## 3 Results and Discussion  
### Functionalization of HSAG  
The functionalization of HSAG was performed through the reaction with serinol pyrrole. As mentioned in the Introduction, the functionalization process is indeed simple and occurs through the domino reaction shown in Figure 3.  
Figure 1: Sketch of the specimen used for fracture tests, with notch length (\(a_{0}\)), thickness of the specimen (\(B\)), and width (\(W\)) and length (\(L_{0}\)) of the specimen. Figure 2: Experimental setup for fracture test: camera in front of the notch root, example of frames taken during a fracture test with the notch surfaces of a specimen. In particular, fracture initiation is indicated. Details about the reaction are provided in the Materials and Methods section. In brief, serinol pyrrole is obtained by simply mixing and heating the primary amine (serinol) and the dicarbonyl compound and functionalization occurs by simply mixing the pyrrole compound and the graphitic substrate, then heating the mixture at 180 \({}^{\circ}\)C for 3 h. The domino functionalization process occurs via the following steps: adsorption of the pyrrole compound onto the graphitic material, carbocatalyzed oxidation of SP, and cycloaddition reaction with the graphene layers. In this work, SP was obtained by performing the reaction between the diketone and serinol in a flask, isolating the product. However, as already reported [76], the reactants can be mixed on top of the sp\({}^{2}\) carbon allotrope. In this case, the first step of the domino process becomes the synthesis of the pyrrole compound. Such functionalization method avoids the above-mentioned harsh reaction conditions typically used for the traditional oxidation-reduction approach. In this work, two functionalization reactions were performed, with two HSAG/SP mass ratios: 10:1 and 10:0.6. The objective was to check the efficiency of the reaction by increasing the amount of the pyrrole compound. The efficiency of the functionalization reaction was evaluated by means of thermogravimetric analysis (TGA), as described in Materials and Methods, on the HSAG/SP adduct isolated after the reaction and an exhaustive acetone extraction, curves are reported in Figure 4. The detected mass losses are in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Sample**} & \multicolumn{4}{c}{**Mass Loss (\%)**} \\ \hline  & & **T \textless{} 150 \({}^{\circ}\)C** & **150 \({}^{\circ}\)C \textless{} T \textless{}** & **400 \({}^{\circ}\)C \textless{} T \textless{}** & **T \textgreater{} 700 \({}^{\circ}\)C** \\ \hline HSAG & (a) & 1.3 & 1.7 & 4.6 & 92.4 \\  & (c) & 0.0 & 0.1 & 0.4 & 99.5 \\ \hline HSAG-SP & & & & & \\ Sample 1 & (b) & 0.9 & 6 & 9.4 & 83.6 \\  & (c) & 1.0 & 5 & 8.5 & 85.5 \\ \hline HSAG-SP & & & & & \\ Sample 2 & & & & & \\  & (c) & 0.5 & 2.1 & 4.1 & 93 \\ \hline \hline \end{tabular} (a) Pristine (b) after the functionalization reaction (c) after washing with acetone (see Materials and Methods section).  
\end{table} 
Table 2: Mass losses for HSAG and HSAG-SP adduct, as detected from TGA analysis. Figure 3: Scheme of the domino reaction for the functionalization of HSAG with serinol pyrrole. Mass losses below 150 \({}^{\circ}\)C can be attributed to the removal of the adsorbed water. It is not revealed by washed pristine HSAG and increases with the amount of serinol pyrrole in the adduct. It is worth repeating (see Materials and Methods) that all the functionalization reactions were performed on washed HSAG samples. The mass loss at temperatures above 150 \({}^{\circ}\)C, for the washed sample of pristine HSAG can be attributed to alkenylic defects. In the case of HSAG/PyC adducts as well, mass loss is due to the presence of the organic modifier introduced with the functionalization reaction [69]. Such mass loss is indeed appreciable in the samples exhaustively extracted with acetone. Stable adducts were thus formed. The equation and procedure for estimating the functionalization yield was reported above in the Materials and Methods section.