Properties Of Surface Plasmons Research Articles

Quantitative concentration determination of silver nanoparticles prepared by DC high voltage electrochemical method

AbstractSilver nanoparticles (AgNPs) were prepared by DC high voltage electrochemical method using a silver anode. The results showed that, for all prepared samples, depending on the size and shape of their nanoparticles, a well‐defined UV‐Vis peak in aqueous solution induced by the surface Plasmon property of AgNPs was observed at wavelength values in the range of 400‐450 nm. Based on the linear dependence between AgNPs concentration and UV‐Vis absorbance up to 200 ppm with the R value of 0.9989, the concentration of AgNPs can be derived quantitatively. Thus, this study introduced a simple quantitative method to determine the concentration of silver nanoparticles directly, instead of the total ionic silver that other chemical, biological or physical methods usually provided.

Visible light driven photo-degradation of Congo red by TiO2[sbnd]ZnO/Ag: DFT approach on synergetic effect on band gap energy

In this paper, we report the combination of two metal oxides (TiO2ZnO) that allows mixed density of states to reduce band gap energy, facilitating the photo-oxidation of Congo red dye under visible light. For the oxidation, a possible mechanism is proposed after analyzing the intermediates by GC-MS, and it is consistent with Density Functional Theory (DFT). The nanohybrids were characterized comprehensibly by several analytical techniques such as X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS). For the addition of ZnO to TiO2, a dominance of anatase phase was found rather than other phases (rutile or brookite). A broad band (∼550 nm) is observed in UV–Visible spectra for TiO2ZnO/Ag NPs nm because of Surface Plasmon properties of Ag NPs. The band gap energy was calculated for TiO2ZnO/Ag system, and then it has been further studied by DFT in order to show why the convergence of two semiconductors allows a mixed density of states, facilitating the reduction of the energy gap between occupied and unoccupied bands; ultimately, it improves the performance of catalysts under visible light. Significantly, the interaction of crystal planes (0 0 Ī) of TiO2 anatase and (0 0 1) of ZnO crucially plays as an important role for the reduction of energy band-gap. Additionally, TiO2ZnOAg NPs were used recognize Saccharomyces cerevisiae cells by con-focal fluorescence microscope, showing that it develops bright bio-images for the cells; while for TiO2 or ZnO or TiO2ZnO NPs, no fluorescent response was seen within the cells.

Hilbert transform-based single-shot plasmon microscopy.

The localized properties of surface plasmons (SPs) and surface waves can be measured with a modified confocal microscope. An interference signal arises from a locally generated reference close to normal incidence and the beam that forms the surface wave. A spatial light modulator can impose different phase shifts on the part of the incident light to recover the properties of the SP. We report a Hilbert transform method to recover the wavenumber with a single shot. The method is faster and potentially less expensive than previous approaches. The signal-to-noise ratio is equivalent to the phase-stepping method. The signal processing necessary to condition the signal is described.

Connection of Collimation, Asymmetric Beaming, and Independent Transmission-Reflection Processes in Concentric-Groove Gratings Supporting Spoof Surface Plasmons

Transmission through subwavelength apertures enables separation of the incidence half-space and the exit half-space, which leads to that the spatial distribution of the field in the latter is not affected by the distribution in the former. The distribution in the exit half-space is mainly determined by the properties of surface plasmons (SPs) at the exit-side interface. In this paper, for the microwave structures with one-side concentric corrugations around a single annular hole, we demonstrate the possible connections between asymmetric transmission in the beaming regime and collimation of the waves incident at different angles, which can be considered as two sides of the same phenomenon occurring due to the common effect of such a separation and the radiation shaping effect being possible due to the spoof SPs at the corrugated exit interface. Collimation manifests itself in that the waves incident at different angles from a wide range contribute to the single outgoing beam so that a far-zone observer cannot distinguish between the contributions of different angles of arrival. Asymmetry in transmission manifests itself in that the spatial shaping of radiation (beaming) in the exit half-space appears only for one of the two opposite incidence directions. Moreover, even in the structures with the same corrugations on both sides, i.e., without asymmetric transmission, spatial separation of two wave processes, e.g., two symmetric or asymmetric collimation processes, can be obtained for a wide range of nonzero angles of incidence.

