Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

Abstract

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 1H 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.

Understanding the Photothermal and Photocatalytic Mechanism of Polydopamine Coated Gold Nanorods

“…[ 34 ] Moreover, PDA possesses a high molar extinction coefficient, leading to an outstanding light absorption ability and the capability of producing ROS under visible radiation. [ 11,57,71,83 ] More importantly, our experiments have shown that the production of OH and O 2 − is higher when visible light is used and by enhancing the production of ROS, specially OH, through carboxylation and dealkylation (Figure 5c). Our TA experiments confirmed that the hot charges generated in AuNRs can be transferred to PDA on the ultrafast time scale of single ps, competing with the charge thermalization processes in gold.…”

“…A few previous studies have shown that PDA plays an electron scavenging role, [ 11 ] and some studies have shown that due to the S‐scheme heterojunction formed between PDA and semiconductors, electrons are quickly transferred and stored in the PDA layer for further chemical interactions. [ 57 ] Though no metal/PDA interface has been studied, our experiments suggest that similar behavior is present at the Au/PDA interface.…”

“…Gold nanoparticles (AuNPs) and gold nanorods (AuNRs) have been recently applied in several fields, such as optics, electrochemistry, biological sensing, [ 6 ] and catalysis. [ 7–11 ]…”

“…Gold nanoparticles (AuNPs) and gold nanorods (AuNRs) have been recently applied in several fields, such as optics, electrochemistry, biological sensing, [6] and catalysis. [7][8][9][10][11] AuNPs and AuNRs have recently been combined with the biomimetic polymer polydopamine (PDA), with promising results for photocatalysis. Au/PDA composites on glass substrates (Au/PDA@slide) have been proven to photodegrade methyl orange and reduce 4-nitrophenol at room temperature with NaBH 4 as a reducing agent.…”

Self-driven immune checkpoint blockade and spatiotemporal-sensitive immune response monitoring in acute myeloid leukemia using an all-in-one turn-on bionanoprobe

“…Among them, polydopamine (PDA) nanoparticles produced from brain secretion have the advantages of mild synthesis conditions, feasibility for surface modification, good optical absorption, and degradability, which facilitates their important role in drug delivery and tumor photothermal therapy in recent years. 17–20 However, approaches to combine its pharmacokinetics advantages with the activation of biomolecules to achieve a more comprehensive capability on simultaneous tracking of therapy efficiency are less explored.…”