Synthesis of bimetallic core/shell nanoparticles via pulse laser ablation and their catalytic effectiveness in dye degradation

In this study, a simple two step method is employed to sequentially synthesize bimetallic core/shell nanoparticles (NPs). In the first step, pure mono Au and Ag NPs are prepared via 1064 nm pulsed laser ablations in liquid. In the second step, the Au/Ag substrate immersed in the Au/Ag colloidal solution is exposed to the nanosecond laser at 1064 nm wavelength using various laser energies and ablation periods. The crystalline phase and morphology of the bimetallic core/shell NPs (Au/Ag, Ag/Au) are examined by x-ray diffraction and scanning electron microscopy, respectively. The results showed that highly crystalline, well-dispersed spherical monometallic and bimetallic core/shell NPs can be synthesized via pulse laser ablation in liquid. The average diameter of Au, Ag, Au/Ag, and Ag/Au NPs is 34, 40, 58, and 43 nm, respectively. With increasing laser energy, the plasmonic absorption peak of Au NPs redshifts and that of Ag NPs blueshifts. For core/shell, two plasmonic peaks were observed, each of which shifted with increasing ablation time for shell material. Organic dyes with concentrations of 10−5M of methylene-blue with NaBH4 of 0.05M and methylene-orange with NaBH4 of 0.1M are used to examine the catalytic performance of the NPs. The core/shell NPs performed better than monometallic NPs. In particular, the catalytic degradation efficiency of Au/Ag and Ag/Au NPs is approximately 90% in significantly less time than monometallic Au and Ag NPs.