Preparation of composite Ag@Au core–shell nanoparticles and their linear and nonlinear optical properties
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We herein report the preparation of composite Ag@Au core–shell nanoparticles (NPs) through galvanic replacement reaction and the investigations of linear and nonlinear optical properties. TEM micrographs envisage the formation of core–shell NPs. EDS elemental mapping images demonstrate the homogeneous distribution of the elements and their chemical composition. The powder XRD pattern confirms the formation of highly crystalline composite Ag@Au core–shell NPs. The UV–Vis absorption spectrum shows contribution of Ag and Au characteristic absorption bands and the slight red shift provides the strong evidence for coating of Au shell over the Ag core. Moreover, the linear optical parameters such as the extinction coefficient, reflectance, refractive index, conductivity, susceptibility and polarizability are studied. z-scan analysis reveals the enhanced nonlinear optical properties of the composite Ag@Au core–shell NPs with nonlinear refraction coefficient (n2) being ten times higher than that of Ag NPs and eight times increase in comparison with that of Au NPs.
The author (Dr. M. Jose) thank the Department of Atomic Energy-Board of Research in Nuclear Sciences (DAE-BRNS), Government of India (Sanction No: 34/14/54/2014- BRNS) for providing Impedance spectroscopy analysis facility in the Department of Physics, Sacred Heart College (Autonomous), Tirupattur, India. The authors also gratefully acknowledge Prof. D. Sastikumar, Department of Physics, National Institute of Technology, Trichy for providing the z-scan facility.
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