APTES-modified RE2O3:Eu3+ luminescent beads: structure and properties

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Lanthanide oxide nanoparticles doped with europium (Eu3+) exhibit desirable luminescent properties.
• Surface functionalization is crucial for integrating nanoparticles into various systems and enhancing their performance.
• 3-aminopropyltriethoxysilane (APTES) is a common silane coupling agent used to introduce amine functionalities onto oxide surfaces.

Purpose of the Study:

• To functionalize europium-doped Yttrium (Y2O3:Eu3+) and Gadolinium (Gd2O3:Eu3+) oxide nanoparticles with amine groups using APTES.
• To characterize the surface modification and quantify the density of amine groups.
• To evaluate the impact of APTES modification on the luminescent properties of the nanoparticles.

Main Methods:

• Synthesis of spherical Y2O3:Eu3+ and Gd2O3:Eu3+ luminescent beads (150 ± 15 nm diameter).
• Surface modification via direct silanation with APTES.
• Characterization using Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS).
• Quantification of amine groups by titration using fluorescein isothiocyanate and luminescence measurements.
• Assessment of luminescence properties before and after surface modification.

Main Results:

• Successful grafting of a nanometric APTES layer onto the oxide beads with an optimal rate of 0.055 ± 0.005 mol APTES/mol RE2O3.
• Confirmation of organosilane layer formation via FTIR and XPS, indicating cross-linked siloxane bonds and pendant amine groups.
• Quantification of approximately 2.3 × 10^4 (Y2O3:Eu3+) and 2.8 × 10^4 (Gd2O3:Eu3+) amine groups per bead.
• A shift in the isoelectronic point by one pH unit after APTES modification.
• Preservation (Gd2O3:Eu3+) or improvement (Y2O3:Eu3+) of the red emission intensity after surface modification.

Conclusions:

• APTES surface modification effectively introduces reactive amine groups onto europium-doped lanthanide oxide beads.
• The functionalization process maintains or enhances the characteristic red luminescence of the nanoparticles.
• These modified nanoparticles are suitable for applications requiring amine-functionalized luminescent materials.