect structure and dislocations. The observed giant reduction in thermal conductivity is due to the multi-scale phonon scattering caused by a combination of stacking faults, lattice dislocations and grain boundary scattering. This study reveals that a large number of dislocations about ∼1.09 × 1016 m−2 are particularly effective at lowering thermal conductivity. We achieved one of the ultra-low thermal conductivity values (∼0.26 W/m K) for the maximized dislocation concentration. Moreover, Isovalent substitution provides a new avenue for the reduction in thermal conductivity and significant enhancement in the Seebeck coefficient of thermoelectric materials.
•Titanium dioxide (TiO2) nanorods under different pH conditions were synthesized by a hydrothermal method.•XRD results confirm the tetragonal structure of anatase phase TiO2 nanopowders.•The ...degradation of 67% of MO was achieved by the irradiation of UV light for 150 min.
Surfactant free Titanium dioxide (TiO2) nanorods under different pH conditions were synthesized by a hydrothermal method. The structure, morphology and framework substitution of the as – prepared nanorods was characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV–Visible, Fourier Transform Infrared (FTIR) and X-ray Photon Spectroscopy (XPS). XRD analysis confirms the formation of anatase phase of TiO2 with tetragonal structure. FESEM micrograph confirms the formation of nanorods. The calculated band gap values of TiO2 nanorods was found to decrease with increasing pH from the optical absorption spectra. XPS spectra confirm the presence of Ti 2p and O 1s states. The photocatalytic activity of the nanorods against methyl orange (MO) was examined and their results have shown highest degradation (51%) of MO was achieved within 150 min.
2-D-layered molybdenum disulfide (MoS2) and MoS2/TiO2 nanocomposite were synthesized by a hydrothermal method. The effects of the concentration of TiO2 on the formation of MoS2/TiO2 composites and ...functional properties were investigated. X-ray diffraction patterns revealed the formation of hexagonal and anatase structure of MoS2 and TiO2, respectively. Core-level X-ray photoelectron spectroscopy confirmed the presence of Mo and Ti interaction by a significant peak shift. Morphological analysis revealed the formation of TiO2 on the surface of the MoS2 nanosheets. The photocatalytic degradation of methylene blue (MB) in an aqueous suspension was employed to evaluate the visible-light activity of the as-prepared composite photocatalyst. The MB absorption peaks completely disappeared after 12 min with 99.33% of degradation under visible-light irradiation at the TiO2 concentration of 0.005 M. It was found that hydroxyl radical (&z.rad; OH) played an important role in the degradation of MB under visible-light irradiation. The possible charge-transfer mechanism has been proposed in this study.
Display omitted
•Ag intercalated Bi2Se3 samples were synthesised by hydrothermal method followed by cold pressing technique.•HRTEM images and IFFT pattern confirms the presence of stacking ...faults.•The slight fermi energy shift towards conduction band significantly improved the electrical conductivity.•Low lattice thermal conductivity of 0.3 W/mK obtained at 543 K by various scattering mechanism.•The peak zT of 0.3 was attained at 543 K due to the synergy of enhanced power factor and low lattice thermal conductivity.
Bismuth Selenide is a Tellurium free topological insulator in V-VI compounds with an excellent thermoelectric performance from room temperature to mid-temperature region. Herein, hydrothermally prepared polycrystalline Bi2AgxSe3 nanostructures have been reported for thermoelectric application. The crystal structure identification and morphology with the elemental presence were analyzed by XRD (X-ray diffraction), HR-SEM with EDS (High resolution scanning electron microscope with energy dispersive X-ray), and HR-TEM (High-resolution transmission electron microscope) measurements. The reduced lattice thermal conductivity and enhanced electrical transport properties synergistically boost the thermoelectric properties through the highly-dense stacking faults with the presence of dislocations. The IFFT (Inverse Fast Fourier Transform) pattern reveals the existence of stacking faults and dislocations. These highly dense stacking faults and dislocations act as active phonon scattering centers, which can contribute to effective phonon scattering resultsin extremely low lattice thermal conduction of 0.3 W/mK at 543 K. On the other hand, the involvement of phonon–phonon scattering primarily reduced the lattice thermal conductivity at elevated temperatures. In addition, phonon-carrier scattering was less compared to phonon–phonon scattering at elevated temperature region. Moreover, the enhancement of electrical conductivity and controlled reduction of the Seebeck coefficient plays a vital role in achieving the maximum power factor of 335 μW/mK2 at 543 K due to the energy filtering effect. The synergistic combination of low thermal conduction and the maximum power factor helps to achieve the high peak zT of 0.3 at 543 K.
PDF