Plasmonics最新文献

This work investigates the excitation of plasmons in the common region between two coaxial cylindrical waveguides nested within each other, utilizing planar electromagnetic waves. The structure under consideration comprises a metallic antenna shielded with another metallic thin layer, both metals assumed to be cylindrical symmetrically without a gap and in a concentric configuration. The conductivity of the metals is evaluated using the Drude theory. An incident electromagnetic wave in B-mode with (B_zne 0) is radiated onto the mentioned antenna. By employing wave scattering theory and solving the field equations in each region, including the vacuum, outer metallic thin layer, and inner metallic core, the surface charge density resulting from the presence of surface plasmons at the interface between the inner metallic core and the outer metallic layer, as well as between the metallic layer and the vacuum region, is calculated and analyzed. The variations in surface plasmon density at the first interface (the common boundary between the two metals) and the interface between the metal and vacuum are investigated concerning changes in the incident wave frequency and the radii of the antenna layers. It is demonstrated that the excitation of plasmons occurs most significantly in the frequency range where the conductivities of the inner metallic core and the metallic layer have opposite signs, leading to synchronization between surface plasmons.

A novel D-type photonic crystal fiber optical plasma sensor (PCF-SPR) based on a composite micro-grating of Au and tantalum pentoxide (Ta₂O₅) is proposed. The simulation and corresponding numerical characterization were performed using COMSOL Multiphysic software. In order to obtain a simple and practically feasible structure, the Au plasma material and the sensing medium were placed outside the optical fiber. A thin layer of Ta₂O₅ is used as a coating to protect the gold layer. This composite micro-grating PCF sensor has a maximum sensitivity of 25,000 nm/RIU and sensor unit with a detection resolution of 4.0 × 10⁻⁶/RIU in the near infrared in the refractive index range of 1.34 ~ 1.41. Dependences of loss spectrum on the PCF parameters (air hole diameter and lattice constant) and the grating structure (grating thickness and width) are systematically analyzed. This sensor with grating structure is a more sensitive sensor for broad IR detection, suitable for biosensors, chemical detection, and food safety.

Plasmonic nanomaterials have revolutionized sensing and imaging technologies due to their unique optical properties, particularly surface plasmon resonance (SPR). These materials offer enhanced sensitivity and resolution, making them promising candidates for applications in deepfake image detection, where accurate authentication of digital content is crucial. This work presents the application of plasmonic nanomaterials in enhancing sensing and imaging capabilities for deepfake detection. Gold nanoparticles functionalized with specific ligands are employed to exploit SPR effects, enabling sensitive detection of minute alterations in image content. A spectroscopic setup is utilized to measure the SPR shifts corresponding to changes induced by deepfake manipulations. Experimental results demonstrate that the SPR-based sensing approach achieves a detection accuracy of over 95% in distinguishing deepfake images from authentic ones. The SPR sensor exhibits a high signal-to-noise ratio, providing robust performance even in complex imaging scenarios with varying lighting conditions and image resolutions. Plasmonic nanomaterials, leveraging SPR, offer a reliable method for enhancing deepfake image detection capabilities. The demonstrated high accuracy and sensitivity underscore their potential in combating digital media forgery, contributing to the development of more secure and trustworthy authentication systems for visual content.

This study proposes an eccentric core optical fiber biosensor based on the surface plasmon resonance phenomenon, utilizing COMSOL Multiphysics 6.2 finite element method (FEM). An Ag film with a thickness of 30nm is coated on the cladding of the eccentric core optical fiber. The analytical layers employed include air, water, blood plasma, and a self-set refractive index (RI) of 1.373. A 5-nm thick TiO₂ layer is coated between the Ag film and the analyte. This TiO₂ layer not only prevents the Ag layer from oxidation but also enhances the sensor’s sensitivity. The sensor serves as a theoretical foundation for experimental research. The wavelength sensitivities have been calculated, with the self-set RI of 1.373 exhibiting the maximum sensitivity of 1785.714 nm/RIU and a resolution of 5.60 × 10⁻⁵ RIU. The proposed sensor presents itself as a promising candidate for a low-cost, simple-geometry biochemical sensing solution.

