Safety is an essential consideration in the utilization of hydrogen energy due to its potential risk of explosion. Thereby, the synthesis of hydrogen sensors with highly sensitive properties is ...required for the early detection of hydrogen leaks. Here, a low-cost process was applied to fabricate PdO-decorated NiO H2 sensors capable of detecting sub-ppm H2 concentration. Unlike the previous two-step noble metal modification strategy, in situ ultrasonic spray pyrolysis was used in this work to directly obtain the needle-like PdO decorated NiO structure. The doped PdO tends to segregate at grain boundaries of NiO in needlelike form and can inhibit crystal growth. The gas-sensing performance was investigated by the means of dynamic gas distribution. The results show that the gas response towards H2 could be enhanced significantly by PdO doping. Especially, the sprayed 2 at% PdO-decorated NiO film sensor shows the highest response and the lowest detection limit at 250 °C, with a response value of 82% to 50 ppm H2 and a detection limit of 500 ppb. It can be speculated that the surface state of NiO film could be heavily affected by PdO doping, which leads to the high performance of PdO-decorated NiO sensors.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The photocatalytic process is used to remove organic contaminants, dyes, industrial sewage from wastewater before reusing it for human consumption again. Here a simple cost-effective ultrasonic spray ...pyrolysis (USP) technique is used to deposit ZnO microflower on glass and stainless steel (SS) mesh in a single step. X-Ray Diffraction (XRD) and Raman spectroscopy indicate the polycrystalline wurtzite nature of ZnO. Field emission scanning electron microscope (FESEM) shows the ZnO microflower structure. PL and XPS studies show the oxygen defect in the films. Photocatalytic degradation results show that methylene blue (MB) dye with 1 × 10−5 M concentration can be degraded around 97.94% and 85% in 120min and 210 min with a degradation rate of 0.03035 min−1 and 0.00917 min−1 respectively using ZnO deposited on SS mesh and glass substrate in both UV–Vis and sunlight condition. ZnO deposited on SS mesh shows high repeatability performance to degrade the MB and it can degrade 96% of MB at 10th cycle. Degradation rate at base medium is higher than acidic medium. A plausible photocatalysis mechanism is also explained.
Display omitted
•A simple single step deposition of ZnO microflower on stainless steel (SS) mesh.•Degradation rate of MB for ZnO on SS mesh is more than thin film.•Highly repeatable performance over 10th cycle with 96% degradation for SS mesh ZnO.•Degradation rate at base medium is higher than acidic medium.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Copper oxide (CuO) thin films were grown on glass substrates by performing ultrasonic spray pyrolysis (USP) method at different substrate temperatures (300 °C, 400 °C, 450 °C, and 500 °C). The ...prepared CuO thin films were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX), UV–visible spectroscopy, and photoluminescence (PL) spectroscopy measurements in order to assess the effects changed substrate temperature on structural, morphological, and optical properties of the grown materials. Also, the suitability of the grown films as electrodes in supercapacitor applications was investigated with respect to variable substrate temperatures. The XRD patterns revealed that the samples were polycrystalline in nature exhibiting tenorite phase of CuO structure preferential orientation along (11 1‾) plane and the corresponding crystallite size ranged from 28.14 nm to 67.98 nm. The SEM images displayed morphological modifications in the prepared CuO thin films as the substrate temperatures incresed. The XPS and EDX analyses confirmed the successful deposition of aimed materials on the fabricated thin films. It was also obtained that optical absorbance decreased due to the increased substrate temperatures and optical energy bandgaps changed between 1.53 eV and 1.71 eV as the substrate temperatures varied. The electrochemical supercapacitive features of the CuO nanostructures thin films were studied with the help of cyclic voltammetry (CV), galvostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS).
•CuO thin films produced to assess their supercapacitor performance by using USP technique for the first time.•The effects of varied substrate temperatures found to lead modifications in structural parameters of CuO nanostructures.•Bandgap of CuO samples increased from 1.53 eV to 1.71 eV as substrate temperature increased.•Luminescence peaks of the grown CuO films affected by changes in substrate temperature.•The specific capacitance value of the CuO thin film electrodes was obtained as 1.4 F g−1.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•Using the USP method, Au supported ZnO particles were generated.•Au nanoparticles were dispersed inner and outer portions of the ZnO particles.•The optimal photocatalytic activity ...occurs with 0.1 mass% Au supported.•The optimal photolysis activity was exhibited at a dose of 10 mg of Ag/ZnO.
