Multifunctional nile red-triphenylamine AIEgen for optical waveguides, lipid droplet imaging, and photodynamic therapy

Aggregation-induced emission luminogens (AIEgens) have drawn significant interest as multifunctional materials, owing to their intense fluorescence in the aggregated state. However, developing an AIEgen that can simultaneously achieve optoelectronic and biological applications remains a significant challenge. Here, we design and synthesize a novel AIE-active molecule, NR-TPA, with a D-π-A structure that emits in the deep-red/near-infrared (DR/NIR) region by introducing triphenylamine (TPA) as the electron donor into a Nile Red (NR) scaffold. Benefiting from its photophysical properties, NR-TPA demonstrates outstanding potential in optical waveguide, lipid droplet (LD) imaging, and photodynamic therapy (PDT). NR-TPA self-assembles into red needle-like crystalline microcrystals that function as optical waveguides with a low loss coefficient of 0.222 dB mm⁻¹. Upon self-assembly with DSPE-PEG2000, NR-TPA forms stable nanoparticles (NPs) with bright fluorescence suitable for LD imaging in living cells. Moreover, the NR-TPA NPs can also generate abundant reactive oxygen species (ROS) under white light irradiation, enabling their application in PDT with minimal dark toxicity. This work highlights a versatile molecular design strategy for constructing AIEgens with combined photonic and biomedical functionalities, and demonstrates the promise of NR-based AIEgens for advanced optical and therapeutic applications.