Microwave-assisted method for preparation of Zn1−xMgxO nanostructures and their activities for photodegradation of methylene blue

Synthesis of β-Ga2O3:Mg Thin Films by Electron Beam Evaporation and Postannealing

Doping divalent metal cations into Ga2O3 films plays a key role in adjusting the conductive behavior of the film. N-type high-resistivity β-Ga2O3:Mg films were prepared using electron beam evaporation and subsequent postannealing processing. Various characterization methods (X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, etc.) revealed that the Mg content plays an important role in affecting the film quality. Specifically, when the Mg content in the film is 3.6%, the S2 film's resistivity, carrier content, and carrier mobility are 59655.5 Ω·cm, 1.95 × 1014 cm3/C, and 0.53682 cm2/Vs. Also, the film exhibits a smoother surface, more refined grains, and higher self-trapped exciton emission efficiency. The Mg cation mainly substitutes the Ga+ cation at a tetrahedral site, acting as a trap for self-trapped holes.

Sulfur deficiency mediated visible emission of ZnS QDs by magnesium dopant and their application in waste water treatment

The photocatalyst with antimicrobial activity serves as a better candidate material for wastewater treatment, as wastewater contains microbes, hazardous dyes, and heavy metals. Hence, the present study extensively examines the photocatalytic and antibacterial activities against two waterborne bacterial strains, namely Salmonella typhi and Escherichia coli. Pure and Mg-doped ZnS (Mg:ZnS) quantum dots (QDs) were synthesized using a low-cost and simple co-precipitation method. The QDs' structural, surface morphology, chemical purity, and optical characteristics were analyzed through XRD, SEM, EDAX, TEM, UV-visible, and photoluminescence spectra. The incorporation of Mg dopants did not introduce significant alterations to the cubic blende structure of ZnS, nor did it induce substantial changes in the structural parameters. However, the QDs exhibited a slight sulfur deficiency, which was further increased by the presence of Mg dopant. The Mg dopant, due to its dominant compositional effect, reduced the band gap. Several optical emission bands were observed in the UV, violet, blue, and green regions, corresponding to NBE emission, sulfur-related defects, and Zn-related defects. Initially, Mg doping enhanced visible emission related to defects, while NBE emission was suppressed by the Mg dopant. However, increasing the concentration of the Mg dopant led to a slight increase in NBE emission. The Mg dopant enhanced the photocatalytic activity of the QDs, and a strong correlation was found between photocatalytic activity and NBE emission. The presence of the Mg dopant led to an increased rate of ROS-based decolorization by reducing the electron-hole recombination rate.

Efficient photocatalytic degradation of malachite green dye using facilely synthesized hematite nanoparticles from Egyptian insecticide cans

In the present study, a combustion method was applied for the production of hematite nanoparticles from Egyptian iron waste using l-arginine (The sample was named HA) and glutamine (The sample was named HG) as organic fuels, respectively. XRD confirmed that the HA and HG products have crystallite sizes of 48 and 56 nm, respectively. Also, HR-TEM demonstrated that spherical and irregular shapes have an average diameter of 45 and 59  nm were observed in the HA and HG samples, respectively. Besides, FE-SEM elucidated that spherical and irregular shapes have an average size of 142 and 196 nm were observed in the HA and HG samples, respectively. In addition, FT-IR confirmed that the peaks which were detected at 518 and 430 cm^-1 are because of vibrations of Fe-O bond. Moreover, the value of the energy gap for the HA and HG samples was 1.00 and 1.45 eV, respectively. Furthermore, the PL emission spectra elucidated that the emission intensity of the HA sample was less than that of the HG sample. So, e^-/h⁺ recombination rate of the HA sample was less than that of the HG sample. Hence, the photocatalytic degradation of malachite green dye using the HA sample was larger than that using the HG sample. In the absence of H₂O₂, the % degradation of malachite green dye under the influence of UV using HA and HG samples was 46.29 and 39.72 % after 3 h, respectively. Also, in the presence of H₂O₂, the % degradation of malachite green dye under the influence of UV using HA and HG samples was 100 % after 60 and 70 min, respectively.

Bioinspired catecholamine/starch composites as superadsorbent for the environmental remediation

Focusing on the encouraging properties of starch-based composite materials, starch‑g‑(acrylic acid‑co‑acrylamide) superabsorbent was synthesized using solution polymerization method, and then the catecholamine functional groups were introduced on to pore surface of the absorbent via oxidative polymerization of dopamine (DA). The adsorbent was optimized in terms of the monomers' mass ratio and synthesis conditions, and characterized by different characterization techniques. The polydopamine (PDA) coating thickness was estimated using transmission electron microscopy (TEM) image and it was found to be 83 nm. The bimodal mesoporous adsorbent with 5914.66% swelling ratio bearing micropores with a specific surface area of 2.8031 m² g^-1 was used for the adsorption of methylene blue (MB) as a model water pollutant dye. The maximum adsorption capacity was obtained 2276 mg g^-1 at pH 9 and within 100 min. The adsorbent with unprecedented super high adsorption capacity can be encouraging from different environmental remediation points of view.

Novel g-C3N4/Ag2SO4 nanocomposites: Fast microwave-assisted preparation and enhanced photocatalytic performance towards degradation of organic pollutants under visible light

Graphite carbon nitride (g-C3N4)/Ag2SO4 nanocomposites, as highly enhanced visible-light-driven photocatalysts, were prepared by a fast microwave-assisted method. The resulting g-C3N4/Ag2SO4 nanocomposites were characterized by X-ray diffraction, energy dispersive analysis of X-rays, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform-infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy techniques. Moreover, charge separation efficiency was studied by photoluminescence measurements. Photocatalytic activity of the g-C3N4/Ag2SO4 (40%) nanocomposite in degradation of rhodamine B, methylene blue, and fuchsine is about 6, 3.8, and 3.3-folds greater than that of the g-C3N4 under visible-light illumination. Effect of microwave irradiation time, calcination temperature, and scavengers of the reactive species on the degradation reaction was also evaluated. The enhanced photocatalytic activity was mainly ascribed to the matching band energies of g-C3N4 and Ag2SO4 which leads to an improved separation of photogenerated electron-hole pairs. Finally, the optimized nanocomposite was recycled for five times without remarkable decrease of the photocatalytic activity.