Enhancing Photophysical and Photosensitizing Properties of Nanoaggregates of Weakly Emissive Non-Planar Push-Pull Chromophore

The development of luminescent dye based on 1,1,4,4-tetracyanobuta-1,3-dienes (TCBDs) is an active research area, to date, only a few examples of designer TCBDs molecules displaying emission properties with quantum yields of 7.8 and 8.5% due to fluorophore conjugation and aggregation have been reported, both in organic, non-polar solvents. Our novel method radically refines weakly emissive 2,3-disubstituted TCBD (phenyl-TCBD 1) (ΦF = 2.3% in CH3CN) into a water-soluble, biocompatible nano-formulation as highly emissive aggregates 1NPsPF-127 with ΦF = 7.9% in H2O and without fluorophore conjugation. Spectroscopic studies including FT-IR revealed that aggregated phenyl-TCBD particles were encapsulated in a non-luminescent tri-block copolymer (PF-127) based nano-micelle. With increasing water fraction, the Phenyl-TCBD nano-aggregates exhibit a 3-fold higher quantum yield, greater lifetime, and redshift (155 nm). Singlet oxygen generation capability was tested to explore future studies as a bio-probe for bio-imaging applications and in photodynamic therapy to selectively target cancer cell lines with singlet oxygen generation (Φ= 0.25) capability. This study has significant implications for developing non-planar push-pull chromophores-based dyes as biosensors and their potential applications beyond bioimaging.