The investigation reports on the transparent and conducting pure and metal doped zinc oxide (ZnO) thin layer. The layers are ultrasonic sprayed onto microscope glass substrates at 350 °C. The effect ...of Sn doping level (from 0% to 3%) is discussed in one hand and metal (Al, Cu and Sn) doping effect on the properties in other hand. Spectroscopic ellipsometry, optical, structural and electrical analyses of the as-grown films have been achieved. The (002)-oriented hexagonal wurtzite crystal structure is revealed by X-ray pattern having a grain size of 4.5–15 nm which confirms the nanosized aspect. The UV–VIS–IR spectrophotometer measurements reveal that the as-grown films are highly transparent in the visible and IR ranges (T~90%). A slight influence of dopants on the band gap energy which ranges between 2.24 and 2.29 eV is emphasized. The electrical parameters such as bulk density, resistivity and mobility are measured by Hall measurement system (HMS). The films thickness is estimated by spectroscopic ellipsometry values and found to be of 178–330 nm. The electrical properties confirm an enhancement of bulk density and conductivity within the range − 1.06 × 1012–5.09 × 1013 (cm−3) and 3.2 × 10−5–1.05 × 10−3(1/Ω cm) due to dopants incorporation as predicted. Inversion to p-type is demonstrated in Sn-doped ZnO sample. The nanostructures are observed in 2D scanned AFM views, size are of micro/nanometer and roughness is of 3.39–15 nm.
•ZnO layers are produced by low cost spray pyrolysis technique onto glass substrate.•Analyses by X-ray, UV-Vis and Ellipsometer spectroscopy of as-grown layers.•Effect of Sn doping level and metallic dopant on properties are evidenced.•Electrical and dielectric parameters of ZnO are studied at room temperature.•Sn-doping causes inversion to p-type conductivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reduced graphene oxide (RGO)/anatase TiO2 composite was prepared using a simple one-step technique—ultrasonic spray pyrolysis—in order to inhibit the aggregation of TiO2 nanoparticles and to improve ...the photocatalytic performance for degradation of methylene blue (MB). Different proportions (0–5 wt%) of RGO/TiO2 composites were characterized by scanning electronic microscopy (SEM), dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), Raman spectroscopy, UV–vis spectroscopy, and electrochemical impedance spectroscopy (EIS) to verify mechanism. From these analysis, TiO2 nanoparticles are distributed uniformly on the RGO sheets with crumpled shape during ultrasonic spray pyrolysis and surface area is increasing by increasing portion of RGO. Band gap of RGO5/TiO2 (5 wt% of RGO) composite is 2.72 eV and band gap was reduced by increasing portion of RGO in RGO/TiO2 composites. The RGO5/TiO2 composite was superior to other lower content of RGO/TiO2 composites with a rapid transport of charge carriers and an effective charge separation. The highest removal efficiency of MB was obtained at the RGO5/TiO2 composite under UVC irradiation, which coincided with the EIS, and the optimal dose of the composite was determined to be 0.5 g/L. The RGO5/TiO2 composite improve the photocatalytic degradation rate of MB over the TiO2 due to a retardation of electron-hole recombination. The MB adsorption capacity and photocatalytic degradation efficiency were greatly affected by pH changes and increased with increasing pH due to electrostatic interactions and generation of more hydroxyl radicals. The reusability of RGO5/TiO2 composite was examined during 3 cycles.
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•RGO/TiO2 composite was successfully prepared by one-pot ultrasonic spray pyrolysis.•The highest MB removal efficiency was obtained at the proportion of 5 wt% RGO.•The MB adsorption capacity of RGO5/TiO2 was enhanced at high solution pH.•RGO/TiO2 composite retarded electron-hole recombination verified with EIS.•RGO/TiO2 composite had reduced Ebg and improved the photocatalytic MB degradation.
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Cu2ZnSnS4 (CZTS) occurs in nature and is the most likely alternative to Cu(In,Ga)Se2 (CIGS) thin film solar cells, which started to spread increasingly all over the world. CZTS is a very suitable ...absorber layer material for thin film solar cells due to containing cheap material. It has a 1.5 eV band gap that is appropriate for theoretical Shockley-Queisser limit values, and the large absorption coefficient (104 cm−1). Substitution of different metals and usage of low cost and easy controlled deposition systems may present advantages.
Cu2CdSnS4 (CCTS) is a semiconductor with a band gap of 1.37 eV, and it has a large absorption coefficient over 104 cm−1 that makes it a possible photovoltaic material. Its structure is similar to CZTS. In this study, Cu2CdSnS4 thin films were deposited by ultrasonic spray method at various substrate temperatures as an alternative absorber layer. The structural features of the thin films were determined by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) surface morphology by Scanning Electron Microscopy (SEM) and optical band gaps by UV-VIS-NIR data. A CCTS-based solar cell with 1.14% power conversion efficiency was obtained using the most appropriate thin film according to optical and structural properties.
