Research paper Intercalation of lecithins for preparation of layered nanohybrid materials and adsorption of limonene Katalin Nagy a , Gábor Bíró a , Ottó Berkesi a , Dániel Benczédi d , Lahoussine Ouali d , Imre Dékány b, c, ⁎ a Department of Physical Chemistry and Materials Science, University of Szeged Aradi Vt. 1., H-6720 Szeged, Hungary b Institute of Medical Chemistry, Faculty of Medicine, University of Szeged, Aradi V.t.1., Szeged, Hungary c Supramolecular and Nanostructured Materials Research Group of the Hungarian Academy of Science, University of Szeged, Aradi Vt. 1., H-6720 Szeged, Hungary d Firmenich SA, Corporate R&D, 1211 Geneva 8, Switzerland abstract article info Article history: Received 14 November 2011 Received in revised form 12 November 2012 Accepted 21 November 2012 Available online 8 January 2013 Keywords: Montmorillonite LDH Intercalation Lecithin Lysolecithin Limonene The intercalation of biosurfactants (lysolecithin and lecithin) in layered clay mineral supports was investigat- ed to assess the suitability of the resulting nanohybrid materials as flavor and fragrance delivery system. The protonated biosurfactant molecules (pH = 2.3) were intercalated into the Na-montmorillonite, whereas the deprotonated biosurfactants (pH ~ 12) were intercalated into Mg–Al layered double hydroxides. The amount of lysolecithin and lecithin bound to the layered adsorbents was estimated by measuring adsorption iso- therms. The basal spacing obtained from X-ray diffraction measurements suggested that the molecules are arranged in parallel with the layers of montmorillonite, whereas in the case of layered double hydroxides, the adsorbed molecules are in a vertical position between the layers. The interaction of layered adsorbents and biosurfactants was further evidenced by infrared spectroscopy. The intercalated montmorillonite and LDH particles were then probed for their ability to intercalate limonene molecules. Only the lysolecithins modified samples adsorbed limonene. The theoretical sizes of molecules and their possible arrangement be- tween the layers were modeled by HyperChem 7.0 molecular calculations to correlate the ability to bind the lecithins in the confined space of the layered materials. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Layered clay minerals are used for their ability to intercalate certain molecules in cosmetic (López-Galindo et al., 2007) and health care products (Choy et al., 2007). The cations in the interlayer space of clay minerals may be exchanged for organic or inorganic cations. Surfactant ions are bound to the silicate surface via their polar groups, whereas their alkyl chains are arranged in a well-defined position in the interlayer space (Dékány and Haraszti, 1997; Lagaly and Dékány, 2005). The surface modification can be controlled through the carbon chain length of the cationic surfactant (Choy et al., 1997; Dékány et al., 1986), and/or through the extent of their surface coverage (Praus et al., 2006). Alexandre and Dubois (2000) synthesized intercalation and exfoliated nanocomposites by the addition of polymers. Ishii et al. (2006) studied the adsorption and desorption characteristics of nanocomposites containing a polymer or a fragrance ingredient. Aguzzi et al. (2007) studied the adsorption and desorption of cationic active agents of various molecular sizes on Na-montmorillonite clay mineral used extensively in studies involving retarded drug delivery. The smaller molecules were bound to the silicate layers less strongly than the larger molecules. When both molecules were tested in a competitive experimental setup, the larger molecules displaced the smaller ones from the interlayer space (Fejér et al., 2002). In desorp- tion studies the smaller molecules were more readily desorbed due to its weaker binding, whereas the desorption ratio of the larger mol- ecule was lower (Fejér et al., 2001). Protonated amino acids can be bound between montmorillonite layers by ion exchange (Kollár et al., 2003). Maximal amino acid uptake was observed in the range of pH=2–3(Theng, 1974). Fudala et al. (1999) studied the intercalation of L-tyrosine and L-phenylalanine on Zn–Al-LDH and Na-montmorillonite. The intercalated molecules can be detected by the increased basal spacing as determined by X-ray diffraction, whereas interactions between the guest molecule and the support can be evaluated by infrared spectroscopy (Fudala et al., 1999). In the case of fatty acids with different chain lengths on Na-montmorillonite the fatty acid with the longer carbon chain was more strongly bound to the surface (Freitas, et al., 2007). The layered double hydroxides (LDH) are anion exchangers. Their industrial production is relatively cheap and easy. The most impor- tant property of these synthetic minerals is the high anion exchange capacity (Dékány et al., 1997). LDHs can be hydrophobized by adsorp- tion or intercalation of surfactants (Dékány et al., 1997; Wang et al., 2005). The arrangement of guest molecules in the interlayer space is determined by their dimensions and functional groups (Khan and Applied Clay Science 72 (2013) 155–162 ⁎ Corresponding author at: Institute of Medical Chemistry, Faculty of Medicine, University of Szeged, Aradi V.t.1., Szeged, Hungary. Tel.: +36 62 544 209; fax: +36 62 544 042. E-mail address: i.dekany@chem.u-szeged.hu (I. Dékány). 0169-1317/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clay.2012.11.008 Contents lists available at SciVerse ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay