Unusual enhancement in electrical conductivity of tin oxide thin films with zinc doping

Electrical conductivity of SnO(2)-based oxides is of great importance for their application as transparent conducting oxides (TCO) and gas sensors. In this paper, for the first time, an unusual enhancement in electrical conductivity was observed for SnO(2) films upon zinc doping. Films with Zn/(Zn + Sn) reaching 0.48 were grown by pulsed spray-evaporation chemical vapor deposition. X-Ray diffraction (XRD) shows that pure and zinc-doped SnO(2) films grow in the tetragonal rutile-type structure. Within the low doping concentration range, Zn leads to a significant decrease of the crystallite size and electrical resistivity. Increasing Zn doping concentration above Zn/(Zn + Sn) = 0.12 leads to an XRD-amorphous film with electrical resistivity below 0.015 ? cm at room temperature. Optical measurements show transparencies above 80% in the visible spectral range for all films, and doping was shown to be efficient for the band gap tuning.     

Enhanced photocatalytic activities of ZnO thin films: a comparative study of hybrid semiconductor nanomaterials

Nanostructure single ZnO, SnO₂, In₂O₃ and composite ZnO/SnO₂, ZnO/In₂O₃ and ZnO/SnO₂/In₂O₃ films were prepared using sol?Cgel method. The obtained composite films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV?CVis spectroscopy. The photocatalytic activities of composite films were investigated using phenol (P), 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) and 4-aminophenol (4-AP) as a model organic compounds under UV light irradiation. Hybrid semiconductor thin films showed a higher photocatalytic activity than single component ZnO, SnO₂ and In₂O₃ films. The substituted phenols degrade faster than phenol. The ease of degradation of phenols is different for each catalyst and the order of catalytic efficiency is also different for each phenol. The use of multiple components offered a higher control of their properties by varying the composition of the materials and related parameters such as morphology and interface. It was also found that the photocatalytic degradation of phenolic compounds on the composite films and single films followed pseudo-first order kinetics.     

Enhanced photocatalytic activity of thin TiO2 films dotted with ZnS nanoparticles

The effect of Ni loading on the catalytic activity of Ni/ZrO₂ catalyst for methane steam reforming was investigated. The sample containing 15 wt.% Ni exhibited the highest activity as well as stability at 600°C. An erratum to this article is available at .     

Increased photocatalytic activity caused by B doping into BiVO4

Research on Chemical Intermediates - We have prepared B-doped BiVO4 (B-BiVO4) with oval-shaped morphology through a simple, one-step hydrothermal route employing sodium citrate as the chelating...     

The effects of cerium doping concentration on the properties and photocatalytic activity of bimetallic Mo/Ce catalyst

In this study, the characterization and photocatalytic activity of MoO₃ nanoparticles doped with various doping concentrations of cerium have been investigated. The Fourier transform infrared (FT-IR) spectra of the prepared catalysts confirmed that MoO₃ particles have been successfully doped by cerium. Field emission scanning electron microscopy (FESEM) was performed to visualize the surface morphology of the obtained catalysts. The XRD patterns suggested that the crystallinity of the sample with the lowest doping concentration of 15 mol % was higher in comparison with samples of higher doping concentrations. The volume-averaged crystal sizes of the obtained catalysts were calculated to be 25, 28, and 32 nm for 15, 35, and 60 mol % samples, respectively. The photocatalytic activity along with the reaction kinetics of Ce-doped MoO₃ nanoparticles have also been investigated through the dye degradation of methyl orange. The synthesized Ce-doped MoO₃ particles with the lowest dopant concentration of 15 mol % exhibited the highest photocatalytic activity for methyl orange dye degradation. It was observed that photo-degradation activity decreased with an increase in the doping concentration of cerium. The predicted rate constants for samples with 15, 35, and 60 mol % doping concentrations were found to be 0.0432, 0.035, and 0.029 min^–1, respectively.     

Modification of photocatalytic TiO2 thin films by electron beam irradiation

Noble metal-modified TiO₂ films were prepared by electron beam deposition of Pt, Pd, Au and Ag on the surface of TiO₂ films with diameters ranging from <1 nm to 500 nm. The morphology of the films was characterized by X-ray diffractometry (XRD), field emission scanning electron microscope (FMSEM) and transmission electron microscope (TEM). The photocatalytic capability of the films were tested and compared by degradation of methyl orange (MO) in aqueous solutions under both UV and visible light illumination.     

