Plasmonics最新文献

Two plasmonic nanoantenna configurations—nanodisk and nanostrip arrays—in a metal–insulator-metal (MIM) setup were proposed, optimized, and compared by simulating their optical properties in three-dimensional models using COMSOL Multiphysics software. The optical responses, including electric field enhancement, absorption, reflection, and transmission spectra, were systematically investigated. Optimized geometrical parameters led to a significant enhancement of the electric field within the gap layers and almost perfect light absorptance for both structures. The results showed that the enhancement of the electric field depends on the polarization of the incident light. For both polarizations, the periodic circular nanodisk array showed a stronger field enhancement with an electric field enhancement factor of 6.6 × 10⁶ and TE polarization, and a larger absorptance of 98% at its dipole resonance wavelength, indicating the fundamental plasmonic mode. In addition, weaker resonant modes were observed in the absorptance and reflectance spectra of both nanostructures, with the nanostrips exhibiting sharper and stronger higher-order modes, making them suitable for applications requiring precise wavelength selectivity and narrow-band responses. Despite their different geometric shapes, both structures exhibited similar optimized metal film thickness and nanoparticle height, comparable modes in number and position, and identical optimized light incidence angles. Furthermore, increasing the dielectric gap layer thickness and optimizing it to a specific value revealed its ability to measure the refractive index, making it a promising candidate for sensing applications.

Modeling slot waveguides using the analogy with transmission lines in microwaves proved itself to be an accurate and simple method for characterizing plasmonic field propagation. Here, the possibility of generalizing the applicability of this method to plasmonic circuits consisting of nanowires is analyzed. It is found that it can be applied as long as the circuit can be divided in regions with known transverse field distributions and propagation constants, the total matrix characterizing plasmon propagation being composed of propagation and interface matrices, as in slot waveguides, the elements of the latter being, however, defined in terms of butt-coupling transmission coefficients at the interface and not using the simple characteristic impedance expression used for slot waveguides.

Many biomolecules exhibit characteristic fingerprint spectra in the terahertz band. This paper describes an optimized detection method using the parametric multiplexing of terahertz metallic metasurface. The method can greatly enhance the terahertz absorption spectra of trace α-lactose analytes by multiplexing geometric parameters of the metasurface. Additionally, the dispersion relationship, electric field distribution, absorptivity and other characteristics of the metal metasurfaces are obtained. The relationship between the thickness of the trace sample, the structural parameters of the device and the enhancement characteristics is investigated. The results demonstrate that the designed terahertz metallic metasurface exhibits high sensitivity and stability in detecting the absorption fingerprint spectrum of biomolecules. The absorption enhancement factor of the 0.1-μm thick α-lactose sample to be tested on the metallic metasurface is about 264 times higher than the direct absorption of terahertz waves by the untreated specimen. The findings of this research offer new ideas and methods for further researches and applications in the field of biomolecule absorption detection.

This study explores the behavior of the SPPs mode propagating along a plasma-LiF-plasma planar waveguide structure. Real and imaginary parts of LiF permittivity are analyzed in the THz frequency range. Furthermore, the dependence of effective mode index, propagation length, permittivity of LiF, phase velocity and normalized propagation for different collisional frequencies, plasma frequencies, and LiF thickness are analyzed in the THz frequency spectrum. Based on the calculated numerical results, it is reported that different characteristics of electromagnetic surface waves are strongly influenced by physical parameters of isotropic plasma and LiF permittivity. The proposed waveguide scheme can be used in plasmonic sector for the development of novel plasma and LiF-based nano-plasmonic devices and making it ideal for high-performance optical communication and sensing applications in the THz frequency regime.

Graphene and its derivatives as multifunctional catalysts are in high demand, owing to their exceptional potential. Here, we synthesized Cu/Ni@rGO nanocomposite by using reduced graphene oxide (rGO) as a support which provided large surface area. A mixture of Cu and Ni nanoparticles (NPs) was embedded on its surface for sorption of heavy metal ions, i.e., Pb²⁺ and Cr⁶⁺, from binary mixture. Synthesis process of nanocomposite was monitored by UV-visible spectroscopy. FTIR analysis was performed to confirm the functional groups involved in synthesis and stabilization of the nanocomposite. The average size of nanocomposite was 26 nm calculated by XRD spectroscopy. SEM analysis revealed the thread-like structure of nanocomposite, while EDX gave information about elemental composition. Synthesized material was used to remove cations (Pb²⁺ and Cr⁶⁺) from binary mixture under tungsten lamp and without tungsten lamp. Under tungsten lamp, at 5 ppm concentration of binary mixture of cations, after 40 min of interaction with 10 mg adsorbent dosage at 45 °C temperature, 94% of cations was removed very efficiently. Thermodynamics studies showed that reaction of cations with nanocatalyst was spontaneous and exothermic in nature. Kinetics models were employed on experimental values and regression coefficient (R²) was near to unity (0.99) for pseudo 2nd order, which was considered the best fitted method for adsorption. Among sorption isotherms, the best fitted model was Freundlich isotherm as its R² value (0.97) is near to unity. On these adsorption isotherms, error analysis was also applied to attain precision on results. Reusability of material was analyzed 5 times by desorption process which confirmed its stability and higher catalytic efficiency.

