Self-Assembly of Nanoparticles from Evaporating Sessile Droplets: Fresh Look into the Role of Particle/Substrate Interaction

TL;DR

This study investigates how particle concentration and particle/substrate DLVO interactions influence the shape of deposits formed by drying sessile droplets, revealing that deposit morphology is primarily governed by concentration rather than interaction forces.

Contribution

It provides a comprehensive analysis of deposit shapes over a wide range of concentrations and DLVO interactions, challenging previous assumptions about the role of particle/substrate forces.

Findings

Deposit shape is consistent across different DLVO regimes at the same concentration.

Low concentration deposits predominantly show dot-like patterns.

Particle/substrate interactions have limited influence on deposit morphology.

Abstract

We studied the dependence of solid deposit shape obtained by free drying of sessile drops on the particles concentration and Derjaguin-Landau-Verwey-Overbeek (DLVO) particle/substrate interaction. In contrast to previous contributions using pH as a control parameter of interactions, we investigated an unprecedentedly wide range of concentrations and particle/substrate DLVO forces by modifying the nature of the substrate and particles as well as their size and surface chemistry whereas long-distance repulsive interactions between particles were maintained for most of the drying time. Our main result is that the different shapes of deposits obtained by modifying the particle concentration are the same in the different regimes of concentration regardless of particle/substrate interaction in the studied range of DLVO forces and particle concentrations. The second result is that, contrary to expectations, the dominant morphology of dry patterns at low particle concentration always shows a dot-like pattern for all the studied systems.