Bifunctional Paramagnetic and Luminescent Clays Obtained by Incorporation of Gd3+ and Eu3+ Ions in the Saponite Framework.

Stefano Marchesi,Fabio Carniato,Carlos Platas-Iglesias,Daniela Lalli,Chiara Bisio,Leonardo Marchese

doi:10.1021/acs.inorgchem.1c01455

Stefano Marchesi, Fabio Carniato + Show 4 more

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https://doi.org/10.1021/acs.inorgchem.1c01455

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Abstract

A novel bifunctional saponite clay incorporating gadolinium (Gd3+) and europium (Eu3+) in the inorganic framework was prepared by one-pot hydrothermal synthesis. The material exhibited interesting luminescent and paramagnetic features derived from the co-presence of the lanthanide ions in equivalent structural positions. Relaxometry and photoluminescence spectroscopy shed light on the chemical environment surrounding the metal sites, the emission properties of Eu3+, and the dynamics of interactions between Gd3+ and the inner-sphere water placed in the saponite gallery. The optical and paramagnetic properties of this solid make it an attractive nanoplatform for bimodal diagnostic applications.

Highlights

There has been large interest in the optimization and employment of synthetic clays for scientific and technological applications.[1−15] In particular, synthetic saponite clays have been studied for their interesting properties, in terms of high thermal stability, specific surface area, tunable acidity, low costs, and excellent chemical versatility.[1−3]
Na-GdEuSAP and the reference samples (Na-EuSAP and Na-GdSAP) were prepared by adapting a one-pot hydrothermal procedure reported in the literature (Scheme S1).[22−24] Eu3+ and Gd3+ were inserted as chloride salts during the preparation of the gel, in the presence of silicon, aluminum, and magnesium sources
The bifunctional saponite sample studied here exhibited interesting optical and magnetic properties associated to the co-presence of Eu3+ and Gd3+ ions in structural positions

Summary

Introduction

There has been large interest in the optimization and employment of synthetic clays for scientific and technological applications.[1−15] In particular, synthetic saponite clays have been studied for their interesting properties, in terms of high thermal stability, specific surface area, tunable acidity, low costs, and excellent chemical versatility.[1−3]Their chemical properties can be tuned by modifying the particle size[2] and/or chemical composition of the interlayer space[4] and the inorganic framework.[5,6] These modifications can be achieved using specific post-synthetic treatments (i.e., intercalation of cationic organic and inorganic compounds) or properly modifying the synthesis method and selecting appropriate precursors for one-pot syntheses.On this basis, with a proper choice of the intercalated entities (i.e., metal ions, dyes, ...) or by modifying the synthetic protocols, it is possible to design new functionalized saponites with innovative features suitable for different applications.[13−20] In particular, the introduction of one or more f-block elements (i.e., Gd3+, Eu3+, Tb3+, ...), in the form of ions or complexes, allows preparing novel versatile materials owning the chemical and mechanical robustness of saponite clays and the peculiar luminescent and magnetic properties conferred by the metal ions. There has been large interest in the optimization and employment of synthetic clays for scientific and technological applications.[1−15] In particular, synthetic saponite clays have been studied for their interesting properties, in terms of high thermal stability, specific surface area, tunable acidity, low costs, and excellent chemical versatility.[1−3] Their chemical properties can be tuned by modifying the particle size[2] and/or chemical composition of the interlayer space[4] and the inorganic framework.[5,6] These modifications can be achieved using specific post-synthetic treatments (i.e., intercalation of cationic organic and inorganic compounds) or properly modifying the synthesis method and selecting appropriate precursors for one-pot syntheses. The in-depth analysis of the relaxometric properties of such functionalized solids allowed access to the chemical environment of the confined chelates and to the water diffusion processes within the interlayer space.[4]

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