Monoparticulate layers of silanized glass spheres at the water-air interface: Particle-particle and particle-subphase interactions

Zoltán Hórvölgyi, Sándor Németh, Janos H. Fendler

Research output: Contribution to journalArticle

97 Citations (Scopus)

Abstract

Silanization has rendered spherical (75 ± 5 μm diameter) glass particles to be weakly (sample A, Θ = 55°), moderately (sample B, Θ = 72°), and highly (sample C, Θ = 90°) hydrophobia. Nonequilibrium surface pressure (Π) vs surface area (A) isotherms have been determined for monoparticulate layers which were prepared from samples A, B, and C at water-air interfaces in a Langmuir film balance. The effect of hydrophobicity on the particle-particle interaction and on the energy (Er) which is necessary for the removal of a particle from the water-air interface (particle-subphase interaction) has been elucidated. Contact cross-sectional areas (CCSA), surface coverages (SC), and collapse energies (Ec), evaluated from Π vs A isotherms, provided semiquantitative information on the structural strength. Monoparticulate layers which were formed from the most hydrophobic glass spheres (sample C) had a structural strength which was almost 5 times greater than that of those which were formed from the least hydrophobic sample (sample A), as revealed by the Ec values which were elucidated for these systems. Long-term stability, determined by time-dependent surface-pressure measurements, was only found for sample C. The energy of a particle-particle contact was calculated, for the strongly cohesive layer of sample C, to be (1.2-1.4) x 10-10 J. The weakly cohesive layer, prepared from sample A, had a 490-nm interparticle distance at the secondary energy minimum and a total repulsive interaction energy in the range of (0.5-1.3) x 10-13 J between two beads at an interparticle distance of 1-200 nm. Values for adhesion work (Wr) were calculated from in situ contact-angle measurements and compared to corresponding Er values which were obtained experimentally by the isotherms. The significant discrepancies between the Wr- and Er values which were found for sample A or sample B were rationalized in terms of contact-angle hysteresis, dynamic wetting, and distortion of the electric double layer around the interfacial beads.

Original languageEnglish
Pages (from-to)997-1004
Number of pages8
JournalLangmuir
Volume12
Issue number4
DOIs
Publication statusPublished - Feb 21 1996

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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