TiO2 doped with europium (Eu): Synthesis, characterization and catalytic performance on pesticide degradation under solar irradiation

Photoluminescence modification of europium(III)-doped MAl2O4 (M = Zn, Mg) spinels induced by Ag@SiO2 core-shell nanoparticles

In recent years, there has been an increasing interest in developing new inorganic compounds with exceptional properties for advanced materials. Specifically, compounds containing europium have attracted much attention due to their luminescent properties. These compounds are used in electronics, biotechnology, medicine, and catalysis. Eu is known for its characteristic red emission, which can be influenced by the environment. This study investigates the surface-enhancement luminescence of europium-doped spinel oxides using modified surface with silver (Ag@SiO2 core-shell) nanoparticles as the enhancers. The europium-doped spinels were synthesized through a sol-gel method, and characterization techniques were used to analyze their structure and morphology. Photoluminescence spectra exhibited characteristic Eu3+ transitions, with the hypersensitive transition being the most prominent. The interaction with an Ag@SiO2 modified-surface led to a significant increase in photoluminescence. The study also analyzed the photoluminescence excitation and lifetimes of the oxides, leading to a 7.3-fold increase in photoluminescence. The improvements observed in the luminescence of these tailor-made materials show their potential interest in next-generation technologies.

Recent updates on remediation approaches of environmentally occurring pollutants using visible light-active nano-photocatalysts

Photocatalysis emerges as a potential remedy for the issue of an unreliable light source. Recognized as the most dependable and potent energy source sustaining life on Earth, sunlight offers a promising solution. Sunlight is abundant and free, operational costs associated with running photocatalytic system using nanoparticles are often lower compared to system relying on artificial light source. The escalating problem of water pollution, particularly in highly industrialized nations, necessitates effective wastewater treatment methods. These methods aim to combat elevated pollution levels, encompassing pharmaceuticals, dyes, flame retardants, and pesticide components. Advanced oxidation processes within photocatalytic wastewater treatment exhibit substantial promise for removing complex organic pollutants. Doped nanomaterials, with their enhanced properties, enable efficient utilization of light. Coupled nanomaterials present significant potential in addressing both water and energy challenges by proficiently eliminating persistent pollutants from environment. Photocatalysis when exposed to sunlight can absorb photons and generate e- h + pairs. This discussion briefly outlines the wastewater treatment facilitated by interconnected nanomaterials, emphasizing their role in water-energy nexus. In exploring the capabilities of components within a functional photocatalyst, a comprehensive analysis of both simple photocatalysts and integrated photocatalytic systems is undertaken. Review aims to provide detailed explanation of the impact of light source on photon generation and significance of solar light on reaction kinetics, considering various parameters such as catalyst dosage, pH, temperature, and types of oxidants. By shedding light on these aspects, this review seeks to enhance our understanding of intricate processes involved in photocatalysis and its potential applications in addressing contemporary environmental challenges.

Label-free photoelectrochemical immunosensing of α-fetoprotein based on Eu-TiO2 nanocomposites sensitized with dye-encapsulated HMA

In this study, a sensitive photoelectrochemical immunosensor with dye-enhanced anodic photocurrent response was proposed for sensitive detection of α-fetoprotein (AFP). Specifically, europium-doped TiO₂ (Eu-TiO₂) was used as the photoelectrochemical functional material and coated onto indium tin oxide (ITO) electrode. Doxorubicin (DOX) as an excellent fluorescent dye was encapsulated in the hydrophobically modified alginate (HMA). Then the dye-loaded HMA was modified onto the surface of Eu-TiO₂ to further sensitize the photocurrent response. The results showed that the photoelectrical signal was enhanced and stabilized due to the effect of sensitization of DOX on Eu-TiO₂ material. The constructed PEC sensor revealed a good linear response to AFP antigen ranging from 0.5 to 100 ng/mL with a detection limit of 0.41 pg/mL. The clinical patient's serum test results obtained from the proposed PEC immunosensor were consistent with those obtained from the commercial electrochemilunescence assay. The proposed PEC sensing method could be a promising analytical tool for the detection of AFP in clinical analysis.

Effect of Doping TiO2 NPs with Lanthanides (La, Ce and Eu) on the Adsorption and Photodegradation of Cyanide-A Comparative Study

Free cyanide is a highly dangerous compound for health and the environment, so treatment of cyanide-contaminated water is extremely important. In the present study, TiO₂, La/TiO₂, Ce/TiO₂, and Eu/TiO₂ nanoparticles were synthesized to assess their ability to remove free cyanide from aqueous solutions. Nanoparticles synthesized through the sol-gel method were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), and specific surface area (SSA). Langmuir and Freundlich isotherm models were utilized to fit the adsorption equilibrium experimental data, and pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit the adsorption kinetics experimental data. Cyanide photodegradation and the effect of reactive oxygen species (ROS) on the photocatalytic process were investigated under simulated solar light. Finally, reuse of the nanoparticles in five consecutive treatment cycles was determined. The results showed that La/TiO₂ has the highest percentage of cyanide removal (98%), followed by Ce/TiO₂ (92%), Eu/TiO₂ (90%), and TiO₂ (88%). From these results, it is suggested that La, Ce, and Eu dopants can improve the properties of TiO₂ as well as its ability to remove cyanide species from aqueous solutions.

