Optical study of oriented double-Se8-ring clusters and luminescent Se2− anions in LTA at extremely high selenium loading density

• Published in: Microporous and mesoporous materials Vol. 348; p. 112395
• Main Authors: Poborchii, Vladimir V., Petranovskii, Vitalii P., Glukhov, Igor A., Fotiadi, Andrei A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15.01.2023
• Subjects: Photoluminescence; Raman/Brillouin microscopy; Selenium; Zeolite single crystals; Selenium; Zeolite single crystals; Raman/Brillouin microscopy; Photoluminescence
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2022.112395

Recently, LTA-Se(1–8) samples with 1–8 Se atoms per cavity (simplified unit cell, large cavity + sodalite cage) obtained via adsorption at the temperature of ∼450 °C were reported. It was shown that single Se8 or single Se12 ring are formed in the large LTA cavities, Se8/Se12 ring concentration ratio decreasing with an increase in the Se loading density. Contrary, in the present work, using Se vapour adsorption at ∼550 °C, we succeeded in encapsulation of ∼17 Se atoms per cavity (LTA-Se(17)) with a significant increase in the Se8/Se12 concentration ratio manifesting double Se8-ring cluster formation in the most of the LTA large cavities, which is a step towards cluster crystal fabrication. According to our polarization/orientation Raman spectroscopic study of LTA-Se(17) single crystals, the orientations of the Se8 and Se12 appeared to be similar to those in previously investigated LTA-Se(1–8). Importantly, luminescent Se2− anions, oriented along the LTA 4-fold axes and located in the sodalite cages, are detected via Raman polarization/orientation dependencies of LTA-Se(17). Bright Se2− light emission with a maximum at ∼1.56 eV and vibronic structure is observed in the 1.3–1.8 eV spectral range. We show that the anions experience a compression in LTA which is slightly relaxing with a decrease in temperature producing an anomalous Raman band downshift. The compression of Se2− in LTA is weaker/stronger than that in sodalite/cancrinite, luminescence band photon energy depending on its strength. High concentration of regularly arranged Se2− in LTA suggests considering LTA-Se(17) as an important novel light-emitting material. [Display omitted] •Extremely high Se loading density of 17 at./cav. is achieved in LTA zeolite.•Mainly double Se8 and minor single Se12 rings are formed in LTA large cavities.•Se2− anions oriented along 4-fold axis are found in sodalite cages.•Se2− luminescence with a maximum at ∼1.55 eV and vibronic structure is found.•Compression of Se2− at ∼300 K and its partial relaxation at ∼77 K is observed.