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.
•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.
•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.
Nickel oxide nanoparticles have been synthesized in the presence of agarose polysaccharide by sol–gel method. The structure, morphology, optical and magnetic properties of the product was examined by ...X-ray diffraction, transmission electron microscopy, UV–visible spectrophotometer and superconducting quantum interference device magnetometer. The result of thermogravimetric analysis of the precursor product showed that the proper calcination temperature was 400 °C. X-ray diffraction result revealed that the obtained product was nickel oxide with face-centered cubic structure. TEM image demonstrated that the nickel oxide nanoparticles have spherical shape with size around 3 nm. Analysis of FTIR spectra confirmed the composition of product. The optical absorption band gap of the NiO nanoparticles was estimated to be 3.51 eV. Magnetic measurement showed that the nickel oxide nanoparticles exhibit superparamagnetic behavior at 300 K. Moreover, the nanoparticles show ferromagnetic interactions at 4.2 K owing to the existence of uncompensated moments on the surface of the nanoparticles.
The technique of facile co-precipitation was employed to prepare the pure ZnO and Gd doped ZnO photocatalysts. The physio-chemical properties of the prepared samples were analysed through various ...analytical techniques. The X-ray diffraction analysis clearly shows that higher amount of Gd dopant creates the secondary phase in addition to normal peaks of ZnO crystals. The visible light absorption increases with increasing the Gd amount in ZnO which is evident from UV–Vis DRS analysis. The as synthesized 3% Gd doped ZnO exhibits the highest photocatalytic activity on Methylene blue dye degradation under visible light irradiation compared to other photocatalysts. The enhanced degradation activity of the photocatalyst demonstrates the improved visible light absorption of the materials due to the incorporation of Gd ions into the ZnO lattice. The possible reaction mechanism and degradation pathway of the photocatalyst has been discussed in detail and the stability of the catalyst have been confirmed by recycle process.
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•Facile co-precipitation method was used to prepare the pure and Gd doped ZnO photocatalyst.•The visible light absorption increases with increasing the percentage of Gd.•The Methylene blue dye degradation efficiency reaches 93% under visible light irradiation over 3% Gd doped ZnO.
Controlled growth of BiVO4 nanostructures along (121) and (040) crystal facets plays a crucial role in enhancing their catalytic performance. In this regard, the visible light active photocatalyst ...BiVO4 was synthesized concerning the effect of pH and surfactants by hydrothermal method. The morphology and size of BiVO4 are strongly dependent on the concentration of H+ and Bi3+ in the reaction system while varying the pH. Further, the significant role of cationic surfactant for obtaining the morphology of the spherical nanoparticles of BiVO4 powders with size 55 nm was analyzed. Adsorption behavior of as-synthesized samples was investigated through Langmuir isotherm model. The catalytic performance of BiVO4 photocatalyst with the degradation efficiency of 98.79% and 15.58% over the methylene blue (MB) and methyl orange (MO) dyes were noticed within 60 min of light irradiation respectively. The enhanced and declined catalytic activity was well correlated with the surface charge of BiVO4 photocatalyst towards the MB and MO dyes respectively. Further, the photocatalytic activity of mixed anionic and cationic dyes was performed. The degradation pathway of MB dye was analyzed by LC-MS for the identification of intermediate products. From the obtained results, the proposed possible photocatalytic mechanism reported.
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•The morphology of BiVO4 strongly depends on the concentration of H+ and Bi3+.•XRD, Raman confirms the well crystalline structure of pure monoclinic BiVO4.•Cationic surfactant CTAB play a key role for obtaining the controlled size of BiVO4.•Superior catalytic activity correlates with increase of (040)/(011) intensity ratio.•h+ and ▪ radicals are predominant oxidative species in the dye degradation process.
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► NiFe2O4 nanorods synthesized by co-precipitation method at high concentration of PEO. ► PEO play an important role in the formation, size and shape control of the nanorods. ► ...Nanorods with representative diameter of 60–65nm and length of 142–147nm. ► The shape anisotropy enhances the coercive field and decreases the magnetization. ► Synthesized nanostructures exhibit ferromagnetic behavior at room temperature.
Highly ordered single crystalline nickel ferrite (NiFe2O4) nanorods have been successfully synthesized by a polymer assisted co-precipitation method using polyethylene oxide (PEO) as a capping and a polymer structure directing reagent. In this synthesis, the addition of high concentration of PEO seems to play an important role in the formation, size and shape control of the nanorods. Powder X-ray diffraction (XRD) and selected area electron diffraction (SAED) exhibit that the obtained nanorods can be indexed to single crystalline inverse spinel with Fd3m space group. The synthesized NiFe2O4 products were characterized in terms of their structural and magnetic properties. The morphological investigations using high resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) reveal that the grown products are rod-like structure with the diameters in the range of 60–65nm and length of 142–147nm. The coercivity of prepared nanorods with high concentration of PEO reached as high as 904.46Oe at room temperature (300K), superior to that of nanoparticles obtained with low concentration of PEO. Hence, it can be used for high frequency electronics and gas sensing applications. On the basis of these experimental results, possible influence mechanisms in the growth processes are discussed.
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.
In this paper, our main aim is to introduce the concept of planar
p-harmonic mappings and investigate the properties of these mappings. First, we discuss the
p-harmonic Bloch mappings. Two estimates ...on the Bloch constant are obtained, which are generalizations of the main results in Colonna (1989)
9. As a consequence of these investigations, we establish a Bloch and Landau's theorem for
p-harmonic mappings.
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.
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