Surface Plasmon Coupling Research Articles

High-performance UV surface photodetector based on plasmonic Ni nanoparticles-decorated hexagonal-faceted ZnO nanorod arrays architecture

We report the photoresponse performance of plasmonic nickel (Ni) nanoparticles (NPs)-decorated ZnO NR arrays-based ultraviolet (UV) surface photodetectors. The ZnO NR arrays were grown on the Si substrate by the facile hydrothermal method, followed by Ni NP decoration on the surface by pulsed laser deposition (PLD) technique. Raman analyses reveal that the grown ZnO NR arrays are in hexagonal wurtzite structure. The field emission scanning electron microscopy (FE-SEM) shows that the grown ZnO NR arrays are vertically aligned, hexagonal faceted, and uniformly distributed on the Si substrate. The 14-fold enhancement in the UV emission upon Ni NP decoration implies the near-field coupling of surface plasmons (SPs) of Ni NPs with the excitons of ZnO NRs. The linear increase in current with the applied voltage indicates good Ohmic contacts between the ZnO NR arrays and the Ag electrodes. The transient photo-response measurements were performed for every twenty seconds (20 s) ON/OFF time and for nine cycles to study its response speed, stability, and repeatability of the photodetectors. The improved photo-response of the Ni NP-decorated ZnO NR arrays is attributed to the near-field coupling of Ni NPs with the underlying ZnO NRs. The decoration of plasmonic Ni NPs provides better optical pathway for the incident light and transfers its hot electrons to the conduction band of ZnO NR arrays gives rise the improved photoresponse.

Super-Planckian Radiative Heat Transfer between Macroscale Surfaces with Vacuum Gaps Down to 190 nm Directly Created by SU-8 Posts and Characterized by Capacitance Method

In this work we experimentally demonstrated the near-field thermal radiation enhancement over the blackbody limit by 11 times between highly doped silicon chips with 1x1 cm2 size at a vacuum gap distance of 190 nm under a temperature difference of 74.7 K above room temperature. SU-8 polymer posts, which significantly reduced the conduction less than 6% of the total heat transfer due to its low thermal conductivity, were carefully fabricated with different heights to directly create vacuum gaps from 507 nm down to 190 nm precisely determined in-situ by capacitance measurement. Experimental results were validated by theoretical calculations based on fluctuational electrodynamics, which revealed the enhancement mechanism mainly as coupled surface plasmon polariton. The experimental method developed here will facilitate the potential applications of near-field radiative devices made of electrically conductive materials like metals, graphene, and transparent conductive oxide besides heavily doped semiconductors for thermal energy conversion, radiative thermal rectification, and radiative heat modulation.

Extraordinary optical transmission through titanium nitride-coated microsphere lattice

Titanium nitride (TiN), one candidate as an alternative plasmonic material, is deposited by the sputtering method on top of a self-assembled polystyrene microsphere lattice. The optical transmission spectra of the TiN-coated microsphere lattice reveal a transmission pass-band attributed to the extraordinary optical transmission phenomenon, known from subwavelength hole arrays in metal films. Simulations by finite element method show the presence of a hybrid mode resulting from coupling of surface plasmons on the TiN film to photonic guided resonance modes in the dielectric microsphere lattice. The crucial role of the microspheres in the transmission process is also evidenced by dedicated simulations. Such hybrid colloidal photonic-plasmonic crystals based on TiN are promising for future plasmonic applications requiring the thermo-mechanical stability of refractory ceramics complemented by a plasmonic efficiency similar to that of gold, but also for extending the range of current applications beyond the use of the classical noble metals gold and silver.

Surface Plasmon Coupling with Radiating Dipole for Enhancing the Emission Efficiency and Light Extraction of a Deep Ultraviolet Light Emitting Diode

In this paper, we numerically investigated the emission characteristics of surface plasmon (SP)-enhanced deep ultraviolet light emitting diode (DUV-LED) by employing Al/Al2O3 core-shell nanoparticle(NP) structure on the p-GaN contact layer by utilizing finite-difference time-domain (FDTD) method. The results suggest that normalized dipole power of TE (TM) polarization is enhanced (inhibited) in the DUV range by coupling with in-plane substrate localized surface plasmon (LSP) mode from Al/Al2O3 core-shell nanoparticle (NP). It is found that normalized upward extraction power for both polarizations can also be significantly increased by scattering effect when photons and excitons coupling with in-plane air LSP mode induced on the NP; thus, the light extraction efficiency (LEE) can be substantially enhanced. The depth d between quantum well (QW) and NP and NP size have a remarkable influence on LSP resonance wavelength. Through careful regulation of NP size and depth d, the emission characteristics in DUV range (240–280 nm) exhibit a considerable amelioration.

