Vertically aligned Gd2O2SO4:Ln and Gd2O2S:Ln luminescent films with super-hydrophobicity via a novel precursor route (Ln = Pr, Eu, Tb)

Pr3+, Eu3+ and Tb3+ activated Gd2O2S (Gd2O2S:Ln), either in the powder or ceramic form, are well known for their wide applications in photoluminescence (PL), cathodoluminescence (CL) and X-ray excited luminescence (XEL) due to high efficiency. The film form of Gd2O2S:Ln, however, has not been reported up to date to the best of our knowledge. By hydrothermally reacting Gd(NO3)(3), (NH4)(2)SO4 and urea, this work produced a Gd-2(OH)(2)CO(3)SO4 center dot H2O new compound (GOCSH) that was crystallized in the tetragonal system (space group P-42(1)m) with a layered structure along the [001] crystallographic direction. Furthermore, macroscopically and microscopically uniform GOSCH:Ln films, constructed by vertical self-alignment of platelike crystallites, were successfully fabricated by applying heterogenous nucleation on quartz substrate. Taking the advantage of the exactly the same S/(Gd,Ln) molar ratio, Gd2O2SO4:Ln and Gd2O2S:Ln films of the same microstructures were then derived from the GOSCH:Ln films by annealing in air and hydrogen at 800 degrees C, respectively, without any additional sulfurization. The mechanism of film formation and the influence of deposition/annealing temperature on film quality were discussed. Aside from luminescence, the films all have microstructure-enabled super-hydrophobicity and are transparent in the visible light region (similar to 70-93%). The multi-functional films, particularly those of Gd2O2S:Ln, may find potential application in luminescence, display, scintillation and microimaging.