Rare earth spectroscopy as a tool to monitor ion exchange of species incorporated between layers of hybrid layered double hydroxides

• Grant number: 25/00720-0
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2025
• End date: April 30, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Danilo Mustafa
• Grantee: Danilo Mustafa
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The two-dimensional arrangement of the structure of layered double hydroxides (LDH) results in a very important type of inorganic layered matrix considering the versatility in terms of its chemical composition. Thus, not only can the cations present in the layered structure be partially replaced by rare earth elements, but also sensitizing molecules can be accommodated between its layers through ion exchange with intercalated anions.Recent research has demonstrated the potential applications of layered double hydroxides as carriers of desired molecules, which motivated us to study this type of material as a possible agent for controlling the release of drugs in the body and the absorption of pollutant molecules.In addition to the search for these materials, some important properties of rare earth ions can be used as a tool for studying the adsorption and release of species between the metallic layers of these materials. In the case of Eu3+, our group is aware that the intercalation of certain anions creates a less centrosymmetric chemical environment for the ion. The direct consequence of this is a distortion in the coordination around Eu3+ towards a less centrosymmetric configuration, relaxing the selection rules for its 4f-4f transitions. This mechanism is responsible for the modifications in the spectral profile of these materials, suggesting that these anions interact directly with the Eu centers hosted in the LDHs and/or strongly affect the coordination geometry around Eu. The relative intensities of the 4f-4f transitions of rare earth ions, however, can be largely modified by the symmetry and composition of their first coordination sphere. This effect makes them powerful spectroscopic probes for local chemical and crystalline modifications of the host material during chemical processes and reactions.Therefore, it is expected to use these properties of rare earths to monitor the changes caused by the adsorption of different ions between the layers of LDHs with the capacity for storage and transport of pharmaceuticals and environmental remediation, integrating the areas of physics and chemistry. (AU)