Solar photodegradation of Rhodamine B dye by Cu2O/TiO2 heterostructure: experimental and computational studies of degradation and toxicity

CONTEXT AND RESULTS

In this study, the heterojunction Cu₂O/TiO₂ is used for the degradation of a cationic dye, Rhodamine B, under solar light irradiation over a wide pH range. The physical and optical properties of both semiconductors Cu₂O and TiO₂ are correlated with the photo-electrochemical characterization to establish the energy diagram of the heterojunction Cu₂O/TiO₂. X-ray diffraction, UV-visible, SEM, EDX, and BET analyses are conducted for both photocatalysts. The band gap (E_g) of 3.26 eV is obtained for TiO₂ with an indirect optical transition. In the case of Cu₂O, the transition is directly allowed at 2.05 eV. According to the BET analysis, the specific surface area of TiO₂ particles is higher (82.65 m² g^-1) than that of Cu₂O (29.81 m² g^-1). The flat band potentials, determined from the Mott-Schottky plots, are 0.3 and - 0.32 V_SCE for TiO₂ and Cu₂O, respectively. The photocatalytic activity is directly proportional to the mass ratio, and the best result is obtained for the mass ratio 1:1 of Cu₂O/TiO₂.

COMPUTATIONAL AND THEORETICAL TECHNIQUES

Furthermore, a theoretical study is conducted by using density functional theory to optimize the structure, reactivity sites of the RhB molecule, and physical parameters like the energy of the frontier molecular orbitals and electronegativity and to predict the proposed mechanism of RhB degradation as well as its intermediates. Also, molecular dynamics simulation is used to determine the adsorption behavior of RhB on TiO₂ (101) and Cu₂O (111) surfaces. The ecotoxicity evaluation showed that degradation products have significantly lower acute toxicity than RhB.

Nanohybrid catalysts with porous structures for environmental remediation through photocatalytic degradation of emerging pollutants

Water supplies have been seriously challenged by new emerging pollutants, which are difficult to remove by traditional wastewater treatment. Thus, new technologies such as catalytic advanced oxidation processes have merged as suitable solutions; however, the drawbacks of typical catalysts limit their application. To overcome this issue, new materials with enhanced textural properties have been developed, showing that their porosity and chemical nature influence their potential as a catalyst. Herein, the recent progress in highly porous catalysts and their suitable deployment to effectively nano-remediate the polluted environmental matrices are reviewed in detail. First, following a brief introduction, several environmental pollutants of emerging concerns from different sectors, including pharmaceutical residues, endocrine-disrupting chemicals (EDCs), pesticides, and hazardous dyes are also introduced with relevant examples. To effectively tackle the sustainable remediation of emerging pollutants, this work also focuses on the multifunctional features of nanohybrid porous materials that act as catalysts constructs to degrade emerging pollutants. The influence of surface reactive centers, stability, bandgap energies, light absorption capacities, and pollutants adsorption capacities are also discussed. Successful examples of the employment of nanohybrid porous catalysts for the degradation of pharmaceutical pollutants, EDCs, pesticides, and hazardous dyes are summarized. Finally, some challenges faced by nanohybrid porous materials to achieve their potential application as advanced catalysts for environmental remediation have been identified and presented herein.

Design and Microwave-Assisted Synthesis of TiO2-Lanthanides Systems and Evaluation of Photocatalytic Activity under UV-LED Light Irradiation

The TiO2-Eu and TiO2-La systems were successfully synthesized using the microwave method. Based on the results of X-ray diffraction analysis, it was found that regardless of the analyzed systems, two crystal structures were noted for the obtained samples: anatase and rutile. The analysis, such as XPS and EDS, proved that the doped lanthanum and europium nano-particles are present only on the TiO2 surface without disturbing the crystal lattice. In the synthesized systems, there were no significant changes in the bandgap energy. Moreover, all the obtained systems were characterized by high thermal stability. One of the key objectives of the work, and a scientific novelty, was the introduction of UV-LED lamps into the metronidazole photo-oxidation pathway. The results of the photo-oxidation study showed that the obtained TiO2 systems doped with selected lanthanides (Eu or La) show high efficiency in the removal of metronidazole, and at the same consuming nearly 10 times less electricity compared to conventional UV lamps (high-pressure mercury lamp). Liquid-chromatography mass-spectrometry (LC-MS) analysis of an intermediate solution showed the presence of fragments of the degraded molecule by m/z 114, 83, and 60, prompting the formulation of a plausible photodegradation pathway for metronidazole.