Plasmonics最新文献

The quantification of dopamine, a critical catecholamine neurotransmitter, remains a significant challenge in neurological research and clinical diagnostics due to its low physiological concentrations and interference from structurally similar compounds. This study presents a simple metasurface sensor employing graphene-enhanced surface plasmon resonance for ultra-sensitive dopamine detection. Finite element method simulations using COMSOL Multiphysics 6.2 demonstrate exceptional performance with a maximum sensitivity of 500 GHzRIU⁻¹ at 0.805 THz, achieving a figure of merit of 2.110 and quality factor ranging from 3.376 to 3.435. The sensor exhibits tunable response through graphene chemical potential modulation (0.1–0.9 eV), with transmittance varying from 81.6% to 16.4%. Angular stability analysis reveals consistent performance across incidence angles from 0° to 80°. Machine learning integration using XGBoost regression achieves 92–100% prediction accuracy, enabling real-time performance optimization. The proposed sensor surpasses existing designs in sensitivity while maintaining broad refractive index detection range,positioning it as a promising platform for advanced neurochemical sensing applications in Parkinson's disease, schizophrenia, and substance abuse disorder diagnostics.

This theoretical and numerical investigation explores the enhancement and preservation of quantum discord in quantum systems coupled through V-shaped plasmonic waveguides (V-PW) using advanced quantum feedback control techniques. We demonstrate that properly engineered quantum feedback can significantly improve quantum discord preservation, particularly in Werner states where we observe enhancements from zero to 0.38 under optimal conditions. The mechanism involves a sophisticated confinement of the quantum state within protected subspaces that are resilient against environmental decoherence. Through detailed theoretical modeling and extensive numerical simulations, we identified the key parameters governing this enhancement process, including waveguide geometry, emitter positioning, and feedback timing. Our results reveal three distinct quantum discord decay temporal regimes and establish optimal operating conditions for maximal quantum correlation preservation. The findings provide fundamental insights into quantum correlation dynamics in nanophotonic systems and practical guidelines for experimental implementations in quantum information processing applications, with particular relevance to room-temperature quantum technologies.

This study presents a detailed investigation into the dispersion and confinement characteristics of surface plasmon polaritons (SPPs) in a symmetric waveguide architecture composed of nanocomposite–metal–nanocomposite (NMC–M–NMC) layers. The nanocomposite claddings incorporate metallic nanoparticles, enabling the simultaneous excitation of propagating surface plasmon modes and localized plasmon resonances. This coupling mechanism leads to superior field confinement and an extended modal wavevector range compared to conventional metal–insulator–metal (MIM) waveguides. The resulting structure supports both long-range SPP (LRSP) and short-range SPP (SRSP) modes, each exhibiting distinct advantages: LRSP modes offer reduced propagation losses and longer transmission distances, while SRSP modes exhibit tight spatial confinement around the metallic core. A key feature of the proposed system is its tunability, achieved by varying the nanoparticle characteristics—such as radius, volume fraction, and interparticle spacing—as well as the thickness of the central metal layer. This flexibility allows dynamic control over the effective wavelength and intensity distribution of the plasmonic modes, making the structure highly adaptable to a wide range of optical design requirements. To further elucidate the material influence on SPP behavior, comparative simulations are performed using two representative nanocomposite systems: silver–silica and gold–alumina. These comparisons reveal material-specific differences in mode dispersion and confinement, thereby providing valuable guidance for material selection in plasmonic device engineering. The demonstrated ability to manipulate SPP propagation and confinement through structural and material parameters underscores the potential of the NMC–M–NMC configuration in advanced photonic applications. In particular, this platform shows strong promise for integration into nanophotonic circuits, plasmonic sensors, optical modulators, and subwavelength light guiding components within next-generation optoelectronic systems.

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This study examined the optimization of the solution viscosity and spin-coating time to produce thin and uniform rGO layers for surface plasmon resonance (SPR) sensor applications. The viscosity of the rGO solution was controlled by varying the concentration of ascorbic acid as a reducing agent in the rGO synthesis process. Then, characterization was performed using FESEM-EDX, TEM, and thickness and roughness measurements using a topography measurement system (TMS). The characterization results demonstrated that increasing the solution viscosity was directly proportional to the layer thickness, roughness, and the percentage of carbon elements, as determined by EDX mapping. The SEM and TEM analyses revealed a surface morphology that resembled wrinkled paper structures, which overlapped and folded. The SAED pattern indicated the presence of crystallinity relating to the (002), (100), and (110) crystal planes. In addition, as the spin-coating time increased, the thickness and roughness of the layer decreased; however, the thickness-to-roughness ratio increased. SPR sensor testing with the rGO layer was also conducted using ethanol solution analytes with concentrations ranging from 0 to 20%. The results demonstrated that the SPR sensor with the rGO layer exhibited a sensitivity of 2481.42 nm/RIU and a linearity of R² = 0.96.

In this study, a D-shaped photonic crystal fiber (PCF) sensor with surface plasmon resonance (SPR) was designed with Ge-doped Si as the fiber core. The surface plasmon wave was excited by gold plating on the D-shaped surface. Numerical simulations by the finite element method (FEM) show that this sensor can realize a wide detection range of refractive index (RI) measurement from 1.330 to 1.445. The maximum wavelength sensitivity (WS) is 45,600 nm/RIU, and the maximum accuracy is 2.19 × 10⁻⁶ RIU. Compared with the sensor with a pure SiO₂ fiber core, the maximum WS is increased by about 2.87 times, and the average WS is increased by 20.6%. The proposed sensor is characterized by a simple structure, high sensitivity, and a large detection range, which has great potential in cell activity monitoring, food additives, and residue detection.