Analysis of Coupled Surface Plasmon in LHM Mediated Dielectric Gap Multilayer Structure

The purpose of this work is to investigate theoretically the characteristics of confined electromagnetic modes propagating along the interfaces of a multilayer device. This one dimensional (ID) sensor is formed by stacking a left-handed material (LHM) layer between a SiCt2-glass prism and a dielectric gap layer in contact with gold (Au). The results indicate that the total thickness of the LHM layer and dielectric gap, in optimum conditions, give the ability of tuning significantly the characteristics of the resonant modes correlated to surface plasmons (SPs) propagation along the interfaces of the designed device. By considering two arrangements between LHM and Au, two opposite resonant behaviors observed in p-reflectance spectra are analyzed in the angular interrogation mode and discussed thoroughly.

Emission behaviors of colloidal quantum dots linked onto synthesized metal nanoparticles

With two different residual surfactants, four different metal nanoparticles (NPs), including two Au NPs and two Ag NPs are synthesized for linking with red-emitting CdZnSeS/ZnS colloidal quantum dots (QDs) to enhance QD emission efficiency. Those metal NPs are first connected with amino polyethylene glycol thiol of different molecular weights to avoid aggregation and make them positively charged. They can attract negatively charged QDs for inducing surface plasmon (SP) coupling such that either QD absorption or emission and hence overall color conversion efficiency can be enhanced. The enhancement of QD emission efficiency is evaluated through the comparison of time-resolved photoluminescence behaviors under different QD linkage conditions. Such results are confirmed by the measurement of the emission quantum efficiency of QD. It is found that by linking QDs onto Ag NPs, the QD emission efficiency is more enhanced, when compared with Au NPs. Also, depending on the synthesis process, the residual surfactant of citrate leads to a relatively large increment in QD emission efficiency, when compared to the surfactant of cetrimonium chloride. A more enhanced QD emission efficiency is caused by a higher QD linkage capability and a stronger SP coupling effect.

Surface plasmon resonance imaging coupled to on-chip mass spectrometry: a new tool to probe protein-GAG interactions.

A biosensor device for the detection and characterization of protein-glycosaminoglycan interactions is being actively sought and constitutes the key to identifying specific carbohydrate ligands, an important issue in glycoscience. Mass spectrometry (MS) hyphenated methods are promising approaches for carbohydrate enrichment and subsequent structural characterization. In the study herein, we report the analysis of interactions between the glycosaminoglycans (GAGs) heparin (HP) and heparan sulfate (HS) and various cytokines by coupling surface plasmon resonance imaging (SPRi) for thermodynamic analysis method and MALDI-TOF MS for structural determination. To do so, we developed an SPR biochip in a microarray format and functionalized it with a self-assembled monolayer of short poly(ethylene oxide) chains for grafting the human cytokines stromal cell-derived factor-1 (SDF-1α), monocyte chemotactic protein-1 (MCP-1), and interferon-γ. The thermodynamic parameters of the interactions between these cytokines and unfractionated HP/HS and derived oligosaccharides were successively determined using SPRi monitoring, and the identification of the captured carbohydrates was carried out directly on the biochip surface using MALDI-TOF MS, revealing cytokine preferential affinity for GAGs. The MS identification was enhanced by on-chip digestion of the cytokine-bound GAGs with heparinase, leading to the detection of oligosaccharides likely involved in the binding sequence of GAG ligands. Although several carbohydrate array-based assays have been reported, this study is the first report of the successful analysis of protein-GAG interactions using SPRi-MS coupling.

Controllable "Clicked-to-Assembled" Plasmonic Core-Satellite Nanostructures and Its Surface-Enhanced Fluorescence in Living Cells.

The assembly of noble-metal core–satellite (CS) nanostructures is an appealing means to control their plasmonic properties for their applications such as surface-enhanced fluorescence or Raman scattering. However, till now there is a lack of some rapid or convenient methods to construct stable CS nanostructures. Here, we proposed a “clicked-to-assembly” strategy based on the fast and specific “click chemistry” reaction between trans-cyclooctene (TCO) and 1,2,4,5-tetrazine (Tz). The CS nanostructures were constructed within 8 min by simple mixing of TCO- or Tz-modified nanoparticles (TCO-NPs or Tz-NPs) without any catalysts or heating required. Transmission electron microscopy experiments show that the constructed CS nanostructures are uniform, and particularly the number of “satellite” nanoparticles in the core surface is controllable by simply adjusting the feeding ratio of TCO-NPs or Tz-NPs in the reaction. The strong surface plasmon coupling effect (SPCE) was observed in these CS nanostructures, which was dependent on the coverage degree, size and composition of the satellite, and core NPs. The nanostructures with tuned surface plasmon resonance (SPR) effect were tried for the surface-enhanced fluorescence in living cells. Such well-defined CS nanostructures could potentially serve as efficient SPR-enhanced fluorescent probes as diagnostics or biomedical imaging agents in nanomedicine.

