2.9. Nanoparticle Characterization

Characterization was restricted to the identification of the shape and size of tea nanoparticles coated with PVA. Shape identification was carried out with an atomic force microscope (AFM) and a high-resolution transmission electron microscope (HRTEM). Their shapes and textures were scanned using a high-resolution transmission electron microscope with an accelerating voltage of 250 kV and magnification of 20×. Samples were prepared before measurement via sonicated irradiation using a sonication prop under the following conditions: increases every 3 s at 73% amplitude power and maximum temperature for 33 minutes. Finally, 40 microns were added to the TEM grade via air drying for 4.5 h [27]. The AFM had a study area of 300 nm × 300 nm and used an Al tip in contact mode and vacuum conditions. Thin film formation needed to be performed first via the free precipitation of the samples on mica plates [28]. The size was measured using dynamic light scattering (DLS). In DLS analysis, the sample suspension is illuminated by a laser beam, after which, the laser light scatters in all directions. The light scattering is observed at a certain angle over time. Signal variation is due to the random Brownian motion of the particles. Angular intensity distribution is used to determine the particle size via the Stokes–Einstein equation [29].