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New method for determination of surface pKa using second harmonic generation

โœ Scribed by Xiaolin Zhao; Shaowei Ong; Hongfei Wang; Kenneth B. Eisenthal

Publisher
Elsevier Science
Year
1993
Tongue
English
Weight
416 KB
Volume
214
Category
Article
ISSN
0009-2614

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โœฆ Synopsis

A new method to determine the pK, of chemical species at aqueous insulating interfaces is based on the discovery that the interface potential is linearly proportional to the measured second harmonic electric field. The proportionality constant is the effective third-order susceptibility and is the same for all aqueous interfaces studied, which has its origin in the polarization of bulk water induced by the charged form of the acid or base at the interface. We have determined that CH3(CH2)2LNH1+ at the air/water interface has a pK, of 9.9? 0.2 versus 10.6 in bulk water.

๐Ÿ“œ SIMILAR VOLUMES

Determination of pKa at the air/water in
Determination of pKa at the air/water interface by second harmonic generation
โœ Xiaolin Zhao; Suchitra Subrahmanyan; Kenneth B. Eisenthal ๐Ÿ“‚ Article ๐Ÿ“… 1990 ๐Ÿ› Elsevier Science ๐ŸŒ English โš– 457 KB

We have used second harmonic generation to directly observe chemical changes in a lipid monolayer. We observed that pK, of phexadecyl aniline at the air/water interface is 3.6& 0.2 versus 5.3 fO.l in the bulk. This fiftyfold increase in acidity is due to the higher free energy of a charged species a