Thermo-optic Aided Tunability of Sr0.6Ba0.4Nb2O6 Thin Film-based Electro-optic Modulator Using Waveguide Coupled SPR Modes

Present article demonstrates the effective tuning of thermo-optic (TO) properties with the Electro-Optic (EO) modulation characteristics of SBN60 thin films utilizing Waveguide coupled surface plasmon resonance (WCSPR) technique. Electro-optic (EO) coefficient (r) was in turn tuned from a value of 594 pm/V to 621 pm/V with increasing ambient temperature from 296 to 373 K. Tunable percent modulation index varying from 24 to 55% was obtained with increasing ambient temperature at a fixed applied electric field. The obtained results clearly illustrate an efficient thermally tunable EO modulator based on SBN thin film utilizing a simplistic approach with $$ {\left.\kern0em \left(\frac{\partial n}{\partial T}\right)\right|}_{E=0}=88.3\times {10}^{-4}{K}^{-1} $$.

Using lactosylated cysteine functionalized gold nanoparticles as colorimetric sensing probes for rapid detection of thericin B chain.

A new colorimetric method that can be used to rapidly detect toxic ricin is demonstrated. Lactosylated cysteine-functionalized gold nanoparticles (Au@LACY NPs) were prepared by a one-pot reaction and employed as optical probes for determination of ricin B chain. It is found that the Au@LACY NPs undergoaggregation in the presence of ricin B chain. This leads to surface plasmon coupling effects of the particles and a color change from red to blue, with absorption maxima at 519 and 670nm, respectively. The feasibility of using the current approach for quantitative analysis of ricin B chain is also demonstrated. The calibration plot is generated by plotting the ratio of the absorbance at the wavelength of 634 to 518nm versus the concentration of thericin B chain. The spectrophotometric method has a ~29 pM (~ 0.91ng·mL-1) detection limit, and the sample with the concentration of ~ 400 pM (~ 13ng·mL-1) can be detected visually. Graphical abstractSchematic representation of using lactosylated cysteine capped gold nanoparticles (Au@LACY NPs) as colorimetric probes for the ricin B chainthrough surface plasmon coupling effects. Sample solution turns from red to blue in the presence of ricin Bchain.

Color conversion efficiency enhancement of colloidal quantum dot through its linkage with synthesized metal nanoparticle on a blue light-emitting diode.

Four surface-modified and, hence, positively charged metal nanoparticles (NPs) of different localized surface plasmon (LSP) resonance wavelengths are synthesized for linking with negatively charged, red-emitting colloidal CdZnSeS/ZnS quantum dots (QDs) on the top surface of a blue-emitting InGaN/GaN quantum well (QW) light-emitting diode (LED) through electro-static force. The metal NP-QD linkage leads to a short distance between them for producing their strong surface plasmon (SP) coupling, such that QD absorption and emission can be enhanced. Meanwhile, the small p-GaN thickness in the LED results in strong SP coupling between the LSP resonance of metal NP and the QWs of the LED, leading to enhanced QW emission and, hence, stronger QD excitation. All those factors together result in the increase of the color conversion efficiency of the QD.

Spectral Shifting in Extraordinary Optical Transmission by Polarization-Dependent Surface Plasmon Coupling

Nanoapertures in a metallic film exhibit extraordinary optical transmission (EOT) owing to the surface plasmon resonance. Their transmission properties are known to be dependent on the structural parameters of the nanoapertures. In addition, the polarization of light has also a crucial influence on the transmission spectrum. In this study, we numerically found that the polarization state is a sensitive parameter in plasmonic EOT only when the gap size between triangular nanoapertures is less than ~ 20 nm. For a polarization of the light perpendicular to the axis between the nanoapertures, the optical transmission spectrum is nonlinearly redshifted with decreasing gap size. This spectral shifting of the transmission has potential applications for active optical filters, which can be manipulated by the polarization of light or by adjusting the gap size.

