Shape-controlled silver metal of nanospheroids from a polymer-assisted autocombustion reaction in open air

Nanospheroids of silver, D = 18–27 nm diameters, have been synthesized following an autocombustion reaction of a polymer complex of polyvinyl alcohol (PVA) containing Ag+ → Ag species in open air. It is shown that, when heating with Ag+ species in water, PVA molecules induce a local Ag+ → Ag reaction, forming such a complex of Ag-nanoparticles dispersing in situ in the PVA molecules. A viscous sample (hot) could be cast and dried in 3–5 wt.% Ag-PVA films (50–100 μm thickness) at room temperature. Ag metal of nanospheroids occurs upon heating 5–10 mm pieces of the films over 300–500 °C in air. According to the X-ray diffraction, it has an Fm3m cubic crystal structure. After 300 °C, the sample consists of small crystallites (D = 24 nm), with the lattice parameter a = 0.4071 nm (density ρ = 10.618 g/cm3), which relaxed nonlinearly to a value 0.4085 nm (ρ = 10.509 g/cm3) upon D-value growing to be as large as 27 nm over higher temperatures.