Research Paper

Journal of Nanoparticle Research

, Volume 11, Issue 4, pp 831-839

The effect of excess surfactants on the adsorption of iron oxide nanoparticles during a dip-coating process

  • Chang-Woo KwonAffiliated withDepartment of Materials Science and Engineering and Nano System Institute-National Core Research Center, Seoul National University
  • , Tae-Sik YoonAffiliated withDepartment of Nano Science and Engineering, Myongji University
  • , Sung-Soo YimAffiliated withDepartment of Materials Science and Engineering and Nano System Institute-National Core Research Center, Seoul National University
  • , Sang-Hyun ParkAffiliated withDepartment of Materials Science and Engineering and Nano System Institute-National Core Research Center, Seoul National University
  • , Ki-Bum KimAffiliated withDepartment of Materials Science and Engineering and Nano System Institute-National Core Research Center, Seoul National University Email author 

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Abstract

The effect of excess surfactants (oleic acids) in a colloidal solution on the adsorption behavior of 9.5-nm-sized, sterically stabilized iron oxide (γ-Fe2O3) nanoparticles on hydrogen terminated Si (Si:H) substrates during a dip-coating process is examined. While the particle coverage follows a type of Langmuir adsorption isotherm as initially increasing and subsequently saturating with increasing particle concentration, it also critically depends on the excess surfactant concentration in the solution. For instance, it is noted that by adding the oleic acids from 0.06 to 2.80 × 1018 ml−1 in the solution with 4.65 × 1013 ml−1 particle concentration, the coverage is gradually reduced from 0.42 to 0.25. In addition, increasing surfactant concentration distinctly changes the morphology of a self-assembled particle layer from densely distributed smaller clusters to sparsely connected, larger ones with enlarged space. The reduced coverage and enlarged cluster size with increasing oleic acid concentration are explained by the reduced interaction energy between particle and substrate and the increased capillary force between particles.

Keywords

Colloidal nanoparticles Adsorption Surfactant Dip-coating Nanoparticle cluster