A three-dimensional frequency selective structure based on the modes coupling of spoof surface plasmon and waveguide transmission

A three-dimensional frequency selective structure (3D FSS) was proposed by applying the spoof surface plasmon (SSP) structures into periodic waveguides, which realizes an enhanced broadband transmission in low frequencies, below the cut-off frequency of periodic waveguides. The transmission characteristics of SSP structures and periodic waveguides as well as their coupling modes are investigated by simulation and experiment method. According to our analysis, the pass-band of this 3D FSS can be customized through changing the values of structure parameters and it also has a good angular stability. In addition, this paper also provides a simple assembly plan for sample preparation. This proposal may be useful for improving filtering performances and gives an effective approach for designing 3D FSSs.

Distance-dependent plasmon-enhanced electrochemiluminescence biosensor based on MoS2 nanosheets

Nonmetallic plasmonic MoS2 nanosheets were synthesized by hydrothermal top-down method. MoS2 nanosheets had shown strong surface plasmon coupling (SPC) light absorption in the visible and near-infrared region. Herein, the nonmetallic plasmonic MoS2 nanosheets were employed to enhance the electrochemiluminescence (ECL) signal of sulfur doped boron nitrogen QDs (S-BN QDs) in this work. It is important to regulate the distance between ECL luminophore and plasmonic nanoparticles. On one hand, too closed distance can cause energy or electron transfer, which could quench the ECL intensity of nano-luminophore. On the other hand, plasmonic nanostructure cannot significantly affect the luminescence in the far distance. Therefore, we discussed the distance-dependent plasmon-enhanced ECL in detail with different length DNA chains. Furthermore, we constructed a hybridization chain reaction (HCR) amplification ECL sensing mode with the SPC-ECL strategy. The proposed DNA sensor can quantify hepatitis C virus (HCV) gene from 0.5 pmoL/L to 1 nmoL/L with a limit of detection (LOD) of 0.17 pmoL/L.

Colossal Enhancement of Near-Field Thermal Radiation Across Hundreds of Nanometers between Millimeter-Scale Plates through Surface Plasmon and Phonon Polaritons Coupling.

Coupling modes between surface plasmon polaritons (SPPs) and surface phonon polaritons (SPhPs) play a vital role in enhancing near-field thermal radiation but are relatively unexplored, and no experimental result is available. Here, we consider the NFTR enhancement between two identical graphene-covered SiO2 heterostructures with millimeter-scale surface area and report an experimentally record-breaking ∼64-fold enhancement compared to blackbody (BB) limit at a gap distance of 170 nm. The energy transmission coefficient and radiation spectra show that the physical mechanism behind the colossal enhancement is the coupling between the surface plasmon and phonon polaritons.

The role of surface depletion layer effects on the enhancement of the UV emission in ZnO induced by a nanostructured Al surface coating

The UV enhancement of Al-coated ZnO single crystals with a wide range of carrier densities is systematically studied using depth-resolved cathodoluminescence and photoluminescence as well as valence band X-ray photoemission spectroscopy (VB-XPS). An up to 17-fold enhanced PL UV emission for Al-coated ZnO with the highest carrier density was measured, which falls to a 12-fold increase for the lowest carrier density. Depth-resolved cathodoluminescence measurements confirm that the enhancement is strongest near the Al-ZnO interface consistent with an increased UV emission due to an exciton-localized surface plasmon coupling mechanism. Correlative cathodoluminescence, photoluminescence and VB-XPS studies reveal that a number of additional effects related to the presence of the Al surface coating also contribute to the UV enhancement factor. These include increased UV enhancement due to the formation of a surface depletion layer induced by the Al coating, which also passivates competitive non-radiative surface recombination channels found in uncoated ZnO. Significantly, it was established that the magnitude of the emission enhancement factor can be raised in a controlled way by reducing the thickness of the depletion layer by increasing the carrier density. The contribution of these effects collectively provides an explanation for the large span of enhancement factors reported in the literature.

Tailored Engineering of Bimetallic Plasmonic Au@Ag Core@Shell Nanoparticles.

