Polydopamine surface modification with UV-shielding effect using KMnO₄ as an efficient oxidizing agent

Over the last decade, polydopamine (PDA) has attracted significant attention due to its material-independent coating ability, process simplicity, and its powerful capabilities for ad-layer formation. However, its long coating time (24 h) has limited its application in industrial scale. To address this issue, oxidants such as (NH₄)₂S₂O₈ CuSO₄ and NaIO₄ were introduced to enhance the coating kinetically. Although NaIO₄, among all the oxidants, was reported as the most efficient one, its high stoichiometric ratio of 2 between the oxidant and dopamine makes it costly and less attractive. Here, KMnO₄ is introduced as a new water-soluble oxidant which can substantially reduce the PDA coating to few minutes in a single reaction process with a chance to adjust its thickness without losing PDA intrinsic modification capability. At a KMnO₄/dopamine ratio of 0.4, a coating speed of 750 nm/h was achieved, which is 25 times higher than that of NaIO₄ at similar oxidant/dopamine ratio. The KMnO₄-assisted PDA coating was utilized to introduce an efficient and inexpensive method to convert glass materials to surfaces with durable UV shielding property. Finally, the reducibility and ad-layer formation ability of PDA layer were used to develop silver, copper, and ZIF8 composite PDA layer to adjust the UV protection level.