•Cu2CdSnS4 thin films were deposited using ultrasonic spray pyrolysis and annealed in H2S/Ar atmosphere.•The influence of substrate temperature on properties of the films were examined.•A solar cell with 1.14% efficiency was obtained.
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Compared with Mn(0.5)/TiO2, more bidentate nitrates were easily transformed to monodentate nitrates and then to NO2 on Fe(0.05)-Mn(0.5)/TiO2, which promoted the formation of NH4+ species.
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A series of Mn/TiO2 catalysts were prepared by ultrasonic spray pyrolysis (USP) method for selective catalytic reduction (SCR) of NOx from flue gas at low temperatures. The highest activity of Mn/TiO2 was obtained with a Mn/Ti ratio of 0.5. When Fe was doped into Mn(0.5)/TiO2, the NOx conversion rate on Fe(0.05)-Mn(0.5)/TiO2 was increased by approximately 10 % at 120–180 °C. The samples were characterized by XRD, SEM, H2-TPR, and N2 adsorption analyses. Results revealed that Mn(0.5)/TiO2 with Mn/Ti ratio of 0.5 presented the lowest crystallinity, the highest surface area, and the highest redox ability. Although the surface area was significantly decreased by Fe doping, it also reduced the crystallinity and crystal size of the catalysts, thereby increasing the O concentration on the surface of catalyst. Moreover, Fe(0.05)-Mn(0.5)/TiO2 displayed a higher redox ability than the other catalysts. At 120–240 °C, the activation energy decreased from 27.65 kJ/mol on Mn(0.5)/TiO2 to 14.46 kJ/mol on Fe(0.05)-Mn(0.5)/TiO2, thereby facilitating the activation of the reaction on Fe(0.05)-Mn(0.5)/TiO2. Despite that the NO and NH3 adsorptions were lower on Fe(0.05)-Mn(0.5)/TiO2 than on Mn(0.5)/TiO2, the intermediates on Fe(0.05)-Mn(0.5)/TiO2, particularly nitrates, were easily activated to participate in the reaction, leading to increasing catalytic activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, we report a facile and green chemistry technique to produce ZnO nanorods decorated with carbon nanodots (C-dots) to yield good photocatalytic for degradation of methyl blue. C-dots ...dispersed solution was obtained via simple carbonization of cassava peels at low temperature followed by ageing process for 6 days in absolute ethanol. The ZnO/C-dots heterostructure has been prepared by spin-coating C-dots dispersed solution onto ZnO nanorods surface. The impact of doping metal such as Co and Mn and the attachment of C-dots nanoparticles onto the surface of ZnO nanorods on their morphology, optical properties and photocatalytic activity were examined. The experimental results reveal that C-dots have successfully been attached onto the surface ZnO nanorods through strong physical interaction between C-dots and ZnO without modifying the morphology, surface area and crystallinity of ZnO nanorods. However, the energy bandgap of ZnO slightly decreases. This condition turns into increasing the charge separation efficiency of its electron-hole pairs which significantly enhances the visible light photocatalytic activity of the sample. The photodegradation rate of methyl blue was found to depend on the number of layers of C-dots. The Co doped ZnO nanorods coated with 4 layers C-dots particles was found to effectively degrade methyl blue solution compared to pristine ZnO nanorods. It is believed that high photocatalytic activity of metal doped ZnO/C-dots nanocomposite under UV light irradiation originates from their outstanding unique properties and the stimulated separation of photogenerated electron-hole pairs based on C-dots.
•Simple carbonization of cassava peels at low temperature without any oxidizing agent or addition of any toxic substances.•The ZnO/C-dots heterostructure prepared via facile spin-coating technique.•All ZnO samples are utilized as photocatalysts to degrade methyl blue solution .•The Co doped ZnO nanorods coated with 4-layer C-dots particles was found to effectively degrade methyl blue solution compared to pristine ZnO nanorods.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Iron doped ZnO films were produced by an effective ultrasonic spray pyrolysis method.•3 % Fe doping improved the crystal structure compared to lower doping ratios.•Iron doping and thermal treatment ...altered the granular morphology of ZnO.•Fe3+ and Fe2+ substitutions transformed to only Fe2+ after thermal treatment.•Thermal treatment clearly improved photocatalytic activity of 1 % Fe doped ZnO.
