Cyclobis(Paraquat-p-Phenylene)-Mediated Electrosynthesis of Silver Nanoparticles.

Silver nanoparticles were obtained in MeCN/0.05 M Bu4NPF6 medium by сyclobis(paraquat-p‑phenylene)-mediated reduction of the silver ions generated by anodic oxidation of metallic silver during the electrolysis in an undivided cell. Due to multipoint donor–acceptor interaction, the сyclobis(paraquat-p‑phenylene) binds the resulting electron-donor silver nanoparticles to each other, which leads to their enlargement, aggregation, and adsorption. This property of the macrocycle allows calling the сyclobis(paraquat-p-phenylene) a molecular glue for silver nanoparticles. In the absence of stabilizers, aggregated polydisperse silver nanoparticles of indeterminate shape are formed, sized 20 to 500 nm. Electrosynthesis in the presence of polyvinylpyrrolidone as a stabilizer also leads to the formation of aggregated smaller (55 ± 26 nm) metal particles which have, in addition to the quasi-spherical shape, the shape of a flat triangle and hexagon. Silver nanoparticles stabilized by polyvinylpyrrolidone are partially bound on the surface of nanocellulose. In the presence of nanocellulose, larger silver nanoparticles with an average size of 97 ± 29 nm are formed, mainly shaped quasi-spherical; cubic, tetrahedral, and rod-shaped silver nanoparticles are also formed; no silver nanoparticles with a flat structure has been formed. The catalytic activity of the obtained particles in the reduction of p-nitrophenol by sodium borohydride is extremely low due to their large size, aggregation, and coating of the silver nanoparticles' surface with the stabilizer polyvinylpyrrolidone and macrocycles. [ABSTRACT FROM AUTHOR]