Abstract
Probing plasmonic properties of surface deposited nanoparticles with high spatial resolution requires the use of a low absorption support. In this work, ultra-thin hexagonal boron nitride (h-BN) flakes are employed as substrates for scanning transmission electron microscopy. The thicknesses of only a few atomic layers, the flat surface, and the large bandgap provide a unique set of properties, which makes h-BN ideally suitable for high resolution plasmon spectroscopy by means of electron energy loss spectroscopy (EELS), especially for small nanoparticles. A facile fabrication process allows the production of h-BN substrates with a thickness of only a few atomic layers. The advantages of h-BN, especially for the low-loss energy region of EEL spectra, are shown in a direct comparison with a silicon nitride substrate. Furthermore, results of the investigation of localized surface plasmon resonances (LSPRs) of Ag and Ag–Au core–shell nanoparticles in the sub-20 nm size regime are presented, confirming the advantages of the fabricated substrate for LSPR mapping. The plasmonic nanoparticles were assembled utilizing the helium nanodroplet synthesis approach, which allows for a very soft deposition and the preservation of the integrity of the ultra-thin substrate. Moreover, it provides a completely solvent and surfactant free environment for the assembly of tailored nanoparticles.
Highlights
The advent of 2D materials is opening up exciting new prospects in a broad diversity of fields
These areas originate from the preparation process when layers of hexagonal boron nitride (h-BN) fold over each other; since they are locally contained, they do not pose a problem for the applied analytical methods
We successfully showed a way to use a very thin h-BN film for the fabrication of scanning transmission electron microscope (STEM) substrates, which are ideal for high resolution studies of nanosized metal particles by means of energy loss spectroscopy (EELS)
Summary
The advent of 2D materials is opening up exciting new prospects in a broad diversity of fields. Hexagonal boron nitride (h-BN) represents a interesting material, which has already been used for applications in optics,[1,2] catalysis,[3,4] and microelectronics.[5,6,7] Here, we demonstrate that ultra-thin h-BN can be utilized for localized surface plasmon (LSP) spectroscopy on the nanoscale by exploiting its electronic properties and the flat, two-dimensional structure.[8] We present results from the fabrication of h-BN substrates and their application for high resolution LSP spectroscopy, performed inside a scanning transmission electron microscope (STEM) by means of monochromated electron energy loss spectroscopy (EELS). A further unique feature of the helium droplet approach, providing interesting opportunities for future experiments, is the possibility to synthesize nanowires by adjusting the helium temperature and thereby forming larger droplets containing vortices.[26–28]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
