Plasmonics最新文献

This study investigates the impact of laser pulse energy (500 mJ/pulse) on silver, gold, and silver@gold NPs and deposited on porous silicon. The objective is to assess their effects on structural, optical, morphological, and electrical properties, aiming to identify optimal conditions. Nanoparticles are produced through the technique of pulsed laser ablation in liquid (PLAL). This involves employing a Q-switched Nd: YAG laser operating at a wavelength of 1064 nm and pulse duration of 10 ns. X-ray diffraction (XRD) analysis validates the crystalline development of (core–shell) NPs, evident from the presence of XRD peaks corresponding to Au and Ag NPs. Morphological analysis reveals excellent adhesion between NPs and the substrate (PS), enhancing structural stability. UV–vis spectra demonstrate a localized surface plasmon resonance (LSPR) band within the 420–540 nm range. This band shifts from two peaks to one with increased gold content. A comparison of the photoluminescence emission spectra of porous silicon and Ag@Au NPS/PS at room temperature. The porous silicon exhibits an extreme PL emission band broadening centered at a visible wavelength of 620 nm (2.033 eV), which reveals the excellent quality of the PS structure. Photodetector measurements highlight maximum responsivity for the Ag@Au/PS photodetector. These Ag@Au NPs show promising attributes for high-performance photodetector applications.

This theoretical study focuses on the performance of the surface plasmon resonance (SPR) sensor by strategically including various heterostructures in between the plasmonic metal and sensing medium. The heterostructure consists of a wurtzite nitride semiconductor and a two-dimensional (2D) material, specifically transition-metal dichalcogenides (TMDC). The angular interrogation approach is used to assess the sensor’s efficacy which includes all commonly used critical parameters. The study also outlines the range of refractive indices (RI) in the sensing medium that elicit exceptional and notable responses from the proposed SPR structure. Based on the sensitivity, detection accuracy (DA), and figure of merit (FOM) values, it is determined that a TMDC material, specifically tungsten disulfide (WS₂), combined with a wurtzite nitride semiconductor (such as gallium nitride, indium nitride, or aluminum nitride), offers the best performance. Among all heterostructures, GaN-WS₂ exhibits the highest sensitivity. In contrast, AlN-WS₂ exhibits remarkable performance in terms of DA, FOM, and the evanescent field intensity factor. Furthermore, the proposed SPR structure with InN-WS₂ demonstrates maximum shifts in resonance angle, occurring within sensing RI range of 1.372 to 1.389. Similarly, AlN-WS₂ exhibits the maximum shifts in resonance angle within the range from 1.387 to 1.4. GaN-WS₂, however, shows the strongest response to resonance angle shifts within the range from 1.38 to 1.396.

In this study, a multi-layered and bi-directionally excitable plasmon-induced transparency (PIT) device with multiple graphene layers was designed. The PIT window was regulated by controlling the Fermi level of graphene, resulting in an increase in the resonance frequency and dip depth of the PIT transmission valleys with an increase in the Fermi level. Theoretical investigations were then conducted. Subsequently, the influence of interlayer distance, individual component size, and relative positioning of graphene on the performance of PIT was studied. When employed as a biosensor, it could only be utilized under x-polarized TM waves, exhibiting a maximum sensitivity of 8.2THz/RIU. As an optical switch, it exhibited the highest modulation depth of 89.7% at 9.04THz under x-polarized waves, and a maximum modulation depth of 94.6% at 2.8THz under y-polarized waves. This theoretically designed PIT device can have potential applications in both sensors and optical switches.

The copper nanoparticles (Cu-NPs), through a novel green synthesis method utilizing Tinospora Cordifolia (TC) aqueous leaf extract as a reducing and stabilizing agent, were synthesized, and investigated for their dye degradation potential. The bio-synthesis process, which is operationally simple, non-toxic, and cost-effective, involves using cupric oxide (CuO) as precursor material. The degradation of dyes in water bodies is challenging research due to their stable nature; therefore, it is essential to develop potential catalyst materials with desirable properties to degrade dyes in water bodies. The CuNPs were characterized using X-ray diffraction (XRD), UV–Vis spectrometer, scanning electron microscopy (SEM), and a Fourier transformed infrared spectrometer (FTIR). The FTIR results confirmed the presence of phytochemicals involved in the reduction, capping, and stabilization of CuNPs, which was corroborated by the XRD data. The photo-catalytic activity of biosynthetic CuNPs was studied using methylene blue (MB) dye upon exposure to visible light source irradiation. The results showed that bio-synthesized CuNPs exhibited a high potential for dye degradation for the methylene blue dye in the presence of a visible light source and a dye degradation rate of 81% was achieved. The green-synthesized CuNPs have proven to be a potential candidate for efficiently removing dyes from water bodies and provide a sustainable, environmentally friendly method for producing metal nanoparticles with excellent photo-catalytic properties.

