Anatase versus Triphasic TiO2: Near-identical synthesis and comparative structure-sensitive photocatalytic degradation of methylene blue and 4-chlorophenol

Charge separation effect in the nanocomposites of Co3O4-QDs: visible light photocatalytic dye degradation in aqueous solutions

Photo-treatment of water is a promising environmentally friendly process that provides clean water and makes wastewater reusable in industry. Thus, efforts toward finding highly efficient photocatalysts have gained a huge attention to remove the organic contaminants in water. Quantum dots (QDs) are extensively utilized for photocatalytic remediation regarding their prominent optical, electrical, and chemical properties. Herein, we report the highly efficient and environmentally friendly synthesis of Co₃O₄-QDs-based graphene quantum dots (GQDs) and infinite coordination polymer comprising Zn nodes (Zn-ICP) nanocomposites as active and robust photocatalysts for photo-assisted water treatment. The pristine Co₃O₄-QDs, GQDs, and Zn-ICP showed lower activity under visible light. However, after functionalization of GQDs and Zn-ICP with Co₃O₄-QDs, the activity increased, and more photocatalytic efficiency was achieved. For instance, Zn-ICP, GQDs, Co₃O₄-QDs, Co₃O₄-QDs/Zn-ICP, and Co₃O₄-QDs/GQD degraded 21, 19, 52, 73, and 83% of rhodamine B (RhB) and 34, 46, 50, 73, and 76% of methylene blue (MB) after 60 min. The high photocatalytic efficiency was ascribed to the conjugation of Co₃O₄-QDs with GQDs and Zn-ICP which causes efficient absorption of visible light. The existence of Co₃O₄-QDs was found to be essential not only for effective charge separation but also widening the region of light absorption followed by increase in photocatalytic performances. Charge separation in photocatalytic reactions, energy levels of nanocomposites, and mechanism of the photocatalytic process were investigated by photoluminescence spectra (PL), Mott-Schottky, electrochemical impedance (EIS), and diffuse reflectance UV-Vis spectroscopy (DRS).

First-principles modelling of the new generation of subnanometric metal clusters: Recent case studies

The very recent development of highly selective techniques making possible the synthesis and experimental characterization of subnanometric (subnanometer-sized) metal clusters (even single atoms) is pushing our understanding far beyond the present knowledge in materials science, driving these clusters as a new generation of quantum materials at the lower bounds of nanotechnology. When the size of the metal cluster is reduced to a small number of atoms, the d-band of the metal splits into a subnanometric d-type molecular orbitals network in which all metal atoms are inter-connected, with the inter-connections having the length of a chemical bond (1-2 Å). These molecular characteristics are at the very core of the high stability and novel properties of the smallest metal clusters, with their integration into colloidal materials interacting with the environment having the potential to further boost their performance in applications such as luminescence, sensing, bioimaging, theranostics, energy conversion, catalysis, and photocatalysis. Through the presentation of very recent case studies, this Feature Article is aimed to illustrate how first-principles modelling, including methods beyond the state-of-the-art and an interplay with cutting-edge experiments, is helping to understand the special properties of these clusters at the most fundamental level. Moreover, it will be discussed how superfluid helium droplets can act both as nano-reactors and carriers to achieve the synthesis and surface deposition of metal clusters. This concept will be illustrated with the quantum simulation of the helium droplet-assisted soft-landing of a single Au atom onto a titanium dioxide (TiO₂) surface. Next, it will be shown how the application of first-principles methods have disclosed the fundamental reasons why subnanometric Cu₅ clusters are resistant to irreversible oxidation, and capable of increasing and extending into the visible region the solar absorption of TiO₂, of augmenting its efficiency for photo-catalysis beyond a factor of four, also considering the decomposition and photo-activation of CO₂ as a prototypical (photo-) catalytic reaction. Finally, I will discuss how the modification of the same material with subnanometric Ag₅ clusters has converted it into a "reporter" of a surface polaron property as well as a novel two-dimensional polaronic material.

Controllable Synthesis of Modified Porous Anatase TiO₂ with High Photocatalytic Activity

In this study, we added ZrO₂ and Y₂O₃ to stabilize the anatase TiO₂ phase at higher temperatures. Composite mesoporous TiO₂/ZrO₂/Y₂O₃ (TZY) oxides were prepared by a sol-gel method, and triblockcopolymer P123 and PEG was used as templates. The properties of the synthesized materials were characterized using X-Ray diffraction (XRD), Raman scattering, N₂ adsorption/desorption, and UV-Visible spectrophotometry (UV-Vis) methods et al. The samples prepared using P123 and PEG as double-template exhibited smaller particles and a higher specific surface area than the samples prepared using P123 and PEG as single-template. Furthermore, crystal phase transition from anatase to rutile occurred later in the case of the double-template method. After introducing ZrO ₂and Y₂O₃, the crystal phase transition and the growth of crystallites were severely suppressed. The results indicated that the RhB degradation efficiency for the double-template method was 99.24%, while the RhB degradation efficiency with TZY/P123 and TZY/PEG samples was 97.43 and 98.18%, respectively.

Photocatalytic degradation of methylene blue under UV and visible light by brookite–rutile bi-crystalline phase of TiO2

Brookite–rutile bi-crystalline phase of TiO₂ were synthesized and applied for the degradation of methylene blue under UV and visible light irradiation by photocatalytic reaction.

Defect Engineering Enhances the Charge Separation of CeO2 Nanorods toward Photocatalytic Methyl Blue Oxidation

Defect-rich photocatalytic materials with excellent charge transfer properties are very popular. Herein, Sm-doped CeO₂ nanorods were annealed in a N₂ atmosphere to obtain the defective Sm-doped CeO₂ photocatalysts (Vo–Sm–CeO₂). The morphology and structure of Vo–Sm–CeO₂ were systematically characterized. The Vo–Sm–CeO₂ nanorods demonstrated an excellent photodegradation performance of methyl blue under visible light irradiation compared to CeO₂ nanorods and Sm–CeO₂. Reactive oxygen species including OH, ·O₂⁻, and h⁺ were confirmed to play a pivotal role in the removal of pollutants via electron spin resonance spectroscopy. Doping Sm enhances the conductivity of CeO₂ nanorods, benefiting photogenerated electrons being removed from the surface reactive sites, resulting in the superior performance.