Abstracts
Optical spectroscopy of inorganic phosphors
Exploring downshift and upconversion optical responses to detail internal structure of vanadate nanocrystalsPaulo C. de S. Filho1
1Universidade Estadual de Campinas (UNICAMP), Department of Inorganic Chemistry, Brazil
E-mail: pcsfilho@unicamp.br
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.
Keywords: Vanadates; Nanoparticles; Colloids; Europium
Acknowledgments: We thank CAPES, CNPq (405048/2021-1, 310654/2022-0), FAEPEX-UNICAMP, and FAPESP (2022/03442-3) for financial support and scholarships.