CYCLOBIS(PARAQUAT-P-PHENYLENE) - MEDIATED ELECTROSYNTHESIS OF SILVER NANOPARTICLES

Abstract

Silver nanoparticles (Ag-NP) were obtained in MeCN/0.05 M Bu4NPF6 medium by сyclobis(paraquat-p-phenylene) (CBPQT4+) – 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 CBPQT4+ binds the resulting electron-donor Ag-NP to each other, which leads to their enlargement, aggregation and adsorption. This property of the macrocycle allows to call it a “molecular glue” for NP-Ag. In the absence of stabilizers, aggregated polydisperse Ag-NP of indefinite shape are formed with sizes ranging from 20 to 500 nm. Electrosynthesis in the presence of a stabilizer, polyvinylpyrrolidone (PVP), also leads to the formation of aggregated smaller metal particles of 55 ± 26 nm, which have, in addition to the quasi-spherical shape, the shape of a flat triangle and hexagon. Ag-NP stabilized by PVP are partially bound on the surface of nanocellulose (NC). In the presence of NC, larger Ag-NP with an average size of 97 ± 29 nm are formed, the main shape of which is quasi-spherical; cubic, tetrahedral, and rod-shaped Ag-NP are also formed; the formation of Ag-NP with a flat structure is excluded. The catalytic activity of the obtained particles in the reduction of p-nitrophenol with sodium borohydride is extremely low due to the large size, aggregation, and coating of the NP-Ag surface with the stabilizer PVP and marcocycle.