Optical and Magnetic Properties of Ag-Ni Bimetallic Nanoparticles Assembled via Pulsed Laser-Induced Dewetting

David A Garfinkel; Grace Pakeltis; Nan Tang; Ilia N Ivanov; Jason D Fowlkes; Dustin A Gilbert; Philip D Rack

doi:10.1021/acsomega.0c02894

Optical and Magnetic Properties of Ag-Ni Bimetallic Nanoparticles Assembled via Pulsed Laser-Induced Dewetting

ACS Omega. 2020 Jul 21;5(30):19285-19292. doi: 10.1021/acsomega.0c02894. eCollection 2020 Aug 4.

Authors

David A Garfinkel¹, Grace Pakeltis¹, Nan Tang¹, Ilia N Ivanov², Jason D Fowlkes^{1

2}, Dustin A Gilbert¹, Philip D Rack^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.
² Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.

Abstract

Pulsed laser-induced dewetting (PLiD) of Ag_0.5Ni_0.5 thin films results in phase-separated bimetallic nanoparticles with size distributions that depend on the initial thin film thickness. Co-sputtering of Ag and Ni is used to generate the as-deposited (AD) nanogranular supersaturated thin films. The magnetic and optical properties of the AD thin films and PLiD nanoparticles are characterized using a vibrating sample magnetometer, optical absorption spectroscopy, and electron energy loss spectroscopy (EELS). Magnetic measurements demonstrate that Ag_0.5Ni_0.5 nanoparticles are ferromagnetic at room temperature when the nanoparticle diameters are >20 nm and superparamagnetic <20 nm. Optical measurements show that all nanoparticle size distributions possess a local surface plasmon resonance (LSPR) peak that red-shifts with increasing diameter. Following PLiD, a Janus nanoparticle morphology is observed in scanning transmission electron microscopy, and low-loss EELS reveals size-dependent Ag and Ni LSPR dipole modes, while higher order modes appear only in the Ag hemisphere. PLiD of Ag-Ni thin films is shown to be a viable technique to generate bimetallic nanoparticles with both magnetic and plasmonic functionality.