Layered MPS₃ (M = Mn, Cd) Thin Films as Host Matrixes for Nonlinear Optical Material Processing

The possibility of processing MPS 3 (M = Mn, Cd) layered materials as thin films capable of intercalating nonlinear optical chomophores is investigated. Two different synthetic routes are presented. The first method (solution approach) involves the coprecipitation of transition-metal ions Mn 2+ with ligands (P 2 S 6 4- ) followed by casting on a glass substrate. Such films have a composition similar to the high-temperature-synthesized MnPS 3 phase but exhibit a much lower crystallinity. However, XRD patterns reveal a preferential orientation of the layers parallel to the support. The second process (solid-state approach) uses the ability of the MPS 3 layered compounds to be exfoliated through the successive intercalations of K + and Li + cations. The resulting compounds of formula M 1- x PS 3 Li 2 x · n H 2 O ( x = 0.18 for the manganese derivative and 0.16 for the cadmium derivative) readily form highly orientated thin films. Highly transparent thin films were obtained from the CdPS 3 starting material. The lithium intercalate thin films were characterized by thermogravimetric techniques, IR spectroscopy, and X-ray diffraction. Their mechanical stability was found to be slightly better than that of the solution-approach-based thin films. The intercalation of a nonlinear optical chromophore (4-[4-(dimethylamino)-α-styryl]-1-methylpyridinium) was performed in these thin layered films, which were found to be much more reactive that the parent bulk MPS 3 .