Colloidal Nanoparticle-Layer Formation Through Dip-Coating: Effect of Solvents and Substrate Withdrawing Speed

The effect of solvents of colloidal solution and substrate withdrawing speed during dip-coating on the nanoparticle-layer formation of sterically stabilized iron oxide (gamma-Fe(2)O(3)) nanoparticles on Si substrates is investigated. From the solutions with 10(13)-10(14) mL(-1) particle concentrations dispersed in hexane, octane, decane, and tetradecane, the multilayer is formed from hexane while the uniform monolayer is formed from octane, decane, and tetradecane. Because the particle layer is formed by direct adsorption and convective flux of particles from solution to substrate, the multilayer formation from hexane is due to the highest interaction energy between particle and substrate and the highest convective flux to the meniscus region of the substrate caused by the highest evaporation rate. Lowering the substrate withdrawing speed increases the particle coverage from similar to 60 to similar to 80% at 0.001 mm/s as locally forming the multilayer regions, which is explained by increased convective flux at reduced speed. These results verify that the colloidal particle delivery to the substrate is determined by factors such as particle-substrate interactions, substrate withdrawing speed, and the evaporation rate of solvent. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3089364] All rights reserved.