Size-dependent photoluminescence properties of bare ZnO and polyethylene imine stabilized ZnO nanoparticles and their Langmuir–Blodgett films

Zinc oxide nanocrystals (∼3 nm) were prepared by colloid chemical method adapted from Meulenkamp [7]. The aging of the sol (particle size increase and aggregation) was investigated by UV–vis absorbance, dynamic light scattering and XRD measurement, particle growth was hindered by surface stabilization with PEI (polyethylene imine). Photoluminescence measurement of ZnO nanoparticles revealed the size-dependent emission properties of ZnO nanocrystals: larger particles show visible emission band at higher wavelengths and weaker intensity. Langmuir–Blodgett (LB) technique was used for the preparation of multilayered films of ZnO and PEI-modified ZnO. Films were characterized with UV–vis absorbance measurements and AFM images. Photoluminescence study of LB films demonstrated that particles preserve their emission properties which makes possible to tune the emission properties of films using ZnO nanoparticles of different sizes.