Structural colors of the SiO2/polyethyleneimine thin films on poly(ethylene terephthalate) substrates

The SiO2/polyethyleneimine (PEI) films with structural colors on poly(ethylene terephthalate) (PET) substrates were fabricated by an electrostatic self-assembly method. The morphology of the films was characterized by Scanning Electron Microscopy. The results showed that there was no distinguishable multilayered structure found of SiO2/PEI films. The optical behaviors of the films were investigated through the color photos captured by a digital camera and the color measurement by a multi-angle spectrophotometer. Different hue and brightness were observed at various viewing angles. The structural colors were dependent on the SiO2 particle size and the number of assembly cycles. The mechanism of the structural colors generated from the assembled films was elucidated. The morphological structures and the optical properties proved that the SiO2/PEI film fabricated on PET substrate formed a homogeneous inorganic/organic SiO2/PEI composite layer, and the structural colors were originated from single thin film interference.