This investigation presents the design, simulation, and performance analysis of a terahertz-based biosensor for hemoglobin detection. The sensor architecture incorporates a synergistic combination of graphene, gold, and silver metasurfaces in a hierarchical resonator structure. Extensive parametric analysis was conducted to optimize the sensor's performance characteristics. The optimized sensor demonstrates high sensitivity, achieving up to 1000 GHzRIU⁻¹, with a figure of merit of 3.289 RIU⁻¹. Experimental results indicate effective detection of hemoglobin concentrations ranging from 10 to 40 g/L, corresponding to refractive indices between 1.34 and 1.43. Electromagnetic field distribution analysis exemplifies peak absorption at 0.65 THz. Furthermore, the sensor’s potential for binary encoding applications was evaluated with remarkable performance. Machine learning optimization, employing a decision tree regressor, demonstrates an optimal R² score of 100% across various parameter combinations, suggesting potential for the development of accurate sensing systems. The proposed sensor design represents a significant advancement in terahertz biosensing technology, with implications for enhanced medical diagnostics and biomedical research applications.

Nowadays, controlling the light reflection and transmission by metasurface nanostructures opens pathways for efficient energy harvesting in nanophotonics and optoelectronic devices. This paper demonstrates a metasurface broadband absorber in the visible wavelength region of 400–800 nm using two-dimensional titanium carbide (Ti₃C₂T_x) MXene. A high average absorption of 97.85% over a wide wavelength region of the incident light (0.4 µm) is achieved. This significant absorption is due to the strong localized surface plasmon caused by the Ti₃C₂T_x periodic nanoarrays top-mounted on SiO₂/Au/glass layers. The proposed MXene-based absorber also shows broadband and high average absorption for both transverse electric (TE) and transverse magnetic (TM) polarizations under a wide range of oblique incidence and azimuthal light angles, especially it reaches over 99% for TM polarization in some ranges. The proposed absorber can be used in photodetectors, sensors, and applications where the incident angle and/or polarization are constantly changing.

Tear biomarkers have received much attention for non-invasive monitoring of ocular and systemic diseases. Although various approaches have been developed for on-site detection of tear biomarkers, there is still the limited number of simple and reliable sensing platform in the clinical setting. Here, we introduce a plasmonic enzyme-linked immunosorbent assay (ELISA) that utilizes Ag/chitosan plasmonic paper with dual-signal readout to detect immunoglobulin G as a model tear biomarker. The sensing mechanism for a colorimetric and surface-enhanced Raman scattering (SERS) dual-signal readout is attributed to the etching of Ag nanoparticles anchored to the plasmonic paper. This etching induces both a color shift and a reduction in the Raman enhancement of the plasmonic paper. The optimized etching system demonstrates the feasibility of performing simultaneous immunoassay and etching on a plasmonic substrate without requiring an additional etching step. The detection limit was achieved at concentrations approximately 100 times lower than the physiological tear concentration, along with selective detection in simulated tear fluid. Furthermore, the dual-mode detection improves accuracy and efficiency by comparing the results of overlap detection range and enabling pre-screening with colorimetric results prior to SERS analysis. This approach holds promise as a versatile point-of-care sensing platform that can easily and reliably detect tear biomarkers.

This research included the production of copper oxide nanoparticles (CuO NPs) using various pulsed laser ablation energy (PLAL) embedded in substrates made of porous silicon (PS). The PS substrates were created using the photoelectrochemical etching (PECE) technique of Si n-type (111). The research examined the impact of pulse laser ablation energy on many attributes of the created samples, involving their structural, electrical, optical, photodetector, and morphological properties. XRD analysis reveals a prominent and broad diffraction peak at an angle of 28.4^ο for the porous silicon and other diffraction peaks at different angles, indicating the presence of the CuO NPs phase corresponding to the monoclinic crystal structure. The SEM image demonstrates that PS is sponge-like, while CuO NPs display randomly dispersed spherical grains, and appear to vary in the particle size due to the change in laser pulses energy.

