Exploring the impact of water on the morphology and crystallinity of xylan hydrate nanotiles

There has been a resurgence of studies on xylan particles describing various properties and exploring new applications. The aim of this study was to analyze xylan hydrate crystals in the wet state and after air-drying using state-of-art imaging techniques in order to assess the impact of water on both crystallinity and particle morphology. Xylan from esparto grass (Stipa tenacissima) was crystallized and formed convex platelets, termed ‘nanotiles’. Fully hydrated xylan crystals were examined in a layer of vitreous ice by cryogenic electron microscopy. Selected area electron diffraction of the xylan hydrate crystals revealed an oriented crystalline core, unlike the dried crystals that showed no orientation. The surface topographies and thickness of wet and air-dried xylan nanotiles were observed using atomic force microscopy imaging in both liquid and in air. X-ray diffraction was used to assess the crystallinity of xylan nanotiles after drying to varying levels. Air-dried crystals gave diffraction maxima corresponding to xylan hydrate, while wet crystals gave diffraction maxima corresponding to xylan dihydrate. This study offers new insight into xylan hydrate particles, focusing on the role of water on their crystallinity, ultrastructure, and orientation of the crystalline layers.