Connecting Surface-Forces-Based Energy Barriers to Nonhomogeneous Colloidal Structures to Appear from Volatile Binary Mixtures of Same Size Nanoparticle Species

The capacity of nanoparticles to self-arrange to various structures and their unique physical properties has made these building blocks essential in a broad range of applications and scientific disciplines. In this work, the manipulation of particulate structures that appear from binary dispersions is demonstrated, comprising same size particles of two different chemistries, following the evaporation of an electrolyte solution carrier. By varying the ionic strength and pH in the solutions, the balance between attractive and repulsive surface forces is tuned, that is, electrical double layer, Van der Waals, hydrophobic, and hydrophilic forces, in the binary particle mixtures. Hence, the corresponding potential energy barriers are tuned to particle attachments to each other and to the underlying substrate and alter the nanoscopic arrangement of the different types of particles in the microscopic particulate structures, which appear by convective pattern formation. Hence, by realizing the physical mechanisms which govern the potential energy contributions to the pattern formation of particulate structures at the nanometer scale, the 3D morphology of binary mixtures of same size particles is rendered homogeneous, layered, or phases separated. This is a useful approach toward the top-down fabrication of nonhomogeneous colloidal structures.