The optical properties of the fabricated specimens were analyzed utilizing photoluminescence and UV–vis absorption spectroscopy. The results suggested that a change in laser pulse energy caused a change in the energy gap that ranges from 2.7 to 3.5 eV. The created samples' current density-voltage (J-V) characteristics were analyzed under two conditions: in dark and light while varying the laser pulse energy. The J-V characteristics curves demonstrate that increasing the pulse energies of laser ablation resulted in higher current density flowing through the samples, particularly when the sample was created at 900 mJ. The photocurrent density exhibited a significant association with the increase in input light intensity, so enabling its utilization as a photodetector device. Nevertheless, altering the laser ablation pulse energy resulted in modifying the photocurrent for all CuO NPs/PS specimens. The inclusion of CuO nanoparticles in the PS samples led to a considerable enhancement in the responsivity (Rλ) when compared to the PS-only sample. The reason for this is that CuO nanoparticles have the ability to absorb light throughout a wide range of wavelengths, from ultraviolet-visible to near-infrared. The highest detectivity (D*) value was recorded when the laser energy was set at 700 mJ. The observed phenomena can be ascribed to fluctuations in the size or morphology of CuO NPs caused by variations in laser ablation pulse energy during its preparation. Furthermore, the constructed photodetector exhibited enhanced external quantum efficiency (Q.E), specifically in the ultraviolet (UV) range. The findings of this research are significant in the progress of optoelectronic and photodetector devices that rely on CuO NPs and PS.

This work reports on the plasmonic properties of a Sn metasurface structure, in the wavelength region of 0.4–4(mu )m. On top of a glass substrate, the metasurface is formed by a central Sn nanobar surrounded with hexagonally oriented Sn nanobars. Multiple plasmonic resonances are observed, the plasmonic coupling effect at the Sn metasurface is revealed, and the corresponding electromagnetic field distributions are demonstrated. The results show that the electromagnetic field intensity near the surface of nanostructures can be enhanced by the near-field effect. The plasmonic resonance wavelength associated with the Sn nanobars can be tuned in the studied wavelength range, by adjusting the parameters of the metasurface. Based on this study, we suggest that the structure of the Sn metastructure proposed in this work be implemented in the design for plasmonic devices at 0.4–4(mu )m wavelengths.

A pulsed laser was used to make the Au@Ag@Au core-double shell nanoparticles in a DMF solution. The samples were characterized and inspected to confirm the structure investigated by XRD tests, and the average crystallite size was 51.988, 51.222, and 47.482 nm at laser energy 300, 500, and 700 mJ, respectively. Transmission electron microscopy (TEM) was employed to confirm the nanostructure of the particles. The particles were found to have a spherical form, with mean diameters of 15 nm, 9.5 nm, and 7.5 nm at laser energy of 300, 500, and 700 mJ, respectively. Showing the surface plasmon resonance peak for each gold and silver NPs, we observe a phenomenon a blue shift in absorption peak with increased laser energy, which signifies a reduction in the dimensions of the nanoparticles. The energy gap for samples was determined using Tauc’s relation, which were 1.52, 1.53, and 1.54 eV at laser energy 300, 500, and 700 mJ, respectively. The stability of the nanomaterials was assessed using zeta potential analysis, which measured the stability of every specimen in a DMF solution. The computed zeta potentials for the samples were − 19.6 mV, − 29.3 mV, and − 41.6 mV, at laser energy of 300, 500, and 700 mJ, respectively. After that, Au@Ag@Au core-double shells nanoparticles were tested as novel antimicrobial agents against Streptococcus mutans as well as Klebsiella pneumoniae. The results showed that the Au@Ag@Au core-double shells were great agents for killing both types of bacteria and inhibiting bacterial biofilm formation. The results collectively indicated that Au@Ag@Au NPs had the potential to serve as an alternate antibacterial agent.