Microstructural and optical properties of ZnO coatings from colloidal inks

Nanoparticles (NPs) and flake-like morphologies of zinc oxide (ZnO) were synthesized by colloidal and hydrothermal methods, respectively. The flake-like particle dimensions have 270 ± 60 nm average diameter and 47 ± 7 nm thickness, in the case of NPs that have 10 ± 2 nm as an average diameter. These two types of particles were used to formulate colloidal inks, using ethylene glycol as a dispersing medium. The inks were formulated with different percentages of particle content and their viscosity and sedimentation as a function of time were studied. ZnO coatings were obtained by the drop coating method for optimized ink formulated with 1 wt% of particle content, obtaining coatings between 3- and 17-μm thickness. The particles present adequate dispersion on the substrate without degradation. These coatings present stability in the particle morphology, structure, adequate absorption in the UV region, and their bandgap values.