http://www.revmaterialeplastice.ro MATERIALE PLASTICE ♦55♦No. 1 ♦2018 63 Luminescent Hybrid Materials Based on Curcumin Derivatives Embedded in Palygorskite MONICA FLORENTINA RADULY, VALENTIN RADITOIU, ALINA RADITOIU, LUMINITA EUGENIA WAGNER*, VIORICA AMARIUTEI, CRISTIAN ANDI NICOLAE Research and Development National Institute for Chemistry and Petrochemistry - ICECHIM, 202 Splaiul Independentei, 060021, Bucharest, Romania The seven curcumin derivatives were deposited on palygorskite in order to obtain hybrid materials. The fluorescence emission spectra of the obtained materials show a decrease in fluorescence intensity relative to the respective dyes, due to the environments around the dyestuff molecules created in the host matrices. Absorption studies show the best adsorption on the inorganic matrix, for the compounds with the hydroxyl groups. Correlating fluorescence spectra of hybrid materials with the results for absorption spectra of the dyes adsorbtion on the surface of the clay lead to the conclusion that a high percentage of the adsorbed dye had the effect of fluorescence quenching. Thus, it was confirmed that the fluorescent properties of hybrid materials depend on the interactions established between the fluorescent dyestuff and the inorganic network. Keywords : curcumin, chromogens, hybrid materials, fluorescent properties, palygorskite Curcumin is a natural yellow coloured compound known for centuaries, extracted from the rhizome of Curcuma species, was used initially as a textile dye [1,2] and then used in diet as a spice or additives [3]. Curcumin applicability has been extended due to their antioxidant, anti-inflammatory and anticancer properties in biomedical domain [4-6]. In the recent years to develop and diversify curcumin derivatives with improved properties in terms of photostability and with increased efficiency of fluorescence emission, were made structural changes on the curcumine skeleton by alkylation, acylation or as metal-complexes [7]. Several curcumin derivatives have been incorporated into inorganic networks (porous materials, natural or synthetic zeolites), thus obtaining hybrid materials with improved photochemical properties for non-conventional applications [8-11]. In many studies on the adsorption of dyes on clays, palygorskite (or attapulgite) was used as an efficient adsorbent [12-14]. Palygorskite (PAL) clay is a natural white-gray, with high hydrophilic properties, abundant in nature and relatively inexpensive. Depending on the area from which the palygorskite comes, it may contain iron, calcium, potassium and sodium ions in various proportions, [Mg (Al 0.5-1 Fe 0-0.5 )] Si 4 O 10 (OH) ·4H 2 O (chemical composition: SiO 2 50-68%; Al 2 O 3 9-12%; MgO 3-12%; Fe 2 O 3 3-5%). Due to its structure containing open channels, the palygorskite falls within the category of porous materials, with a surface area that varies between 75-400m 2 /g [15,16]. Due to it lamellar structure, the palygorskite has remarkable properties for chemical stability and durability when exposed to various external factors. These properties have made it to be used in studies aimed at obtaining luminescent nanocomposites [17] and in biological applications [18]. * email: luminitawagner@yahoo.com Based on these considerations, this study is intended to provide data on obtaining hybrid materials with luminescent properties by depositing of the curcumin derivatives on an inorganic matrix. The curcumin derivatives were previously synthesized in the microwave field, purified and characterized [19]. Experimental part The present paper illustrates experimental data regarding synthesis and characterization of seven new organic-inorganic hybrids obtained by curcumin derivatives (fig.1) depositing on surface of palygorskite inorganic matrix. All of the chemicals used were of laboratory reagent grade and were obtained from Merck (Germany) and Aldrich (USA). Methanol (MeOH), hexadecyltrimethyl- ammonium bromide (CTAB), and hydrochloric acid (0.1 N) were used as they were received without further purification. The Palygorskite (PAL) clay used in this study was obtained from SERVA (Germany). The curcumin derivatives (cc1-cc7) were deposited on PAL previously modified with hydrochloric acid and hexadecyltrimethylammonium bromide (CTAB) [13,18]. Surface treatment of palygorskite PALs were activated in a 5 M HCl solution at 100 0 C for 4h, and then washed with water until neutral p H. Afterwards the crude product was dried at 120 0 C for 5 h in order to get activated PALs. CTAB (0.01 mol) was dissolved in water (300 mL) at p H = 3 and 60 0 C, and after complete dissolution it was added Palygorskite (10 g) and then stirred at 60 0 C for 12 h. The dispersion was filtered, washed with water to p H = 7 and dried at 120 0 C for 24 h. Fig.1 Structural formula of curcumin derivatives