Great enhancement of photocatalytic activity of nitrogen-doped titania by coupling with tungsten oxide

The TiO2-N-x%WO3 composite photocatalysts were prepared by introducing WO3 into nitrogen-doped TiO2. The composite catalysts present much higher photocatalytic activity than TiO2 and nitrogen-doped TiO2 under both ultraviolet and visible light irradiation. Diffuse reflectance UV-vis spectra, XPS analysis, and IR spectra show that the coordinated nitrogen species (or N-metal-O linkages) may contribute to the visible light photocatalytic activity. WO3 coupling increases the active nitrogen species and thus enhances the visible light activity of the composite photocatalysts. The superior activity of TiO2-N-x%WO3 composite photocatalysts upon UV light irradiation can be rationalized in terms of efficient charge separation and high adsorption affinity of WO3.     

Synthesis and characterization of Mn:CdS nanoflower thin films prepared by hydrothermal method for photocatalytic activity

Journal of Sol-Gel Science and Technology - Mn-CdS nanoflowers were successfully deposited using hydrothermal technique at 150 °C for 2 h. The effect of changing the dopant...     

The improvement of solar photocatalytic activity of ZnO by doping with Er3+:Y3Al5O12 during dye degradation

The Er³⁺:Y₃Al₅O₁₂, an upconversion luminescence agent, which is able to transform the visible light to ultraviolet light, was synthesized by nitrate-citric acid method. And then, a novel photocatalyst, Er³⁺:Y₃Al₅O₁₂/ZnO composites, was prepared by ultrasonic dispersing and liquid boil method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structural morphology and surface properties of the Er³⁺:Y₃Al₅O₁₂/ZnO. Azo Fuchsine dye was selected as target organic pollutant to inspect the photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/ZnO. The key parameters affecting the photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/ZnO, such as Er³⁺:Y₃Al₅O₁₂ content, heat-treatment temperature and heat-treatment time, were studied. In addition, the effects of dye initial concentration, Er³⁺:Y₃Al₅O₁₂/ZnO amount and solar light irradiation time were also reviewed, as well as the photocatalytic activity in degradation of other organic dyes were compared. It was found that the photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/ZnO was much superior to pure ZnO under the same conditions. Thus, the Er³⁺:Y₃Al₅O₁₂/ZnO is a useful photocatalyst for the wastewater treatment because it can efficiently utilize solar light by converting visible light into ultraviolet light.     

Raman study of oriented ZnO thin films deposited by sol-gel method

ZnO films with preferred orientation along the (0 0 2) plane were successfully deposited by the sol-gel method using Zn(CH3COO)2.2H2O as starting material and inorganic precursor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. Thin films are obtained by spin-coating on glass substrates. ZnO films were obtained by preheating the spin-coated films at 300 degrees C for 10 min after each coating and postheating upto 550 degrees C for 2h. The as-deposited films are transformed into mono-oriented ZnO upon thermal treatment. The films consist of spongy particles aggregates with an uniform size and homogenous surface. The films aim to be used in optoelectronic devices. Raman spectroscopy from ZnO films and deposit solutions has been investigated. New Raman results of the deposit solution suggest that Zn-O bond forms first in solution and that these entities play the role of germs initiating the crystallization mechanisms during films annealing. Raman spectra of the annealed films show the presence of a compressive stress within the film structure.     

Photoinduced hydrophilicity of heteroepitaxially grown ZnO thin films

Single crystalline ZnO thin films were heteroepitaxially grown on sapphire substrates by rf-magnetron sputtering. The ZnO films on sapphire A and C face were oriented along the (0001) direction, whereas the ZnO film on sapphire R face was oriented along the (11-20) direction. The rate of photoinduced hydrophilic conversion strongly depended on the surface crystal structure. The ZnO film oriented along the (11-20) direction exhibited a higher hydrophilicizing rate than those oriented along the (0001) direction. The high hydrophilicizing rate of the ZnO oriented along the (11-20) direction is due to its surface atomic arrangement. The outermost layer of the ZnO surface of the (11-20) face contains oxygen ions, which are considered to be energetically reactive sites and responsible for the hydrophilic conversion.     

