Charge-Regulated Spontaneous, Reversible Self-Assembly of the Carboxylic Acid-Functionalized Hydrophilic Fullerene Macroanions in Dilute Solution

Abstract

Fullerene molecule covalently functionalized with 12 carboxylic acid groups on its periphery was synthesized, and its solution behavior was explored. The functionalized fullerene molecules behave as hydrophilic macroions in polar solvents by showing strong attractions with each other mediated from their counterions and consequently self-assembling into single-layer, hollow, spherical blackberry-type structures in solvents with moderate polarity. The fullerene molecules are not touching with each other in the assemblies, and the assembly size can be tuned by changing the polarity of the solvents. More importantly, the transition between the self-assembly and the disassembly of the macroions can be easily achieved by changing temperature. The discovery confirms that the semirigid clusters demonstrate the unique solution behavior of macroions and open up a new way to assemble fullerene into functional materials and devices.