^a State Key Laboratory C*tion Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010, China

^b Sichuan University of Science and Engineering, Zigong 643000, China

^c Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory, Southwest University of Science and Technology, Mianyang 621010, China

摘要：Electrostatic interaction of charged colloids and polyelectrolytes is a useful method to assemble matter into hybrid nanostructures with numerous examples in materials science as well as in biology. However, the colloidal electrostatic interaction is rapid and uncontrolled, the strong interaction usually leads to large and irregular aggregates. Therefore, control of the electrostatic interaction in order to resulting well-defined nanostructures remains a challenge. Here we report on a general and simple method to moderate the wild electrostatic interaction. Direct mixing of stock solutions containing anionic superparamagnetic nanoparticles and widespread cationic homopolyelectrolytes at an appropriate ionic strength generates aggregates with controlled shape and morphology. The simple and versatile methodology not only efficiently moderates electrostatic interactions but also enables the corresponding growth mechanism to be revealed by light scattering and electron microscopy as aggregation occurs at much slower timescales. The present results carry important implications for both practical applications and understanding on nanoscale electrostatic interaction between colloids.