Plasmonic Multilayers Research Articles

Hybrid modes in multilayer/antenna architecture set side-band-selective molecular Raman scattering

Abstract Technologies with tag-less capacity for analyzing molecules, are poised to make significant advancements in the healthcare industry with a substantial potential to improve sensitivity for individual molecules and binding events. Plasmonics has the potential for enhanced system response when emitters are included in the full architecture. Here, a hybrid multilayer including a sequence of metals and dielectrics has been examined. The surface of the multilayer is covered with 30-μm height features working as plasmonic antennae. Their contribution to the emission of the system has been analyzed. The multilayer has been coupled with a prism to excite the polaritons in an experimental optical setup to measure the reflected and transmitted signals. The measurements demonstrate the surface plasmon polariton/antenna mode hybridization. The optomechanics of the plasmonic resonant multilayer has been studied with reference to the refractive index of the surrounding medium as well as to the incident angle of the exciting beam. Then, the experimental shifts have been measured according to the optomechanical spectrum of the naïve plasmon resonant multilayer. The optomechanics of the plasmonic resonant multilayer, which has shown a natural resonance at ω = 96 MHz , has been coupled with a molecular emitter, e.g. a dye. As the concentration of the red dye increases, the intensity of the peaks at ω > 96 MHz raises, suggesting an important sensitivity in the anti-Stokes domain. On the other side, the decay is equal to κ = 1.1 × 10 − 2 MHz showcasing a high quality factor ( Q = 9.6 × 10 3 ). For validation of increased sensitivity in the anti-Stokes region, bovine serum albumin (BSA), a protein active in the Raman region, has been tested and, through an image-based analysis, the molecular pattern recorded. The demonstrated potential of utilizing optical resonance shifts to investigate molecular patterns is highly promising. Therefore, the proposed sensing method represents a significant advancement in the field, offering new opportunities for the sensitive detection of biomolecules.

Three-Phase Catassembly of 10 nm Au Nanoparticles for Sensitive and Stable Surface-Enhanced Raman Scattering Detection.

Interfacial self-assembly with the advantage of providing large-area, high-density plasmonic hot spots is conducive to achieving high sensitivity and stable surface-enhanced Raman scattering (SERS) sensing. However, rapid and simple assembly of highly repeatable large-scale multilayers with small nanoparticles remains a challenge. Here, we proposed a catassembly approach, where the "catassembly" means the increase in the rate and control of nanoparticle assembly dynamics. The catassembly approach was dropping heated Au sols onto oil chloroform (CHCl3), which triggers a rapid assembly of plasmonic multilayers within 15 s at the oil-water-air (O/W/A) interface. A mixture of heated sol and CHCl3 constructs a continuous liquid-air interfacial tension gradient; thus, the plasmonic multilayer film can form rapidly without adding functional ligands. Also, the dynamic assembly process of the three-phase catassembly ranging from cluster to interfacial film formation was observed through experimental characterization and COMSOL simulation. Importantly, the plasmonic multilayers of 10 nm Au NPs for SERS sensing demonstrated high sensitivity with the 1 nM level for crystal violet molecules and excellent stability with an RSD of about 10.0%, which is comparable to the detection level of 50 nm Au NPs with layer-by-layer assembly, as well as breaking the traditional and intrinsic understanding of small particles of plasmon properties. These plasmonic multilayers of 10 nm Au NPs through the three-phase catassembly method illustrate high SERS sensitivity and stability, paving the way for small-nanoparticle SERS sensing applications.

Enhanced Sensitivity and Detection of Near-Infrared Refractive Index Sensor with Plasmonic Multilayers.

In this work, the multilayer of the surface plasmon resonance (SPR) sensor was optimized to achieve the maximum sensor sensitivity. By optimizing the thickness of the silver layer (Ag) and dielectric films (TiO2 and AlAs), the optimum sensitivity of the SPR sensor could be obtained. The performance of the SPR sensor proposed was compared with control simulations utilizing zinc oxide (ZnO) and molybdenum oxide (MoO3). The numerical results indicate that the figure-of-merits (FOM) of the SPR sensor was achieved around 150/RIU, corresponding to the sensor sensitivity of 162.79°/RIU with the optimized thicknesses of the TiO2, Ag, and AlAs layers of 140 nm, 60 nm, and 25 nm, respectively. This refractive index sensor shows the FOM to have high detection accuracy and high sensitivity that lead to finding potential application in bio-chemical detection with a small volume of liquid used in biological diagnosis.