A unified approach to Plasmon–Polariton and Brewster mode dynamics in media with interfacial surface-admittance

In this article we develop an ab-initio formulation for the analysis of certain solutions to the macroscopic Maxwell equations in bulk homogeneous materials that are separated by a planar interface that may sustain field-dependent electric currents induced by a surface admittance tensor. Based on Clemmow’s description of complex inhomogeneous plane time-harmonic waves, a systematic procedure is given that yields particular global solutions in terms of solutions to a system of bivariate polynomial and linear eigen-value equations for a set of six complex dimensionless scalars. This algebraic system is amenable to rapid numerical analysis using Maple or Matlab on a laptop. From the resulting solutions, analytic formulae for the electromagnetic fields can be expressed in terms of values for these six scalars and the electromagnetic phenomenological properties of the bulk media and their interface.We show explicitly how general properties of Surface Plasmon–Polariton (SPP) and Brewster modes follow from this unified viewpoint without appeal to any reflections in a Fresnel formulation. In particular we emphasise that endowing the material interface with (in general) anisotropic admittance properties can lead to new global electromagnetic field characteristics offering new possibilities for the control of surface characteristics by using recent advances in the fabrication of meta-materials.We illustrate our results by showing how a mono-layer of graphene in a normal magneto-static field can be used to construct a tunable meta-surface for SPP generation and how a simple conducting Ohmic interface can be used to excite both transverse electric and transverse magnetic Brewster modes as a function of the interface admittance.

Spatiotemporal Imaging of Surface Plasmons Using Two-Color Photoemission Electron Microscopy

Time-resolved photoemission electron microscopy images recorded using a combination of ultrafast 800 nm (red) and 400 nm (blue) pulses track surface plasmon polaritons launched from lithographic patterns etched into silver thin films with joint femtosecond temporal and nanometer spatial resolution. The nondegenerate two-color scheme is found to significantly enhance photoelectron yields relative to single-color approaches. This enables both an enhanced visualization of surface plasmons and a more accurate determination of surface plasmon properties compared to single-color measurements. Power-dependent photoemission yield measurements reveal that the overall signal is linear with respect to blue excitation and slightly nonlinear for analogous red excitation. A numerical model based on wave packet propagation reproduces the experimental results and rigorously establishes that the polarization fields from both laser colors and their conjugate surface plasmons account for the observed photoelectron yield enh...

Collective effect of hybrid Au-Ag nanoparticles and organic-inorganic cathode interfacial layers for high performance polymer solar cell

The cooperative effect of hybrid Au-Ag nanoparticles and organic-inorganic cathode interfacial layers to advance the power conversion efficiency (PCE) of regio regular (rr) P3HT:PCBM based polymer solar cells (PSCs) are systematically demonstrated. In this work initially, two types of plasmonic nanoparticles (NPs), namely, citrate stabilized gold (AuNPs) and silver (AgNPs) were separately synthesized and then physically blend together with three different volume ratio [AuNPs + AgNPs (25:75), AuNPs + AgNPs (50:50) and AuNPs + AgNPs (75:25)]. These three blended NP solutions were then mixed together in the PEDOT:PSS (20 v/v %) hole extraction layer (HEL) to form three new NPs doped HEL and their effect on the rr-P3HT:PCBM based PSCs were systematically analyzed. For dual organic-inorganic cathode interfacial layers, two organic hole blocking materials, BPhen and BCP were used for enhanced charge collection in combination with LiF:Al as conventional cathode electrode. The collective effect of hybrid NPs with the dual cathode interfacial layers was examined with two varying active polymer blends, rr-P3HT:PC61BM and rr-P3HT:PC71BM. It has been found that the PCE increases considerably for both the active blend systems, with PEDOT:PSS + [AuNPs:AgNPs (25:75)] + BCP:LiF:Al as the modified cathode electrode. This is due to suitable electronic energy level matching of BCP:LiF:Al and active blend with the excellent surface plasmon property of the AuNPs:AgNPs (25:75) in the UV–Visible region compared to AuNPs:AgNPs (50:50) and AuNPs:AgNPs (75:25). Devices having configuration PEDOT:PSS + [AuNPs:AgNPs (25:75)] as HEL, rr-P3HT:PC71BM as active blend and BCP:LiF:Al provided PCE, ɳmax = 5.71% with Jsc = 16.44 mA/cm2, Voc = 0.58 V, FF = 60% and device with rr-P3HT:PC61BM as active blend layer was showing as PCE, ɳmax = 5.31% with Jsc = 14.77 mA/cm2, Voc = 0.58 V and FF = 62% with the same PEDOT:PSS + [AuNPs:AgNPs (25:75)] layer and BCP:LiF:Al. These results conclusively described a very simple technique in which the cooperative effect of plasmonic hybrid metals nanoparticles and dual cathode interfacial layers outstandingly enrich the PCE and in general the complete nature of rr-P3HT:PCBM based PSCs.

