The short wave near-infrared fluorescence properties of two p-azaquinodimethane (p-AQM)-based conjugated polymers

Abstract

The absorption, scattering, and autofluorescence of biological tissues in short-wave infrared region (SWIR, 900–1700[Formula: see text]nm) are relatively low, so SWIR fluorescence usually has deeper penetration into living tissues, and can show a higher signal-to-noise ratio when used for imaging in vivo. However, there are few types of organic SWIR fluorescent materials currently. In this work, [Formula: see text]-azaquinodimethane ([Formula: see text]-AQM) with a quinoid structure is used as the acceptor unit, and carbazole or fluorene with sp3 hybridization are used as the donor units, two conjugated polymers were synthesized. The quinone structure is conducive to the redshift of absorption and fluorescence spectra, and the sp3 hybridization structure is conducive to weakening the aggregation quenching of polymer fluorescence. PF and PCz exhibited absorption peaks of 492[Formula: see text]nm and 508[Formula: see text]nm, respectively. The emission peaks of the two polymers are 920[Formula: see text]nm and 950[Formula: see text]nm, respectively, both in the short-wave near infrared region. The quantum yield (QY) of PF and PCz is 0.4% and 0.3%, respectively.