High spatial resolution mapping of surface plasmon resonance modes in single and aggregated gold nanoparticles assembled on DNA strands

Abstract

We present the mapping of the full plasmonic mode spectrum for single and aggregated gold nanoparticles linked through DNA strands to a silicon nitride substrate. A comprehensive analysis of the electron energy loss spectroscopy images maps was performed on nanoparticles standing alone, dimers, and clusters of nanoparticles. The experimental results were confirmed by numerical calculations using the Mie theory and Gans-Mie theory for solving Maxwell's equations. Both bright and dark surface plasmon modes have been unveiled.PACS78.67.Bf; 61.46.Df; 87.64.Ee

Angular-resolved electron energy loss spectroscopy on a split-ring resonator

“…Alternatively, an energy filtering TEM (EFTEM) with a broad electron beam can be used to directly acquire a complete EELS map by imaging only those electrons which experienced a specific energy loss. Both techniques have been applied to map the plasmonic modes of a variety of metallic nanostructures such as nanotriangles [5,6], nanorods and nanowires [7,8], dimer structures [9][10][11], bowtie antennas [12], nanodisks [13], split-ring resonators [14][15][16], and apertures in metal films [17].…”

Electron Energy Loss Spectroscopy of Hot Electron Transport between Gold Nanoantennas and Molybdenum Disulfide by Plasmon Excitation

“…Monolayer MoS 2 appears dark-gray in STEM mode relative to Au due to a low electron-scattering cross section inherent to its atomically thin nature. [18,21,23] Screening by PVP ligand encapsulating the Au particle may have red-shifted this mode relative to the bulk plasma energy of 2.45 eV. Bright and dark modes were distinguished elsewhere using maps of resonant EELS intensity, which indicate induced charge distributions at a given energy loss.…”

“…Probing a single nanoantenna using EELS in the latter avoided confounding effects from optical induction, such as direct electron-hole pair generation and diffraction-limited excitation across numerous nanoantennas or aggregates. [15,[18][19][20][21][22][23][24] Previous work in Au-MoS 2 hybrids used bright mode excitation of the Au nanoantennas to produce enhancements from which hot electron transfer contribution was inferred. The appearance, energy, and bandwidth of these modes depend on the impact point of the nanometer electron probe [16,17] and the geometry of the nanoantenna, e.g., sphere, disk, ellipse, or prism.…”

“…The appearance, energy, and bandwidth of these modes depend on the impact point of the nanometer electron probe [16,17] and the geometry of the nanoantenna, e.g., sphere, disk, ellipse, or prism. [15,[18][19][20][21][22][23][24] Previous work in Au-MoS 2 hybrids used bright mode excitation of the Au nanoantennas to produce enhancements from which hot electron transfer contribution was inferred. [7][8][9][10][11]25] Absorption of plasmon energy exceeding the Schottky barrier of nanoantenna-transition metal dichalcogenide (TMD) interfaces governs the potential for transport of plasmon-excited hot electrons into the TMD.…”

Mapping the plasmonic modes of silver nanoparticle aggregates

“…The third conditioning factor is the geometric shape of the cluster. In the same way that triangular NPs have plasmonic modes at lower energies than a sphere [5], a triangular or rhomboidal shaped group of NPs shows plasmonic modes at smaller energies than a spherical one [6]. In this work, silver NPs were created and were forced to cluster.…”