A Journey Through the Landscapes of Small Particles in Binary Colloidal Assemblies: Unveiling Structural Transitions from Isolated Particles to Clusters upon Variation in Composition

Abstract

Two-dimensional (2D) amorphous binary colloidal assemblies composed of particles of two different sizes are characterized by the loss of hexagonal close-packing for larger particles, occurring when the size ratio between small (S) and large (L) particles dSdL exceeds a certain threshold value. For moderately low particle number ratios NSNL large particles still retain a denser arrangement with transitions from hexagonal symmetry to the coexistence of different types of symmetries as NSNL progressively departs from 0 to higher values. On the other hand, small particles reveal sparser arrangements: shape identification and quantification of structural transitions in small particle arrangements appear particularly challenging. In this article, we investigate their shapes and transitions for amorphous binary colloidal particles assembled at the air/water interface. For the quantitative characterization of the evolution in particle arrangements for NSNL variable between 0.5 and 2, we develop an innovative procedure for morphological analysis, combining Minkowski functionals, Voronoi diagrams and ad hoc techniques to recognize and classify specific features. Such a powerful approach has revealed a wide variety of landscapes featuring isolated particles, dimers, chains, small clusters evolving with the colloidal suspension composition. Our method can be applied to the analysis of spatial configurations of sparse colloidal patterns obtained in different conditions.

Shape Deformation in Ion Beam Irradiated Colloidal Monolayers: An AFM Investigation

“…Interfacial self-assembly has been used for the fabrication of colloidal monolayers due to its effectiveness and versatility for the assembly of very diverse materials and has been widely investigated theoretically [1,3,[45][46][47][48][49][50][51][52][53][54][55][56]. In particular, air/water interface self-assembly based on surface confinement and water discharge has been adopted [45].…”

Controlling disorder in self-assembled colloidal monolayers via evaporative processes

“…For a perfect hexagonally close packed crystal, the number of nearest neighbors, N j , is six. More disordered lattices will feature Voronoi cells of varying area 71,72 and differing number of sides. 47,73,74 Statistical analysis of the population of these cells enables the calculation of values describing the entire population, such as the variance or global Voronoi entropy, S vor .…”

“…ref. 72 , 74 , 78 and 81–89 ). Additionally, the complex phase of this function, , can be used as a direct measure of local crystalline ordering.…”

Monte Carlo simulation of particle size separation in evaporating bi-dispersed colloidal droplets on hydrophilic substrates

“…4c). The methods for analyzing the morphology of such structures are described in detail in the reviews 54,55 . Narrow and relatively free space is visible between clusters of a particle mixture and clusters of small particles (Fig.…”