InterPore2026

Effect of cross-sectional geometry, pore diameter and varying hydrophilicity on the water droplet confined in a-silica nanopores

21 May 2026, 15:35

1h 30m

Poster Presentation (MS13) Fluids in Nanoporous Media Poster

Speaker

Gopi Kundia (PhD student)

Description

Mesoporous silica materials have been extensively studied for several decades, with a notable increase since the late 20th century. They are crucial in various scientific fields, including catalysis, drug delivery, adsorption, sensing, CO₂ sequestration, and separation technologies, owing to their material properties, such as a high surface area-to-volume ratio, tunable porosity, ease of surface functionalization, biocompatibility, and the unique behavior of fluids under confinement. Understanding water confined in amorphous silica nanopores is crucial because confinement and surface interactions alter the structural, dynamic, and thermodynamic properties of water relative to its bulk state. These properties govern the fundamental processes, such as adsorption, transport, capillary condensation, and phase behavior in silica nanopores, thereby directly influencing the material applications. To have molecular-level insights, several simulation studies have investigated the behavior of water in silica nanopores, focusing on adsorption, transport, and phase transitions. However, these investigations used crystalline pores, with limited attention to pore geometry and surface wettability. In this study, we employ molecular dynamics simulations to investigate the behavior of water confined in amorphous silica nanopores. Our earlier study, which used a Lennard-Jones solid and fluid, demonstrated that the cross-sectional geometry, pore size, and solid-fluid interaction strength significantly impact droplet stability and phase behavior.[1] In this work, we extend the investigation to a more realistic system by employing molecular dynamics simulations to study water confined in functionalized amorphous silica nanopores. Specifically, we examine how surface wettability (tuned via methyl functionalization), cross-sectional geometry (circular, hexagonal, square, and triangular), and pore diameter (1–6 nm) influence the stability, density distribution, self-diffusivity and meniscus shape of the confined liquid. We identify a confinement-driven crossover in silica nanopores, where water transitions from an adsorption-dominated molecular clustering regime under extreme confinement (1–2 nm) to a stable, bulk-like capillary liquid column at larger diameters (6 nm), with intermediate pore sizes exhibiting pronounced transitional behavior. In methyl-functionalized pores (except the smallest system), these liquid-like columns remain segmented into discrete water clusters separated by vapor-like regions. Moreover, we observe that the pore geometry modulates the stability and connectivity of water columns/clusters in hydrophilic/hydrophobic nanopores. While experimental studies offer valuable macroscopic insights, molecular simulations provide a detailed atomistic understanding essential for capturing the local and interfacial behavior, as well as the dynamic properties of confined fluids. Our findings aim to deepen the fundamental knowledge of confined water in realistic silica systems and guide the rational design of functional mesoporous materials for target applications.