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Optical Bistability in a Quantum Dot–Metallic Nanoshell–Cell Membrane Hybrid System: Applications for High-Performance Biosensing

Xiao Ma, Hongmei Gong, Yuxiang Peng, Linwen Long, Jianbo LI

Published Jan 14, 2026• 0 citations
Publisher

Abstract

We investigate optical bistability (OB) in a hybrid system comprising a semiconductor quantum dot (SQD), a metallic nanoshell (MNS), and a cell membrane within the framework of the multipole approximation. Bistability phase diagrams plotted in the system’s parameter subspaces demonstrate that, in the weak exciton–phonon coupling regime, dynamic switching of bistable states among no-channel, single-channel, and dual-channel configurations can be achieved via precise modulation of the MNS’s dielectric shell thickness. Especially, a critical sensing threshold is identified: the absorption peak disappears and a bistable effect emerges when only 1.82% of normal cells undergo malignant transformation. Furthermore, the bistable region exhibits a gradual broadening trend with an increasing proportion of cancerous cells, yielding a quantitative and ultra-sensitive readout that underpins a highly accurate strategy for early cancer diagnosis. These findings not only deepen our fundamental understanding of bistability regulation in hybrid quantum-plasmonic systems interfaced with biological materials but also offer valuable insights for the development of next-generation optical switches and biomedical sensing platforms.

