Insights into the microstructure and interconnectivity of porosity in porous starch by hyperpolarized 129Xe NMR

For the first time, hyperpolarized (HP) Xe-129 NMR measurements are utilized to explore porous structures of porous starch (PS) successfully. Some micropores resided inside the mesopore walls of PS were detected by variable temperature (VT) HP Xe-129 NMR, and the pore sizes of micropores were also estimated using the empirical relationship. Furthermore, the interconnectivity of pores was investigated in detail by two-dimensional (2D) exchange spectroscopy (EXSY). The exchange process of xenon from microporosity within pore walls to the free gas space was occurred at the mixing time of >= 12 ms at 173 K, which indicated the well interconnectivity between micropores and mesopores. This study not only exhibits a new approach for investigation of pores and hollows of PS, but also provides a better understanding of porous structures for rational design in adsorbing functional compounds. (C) 2020 Elsevier B.V. All rights reserved.