PREPARATION OF BIMETALLIC AG-PD COLLOIDS FROM SILVER(I) BIS(OXALATO)PALLADATE(II)

Bimetallic silver-palladium colloids have been prepared by reduction of silver(I) bis(oxalato)palladate(II) with 253.7-nm UV light in the presence of poly(N-vinyl-2-pyrrolidone). The average particle size ranged from 3 to 11 nm in the 5 X 10(-3) mol dm-3 PVP system. The EDX profiles reveal that each particle is bimetallic Ag-Pd, although the composition is not uniform. The average composition shows a dependence on the concentration of Ag2[Pd(C2O4)2]; Silver becomes rich in colloid particles with an increase in the concentration. Optical spectra of these colloids show a plasma resonance band at 330-375 nm. The peak shift with changing composition of the bimetallic colloids is in qualitative agreement with Mie theory.