Construction of Through-Space Charge-Transfer Nanoparticles for Facilely Realizing High-Performance NIR-II Cancer Phototheranostics

Phototheranostics with second near-infrared (NIR-II) emissions show great potential for disease diagnosis and imaging-guided phototherapy owing to deep tissue penetration, high imaging resolution, and excellent tumor eradication. Recently, molecular conjugation engineering and J-aggregation have been used to construct organic NIR-II materials. However, these molecules generally have extensive conjugation and large molecular weight in the range of 700–1700 g mol⁻¹, requiring complicated molecular design and synthesis. Herein, a NIR-II emissive through-space charge-transfer (TSCT) nanoparticle (NP) using short-conjugated donor-acceptor (D-A) molecules (TTP) is reported for high-performance bioimaging and cancer phototheranostics. Owing to the short conjugation of the TTP molecule with a small molecular weight of only 518 g mol⁻¹, the TTP monomer possesses visible absorption and first near-infrared (NIR-I) emission. Upon forming NPs in water, the efficient TSCT between TTP monomers leads to significantly red-shifted absorption to the NIR-I and emission to the NIR-II region with a tail that extends to 1400 nm. TTP NPs are employed in NIR-II in vivo blood-vessel bioimaging and cancer phototheranostics successfully. This work introduces a facile strategy to construct NIR-II emissive NPs based on short-conjugated D-A molecules for high-performance biomedical applications. © 2024 The Author(s). Advanced Functional Materials published by Wiley-VCH GmbH.