Reversible intercalation of ammonia molecules into a layered double hydroxide structure without exchanging nitrate counter-ions |
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Authors: | Gregorio Guadalupe Carbajal Arizaga Fernando Wypych Oscar Edel Contreras Lopez |
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Affiliation: | a Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, Apdo. Postal 14, C.P. 22800. Ensenada, Baja California, México b CEPESQ—Research Centre of Applied Chemistry, Department of Chemistry, Federal University of Paraná, P.O. Box 19081, 81531-980 Curitiba, PR, Brazil |
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Abstract: | A zinc/aluminum LDH was precipitated with recycled ammonia from a chemical vapor deposition reaction. The LDH presented a crystalline phase with basal distance of 8.9 Å, typical for nitrate-containing LDHs, and another phase with a basal distance of 13.9 Å. Thermal treatment at 150 °C eliminated the phase with the bigger basal distance leaving only the anhydrous nitrate-intercalated LDH structure with 8.9 Å. Intense N-H stretching modes in the FTIR spectra suggested that the expansion was due to intercalation of ammonia in the form of [NH4(NH3)n]+ species. When additional samples were precipitated with pure ammonia, the conventional LDH nitrate structure was obtained (8.9 Å basal distance) at pH=7, as well as a pure crystalline phase with 13.9 Å basal distance at pH=10 due to ammonia intercalation that can be removed by heating at 150 °C or by stirring in acetone, confirming a unusual sensu stricto intercalation process into a LDH without exchanging nitrate ions. |
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Keywords: | Layered Hydroxide Intercalation Ammonia |
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