## 2 Materials and Methods
### Plasma Source and Specimens' Treatment  
#### 2.2.1 Plasma-Processed Air (PPA) Generation and Plasma-Treated Water (PTW) Functionalization  
The functionalization of compressed air for PPA production for the PPA treatment of the _C. albicans_ inoculated PE strips was carried out with a microwave-driven discharge device [35; 36]. The setup used is shown in Figure 1A. The microwaves used had a frequency of 2.45 GHz with an input power of 1.1 kW, which results in a gas temperature of about 3500-4000 K at a gas flow of 18 slm air. By cooling the PPA to room temperature (20-25 \({}^{\circ}\)C), the functionalized gas could be used directly for the decontamination of the PE strips or for further functionalization of the water to PTW (Figure 1B). The given gas temperature was measured in pure nitrogen by optical emission spectroscopy (OES) using the first negative system of N\({}_{2}\)\({}^{+}\). This method is a common method for temperature measurements at high temperatures such as those found in arc jets or microwave torches and has been described in detail by [PERSON] et al. (2001) [37]. A temperature of about 4000 K was then calculated. Unfortunately, this method is not applicable in air plasmas due to the presence of oxygen. Therefore, an alternative method described in [PERSON] et al. (2008) was used [38]. Based on the OH spectrum between 300 nm and 320 nm, a temperature of 3000 K \(\pm\) 500 K is assumed. If the Fourier-transform infrared spectroscopy (FTIR) spectrum measured in the plasma outflow is taken into account [39] and compared with the chemical composition of the air plasma of the entire temperature range in [PERSON] (1978) [40], it becomes clear that the temperature of the plasma torch must be in the range of 3500 K-4000 K.  
The main chemical components of PPA are reactive nitrogen species (RNS) such as nitric oxide (NO), nitrogen dioxide (NO\({}_{2}\)), nitrous acid (HNO\({}_{2}\)) and nitric acid (HNO\({}_{3}\)) and water (H\({}_{2}\)O) [31; 39]. However, previous mass spectrometric investigations (OmniStar(tm) GSD3001O1, Pfeiffer Vacuum (Asslar, Germany)) [31] showed that 97% of the air used as working gas remained compressed air after microwave discharge treatment and cooling at the point of application, so that only 3% was functionalized to PPA [31]. As described in [31], a mass spectrometric analysis were done under atmospheric pressure. The plasma gas was fed through a heatable stainless steel capillary (inner diameter of 1/16\" and length of 1 m) into the chamber for analysis. A gas flow of 1 to 2 sccm was generated. The detection range of the mass spectrometer was 1 to 100 amu. The measurements and evaluations were performed with the software QuadStar(tm) (Pfeiffer Vacuum). Nitrogen dioxide (NO\({}_{2}\)) was measured by two different methods. The first is described in [33] in detail and is based on a self-constructed 'NO\({}_{2}\) sensor, which was calibrated by usage of test gas (Linde AG, Pullach, Germany: test gas 'NO\({}_{2}\) (3.19%) and synthetic air). The sensor is based on absorbance measurements of 'NO\({}_{2}\)-bands at 400 nm [41]. The second method is described in [39] in detail and is based on FTIR measurements. The FTIR (Vertex 70v, Bruker Cooperation, Billerica, MA, USA) was equipped with a variable long path cell, 0.25-1 m (Bruker Cooperation), which was calibrated for a path length of 0.25 m. In order to get species concentrations, the experimental data were processed by a MATLAB (The MathWorks Inc., Paderborn, Germany) code developed at our institute based on the  
Figure 1: Scheme of the microwave-setup for (**A**) the generation of PPA (plasma-processed air) and (**B**) the functionalization of PTW (plasma-treated water). spectroscopic data of the HITRAN database (High-Resolution Transmission molecular absorption database, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA). For the measurements, the microwave plasma device was connected directly to the long path cell via a 9-fold gas distributor.