Symmetric and asymmetric epitaxial growth of metals (Ag, Pd, and Pt) onto Au nanotriangles: effects of reductants and plasmonic properties.

Xiaobin Xie,Marijn A Van Huis,Alfons Van Blaaderen

doi:10.1039/d0nr06789j

Xiaobin Xie, Marijn A Van Huis + Show 1 more

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https://doi.org/10.1039/d0nr06789j

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Abstract

The surface plasmon resonance of noble metals can be tuned by morphology and composition, offering interesting opportunities for applications in biomedicine, optoelectronics, photocatalysis, photovoltaics, and sensing. Here, we present the results of the symmetrical and asymmetrical overgrowth of metals (Ag, Pd, and Pt) onto triangular Au nanoplates using l-ascorbic acid (AA) and/or salicylic acid (SA) as reductants. By varying the reaction conditions, various types of Au nanotriangle-metal (Au NT-M) hetero-nanostructures were easily prepared. The plasmonic properties of as-synthesized nanoparticles were investigated by a combination of optical absorbance measurements and Finite-Difference Time-Domain (FDTD) simulations. We show that specific use of these reductants enables controlled growth of different metals on Au NTs, yielding different morphologies and allowing manipulation and tuning of the plasmonic properties of bimetallic Au NT-M (Ag, Pd, and Pt) structures.

Highlights

We systematically investigate the roles that ascorbic acid (AA) and salicylic acid (SA) play in the synthesis of Au nanotriangle (Au NT) based binary noble metal nanoparticles (BNMNPs) under similar reaction conditions
SA and AA were used as a reductant for growth of metals (Ag, Pd, and Pt) onto Au NTs
Due to the lower reactivity in comparison to AA, using SA allowed less control over the morphology of Au–Ag NPs but this reductant was found to be effective for manipulating Pd and Pt structures growing onto Au NTs

Summary

Introduction

Gold based binary noble metal nanoparticles (BNMNPs) have attracted great interest due to their promising applications in various fields, including electronic devices,[1] catalysis,[2,3] energy conversion,[4,5] biological medicine,[6,7] sensing and detection.[8,9,10,11] In the course of decades, a wide variety of BNMNP structures, like core–shell, alloyed, Janus, yolk–shell and other complex morphologies have been successfully synthesized.[8,12,13,14,15,16] nano-structures based on platelike Au nanoparticles are increasingly drawing attention, because of their special morphology and highly tunable properties.[17]. The FDTD simulations on the Au NT-Ag NPs with an asymmetrical Ag shell with thicknesses varying from 1 nm to 40 nm (Fig. 3b), show good agreement in that a thicker Ag shell leads to a larger blue shift of the main LSPR band.

Results

Conclusion