Ionic Self-Assembled Luminescent Nanospheres from Cationic Polyelectrolyte and Eu-Containing Polyoxometalate

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Luminescence Spectroscopy

Background:

• Europium-containing polyoxometalates (Eu-POMs) exhibit luminescence but suffer from solvent quenching and poor processability.
• Ionic self-assembly (ISA) offers a strategy to combine Eu-POMs with organic molecules via noncovalent electrostatic interactions.
• Protecting Eu-POMs from solvent quenching is crucial for enhancing their luminescence properties and practical applications.

Purpose of the Study:

• To construct luminescence-enhanced spherical aggregates using Eu-POMs and a cationic polyelectrolyte.
• To investigate the effect of ionic self-assembly on the photophysical properties of Eu-POMs.
• To explore the potential of these aggregates as sensors for specific analytes.

Main Methods:

• Synthesis of spherical aggregates using Na9(EuW10O36)·32H2O (EuW10) and branched polyethyleneimine (PEI) via ionic self-assembly.
• Characterization of aggregate size (50-200 nm) and modulation of properties by PEI concentration.
• Measurement of luminescence properties, including absolute quantum yield and luminescence lifetime.

Main Results:

• Ionic self-assembly effectively shielded EuW10 from solvent quenching, leading to enhanced luminescence.
• The absolute quantum yield and luminescence lifetime of the aggregates increased 10-fold and 5-fold, respectively, compared to bare EuW10.
• The aggregates demonstrated sensitivity to copper cations and permanganate anions, enabling their detection via luminescence quenching.

Conclusions:

• The developed luminescent soft material provides a model for enhancing lanthanide luminescence through self-assembly in aqueous solutions.
• The synthesized aggregates exhibit potential for application in luminescence-based detection and analysis.
• This work highlights the effectiveness of ISA in creating functional luminescent materials with improved photophysical properties.