Tuning Thin Film Thickness and Porosity with Layer-by-Layer Submicronic Particles Assembly

Porous NiO films were prepared using Layer-by-Layer assembly of submicronic β-Ni(OH)₂ nanoplatelets and size-controlled poly(methyl methacrylate) (PMMA) particles. β-Ni(OH)₂/PMMA thin films were elaborated using different PMMA particle sizes and concentrations. The elaborated films were then heated at a temperature of 325 °C in air for one hour to form porous NiO films by calcining β-Ni(OH)₂ nanoplatelets. PMMA polymeric particles were also calcined during this process, leading to film porosity. Thermal treatment experiments clearly showed a relationship between PMMA particle size and film properties i. e., porosity and thickness. NiO films exhibited huge pores, around 1 μm, and matter loss after calcination when PMMA particles with a diameter of 190±43 nm were employed. Partial collapsing of the films was also denoted. Experiments were then carried out by decreasing PMMA particle size (100±19 nm) leading to cohesive NiO films. Finally, the specific surface area (SSA) of the NiO films prepared with PMMA particles of 100 nm was determined by adsorption-desorption of nitrogen gas using the BET (Brunauer–Emmet–Teller) method. This showed an increase in SSA with PMMA particle concentration.