Dual-Responsive Ionically
Assembled Fluorescent Nanoparticles
from Copoly(Ionic Liquid) for Temperature Sensor
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Abstract
A simple copolymer, copoly(ionic liquid), consisting
of <i>N</i>-isopropylacrylamide (NIPAM) and 1-benzyl-4-vinylpyridine
bromide (4-VPBn<sup>+</sup>Br<sup>–</sup>) units as thermo-responsive
and ionic liquid parts, respectively, has been synthesized. Fluorescent
nanoparticles (FNPs) were then formed under the driving forces of
electrostatic interaction between 2-(4-amino-2-hydroxyphenyl) benzothiazole
derivative (AHBTA) and copoly(ionic liquid) due to hydrophilic/hydrophobic
balance. The fluorescent intensity of the FNPs enhanced by a factor
of about 50 times when the pH was increased from 7 to 10, and was
effectively doubled within 1 °C around LCST in pH 9 buffer solution,
thus showing a dramatic pH and thermal dual-dependent property. The
FNPs exhibited reversible fluorescence enhancement/quenching over
more than five cycles, regardless of the heating/cooling process.
Furthermore, the FNPS proved to be much more stable to UV light irradiation
than pure fluorescence molecule AHBTA