Optical properties and microstructure of silver-copper nanoparticles synthesized by pulsed laser deposition

Utilizing a pulsed laser deposition (PLD) method, silver-copper (Ag-Cu) nanoparticles have been synthesized by changing the surface area ratio of the target (S (R) = S (Cu)/(S (Ag) + S (Cu))) from 0 to 30%. The peak absorption attributed to surface plasmon resonance (SPR) increased when increasing S (R) up to 15%, above which it decreased. The peak shifts seem to be induced by the changes in the conductivity and morphology of the Ag-Cu nanoparticles. Additionally, the interplanar spacings of the Ag-Cu nanoparticles prepared at S (R) = 15% corresponded to the Ag {111}, {200}, {220}, and Cu {111} planes. However, since the interplanar spacings attributed to the Cu {200} and {220} planes were not detected, the Ag-Cu nanoparticles were believed to possess a lattice constant (a) close not to the Cu phase (a = 3.615 angstrom) but to the Ag phase (a = 4.086 angstrom). Moreover, confirming the presence of Cu atoms in the nanoparticles using energy dispersive X-ray (EDX) spectra, Ag-Cu nanoparticles may be a solid solution in which Cu atoms partially replace Ag atoms in the fcc structure.