Imaging of Surfaces by Concurrent Surface Plasmon Resonance and Surface Plasmon Resonance-Enhanced Fluorescence

Surface plasmon resonance imaging and surface plasmon induced fluorescent are sensitive tools for surface analysis. However, existing instruments in this area have provided limited capability for concurrent detection, and may be large and expensive. We demonstrate a highly cost-effective system capable of concurrent surface plasmon resonance microscopy (SPRM) and surface plasmon resonance-enhanced fluorescence (SPRF) imaging, allowing for simultaneous monitoring of reflectivity and fluorescence from discrete spatial regions. The instrument allows for high performance imaging and quantitative measurements with surface plasmon resonance, and surface plasmon induced fluorescence, with inexpensive off-the-shelf components.     

Coupling Behaviors of Surface Plasmon Polariton and Localized Surface Plasmon with an InGaN/GaN Quantum Well

Plasmonics - Surface plasmon (SP) coupling behaviors of an InGaN/GaN quantum well (QW) with surface plasmon polariton (SPP) induced on a smooth Ag-film/GaN interface and localized surface plasmon...     

Numerical Simulation of Extinction Spectra of Plasmonically Coupled Nanospheres Using Discrete Dipole Approximation: Influence of Compositional Asymmetry

We demonstrate plasmon coupling phenomenon between equivalent (homodimer) and non-equivalent (heterodimer) spherical shape noble metal nanoparticle (Ag, Au and Al). A systematic comparison of surface plasmon resonance (SPR) and extinction properties of various configurations (monomer, homodimer and heterodimer) has been investigated to observe the effect of compositional asymmetry. Numerical simulation has been done by using discrete dipole approximation method to study the optical properties of plasmonically coupled metal nanoparticles (MNPs). Plasmon coupling between similar nanoparticles allows only higher wavelength bonding plasmon mode while both the plasmon modes lower wavelength antibonding mode as well as higher wavelength bonding mode in the case of heterodimer. Au monomer of radius 50 nm shows resonance peak at 518 nm while plasmon coupling between Au-Au homodimer results in a spectral red shift around 609 nm. Au-Ag plasmonic heterodimer (radius 50 nm) reveals two resonant modes corresponding to higher energy antibonding mode (422 nm) as well as lower energy bonding mode (533 nm). Further, we have shown that interparticle edge-to-edge separation is the most significant parameter affecting the surface plasmon resonances of MNPs. As the inter particle separation decreases, resonance wavelength shows red spectral shift which is maximum for the touching condition. It is shown that plasmon coupling is a reliable strategy to tune the SPR.

     

Remote Excited Raman Optical Activity of Adenine Along Ag Plasmonic Waveguide

We report the remote excited Raman optical activity (ROA) of adenine along Ag plasmonic waveguide. First, the surface plasmons that propagate along Ag nanowire is demonstrated experimentally. Second, the Raman spectra of adenine are measured experimentally. Third, the remote exited ROA by plasmonic waveguide are measured and compared. It is found that the plasmon chirality strongly influenced the molecular ORA by the local surface plasmon and remote plasmon waveguide. The plasmon chirality of nanostructures and the chirality plasmon waveguide should be considered in the experiments for the local and remote measurement.     

Dispersion and Damping of Gold Surface Plasmon

High-resolution electron energy loss spectroscopy was used to investigate the surface plasmon dispersion in (111)-oriented Au films grown on Cu(111). The measured dispersion of the plasmon mode was positive, as found for Ag. The centroid of the induced charge associated to the plasmon field lies well inside the jellium edge. The damping relation of the Au surface plasmon presented a critical wave vector of 0.11 Å^?1. For higher values of the parallel momentum transfer, the line width of Au surface plasmon considerably increased as a consequence of the opening of a new decay channel via single-particle transitions.     

Lifetime of Enhanced Graphene Surface Plasmon and Superstrate Sensitivity

Plasmonics - We investigated the field enhancement and lifetime of tuning surface plasmon in zero-thickness nanostructured graphene patches. The graphene surface plasmon (GSP) resonance mechanism...     

Plasmon Polariton Imaging Characteristics of Near-Field Optical Fiber Probes

The influence of different near-field optical (near-field scanning optical microscopy) probes on the imaging of surface plasmon polaritons propagating on thin metal films is investigated. Metal-coated fiber probes exhibit a suppression of the measured plasmon signal close to the metal film surface and increased local scattering of the plasmon field. Purely dielectric fiber probes are shown to be largely free of these effects.     

Sensitivity Enhanced by MoS2–Graphene Hybrid Structure in Guided-Wave Surface Plasmon Resonance Biosensor

Plasmonics - Compared with surface plasmon resonance (SPR) biosensor, guided-wave surface plasmon resonance (GWSPR) biosensor has a higher sensitivity. In order to further enhance the sensitivity...     

Liquid Crystal-Based Surface Plasmon Resonance Biosensor

Plasmonics - Surface plasmon resonance has many applications in designing biosensors. In this paper, an easy fabrication liquid crystal-based surface plasmon resonance (LC-SPR) biosensor is...     

