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.