DOI
10.3390/coatings16010109

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We investigate optical bistability (OB) in a hybrid system comprising a semiconductor quantum dot (SQD), a metallic nanoshell (MNS), and a cell membrane within the framework of the multipole approximation. Bistability phase diagrams plotted in the system’s parameter subspaces demonstrate that, in the weak exciton–phonon coupling regime, dynamic switching of bistable states among no-channel, single-channel, and dual-channel configurations can be achieved via precise modulation of the MNS’s dielectric shell thickness. Especially, a critical sensing threshold is identified: the absorption peak disappears and a bistable effect emerges when only 1.82% of normal cells undergo malignant transformation. Furthermore, the bistable region exhibits a gradual broadening trend with an increasing proportion of cancerous cells, yielding a quantitative and ultra-sensitive readout that underpins a highly accurate strategy for early cancer diagnosis. These findings not only deepen our fundamental understanding of bistability regulation in hybrid quantum-plasmonic systems interfaced with biological materials but also offer valuable insights for the development of next-generation optical switches and biomedical sensing platforms.
We develop a theory to investigate Kerr nonlinearity in a hybrid nanosystem integrating a semiconductor quantum dot (SQD), a metallic nanoshell (MNS) consisting of a metallic inner core and a dielectric outer shell, and a cell membrane. Beyond the dipole approximation, an analytical expression for the Kerr coefficient is derived, with key findings as follows: (1) The multipole effect enables a significant enhancement of the Kerr coefficient compared to the dipole approximation scenario, whereas increasing the spacing between the SQD and the MNS leads to substantial suppression of this coefficient; (2) The Kerr spectrum can be switched from a two-peaked to a three-peaked structure solely by tuning the exciton-phonon coupling strength; (3) The heights, positions, and full widths at half maximum (FWHM) of the two sideband peaks in the Kerr spectrum exhibit high sensitivity to both pumping intensity and dielectric shell thickness. Importantly, we demonstrate the feasibility of detecting the initiation of normal cell carcinogenesis by monitoring the heights, locations, and frequency shifts of these two sideband peaks. The proposed scheme exhibits promising applications in quantum information networks and biosensing.
We theoretically explore the conditions for generating optical bistability (OB) in a heterodimer comprised of a semiconductor quantum dot (SQD) and a metallic nanoshell (MNS). The MNS is made of a metallic nanosphere as a core and a dielectric material as a shell. For the specific hybrid system considered, the bistable effect appears only if the frequency of the pump field is equal to (or slightly less than) the exciton frequency for a proper shell thickness. Bistability phase diagrams, when plotted, show that the dipole-induced bistable region can be greatly broadened by changing the shell thickness of the MNS in a strong exciton-plasmon coupling regime. In particular, we demonstrate that the multipole polarization not only narrows the bistable zone but also enlarges the corresponding thresholds for a given intermediate scaled pumping intensity. On the other hand, when the SQD couples strongly with the MNS, the multipole polarization can also significantly broaden the bistable region and induce a great suppression of the FWM (four-wave mixing) signal for a fixed shell thickness. These interesting findings offer a fresh understanding of the bistability conditions in an SQD/MNS heterodimer, and may be useful in the fabrication of high-performance and low-threshold optical bistable nanodevices.
We propose a scheme for achieving ultrastrong slow light in a hybrid nanosystem consisting of a metallic nanoshell (MNS), a semiconductor quantum dot (SQD), and a cell membrane. The MNS is composed of a metallic inner core and a dielectric outer shell. We derive the analytical expressions for the linear susceptibility and group velocity index under the multipole approximation. It is shown that the amplitudes and positions of the absorption peaks, as well as the group velocity index, depend strongly on the exciton-pump detuning, MNS-SQD distance, dielectric shell thickness, and exciton-phonon coupling strength. Especially, the amplitude of the characteristic absorption peak associated with the cell membrane can be enhanced by over 2200 times by only tuning the exciton-phonon coupling strength within an extremely narrow range. In an intermediate exciton-phonon coupling regime, the group velocity index rises abruptly from 86.13 to 2.87 × 10 11 with the pump intensity varied from 10 GHz 2 to 22.41 GHz 2 . Furthermore, we demonstrate that the precise monitoring of the cellular carcinogenesis degree can be realized by detecting the fast-to-slow light switching point, with the corresponding proportion of cancerous cells as low as 1.71%. Our findings exhibit broad application prospects in optical signal amplifiers and biosensors.
We theoretically study the optical bistability assisted by multipole polarizations in a semiconductor quantum dot (SQD)/metal nanoparticle (MNP) hybrid molecule. We map out bistability phase diagrams within the parameter subspace spanned by (the pumping intensity Ipu, interparticle distance, d) under dipole and multipole approximations. It is shown that the Ipu-correlated bistable region will be broadened greatly in the strong exciton–plasmon coupling regime, and the corresponding lower (upper) bistable threshold is enlarged significantly due to multipole polarization (N = 10) in comparison to that in the dipole approximation (N = 1). However, under the same conditions, the d-correlated bistable region is shrunk at high pump intensities. Our contribution not only offers a better understanding of exciton–plasmon coupling systems but also expands the application of SQD/MNP hybrid molecules in the field of optical bistable nanodevices.
We study the response of a semiconductor quantum dot-metal nanoparticle system to an external field E0 cos (ωt). The borders between Fano, double peaks, weak transition, strong transition, and bistability regions of the phase diagram move considerably as one regards the multipole effects. The exciton-induced transparency is an artifact of the dipole approximation. The absorption of the nanoparticle, the population inversion of the quantum dot, the upper and lower limits of intensity where bistability occurs, the characteristic time to reach the steady state, and other features of the hybrid system change due to the multipole effects. The phase diagrams corresponding to the fields parallel and perpendicular to the axis of system are quite distinguishable. Thus, both the intensity and the polarization of the incident field can be used to control the system. In particular, the incident polarization can be used to switch on and switch off the bistable behavior. For applications such as miniaturized bistable devices and nanosensors sensitive to variations of the dielectric constant of the surrounding medium, multipole effects must be considered.
Optical response of a complex nanodimer comprising a semiconductor quantum dot via Coulomb interaction to a metal nanorod is analyzed theoretically. Optical bistability (OB) behavior of a coherently coupled exciton-plasmon (plexcitonic) hybrid system under a laser field is investigated. The bistable exciton population in a hybrid metal–semiconductor nanodimer response is shown, and it could be pointed out that OB behavior is strongly influenced by various parameters such as size of metal nanoparticle, interparticle distance as well as intensity of probe laser field. We show that OB can be observed for a plexcitonic system and depends strongly on the type of the metals which are good candidates for plasmonic applications. The numerical calculations show the gold nanorod exhibits significant optical bistability. The result promises various applications in the field of all-optical information processing at the nanoscale, the most basic of them being the optical switching, optical memory, optical transistor and optical logic.