Plasmonics最新文献

In this study, a theoretical model for a surface plasmon resonance (SPR) sensor was developed using the transfer matrix method (TMM) to simulate and analyze reflectivity as a function of the angle of incidence in a multilayer system. This system consists of a gold layer with a fixed thickness, followed by a layer of SnSe with variable thicknesses within a defined range, and then a thin layer of MoS₂, using water as a biorecognition medium. The study focused on examining the effects of changes in the thickness of the SnSe layer and the wavelength within the range (690 to 1000 nm), as well as the effect of variations in the refractive index of the sensing medium due to contamination. Through numerical simulation, the properties of plasmonic resonance such as the reflection angle, SPR dip width, and SPR dip length were evaluated, along with sensor sensitivity. The sensor response was also analyzed when the refractive index of the sensitive medium changed slightly, reflecting the presence of contaminants, with the aim of studying the sensor’s ability to distinguish between different conditions. The addition of the SnSe layer has proven effective in improving the coupling of the evanescent wave with the sensitive medium, significantly enhancing the sensitivity of the device. A sensitivity of approximately 200°/RIU was achieved at wavelengths of 800 nm and 900 nm with thicknesses of 10 and 60 nm. These results reflect the effectiveness of the proposed design for use in high-precision sensing applications.

This works presents a Tamm plasmon polariton (TPP)-based sensor for the identification of the degree of adulteration in petrol. The proposed structure is designed by integrating black phosphorous (BP) with 1D photonic crystal (PhC), where the PhC is realized with an alternate stacking of TiO₂ and SiO₂. A defect layer is sandwiched between BP and PhC, which is filled with various concentrations of adulterated petrol for sensing purpose. The reflectance spectrum of the sensor is investigated by employing well-known transfer matrix method. The sensing principle is based on the analysis of the shift in the TPP mode wavelength with respect to different percentages of adulteration. The geometrical parameters like thickness of different layers and period of the PhC are suitably optimized to attain maximum performance. The significance of BP is studied and compared with the conventional metal for the generation of TPP mode. Furthermore, the electric field distribution is investigated in the structure. Simulation outcomes show a maximum sensitivity of 4900 nm/RIU, maximum quality factor of 151.42, and minimum detection limit of (1.27times10^{-4}) RIU are achieved with the designed sensor, which proves its potential applications in petrochemical industry.

In the present work, we theoretically investigate the optical bistability in a dimer consisting of two graphene-coated dielectric nanoparticles with a single molecule placed in the gap region. Assuming this system is exposed to an electromagnetic field, by solving Laplace’s equation in the quasi-static approximation, we obtain the local electric fields in different regions of the proposed system. The results show that the presence of molecule in the gap of dimer significantly affects the bistable behavior and leads to changes in the bistability thresholds and hysteresis loop compared to the dimer without the molecule. Furthermore, we explore the effects of nanoparticle asymmetry and the molecule dipole moment on the bistable response. We found that by increasing the degree of asymmetry, where the two nanoparticles differ in size, the bistability region will be increased and broadened. However, these findings may find practical potential applications in nanophotonic and optoelectronic devices.

This research investigates the structural and optical properties of carbon quantum dots (CQDs) for the sensitive detection of ascorbic acid (AA), an essential biomolecule used widely in health and industry. Accurate AA detection is critical for pharmaceutical and food safety applications, and this study demonstrates the use of a prism-based surface plasmon resonance (SPR) sensor with a CQD thin film for label-free and real-time monitoring. CQDs were deposited onto a gold (Au) thin film, and their structural properties were characterized through Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). FTIR analysis confirmed the presence of C–H, C≡C, C–N, and C–O bonds on the Au/CQDs surface, while AFM characterization revealed that the CQDs formed a uniformly dispersed, spiky surface evenly distributed across the gold layer. The optical properties of the Au/CQDs thin film were studied using ultraviolet–visible (UV–Vis) spectroscopy, showing an absorption peak of approximately 4.44 a.u. in the range of 260–270 nm, with an optical bandgap of 4.072 eV. When integrated into the SPR sensor, the Au/CQDs thin film demonstrated high sensitivity for AA detection, achieving a detection limit as low as 0.001 µM. Further characterization was conducted to explore the interaction between the Au/CQD thin film and AA, highlighting the film’s potential for use in sensitive biochemical sensing applications.

