Systematic investigation on quad-metallic AgAuPdPt and tri-metallic AuPdPt NPs through the solid-state dewetting of quad-layer Ag/Au/Pd/Pt thin films on c-plane sapphire

RESEARCH ARTICLE Systematic investigation on quad-metallic AgAuPdPt and tri-metallic AuPdPt NPs through the solid-state dewetting of quadlayer Ag/Au/Pd/Pt thin films on c-plane sapphire Mao Sui1,2*, Sundar Kunwar2, Puran Pandey2, Sanchaya Pandit2, Jihoon Lee ID2* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Institute of Hybrid Materials, College of Materials Science and Engineering, Qingdao University, Qingdao, P. R. China, 2 Department of Electronic Engineering, College of Electronics and Information, Kwangwoon University, Nowon-gu Seoul, South Korea * (MS); (JL) Abstract OPEN ACCESS Citation: Sui M, Kunwar S, Pandey P, Pandit S, Lee J (2019) Systematic investigation on quad-metallic AgAuPdPt and tri-metallic AuPdPt NPs through the solid-state dewetting of quad-layer Ag/Au/Pd/Pt thin films on c-plane sapphire. PLoS ONE 14(10): e0224208. https://doi.org/10.1371/journal. pone.0224208 Editor: Yogendra Kumar Mishra, Institute of Materials Science, GERMANY Received: August 9, 2019 Accepted: October 8, 2019 Published: October 21, 2019 Copyright: © 2019 Sui et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: Financial support from the National Research Foundation of Korea (no. NRF2019R1A2C4069438 and NRF2018R1A6A1A03025242) and in part by the research grant of Kwangwoon University in 2019 (JL) is gratefully acknowledged. Multi-metallic alloy nanoparticles (MNPs) can offer valuable opportunities to meet the various demands of applications. MNPs consist of various noble metallic elements can combine diverse electronic, optical and catalytic properties in a single NP configuration, thus taking the advantage of each element. In this paper, the fabrication of tri- and quad- metallic alloy NPs with noble elements (Ag, Au, Pd and Pt) and the corresponding localized surface plasmon resonance (LPSR) properties are systematically demonstrated. Tri- and quad-metallic alloy NPs come in various size and configurations by the solid-state dewetting of Ag/Au/Pd/ Pt quad-layers on sapphire (0001). Tri-metallic AuPdPt NPs are demonstrated by the systematic control of growth temperature along with the significant Ag atom sublimation. Strongly enhanced and tunable LPSR is exerted in the UV-VIS regions depending upon the size, configuration, spacing and elemental composition of the MNPs. The size dependent LSPR response of MNPs is discussed based on the absorption and scattering along with the excitation of dipolar, quadrupolar, high order and multipolar resonance modes. The MNPs exhibit much stronger and dynamic LSPR bands as compared with the monometallic Pt and Pd NPs with the comparable size and configurations. Introduction The localized surface plasmon resonance (LSPR) offered by the noble metallic NPs has been an intensive area of research and thus utilized in various fields to increase absorption and scattering of selective wavelength, which can effectively enhance the energy conversion efficiency in solar cells, light scattering in LEDs, photocatalytic activity in fuel cells and sensitivity in the biological sensors [1–13]. Multi-metallic alloy nanoparticles (MNPs) are important materials systems in various fields due to the feasibility of integrating beneficial electronic, optical and PLOS ONE | https://doi.org/10.1371/journal.pone.0224208 October 21, 2019 1 / 18 Systematic investigation on quad-metallic AgAuPdPt and tri-metallic AuPdPt NPs Competing interests: The authors have declared that no competing interests exist. catalytic properties of each element [1,2,6,7]. The properties and functionalities of MNPs are largely dependent on the elemental composition along with the morphology [8–12]. As an example, the tri-metallic PdAgCd NPs, in contrast to the mono-metallic Pd and bi-metallic PdAg NPs, demonstrated a significantly enhanced hydrogen storage efficiency due to the synergetic effect of alloy elements [14]. Among various noble metallic elements, the Au and Ag are widely adapted as superior plasmonic materials due to their strong generation of electromagnetic fields at the resonance frequency. Meanwhile, the Pd and Pt NPs can offer superior catalytic activity and stability and thus are promising cathode materials in the fuel cells [15,16]. The combination of these elements can deliver interesting opportunities, i.e. a superior photocatalytic system for the fuel cells, by taking the advantage of each element. At the same time, the solid-state dewetting (SSD) can offer an efficient route to fabricate the MNPs based on the temperature-induced surface diffusion and intermixing process below the melting point of elements [17–20]. Various mono- and bi-metallic NPs have been successfully applied in numerous applications based on the SSD, in which the initial layer thickness, growth conditions and substrate properties can largely affect the resulting crystal orientation, size and shape of NPs [21]. Meanwhile, the MNPs have been generally synthesized in the form of colloidal solution by the chemical approaches due to the relative handy synthesis environment, which can provide precise control on size, shape and uniformity [22]. However, the device performance with the chemically synthesized NPs has been somewhat hindered by the issues of impurity, durability and weak binding to substrate. The SSD approach can provide highly stable, pure and large scale-fabrication of various monometallic and multi-metallic alloy NPs [23]. The detailed study on the fabrication and characterizations of MNPs by the SSD can allow one to control the composition and morphology of NPs for the target applications, which however has not been explored for the high order MNPs up to now. In this paper, a systematic study on the fabrication and LSPR property of MNPs is performed by means of the solid-state dewetting (SSD) of Ag/Au/Pd/Pt quad-metallic layers on sapphire (0001). A wide range of size, density and configuration of quad-metallic AgAuPdPt and tri-metallic AuPdPt NPs have been successfully demonstrated depending on the control of initial quad-layer thickness and growth conditions, which exhibits strong and dynamic LSPR bands in the UV and VIS wavelengths. The fabrication and evolution of various MNPs are discussed based on the temperature-dependent atomic inter-diffusion, alloy phase, energy minimization and sublimation of Ag atoms along with the systematic analyses. The LSPR bands demonstrate the dynamic variations in the intensity, position and bandwidth based on the surface morphology and composition of MNPs. Materials and methods In this work, the double-side polished 430 μm-thick c-plane sapphire with ± 0.1˚ off-axis (iNexus, South Korea) was chosen as a substrate. Firstly (...truncated)