Surface charges of hedgehog-shaped polyoxomolybdate modified by a cationic surfactant and the inorganic/organic complex

The basic solution properties of the newly synthesised hedgehog-shaped polyoxomolybdate, Na48[HxMo256VIMo112VO1032(H2O)240(SO4)48]⋅ca.1000H2O, x≈16 ({Mo368}, “blue nanolemon”), were investigated by conductivity curves, pH curves, influence of additive electrolytes, and surface modification by a cationic surfactant, tetradecyltrimethylammonium bromide (TTA+Br−). For 1.25 × 10−5 mol L−1 {Mo368} aqueous solution, the average {Mo368}n− surface can be encapsulated by 122 ± 5 TTA+, which allows a spatial arrangement. In addition, the larger clusters with a hydrophilic or hydrophobic surface and monolayer or bilayer capsules were subsequently formed by surface modification of TTA+. At the stoichiometric ratio, {Mo368} and TTA+Br− can spontaneously self-assemble to form a hydrophobic surfactant-encapsulated cluster (SEC), {Mo368}122−–(TTA+)122, which is a novel inorganic/organic nano-complex. From experiments, it was found that many TTA+ cations arrange orderly on the surface of giant anions {Mo368}n−, like reversed micelles. But the complex is poorly crystalline because of the surfactant encapsulation, which makes a few gauche defects in the complex. This topic bridges the channel between inorganic chemistry and colloidal chemistry.