Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10377697 | Journal of Colloid and Interface Science | 2005 | 5 Pages |
Abstract
The reaction enthalpies for the solution-phase self-assembly of n-alkylphosphonic acids on the surfaces of TiO2 and ZrO2 have been determined using isothermal titration calorimetry at 298 K. The reaction enthalpies were negative (exothermic) for methyl- and n-octylphosphonic acids and positive (endothermic) for n-octadecylphosphonic acid with both metal oxides. The enthalpy/energy analysis showed that the net enthalpy of the formation of self-assembled monolayers (SAMs) at solid-liquid interface can be presented as follows: ÎHr=âDâ(ÎHsol+ÎHdil)â(ESâESAM), where D is the binding energy of the SAM molecules with the solid; ÎHsol and ÎHdil are the enthalpies of dissolution and dilution; ES and ESAM are the surface energies of bare solid and SAM, respectively. This equation predicted an increase (and the sign change) of the reaction enthalpy as the alkyl group in n-alkylphosphonic acid increased, which explained the experimental data. Using this equation, the binding energy (D) in the SAMs of n-octyl- and n-octadecylphosphonic acids were estimated: 55±5kJ/mol (for ZrO2) and 58±7kJ/mol (for TiO2).
Related Topics
Physical Sciences and Engineering
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Colloid and Surface Chemistry
Authors
Jaime M. Ferreira, Stephen Marcinko, Richard Sheardy, Alexander Y. Fadeev,