Environmental pollution by organic dyes used in industry is a serious problem in developing countries. Environmentally friendly treatment methods are being studied because conventional methods require chemical or additional decomposition treatment. In particular, oxidation via a photocatalyst is a promising alternative due to its chemical and physical stabilities and low cost. However, electron-hole recombination limits the photocatalytic activity in semiconductor photocatalysts such as ZnO and TiO2. This study investigates control of electron-hole recombination of the photocatalyst by loading Au on ZnO (Au/ZnO). Using the Ultrasonic Spray Pyrolysis (USP) method, Au/ZnO particle generation is easily achieved under various conditions. XRD analysis confirms the crystal peaks of ZnO and Au. The EDX mapping and STEM images of the particles show that the Au crystals are well dispersed in the inner and outer portions of ZnO. The photocatalytic decomposition rate of organic dye (Rhodamine-B) is faster than that of ZnO in all Au/ZnO particles, and the best photocatalytic activity occurs in particles with 0.1 mass% Au supported on ZnO particles. In addition, optimal photolysis activity occurs in 100 mL of 5 mg/L RhB aqueous solution and 10 mg dose of Au/ZnO particles.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The facile and affordable fabrication of sensors that can detect carcinogenic benzene has remained a long-standing challenge, as sophisticated nano-architectures and/or sensing films are essential to ...ensure benzene selectivity. Herein, we report a raisin bread-structured film fabricated by mixing two different types of oxide hollow spheres, as a novel, cost-effective platform for the highly selective and sensitive detection of benzene. The film comprises catalytic Pd-Co3O4 (i.e., raisins) and gas-sensing SnO2 hollow spheres (i.e., bread), prepared by ultrasonic spray pyrolysis. In contrast to films of pure SnO2 or Pd-Co3O4 hollow spheres, which are partially selective to reactive gases such as xylene/toluene/ethanol, raisin bread films are highly selective to less reactive benzene. Thus, an array of the SnO2, Pd-Co3O4, and raisin bread sensors enables exclusive benzene identification with principal component analysis. The superior benzene-sensing properties of raisin bread sensors are attributed to the oxidative consumption of reactive gases by the catalytic raisins, whereas less-consumed benzene sensitively reacts with the gas-sensing bread. This is supported by proton transfer reaction-quadrupole mass spectrometry analysis. This work provides a simple, rational strategy to attain gas selectivity to chemically stable benzene and is expected to trigger the development of ubiquitous portable devices to monitor airborne benzene.
Display omitted
•Raisin bread film is fabricated by mixing two different oxide hollow spheres.•The film shows high selectivity to benzene gas.•The sensing mechanism is confirmed via mass spectrometry-based analysis.•An electric nose composed of sensors with different gas selectivity is designed.•The exclusive identification of benzene in the electric nose is demonstrated.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Here, a specific metal oxide (CuO) and its impurity (Cr) added composites were grown onto glass substrates as nanostructured thin films by executing ultrasonic spray pyrolysis method. The effects of ...the varied Cr dopant concentration on the morphological, structural, optical and H2 gas sensor properties of the synthesized CuO thin films were determined by conducting scanning electron microscopy, X-ray Diffraction, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, ultraviolet–visible spectroscopy, and gas detection analyses. The X-Ray Diffraction analysis revealed the presence of CuO crystals with predominant (111) plane and it changed to (002) orientation for the doped samples, where crystallite sizes varied between 32 and 46 nm. The structural studies disclosed that the crystalline structure modified due to the added impurities. The scanning electron microscopy observations unveiled polyhedron-like shape formations of the synthesized nanostructures which also showed clear indications of changed morphology due to the impacts of different Cr doping percentages. Besides, the presence of copper, oxygen, and chromium was confirmed by EDX elemental analysis as well as X-ray photoelectron spectroscopy. The optical examination concluded that absorbance values followed a random trend with respect to the increased impurity contents while bandgap decreased with the increase of doping concentration. And, it was also noted that the luminescent emission peaks decreased in the photoluminescence spectroscopy as a result of introduced impurity levels. Finally, H2 responsivity was detected for the grown films and found out that the impurity doping notably increased the sensitivity of the gas sensor based on the prepared CuO nanostructures.
