Novel PWO/ ZnO heterostructured nanocomposites: Synthesis, characterization, and photocatalytic performance

Photocatalytic degradation is becoming an increasingly attractive method for addressing environmental remediation challenges. In this work, the novel pure PWO/ZnO and doped PWO: Er/ZnO: Ag heterostructure nanocomposites with premier photocatalytic efficiency were synthesized via a simple co-precipitation method followed by a solvothermal procedure. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX), and ultraviolet-visible (UV-Vis) absorbance measurements techniques were employed to characterize the structural and optical properties. HRTEM images prove the possibility of intimate contact formation at the pure and doped PWO/ZnO heterostructure nanocomposite interfaces. The photocatalytic performance of the PWO/ZnO heterostructure nanocomposites in the degradation of the methylene blue (MB) and methyl orange (MO) dyes under UVA light was evaluated. The photocatalysts' ability in the mineralization of organic pollutants was confirmed by the TOC test. BET and zeta potential analyses were used to study the dye adsorption mechanisms. Additionally, adsorption isotherms and kinetics have been investigated to describe the adsorption of MB and MO into the samples. The degradation rates of MB with PWO/ZnO and PWO: Er/ZnO: Ag heterostructure nanocomposites were 4.7 and 6.6 times higher than those of PWO and PWO: Er nanoparticles. This rate for MO degradation is 5.2 and 3.5 times higher than that of pure PWO and PWO: Er nanoparticles, respectively. This study outlines an easy method to develop innovative, highly effective heterostructure nanocomposites capable of converting UVA light into photocatalytic performance.

Investigation on optical band gap, photoluminescence properties and concentration quenching mechanism of Pb1-x Tb3+xWO4 green-emitting phosphors

A series of monophasic Tb³⁺ (2, 5, 7, 10 and 15at%) doped PbWO₄ phosphors were successfully prepared via hydrothermal method. X-ray diffraction patterns revealed that the prepared samples possess a high crystallinity with tetragonal scheelite-type structure. FT-IR and Raman analysis exhibited a WO stretching peak of WO₄^2- group, which is also related to the scheelite structure. UV-visible diffuse reflectance spectra indicated a reduction in the optical band gap with the replacement of Pb²⁺ by Tb³⁺ ions. The presence of strong and intense emission peaks characteristic of Tb³⁺ with the dominant peak at 545nm (green, ⁵D₄→⁷F₅ transition) under UV irradiation at 320nm demonstrated an efficient energy transfer from the host to Tb³⁺ ions. Using Van Uitert's model, the concentration quenching mechanism between Tb³⁺ ions in PbWO₄:Tb³⁺ phosphor was attributed to a dipole-dipole interaction and the critical distance was determined to be ~12Å. The decay lifetimes and CIE chromaticity co-ordinates of PbWO₄:Tb³⁺ phosphors were also investigated in detail. These prepared materials might serve as a potential phosphor for LED applications.

Nitrate-assisted photocatalytic efficiency of defective Eu-doped Pr(OH)3 nanostructures

Pr(OH)₃ one-dimensional nanostructures are a less studied member of lanthanide hydroxide nanostructures, which recently demonstrated an excellent adsorption capacity for organic pollutant removal from wastewater. In this study, Pr_1-xEu_x(OH)₃ (x = 0, 0.01, 0.03, and 0.05) defective nanostructures were synthesized by a facile and scalable microwave-assisted hydrothermal method using KOH as an alkaline metal precursor. The phase and surface composition, morphology, vibrational, electronic and optical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Raman, infrared (IR), photoluminescence (PL), and diffuse reflectance spectroscopy (DRS). It was deduced that the incorporation of Eu³⁺ ions promoted the formation of oxygen vacancies in the already defective Pr(OH)₃, subsequently changing the Pr(OH)₃ nanorod morphology. The presence of KNO₃ phase was registered in the Eu-doped samples. The oxygen-deficient Eu-doped Pr(OH)₃ nanostructures displayed an improved photocatalytic activity in the removal of reactive orange (RO16) dye under UV-vis light irradiation. An enhanced photocatalytic activity of the Eu-doped Pr(OH)₃ nanostructures was caused by the synergetic effect of oxygen vacancies and Eu³⁺ (NO₃^-) ions present on the Pr(OH)₃ surface, the charge separation efficiency and the formation of the reactive radicals. In addition, the 3% Eu-doped sample exhibited very good adsorptive properties due to different morphology and higher electrostatic attraction with the anionic dye. Pr_1-xEu_x(OH)₃ nanostructures with the possibility of tuning their adsorption/photocatalytic properties present a great potential for wastewater treatment.

Tunable luminescence and enhanced photocatalytic activity for Eu(III) doped Bi2WO6 nanoparticles

A series of Eu(III) doped Bi₂WO₆ nanoparticles were synthesized by a hydrothermal process. The obtained Bi₂WO₆:Eu(III) nanoparticles were characterized by XRD, SEM, luminescence spectrophotometer and DRS. The XRD and TEM results indicate that the Eu(III) doping concentration has no influence on the phase and morphology. However, the Eu(III) doping can tune the luminescence and enhance the photocatalytic activity of Bi₂WO₆. With the increases of Eu³⁺ doping concentrations, the emission intensity of WO₆^6- group decreases nut the photocatalytic activity increases. The tunable luminescence of Bi₂WO₆:Eu(III) nanoparticles results from the energy transfer from WO₆^6- group to Eu(III) ion. The enhanced performance can be ascribed to efficient separation of electron and hole pairs after doping Eu(III) into the Bi₂WO₆ lattice.