This work presents a mechanism for controlling stimulus speed within the plasmon-polariton model of fast stimulus kinetics during saltatory conduction in myelinated axons. Myelin thickness plays a crucial role, but the related mechanism differs from that in the conventional cable model. The thickness of the myelin sheath precisely tunes the plasmon-polariton frequency and the associated signal velocity. This frequency is limited by the timescale of triggering the opening of sodium channels at the nodes of Ranvier, allowing for the initiation of the Huxley-Hodgkin cycles. Synchronization of the plasmon-polariton stimulus frequency with these cycles at consecutive nodes of Ranvier ensures the balance of Ohmic losses and enables arbitrarily long-range axon firing. The myelin layer thickness assessed by the model, considering the molecular structure of sodium channels, is consistent with observations. This model of plasmon-polariton stimulus control in myelinated axons completes the theory of saltatory conduction presented in Ionic Plasmon-Polaritons in Neural Signaling I: Structure and Dynamics of Plasmon-Polaritons in Myelinated Axons, Plasmonics 20, 4195-4220 (2025), https://doi.org/10.1007/s11468-024-02694-7.

Clostridium tetani produce a potent neuro toxoid as tetanus toxoid, which elicits spastic paralysis in humans and warm-blooded animals. Tetanus recognition is crucial; however, existing diagnostic methods have notable limitations. Recently, the localized surface plasmon resonance (LSPR) nano-bio-probe has been established as a promising technique for detecting Clostridium tetani toxoid. The designed nanobioprobe utilizes covalent conjugation between monoclonal anti-tetanus IgG antibodies and gold nanoparticles (GNPs). The dynamic light scattering (DLS) technique was employed to verify successful conjugation. Subsequently, the sensitivity of the LSPR was assessed as a function of tetanus toxoid concentration using a colorimetric assay. The results demonstrated that the LSPR band of functionalized GNPs exhibited a redshift from 530 to 563 nm in the presence of 1 ng of tetanus toxoid, outperforming the ELISA method. This study presents a rapid, sensitive, and selective approach for tetanus toxoid detection in clinical samples.

This study presents a novel terahertz metasurface biosensor incorporating graphene-MXene hybrid materials for enhanced salinity detection across environmental and industrial applications. The sensor features a multilayered architecture with three copper-coated rectangular resonators, concentric MXene-coated circular ring resonators, and a graphene-integrated circular base resonator on a silicon dioxide substrate. Numerical simulations using COMSOL Multiphysics demonstrated tunable electromagnetic response through graphene chemical potential modulation (0.1–0.9 eV) and maintained stable performance across incident angles up to 60°. The optimized sensor achieved a sensitivity of 286 GHz/RIU with a figure of merit of 3.247 RIU⁻¹, quality factor of 4.398, and detection limit of 0.022 RIU across a refractive index range of 1.3325–1.3505. Experimental validation showed strong correlation (R² = 0.80) between theoretical and measured absorption values. The proposed biosensor addresses critical limitations of conventional conductivity-based sensors, offering superior performance in high-salinity and turbid environments while providing real-time monitoring capabilities essential for oceanography, aquaculture, agriculture, and desalination applications.

A highly sensitive D-type photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) is proposed for the detection of cancer cells through refractive index (RI) monitoring. The sensor features a semicircular groove on the polished surface, coated with dual layers of gold (Au) and titanium dioxide (TiO₂) to enhance plasmonic coupling. Finite element method (FEM) analysis shows that the sensor has a refractive index range, maximum wavelength sensitivity, and resolution of 1.355–1.395, 54,000 nm/RIU, and 1.85 × 10⁻⁶ RIU, respectively, boding well for the early screening of cancer cells with a sensitivity in the range of 2500–24,285 nm/RIU. The compact sensor comprising a standard single-mode fiber with an outer diameter of 125 μm can be produced easily and has large application prospects in fields such as biomedical diagnosis, disease screening, and environmental detection.

The present study designed a new surface plasmon resonance (SPR) sensor based on a BaF₂ prism, silver (Ag), silicon (Si), and tantalum diselenide (TaSe₂) 2D material structure for the detection of basal cells. The angular interrogation method allows us to evaluate the performance exponentially at 633 nm. The proposed sensor demonstrates improved sensitivity and accuracy and detects the basal cell uses. The sensor proposed has a maximum sensitivity of 337.47°/RIU, a detection accuracy (DA) of 0.254/°, and a figure of merit (FoM) of 85.87/RIU. The research indicates that the integration of Si and TaSe₂ layers with traditional plasmonic metals can enhance sensitivity and provide a platform for further environmental monitoring and medical diagnostics.