The Influence of a Finite Size of Spheroids Forming a Chain on the Properties of Surface Plasmons

A plasmon transmission line comprising a chain of metal nanospheroids is considered. It is shown that taking into account a finite size of spheroids leads to a significant change in the transmission characteristics of the chain of spheroids; in particular, the plasmon propagation length decreases dramatically.

Surface plasmon characteristics based on graphene-cavity-coupled waveguide system

We theoretically investigate the localized surface plasmon of graphene in graphene-cavity-coupled waveguide system with using finite-difference time-domain (FDTD) method and the coupled mode theory (CMT). Cavity provides the strong light-matter interaction between graphene and light. And strongly confined radiation can be confined in a thin and finite width graphene. The fermi level of the graphene nanoribbon plays an important role in tuning the graphene surface plasmon. The faint high-order mode of graphene surface plasmon is also observed. The resonant wavelengths of graphene surface plasmon are almost unaffected by the altering of the refractive index of the cavity core, susceptibility of the cavity core and intensity of incident light. This paper can give an insight of the localized surface plasmon properties in graphene system or any other 2D system. And graphene assisted with cavity is an attractive candidate for designing active graphene plasmonic devices or any other 2D plasmonic devices.

Surface plasmons in a semi-bounded massless Dirac plasma

The collective excitation of surface plasmons in a massless Dirac plasma (e.g., graphene) half-space (bounded by air) is investigated using a relativistic quantum fluid model. The unique features of such surface waves are discussed and compared with those in a Fermi plasma. It is found that in contrast to Fermi plasmas, the long-wavelength surface plasmon frequency (ω) in massless Dirac plasmas is explicitly nonclassical, i.e., ω∝1/ħ, where h=2πħ is the Planck's constant. Besides some apparent similarities between the surface plasmon frequencies in massless Dirac plasmas and Fermi plasmas, several notable differences are also found and discussed. Our findings elucidate the properties of surface plasmons that may propagate in degenerate plasmas where the relativistic and quantum effects play a vital role.

Performance of Graphene Plasmonic Antenna in Comparison with Their Counterparts for Low-Terahertz Applications

Graphene has attracted great interest for antenna applications because of its two-dimensional nature and superior electronic properties. Low losses, strong confinement, and high tunability properties of surface plasmon make this material as one of the suited material for terahertz applications. In this paper, we have investigated the surface plasmon polariton properties and plasmonic resonance of the graphene dipole antenna at low-terahertz frequency range and compared its radiation performance with that of carbon nanotube and copper, in order to find the suitability of these materials for THz antenna designing. Surface conductivity and surface impedance of graphene, carbon nanotube, and copper at terahertz band have been studied. The performances of these antennas are analyzed, and it was found that graphene plasmonic antenna better suits for making THz antennas.

