Efficient PET-RAFT polymerization achieved by using low-toxicity shortwave infrared CuInSe₂/CuInS₂ quantum dots

Photoinduced electron/energy transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization enables precise light-controlled polymer growth. Traditional near-infrared strategies often rely on nonlinear optical processes such as two-photon absorption or photon upconversion, which typically require high-intensity laser excitation.

Direct shortwave infrared (SWIR) light-driven PET-RAFT has distinct advantages such as higher selectivity, deeper tissue penetration, and potential applications in three-dimensional printing and transdermal polymerization. However, efficient photocatalysts that can directly utilize SWIR photons remain rare.

In a study published in the Journal of the American Chemical Society, a team led by Prof. Wu Kaifeng and Prof. Du Jun from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, along with Prof. Cyrille Boyer from the University of New South Wales, achieved living radical polymerization using low-toxicity copper indium selenide (CuInSe₂) quantum dots (QDs), extending PET-RAFT excitation into the SWIR region at 1,050 nm.

Researchers synthesized highly luminescent CuInSe₂/CuInS₂ QDs with an absorption onset extended to 1,100 nm, and hybridized them with 4-Cyano-4-(dodecylsulfanylthiocarbonyl)sulfanylpentanoic acid as a photocatalyst. Under 1,050 nm excitation, this hybrid system effectively triggered PET-RAFT polymerization, achieving efficient polymerization through 3 mm of biological tissue.

Furthermore, researchers revealed that long-lived shallow defect-state electrons in CuInSe₂ QDs played a key role during organic photochemical reactions, providing guidance for the development of high-performance SWIR photocatalysts.

“With further optimization of QDs, this strategy could enable efficient polymerization at even longer wavelengths, paving the way for SWIR-driven synthesis of advanced functional polymer materials,” said Prof. Du.