Employing surface plasmon resonance (SPR) in a specially designed dual-core photonic crystal fiber (PCF) with double-sided polishing, this study demonstrates a biosensor with superior sensitivity for Bacillus cereus identification. The sensor uses silica as a background material, and the structure is optimized by COMSOL Multiphysics software. Under Y-pol, the refractive index (RI) detection ranges were determined as n_a = 1.31–1.40 for odd mode and n_a = 1.31–1.39 for even mode. The maximum wavelength sensitivity (WS) reached 30,600 nm/RIU for even mode and 23,800 nm/RIU for odd mode. Within the concentration range of 0.2 × 10⁸–1.4 × 10⁸ CFU/ml, both modes demonstrated concentration-dependent variations in WS and figure of merit (FOM), with the even mode exhibiting superior detection performance. In addition to detecting the Bacillus cereus concentration, it can also detect S. aureus, Salmonella, Shigella, E. coli, Vibrio cholerae, and many other common pathogens that cause food poisoning or serious infections.

Plasmonic nanomaterials have garnered significant attention for their enhanced optical, antibacterial, and anticancer properties, owing to their surface plasmon resonance (SPR) effects. In this study, ZnO and ZnO/Ag nanoparticles were synthesized using green synthesis approach. The structural, morphological, and physicochemical properties of the fabricated nanomaterials were systematically characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and dynamic light scattering (DLS). XRD analysis confirmed the hexagonal wurtzite structure of ZnO, while additional peaks in ZnO/Ag nanoparticles indicated successful silver incorporation. TEM imaging revealed a spherical morphology with average particle sizes of 35 ± 10 nm for ZnO and 55 ± 10 nm for ZnO/Ag. The antibacterial activity of the nanoparticles was assessed against Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Streptococcus mutans, Staphylococcus aureus, and Enterococcus faecalis using broth microdilution method. ZnO/Ag nanoparticles exhibited superior antibacterial efficacy, particularly against Gram-negative strains, due to the synergistic action of ZnO-mediated oxidative stress and Ag⁺-induced membrane disruption. The plasmonic properties of Ag further contributed to the antibacterial effect by enhancing reactive oxygen species (ROS) generation under light exposure. Moreover, the MTT assay demonstrated a dose-dependent cytotoxic effect on A-549 lung carcinoma cells, with ZnO/Ag nanoparticles displaying a lower IC50 than ZnO. The enhanced anticancer activity was attributed to increased mitochondrial dysfunction, ROS generation, and apoptosis induction, further amplified by plasmonic interactions. These findings highlight the potential of ZnO/Ag nanomaterials as promising candidates for biomedical applications, particularly in antimicrobial and anticancer therapies.

We present a hybrid plasmonic platform that integrates plasmon-induced transparency (PIT) and perfect absorbance (PA) to achieve multi-band, tunable, and highly efficient light–matter interactions in the mid-infrared (mid-IR) spectral region. The system employs a dolmen-shaped nanoantenna configuration engineered to support the hybridization of bright dipole and dark quadrupole resonances. By systematically tuning structural parameters such as antenna separation and dielectric spacer thickness, the platform enables precise control over spectral splitting and absorption strength, giving rise to multiple perfect absorption peaks. To demonstrate the platform’s utility for molecular sensing, we modeled a protein bilayer characterized by vibrational signatures at the Amide I, II and III bands. Our results demonstrate that this PIT–PA integrated platform not only achieves near-unity absorbance across multiple spectral bands but also enables the label-free detection of distinct protein vibrational modes with high sensitivity. The platform holds strong potential for applications in biosensing, photodetection, and infrared energy harvesting, where multi-band operation and spectral precision are critical.

For females, particularly growing fetuses in the latter stages of pregnancy, progesterone plays a crucial function. However, one female sex hormone that falls within the category of estrogen is estradiol. Egg mellowing and emission are caused by an increase in estradiol degrees during the menstrual cycle. It is responsible for the pollinated eggs imbedding, which causes the uterine coating to solidify. Here, an innovative PCFD is projected to determine progesterone hormone (PH) and estradiol hormone (EH) in blood which involves an easy structure of square hole is treated as a core gap. The suggested PCFD is achieved an ultra-high relative sensitivity (RSE) as 99.92% at 2 THz. Furthermore, the loss in the projected PCFD is very tiny which proves the effectiveness of planned PCFD. Also, this PCFD has tunable design and simple structure; it can be fabricated easily using the prevailing fabrication schemes. As a result, the suggested PCFD will act a key role in chemical and bio-testing in diverse areas swiftly.

Surface plasmon polariton (SPP) waves are electromagnetic (EM) waves that travel over the interface between a metal and a dielectric. Typically, the conventional Drude model (DM), which uses integer order derivatives, has been employed to investigate SPP behavior. Since the classical DM does not exactly match experimental values for metal dielectric constants, it has been modified with the fractional calculus method to improve its modeling capabilities. The fractional method allows us to analyze system behaviors in non-integer domains that classic integer-order models cannot capture. In this paper, we use a fractional Drude model (FDM) with non-integer order derivatives to study SPP wave characteristics. A planar silver-glass interface is unitized to investigate the effect of the fractional-order parameter ( gamma ), which defines the order of the FDM. The impact of small variations of ( gamma ) from unity on dielectric constant and refractive index of metal is explored. Furthermore, important SPP properties such as effective propagation length, dispersion curve, and bandgaps are examined for various values of ( gamma ). Notably, setting ( gamma = 1 ) recovers results in agreement with the standard DM, validating the proposed mechanism. This theoretical study indicates that the optical characteristics are influenced by both the applied electric field frequency ( omega ) and the non-integer order ( gamma ) of FDM. This fractional order of FDM is tuned to ensure a good fit with the experimental data. It is hoped that these findings would be useful to plasmonic researchers.