*Article* **Antibacterial Properties of Zn Doped Hydrophobic SiO2 Coatings Produced by Sol-Gel Method**

#### **Bo ˙zena Pietrzyk \*, Katarzyna Por ˛ebska, Witold Jakubowski and Sebastian Miszczak**

Institute of Materials Science and Engineering, Faculty of Mechanical Engineering, Lodz University of Technology, Stefanowskiego Str. 1/15, 90-924 Lodz, Poland; katka.porebska@gmail.com (K.P.); witold.jakubowski@p.lodz.pl (W.J.); sebastian.miszczak@p.lodz.pl (S.M.)

**\*** Correspondence: bozena.pietrzyk@p.lodz.pl; Tel.: +48-42-6313043

Received: 6 May 2019; Accepted: 29 May 2019; Published: 1 June 2019

**Abstract:** Bacteria existing on the surfaces of various materials can be both a source of infection and an obstacle to the proper functioning of structures. Increased resistance to colonization by microorganisms can be obtained by applying antibacterial coatings. This paper describes the influence of surface wettability and amount of antibacterial additive (Zn) on bacteria settlement on modified SiO2-based coatings. The coatings were made by sol-gel method. The sols were prepared on the basis of tetraethoxysilane (TEOS), modified with methyltrimethoxysilane (MTMS), hexamethyldisilazane (HMDS) and the addition of zinc nitrate or zinc acetate. Roughness and surface wettability tests, as well as study of the chemical structure of the coatings were carried out. The antibacterial properties of the coatings were checked by examining their susceptibility to colonization by *Escherichia coli*. It was found that the addition of zinc compound reduced the susceptibility to colonization by *E. coli*, while in the studied range, roughness and hydrophobicity did not affect the level of bacteria adhesion to the coatings.

**Keywords:** SiO2 coatings; sol-gel; Zn doping; antibacterial coatings; hydrophobic coatings; wettability
