A facile way of controlling capillary condensation: particle-based crystal

Abstract

To demonstrate a facile method to control capillary condensation via the design of confined geometric structures, we use a particle self-assembly technique to fabricate porous materials with well-defined pore sizes. Four groups of silica particles were synthesized using the modified Stober method, and these groups of particles were then arranged in closely packed structures. Quantitative predictions of capillary condensation were made based on the Kelvin equation and an approximation of the geometric structures of our closely packed samples. Experimental observations revealed that water uptake at 100% relative humidity reached 40%–50% relative to particle mass across sizes, closely aligning with theoretical predictions for small-particle systems, even though the geometry of some of the confined spaces corresponds to distances smaller than 10 nm. Despite deviation from theoretical predictions that are observed in larger particle systems, and which can be attributed primarily to practical limitations of attainable ordered structures at these scales, this fabrication method shows great potential for the creation of devices that allow facile control of capillary condensation in relevant applications such as vapor capture and humidity control.