Spectral Tuning of Plasmon Resonances of Bimetallic Noble Metal Alloy Nanoparticles Through Compositional Changes
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Spectral Tuning of Plasmon Resonances of Bimetallic Noble Metal Alloy Nanoparticles Through Compositional Changes Jayanta K. Majhi 1 & Probodh K. Kuiri 2 Received: 7 August 2019 / Accepted: 4 December 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract The optical absorption properties of the bimetallic noble metal alloy (viz. Au-Ag, Au-Cu, and Ag-Cu) nanoparticles (NPs) of radii of 10 nm and 20 nm embedded in silica glass have been studied theoretically using a simple model based on the effective medium theory. Our study reveals that the spectra of the above bimetallic alloy NPs exhibit single but composition-sensitive surface plasmon resonance (SPR) peak which indicates the successful formation of alloys. The position of the SPR peak that appeared corresponding to alloy NPs is different from that of the component metals. The study further reveals that the Ag-Au and Au-Cu alloy systems are completely miscible over the entire concentration range but Ag-Cu is miscible up to a certain extent, although, their SPR peak shows a linear shift with molar concentration. It has been further observed that the phase of the Ag-Au alloy system changes with concentration of Au during the alloy formation but no such change is seen in the other two systems. Thus, our study shows that the Ag-Cu system which otherwise does not form alloy in bulk may form alloy in nanoscale with limited miscibility. A shift of the SPR peak positions from ~ 405 to ~ 535 nm for Au-Ag, from ~ 535 to ~ 590 nm for Au-Cu, and from ~ 405 to ~ 436 nm for Ag-Cu NP systems has been observed for different composition of constituent monometals. The compositional changes lead to a spectral tuning of the SPR of the system under studies. Keywords Noble metal nanoparticles . Alloys . Surface plasmon resonance . Peak shift
Introduction The research in plasmonics has initially been started on Au and Ag nanoparticles (NPs) due to their strong plasmonic behavior in an embedding medium as well as low losses in the visible to near infrared (IR) region of electromagnetic spectrum [1, 2]. However, there are some limitations in respect of chemical stability and cost as an individual plasmonic material based on elemental metals [2]. Therefore, the material cost, its stability, and availability or abundance are the most important factors to be remembered while considering the individual noble metal as a plasmonic material for various plasmonic applications. Such limitations of individual noble metal have been overcome by combining them to form bimetallic alloys and core shell NPs [3]. Alloy NPs exhibit * Probodh K. Kuiri [email protected] 1
Department of Physics, Banwarilal Bhalotia College, Asansol, West Bengal 713303, India
2
Department of Physics, Sidho-Kanho-Birsha University, Purulia, West Bengal 723104, India
electronic, optical, and catalytic properties that are distinctive from those of the corresponding monometal NPs. Furthermore, using the alloy NPs, tunable physical properties can be obtained by varying the composition ratio of NP
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