•USP technique performed to synthesize Cr doped CuO films and H2 gas sensitivity of the films tested for the first time.•Different impurity percentages noted to cause modifications in the structural parameters of CuO nanostructures.•Cr addition led to decrease the bandgap of CuO samples from 1.75 to 1.59 eV.•The PL emission intensities found to decrease as a result of Cr doping.•The H2 gas sensitivity of CuO films enhanced due to the presence of added Cr ions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The photoelectrochemical (PEC) water splitting approach is an interesting concept due to abundant solar energy source and economical viability. However, it is challenging to realize the theoretical ...potential of photoactive materials mainly because of intricate interactions between sunlight, semiconductors and liquid solutions. BiVO4 is one such promising material because of its favorable valence and conduction band position with a bandgap of ∼2.4 eV. In this work, thin films of BiVO4 (2 cm X 2 cm surface area) have been prepared through modified synthesis route by using robust USP technique. Further, BiVO4 doped with Mo or W elements of different atomic concentrations (3, 5, 7 and 9 at.%) have been prepared. The results indicate that doping of Mo and W in BiVO4 shown ∼2.5 times of higher photocurrent density as compared to pristine BiVO4. Poor electron–hole separation yield is one of the main limiting factors for BiVO4. The purpose of Mo or W-doping in this study is to increase the electron–hole separation yield which is resulted by improving the electron transport properties. Mo or W played a role of donor dopants by compensating cation vacancies or electrons, which contribute to increase in conductivity. Both structural and performance characterization of electrodes have been carried out to corroborate with the results. Increase in charge carrier density and decrease in charge transfer resistance unfolds the reason behind increase in photoelectrochemical performance.
•Comprehensive study of Mo and W doping into BiVO4 through modified synthesis route.•Both Mo and W doping showed nearly 2.5 times increase in photocurrent density.•Increase in charge carrier density and decrease in charge transfer resistance with doping.•Structural stability even at higher doping amounts.•Extensive coverage about synthesis, structural and performance characterization results.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tungstates are inorganic materials with great potential in diverse applications, mainly as a photoluminescent material as a candidate to replace traditional lighting sources. In this study, we report ...the synthesis and characterization of Zn1-xCaxWO4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) powders with white light-emitting properties. Using X-ray diffraction, the formation of the monoclinic ZnWO4 phase was observed for x = 0 and the formation of the tetragonal scheelite phase of CaWO4 was observed for x = 1. The formation of a heterostructure composed of both phases was found for compositions with x = 0.2, 0.4, 0.6 and 0.8. Scanning electron microscopy images showed that the Zn1-xCaxWO4 particles exhibit a spherical morphology. The band-gap energies had variation between 3.79 eV and 3.99 eV, being influenced by the degree of structural disorder. The photoluminescence emission spectra of the samples showed white light emission. Thus, Zn1-xCaxWO4 can be considered as promising white light sources, mainly for the sample synthesized with x = 0.8 for application in LED lamps (6500 K).
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nanostructured hollow spheres composed of K0·5Na0.5(WxNb1-x)O3 were synthesized by ultrasonic spray pyrolysis. Correlations between the W-doping content and properties of the NbO6 octahedra, ...including morphology, texture, crystalline structure, and polarization were found. Scanning and transmission electron microscopy analysis indicate the present samples are nanostructured hollow spheres. Textural analysis indicates the samples are composed of a balanced framework including micropores (40–50%) and mesopores (50–60%). Structural refinement by the Rietveld method indicated that non-isovalent W6+ cation only occupies the Nb5+ site in the host structure. Several space groups including Amm2, Pbcm, and Pm were used to refine the W-doped K0·5Na0·5NbO3 structure and the best adjustment was reached assuming the co-existence of two distinct symmetries. The FTIR bands associated with a corner-shared NbO6 octahedron suggested an increase in Nb–O bond length in agreement with the Rietveld refinement. In general, ultrasonic spray pyrolysis is an effective methodology for the one-step synthesis of nanostructured crystallites of W-doped niobate-based perovskites with a tailored structure and morphology.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