Zinc Oxide and Fe-doped ZnO films (1, 2, 3 %) were deposited onto glass substrates by ultrasonic spray pyrolysis. Then, the films were thermally treated at 500 °C for 2 h. Findings revealed that both Fe doping and thermal treatment changed film properties. Films presented hexagonal wurtzite structures without any secondary phases for all films. The preferential orientation (002) changed to dominant growth directions (100) and (002) according to the doping concentration and thermal treatment. The grain size of the ZnO nanogranules decreased after Fe doping and also thermal treatment. The optical transparency was found maximum of 77 % in the visible region. 3 % Fe doping and thermal treatment caused the reduction in the optical band gap values to 3.18 eV. Fourier transform infrared spectroscopy analysis presented the Z-O stretching, CH vibration, and OH stretching bonds. Shifting in the peak position indicated the Fe+2 ion substitution. Photoluminescence analyses revealed the reduced emission intensity with the effect of thermal treatment. Photocatalytic performance tests showed improved degradation efficiency after the films were thermally treated. Especially among Fe-doped films, thermally treated 1 % Fe-doped ZnO film showed a significant increment after as-deposited ones. Consequently, it has been uncovered that thermal treatment and Fe doping significantly influence the investigated film properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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The hollow NiCo2O4 nano-spheres (∼300–500nm) are synthesized by ultrasonic spray pyrolysis method and used as electrode for high-performance supercapacitor (SC) and lithium-ion ...battery (LIB). When used in SC application, the hollow NiCo2O4 deliver a specific capacitance of ∼1000Fg−1 even after 3000 charge–discharge cycles. In addition, as an anode material for LIBs, it exhibits admirable high capacity values of 763 and 516mAhg−1 after 1000 cycles at a current density of 1500 and 3000mAhg−1, respectively. The excellent electrochemical performance of this hollow NiCo2O4 nano-sphere indicates its potential applications for next generation SCs and LIBs.
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•Ag-supported ZnO particles were generated using the spray pyrolysis method.•Ag/ZnO particles with high efficiency showed twice the photolysis activity of P25.•The generated particles ...were recovered by gravity sedimentation and reused.•Change of Ag nanoparticles was not observed after the photolysis experiment.
Environmental issues caused by the rapid industrialization and urbanization of modern society are a serious problem. For example, conventional wastewater treatment technologies such as adsorption, coagulation, and filtration are expensive and cannot completely treat the discharge of organic pollutants in industrial wastewater. A promising alternative is the decomposition treatment of organic pollutants using an eco-friendly metal oxide photocatalyst. However, the rapid recombination of excited electron-holes limits the photolytic activity of semiconductor photocatalysts. This study investigates the inhibition of electron-hole recombination by supporting Ag nanoparticles on a ZnO photocatalyst. Ag/ZnO particles are generated under various conditions using ultrasonic spray pyrolysis. XRD analysis confirms the presence of Ag and ZnO crystal peaks in the generated particles. EDX mapping and STEM images show that Ag nanoparticles are well dispersed in ZnO. The photolysis rate of organic dye (rhodamine-B) is faster than that of ZnO in all Ag/ZnO particles, and particles with a 0.2 mass% silver nitrate supported on ZnO particles exhibit twice the photolysis activity of P25. Additionally, the optimal photolysis activity in 100 mL of 5 mg/L rhodamine-B aqueous solution with 10 mg of Ag/ZnO particles are confirmed and had excellent persistence and stability even during 7 reuses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Designing heterostructure materials at the nanoscale is a well-known method to enhance gas sensing performance. In this study, a mixed solution of zinc chloride and tin (II) chloride dihydrate, ...dissolved in ethanol solvent, was used as the initial precursor for depositing the sensing layer on alumina substrates using the ultrasonic spray pyrolysis (USP) method. Several ZnO/SnO2 heterostructures were grown by applying different ratios in the initial precursors. These heterostructures were used as active materials for the sensing of H2S gas molecules. The results revealed that an increase in the zinc chloride in the USP precursor alters the H2S sensitivity of the sensor. The optimal working temperature was found to be 450 °C. The sensor, containing 5:1 (ZnCl2: SnCl2·2H2O) ratio in the USP precursor, demonstrates a higher response than the pure SnO2 (∼95 times) sample and other heterostructures. Later, the selectivity of the ZnO/SnO2 heterostructures toward 5 ppm NO2, 200 ppm methanol, and 100 ppm of CH4, acetone, and ethanol was also examined. The gas sensing mechanism of the ZnO/SnO2 was analyzed and the remarkably enhanced gas-sensing performance was mainly attributed to the heterostructure formation between ZnO and SnO2. The synthesized materials were also analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and X-ray photoelectron spectra to investigate the material distribution, grain size, and material quality of ZnO/SnO2 heterostructures.
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