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This research study focused on providing a solution to the problem of efficiency in the solar cell using window layer thickness. A novel Ag/WO₃/CuO/Si heterojunction solar cell geometry as a function of WO₃ window layer thickness via cost-effective hydrothermal and spin coating approaches has been demonstrated. The structural, morphological, and optical characteristics were systematically studied, indicating a direct correlation with the fabricated solace cells’ efficiency. In detail, a decrease in the WO₃ layer thickness from 150 to 50 nm resulted in the average transmission increment from 58 to 75%; this, in turn, allowed higher power conversion efficiency enhancement from 0.063 to 1.387%. Specifically, short circuit currents of 0.307 and 6.206 mA/cm² and open circuit voltages of 0.259 and 0.779 V were attained for the aforementioned layers’ thickness, respectively.

Perovskite solar cells have emerged as a promising third-generation solar cell technology, characterized by high efficiency and low fabrication costs, garnering significant research attention in recent years. In this study, the impact of embedding the cluster of cubic plasmonic nanoparticles within the ultra-thin absorber layer of perovskite solar cells was investigated. Various types of metallic nanoparticles (including Au, Ag, Al, and Cu) were employed in the perovskite absorber layer, each with different thicknesses and widths. This facilitated a comprehensive comparison aimed at identifying the optimal structure for light absorption within the bandgap range of the perovskite absorber layer—specifically, 300 to 800 nm, corresponding to a bandgap energy of 1.55 eV. The layers used in the design of the perovskite solar cell in this research are SiO₂/ITO/SnO₂/MAPbI₃/MoO₃/Au. Optical and electrical analyses revealed that the local field intensity is significantly stronger at the edges of metallic nanoparticles. Notably, the efficiency of perovskite solar cells is enhanced by 56.87% (rising from 18.24 to 28.62%) with the incorporation of an Ag-based cluster of cubic nanoparticles, compared to perovskite solar cells without metallic nanoparticles. This achievement resulted in an overall efficiency of 28.62% and a short-circuit current of 31.22 mA/cm². This result closely approaches the efficiency limitation of perovskite absorber layers, which indicates the potential for significant performance enhancements in future perovskite solar cell technologies.

Colloidal In₂O₃NPs-MWCNTs heterostructure (NPs) were successfully synthesized by a facile one-step Q-switched Nd: YAG laser ablation of indium target in CNTs suspension at room temperature. Raman spectroscopy and optical absorption analysis of the prepared samples confirmed the formation of In₂O₃NPs-MWCNTs heterostructure. Transmission electron microscope (TEM) investigation of In₂O₃-CNTs structure and pure In₂O₃ nanoparticles revealed the formation of spherical nanoparticles with average size of 66 nm and 19 nm, respectively. The heterojunction photodetectors were fabricated by drop casting of colloidal In₂O₃NPs-MWCNTs NPs onto a single crystal silicon wafer. I–V characteristics of the In₂O₃NPs/Si and In₂O₃NPs-MWCNTs/Si heterojunctions under both dark and light conditions revealed rectifying properties and good photo-response. The built-in voltage was determined from the C–V measurements which revealed an abrupt junction and their values of 1.05 V and 0.59 V for In₂O₃NPs-MWCNTs/Si and In₂O₃NPs/Si, respectively. In₂O₃NPs-MWCNTs/Si photodetector demonstrated the highest responsivity and quantum efficiency of 1.3 A/W and 3.5 × 10²% at 450 nm, respectively. This In₂O₃-MWCNTs heterostructure-based photodetector with improved performance may open the door to effective Vis–NIR photodetection applications.

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Cancer is a leading cause of morbidity and mortality worldwide. Millions of individuals throughout the world suffer from cancer and other illnesses. This is a leading cause of human death each year. Huge efforts were made to develop simple, precise, and cost-effective technologies for detecting various diseases. As the detection of cancer and diabetic disorders has received a lot of interest in the field of biosensing, several methods have been developed to detect these diseases with high accuracy. This study investigates the possibility of surface plasmon resonance (SPR) for human breast cancer detection utilizing a bimetal silver with gold in permutation and hybrid organic–inorganic halide perovskites (MAPbX₃ ≡ CH₃NH₃PbY₃, with M = CH₃, A = NH₃, and Y = Br) sensor that operates at a specific wavelength of 633 nm. Early cancer identification is critical for improving patient outcomes, and SPR presents a promising path for label-free, sensitive detection of cancer biomarkers.

The development of highly sensitive and reliable biosensors for hemoglobin detection is crucial for various medical and diagnostic applications. Hemoglobin, a vital protein in red blood cells responsible for oxygen transport, serves as an important biomarker for numerous health conditions. Accurate and rapid measurement of hemoglobin levels can aid in the early detection and monitoring of anemia, blood disorders, and other medical conditions. This study presents a biosensor design for hemoglobin detection, integrating a graphene-based metasurface with circular and square ring resonators constructed from silver and gold nanostructures. The proposed sensor leverages the unique plasmonic properties of plasmonic nanostructures and the remarkable optical characteristics of graphene to enhance its performance. Extensive parametric analysis and optimization are conducted to enhance detection accuracy among other performance parameters. Detection analysis demonstrated the sensor’s ability to resolve changes in hemoglobin concentration through distinct shifts in transmittance and reflectance spectra. The resulting sensor exhibits enhanced sensitivity of 3500nmRIU⁻¹ to infrared energy, maximum FOM of 17.6, and detection limits of 0.05 among other performance parameters. Furthermore, machine learning optimization using 1D convolutional neural network regression is employed to predict the sensor’s behavior achieving high accuracy with maximum R² scores ranging up to 1. The sensor design exhibits remarkable potential for applications requiring highly sensitive and precise hemoglobin monitoring in medical diagnostics and healthcare.