Formation of hexamethylbenzene: chloranil charge transfer nanocrystals

The nucleation and growth of nanoparticles can be induced using the reprecipitation method, in which a solution is rapidly mixed with a miscible non-solvent. This method has been used to create a wide variety of organic nanoparticles, including those comprised of polymers or of small molecules. Here we demonstrate the formation of charge transfer nanocrystals of the electron donor hexamethylbenzene and electron acceptor chloranil using the reprecipitation method. We achieve the rapid mixing needed for nanoparticle formation in a number of ways: using a 3D printed vortex micro-mixer, a double impinging jet mixer or direct jet injection of the solution into the non-solvent. The crystal formation kinetics are characterized over times scales from 10 ms to tens of minutes using UV-Vis absorption spectroscopy and dynamic light scattering.