Research paper Layered titanosilicates JDF-L1 and AM-4 for biocide applications Javier Pérez-Carvajal, Patricia Lalueza, Clara Casado, Carlos Téllez, Joaquín Coronas ⁎ Department of Chemical and Environmental Engineering and Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza, Spain abstract article info Article history: Received 29 June 2011 Received in revised form 11 November 2011 Accepted 16 November 2011 Available online 20 December 2011 Keywords: Titanosilicate JDF-L1 AM-4 Ion exchange Biocide Layered materials JDF-L1 and AM-4 are porous layered titanosilicates that can be modified by ion exchange while keeping the crystallinity. In this study, JDF-L1 and AM-4 were exchanged with Ag + , Zn 2+ and Cu 2+ ions and characterized by XRD and TEM. JDF-L1 exchanged titanosilicate preserved the crystalline structure while AM-4 exchanged titanosilicate showed a certain loss of crystallinity. In the case of Ag-exchanged samples, the Ag nanoparticles were distributed at the edges of the JDF-L1 crystals whereas they were distributed around the AM-4 particles. The antimicrobial activity was tested with Staphylococcus aureus. All the exchanged titanosilicates showed good antimicrobial activity against the bacteria and the most active was Ag–AM-4. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Metal cations and especially silver ions were long used to prevent or treat infections. Around 1000 B.C., silver was used to produce pota- ble water (Castellano et al., 2007; Richard et al., 2002). In the 18th century, silver nitrate was employed for the treatment of different microbial infections such as venereal diseases, fistulae from salivary glands, bone and perianal abscesses (Klasen, 2000; Landsdown and Williams, 2007). In 1800, silver nitrate was also applied to remove granulation tissues. This allowed epithelization to take place and the formation of a crust on the surface of wounds. Moreover, silver nitrate was also recognized as a good tool to treat fresh burns (Castellano et al., 2007; Klasen, 2002). During World War II, penicillin was widely introduced and the use of silver as antimicrobial agent diminished (Demling and DeSanti, 2001; Hugo and Russell, 1982). Nevertheless, due to the emergence of antibiotic-resistant bacteria and the stronger control of the use of antibiotics (Chopra, 2007; Gemell et al., 2006), silver recently regained importance as an antimicrobial. Different forms of silver were found in the literature. Silver nano- particles showed antimicrobial properties that were size-dependent. The smaller they were, the greater their bactericidal effect due to their better ability to penetrate the bacteria (Morones et al., 2005; Panacek et al., 2006). Silver sulfadiazine was reported as a good reser- voir from which silver was slowly released (Rai et al., 2009). The ac- tion mechanism of silver ions is not yet well known. Although different mechanisms were proposed, silver ions on bacteria effected several morphological and structural changes in the cells: (i) by inter- acting with the peptidoglycan and lipids of the cell membrane, silver inhibited the respiration chain and, in this way, reactive oxygen spe- cies (ROS) were generated, which could damage the bacterial cell it- self (Matsumura et al., 2003); (ii) by binding of the silver ions to DNA phosphate groups the functions of replication and transcription could be lost. When the silver ions penetrated inside the bacterial cell, the DNA molecule turned into a condensed form to protect itself limiting of the replication ability and finally leading to cell death (Feng et al., 2000); and (iii) silver ions interacting with thiol groups to proteins and enzymes inhibiting their functions (Matsumura et al., 2003). Clay minerals are abundant and versatile materials that can be as- sembled in nanometer scale to a large diversity of organic compounds yielding nanostructured hybrid materials, by mechanisms ranging from ion exchange to covalent bonding, with growing applications in environment and biomedicine (Ruiz-Hitzky et al., 2010). Other antimicrobial materials used were TiO 2 , ZnO and copper nanoparticles. TiO 2 was used as a semiconductor catalyst activated by UV radiation and, in this way, producing ROS, so that the antibac- terial action was inhibited (Kikuchi et al., 1997). ZnO nanoparticles also showed a wide range of antibacterial activity on a large amount of bacteria but their mechanism is yet less understood than that of sil- ver and silver ions (Sawai, 2003). Copper nanoparticles were embed- ded in particles of sepiolite but the anti-bacterial activity was lower than that of silver nanoparticles (Dastjerdi and Montazer, 2010). Other antimicrobial materials were silver-exchanged zeolites (Lalueza et al., 2011; Matsumura et al., 2003), where even very low concentrations, such as 0.2 mass % silver in silver-exchanged ZSM-5, caused bactericidal activity (Lalueza et al., 2011). Other zeolite Applied Clay Science 56 (2012) 30–35 ⁎ Corresponding author. Tel.: + 34 976 762471; fax: + 34 976 761879. E-mail address: coronas@unizar.es (J. Coronas). 0169-1317/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2011.11.020 Contents lists available at SciVerse ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay