Confined selenium chains in one-dimensional mordenite nanochannels: A TEM and Raman spectroscopy study

This study investigates the incorporation of selenium chains into the nanochannels of hydrated mordenite (MOR) using high-resolution TEM imaging, Raman spectroscopy, and computational simulations. The results reveal that selenium chains are successfully incorporated within the mordenite framework, with changes in image contrast confirming its presence. Raman spectroscopy was employed to identify the selenium species in Se-MOR, revealing characteristic vibrational modes associated with trigonal selenium structures. Raman spectrum for Se-MOR displayed peaks at 250 cm^–1, attributed to symmetric bond-stretching, and at 265 cm^–1, linked to antisymmetric bond-stretching, confirming the presence of selenium chains within the nanochannels of the mordenite structure. Crystallographic modeling and TEM analysis show that these selenium chains are integrated into specific nanochannels, influencing the Se-MOR growth directions. TEM imaging and SimulaTEM simulations at 300 and 400 keV in bright field mode show no changes in pure mordenite but reveal darker regions in Se-MOR corresponding to selenium chains. STEM_CELL simulations in dark field mode confirm increased intensity in selenium-rich regions, consistent with conventional TEM mode observation. Comparisons between simulated and experimental Raman spectrum show good agreement, suggesting that selenium chains primarily occupy small nanochannels in hydrated mordenite, while larger nanochannels in dehydrated mordenite may accommodate a range of selenium species. Additionally, the study explores the impact of water molecules on selenium incorporation, showing that only selenium chains are formed in the small channels in the presence of water.