With the aim of quantitatively investigate the anion binding to a fully non-ionic surface, the self-diffusion coefficients of four different anions were probed in a Triton X-100 micellar solution by means of multinuclear PGSTE-NMR measurements. The salt concentration used was sufficiently low to avoid any observable alteration of the surface of interaction (the micellar ensemble). A specific anion binding was detected. Through a careful data modeling, anions affinity to the micellar surface could quantitatively be placed in the order (CH3)2AsO2− >> CH3COO− > H2PO4− > F−, that represents a Hofmeister series. Since the micellar aggregates here used as model surface do not bear any electric charge and only the surfactant hydrophilic moiety is exposed to the bulk, electrostatics or hydrophobic interactions cannot be considered relevant to justify the different anion binding. Therefore, the observed ion specificity can be rationalized only calling into play the non-electrostatic interactions occurring between the anions and the micellar surface.
Quantification of Specific Anion Binding to Non-Ionic Triton X-100 Micelles
PALAZZO, Gerardo
2012-01-01
Abstract
With the aim of quantitatively investigate the anion binding to a fully non-ionic surface, the self-diffusion coefficients of four different anions were probed in a Triton X-100 micellar solution by means of multinuclear PGSTE-NMR measurements. The salt concentration used was sufficiently low to avoid any observable alteration of the surface of interaction (the micellar ensemble). A specific anion binding was detected. Through a careful data modeling, anions affinity to the micellar surface could quantitatively be placed in the order (CH3)2AsO2− >> CH3COO− > H2PO4− > F−, that represents a Hofmeister series. Since the micellar aggregates here used as model surface do not bear any electric charge and only the surfactant hydrophilic moiety is exposed to the bulk, electrostatics or hydrophobic interactions cannot be considered relevant to justify the different anion binding. Therefore, the observed ion specificity can be rationalized only calling into play the non-electrostatic interactions occurring between the anions and the micellar surface.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
