A high sensitivity dual-mode optical thermometry based on charge compensation in ZnTiO3:M (M = Eu3+, Mn4+) hexagonal prisms

Enhancing Methylene Blue Removal through Adsorption and Photocatalysis-A Study on the GO/ZnTiO3/TiO2 Composite

This study focuses on synthesizing and characterizing a graphene oxide/ZnTiO3/TiO2 (GO/ZTO/TO) composite to efficiently remove methylene blue (MB) from water, presenting a novel solution to address industrial dye pollution. GO and ZTO/TO were synthesized by the modified Hummers and sol-gel methods, respectively, while GO/ZTO/TO was prepared using a hydrothermal process. The structural and surface properties of the composite were characterized using various analytical techniques confirming the integration of the constituent materials and suitability for dye adsorption. The study revealed that GO/ZTO/TO exhibits an adsorption capacity of 78 mg g-1 for MB, with only a 15% reduction in adsorption efficiency until the fifth reuse cycle. Furthermore, the study suggests optimal adsorption near neutral pH and enhanced performance at elevated temperatures, indicating an endothermic reaction. The adsorption behavior fits the Langmuir isotherm, implying monolayer adsorption on homogeneous surfaces, and follows pseudo-second-order kinetics, highlighting chemical interactions at the surface as the rate-limiting step. The photocatalytic degradation of MB by GO/ZTO/TO follows pseudo-first-order kinetics, with a higher rate constant than that of GO alone, demonstrating the enhanced photocatalytic activity of the composite. In conclusion, GO/ZTO/TO emerges as a promising and sustainable approach for water purification, through an adsorption process and subsequent photocatalytic degradation.

Dual-mode optical thermometer based on fluorescence intensity ratio of Eu3+/Mn4+ co-doping zinc titanate phosphors

Zinc titanate phosphors containing Eu³⁺/ Mn⁴⁺ as active ions were synthesized by using the solid-state method. XRD patterns of the powders confirmed that the samples were a mixture of cubic Zn₂TiO₄ and hexagonal ZnTiO₃ phases. The luminous intensity of ZTO: Eu³⁺phosphors and ZTO: Mn⁴⁺ phosphors both increased with the increase of doping concentration, reaching the maximum at 2 mol% Eu³⁺ and 0.3 mol% Mn⁴⁺, respectively. In the photoluminescence spectra of ZTO: Eu³⁺(2 mol%) phosphors with different Mn⁴⁺ doping amounts excited at 465 nm, the emission spectra revealed the characteristic peaks of Eu³⁺ with low Mn⁴⁺ content, and with the Mn⁴⁺ content increasing, the emission spectra contained both Mn⁴⁺ and Eu³⁺ luminescence peaks. In the variable temperature spectra, the relative sensitivity of the samples was improved with the concentration of Mn⁴⁺ increasing and achieved the maximum value of 3.2 %/K.

Comparative Study of the Effect of Doping ZnTiO3 with Rare Earths (La and Ce) on the Adsorption and Photodegradation of Cyanide in Aqueous Systems

Cyanide is a highly toxic compound that can pose serious health problems to both humans and aquatic organisms. Therefore, the present comparative study focuses on the removal of total cyanide from aqueous solutions by photocatalytic adsorption and degradation methods using ZnTiO₃ (ZTO), La/ZnTiO₃ (La/ZTO), and Ce/ZnTiO₃ (Ce/ZTO). The nanoparticles were synthesized by the sol-gel method and characterized by X-ray powder diffractometry (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), Diffuse reflectance spectroscopy (DRS), and Specific surface area (SSA). The adsorption equilibrium data were fitted to the Langmuir and Freundlich isotherm models. Adsorption kinetics were also evaluated using the pseudo-first-order and pseudo-second-order models and the intraparticle diffusion model. Likewise, the photodegradation of cyanide under simulated sunlight was investigated and the reusability of the synthesized nanoparticles for cyanide removal in aqueous systems was determined. The results demonstrated the effectiveness of doping with lanthanum (La) and cerium (Ce) to improve the adsorbent and photocatalytic properties of ZTO. In general, La/ZTO showed the maximum percentage of total cyanide removal (99.0%) followed by Ce/ZTO (97.0%) and ZTO (93.6%). Finally, based on the evidence of this study, a mechanism for the removal of total cyanide from aqueous solutions using the synthesized nanoparticles was proposed.

Efficient dual mode emission in Ce3+/Yb3+/Er3+ doped yttrium aluminium gallium garnet for led device and optical thermometry

By utilizing the effective energy transfer from Ce³⁺ to Yb³⁺, Er³⁺ and from Yb³⁺ to Er³⁺ authors have achieved dual mode emission in Y₃Al₄GaO₁₂ activated with Ce³⁺/Yb³⁺/Er³⁺ ions. Surface morphological and elemental compositions of the prepared samples have been examined using field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS) analysis, respectively. The chemical state of the dopant ions is confirmed by the X-ray photoelectron spectroscopy (XPS). On excitation with 438 nm the prepared material has shown broad visible emission band around 511 nm due to the electronic transition of Ce³⁺ ion. In addition to this sample has also shown NIR emission bands centered around 1024 nm and 1480 nm from Yb³⁺ and Er³⁺ ions, respectively. The emission band at 1024 nm could be due to the quantum cutting (QC) process. Furthermore, up-conversion (UC) emission against temperature and laser power variations is studied on 980 nm excitation wavelength. The prepared sample is used to fabricate visible and NIR LED devices by coating of sample on blue LED chip. Along with this demonstration, optical thermometry ability of the material is studied using emission intensity ratio of two emitting levels. Studies suggest that the prepared material could be useful as dual mode emitting phosphor and LED.

The Effect of La3+ on the Methylene Blue Dye Removal Capacity of the La/ZnTiO3 Photocatalyst, a DFT Study

Theoretically, lanthanum can bond with surface oxygens of ZnTiO3 to form La-O-Ti bonds, resulting in the change of both the band structure and the electron state of the surface. To verify this statement, DFT calculations were performed using a model with a dispersed lanthanum atom on the surface (101) of ZnTiO3. The negative heat segmentation values obtained suggest that the incorporation of La on the surface of ZnTiO3 is thermodynamically stable. The bandgap energy value of La/ZnTiO3 (2.92 eV) was lower than that of ZnTiO3 (3.16 eV). TDOS showed that the conduction band (CB) and the valence band (VB) energy levels of La/ZnTiO3 are denser than those of ZnTiO3 due to the participation of hybrid levels composed mainly of O2p and La5d orbitals. From the PDOSs, Bader's charge analysis, and ELF function, it was established that the La-O bond is polar covalent. MB adsorption on La/ZnTiO3 (-200 kJ/mol) was more favorable than on ZnTiO3 (-85 kJ/mol). From the evidence of this study, it is proposed that the MB molecule first is adsorbed on the surface of La/ZnTiO3, and then the electrons in the VB of La/ZnTiO3 are photoexcited to hybrid levels, and finally, the MB molecule oxidizes into smaller molecules.