Transformation of Amorphous Terbium Metal–Organic Framework on Terbium Oxide TbOx(111) Thin Film on Pt(111) Substrate: Structure of TbxOy Film

Abstract

The present study is focused on the synthesis and structural properties of amorphous terbium metal–organic framework thin film (TbMOF-TF) and its transformation to terbium oxide by pyrolysis at 450 °C in the air. The crystalline (cTbMOF) and amorphous (aTbMOF) films were prepared by solvothermal synthesis using different amounts (0.4 and 0.7 mmol) of the modulator (sodium acetate), respectively. The powders were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM). The varied chemical composition of the surface of TbMOFs and TbxOy was investigated by X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aTbMOF had been fully transformed to a Tb4O7 phase with a cubic crystal structure at 450 °C. The amorphous aTbMOF-TF film was prepared by dropping a colloidal solution of amorphous precursor nanocrystals on the SiO2/Si substrates covered with Pt as an interlayer. XPS confirmed the presence of Tb in two states, Tb3+ and Tb4+. The amorphous film has a rough, porous microstructure and is composed of large clusters of worm-like particles, while terbium oxide film consists of fine crystallites of cubic fluorite cF-TbOx, c-Tb4O7, and c-Tb2O3 phases. The surface topography was investigated by a combination of confocal (CM) and atomic force microscopy (AFM). The amorphous film is porous and rough, which is contrast to the crystalline terbium oxide film.

Recent Advances in Lanthanide Metal–Organic Framework Thin Films Based on Eu, Tb, Gd: Preparation and Application as Luminescent Sensors and Light-Emitting Devices

“…SEM and AFM micrographs of crystalline and amorphous films are presented in Figure 2. As shown in Figure 2a, particles of crystalline TbBTC powder with an average size of 300 nm (observed by TEM), were obtained with the use of a 0.4 mmol NaOAc modulator [71]. The SEM micrographs of cTbMOF (Figure 2b) reveal a straw-sheaf-like structure, which is in agreement with that reported in the literature [71].…”

“…The hydro/solvothermal growth of MOF-TFs is simple in preparation, feasible, efficient, and well reproducible deposition method and thus is commonly used for the production of electronic and optoelectronic devices [75]. A walkthrough of the general process step by step is depicted in Figure 1, in which upon heating, LnMOFs growth occurs rapidly on the substrate: bare-ITO glass-Eu/Tb-BTC film [40], one modified with platinum layer on SiO 2 /Si wafer-Tb-BTC, Eu 0.25 Gd 0.5 Tb 0.25 -BTC films, [71,72,76] and one with a seed layer of a UiO-66-NH 2 -Eu-BDC-NH 2 film [73]. The XRD data of Ln-BTC films are in good agreement with the tetragonal structure P 4 322 space group similar to Y(BTC)(H 2 O) [40,71].…”

“…A walkthrough of the general process step by step is depicted in Figure 1, in which upon heating, LnMOFs growth occurs rapidly on the substrate: bare-ITO glass-Eu/Tb-BTC film [40], one modified with platinum layer on SiO 2 /Si wafer-Tb-BTC, Eu 0.25 Gd 0.5 Tb 0.25 -BTC films, [71,72,76] and one with a seed layer of a UiO-66-NH 2 -Eu-BDC-NH 2 film [73]. The XRD data of Ln-BTC films are in good agreement with the tetragonal structure P 4 322 space group similar to Y(BTC)(H 2 O) [40,71]. The XRD peaks of the Eu-BDC-NH 2 film slightly shifted to a lower degree compared to that of UiO-66-NH 2 , which is mainly attributed to the larger ion size of Eu 3+ compared to the Zr 4+ [73].…”

“…Both the Tb-BTC crystalline (cTbMOF) and amorphous (aTbMOF) films were successfully prepared by solvothermal synthesis simply by changing the amount of NaOAc modulator used, that is, 0.4 and 0.7 mmol, respectively, according to our previous work [71]. The results of the syntheses are presented in Figure 2.…”

“…modulator used, that is, 0.4 and 0.7 mmol, respectively, according to our previous work [71]. The results of the syntheses are presented in Figure 2.…”