This study describes gold nanoparticle synthesis in an aqueous solution by reducing tetrachloroauric acid (HAuCl4), using sodium citrate as a reducing agent. Synthesis was optimized through an experimental design, and particle characterization was obtained through UV-Vis spectroscopy. In a first stage, a factorial design was conducted to establish the significance of the variables used in the synthesis, i.e. reducer concentration, temperature, stirring rate. In the second stage, the obtained nanoparticles were positioned on a silicon p-type substrate through electrophoretic deposition. The modified substrates were characterized by means of reflectance measurements and their morphology using transmission electron microscopy (TEM) and atomic force microscopy (AFM). Finally, a brief discussion was carried out concerning the sizes of the determined nanoparticles based on a model taken from the literature that relates maximum absorption with the nanoparticle diameter, comparing these with the sizes obtained through AFM and TEM observation.