Adsorption characteristics of charged and nonionic small molecules to colloidal alumina

Vikram J. Pansare, Victoria Hwang, Carlos Figueroa, Robert K. Prud'homme

Research output: Contribution to journalArticlepeer-review

Abstract

Dense fluorescent pigments used for inkjet printing of UV and IR-readable non-photobleaching security features require stabilizers to prevent aggregation/sedimentation and inkjet head clogging at high resolution. A study of small molecule adsorption to α-alumina, a model system for security pigments, is presented. Alumina is dispersed by two methods yielding different zeta potentials but identical isoelectric points. Essentially complete dispersion is obtained in water at pH 3 but aggregation occurs at pH 6 where the surface charging is lower. Adsorption studies focus on the naphthyl-phosphate, -sulfate, and hydroxyl (triethylene glycol) groups. Phosphate adsorption was strongest with a 1.2 molecules/nm2 plateau, close to the titratable exchange capacity of 1.3 [sbnd]OH groups/nm2 on the alumina surface with ΔHadsorption = −7.58 ± 1.63 kJ/mol determined by calorimetry. Sulfate adsorption was weaker with a more linear adsorption isotherm. The adsorption/exchange process yields a rise in pH that is correlated with the binding strength. Hydroxyl binding is weakest, being driven by hydrogen bonding, and showed no rise in pH during adsorption. A polyphosphate-poly(ethylene glycol) block copolymer is expected to be advantageous for the dispersion of such inkjet colloids.

Original languageEnglish (US)
Pages (from-to)29-38
Number of pages10
JournalJournal of Colloid And Interface Science
Volume512
DOIs
StatePublished - Feb 15 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

Keywords

  • Adsorption isotherm
  • Aharged small molecule
  • Alumina
  • Inkjet
  • Isothermal calorimetry
  • Stabilization

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