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.
•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.
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.
Specifically engineered three‐dimensional (3D) and 1D morphologies are expected to play significant roles in the development of next‐generation dye‐sensitized solar cells. In this study, using a ...hydrothermal approach without a surfactant or template, we attempted to synthesize a 3D hierarchical rutile titanium dioxide (TiO2) architecture by varying the growth temperature and time. X‐ray diffraction patterns of the synthesized TiO2 correlated well with rutile TiO2. Scanning electron microscopy images exhibited different nanostructures, such as nanorods, aggregated nanorods, and 3D TiO2 microflowers comprised of nanorods at 100°C, 130°C, and 160°C, respectively, after growth for 6 h. A significantly improved efficiency was observed for the TiO2 microflowers. The TiO2 microflowers exhibited an efficiency of 1.16%, short‐circuit current density of 12.8 mA cm−2, open‐circuit voltage of 0.692 V, and fill factor of 0.67.
TiO2 hierarchical structures synthesized by varying time and temperature. The spray technique was utilized to fabricate the 3D TiO2 photoanode. OH− and Cl− ions played a vital role in the formation of nanostructure. TiO2 microflowers showed Jsc = 12.8 mA cm−2, VOC = 0.692 V, and FF = 0.67.
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•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.
Construction of heterojunction photocatalyst with charges separation is essential in photocatalysis for solar energy conversion. In this work, CuO/ZnO nanocomposites were synthesized with different ...Cu/Zn weight percentage. The morphological transformation from hollow dumbbell to nanosheets was observed with change in Cu/Zn percentage. Moreover, the CuO/ZnO nanocomposite shows good adsorption and photocatalytic decomposition capacity for Methylene Blue (MB). The CuO/ZnO nanocomposites improve the transfer and electron and hole pairs separation. Compared to TiO2, the CuO/ZnO nanocomposite with 5 wt% of Cu shows enhanced activity with MB degradation of 96.57% in 25 min. The enhanced performance of nanocomposite was explained by the p–n junction interface which hinders the electron-hole pair recombination.
•The morphology transformation from hollow dumbbell to spindles was observed.•The functional properties of the CuO/ZnO nanocomposite were studied.•The CuO/ZnO hetero-junction improved the separation of photogenerated electrons and holes.•Synergetic interaction of CuO/ZnO was achieved for photocatalytic application.
Low energy density of the supercapacitors is considered as a roadblock for its application in or as a primary power source. While, utilization of high energy density battery-type electrode materials ...in an asymmetrical configuration was expected to resolve this hurdle, however, its inferior rate performance and poor cycling stability hinder the overall device performance. Incomplete utilization of active material at elevated current density was identified as the root for poor rate performance. Herein, we developed a hierarchical NiS microspheres build by the self-assembly of hexagonal nanoplates via trimethylamine (TEA) assisted hydrothermal method. The optimized sample exhibited a superior specific capacitance of 606 C/g at 0.5 A/g. More interestingly, the electrode was able to retain 50% (302 C/g at 20 A/g) of its maximum capacity even when the current density was multiplied 40-fold relative to 18% (50 C/g at 20 A/g) shown by control sample prepared without TEA. Excellent rate performance of the electrode could be attributed to the increment in the electrolyte-accessible surface area by morphological modifications. Owing to its porous nature, optimized sample was able to retain 93% of its original capacity at the end of 2000 continuous cycles of charge-discharge. Furthermore, an asymmetric supercapacitor with NiS-C as the positive electrode and activated carbon as the negative electrode delivered a high energy density of 35.07 Wh/kg at a power density of 0.420 kW/kg within an operating voltage window of 1.5 V.
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The design and construction of state-of-the-art wearable thermoelectric materials are important for the development of self-powered wearable thermoelectric generators (WTEGs). ...Molybdenum disulfide (MoS2) has been reported as a noteworthy thermoelectric (TE) material because of its large intrinsic bandgap and high carrier mobility. In this work, Cu-doped two-dimensional layered MoS2 nanosheets were grown on carbon fabric (CF) via a hydrothermal method. The electrical conductivity, Seebeck coefficient, and power factor for the Cu-doped MoS2 were found to increase with increasing temperature. The maximum Seebeck coefficient was obtained for a MoS2 sample doped with 4 at% of Cu (CM4) was ∼10 μV/K at 303 K and ∼13 μV/K at 373 K. The enhancement in the Seebeck coefficient was attributed to an energy-filtering effect caused by the interfacial barrier between MoS2 and Cu. In addition, a thermoelectric device was designed with four pairs of TE materials, where CM4 (4 at%) was used as a p-type material and Cu wire was used as an n-type material. These p- and n-type materials were connected electrically in series and thermally in parallel to generate a voltage of 190.7 μV at a temperature gradient of 8 K.
Reduced graphene oxide (rGO) was successfully deposited on the surface of cotton fabric by a hydrothermal method. Raman spectroscopy reveals that rGO contain sp2 hybridized carbon atoms. ...Field-emission scanning electron microscopy image indicated the deposition of rGO on the cotton fabric. Elemental mapping analyses confirmed the uniform distribution and coating of rGO on the cotton fabric. Ultraviolet protection factor (UPF) of rGO-deposited fabric before and after laundering was 442.69 and 422.32 respectively, while the bare fabric had 7.83. Thus the durability of rGO-deposited cotton fabric was enhanced than the bare cotton fabric. The UV tests indicates that the fabric incorporating reduced graphene oxide could dramatically enhance the UV blocking property compared with bare cotton fiber.
•rGO was successfully deposited on cotton fabric by hydrothermal growth.•Enhanced ultraviolet protection factor was obtained.•Functional properties revealed that the rGO coated cotton fabric possessed excellent properties.
•Diluted magnetic semiconducting TM (Ni, Mn, Co) doped ZnO thin films were fabricated by sol–gel spin coating technique.•The XRD analyses revealed that the TM (Ni, Mn, Co) doped ZnO films have ...hexagonal wurtzite structure.•Photoluminescence and micro-Raman spectra were interpreted for TM (Ni, Mn, Co) doped ZnO thin films.•SEM morphology studies were made for Zn0.97 Ni0.03O, Zn0.97 Mn0.03O and Zn0.97 Co0.03O thin films.•Room temperature ferromagnetism was observed in TM (Ni, Mn, Co) doped ZnO thin films.
Pure and transition metal (TM=Ni, Mn, Co) doped zinc oxide (ZnO) thin films were prepared by sol–gel spin coating method with a concentration of 0.03mol% of transition metals. X-ray diffraction studies revealed the polycrystalline nature of the films with the presence of hexagonal wurtzite structure. UV transmittance spectra showed that all the films are highly transparent in the visible region and in the case of doped ZnO thin films, d–d transition was observed in the violet region due to the existence of crystalline defects and grain boundaries. The optical band gap of the films decreases with increasing orbital occupation numbers of 3d electrons due to the orbital splitting of magnetic ions. Ultraviolet and near-infrared electronic transitions were observed which reveals a strong relationship with the doping of transition metal into ZnO site. The observed luminescence in the green, violet and red regions strongly depends on the doping elements owing to the different oxygen vacancy, oxygen interstitial, and surface morphology. The surface morphology of thin films was investigated by scanning electron microscope (SEM). The energy dispersive X-ray analysis (EDX) confirmed the stoichiometric composition of the TM doped ZnO thin films. Magnetic measurements at room temperature exhibited well defined ferromagnetic features of the thin films.
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