Alessandro Lauria

Last Name

Lauria

First Name

Alessandro

ORCID

0000-0002-7978-2687

Organisational unit

03763 - Niederberger, Markus / Niederberger, Markus

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Publications 1 - 6 of 6

Charge compensation in europium-doped hafnia nanoparticles: Solvothermal synthesis and colloidal dispersion
Guichard, Xavier H.; Bernasconi, Francesco; Lauria, Alessandro (2021)
Crystals
Effective charge compensation of europium in hafnium oxide nanoparticles was achieved at low temperature, allowing high doping incorporation (up to 6 at.%) and enhanced luminescence. The efficiency of the incorporation and charge compensation was confirmed by scanning electron microscope energy dispersive X-ray spectroscopy and powder X-ray diffraction measurements. Despite the known polymorphism of hafnium oxide, when doped to a concentration above 3 at.%, only the pure monoclinic phase was observed up to 6 at.% of europium. Furthermore, the low-temperature solvothermal route allowed the direct formation of stable dispersions of the synthesized material over a wide range of concentrations in aqueous media. The dispersions were studied by diffuse light scattering (DLS) to evaluate their quality and by photoluminescence to investigate the incorporation of the dopants into the lattice.
Controlled Impurity Admixture: From Doped Systems to Composites
Lauria, Alessandro; Niederberger, Markus (2021)
Metal Oxide Nanoparticles: Formation, Functional Properties, and Interfaces, Volume 2
Solid solubility is often enhanced with decreasing particle size, which means that nanoparticles can be doped or alloyed with atoms or ions that show a miscibility gap on the bulk level under the same conditions. If the solubility limit is reached, the nanoparticles undergo phase segregation and form multicomponent or heterostructured nanomaterials. This chapter provides an overview of the different synthesis techniques for doped, alloyed and phase-segregated metal oxide nanoparticles. It begins with liquid-phase routes, proceed to gas-phase methods and then discusses solid-state approaches. The chapter presents examples, where phase-segregation or seeded growth leads to the formation of composite or multicomponent materials. It focuses clearly on the synthesis. In the case of doped nanoparticles, the precise incorporation of impurity atoms represents an additional experimental complication going well beyond simple compositional control.
Heat-Induced Transformation of Luminescent, Size Tuneable, Anisotropic Eu:Lu(OH)2Cl Microparticles to Micro-Structurally Controlled Eu:Lu2O3 Microplatelets
Fellner, Madeleine; Soppelsa, Alberto; Lauria, Alessandro (2021)
Crystals
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare earth emitter ions. However, rare earth sesquioxides are challenging to synthesise using bottom-up methods. Therefore, calcination represents an interesting approach to transform lutetium-based particles to corresponding sesquioxides. Here, the controlled solvothermal synthesis of size-tuneable europium doped Lu(OH)(2)Cl microplatelets and their heat-induced transformation to Eu:Lu2O3 above 800 degrees C are described. The particles obtained in microwave solvothermal conditions, and their thermal evolution were studied using powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, thermogravimetric analysis (TGA), luminescence spectroscopy (PL/PLE) and infrared spectroscopy (ATR-IR). The successful transformation of Eu:Lu(OH)(2)Cl particles into polycrystalline Eu:Lu2O3 microparticles is reported, together with the detailed analysis of their initial and final morphology.
Caesium manganese fluoride cubic-perovskite nanoparticles - synthesis, luminescence and magnetic properties
Fellner, Madeleine; Lauria, Alessandro (2023)
Journal of Sol-Gel Science and Technology
Lead halide perovskite materials have outstanding optical properties such as color purity and efficient fluorescence in the visible spectrum. However, the toxicity of lead makes the synthesis, processing, use and disposal of such materials hazardous for humans and the environment. Therefore, the exploration of different perovskite materials containing the transition metal Mn(II) and fluoride anions might lead to more appealing alternatives towards more sustainable and environmentally friendly functional materials. Nanocrystals primarily consisting of cubic CsMnF3 - a polymorph so far only reported at pressures of 3 x 10(4 )bar - were synthesized from manganese(II) acetate and caesium fluoride precursors using a heating-up approach in high boiling organic solvents. The concentration of defects could be tuned by changing the amount of fluorinating precursor CsF, with more defects produced when an excess of CsF was used in the synthesis. The structure, morphology, optical and magnetic properties of the product nanoparticles were studied. Due to their X-ray sensitized fluorescence, likely caused by defects in the crystal structure, these materials are promising for potential applications in dosimetry.