Bi3+/Ce3+ doped ZnO nanoparticles with enhanced photocatalytic and dielectric properties

In this study, varying % Bi-doped on 1% Ce-doped ZnO (1CZ) nanoparticles (X% B-1CZ) were synthesized via a facile, simple, low-cost, sol–gel process. Various characterization techniques were employed to characterize the synthesized compound, while the dielectric properties i.e. dielectric constant, dielectric loss and AC conductivity against frequency were studied with the help of a precision impedance analyzer. It was observed that by increasing bismuth content in the nanoparticles, the dielectric constant also increased in the range (1.47 × 10⁶ – 4.02 × 10⁶) at 20 Hz, and vice versa for dielectric loss decreased from 1.05 × 10⁶ to 0.39 × 10⁶. The role of prepared compounds as photocatalysts was also investigated against methylene blue under ultraviolet irradiation. The degradation efficiency, as well as the dielectric properties of 7% Bi-doped on 1% Ce-doped ZnO (7%B-1CZ), were found to be the best. Overall, it was found that the synthesized compounds proved promising candidates with enhanced photocatalytic & dielectric properties and hence could safely be employed for environmental remediation purposes and energy storage devices.     

Hybrid ZnO/polymer thin films prepared by RF magnetron sputtering

Zinc oxide/poly(acrylic acid) (ZnO/PAA) multilayered hybrid films with different layer thicknesses were prepared by radio frequency magnetron sputtering. Zinc peroxide was used as precursor materials for the preparation of ZnO layers, since the zinc peroxide decomposes to ZnO during the film deposition. The films have a high transmittance in the visible region and exhibit visible photoluminescence emission. The band gap energy of the films—determined by the Tauc relationship—decreases with increasing layer thickness (3.40–3.36 eV) due to the increasing crystalline size of the ZnO particles. The morphological investigations showed that a real layered hybrid film structure formed.     

Inhibition of the toxic byproduct during photocatalytic NO oxidation via La doping in ZnO

It is of a great challenge to develop semiconductor photocatalysts with potential possibilities to simultaneously enhance photocatalytic efficiency and inhibit generation of toxic intermediates.In this study,we developed a facile method to induce the La doping and cationic vacancie(V(Zn))on ZnO for the highly efficient complete NO oxidation.The photocatalytic NO removal efficiency increases from 36.2%to 53,6%.Most importantly,a significant suppressed NO2 production also has been realized.According to the DFT calculations,ESR spectra and in situ FTIR spectra,the introduction of La^3+induce the redistribution of charge carriers in La-ZnO,which promote the production of·O2^- and lead to the formation of V(Zn)for the formation of·OH,contributing to the complete oxidation of NO to nitrate.Besides,the conversion pathway of photocatalytic NO oxidation has been elaborated,This work paves a new way to simultaneously realize the photocatalytic pollutants removal and the inhibition of toxic intermediates generation for efficient and safe air purification.     

Enhancement of the photocatalytic activity of TiO(2) by doping it with calcium ions

Titanium dioxide (TiO(2)) with an enhanced photocatalytic activity was developed by doping it with calcium ions through a sol-gel method. The developed photocatalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, N(2) physisorption, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction. Their surface morphologies were studied using surface scanning electron microscopy (SEM). The XPS analyses confirmed the presence of Ti, O, Ca, and C in the Ca-doped TiO(2) sample. The activities of the catalysts were evaluated by photocatalytic degradation of an azo dye, acid red 1 (AR1), using UV light irradiation. The results of the investigations revealed that the samples calcined at 300 °C for 3.6h in a cyclic (2 cycles) mode had the best performance. Lower percentage dopant, 0.3-1.0 wt.%, enhanced the photocatalytic activity of TiO(2), with the best at 0.5 wt.% Ca-TiO(2). The performance of 0.5 wt.% Ca-TiO(2) in the degradation of AR1 was far superior to that of a commercial anatase TiO(2) Sigma product CAS No. 1317-70-0. The effect of pH on the degradation of AR1 was studied, and the pH of the dye solution exerted a great influence on the degradation of the dye.