Effect of the Composition on the Nonlinear Optical Response of AuxAg1–x Nano-Alloys

The synthesis of variable composition AuxAg(1–x) alloyed nanoparticles prepared by laser ablation in water is reported. The nanoalloys exhibited a single characteristic surface plasmon resonance peak, whose spectral position was lying between the surface plasmon resonance peaks of neat Ag and Au nanoparticles, at about 400 and 530 nm respectively, depending directly on the composition of the alloyed nanoparticles. The nonlinear optical response of the nanoalloys was studied in details under 532 nm (visible) 35 ps and 4 ns laser excitation and it was found to be significant and greatly influenced by the position of the plasmonic band relative to the laser excitation wavelength. In this respect, increase of the Au molar fraction resulted in shifting of the nanoalloy plasmon band toward the location of the plasmon band of neat Au nanoparticles, i.e., at about 530 nm, closer to the laser excitation wavelength, hence causing more efficient resonance enhancement of the nonlinear optical response. Moreover, the ...