Effect of [Zr(α-PW11O39)2]10− Polyoxometalate on the Self-Assembly of Surfactant Molecules in Water Studied by Fluorescence and DOSY NMR Spectroscopy

Thomas Quanten,Pavletta Shestakova,Aleksandar Kondinski,Tatjana Parac-Vogt

doi:10.3390/inorganics6040112

Abstract

The catalytic fragmentation of hydrophobic proteins by polyoxometalates (POMs) requires the presence of surfactants in order to increase the solubility of the protein. Depending on the nature of the surfactant, different effects on the kinetics of protein hydrolysis are observed. As the molecular interactions between the POMs and surfactants in solutions have been scarcely explored, in this study, the interaction between the catalytically active Keggin polyoxometalate [Zr(α-PW11O39)2]10− and four different surfactants—sodium dodecyl sulfate (SDS), dodecyldimethyl(3-sulfopropyl)ammonium (Zw3-12), dodecyldimethyl(3-sulfopropyl) ammonium (CHAPS), and polyethylene glycol tert-octylphenyl ether (TX-100)—have been studied in aqueous media. The effect of polyoxometalate on the self-assembly of surfactant molecules into micelles and on the critical micellar concentration (CMC) has been examined by fluorescence spectroscopy and diffusion ordered NMR spectroscopy (DOSY).

Highlights

Polyoxometalates (POMs) are anionic metaloxo clusters typically comprised of early transition metal centers in high oxidation states [1]
We explored the effect of the Keggin polyoxometalate [Zr(α-PW11 O39 )2 ]10− on the formation of surfactant-based micelles
Our experiments using fluorescent spectroscopy showed that the critical micellar concentration (CMC) of the anionic sodium dodecyl sulfate (SDS) and the neutral TX-100 are unaffected by 1

Summary

Introduction

Polyoxometalates (POMs) are anionic metaloxo clusters typically comprised of early transition metal centers in high oxidation states (mainly V, Mo, and W) [1]. POMs will influence the soluble surfactants low concentrations the water/air interface. SECsofhave mainly headgroup, explored in (CMC), which can be influenced by theHowever, following:so (i) charge the been hydrophilic non-aqueous media, they haveand been much attention in material science and the length of the hydrophobic moiety,. We first explore the effect of 1 on the CMC using fluorescence spectroscopy, which is followed by detailed 1 H and 31 P DOSY studies [21,22,23]. Results and Discussion is used as the salt, (Et2 NH2 )10 [Zr(α-PW11 O39 )2 ] throughout the study This POM has previously been shown to exhibit catalytic activity towards the hydrolysis of different proteins [13,14]

Method

Materials and Methods

Conclusions