Two-dimensional plasmonic multilayer as an efficient tool for low power random lasing applications

Multi wavelength lasing is desired in two-dimensional flexible plexcitonic nanostructures through surface lattice plasmon amplification. For this purpose, gold nano-rods covered by the gold dispersed Rhodamine B was used as the first gain media. Then, the spacer layer by Poly-Vinyl-Pyrrolidone polymer was implemented to enhance the total internal reflection between polydimethylsiloxane substrate and this polymer. Finally, it was coated by methylene Blue dye with three different gold concentrations as the second gain media. To achieve multi-wavelength random laser, these three layers pumped by nanosecond green laser and the lasing were collected by spectrometer due to band-edge lattice plasmons in the arrays of plasmonic nano rods in a homogeneous environment. Based on the results, narrow emission peaks were emerged with a full width at half maximum less than 2 nm for every wavelength region, and threshold lasing reduced to the minimum value, along with the maximum emission intensity of multi-wavelength region.

Paper-Based SERS Sensing Platform Based on 3D Silver Dendrites and Molecularly Imprinted Identifier Sandwich Hybrid for Neonicotinoid Quantification.

Real-time monitoring of neonicotinoid pesticide residues is of great significance for food security and sustainable development of the ecological environment. Herein, a paper-based surface-enhanced Raman scattering (SERS) amplified approach was proposed by virtue of multilayered plasmonic coupling amplification. The unique plasmonic SERS multilayer was constructed using three-dimensional (3D) silver dendrite (SD)/electropolymerized molecular identifier (EMI)/silver nanoparticle (AgNP) sandwich hybrids with multiple hotspots and a strong electromagnetic field in nanogaps. Dendritelike 3D silver materials with remarkably high accessible surface areas and the lightning rod effect constituted the first-order enhancement of paper-based sensors. Molecular identifiers coated upon an SD layer as the interlayer were used for target capture and enrichment. Subsequently, AgNPs featuring rough surface and local plasma resonance decorated as the top layer formed the secondary enhancement of the amplification strategy. As the most brilliant part, dendritelike 3D silver coupled with AgNPs has established double Ag layers to accomplish a multistage enhancement of SERS signals based on the superposition of their electromagnetic fields. Owning to the distinctive design of the multiple coupling amplification strategy, the fabricated SERS paper chips demonstrated impressive specificity and ultrahigh sensitivity in the detection of imidacloprid (IMI), with a detection limit as low as 0.02811 ng mL-1. More importantly, the multiple SERS enhancement paper chip holds great potential for automated screening of a variety of contaminants.

Robust polarization twist by pairs of multilayers with tilted optical axes

Polarization of photonic beams makes a continuous information carrier and thus modifying it dramatically within a short distance is desirable for numerous optical devices. The easiest way to emulate anisotropy, which is a prerequisite for any polarization conversion, is utilizing thin slices of plasmonic multilayers, whose performance is limited by the inevitable losses. Such a difficulty gets overcome by using pairs of these slices in a bilayer configuration and optimizing the direction of their optical axes. In this sense, the losses are balanced by the interplay between fields in each slice and the overall interference scheme yields closer-to-desired transmissions. Several realistic designs giving effective polarization twists of substantial immunity to fabrication defects or misalignment in oscillation frequency and incidence angle, are obtained. These structures are both efficient and minimalistic; thus can be useful in many photonic systems requiring robust polarization engineering and compact packaging.

Comb-like scattering realized by cylindrical plasmonic multilayers

We study the comb-like scattering response of cylindrical multilayered plasmonic nanostructures. Through oxide semiconductors with different doping levels, the comb-like scattering made up of multiple Fano resonances can be achieved with enough scattering excursion. Each sharp Fano resonance is associated with a degenerate state between a bipolar cloaking and a bipolar resonant scattering. When the semiconductor shell is thin enough, the scattering response is independent of the core and background materials, and even the size of the nanostructure under quasi-static conditions. The physical mechanism of the proposed comb-like device is explained by using full-wave electromagnetic simulation. Moreover, the scattering cross section of the device with a considerable thickness can exhibit reliable comb-like scattering under different thicknesses and material parameters, which is suitable for optical tagging applications.

Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors.

We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material.

Zinc Oxide Based Plasmonic Multilayer Resonator: Localized and Gap Surface Plasmon in the Infrared

Using alternative plasmonic materials, we experimentally demonstrate gap plasmon resonances in metal–insulator–metal nanostructures in the near- and mid-infrared wavelength regions utilizing gallium doped zinc oxide as the metallic component and undoped zinc oxide as the dielectric. We show that similar to metal–insulator–metal resonators previously demonstrated with noble metals, the layered transparent conducting oxide nanodisks support gap surface plasmon resonances characterized by highly confined electromagnetic fields in the dielectric gap. Such resonances can be tailored to desired values by varying the dielectric-layer thickness. Utilizing these observed gap plasmon resonance, we examine the potential of our structure for sensing applications by measuring the surface enhanced infrared absorption of an octadecanethiol layer. The layered nanostructure can detect very weak absorption resonances in nanoscale volumes of absorbing material deposited over the nanodisk resonator.

