Synthesis and characterization of low dimensional ZnS- and PbS-semiconductor particles on a montmorillonite template

Abstract

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 Jelšový Potok (Slovakia) bentonites were saturated with Pb²⁺ or Zn²⁺. 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 Pb²⁺ or Zn²⁺ 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 Jelšový Potok probably as a consequence of its higher cation exchange capacity.