Optical-Quality Thin Films with Tunable Thickness from Stable Colloidal Suspensions of Lanthanide Oxysulfide Nanoplates

Abstract

In modern laser technologies, there is a need for coatings that would be compatible with flexible substrates while retaining the advantages of inorganic compounds in terms of robustness. As a first step in this direction, we developed here thin films of lanthanide oxysulfide, of optical quality, prepared by low-temperature dip coating. As a model compound in the family of oxysulfides, (Gd,Ce)2O2S anisotropic nanoplates were used. The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and in situ UV and IR spectroscopic ellipsometry, showing that the band gap of the materials was preserved through the deposition process. The thickness of the films was tuned in a broad range, from a few nanometers to 150 nm, using different concentrations of the colloidal suspensions as well as single-layer and multilayer deposition. Lastly, thermal treatment of the thin films was optimized to remove the stabilizing organic ligands of the nanoparticles while preserving their integrity, as confirmed by SEM and XRD.

From Ln2O2S to Ln10OS14: exploring the sulphur spectrum of trivalent lanthanoid oxysulphides

“…Since the first elucidation of the structure of an oxysulphide in 1947, 1 these materials have been extensively studied due to their multitude of technological applications as colour-tunable phosphors, 2 sulphur-tolerant 3 catalyst supports for the water gas shift reaction, 4 and in magnetism 5 and luminescence thermal sensing. [6][7][8][9] While the compositional space is large, Ln 2 O 2 S has been the most widely explored stoichiometry, [10][11][12] and considerably less information is available on its remaining congeners. 13,14 The Ln 2 O 2 S 2 crystal structure was only recently understood owing to the disorder present in the disulphide layer.…”

Controlled Synthesis of Terbium-Doped Colloidal Gd2O2S Nanoplatelets Enables High-Performance X-ray Scintillators

“…Nanoplatelets (NPLs) are usually formed during the colloidal synthesis of RE 2 O 2 S, which can be attributed to their hexagonal crystal structure. This technique has been utilized for several RE 2 O 2 S compositions, including La, Eu, Ce, Gd, Yb, and Y. − However, current colloidal Gadox synthesis methods offer limited control over the shape, size, and thickness of the NPLs, as well as very low photoluminescence quantum yield (PLQY). ,,− Consequently, due to their low PLQY, Gadox NPLs seemed impractical for X-ray applications because of their expected low light yield (LY). However, we posit that the low PLQY and the lack of control over shape, size, and Tb 3+ concentration are interrelated.…”