A distinctive synthetic method for the efficient synthesis of multifunctional bimetallic plasmonic Au@Ag core@shell nanoparticles (NPs) with tunable size, morphology, and localized surface plasmon resonance (LSPR) using Triton X-100/hexanol-1/deionized water/cyclohexane-based water-in-oil (W/O) microemulsion (ME) is described. The W/O ME acted as a “true nanoreactor” for the synthesis of Au@Ag core@shell NPs by providing a confined and controlled environment and suppressing the nucleation, growth, agglomeration, and aggregation of the NPs. High-resolution transmission electron microscopic analysis of the synthesized Au@Ag core@shell NPs revealed an “unusual core@shell” contrast, and the selected area electron diffraction and Moiré patterns showed that Au layers are paralleled to Ag layers, thus indicating the formation of Au@Ag core@shell NPs. Interestingly, the UV–visible spectrum of the Au@Ag core@shell NPs exhibited enthralling plasmonic properties by introducing a high-frequency quadrupolar LSPR mode originated from the isolated Au@Ag NPs along with a low-frequency dipolar LSPR mode originated from the coupled Au@Ag NPs. The effective plasmonic enhancement of the Au@Ag core@shell NPs is attributed to the extreme enhancement of the localized electromagnetic field by coupling of the localized surface plasmons of the Au core and Ag shell. The mechanisms for the nucleation and growth of Au@Ag core@shell NPs in W/O ME have been proposed. A unique electron transfer phenomenon between the Au core and Ag shell is elucidated for better understanding and manipulation of the electronic properties, which evinced the development of Au@Ag core@shell NPs through suppression of the galvanic replacement reaction.

Strong Coupling of Nanoplatelets and Surface Plasmons on a Gold Surface

Nanoplatelets are strongly anisotropic colloidal nanocrystals confined in only one direction. Perfect thickness control and large lateral dimensions enable a large exciton coherence area that exhib...

Ferroelectric [formula omitted] thin film based broadband waveguide coupled surface plasmon electro-optic modulator

Present article demonstrates the enhanced dynamically tuneable EO modulation characteristics in ferroelectric Strontium Barium Niobate SBN,Sr0.6Ba0.4Nb2O6 thin film modulator based on waveguide coupled surface plasmon resonance. The alternating modulating signals having broad frequency range (1 kHz to 10 MHz) with varying amplitude (40kV/cm to 400kV/cm) was applied to estimate the resonance frequency (~1 MHz) using differential modulated intensity interrogation signal. A high value of EO coefficient r=310pm/V leading to Modulation index of 56% was achieved with sensitivity of about 0.33 at resonance possessing a characteristics length of 54.64 μm. These waveguide modes coupled with the plasmon modes paves a way for development of EO modulators utilizing materials with high losses. Therefore, a thin film based WCSPR-EO modulator with compact footprint, low operation voltage, broad operation spectrum and faster speed of modulation was fabricated which paves the way for on-chip optical communications.

Manipulating Light-Matter Interactions in Plasmonic Nanoparticle Lattices.

Rationally assembled nanostructures exhibit distinct physical and chemical properties beyond their individual units. Developments in nanofabrication techniques have enabled the patterning of a wide range of nanomaterial designs over macroscale (>in.2) areas. Periodic metal nanostructures show long-range diffractive interactions when the lattice spacing is close to the wavelength of the incident light. The collective coupling between metal nanoparticles in a lattice introduces sharp and intense plasmonic surface lattice resonances, in contrast to the broad localized resonances from single nanoparticles. Plasmonic nanoparticle lattices exhibit strongly enhanced optical fields within the subwavelength vicinity of the nanoparticle unit cells that are 2 orders of magnitude higher than that of individual units. These intense electromagnetic fields can manipulate nanoscale processes such as photocatalysis, optical spectroscopy, nonlinear optics, and light harvesting. This Account focuses on advances in exciton-plasmon coupling and light-matter interactions with plasmonic nanoparticle lattices. First, we introduce the fundamentals of ultrasharp surface lattice resonances; these resonances arise from the coupling of the localized surface plasmons of a nanoparticle to the diffraction mode from the lattice. Second, we discuss how integrating dye molecules with plasmonic nanoparticle lattices can result in an architecture for nanoscale lasing at room temperature. The lasing emission wavelength can be tuned in real time by adjusting the refractive index environment or varying the lattice spacing. Third, we describe how manipulating either the shape of the unit cell or the lattice geometry can control the lasing emission properties. Low-symmetry plasmonic nanoparticle lattices can show polarization-dependent lasing responses, and multiscale plasmonic superlattices-finite patches of nanoparticles grouped into microscale arrays-can support multiple plasmon resonances for controlled multimodal nanolasing. Fourth, we discuss how the assembly of photoactive emitters on the nanocavity arrays behaves as a hybrid materials system with enhanced exciton-plasmon coupling. Positioning metal-organic framework materials around nanoparticles produces mixed photon modes with strongly enhanced photoluminescence at wavelengths determined by the lattice. Deterministic coupling of quantum emitters in two-dimensional materials to plasmonic lattices leads to preserved single-photon emission and reduced decay lifetimes. Finally, we highlight emerging applications of nanoparticle lattices from compact, fully reconfigurable imaging devices to solid-state emitter structures. Plasmonic nanoparticle lattices are a versatile, scalable platform for tunable flat optics, nontrivial topological photonics, and modified chemical reactivities.