Coatings consisting of Cu, especially those grown on frequently touched surfaces, are important tools to reduce fomite infections and improve public health. [2] In many hospitals and throughout public transportation systems, stainless steel is one of the most common materials due to its resistance to corrosion, appropriate mechanical properties, and processability. However, stainless steel does not have antimicrobial properties. An ideal disinfecting coating on stainless steels should be durable, safe, and easy to grow. These criteria, however, are challenging to be met simultaneously. For example, a high temperature and/or a high level of vacuum are often required to grow metallic Cu or its alloy on stainless steels, such as plasma spray, wire arc spray, and chemical vapor deposition. [3] Paintings of metallic Cu and Cu oxides particles composited with polymers may suffer from poor adhesion on the substrate, especially when considering the curved shape and fine finish of stainless steel used in those scenarios. Cu ions have also been investigated in coating techniques, such as those using zeolite, [4] laponite, [5] and polyanion [6] as the anchoring agents. Pre-loaded Cu ions can be released into the local aqueous environment of microorganisms to cause inactivation. However, these methods are currently limited to specific types of substrates and are not applicable to stainless steel.The challenge of growing an adherent coating on stainless steel is attributed to its chemical inertness. One way to overcome this is through surface reactions based on a strong oxidizing agent, such as KMnO 4 . This has been utilized for in situ synthesis of electrocatalyst, as reported by previous studies. [7] The reaction between KMnO 4 based precursor solution and stainless steel is spontaneous and self-limiting, leaving a thin and conformal oxyhydroxide surface layer. By adding Cu salts into the precursor solution, we developed a simple method to obtain a Cu-containing coating. It was found that Cu ions can leach from the coating, which may have caused the improved antibacterial activity compared to bare substrates. This solution-processing method can be applied to retrofit already-installed stainless steel parts, such as doorknobs and elevator buttons, with a conformal yet strongly adhering nanocoating for improved antibacterial properties.Stainless steels are widely used in hospitals and public transportation vehicles as one of the most common touch surfaces. Retrofitting stainless steel surfaces with an antimicrobial layer can bring potential public health benefits by reducing the ability of inanimate objects, or fomites, to transmit infections. Here, a facile surface conversion reaction between stainless steel and a solution of KMnO 4 and CuSO 4 is reported, which leads to a conformal and robust oxyhydroxide layer. Microscopy observations show that the layer is amorphous, continuous, and pinhole-free with a thickness of only 10-15 nm. The coating adheres strongly to stainless steel and can resist rubbing in simulated fricti...
