A laboratory experiment in which students synthesize Ag, Au, and Pt nanoparticles (NPs) and use them to modify screen printed carbon electrodes for the electroanalysis of the hydrogen peroxide content in commercially available teeth whitening strips is described. This experiment is designed for two 3-h laboratory periods and can be adapted for upper-division undergraduate students in instrumental analysis, materials science, or physical chemistry laboratories. The experiment presented has already been used as a hands-on component in a Functional Nanomaterials Course, which exposed students to the analysis of the electrochemical properties of metal nanoparticles. Moreover, it allows for teaching the basics of nanoparticle synthesis and enables students to learn the fundamentals of electrochemical sensing with nanostructured materials.