1 research outputs found
Unusual Aggregation Arrangement of Eu-Containing Polyoxometalate Hybrid in a Protic Ionic Liquid with Improved Luminescence Property
Hybridization
of polyoxometalates (POMs) with cationic surfactants
offers the opportunity to greatly improve their functionalities as
well as processabilities. Here, a surfactant-encapsulated Eu-containing
POM complex (SEP) was formed via electrostatic interaction between
1-octadecyl-3-methylimidazolium bromide (OB) and Na<sub>9</sub>(EuW<sub>10</sub>O<sub>36</sub>)·32H<sub>2</sub>O (EuW<sub>10</sub>).
SEP was first self-assembled in a protic ionic liquid to prepare the
soft aggregates to fundamentally avoid the fluorescence quenching
by water molecules. The structures and photophysical properties of
SEP or aggregates were investigated thoroughly by NMR and FTIR spectroscopy,
optical and electron microscopy, small-angle X-ray scattering, and
fluorescence measurements. The formed gel-like aggregates were found
to compose of three-dimensional networks of microribbons with an interdigitated
layered molecular packing of SEP, which was different from the usual
inverse bilayer model of POM hybrids in common organic solvents. Compared
to EuW<sub>10</sub> solid or its aqueous solution, both SEP and its
aggregates exhibited intense red luminescence with much improved lifetime
and quantum efficiency. In addition, the soft aggregates exhibited
an efficient energy transfer and an obviously enhanced monochromaticity,
owning to the organized arrangement of EuW<sub>10</sub> units and
a confined microenvironment to isolate them from each other between
adjacent layers. The obtained results will not only present a useful
reference to the aggregation behavior of POM hybrids in ionic liquids,
but also provide an easy way to design EuW<sub>10</sub> luminescent
soft materials based on the nonaqueous media