## 2 Materials and Methods  
### Materials  
Silicon dioxide (SiO\({}_{2}\)) nanoparticles were coated with the KH570-Silane coupling agent; both these materials were obtained from Nanografi Inc. (Cankaya/Ankara, Turkey; [[https://nanografi.com/](https://nanografi.com/)]([https://nanografi.com/](https://nanografi.com/))). The properties of the nanoparticles together with some data coming from an elemental analysis of nanoparticles coated with the above-indicated coupling agent are shown in Tables 1 and 2, respectively. The molecular structure of the silane-coupling agents (3-Methacryloxypropyltrimethoxy silane) is presented in Figure 1 and the chemical formula of KH570 is CH\({}_{3}\)CCH\({}_{2}\)COO(CH\({}_{2}\))\({}_{3}\)Si(OCH\({}_{3}\))\({}_{3}\)[33]. It has a molecular mass equal to 248.351 g\(\cdot\)mol\({}^{-1}\). The designation given to this particular silane coupling agent is shorter than IUPAC designation because it is only a reference within producers' product lines, so letters (KH) and numbers (570) do not have any specific meaning beyond serving as an identifier for this product. Mistral 15W40 lubricant and PLANTO MOT SAE 10W40 biolubricant were supplied from NILS S.p.A ([[https://www.nils.eu/](https://www.nils.eu/)]([https://www.nils.eu/](https://www.nils.eu/))) and FUCHS LUBRICANTS GERMANY GmbH ([[https://www.fuchs.com/de/en/](https://www.fuchs.com/de/en/)]([https://www.fuchs.com/de/en/](https://www.fuchs.com/de/en/))), respectively. In Table 3, the technical characteristics of the lubricant and biolubricant are presented separately. The scientific methods utilizedin this research include: viscometric analysis, FTIR spectroscopy, UV-Vis spectrophotometry, and ICP-OES analysis. The standards referenced in the measurements are provided by the American Society for Testing and Materials (ASTM) International ([[https://www.astm.org/](https://www.astm.org/)]([https://www.astm.org/](https://www.astm.org/))) and the International Organization for Standardization (ISO; [[https://www.iso.org/](https://www.iso.org/)]([https://www.iso.org/](https://www.iso.org/))). The techniques encompass a two-step preparation of nanolubricants and nanobiolubricants, magnetic stirring, ultrasonic cleaning, and sedimentation photography. The employed analyses are: kinematic viscosity measurements, viscosity index calculation, density measurement, TAN and TBN titration, and elemental analysis. The software used includes the instrument-specific software for the Anton Paar SVM 3001 kinematic viscometer (Anton Paar GmbH, Graz, Austria; [[https://www.anton-paar.com/](https://www.anton-paar.com/)]([https://www.anton-paar.com/](https://www.anton-paar.com/))), the Mettler Toledo T50 titrator (Mettler-Toledo International Inc., Columbus, OH, USA; [[https://www.mt.com/](https://www.mt.com/)]([https://www.mt.com/](https://www.mt.com/))), the Perkin Elmer OPTIMA 8000 ICP-OES (PerkinElmer Inc., Waltham, MA, USA; [[https://content.perkinelmer.com/](https://content.perkinelmer.com/)]([https://content.perkinelmer.com/](https://content.perkinelmer.com/))), the Perkin Elmer Spectrum 100 FTIR (PerkinElmer Inc., Waltham, MA, USA; [[https://content.perkinelmer.com/](https://content.perkinelmer.com/)]([https://content.perkinelmer.com/](https://content.perkinelmer.com/))), and the Agilent Cary 100 UV-Visible Spectrophotometer (Agilent Technologies Inc., Santa Clara, CA, USA; [[https://www.agilent.com/](https://www.agilent.com/)]([https://www.agilent.com/](https://www.agilent.com/))). All research activities were conducted in the university laboratory of the Free University of Bozen-Bolzano. \begin{table}
\begin{tabular}{l c c} \hline
**Technical Property** & **Unit of Measurement** & **Value** \\ \hline Purity & \% & 95.9+ \\ Colour & – & white \\ Particle shape & – & amorphous \\ Average Particle Size & nm & 18–35 \\ Specific Surface Area & m\({}^{2}\cdot\)g\({}^{-1}\) & 150–550 \\ Bulk Density & g\(\cdot\)cm\({}^{-3}\) & \(<\)0.1 \\ True Density & g\(\cdot\)cm\({}^{-3}\) & 2.2 \\ \hline \end{tabular}
\end{table}