Unexpected Coulomb Interactions in Nonpolar Solvent for Highly Efficient Nanoxerography of Perovskite Quantum Dots

In this work, an unexpected sign-dependent electrostatic assembly, also known as nanoxerography, of perovskite quantum dots was observed in nonpolar solutions. Electrical force microscope measurements showed that CsPbBr₃ quantum dots carry negative charges and tend to aggregate at the positively charged nanospots via Coulomb interactions despite that they are synthesized and dispersed in a neutral nonpolar solvent. The result was further confirmed by a statistical method developed in this work based on the Gibbs-Boltzmann distribution. More interestingly, we found that the existence of net charges is a common phenomenon for widely used oil-phase synthesized nanoparticles, including Au, Fe₂O₃, and CdSe/ZnS nanoparticles. This is contrary to the common belief and indicates the possibility of highly efficient nanoxerography for functional nanoparticles synthesized in nonpolar solvents.