Cryo-STEM Reveals Humidity-Controlled Shape Change in Silica Nanoparticles

Cryo-electron microscopy allows the direct observation of cryo-immobilized structures in solution. It therefore is a powerful tool for visualizing formation processes in liquids for which resolution, contrast, or beam damage prevents real-time liquid cell TEM observation. Here, we use cryo-STEM to image at high-resolution hybrid mesoporous silica nanoparticles with structure dictated by the interaction between inorganic silica and an ordered organic template. We demonstrate that surprisingly these silica particles behave as shape change materials (SCMs). Shape changes can be induced via the presence of water, e.g. by controlling the humidity during particle drying, suggesting potential applications of these silica-based nanoparticles as humidity-responsive material.