Improved Morphological and Localized Surface Plasmon Resonance (LSPR) Properties of Fully Alloyed Bimetallic AgPt and Monometallic Pt NPs Via the One-Step Solid-State Dewetting (SSD) of the Ag/Pt Bilayers

Multi-metallic alloy nanoparticles (NPs) can offer a promising route for the integration of multi-functional elements by the adaptation of advantageous individual NP properties and thus can exhibit the multi-functional dynamic properties arisen from the electronic heterogeneity as well as configurational diversity. The integration of Pt-based metallic alloy NPs are imperative in the catalytic, sensing, and energy applications; however, it usually suffers from the difficulty in the fabrication of morphologically well-structured and elementally well-alloyed NPs, which yields poor plasmonic responses. In this work, the improved morphological and localized surface plasmon resonance (LSPR) properties of fully alloyed bimetallic AgPt and monometallic Pt NPs are demonstrated on sapphire (0001) via the one-step solid-state dewetting (SSD) of the Ag/Pt bilayers. In a sharp contrast to the previous studies of pure Pt NPs, the surface morphology of the resulting AgPt and Pt NPs in this work are significantly improved such that they possess larger size, increased interparticle gaps, and improved uniformity. The intermixing of Ag and Pt atoms, AgPt alloy formation, and concurrent sublimation of Ag atoms plays the major roles in the fabrication of bimetallic AgPt and monometallic Pt NPs along with the enhanced global diffusion and energy minimization of NP system. The fabricated AgPt and Pt NPs show much-enhanced LSPR responses as compared to the pure Pt NPs in the previous studies, and the excitation of dipolar, quadrupolar, multipolar and higher-order resonance modes is realized depending upon the size, configuration, and elemental compositions. The LSPR peaks demonstrate drastic alteration along with the evolution of AgPt and Pt NPs, i.e., the resonance peaks are shifted and enhanced by the variation of size and Ag content.