Iron-coated polymer films with high antibacterial activity under indoor and outdoor light, prepared by different facile pre-treatment and deposition methods

In the present work, we study the fabrication of self-cleaning antibacterial surfaces, active under indoor or outdoor light. In order to obtain the highest activity with the lowest complexity we assess mild conditions of preparation (temperatures), pre-treatment (physical, chemical) and deposition method (dip coating, spraying). We report that the combination of deposition time and temperature during this phase on PET can lead to effective germicidal films (< 40 min under solar light) and pre-treatment with simple sandpaper scratching or acetone dissolution increase the inactivation kinetics more than 35%. Spray coating always led to higher germicidal efficiencies, due to the differentiated layering during deposition, reaching total inactivation under either indoor or solar light. Furthermore, the non-pretreated films were very robust over 10 re-uses and the pre-treated ones led to virtually no loss of antibacterial activity. Other materials such as polyurethane (PU) and LDPE were effectively used, with pre-treated PU reaching the fastest inactivation (< 30 min). Finally, the costly Fe reagent was effectively replaced with natural Fe oxides, which were equally efficient in pre-treated surfaces. In overall, compared to real world conditions, a very high microbial load was eliminated, in either indoor or outdoor environments, meeting the demands where the infection problems are high and the means are scarce.