Theoretical Study of Fluorescence Spectroscopy of Quantum Emitters Coupled with Plasmonic Dimers and Trimers

Abstract

We have developed a theory for the photoluminescence of dimer nanohybrids and trimer nanohybrids using the density matrix method. These nanohybrids are made from identical double metallic nanoshells embedded in an ensemble of quantum emitters. We consider that they are immersed in medical, biological, and chemical solutions. The dipole−dipole interaction between quantum emitters in the ensemble is calculated using the mean-field approximation. The effect of the dipole−dipole interaction has been included in the formulation of the photoluminescence. We have compared our theory with the experimental data of the ensemble of quantum emitters (ZnCdSeS-QDs) doped in chloroform and aqueous solutions. A good agreement between theory and experiment is found. We showed that the dipole−dipole interaction is stronger in the chloroform solution than that in the aqueous solution. Surface plasmon polariton resonances and electric fields are calculated for the metallic dimer and trimer by solving the Maxwell equations in the static wave approximation. The calculated surface plasmon polariton resonances agree with experimental data for an Au dimer and an Au trimer. We compare our theory with the photoluminescence experimental data of nanohybrids made from the ensemble of ZnCdSeS-QDs and the Au dimer and Au trimer. It is shown that the dipole−dipole interaction plays an important role in understanding the photoluminescence. We found that the intensity of the photoluminescence in the Au trimer nanohybrid is slightly higher than that in the Au dimer nanohybrid. This is because the surface plasmon polariton electric field emitted by the Au trimer is slightly larger than the electric field emitted by the Au dimer. We also found that two competing physical mechanisms, namely, the quenching and the enhancement, play important roles in these experiments. We showed that the quenching is due to the nonradiative decay rate, whereas the enhancement is due to the dipole−dipole interaction and surface plasmon polariton electric fields. These interesting findings may be useful in the fabrication of nanosensors for medical, biological, and chemical applications.

Insights on the Coupling of Plasmonic Nanoparticles from Near-Field Spectra Determined via Discrete Dipole Approximations

“…Although many studies have shown that such an approach is valid, one should be aware of possible quantum effects in NP coupling when particle sizes are small (less than 10 nm) or the gap distance between the NPs is in the subnanometer range . Additionally, interactions of molecular dyes or quantum dots with plasmonic NPs are fundamentally dictated by quantum electrodynamics, although the mean-field approach has been applied to describe the dipole–dipole interaction in these hybrid systems. , The near-field spectra obtained in the current study might provide additional insights to these hybrid systems.…”

Controllable Excitation of Surface Plasmon Polaritons in Graphene‐Based Semiconductor Quantum Dot Waveguides

“…Note that the distances between individual QDs in the system are chosen to be the same order of magnitude or larger than the characteristic SPP wavelength in the system. Considerable reduction of such a distance can lead to an increase in the role of near-field dipole-dipole interaction (DDI) between nanoparticles (NPs) [42][43][44] and changing the regime from plasmonic waveguide to non-radiative energy transmission by means of photonic bound states. [45] In our investigation, we use a semiclassical approach to define the graphene waveguide system's main parameters with an Ag 2 Se QD array that can lead to the excitation of graphene SPPs only in the local space between the gold stripes used to connect external electrical voltages.…”

Tailoring the Third-Order Nonlinear Optical Property of a Hybrid Semiconductor Quantum Dot–Metal Nanoparticle: From Saturable to Fano-Enhanced Absorption

“…Due to recent advancements in nanofabrication techniques, there has been growing interest in SQD–MNP hybrid nanostructures − for their potential novel optoelectronic applications ,− and exotic physical behavior, including plasmon–exciton electromagnetic coupling, − plasmon-assisted Rabi oscillations, as well as plasmon-modified energy transfer and resonances. ,,, A wide range of theoretical studies on nanostructures have been developed, based on classical, semiclassical, ,,− and full quantum mechanical approaches. ,− These studies have greatly motivated extensive exploration toward nonlinear optical fields, − such as second harmonic generation, , optical bistability, , four-wave mixing, Raman scattering, giant third-order nonlinear responses, and high-order harmonics . Recently, Singh et al developed density matrix method for nanohybrids and observed the anomalous quenching and enhancement in the photoluminescence (PL) spectrum of the CdSe/ZnS quantum dot embedded in the ensemble of Au MNP .…”

“…Recently, Singh et al developed density matrix method for nanohybrids and observed the anomalous quenching and enhancement in the photoluminescence (PL) spectrum of the CdSe/ZnS quantum dot embedded in the ensemble of Au MNP . They demonstrated fluorescence enhancement in dimer and trimer nanohybrids …”

“…47 They demonstrated fluorescence enhancement in dimer 48 and trimer nanohybrids. 34 Most of the previous studies on the SQD−MNP hybrid nanostructures [5][6][7]32,35,49 focused primarily on the total absorption responses of which the linear and all orders of nonlinear optical processes were included. However, it is not clear in these studies how much individual nonlinear orders contribute to the total responses.…”