14236 Phys. Chem. Chem. Phys., 2010, 12, 14236–14244 This journal is c the Owner Societies 2010 Synthesis and characterization of low dimensional ZnS- and PbS-semiconductor particles on a montmorillonite templatew L ˇ ubosˇ Jankovicˇ ,* ab Konstantinos Dimos, b Juraj Bujda´k, a Ioannis Koutselas, bc Jana Madejova´, a Dimitrios Gournis, b Michael A. Karakassides b and Peter Komadel a Received 10th February 2010, Accepted 29th July 2010 DOI: 10.1039/c002891f Low dimensional metal sulfide particles have been prepared in the interlayers of montmorillonites via reactions of the metal ion-exchanged clay minerals in aqueous dispersions with gaseous hydrogen sulfide. The montmorillonites separated from the Wyoming (USA) and Jelsˇovy´ Potok (Slovakia) bentonites were saturated with Pb 2+ or Zn 2+ . In the final nanohybrids, the smectite mineral can be incorporated with metal sulfide pillars and/or nanoparticles. Properties of the prepared materials were investigated by various analytical techniques. The formation of metal sulfide nanoparticles in the interlayer galleries was indicated by X-ray diffraction and energy dispersive X-ray analysis. About 50% of Pb 2+ or Zn 2+ present in montmorillonite has formed metal sulfide semiconducting units. Infrared spectroscopy and thermogravimetric analysis were used for characterization of starting materials and products. Ultraviolet-visible absorption and photoluminescence spectroscopies confirmed that final composite systems acquired the optical properties of the incorporated quantum low dimensional systems exhibiting blue shift of the energy gap and higher oscillator strength excitonic peaks. Larger amounts of metal sulfide nanoparticles were formed in montmorillonite Jelsˇovy´ Potok probably as a consequence of its higher cation exchange capacity. 1. Introduction Expandable clay minerals such as smectites have extensive applications due to their swelling, adsorption and ion exchange properties and high surface areas. 1 The most commonly used clay mineral is montmorillonite (MMT), which has two siloxane tetrahedral sheets sandwiching an octahedral sheet with Al(III) as dominant cental atoms. Due to the isomorphic substitutions, typically Mg(II) for Al(III) in the octahedra and Al(III) for Si(IV) in the tetrahedra, the layers are negatively charged. This is counterbalanced by hydrated exchangeable cations, such as Ca 2+ or Na + , within the interlayer space and on the external surfaces. The intercalation process in these systems often proceeds via ion exchange and, in contrast with intercalation compounds of graphite, does not necessarily involve charge transfer between the guest and host species. One possibility to modify the surface and chemical properties of MMTs is by replacing the natural inorganic cations with other cations. This process may alter both the surface and pore structure of the minerals. 2 Surface modifications of clay minerals have received much attention because they can lead to new materials and new applications such as adsorbents of organic pollutants in soils, water and air, rheological control agents, paints, cosmetics, personal care products, refractory varnish, thixotropic fluids, etc. 3–4 The nature of the micro- environment between the aluminosilicate sheets regulates the topology of the intercalated molecules and affects possible supramolecular rearrangements or reactions that are usually not easily controlled in the solution phase. 5–7 Layered silicates are also eminently suitable for the preparation of particles with a diameter of a few nanometres on the surface and in the interlamellar space in aqueous dispersions. Inorganic nanoparticles are most conveniently grown on the clay mineral surface by displacing the exchangeable cations with precursor transition metal cations and by subsequent reaction. The adsorption layer at the solid/liquid interface was employed earlier as a ‘nanophase reactor’ for the generation of nano- crystalline metal particles and for their stabilization in the presence of the clay mineral. 8 The nanoparticles can be grown attached to the surface in well controllable number and size between the silicate layers. Semiconductor nanocrystals have attracted considerable attention in recent years because of their size- and shape-dependent optical and electronic properties as well as their potential for applications in nanodevices. Metal sulfides (MS) belong to the most important semiconductors and have potential applications in numerous areas including optoelectronics, 9 photocatalysis, 10 and thin-film electroluminescent devices. 11 Many reports appeared on attempts to control the size and morphology of metal sulfides including solvothermal routes, 12 thermal evaporation, 13 reverse micelle templates, 14 as well as intercalation a Institute of Inorganic Chemistry, Slovak Academy of Sciences, Du ´bravska ´ cesta 9, SK-845 36 Bratislava, Slovakia. E-mail: Lubos.Jankovic@savba.sk; Fax: +421-2-59410444; Tel: +421-2-59410459 b Department of Materials Science & Engineering, University of Ioannina, GR-45110 Ioannina, Greece c Department of Materials Science, University of Patras, GR-26504 Patras, Greece w Electronic supplementary information (ESI) available: Experimental data. See DOI: 10.1039/c002891f PAPER www.rsc.org/pccp | Physical Chemistry Chemical Physics