Spectroscopic study on strongly luminescent Nd(iii) exchanged zeolite: TMA+-containing FAU type zeolite as a suitable host for ship-in-bottle synthesis

Enhanced emission from intrazeolite Nd3+ was investigated by using bis(perfluoromethanesulfonyl)aminate (PMS) as a low vibrational ligand of the ion and TMA+-containing FAU zeolite nanocrystallite (TMA–nano-FAU) as a host matrix. Treatments such as deuteration, and thermal treatments at high temperatures were ineffective for the strong emission of Nd3+ within this zeolite. The high-resolution emission and excitation spectra suggested that the environment of Nd3+ in the zeolite was more homogeneous than that in a glass matrix, and intrazeolitic emissive Nd3+ ions consisted of at least two species. The diffuse reflectance spectra revealed that the strong emission was attributed to the PMS ligands that eliminated hydroxy groups from the vicinity of the ion. On the other hand, thermal treatment at high temperatures induced emission of Nd3+-exchanged Na–micro-FAU. Judd–Ofelt analysis revealed that the difference of the emission property between TMA–nano- and Na–micro-FAU zeolites depended on whether the cations migrated to the inner cages or not: in the former case, the ligation of PMS with the Nd3+ ion occurred easily, because the ions remained in the super cages without migrating into inner cages due to the hindrance of TMA+ occupying in the sodalite cages. In the latter case, the ligation was suppressed because of the Nd3+ ions migrated into the inner cages from the supercages.