Novel Dielectric-Loaded Plasmonic Waveguide for Tight-Confined Hybrid Plasmon Mode

In this paper, a novel metal-dielectric waveguide structure is proposed to support hybrid long range surface plasmon polaritons (LRSPPs) with a highly confined mode field. The simulation results showed that our proposed structure has better mode confinement and propagation length compared to that of conventional dielectric-loaded surface plasmon polaritons (DLSPPs) waveguides. This structure offers greater flexibility for the design of surface plasmon polaritons (SPPs) waveguides by altering the trade-off between mode confinement and propagation length. The proposed structure has significant potential for application in highly integrated photonic circuits.     

Characterization of a Wnt-binding site of the WIF-domain of Wnt inhibitory factor-1

A Wnt-binding site of the WIF-domain of Wnt inhibitory factor-1 was localized by structure-guided arginine-scanning mutagenesis in combination with surface plasmon resonance assays. Our observation that substitution of some residues of WIF resulted in an increased affinity for Wnt5a, but decreased affinity for Wnt3a, suggests that these residues may define the specificity spectrum of WIF for Wnts. These results hold promise for a more specific targeting of Wnt family members with WIF variants in various forms of cancer.

Structured summary of protein interactions

WIFbinds to Wnt7a by surface plasmon resonance (View Interaction)WIFbinds to Wnt4 by surface plasmon resonance (View Interaction)WIF and Wnt3aphysically interact by competition binding (View Interaction 1, 2, 3, 4,5, 6)WIFbinds to Wnt9b by surface plasmon resonance (View Interaction)WIFbinds to Wnt5a by surface plasmon resonance (View Interaction)WIFbinds to Wnt11 by surface plasmon resonance (View Interaction)WIFbinds to Wnt3a by surface plasmon resonance (View Interaction)Wnt-5a and WIFphysically interact by competition binding (View Interaction 1,2, 3, 4, 5, 6)     

Evolutionary features of chondriome divergence in Triticum (wheat) and Aegilops shown by RFLP analysis of mitochondrial DNAs

The first comprehensive analysis was made of restriction fragment length polymorphism (RFLP) of the mitochondrial (mt) DNA of two related genera, Triticum (wheat) and Aegilops. This led to clarification of the nature of mtDNA variability and the inference of the phylogeny of the mitochondrial genomes (=chondriome). Forty-six alloplasmic lines and one euplasmic line of common wheat (2n = 42, genomes AABBDD) carrying plasmons (cytoplasmic genomes) of 47 accessions belonging to 33 species were used. This consisted of nearly all the Triticum and Aegilops species. RFLP analysis, carried out with seven mitochondrial gene probes (7.0 kb in total) in combination with three restriction endonucleases, found marked variation: Of the 168 bands detected, 165 were variable (98.2%), indicative that there is extremely high mtDNA variability in these genera. This high variability is attributed to the variation present in the intergenic regions. Most of the variation was between chondriomes of different plasmon types; only 8 bands (4.8%) between those of the same plasmon types were variable, evidence of clear chondriome divergence between different plasmon types. The first comprehensive phylogenetic trees of the chondriome were constructed on the basis of genetic distances. All but 1 of the polyploids had chondriomes closely related to those of 1 putative parent, indicative of uniparental chondriome transmission at the time of polyploid formation. The chondriome showed parallel evolutionary divergence to the plastome (chloroplast genome). Use of a minimum set of 3 mtDNA probe-enzyme combinations is proposed for tentative plasmon type identification and the screening of new plasmon types in those genera. Received: 20 March 1999 / Accepted: 22 June 1999     

Tuning the Fano Resonance Between Localized and Propagating Surface Plasmon Resonances for Refractive Index Sensing Applications

Localized and propagating surface plasmon resonances are known to show very pronounced interactions if they are simultaneously excited in the same nanostructure. Here, we study the Fano interference that occurs between localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (SPP) modes by means of phase-sensitive spectroscopic ellipsometry. The sample structures consist of periodic gratings of gold nanodisks on top of a continuous gold layer and a thin dielectric spacer, in which the structural dimensions were tuned in such a way that the dipolar LSPR mode and the propagating SPP modes are excited in the same spectral region. We observe pronounced anti-crossing and strongly asymmetric line shapes when both modes move to each other’s vicinity, accompanied of largely increased phase differences between the respective plasmon resonances. Moreover, we show that the anti-crossing can be exploited to increase the refractive index sensitivity of the localized modes dramatically, which result in largely increased values for the figure-of-merit which reaches values between 24 and 58 for the respective plasmon modes.     

Long-Range Surface Plasmon Supported by Asymmetric Bimetallic Structure

With this study, we prove that an asymmetric bimetallic structure can support long-range surface plasmon (LRSP) and propose a procedure for its optimization. By applying different criteria we prove that the plasmon which is supported by the structure is indeed LRSP. Unlike all known asymmetric structures supporting LRSP, our structure provides prism excitation and can be used as a biochip for biosensing. Moreover, we show that the structure supports a plasmon with the same propagation constant as LRSP and which is excited at the interface of metal and buffer. This plasmon can be used as a reference channel providing information for the temperature of the structure.     