Observation of surface plasmon polaritons in 2D electron gas of surface electron accumulation in InN nanostructures

Recently, heavily doped semiconductors have been emerging as an alternative to low-loss plasmonic materials. InN, belonging to the group III nitrides, possesses the unique property of surface electron accumulation (SEA), which provides a 2D electron gas (2DEG) system. In this report, we demonstrated the surface plasmon properties of InN nanoparticles originating from SEA using the real-space mapping of the surface plasmon fields for the first time. The SEA is confirmed by Raman studies, which are further corroborated by photoluminescence and photoemission spectroscopic studies. The frequency of 2DEG corresponding to SEA is found to be in the THz region. The periodic fringes are observed in the near-field scanning optical microscopic images of InN nanostructures. The observed fringes are attributed to the interference of propagated and back-reflected surface plasmon polaritons (SPPs). The observation of SPPs is solely attributed to the 2DEG corresponding to the SEA of InN. In addition, a resonance kind of behavior with the enhancement of the near-field intensity is observed in the near-field images of InN nanostructures. Observation of SPPs indicates that InN with SEA can be a promising THz plasmonic material for light confinement.

MoS2 Quantum Dots@TiO2 Nanotube Arrays: An Extended-Spectrum-Driven Photocatalyst for Solar Hydrogen Evolution.

TiO2 nanotube arrays (TiO2 NTAs) decorated with molybdenum disulfide quantum dots (MoS2 QDs) were synthesized by a facile electrodeposition method and used as a composite photocatalyst. MoS2 QDs/TiO2 NTAs showed enhanced photocatalytic activity compared with pristine TiO2 NTAs for solar light-promoted H2 evolution without adding any sacrificial agents or cocatalysts. The photocatalytic activity was influenced by the amount of MoS2 QDs coated on TiO2 NTAs. The optimal composition showed excellent photocatalytic activity, achieving H2 evolution rates of 31.36, 5.29, and 1.67 μmol cm-2 h-1 corresponding to ultraviolet (UV, λ<420 nm), visible (Vis, λ≥420 nm), and near-infrared (NIR, λ>760) illumination, respectively. The improved photocatalytic activity was attributed to the decreased bandgap and the surface plasmonic properties of MoS2 QDs/TiO2 NTAs, which promoted electron-hole pair separation and the absorption capacity for Vis and NIR light. This study presents a facile approach for fabricating MoS2 QDs/TiO2 NTA heterostructures for efficient photocatalytic H2 evolution, which will facilitate the development of designing new photocatalysts for environment and energy applications.

Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Boron dipyrromethene (BODIPY) molecules with donor-acceptor configurations are of great interests for harvesting and converting solar energy in a solar cell. Au nanoparticles have been applied to enhance solar energy harvesting and conversion efficiency of organic solar cells because of their surface plasmon properties for increasing light absorption cross-section of an organic dye. Electrochemical properties of single BODIPY dyes and plasmonic Au nanoparticles (NPs) are studied using combined optical and electrochemical methods to reveal their structure-function relationship at the nanometer scale. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-doped tin oxide (ITO) surfaces. Dark field scattering (DFS), photoluminescence (PL), and electrogenerated chemiluminescence (ECL) are used to probe local redox reactions of single Au nanoparticles at transparent planar and micro-sized electrode. Our study shows that these optical responses at individual plasmonic NPs are strongly dependent on particle size, and are affected by the local chemical and charge transfer environment of the NPs.

Transport properties of surface plasmons in a nonlinear nanowire coupled to quantum dots with azimuthal angle differences

We investigate single surface-plasmon transport in a nonlinear nanowire strongly coupled to multiple quantum dots with azimuthal angle differences. Exact expressions for the scattering coefficients are obtained by adopting the real-space Hamiltonian and the transfer matrix approach. Fano-like resonance and jiggling behavior in the scattering spectra are exhibited, and a plasmonic switch can be achieved, by adjusting azimuthal angle differences of quantum dots. The periodic transmission and reflection profile is also revealed at specific azimuthal angles. These results show that the azimuthal angle may be utilized as a new handle to control the surface plasmon transport.

