Recently, hybrid
coassembly between polyoxometalates (POMs) and
cationic building blocks provides an efficient strategy to greatly
optimize POMs’ functionality as well as their aggregate structural
diversity. Adaptive hybrid supramolecular materials with enhanced
luminescence have then been obtained from lanthanide-containing POMs.
In this work, a commercially available and pH-switchable zwitterionic
surfactant, tetradecyldimethylamine oxide (C14DMAO), was
chosen to coassemble with a lanthanide-containing anionic POM [Na9(EuW10O36)·32H2O, abbreviated
as EuW10] in water. The much improved red-emitting luminescent
nanobelts at a C14DMAO/EuW10 molar ratio (R) of 20 were obtained, which exhibited longer luminescence
lifetime and higher quantum yield compared with EuW10 aqueous
solution. After careful characterization of morphology and structure
of nanobelts, an unusual axial lamellar aggregation arrangement mechanism
was proposed. It was the partial protonation of C14DMAO
at the solution pH of about 6.5 that led to positively charged micelles,
being bridged by anionic EuW10 clusters to aggregate into
such novel nanobelts under the synergetic effects of appropriate electrostatic,
hydrogen-bonding, and hydrophobic interactions. The resulted pH-responsive
luminescent nanobelts and their aggregation model should offer attractive
references for preparing smart optical supramolecular materials.