## 4 Conclusions  
In this paper we report the use of _Sargassum_ extract to synthesize silver nanoparticles. By varying the different parameters, such as the solvent used to make the extract, the volumetric ratio of extract to precursor salt (AgNO\({}_{3}\)), and the pH, a synthesis route was defined. The _Sargassum_ extract obtained with the water-ethanol mixture was shown to contain a higher content of organic compounds that act as reducing agents and stabilizers for the synthesis of AgNPs. Variation in the volume of the extract can improve the synthesis of nanoparticles. Finally, alkaline conditions favor the synthesis of uniform and monodisperse nanoparticles. From the results, it is seen that green synthesis provides monodispersed polyhedral nanoparticles of around 26 nm (\(\pm\)2 nm) and high stability (confirmed by zeta potential), with a concentration of 2.23 mg/mL. This good size homogeneity and lack of agglomeration are outstanding and, following evaluation of their catalytic and antibacterial activity, show better performance than those obtained by chemical synthesis, despite their smaller sizes and higher concentration, 11.55 nm and 3.8 mg/mL, respectively. In conclusion, algae-based synthesized AgNPs have excellent antibacterial and catalytic activity and are cheap, practical, sustainable, widely available, and environmentally  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{_S. aureus_} & \multicolumn{2}{c}{_P. aeruginosa_} \\  & \multicolumn{2}{c}{**(Mean AA \(\pm\) SD)**} & \multicolumn{2}{c}{**(Mean AA \(\pm\) SD)**} \\ \hline  & **t = 1 h** & **t = 24 h** & **t = 1 h** & **t = 24 h** \\ \hline \multicolumn{4}{c}{**AgNPs-S**} \\ \multicolumn{4}{c}{**(Concentration \(\mu\)g/mL)**} \\ \hline
1000 & 73.71 \(\pm\) 9.0 & 99.66 \(\pm\) 0.3 & 65.85 \(\pm\) 8.5 & 99.95 \(\pm\) 1.0 \\ \hline
500 & 58.85 \(\pm\) 4.2 & 99.33 \(\pm\) 0.6 & 54.85 \(\pm\) 8.0 & 99.71 \(\pm\) 1.5 \\ \hline
250 & 48.75 \(\pm\) 9.5 & 98.23 \(\pm\) 2.7 & 32.85 \(\pm\) 6.5 & 99.85 \(\pm\) 0.5 \\ \hline
125 & 41.28 \(\pm\) 4.5 & 98.33 \(\pm\) 1.5 & 74.57 \(\pm\) 6.0 & 99.71 \(\pm\) 1.5 \\
62.5 & 38.42 \(\pm\) 5.5 & 98.33 \(\pm\) 2.0 & 10.00 \(\pm\) 9.0 & 99.85 \(\pm\) 0.5 \\ \hline \multicolumn{4}{c}{**AgNPs-C**} \\ \multicolumn{4}{c}{**(Concentration \(\mu\)g/mL)**} \\ \hline
1000 & 92.28 \(\pm\) 6.0 & 99.95 \(\pm\) 0.2 & 94.42 \(\pm\) 1.5 & 99.99 \(\pm\) 0.2 \\
500 & 78.28 \(\pm\) 9.0 & 99.99 \(\pm\) 0.1 & 93.71 \(\pm\) 3.0 & 99.71 \(\pm\) 1.5 \\
250 & 67.71 \(\pm\) 4.0 & 99.90 \(\  
safe. The synthesized nanoparticles could be of great use in various fields, such as the chemical and textile industries, and especially in environmental remediation. Conceptualization, J.L.L.-M., R.E., M.A.G.-R., B.L.E.-S., A.R.H.-M., R.S. and M.E. ; methodology, J.L.L.-M., R.E., M.A.G.-R., B.L.E.-S., A.R.H.-M. and M.E. ; validation, J.L.L.-M., R.E., M.A.G.-R., B.L.E.-S., A.R.H.-M. and M.E. ; resources, M.E. ; writing--original draft preparation, J.L.L.-M., R.E., M.A.G.-R., B.L.E.-S., A.R.H.-M., R.S. and M.E. ; writing--review and editing, R.E., and M.E. ; visualization, J.L.L.-M., M.A.G.-R. and B.L.E.-S.; supervision, M.E. ; project administration, M.E. ; funding acquisition, R.S. All authors have read and agreed to the published version of the manuscript. Not applicable. The data presented are available in this same study, _Sargassum_ Influx on the Mexican Coast: A Source for Synthesizing Silver Nanoparticles with Catalytic and Antibacterial Properties. The authors are grateful to SENER-CONACYT for the funding of this research through the CEMIE-Oceano project. Thanks also go to the Laboratorio Nacional de Caracterizacion de Materiales \"LaNCaM\" at the CFATA-UNAM. Thanks to technicians [PERSON] and [PERSON] of the UNAM Juriquilla Campus for their technical support, to the Servicio Academico de Monticro Meteorologico y Oceanografico (SAMMO) of the Academic Unit of Reef Systems Puerto Morelos (UASAPM) of the ICML of UNAM, and to [PERSON], [PERSON], and [PERSON] for collecting and sending the samples of Sargasso.