Spin-Assisted Multilayers of Poly(methyl methacrylate) and Zinc Oxide Quantum Dots for Ultraviolet-Blocking Applications

Thin UV-blocking films of poly(methyl methacrylate) (PMMA) and ZnO quantum dots (QDs) were built-up by spin-coating. Ellipsometry reveals average thicknesses of 9.5 and 8.6 nm per bilayer before and after heating at 100 °C for one hour, respectively. The surface roughness measured by Atomic force microscopy (AFM) was 3.6 and 8.4 nm for the one and ten bilayer films, respectively. The linear increase in thickness as well as the low surface roughness increment per bilayer indicates a stratified multilayer structure and a smooth interface without aggregation. The absorption of UV radiation increased with increasing number of bilayers. At the same time, transmission was damped at wavelengths shorter than 375 nm. The thin films had a high and constant transparency in the visible region. Green-light emitting QDs could be detected by confocal microscopy at a concentration of 20% in a single layer of PMMA/ZnO. PMMA/ZnO QDs thin films are hydrophobic, as indicated by contact angle measurements.