A novel method for synthesis of clay/polymer stabilized silver nanoparticles

Silver nanoparticles were synthesized with clay mineral (montmorillonite)/PVP (polyvinyl pyrrolidone) suspensions using an electrochemical approach. The polymer and exfoliated clay mineral solution protect and prevent aggregation of the silver nanoparticles. The clay mineral component is environmentally friendly and low cost. Unlike other studies, the clay platelets are exfoliated (sheared apart to individual platelets) to expose a much larger surface area and function as supporting material and stabilizer. A prime advantage of this novel approach is that the polymer and layered silicates protected the silver nanoclusters from agglomerating, effectively immobilizing and enhancing contact with the cathode for reduction. An electrochemical approach for nanoparticle synthesis has several advantages; including control and tuning of the experimental parameters, easy set-up, and short synthesis times. Morphology of the silver nanoparticles depended on current density of the electrochemical synthesis. Transmission electron microscopy showed small spherical silver nanoparticles formed at current densities below 1.25 mA/cm2 and silver dendritic formation at current densities greater than 2.5 mA/cm2. Size distribution of nanocomposites in solution measured by dynamic light scattering was 27 nm for the silver nanoparticles. X-ray diffraction was used to measure the crystallite size of the dried powders, which ranged between 10 and 60 nm depending on the experimental parameters. Nanocomposite coatings were also formed on graphite foil electrodes. Dense uniform films of spherical silver nanoparticles were produced at low current densities (<1.25 mA/cm2), while aggregates formed at higher current densities (>2.0 mA/cm2).