Juliana dos Santos de Souza

Persistent luminescent (PersL) materials are in evidence nowadays due to their property of charge storage in the form of trapped electrons that are released slowly with time. Usually, PersL materials are applied in a range of applications from decoration objects to bioimaging. Here, persistent luminescence ZnGa2O4:Cr3+ nanoparticles are demonstrated as persistent photocatalysts for hydrogen production, expanding the range of applications of this material. Synthesized via a solvothermal liquid–solid-solution route with oleic acid, the crystalline, monodisperse nanoparticles (∼10 nm) exhibit strong UV-C absorption and near-infrared emission. Under UV–vis irradiation with triethanolamine as a sacrificial agent, they deliver substantial H2 yields and show measurable postirradiation hydrogen evolution. Synchrotron-based XANES, XRF, and XEOL measurements reveal a homogeneous elemental distribution and show that excitation is primarily driven by the host lattice, with energy transfer to Cr3+ centers rather than direct excitation of the dopant. EPR and Mott–Schottky analyses indicate that Cr-related states and defect-induced traps store photogenerated charges and release them gradually, while band structure measurements confirm that proton reduction is thermodynamically favorable. These findings highlight the potential of persistent luminescent materials to sustain photocatalytic hydrogen production beyond the illumination period, opening opportunities for further investigation of postillumination photocatalytic systems.

The optoelectronic properties and crystallization behavior of formamidinium lead iodide (FAPbI ₃ ) perovskites are highly sensitive to processing conditions, particularly moisture during annealing.

Developing efficient photoelectrocatalysts is crucial for advancing sustainable energy solutions to generate green hydrogen, particularly in photoelectrochemical water splitting. This study addresses these limitations by synthesizing and characterizing WO₃/(W)BiVO₄ heterojunctions incorporated with graphitic carbon nitride (C₃N₄). Our approach combines a microwave-assisted synthesis for heterojunction formation with the direct polymerization of C₃N₄, aiming to enhance the charge separation and light absorption. Structural and morphological analyses confirmed the presence of well-defined heterojunctions with homogeneous element distributions, while spectroscopic studies demonstrated enhanced visible light absorption. Our results show the potential of WO₃/(W)BiVO₄/C₃N₄ systems as durable and efficient photoanodes. The further optimization of polymerization conditions and band alignment strategies may unlock greater efficiency, paving the way for more effective solar-driven hydrogen production.

Zinc oxide (ZnO) nanoparticles are widely used in cosmetic and pharmaceutical formulations; however, their dispersion in viscous organic media is often limited by aggregation and poor compatibility. In this work, the in situ formation of ZnO nanoparticles directly within polyethylene glycol (PEG 400) is investigated using a microwave-assisted solvothermal approach. A design of experiments (DoE) framework was applied to evaluate the influence of heating ramp, reaction temperature, and holding time on particle morphology and crystallinity, as well as on liquid-phase properties. Electron microscopy indicates that higher temperatures and longer reaction times tend to promote the formation of smaller and more anisotropic particles. X-ray diffraction shows the formation of crystalline ZnO with a wurtzite structure under all investigated conditions. The statistical analysis suggests relationships between synthesis parameters and particle aspect ratio, although with limitations inherent to the experimental design. The PEG phase exhibited progressive yellowing under more severe conditions, suggesting possible oxidative processes, whereas Raman spectroscopy did not reveal significant changes in the polymer’s main molecular features within the technique’s sensitivity. Overall, the results provide insight into nanoparticle formation within viscous oligomeric media and indicate that in situ synthesis in PEG may represent a viable route to improve compatibility between inorganic nanoparticles and organic matrices, potentially reducing the need for post-synthesis dispersion steps.

Nonequilibrium synthesis provides a powerful route to access metastable structural states that are inaccessible under near-equilibrium conditions, yet quantitative links between growth kinetics, defect structure, and functional response remain poorly understood. Here, we investigate the microwave-assisted synthesis of Eu³⁺- and Tb³⁺-doped Lu₂O₃ nanocrystals as a model system to elucidate how nonequilibrium crystallization kinetically encodes lattice microstrain and governs material properties. Time-resolved X-ray diffraction, transmission electron microscopy, and kinetic modeling reveal diffusion-controlled crystallite growth consistent with Ostwald ripening, accompanied by persistent microstrain that relaxes only partially with microwave irradiation time. Williamson–Hall analysis demonstrates that dopant chemistry systematically modulates the magnitude and evolution of microstrain, indicating a coupling between defect formation and mass transport under microwave heating. Photoluminescence spectroscopy shows that Eu³⁺ hypersensitive transitions and Eu–O charge-transfer states track microstrain directly, establishing lattice strain as an internal structural field that tunes local symmetry and electronic structure. In contrast, Tb³⁺ emission is primarily quenched by defect-mediated nonradiative processes, highlighting dopant-selective coupling to strain. These structure–optical correlations are mirrored in photocatalytic performance, where intermediate strain levels maximize activity by balancing internal electric fields and defect recombination. Together, these results demonstrate that microwave-assisted nonequilibrium synthesis enables the kinetic encoding of lattice microstrain, providing a general strategy to rationally design functional oxide nanomaterials through controlled growth pathways rather than composition alone.

The urgent need to address global energy demands and mitigate climate change has driven research toward sustainable methods of hydrogen production. Photocatalytic water splitting represents a promising pathway for the generation of green hydrogen, provided that efficient, stable, and sustainably produced photocatalysts are developed. In this work, orthorhombic sodium niobate (NaNbO₃) nanowires were synthesized via a microwave-assisted hydrothermal route, a green, time-efficient, and energy-saving strategy that yielded high-surface-area structures. Platinum was incorporated as a cocatalyst to enhance charge separation and promote hydrogen evolution reaction (HER) activity. Comprehensive structural, morphological, and spectroscopic analyses revealed that Pt incorporation occurred at the molecular level, potentially altering the crystal growth orientation, increasing the surface area, and altering the band structure. While Pt loading reduced NaNbO₃ activity toward the oxygen evolution reaction (OER), it significantly boosted HER performance, achieving 1.26 mmol h^–1 g^–1 of H₂, over four times higher than pristine NaNbO₃, and comparable to the best reported systems, but obtained through a more sustainable synthesis route. These results highlight the combined benefits of microwave-assisted synthesis and Pt integration in the production of efficient photocatalysts for renewable hydrogen generation.

Heterojunction based on ZnO and BiNbO ₄ boosts photocurrents on OER and enhances H ₂ production offering a fast, energy-efficient solution for photo(electro)catalytic applications.