Selenadiazolobenzotriazole based near infrared dyes with enhanced intramolecular charge transfer and photothermal effect: Synthesis, characterization and photophysical properties

Near-infrared (NIR) dyes have shown increasing popularity for photothermal cancer therapy. Here, we report the synthesis and photophysical properties of selenadiazolobenzotriazole based organic small molecule NIR dyes SeNz and SeNzBr, both of which demonstrate strong intramolecular charge transfer and an excellent photothermal effect. Through self-assembly, hydrophilic nanoparticles (NPs) SeNz NPs and SeNzBr NPs were prepared by taking DSPE-PEG₂₀₀₀ as the polymer matrix and exhibited excellent photothermal conversion efficiency of 57.4% and 42.5%, respectively. In addition, both NPs displayed excellent photothermal stability and photostability. Furthermore, both NPs show low dark cytotoxicity and high phototoxicity by taking HeLa cells as the model. All results suggest that selenadiazolobenzotriazole based NIR dyes SeNz and SeNzBr are promising for photothermal therapy.