Self-Recognition Between Two Almost Identical Macroions During Their Assembly: The Effects of pH and Temperature

摘要

Two Keplerate-type macroions, [(Mo72Fe30O252)-Fe-VI-O-III- (CH3COO)(12){Mo2O7(H2O)}(2){H2Mo2O8(H2O)}(H2O)(91)]ca.150H(2)O= {Mo72Fe30} and [{Na(H2O)(12)}< subset of>{(Mo72Cr30O252)-Cr-VI-O-III(CH3COO)(19)- (H2O)(94)}]ca.120H(2)O={Mo72Cr30}, with identical size and shape but different charge density, can self-assemble into spherical blackberry-like structures in aqueous solution by means of electrostatic interactions. These two macroanions can self-recognize each other and self-assemble into two separate types of homogeneous blackberries in their mixed dilute aqueous solution, in which they carry -7 and -5 net charges, respectively. Either adjusting the solution pH or raising temperature is expected to make the self-recognition more difficult, by making the charge densities of the two clusters closer, or by decreasing the activation energy barrier for the blackberry formation, respectively. Amazingly, the self-recognition behavior remains, as confirmed by dynamic and static light scattering, TEM, and energy dispersive spectroscopy techniques. The results prove that the self-recognition behavior of the macroions due to the long-range electrostatic interaction is universal and can be achieved when only minimum differences exist between two types of macroanions.