ARC Centre of Excellence in Exciton Science, School of Physics, University of New South Wales, Sydney, Australia.
School of Chemistry, University of New South Wales, Sydney, Australia.
Angew Chem Int Ed Engl. 2023 May 8;62(20):e202301678. doi: 10.1002/anie.202301678. Epub 2023 Apr 12.
Polydopamine (PDA) is a synthetic model for melanin and has a wide range of opto-electronic properties that underpin its utility in applied and biological settings, from broadband light absorbance to possessing stable free radical species. Here, we show that PDA free radicals are photo-responsive under visible light irradiation, enabling PDA to serve as a photo-redox catalyst. Steady-state and transient electron spin resonance spectroscopy reveals a reversible amplification in semiquinone radical population within PDA under visible light. This photo-response modifies the redox potential of PDA and supports sensitisation of exogenous species via photoinduced electron transfer (PET). We demonstrate the utility of this discovery by employing PDA nanoparticles to photosensitise a common diaryliodonium photoinitiator and initiate free-radical polymerisation (FRP) of vinylic monomers. In situ H nuclear magnetic resonance spectroscopy reveals an interplay between PDA-driven photosensitising and radical quenching during FRP under blue, green, and red light. This work provides crucial insights into the photoactive free radical properties of melanin-like materials and reveals a promising new application for polydopamine as a photosensitiser.
聚多巴胺（PDA）是一种合成的黑色素模型，具有广泛的光电性能，使其在应用和生物环境中具有实用性，从宽带光吸收到具有稳定的自由基种类。在这里，我们表明 PDA 自由基在可见光照射下具有光响应性，使 PDA 能够充当光氧化还原催化剂。稳态和瞬态电子自旋共振光谱揭示了可见光下 PDA 中半醌自由基种群的可逆放大。这种光响应改变了 PDA 的氧化还原电位，并通过光诱导电子转移（PET）支持外源物质的敏化。我们通过使用 PDA 纳米粒子敏化常见的二芳基碘鎓光引发剂并引发乙烯基单体的自由基聚合（FRP）来证明这一发现的实用性。原位 1 H 核磁共振光谱揭示了在蓝、绿、红光下 FRP 过程中 PDA 驱动的光致敏化和自由基猝灭之间的相互作用。这项工作为黑色素样材料的光活性自由基性质提供了重要的见解，并揭示了聚多巴胺作为光敏剂的有前途的新应用。
