DEPOSITION OF SILVER PARTICLES ON THE SOLID SURFACES WITH THE PARTICIPATION OF BLOCK COPOLYMER OF POLYSTYRENE AND POLYETHYLENE GLYCOL

Abstract

Earlier the ability of obtaining of stabilized organosols in such systems as «toluene-water», «toluene-methanol» in presence of block copolymer of polystyrene and polyethylene glycol has been shown. In present investigation these disperse systems have been used in a mixture with precursor of silver nanoparticles (silver salt) and reducing agent (sodium citrate or hydrazine hydrate). Thus obtained silver sols have been put on a glass or graphite surfaces with subsequent removal of block copolymer by heating of samples in air to 500 °C. The dimension of obtained silver sols particles has been determined by means of sedimental turbidimetry (ST) and dynamic light scattering (DLS) methods. It has been shown that in silver sols obtained in the system «toluene-water-citrate» with the copolymer content of 0.25 and 1 g/100 ml have particle diameters of 800 and 1100 nm correspondingly. According to scanning electron microscopy (SEM) data the silver particles have spheric form. Their size does not depend much on the concentration of silver, but with an increase in the concentration of the copolymer, their size heterogeneity increases. The formation of spatial ordered structures of silver particles on the glass surface is noted, while the particles on the graphite surface are distributed more evenly. Using the system "toluene-methanol-block copolymer-silver salt-hydrazine hydrate" on the basis of thermally expanded graphite (TEG), a composite with a silver content of 130 mg/g was obtained and its effect on the activity of yeast fungi was evaluated. In comparison with the control samples (TEG and TEG treated with a similar dispersed system without the participation of a block copolymer), a decrease in foam formed in the column during fermentation of sucrose at 35 °C was found. Thus, it is shown that the block copolymer of polystyrene and polyethylene glycol promotes a more uniform deposition of silver particles from sols on the surface of graphite and can be used, in particular, to create materials with potential biological activity.