## 4 Discussion  
The mechanism surrounding the green synthesis of AgNPs using plants usually involves the preparation of nanoparticles by mixing the plant extract and silver salt solutions in different proportions, for different stirring times and at certain pH and temperature values. When exposed to plant compounds, Ag\({}^{+}\) is reduced to Ag\({}^{0}\), followed by the formation of oligomeric clusters and AgNPs synthesis [38]. Thus, silver ions suffer a bioreduction process that is believed to be due to biomolecules found in plant extracts (e.g., polyphenols, flavonoids, polysaccharides), being eventually transformed into colloidal silver which will form aggregates. Such aggregates will eventually stabilize through the attachment of biocompounds from the medium to their surface [35,39]. The decrease in the content of phenolic compounds found in the supernatant obtained after separation of AgNPs compared to that of the initial extract indicates the importance such polyphenols play in the synthesis of nanoparticles. The optimization of the synthesis demonstrated that, in the case of _T. eercta_ aqueous extract, the most suitable reaction conditions for AgNPs obtaining were: pH 8, 3 mM AgNO\({}_{3}\) solution, extract:AgNO\({}_{3}\) ratio of 1:9, 40 \({}^{\circ}\)C temperature, and stirring time of 75 min. In the case of the ethanolic extract, the most suitable reaction conditions for obtaining AgNPs were similar, the only difference being noticed regarding the optimal extract: AgNO\({}_{3}\) volume ratio which was 5:5 in the latter case. Regarding FTIR analysis, absorption bands in extracts were also visible in their derived AgNPs spectra, in some cases being attenuated or shifted, suggesting the attachment of functional groups from the extract compounds to the nanoparticles' surface. IR spectra of the extracts and their derived AgNPs indicate that polyphenols and flavonoids are the major compounds involved in the biosynthesis of nanoparticles, having also a role as capping agents [40,41]. The EDX analysis showed a dominant peak at 3 KeV, that is typical for AgNPs, and demonstrates the presence of silver in the synthesized nanoparticles and, implicitly, of the SPR band. In the case of AgNPs-H\({}_{2}\)O, a stronger signal is observed compared to AgNPs-EtOH. This could be explained by a better reduction of silver ions to elemental silver in the first case [42]. Moreover, the signals corresponding to other elements are much lower for AgNPs-H\({}_{2}\)O, compared to AgNPs-EtOH. This could be explained by the presence of \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Samples/Standards**} & \multicolumn{3}{c}{**Diameter of Inhibition Zones (mm) \(\pm\) SD**} \\ \cline{2-4}  & _Staphylococcus aureus_ & _Pseudomonas aeruginosa_ & _Candida albicans_ \\  & **ATCC 25923** & **ATCC 27853** & **ATCC 27853** \\ \hline Aqueous extract & 14.0 \(\pm\) 0.00 & NA * & 13.0 \(\pm\) 0.00 \\ \hline Ethanolic extract & 14.0 \(\pm\) 0.00 & NA * & 12.0 \(\pm\) 0.00 \\ \hline AgNPs-H\({}_{2}\)O & 14.0 \(\pm\) 0.00 & NA * & 14.0 \(\pm\) 0.00 \\ \hline AgNPs-EtOH & 14.0 \(\pm\) 0.00 & NA * & 20.0 \(\pm\) 0.00 \\ \hline Ciprofloxacinacin & 30.0 \(\pm\) 0.00 & 30.3 \(\pm\) 0.57 & * NT \\ \hline Fluconazole & NT * & NT ** & 29.0 \(\pm\) 0.00 \\ \hline \hline \end{tabular}  
*NA—no activity detected; ** NT—not tested.  
\end{table} 
Table 3: Antimicrobial activity of the plant extracts and of the corresponding AgNPs. photochemical compound in higher amounts on the surface of AgNPs-EtOH compared to that of AgNPs-H\({}_{2}\)O, taking into consideration that the plant's secondary metabolites act not only as reducing agents, but also as coating agents for AgNPs [43]. When analyzing the obtained TEM images, AgNPs-H\({}_{2}\)O presented reduced dimensional uniformity. In contrast, AgNPs-EtOH had a more pronounced spherical shape than that of AgNPs-H\({}_{2}\)O, and showed good dimensional uniformity, close to the average diameter of AgNPs-H\({}_{2}\)O.