Majumder Sanjib, Basavaraj Madivala G, Satapathy Dillip K
Soft Material Laboratory, Department of Physics, IIT Madras Chennai-600036 India.
Centre for Soft and Biological Matter, IIT Madras Chennai-600036 India
Nanoscale Adv. 2024 Jul 23;6(19):4907-21. doi: 10.1039/d4na00542b.
Colloidal monolayers serve as fundamental building blocks in fabricating diverse functional materials, pivotal for surface modifications, chemical reactivity, and controlled assembly of nanoparticles. In this article, we report the formation of colloidal monolayers generated by drying an aqueous droplet containing soft colloids confined between two hydrophilic parallel plates. The analysis of the kinetics of evaporation in this confined mode showed that: (i) for a significant portion of the drying time, the drops adopt a catenoid configuration; (ii) in the penultimate stage of drying, the catenoid structure undergoes division into two daughter droplets; (iii) the three-phase contact line remains pinned at a specific location while it continuously slips at all other locations. The interplay between interface-assisted particle deposition onto the solid substrate and the time evolution of particle concentration within the droplet during evaporation results in unique microstructural features in the deposited patterns. Notably, these deposit patterns exhibit reflection symmetry. The microstructural features of the dried deposits are further quantified by calculating the particle number density, inter-particle separation, areal disorder parameter, and bond orientational order parameter. The variation of these parameters for deposits formed under different conditions, such as by altering the spacing between parallel plates and the concentration of microgel particles in the droplet, is discussed.
胶体单层作为制造各种功能材料的基本构建单元，对于表面改性、化学反应性以及纳米粒子的可控组装至关重要。在本文中，我们报道了通过干燥包含限制在两个亲水性平行板之间的软胶体的水滴而形成的胶体单层。对这种受限模式下蒸发动力学的分析表明：（i）在大部分干燥时间内，液滴呈现悬链线构型；（ii）在干燥的倒数第二阶段，悬链线结构分裂成两个子液滴；（iii）三相接触线在特定位置保持固定，而在所有其他位置持续滑动。蒸发过程中界面辅助颗粒沉积到固体基质上与液滴内颗粒浓度随时间的演变之间的相互作用导致了沉积图案中独特的微观结构特征。值得注意的是，这些沉积图案呈现反射对称性。通过计算颗粒数密度、颗粒间间距、面内无序参数和键取向序参数，进一步量化了干燥沉积物的微观结构特征。讨论了在不同条件下形成的沉积物的这些参数的变化，例如通过改变平行板之间的间距和液滴中微凝胶颗粒的浓度。