Plasmonic and Energy Studies of Ag Nanoparticles in Silica-Titania Hosts

The present work reports an investigation of surface plasmon resonance (SPR) of silver nanoparticles in SiO₂–TiO₂ hosts. The surface plasmon resonance of silver nanoparticles was observed in the wavelength range 300–400 nm. Numerical calculation of SPR of silver nanoparticles with spherical morphology was done on the basis of discrete dipole approximation (DDA) method. The observed fluorescence spectrum fits well with the theoretically calculated one. The luminescence enhancement is attributed to the strong local electric field which increases the exciting and emitting photons coupled to SPR. An effort has been made to study the surface plasmon mediated excitation energy transfer (EET) between two spherical metal nanoparticles. The van der Waals (vdW) energy between plasmonic silver nanoparticles in the present hosts has been estimated.     

Quantized plasmon quenching dips nanospectroscopy via plasmon resonance energy transfer

We observed quantized plasmon quenching dips in resonant Rayleigh scattering spectra by plasmon resonance energy transfer (PRET) from a single nanoplasmonic particle to adsorbed biomolecules. This label-free biomolecular absorption nanospectroscopic method has ultrahigh molecular sensitivity.     

Collective Electronic Excitations in Thin Ag Films on Ni(111)

The collective electronic excitations in thin Ag films deposited onto the Ni(111) surface were studied by high-resolution electron energy loss spectroscopy. A broad loss peak at 7.7 eV was assigned to the Ag multipole plasmon, in excellent agreement with calculations based on s-d polarization model. Ag multipole plasmon was excited only at grazing incidence. Furthermore, a strong dependence on the impinging energy exists. Multipole plasmon could be measured only for a very strict range of primary electron beam energies and it was excited by electrons scattered at a reflection plane located just underneath the jellium edge. Such mode was found to be dramatically more sensible to the state of the surface with respect to ordinary surface plasmon. Moreover, we report experimental evidence of interference effects in surface plasmon excitation.     

Localized Surface Plasmon Resonance and Refractive Index Sensitivity of Metal–Dielectric–Metal Multilayered Nanostructures

The localized surface plasmon resonances of multilayered nanostructures are studied using finite difference time domain simulations and plasmon hybridization method. Concentric metal–dielectric–metal (MDM) structure with metal core and nanoshell separated by a thin dielectric layer exhibits a strong coupling between the core and nanoshell plasmon resonance modes. The coupled resonance mode wavelengths show dependence on the dielectric layer thickness and composition of core and outer layer metal. The aluminum-based MDM structures show lower plasmon wavelength compared with Ag- and Au-based MDM nanostructures. The calculated refractive index sensitivity (RIS) factor is in the order Ag–Air–Ag>Au–Air–Au>Al–Air–Al for monometallic multilayered nanostructures. Bimetallic multilayered nanostructures support strong and tunable plasmon resonance wavelengths as well as high RIS factor of 510 nm/refractive index unit (RIU) and 470 nm/RIU for Al–Air–Au and Ag-Air-Au, respectively. The MDM structures not only exhibit higher index sensitivity but also cover a wide ultraviolet–near-infrared wavelengths, making these structures very promising for index sensing, biomolecule sensing, and surface-enhanced Raman spectroscopy.     

The Effect of Inserted Gold Nanosphere on the Second Harmonic Generation (SHG) Enhancement Factor of Three-Layered Dielectric-Gold Nanoshell

The tunable second harmonic generation (SHG) enhancement factor of gold-dielectric-gold three-layered nanoshells has been theoretically studied using the theory of quasi-static electrodynamics and plasmon hybridization. Because of the local surface plasmon resonance (LSPR)-induced local field effect, the SHG response corresponding to both fundamental frequency and second harmonic has been greatly enhanced. By changing the geometry parameters and local dielectric environment of the three-layered nanostructure, the intensity and shift of the SHG factor peaks could be fine tuned. As the radius of the inner gold sphere is increased, both the fundamental and the second harmonic SHG peaks from the anti-symmetric coupling between the outer bonding shell plasmon and the inner sphere plasmon decrease, whereas the SHG peaks from the symmetric coupling between the outer shell and the inner sphere get intense. These radius-dependent intensity changes of the SHG peaks also depend on the dielectric constant of the separate layer and outer surrounding. Thus, the number of SHG peak could be tuned from two to four. Furthermore, the wavelength gaps between the SHG peaks corresponding to anti-symmetric and symmetric coupling could be greatly reduced by increasing the thickness of the outer gold shell. Therefore, the nonmonotonous intensity change could be observed because of the switching of the SHG peaks. The corresponding physical origin has been illuminated by analyzing the plasmon hybridization and the polarization fields in the nanostructure.