Barium praseodymium tungstate (Ba 1-x Pr 2x/3 )WO 4 crystals with (x = 0, 0.01, and 0.02) were prepared by the coprecipitation method. These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinements, Fourier-transform Raman (FT-Raman) and Fourier-transform infrared (FT-IR) spectroscopies. The shape and size of these crystals were observed by field emission scanning electron microcopy (FE-SEM). Their optical properties were investigated by ultraviolet visible (UV-vis) absorption and photoluminescence (PL) measurements. Moreover, we have studied the photocatalytic (PC) activity of crystals for degradation of rhodamine B (RhB) dye. XRD patterns, Rietveld refinements data, FT-Raman and FT-IR spectroscopies indicate that all crystals exhibit a tetragonal structure without deleterious phases. FT-Raman spectra exhibited 13 Raman-active modes in a range from 50 to 1000 cm 21 , while FT-IR spectra have 8 infrared active modes in a range from 200 to 1050 cm 21 . FE-SEM images showed different shapes (bonbon-, spindle-, rice-and flake-like) as well as a reduction in the crystal size with an increase in Pr 3+ ions. A possible growth process was proposed for these crystals. UV-vis absorption measurements revealed a decrease in optical band gap values with an increase of Pr 3+ into the matrix. An intense green PL emission was noted for (Ba 1-x Pr 2x/3 )WO 4 crystals (x = 0), while crystals with (x = 0.01 and 0.02) produced a reduction in the wide band PL emission and the narrow band PL emission which is related to f-f transitions from Pr 3+ ions. High photocatalytic efficiency was verified for the bonbon-like BaWO 4 crystals as a catalyst in the degradation of the RhB dye after 25 min under UV-light. Finally, we discuss possible mechanisms for PL and PC properties of these crystals.

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The search for functional materials has increased daily in order to improve their functionality while maintaining a low cost. Among the materials of considerable interest are clays and within them is a particular clay known as palygorskite, which contains a hydrated silicate of aluminum and magnesium with a fibrous morphology. This work achieved the organofunctionalization of palygorskite with ethylene sulfide in the absence of a solvent. Through the elemental analysis of sulphur, the incorporation of 9.73 ± 0.36 mmol g-1 was identified. A significant decrease in the crystallographic planes (110) and (040) was identified in the XRD. The FTIR showed vibrations of stretching and deformation of the methylene groups in the region below 3000 and in 1421 cm-1, respectively. The deformation related to the C-S group in the region of 700 and 600 cm-1, and the surface area (BET) showed a significant reduction from 113 to 7 m2 g-1. Additionally, the SEM presented a loss of fibrous character.