Abstracts

Rare earth vanadates are classic luminescent systems offering a unique combination of properties for emerging applications combining thermal or chemical sensing and enzyme-like catalysis. Whilst appropriate control of composition, crystallinity, size, and morphology is critical for the proposed applications, vanadate nanoparticles often exhibit complex internal microstructures arising from non-classical nucleation/growth processes in liquid-phase. Furthermore, nanostructural character imposes additional restrictions on luminescence quantum yields due to surface and dielectric effects, thus increasing the number of aspects to be considered in the design of this class of materials. Rational control of the internal microstructure of colloidal oxide nanoparticles is still a matter of investigation, and development of processing techniques for the improvement of target properties requires a full picture of the internal chemical environment. Detailed information on poly- vs. nanocrystallinity, porosity, defect density, and microstrain involve a combination of multiple characterisation tools, but our recent observations regarding Eu³⁺ spectroscopic properties reveal interesting insights on the microstructure of REVO₄ nanoparticles. In summary, analysis of B₂ and E ⁵D₀→⁷F₂ Stark components in terms of relative intensities, bandwidth, and unfolding provides direct correlation on long-range crystallinity, defect density, distortions on coordination polyhedra, and desymmetrisation in the tetragonal I4₁/amd structure. We evaluated the emission spectra of bulk/single-crystalline, nano/single-crystalline, nano/polycrystalline, and nano/polycrystalline/high-entropy REVO₄ solids [RE=Y, Ce, and (Y,La,Gd,Yb,Lu)] doped with Eu³⁺ with different degrees of defect density. In addition to UV-excited downshift Eu³⁺ emissions, some of the particles also showed unconventional Eu³⁺ upconversion luminescence. Our results confirm the use of luminescence spectra as an additional tool to describe the internal structure of complex nanoparticles, thus enabling further advance in the rational design of REVO₄ colloidal particles for thermometry and catalysis applications.References: J. Phys. Chem. C 2024, 128, 1, 667–670. Cryst. Growth Des. 2023, 23, 8, 5389–5396. Chem. Commun. 2023,59,11393-11396. Nanoscale 2021,13, 4931-4945.