2.2 Preparation and characterization of THB@ANVs
2.2.1 Characterization of4-(2-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)vinyl)-1-(2-hydroxyethyl)
pyridin-1-ium bromide
(THB)
Pyridinium moiety-containing red
light AIEgens with π-conjugation structures have been shown to exhibit a
distinct enhancement of ROS generation capacity induced by aggregation,
making them a promising option for photodynamic antibacterial
applications.[32] These positively charged AIEgens
require only natural sunlight or white light with equivalent energy
density to generate ROS [33,34]. Here, we designed
a hydroxypyridinium moiety containing water soluble THB, which is
expected to allow for better loading into and release from nanovesicles,
while achieving high antibacterial activity. The THB was synthetized by
facile organic reactions in high yield, and the structures of THB and
intermediates were characterized
by 1H and 13C
nuclear magnetic resonance
spectra and high-resolution mass
spectra (HRMS) (Figure S1~S5). As a hydrophilic molecule
that can be well dispersed in water, the aqueous solution of THB is
almost non-emissive. Thus, the AIE properties of THB were tested with
different volume percentage of hexane as poor solvent (Figure 1C and
1D). The photoluminescent (PL) intensities gradually increase and
bule-shifted with increasing fraction of hexane, due to the formation of
nanoaggregates. The enhanced emissions in aggregates could be attributed
to the restriction of rotor motions, which activate radiative decay
process. The maximum absorption of THB is 464 nm (Figure S6), while the
maximum emission in the aggregation state is located at 647 nm,
indicating its red-emission property and large Stokes shift.