Effects of Monolayer Density and Bulk Ionic Strength on Acid−Base Equilibria at the Air/Water Interface

• DOI: 10.1021/jp0018091
• Publication Date: 2002-07-26T06:04:16Z
• Authors: Hongfei Wang; Xiaolin Zhao; K. B. Eisenthal
• Keywords: Interface (matter); Air interface

The surface density and electrolyte concentration dependences of the pKa CH3(CH2)21NH3+ at air/water interface are obtained using method second harmonic generation. If it is assumed that amphiphiles uniformly distributed interface, application Gouy−Chapman model yields values ranging from 10.2 to 8.2 as varies 100 22 Å2/molecule. By accounting for inhomogeneity i.e., there islands "liquid phase" immersed in a "gas very low-density amphiphiles, single 10.1 ± 0.2 all densities. acidity long chain amine enhanced by 3 times compared with bulk aqueous solution.