Silver nanowires as a result of irradiation or hydrogen reduction of Ag_3PW_(12)O_(4o) salt

摘要

We abstract report XPS, SEM and XRD investigations of the silver nanowires that are grown at the surface of the neutral silver salt of 12-tungstophosphoric acid (Ag_3PW_(12)O_(40)). Irradiation of the salt with electron or UV beams result in the formation of silver wires in the salt lattice and on the salt surface. The mechanical stress that appears during metallic silver phase formation leads to destruction of the crystal body. The same phenomena were observed after the reduction of Ag_3PW _(12)O_(40) in hydrogen. XRD analysis of the processed salts showed two additional reflexes of 2Θ at 38. 12° and 44. 28° that originate from the metallic silver phase. SEM analysis showed that the surfaces of the processed salts are covered by bunches of the wires. They show high aspect ratio and rather uniform distribution over the sample. XPS measurements were performed with the fresh and processed silver salts. Hydrogen reduction or irradiation of Ag_3PW_(12)O_(40) leads to significant changes in the main component of Ag 3d line. The quantity of the lattice Ag ~+ decreases after reduction, from 93 to 30%. Simultaneously, a new component (metallic silver) appears in the spectrum at a binding energy of 368. 0 eV. The amount of metallic silver on the surface of the reduced salt approaches 68% of the total silver concentration in the sample. The analysis of P 2p, O 1s and W 4f core excitations showed no qualitative differences after reduction, which means that the Keggin structure of the treated salt remains unchanged. The latter agrees well with XRD results.