Size Effect of Silica Shell on Gas Uptake Kinetics in Dry Water

Two kinds of dry water (DW) particles are prepared by mixing water and hydrophobic silica particles with nanometer or micrometer dimensions, and the two DW particles are found to have similar size distributions regardless of the size of the silica shell. The CO2 uptake kinetics of DW with nanometer (nanoshell) and micrometer shells (microshell) are measured, and both uptake rate and capacity show the obvious size effect of the silica shell. The DW with a microshell possesses a larger uptake capacity, whereas the DW with a nanoshell has a faster uptake rate. By comparing the uptake kinetics of soluble NH3 and CO2 further, we found that the microshell enhances the stability and the dispersion degree of DW and the nanoshell offers a shorter path for the transit of guest gas into the water core. Furthermore, molecular dynamics simulation is introduced to illustrate the nanosize effect of the silica shell on the initial step of the gas uptake. It is found that the concentration of gas molecules close to the si...