Luminescent Eu^III Complexes Immobilized on a Vermiculite Clay Surface

Abstract

Vermiculite clays were leached with nitric acid and functionalized with (3‐chloropropyl)trimethoxysilane. The resulting materials were modified with the methylimidazolium (MID) group to yield cationic surfaces. These materials were characterized by infrared spectroscopy, elemental analyses, and specific surface area. Tetrakis(β‐diketonate)europate(III) complexes, [EuL4]– [L = dibenzoylmethane (DBM) and thenoyltrifluoroacetone (TTA)], were immobilized on the vermiculite surface containing the imidazolium cation to yield hybrid surfaces named Vx‐MID‐EuL4 (x = 0, 1, and 2), in which x represents the acid nitric concentration in mol L–1 that is used in the leaching process. The highest luminescence intensities of the intraconfigurational‐4f 5D0→7FJ transitions (for which J = 0, 1, 2, 3, and 4) arising from [EuL4]– complexes were presented by the hybrid materials containing the amount of imidazolium cation, which depend on the leaching process. The excitation and emission spectra suggested an efficient intramolecular energy‐transfer process from ligand‐to‐Eu3+ ion in the supported materials. The photoluminescent properties of the hybrid materials were investigated based on the emission quantum efficiency (η), experimental intensity parameters Ω2 and Ω4, and Einstein's emission coefficient (A0J). The values of these parameters for the V2‐MID‐EuL4 surface are close to those assigned to the [EuL4]– isolated complexes, which indicates that hybrid vermiculite materials are promising red phosphors.

Luminescent Hybrid Materials Based on Laponite Clay

“…[13,[22][23][24][25][26] Recently, complexes have also been used to modify clay minerals. [27][28][29][30][31][32][33][34] As opposed to zeolites, the cavities of which are typically rigid, guest species are accommodated in interlayer space between two "hard" layers; the interlayer space can to some extent be flexibly adjusted by the accommodated guest species. [27] Currently, increased interest is being focused on artificial nanosized clays such as Laponite, which is a synthetic smectic clay with very similar structure and composition to the natural clay mineral hectorite.…”

Experimental design investigation for vermiculite modification: Intercalation reaction and application for dye removal

“…Atomic absorption spectroscopy was performed on a Perkin-Elmer 5100 instrument with an air-acetylene flame after previous digestion of samples with an acidic mixture of HF/HNO 3 and HCl. The silicon and aluminum contents were analyzed gravimetrically after fusion with sodium carbonate, as previously described (Silva et al, 2014). X-ray powder diffraction patterns of random samples were obtained in a Shimadzu XRD-7000 diffractometer at 30 kV and 30 mA with nickel-filtered CuKα (α = 0.154 nm) radiation in the range from 3.0°to 80°for 2θ, at a scan rate of 0.60°s − 1 , step size of 0.03°and counting time 1 s per step.…”

“…Therefore, acid-activated solids have altered structural properties, and their applications can be improved. Acid-activated vermiculites were applied as precursors for clay-polymer nanocomposites, adsorbents (Hashem et al, 2015), catalysts (Chmielarz et al, 2012), catalytic supports (Jin and Dai, 2012) and luminescent species (Silva et al, 2014).…”

Relationship between Textural Parameters of Lamellar Products Obtained by Acid Activation of Pure and Commercial Vermiculites and Their Iron and Water Content

“…These studies have shown that the resulting products have high specific surface area and porosity [27,29] and are useful in various applications. They can be used as selective adsorbents for specific contaminants from wastewater [24,[29][30][31], support for luminescent complexes [32], and selective catalysts for NO reduction [27].…”