Ag/Au Alloy LSPR Engineering by Co‐deposition of RF‐Sputtering and RF‐PECVD

Silver‐Gold alloy/diamond like carbon (Ag‐Au/DLC) nanocomposite films were prepared by co‐deposition of RF‐sputtering and RF‐PECVD on glass substrates by using acetylene gas and silver‐gold target. The deposition process was carried out at room temperature in one minute with the variable parameters of initial pressures and RF powers. X‐ray diffraction analysis demonstrated the formation of Ag/Au alloy nanoparticles with a face‐centered cubic (FCC) structure. Localized surface plasmon and optical properties of Ag‐Au alloy nanoparticles were studied by UV‐visible spectrophotometry which showed that increasing RF power and initial pressure cause a redshift in all samples. Moreover, the effect of RF power and initial pressure on the size and shape of nanoparticles were studied by 2D Atomic force microscopy images. Energy dispersive X‐ray spectroscopy revealed the formation of Ag‐Au/DLC nanoparticles and the percentages of C, Ag, Au and O in all samples. The applied method for Ag/Au alloy preparation is the one step and low‐cost method which makes the samples ready for sensing application.

Theoretical study on surface plasmon properties of gold nanostars

With the rapid development of nanotechnology, the surface plasmon properties of metal nanostructures have become the focus of research. In this paper, a multi-tip gold nanostars (GNSs) structure is designed theoretically, and its surface plasmon properties are simulated by using the finite element method (FEM), which is practical and versatile. Compared with the traditional spherical and triangular plate particles, the results show that the tip structure of the GNSs has a stronger hot spots effect, resulting in greater local field enhancement properties. The relationship between the structure parameters of GNSs and their resonance peaks was also studied. The results indicate that the resonance peaks of GNSs depend strongly on the size, spacing between two GNSs, quantity and refractive index of the GNSs.

Surface plasmon oscillations in a semi-bounded semiconductor plasma

We study the dispersion properties of surface plasmon (SP) oscillations in a semi-bounded semiconductor plasma with the effects of the Coulomb exchange (CE) force associated with the spin polarization of electrons and holes as well as the effects of the Fermi degenerate pressure and the quantum Bohm potential. Starting from a quantum hydrodynamic model coupled to the Poisson equation, we derive the general dispersion relation for surface plasma waves. Previous results in this context are recovered. The dispersion properties of the surface waves are analyzed in some particular cases of interest and the relative influence of the quantum forces on these waves are also studied for a nano-sized GaAs semiconductor plasma. It is found that the CE effects significantly modify the behaviors of the SP waves. The present results are applicable to understand the propagation characteristics of surface waves in solid density plasmas.

Continuous synthesis of hollow silver-palladium nanoparticles for catalytic applications.

Hollow bimetallic nanoparticles exhibit unique surface plasmonic properties, enhanced catalytic activities and high photo-thermal conversion efficiencies amongst other properties, however, their research and further deployment are currently limited by their complicated multi-step syntheses. This paper presents a novel approach for their continuous synthesis with controllable and tuneable sizes and compositions. This robust manufacturing tool, consisting of coiled flow inverter (CFI) reactors connected in series, allows for the first time the temporal and spatial separation of the initial formation of silver seeds and their subsequent galvanic displacement reaction in the presence of a palladium precursor, leading to the full control of both steps separately. We have also demonstrated that coupling the galvanic replacement and co-reduction leads to a great kinetic enhancement of the system leading to a high yield process of hollow bimetallic nanoparticles, directly applicable to other metal combinations.

Simulation and analysis of 2D material (MoS2/MoSe2) based plasmonic sensor for measurement of organic compounds in infrared

A plasmonic sensor with enhanced performance based on chalcogenide (ChG) substrate with 2D nanomaterial (transition metal dichalcogenides: TMDC) and Au layer in NIR regime is proposed for the diagnostics of organic compounds. MoS2 and MoSe2 in their monolayer forms have been considered as the 2D materials. Detailed simulation and analysis of sensing properties of surface plasmons (SPs) supported by Au-MoS2/MoSe2 interface are carried out. The sensing performance is evaluated in terms of the figure of merit (FOM) that takes both sensitivity as well as accuracy of the sensor into account. Further, the effect of the number of MoSe2 and MoS2 layers is investigated. It is concluded that longer wavelength and smaller number of MoS2/MoSe2 (preferably monolayer) exhibit significantly enhanced FOM. Also, the strong chemical and thermal stability of ChG and 2D materials lead to highly steady sensing performance.