A three-layer type of solar absorber is developed with a graphene layer to observe a perfect absorption level in this work. The top (resonator) uses Iron (Fe), the middle (substrate) layer is Indium Antimonide (InSb), and the base (ground) layer with Aluminium (Al). The proposed design can perform the absorption percentages of 94.3% at the 2800 nm ultra-broadband bandwidth range. Absorption levels greater than 95% (96.6%) at a 1470 nm and a 750 nm bandwidth above 97% (98.1%). The contribution steps of the design and the respective absorption A, reflectance R, and transmittance T outputs are explored. AM performances and parameter variations of thickness and width of a base layer, resonator, and substrate thickness can be studied. Moreover, chemical potential and incidence angle changing from 0 to 60 degrees with a 10-degree separation are also presented. The comparison table and electric amount testing sections are also included in a recent paper.

In this study, Γ-shaped rectangular resonators, which are created in a metal insulator metal (MIM) structure, have been studied analytically and numerically. The metal is silver and rectangular resonators are filled by Si and the peak of transparency profile is tuned in the communication band with proper geometrical parameters. By employing 2-D finite difference time domain method (FDTD), simulations show a plasmonic induced transparency (PIT) window in the transmission diagram. The PIT is created by instructive and destructive interference between bright and dark resonator modes. The presented structure demonstrates tunable transparency window by variation of symmetry parameter, s. The maximum group velocity is obtained 0.1 ps in communication band corresponded to 30 μm traveling of light in the vacuum which is comparable to previous articles. The proposed structure may have potential applications in optical memory and delay blocks in designing integrated optical circuits.

Surface-enhanced Raman scattering (SERS) is widely employed because it offers quick, microscopic, and traceless detection. This study used high-voltage and low-voltage ultrasonic oscillation to embed gold-silver nanoparticles (Au-Ag NPs) into the pores of chemically modified ultrathin anodic alumina (AAO) films, resulting in a highly sensitive three-dimensional SERS substrate. We improved the substrate’s stability and Raman activity by adjusting the particle alloy ratio. For the substrate in this alloy ratio, the Raman signal of probe molecules (Rh6G) adsorbed on the substrate surface is enhanced. the enhancement factor (EF) was as high as 1.40 × 10⁷, the relative standard deviation (RSD) of 10.6%, and the concentration of Rh6G shows a linear relationship with Raman intensity, with a linear correlation coefficient of 0.961. In addition, we evaluated the substrate’s detection effect on thiram molecules. It has been proven that this structure has good practicality and high sensitivity as a Raman enhanced substrate.

Sexually transmitted infections (STIs) due to Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) pose global health challenges due to their widespread prevalence through sexual contact. Rapid and user-friendly diagnostic solutions are crucial to curb their spread and mitigate potential complications. In this article, we introduced a portable plasmonic biosensor kit for the detection of NG and CT bacteria in urine samples. Our platform merges label-free plasmonic nanohole sensing with lens-free computational imaging, revolutionizing point-of-care pathogen diagnosis. The system captures and analyzes diffraction field images, uncovering subtle bacterial presence cues. With a low-cost pump compartment and flow cell, we ensured precise sample delivery to the plasmonic chip. The system software controls hardware setup, test execution, and image analysis for bacterial detection. Leveraging control and sensor antibodies, our technology excels in sensitivity and selectivity. Microfluidic channels with multiple sensor locations enable separate NG and CT testing. Our imaging-based approach allows simultaneous detection, obviating the need for separate assays. Integrating multiple sensor sites ensures robust high-throughput testing. Employing plasmonic pixels for control tests effectively mitigates the background noise. Simple optics, affordable components, and controlled environment underscore the practicality of our handheld biosensor. Strong detection limits, e.g., 452 CFU/mL for NG and 121 CFU/mL for CT bacteria (CFU: colony-forming unit), position our technology as a transformative point-of-care diagnostic tool for pathogenic diseases, bridging accessibility and affordability gaps.

Ellipsoidal plasmonic particles are of huge importance in the biosensing field due to their orientation-specific light scattering properties and higher area of surface-adhesive interactions. In this paper, we present a computational investigation of the orientation-specific plasmonic properties of graphene-wrapped—Au nano ellipsoids of various aspect ratios and graphene layer thicknesses using the discontinuous Galerkin time domain (DGTD) method. We could observe that both the dipolar and quadrapolar resonances of Au ellipsoids are strongly modulated by graphene layer. Furthermore, we have modelled graphene wrapped Au ellipsoidal nanoarray biosensor with optimized orientation having very high sensitivity (484 nm/RIU) towards refractive index changes associated with various fibrillation stages of beta amyloid (biomarker for Alzheimer’s disease) compared to the bare Au nanoellipsoidal biosensor.

In this paper, we have proposed a new multilayer structure and investigated its performance as a chemical sensor utilizing surface plasmon resonance. Our proposed design consists of a black phosphorus layer sandwiched between a metal layer and a graphene layer, blue phosphorene/MoS₂ heterostructure layers placed over it, and the sensing layer containing the analyte placed on top. A CaF₂ prism in the Kretschmann configuration is employed to excite surface plasmon resonance (SPR), and the angle interrogation method is used for analysis. Sellmeier equations calculate the reflectivity and other parameters of the multilayer design. We also study the effect of the combination of BP and metal interlayer. Analysis of the proposed design shows significantly improved sensitivity compared to recent SPR-based sensors. In this paper, the sensitivity of 466°/RIU is obtained with silver metal, BP, graphene, and BlueP/MoS₂ layers SPR sensor.