Ionic Specificity in pH Regulated Charged Interfaces: Fe(3+) versus La(3+)
|Title||Ionic Specificity in pH Regulated Charged Interfaces: Fe(3+) versus La(3+)|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||Wang WJ, Park RY, Meyer DH, Travesset A, Vaknin D|
We determine the distribution of two trivalent ions Fe(3+) and La(3+) next to two different amphiphilic charged interfaces as ions or complexes, consisting of the phosphate lipid dihexadecyl phosphate (DHDP) and the fatty acid arachidic acid (AA). These amphiphiles provide a wide range of plc values, from 2.1 (DHDP) to 5.1 (AA), thus allowing manipulation of the surface charge over extremely low pH (pH similar to 1 or larger), and the two ions provide two limiting cases of specificity for the amphiphiles. We find that La(3+) distribution is mostly sensitive to the surface charge, whereas the Fe(3+) binding depend:: on its character in the solution and is highly specific, as indicated by the crucial role played by iron complexes (Fe(OH)(3) or Fe(OH)(2+)) forming covalent bonds even for an uncharged interface. The implications of the results to other ions and/or amphiphilic interfaces are also discussed.