Water-Based Scalable Methods for Self-Cleaning Antibacterial ZnO-Nanostructured Surfaces

Abstract

Bacterial colonization poses significant health risks, such as infestation of surfaces in biomedical applications and clean water unavailability. If maintaining the surrounding water clean is a target, developing surfaces with strong bactericidal action, which is facilitated by bacterial access to the surface and mixing, can be a solution. On the other hand, if sustenance of a surface free of bacteria is the goal, developing surfaces with ultralow bacterial adhesion often suffices. Here we report a facile, scalable, and environmentally benign strategy that delivers customized surfaces for these challenges. For bactericidal action, nanostructures of inherently antibacterial ZnO, through simple immersion of zinc in hot water, are fabricated. The resulting nanostructured surface exhibits extreme bactericidal effectiveness (9250 cells cm –2 h –1 ) that eliminates bacteria in direct contact and also remotely through the action of reactive oxygen species. Remarkably, the remote bactericidal action is achieved without the need for any illumination, otherwise required in conventional approaches. As a result, ZnO nanostructures yield outstanding water disinfection of >99.98%, in the dark, by inactivating the bacteria within 3 h. Moreover, Zn 2+ released to the aqueous medium from the nanostructured ZnO surface have a concentration of 0.73 ± 0.15 ppm, markedly below the legal limit for safe drinking water (5–6 ppm). The same nanostructures, when hydrophobized (through a water-based or fluorine-free spray process), exhibit strong bacterial repulsion, thus substantially reducing bacterial adhesion. Such environmentally benign and scalable methods showcase pathways toward inhibiting surface bacterial colonization.

Past and Current Progress in the Development of Antiviral/Antimicrobial Polymer Coating towards COVID-19 Prevention: A Review

“…Another attempt at superhydrophobic self-cleaning surface fabrication was made by Milionis’ group [ 155 ]. They introduced two different hydrophobic layers, water-soluble fluoroalkylsilane (FAS) and ethanol-soluble stearic acid (SA), over zinc oxide nanostructure surfaces.…”

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“…[17] Metallic surfaces in condensers, such as steel, aluminum or copper, are typically hydrophilic and DWC can be achieved on such surfaces by applying hydrophobic coatings. Numerous such coatings have been developed along with a range of coating techniques, including selfassembled monolayers (SAMs), [18,19] spraying, [20] physical (PVD) [21] and chemical vapor deposition (CVD). [22] However, these coatings need to address a number of conflicting challenges namely optimal wettability for efficient shedding of condensate, low thermal resistance, long-term mechanical durability, and scalability of the fabrication process.…”

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“…Similar to Cu, Zn is also biocidal, and the toxicity of ZnO nanoparticles to Gram-positive and -negative bacteria and viruses is well-studied. [38],[39] When bacteria are exposed to ZnO nanoparticles, biocidal Zn 2+ ions are released, which destroy the bacteria cell wall and generates ROS. [38,40–42] In addition, NP3 coatings had the least amount of metallic Cu.…”