Relaxation Processes in Rare-Earth-Doped a-NaYF₄ Nanoparticles by Nuclear Magnetic Resonance Spectroscopy

Author(s)

Flores, Ali F. Garcia ; Munevar, Julian ; de Oliveira, Marcos ; Rettori, Carlos ; Urbano, Ricardo R. ; de Queiroz, Thiago B.

• Document type: Journal article
• Source: Journal of Physical Chemistry C; v. 127, n. 37, p. 11-pg., 2023-09-11.

Abstract

NaYF4 nanoparticles (NPs) are among the most promising hosts for lanthanides in different applications as IR-to-UV upconversion and photodynamic therapy due to their crystal electric field properties and their low phonon energy. The efficiency in such applications depends on the dispersion of the ions and their local structure in the host. Paramagnetic nuclear magnetic resonance (NMR) has been one of the main tools to perform such studies, based on the comprehensiveness of the hyperfine interaction of the rare-earth (RE)' s unpaired electrons with the observed nuclei and its effects in NMR quantities, like paramagnetic shift, line broadening, and relaxation enhancement. However, it can be challenging to resolve these effects for spin systems with large dipolar or quadrupolar interactions and site heterogeneity. We hereby address these issues for RE3+-doped alpha-NaYF4 NPs of small sizes and low polydispersity [phi approximate to 7(1) nm] with Na-23 and F-19 NMR employing high-resolution techniques associated with relaxation measurements. In particular, remarkable fast relaxation rates are found for the Gd3+-doped NPs which are rationalized in terms of Solomon ' s relaxation mechanism enhanced by the long electronic relaxation time of the ion. (AU)

• FAPESP's process: 22/02974-1 - Fundamental aspects of the amorphous state of metal organic compounds: a solid state magnetic resonance approach
• Grantee: Marcos de Oliveira Junior
• Support Opportunities: Research Grants - Initial Project
• FAPESP's process: 19/09673-4 - Technical and computational support for synthesis and characterization of metallic and insulator nanoparticles
• Grantee: Alí Francisco García Flores
• Support Opportunities: Scholarships in Brazil - Technical Training Program - Technical Training
• FAPESP's process: 20/13466-1 - Design, synthesis and characterization of molecular systems for light harvesting and charge separation
• Grantee: Thiago Branquinho de Queiroz
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 17/10581-1 - Emergent phenomena in reduced dimension systems
• Grantee: Pascoal Jose Giglio Pagliuso
• Support Opportunities: Special Projects