Nanoengineering of conductively coupled metallic nanoparticles towards selective resonance modes within the near-infrared regime

Abstract

In this work, the mode transition effect of different plasmonic resonances in linked dimers by a conductive junction is numerically investigated.Without the junction, the dimer supports a single dipolar bonding plasmon mode, while two new resonance modes, a screened bonding dipolar mode and a low energy charge transfer plasmon mode, emerge when two nanoparticles are linked via a bridge. Such effect is proved to be unrelated to the shape of the nanoparticles, whether sphere, core-shell or nanoegg. However, it was found that the status of each specific resonance mode is profoundly influenced by the shape of nanoparticles. Furthermore, a detailed discussion of mechanisms of controlling plasmon modes, specially charge transfer mode, and tuning their corresponding spectra in bridged nanoparticles as functions of nanoparticle parameters and junction conductance is presented. These results show that the optical response of the dimer is highly sensitive to changes in the inter-particle gap. While the capacitive dimer provides a strong hotstop, the conductive dimer leads to highly controllable low energy plasmon mode at the mid-infrared region appropriate for novel applications. These findings may serve as an important guide for optical properties of linked nanoparticles as well as understanding the transition between the capacitive and conductive coupling.

Single-Step Plasmonic Dimer Printing by Gold Nanorod Splitting with Light

“…For gold particles in (electrical) contact, the BDP mode is screened (blue-shifted and lowered in intensity), becoming a higher order charge transfer plasmon (CTP′) (or screened BDP mode) at wavelengths <590 nm . Furthermore, a CTP mode would appear in the IR wavelength region. − The visible part of the dimer scattering spectrum shown in Figure b (lower panel) could be reproduced classically by assuming a 0.4 nm gap. A separation of ≥0.4 nm corresponds to the noncontact regime for gold particles of comparable size, where classical electrodynamic modeling resembles quantum mechanical results. , However, one must consider that determining exact gap sizes based on calculations is challenging because the particles may not form perfect spheres.…”

Photothermal and Photoacoustic Response of a VO2@Au Nanoshell Irradiated by a Nanosecond Laser Pulse

“…To study plasmonic modes, the surface charge density for two wavelengths is calculated using the following equation ρ = ε 0 × ( n · E ) n ω 2 = ε 0 ( n x × E x + n y × E y + n z × E z ) n ω 2 where n x , n y , and n z are normal vectors .…”

Hybrid Plasmonic Modes for Enhanced Refractive Index Sensing

“…[64] Nevertheless, the CTP modes have striking spectral features including ultratunable mid-infrared spectrum that can be easily tuned by controlling the conductance of bridging nanowire and geometries of linked nanoparticles (see Figure 5B). [17,65] Thus, understanding the direct transfer of charges in conductively bridged plasmonic nanodimers is essential for developing plasmon-based nanodevices including nanomotors, sensors, and optoelectronic devices. [10,20,66] In particular, given its ultratunable and narrow spectral signatures, the CTP resonance has great potential for bulk, surface, gas and molecular sensing.…”