## 1 Introduction  
Silica materials are a large group of functional materials with a wide range of applications [1]. They can be obtained in a polycondensation reaction from silicon alkoxides or other similar precursors using the sol-gel process. The final properties of the product depend on the process parameters such as type of precursor and solvent, catalyst, or temperature. This makes it an effective, simple, and cheap technology characterized by many advantages [2]. Silica-based coatings are one of such materials; they are largely developing and future-oriented because they can impart a wide variety of predetermined properties to a surface [3]. Silica coatings can be doped with various fillers or modifiers in order to improve or change their properties. This makes them a composite material. The composite is produced from two or more constituent materials with different physical and chemical properties [4]. Their combination results in a material with properties dissimilar to those of individual elements. When the two constituents are at the nanometer or molecular level, this is a hybrid material [5]. This combination, consisting of organic and inorganic constituents, makes an interesting material with specific physical, thermal, optical, electrical, and mechanical properties that are promising for various applications [6; 7]. Recently, the use of carbon nanotubes (CNTs) [8] has become more common, and they are now one of the most widely used organic additives due to their unique properties such as small density, excellent mechanical properties, and good thermal and electrical conductivity, which make them an ideal component for the organic phase in composites or hybrids [9; 10; 11; 12]. CNTs are cylindrical structures consisting of rolled-up sheets of single-layer carbon network with the structure (sp\({}^{2}\)) of graphene [13]. In the case of the single-walled carbon nanotubes (SWCNTs), this is a single sheet close to 1 nanometer in diameter [14], whereas for the multiwalled carbon nanotubes (MWCNTs), there are several concentrically interlinked single tubes, and the end diameter of the structure can reach up to 100 nm [15]. The length of nanotube ranges from nanometers, through millimeters, up to several centimeters [16]. The popularity of carbon nanotubes applications can be demonstrated by their usage not only for nanocomposites [17; 18] but also in many fields--for example, drug delivery systems [19], functional fabrics production [20], medicine [21], electronics [22], solar energy systems [23], road constructions [24], and even spacecrafts [25]. There is a quick and simple method to synthesize doped silica composites--mix an organic additive with one of the precursors (for example tetraethyl orthosilicate) followed by the sol-gel reaction assisted with acid or base catalysis [26]. The hydrogen bonds formed between the two constituents prevent phase separation and result in obtaining a transparent and stable composition or a film [27]. However, so far, there are no reports in the literature on the use of carbon nanotubes as a silica coating modifier, but they have been successfully used, for example, to produce composite polymer materials [28] or different types of hybrid materials [29]. Another possibility to modify the properties of the coatings is to modify the support with plasma. Plasma is commonly defined as a fourth state of matter, distinct from a solid, liquid, or gas, that is composed of high-energy ions, electrons, neutral or excited molecules, and UV light [30]. It was first described by the American chemist [PERSON] in the 1920s [31; 32]. It is crucial to distinguish between thermal and nonthermal (cold) plasmas, and the classification is based on the relative temperatures of their constituents.