Multiperiodicity in plasmonic multilayers: General description and diversity of topologies

We introduce multiperiodicity in periodic metal-dielectric multilayers by stacking more than two types of metal and/or dielectric layers into the unit cell. A simple way to characterize arbitrary multiperiodic multilayers using permutation vectors is suggested and employed. Effects of multiperiodicity up to its fourth order are investigated. We demonstrate that various topologies of multiple-sheet isofrequency and dispersion surfaces exist for such plasmonic multilayers, including a photonic realization of nontrivial isolated Dirac cones.

Metallic Nanowire Array–Polymer Hybrid Film for Surface Plasmon Resonance Sensitivity Enhancement and Spectral Range Enlargement

In this paper, the coupling interaction is investigated between a metallic nanowire array and a metal film under the Kretschmann condition. The plasmonic multilayer is composed of a metallic nanowire array embedded in a polymer layer positioned above a metal film, exploiting the classical surface plasmon resonance (SPR) configuration. We analyze the influence of various structural parameters of the metallic nanowire array on the SPR spectrum of thin metal film. The results show that the coupling interactions of nanowires with the metal film can greatly affect SPR resonance wavelength and increase SPR sensitivity. The coupling strength of metallic nanowire array and metal film also impacts resonance wavelength, which can be used to adjust SPR range but have little effect on its sensitivity. The results are confirmed using a dipole coupling resonance model of metallic nanowire. We demonstrated that this nanostructured hybrid structure can be used for high sensitivity SPR monitoring in a large spectral range, which is important for advanced SPR measurement including fiber-optic SPR sensing technology.

Transmissive color filtering using plasmonic multilayer structure

A transmission type plasmonic multilayer filter is theoretically investigated using three-dimensional rigorous coupled wave analysis (RCWA) method. The design rule of the resonance properties associated with the weakly localized surface plasmon modes in metal/insulator/metal waveguide arrays is discussed. The optical performances with respect to the geometrical parameters of the plasmonic structure are evaluated. Through manipulating the geometric parameters of the metal/insulator/metal waveguide, the optical properties of the filter can be engineered.

Immobilization of Gold Nanoparticles on Aluminum Oxide Nanoporous Structure for Highly Sensitive Plasmonic Sensing

In this work, we investigate the optical properties of a nanostructure design with plasmonic gold nanoparticles (AuNPs) and photonic thin-film multilayers of aluminum oxide on an aluminum film. An aluminum oxide nanoporous surface fabricated by the two-step anodizing method is treated with cationic poly(allyl amine) to fix AuNPs on the surface. The porous nanostructure partially trapped two nanoparticles, producing a small number of nanoparticle dimers on the substrate surface. The experimental and simulation results show that the plasmonic spectra of these gold nanoparticle dimers (AuNDs) are enhanced by the interference spectra of the Al2O3/Al multilayer. On the basis of the longitudinal localized surface plasmon resonance (LSPR) band of AuNDs, our nanostructure substrate showed a high sensitivity to various solutions with different refractive indices, thus showing promising potential for the to development of a new nanosensor for the label-free monitoring of biomolecular interactions.

An Interference Localized Surface Plasmon Resonance Biosensor Based on the Photonic Structure of Au Nanoparticles and SiO2/Si Multilayers

This paper presents the experimental and simulation analysis of an original nanostructure design constructed with plasmonic gold nanoparticles and photonic thin-film multilayers of silicon dioxide (500 nm in thickness) and silicon on a substrate. Our nanostructure substrate showed a high sensitivity for various refractive index RI solutions and a prominent capacity for functionalizing alkanethiol molecules on the gold surface and demonstrates great potential in the development of a microfluidic-based biosensor for monitoring biotin-avidin interactions in real-time.

Transmission Enhancement through Single Slit Embedded in Plasmonic Multilayer Structure

The transmission properties of a plasmonic multilayer structure with a defect, which can be a nanoslit, were investigated. The transmission spectrum through the slit embedded in the plasmonic multilayer structure presents a Fano-like shape at a transmission peak of 580 nm. The enhanced transmission is due to the localized surface plasmon resonant within the cavity of the plasmonic multilayer. The increased transmission factor has a maximum of 5.5 and it also performs loose angle tolerances of 10 and 20° for 1 and 3 dB losses, respectively.