Silver nanomaterials (AgNMs) have been applied as antibacterial agents to combat bacterial infections that can cause disease and death. The antibacterial activity of AgNMs can be improved by increasing the specific surface area, so significant efforts have been devoted to developing various bottom-up synthesis methods to control the size and shape of the particles. Herein, we report on a facile heat-treatment method that can improve the antibacterial activity of transparent silver nanowire (AgNW) films in a size-controllable, top-down manner. AgNW films were fabricated via spin-coating and were then heated at different temperatures (230 and 280 °C) for 30 min. The morphology and the degree of oxidation of the as-fabricated AgNW film were remarkably sensitive to the heat-treatment temperature, while the transparency was insensitive. As the heat-treatment temperature increased, the AgNWs spontaneously broke into more discrete wires and droplets, and oxidation proceeded faster. The increase in the heat-treatment temperature further increased the antibacterial activity of the AgNW film, and the heat treatment at 280 °C improved the antibacterial activity from 31.7% to 94.7% for Staphylococcus aureus, and from 57.0% to 98.7% for Escherichia coli. Following commonly accepted antibacterial mechanisms of AgNMs, we present a correlation between the antibacterial activity and surface observations of the AgNW film.

To combat infectious diseases, zinc oxide (ZnO) has been identified as an effective antibacterial agent; however, its performance can be adversely affected by harsh application environments. The ozone impact on ZnO antibacterial film needs to be evaluated prior to its application in an ozone disinfection system. In this study, ZnO films synthesized via sol-gel/spin-coating were subjected to ultraviolet–ozone (UVO) treatment for different periods. Surface investigations using scanning electron microscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy revealed that the treatment-induced film changes. With longer UVO treatment, the surface porosity of the film gradually increased from 5% to 30%, causing the transmittance reduction and absorbance increase in visible-light range. Phase transformation of Zn(OH)₂ to ZnO occurred during the first 10 min of UVO treatment, followed by oxygen uptake as a consequence of the reaction with reactive oxygen species generated during UVO treatment. However, despite these surface changes, the satisfactory antibacterial activity of the synthesized ZnO film against Staphylococcus aureus and Escherichia coli was sustained even after 120 min of UVO treatment. This indicates that the UVO-induced surface changes do not have a significant effect on the antibacterial performance and that the ZnO sol-gel film possesses good functional durability in ozone environments.

Cross-infection following cross-contamination is a serious social issue worldwide. Pathogens are normally spread by contact with germ-contaminated surfaces. Accordingly, antibacterial surface technologies are urgently needed and have consequently been actively developed in recent years. Among these technologies, biomimetic nanopatterned surfaces that physically kill adhering bacteria have attracted attraction as an effective technological solution to replace toxic chemical disinfectants (biocides). Herein, we introduce a transparent, colorless, and self-disinfecting polyethylene terephthalate (PET) film that mimics the surface structure of the Progomphus obscurus (sanddragon) wing physically killing the attached bacteria. The PET film was partially etched via a 4-min carbon tetrafluoride (CF₄) plasma treatment. Compared to a flat bare PET film, the plasma-treated film surface exhibited a uniform array structure composed of nanopillars with a 30 nm diameter, 237 nm height, and 75 nm pitch. The plasma-treated PET film showed improvements in optical properties (transmittance and B*) and antibacterial effectiveness over the bare film; the transparency and colorlessness slightly increased, and the antibacterial activity increased from 53.8 to 100% for Staphylococcus aureus, and from 0 to 100% for Escherichia coli. These results demonstrated the feasibility of the CF₄ plasma-treated PET film as a potential antibacterial overcoating with good optical properties.

Electron beam (EB) curing is a foldable hard coating process and has attracted significant research attention in the field of flexible electronic devices. In this study, we report a method for enhancing material surface hardness with low-energy EB curing in a short time. The low-energy EB improved the coating hardness of films by inducing cross-linking polymerization of the silicon-containing monomer. The hardness of the cured coating layer was measured as 3 H using a pencil hardness tester, and the transparency of the coating was higher than 90%. Owing to a series of cross-linking reactions between Si–O–C and Si–OH groups under EB curing and the formation of Si–Si bonds, the cured layer exhibited remarkable durability in the 100000-flexible cycle test. Additionally, the natural oxidation of the C–O groups on the surface of the coating formed carboxyl groups that improved the hydrophilic properties of the coating layer. To the best of our knowledge, this is the first study to propose that the hardness of polyethylene terephthalate films can be improved using low-energy EBs to rapidly cure silicon-containing coatings. Our results provide a novel and commercially viable approach for improving the hardness of touch screens and foldable displays.