Effect of Intertip Coupling on the Plasmonic Behavior of Individual Multitipped Gold Nanoflower

Abstract

We report here, the first experimental realization on the selective excitation of two closely lying tips from the same spherical core of a multitipped gold nanoparticle with flower-like morphology. This gives strong multipeaked resonance in the near-infrared region of the far-field emission spectra showing a clear signature of tip to tip coupling. The cathodoluminescence (CL) technique in a scanning electron microscope (SEM) combined with finite-difference time-domain (FDTD) simulation has helped us to identify the coupled plasmon modes to be originated from the interaction between two closely spaced tips with a narrow angular separation. Our analysis further estimates a range of angular separation between the tips that triggers the onset of the intertip coupling.

Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields

“…The high spectral resolution in CL permits the observation of shoulders on the low-or high-energy side of the peaks, suggesting weak coupling between particular tip resonances. In good correspondence with the results of earlier experiments on Au nanostars 47,49,50 , we attribute the high-energy peak near 2.4 eV in CL to the plasmon resonance of the nanostar core. The side peaks in the core spectrum at 1.8 and 2.0 eV indicate coupling between the core and tip modes, as suggested in ref.…”

“…In this article, we present spatially-resolved EELS, CL, and PINEM measurements on a single Au nanostar with sharp conical tips. 42 As shown in previous works, [43][44][45][46][47][48][49][50][51][52] these tips sustain distinct plasmonic resonances that give rise to highly confined optical near fields at the tip apexes, providing an ideal geometry to correlate EELS, CL, and PINEM measurements at the nanometer length scale. Supported by theoretical considerations and numerical electromagnetic boundary-element method (BEM) calculations, we test the hypothesis that in the limit of an isolated tip mode spatial variations in the electron-near field coupling are fully determined by the modal electric field profile, irrespective of whether the excitations are driven by the electron itself (in EELS and CL) or a laser pulse (in PINEM).…”

“…In this article, we present spatially resolved EELS, CL, and PINEM measurements in the near field of a single chemically synthesized Au nanostar composed of an~50nm-diameter spherical core and sharp conical protrusions with a tip radius of curvature <3 nm 41 . As shown in previous works [42][43][44][45][46][47][48][49][50][51] , these tips sustain distinct plasmonic resonances in the VIS-NIR spectral range that give rise to highly confined optical near fields at the tip apexes, providing an ideal geometry to compare EELS, CL, and PINEM measurements at the nanometer length scale. Supported by theoretical considerations and numerical electromagnetic boundary-element method (BEM) calculations, we study the spectral and spatial dependence of the spontaneous electron energy-loss and photonemission probabilities probed by EELS and CL, respectively, and the stimulated electron-near-field coupling strength measured in PINEM.…”

Binary Surfactant–Mediated Tunable Nanotip Growth on Gold Nanoparticles and Applications in Photothermal Catalysis

“…This new peak appears because of the lightning-rod effect, in which the nanotip serves as an antenna. Coupling of the core and nanotip increases the effective dipole moment of the tip plasmons ( Maity et al, 2014 ; Kim and Ha, 2017 ). Hybridization of the core and tip increases the cross section for excitation of bonding nanostar plasmons compared with that of an individual nanosphere plasmon.…”

Gold nanoparticle labeling based ICP-MS detection/measurement of bacteria, and their quantitative photothermal destruction

“…One possible reason is that several narrow, nanoscale spikes in GNPOP were capable of focusing the field at their apexes, which could provide considerable enhancement of photothermal efficiency. 75 …”