Decoupling of the Crystal Structure and Upconversion in HfO₂ Nanocrystals: Emission Chromaticity to Determine the Nanoscale Dopant Distribution
Guichard, Xavier; Lauria, Alessandro (2024)
Chemistry of Materials
The study of rare-earth (RE)-based upconversion in HfO₂ nanocrystals must consider the dual role of aliovalent doping. In fact, in this oxide, RE³⁺ doping not only induces luminescence but also perturbs the host material structure, leading to higher-symmetry polymorphs. Such a change of the crystal structure further affects the optical properties, making equivocal the interpretation of the upconversion luminescence (UCL) dependence on rare-earth sensitizer (Yb³⁺) and activator (Er³⁺) concentrations. We propose the introduction of an additional optically inactive dopant (Lu³⁺), enabling the investigation of the separate influence of the crystal structure and dopant concentrations on upconversion. For identical concentrations of Er³⁺ and Yb³⁺, the comparison of the cubic and monoclinic polymorphs of HfO₂ shows the essential role of the crystal structure alone on UCL. In cubic HfO₂, the emission intensity and chromaticity vary by more than 2 orders of magnitude depending on Er³⁺ and Yb³⁺ concentrations. Furthermore, the labeling of upconversion spectral features in phase-pure polymorphs and their correlation with the composition allow a clearer interpretation of UCL in phase mixtures, where the use of UCL chromaticity to determine the local rare-earth distribution reveals its intrinsic inhomogeneity at the nanoscale between different polymorphs. Hence, these results represent an important step toward highly efficient upconverting hafnia nanocrystals with tunable optical properties and provide a deeper understanding of doping distribution during the formation of mixed-phase particle systems.
Maximizing photocatalytic efficiency with minimal amount of gold: Solar-driven TiO₂ photocatalysis supported by MICROSCAFS® for facile catalyst recovery
Fernandes, Sofia Moreira; Barrocas, Beatriz Trindade; Nardeli, Jéssica Verger; et al. (2024)
Journal of Environmental Chemical Engineering
Multicomponent oxide (i.e., SiO2-TiO2) microspheres with interconnected meso and macroporosity, called MICROSCAFS®, are attractive for various applications. Here, we present them as robust and efficient catalyst supports, facilitating straightforward purification of wastewater through solar-driven photocatalysis, and an easy recovery and reuse. We report on the immobilization of titanium dioxide (TiO2) and gold nanoparticles (Au NPs) into the MICROSCAFS® and their characterization using various analytical techniques. The supported catalysts were tested for solar (1 sun) photocatalytic degradation of two different pollutants: the organic dye methyl orange (MO) and the antibiotic minocycline (MC). The results showed that the presence of Au NPs, in nominal concentrations between 0.02 and 0.08 wt%. improved the photocatalytic performance, achieving up to 20% higher degradation for MO, compared to the sample without gold. In the case of MC, we observed an initial 45.5% adsorption, followed by complete photodegradation under irradiation in less than 1 h. The supported catalysts also demonstrated good recyclability, with improved photocatalytic performance observed in the case of MC, and decreased adsorption tendency for the subsequent cycles. The transformation products (TPs) were elucidated by high-resolution mass spectrometry experiments. For MO, the results showed the generation of three TPs, with lower toxicity for aquatic species, while for MC there were only two TPs, which are completely removed within less than 2 h of irradiation. Overall, this study highlights the potential of MICROSCAFS® as an efficient photocatalyst support for the degradation of organic pollutants under solar light irradiation.

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Alessandro Lauria

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