Fabrication and characterization of stable ultrathin film micropatterns containing CdS nanoparticles

Stable, ultrathin micropatterns containing CdS nanoparticles (CdS-NPs) were fabricated in a two-step processes. In the first step, a precursor film was built-up by the layer-by-layer electrostatic self-assembly off photosensitive nitro-diazoresin and mercaptoacetic acid capped CdS nanoparticles. In the second step, the film was selectively exposed to UV light through a photomask and developed in an aqueous solution of sodium dodecylsulfate (SDS). The formation of covalently linked micropatterns was based on the different solubilities of the irradiated and non-irradiated parts of the film in the developer. Namely, the irradiated regions were cross-linked and insoluble, whereas the non-irradiated regions, linked with ionic bonds, were removed by the SDS solutions. The resultant patterns were systematically characterized with atomic force microscopy, field emission scanning electron microscopy, optical microscopy, and X-ray photoelectron spectroscopy.