Colloidal lithography: Synthesis and characterization of SiO2 and TiO2 micro-bowel arrays

Abstract

Recent interest has surged in engineering surface structures at nano/micro scales using accessible and cost-effective techniques, owing to their wide-ranging applications. In this study, we fabricated ordered arrays of TiO₂ and SiO₂ micro-bowels utilizing the colloidal lithography method and delved into their optical properties. Initially, we synthesized polymethyl methacrylate (PMMA) microspheres with an average diameter of 409 nm via the emulsion polymerization method. Ensuring crack-free and well-organized 2D colloidal crystals as the lithography template is crucial for achieving high-quality and systematically arranged micro-bowel arrays. Therefore, we explored two distinct methods for fabricating 2D colloidal PMMA crystals, namely the Langmuir−Blodgett trough and gravity-assisted wedge-shaped cell techniques, and compared their outcomes. Subsequently, we introduced a specific amount and concentration of TiO₂/SiO₂ precursor into the templates. Upon removal of the polymeric template through calcination and chemical etching, the micro-bowel array persisted on the substrate surface. We thoroughly investigated the influence of the template fabrication method on the quality of the final microstructures. Our analyses affirm that the Langmuir−Blodgett technique yields higher-quality micro-bowels in a shorter duration. The ordered structures and high surface-to-volume ratio of the micro-bowels render them suitable candidates for various applications including photocatalysis, solar cells, bio/chemical sensors, and more.