Showing papers on "Surface plasmon resonance published in 2007"
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15 May 2007
TL;DR: In this paper, the authors discuss the role of surface plasmon polaritons at metal/insulator interfaces and their application in the propagation of surfaceplasmon waveguides.
Abstract: Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.
7,238 citations
TL;DR: This review describes recent fundamental spectroscopic studies that reveal key relationships governing the LSPR spectral location and its sensitivity to the local environment, including nanoparticle shape and size and introduces a new form of L SPR spectroscopy, involving the coupling between nanoparticle plasmon resonances and adsorbate molecular resonances.
Abstract: Localized surface plasmon resonance (LSPR) spectroscopy of metallic nanoparticles is a powerful technique for chemical and biological sensing experiments. Moreover, the LSPR is responsible for the electromagnetic-field enhancement that leads to surface-enhanced Raman scattering (SERS) and other surface-enhanced spectroscopic processes. This review describes recent fundamental spectroscopic studies that reveal key relationships governing the LSPR spectral location and its sensitivity to the local environment, including nanoparticle shape and size. We also describe studies on the distance dependence of the enhanced electromagnetic field and the relationship between the plasmon resonance and the Raman excitation energy. Lastly, we introduce a new form of LSPR spectroscopy, involving the coupling between nanoparticle plasmon resonances and adsorbate molecular resonances. The results from these fundamental studies guide the design of new sensing experiments, illustrated through applications in which researchers use both LSPR wavelength-shift sensing and SERS to detect molecules of chemical and biological relevance.
5,444 citations
TL;DR: The rates of protein association and dissociation are determined using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein–nanoparticle mixtures, and this method is developed into a systematic methodology to isolate nanoparticle-associated proteins.
Abstract: Due to their small size, nanoparticles have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with living systems. In a biological fluid, proteins associate with nanoparticles, and the amount and presentation of the proteins on the surface of the particles leads to an in vivo response. Proteins compete for the nanoparticle "surface," leading to a protein "corona" that largely defines the biological identity of the particle. Thus, knowledge of rates, affinities, and stoichiometries of protein association with, and dissociation from, nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells. Here we develop approaches to study these parameters and apply them to plasma and simple model systems, albumin and fibrinogen. A series of copolymer nanoparticles are used with variation of size and composition (hydrophobicity). We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles. We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein-nanoparticle mixtures. This method is less perturbing than centrifugation, and is developed into a systematic methodology to isolate nanoparticle-associated proteins. The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size.
2,715 citations
TL;DR: This paper presents a meta-analysis of four-Wave Mixing and its applications in nanofiltration, which shows clear trends in high-performance liquid chromatography and also investigates the role of nano-magnifying lens technology in this process.
Abstract: 12.2.2. Four-Wave Mixing (FWM) 4849 12.2.3. Dye Aggregation 4850 12.2.4. Optoelectronic Nanodevices 4850 12.3. Sensor 4851 12.3.1. Chemical Sensor 4851 12.3.2. Biological Sensor 4851 12.4. Catalysis 4852 13. Conclusion and Perspectives 4852 14. Abbreviations 4853 15. Acknowledgements 4854 16. References 4854 * Corresponding author E-mail: tpal@chem.iitkgp.ernet.in. † Raidighi College. § Indian Institute of Technology. 4797 Chem. Rev. 2007, 107, 4797−4862
2,414 citations
TL;DR: In this paper, the surface plasmon response of metal nanoparticles is studied for different shapes and physical environments, and the modification of these surface plasmons by different surrounding media and the presence of a substrate or other nanoparticles are also discussed.
Abstract: The surface plasmon response of metal nanoparticles is studied for different shapes and physical environments. For polyhedral nanoparticles, the surface plasmon resonances are studied as a function of the number of faces and vertices. The modification of these surface plasmons by different surrounding media and the presence of a substrate or other nanoparticles is also discussed. We found that polyhedral nanoparticles composed with less faces show more surface plasmon resonances, and as the nanoparticle becomes more symmetric, the main surface plasmon resonance is blue-shifted. It is also found that the corners induce more surface plasmons in a wider energy range. In the presence of a substrate, multipolar plasmon resonances are induced, and as the nanoparticle approaches the substrate, such resonances are red-shifted. The interaction among nanoparticles also induces multipolar resonances, but they can be red or blue-shifted depending on the polarization of the external field.
1,574 citations
TL;DR: In this article, the authors investigated the localized surface plasmon resonances (LSPR) in gold nanodisc pairs using microabsorption spectroscopy and electrodynamic simulations.
Abstract: Localized surface plasmon resonances (LSPR) in lithographically fabricated gold (Au) nanodisc pairs are investigated using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, we find that the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. In addition, we find that the decay length is roughly about 0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielectric constant. The near-exponential distance decay and the interesting “universal” scaling behavior of interparticle plasmon coupling can be qualitatively explained on the basis of a dipolar-coupling model as being due to the interplay of two factors: the direct dependence of the single-particle polarizability on the cubic power of the particle dimension and the decay of the plasmonic near-field as the cubic power of the inverse distance. Using this universal scaling behavior, we ...
1,456 citations
TL;DR: In this article, a theoretical description of the many-body dynamical electronic response of solids is presented, which underlines the existence of various collective electronic excitations at metal surfaces.
Abstract: Collective electronic excitations at metal surfaces are well known to play a key role in a wide spectrum of science, ranging from physics and materials science to biology. Here we focus on a theoretical description of the many-body dynamical electronic response of solids, which underlines the existence of various collective electronic excitations at metal surfaces, such as the conventional surface plasmon, multipole plasmons and the recently predicted acoustic surface plasmon. We also review existing calculations, experimental measurements and applications.
1,316 citations
TL;DR: In particular, the amount of generated heat and temperature increase depends on the number of colloidal nanoparticles in a complex and the shape and organization of the nanoparticles as mentioned in this paper, which suggests new possibilities for measuring heat release at the nanoscale.
1,201 citations
TL;DR: In this article, a review of the plasmon resonance (SPR) enhanced optical properties of noble metal nanoparticles is presented, with an emphasis on the recent advances in the utility of these plasmoric properties in molecular-specific imaging and sensing, photo-diagnostics, and selective photothermal therapy.
Abstract: Noble metal, especially gold (Au) and silver (Ag) nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR). In this review, we discuss the SPR-enhanced optical properties of noble metal nanoparticles, with an emphasis on the recent advances in the utility of these plasmonic properties in molecular-specific imaging and sensing, photo-diagnostics, and selective photothermal therapy. The strongly enhanced SPR scattering from Au nanoparticles makes them useful as bright optical tags for molecular-specific biological imaging and detection using simple dark-field optical microscopy. On the other hand, the SPR absorption of the nanoparticles has allowed their use in the selective laser photothermal therapy of cancer. We also discuss the sensitivity of the nanoparticle SPR frequency to the local medium dielectric constant, which has been successfully exploited for the optical sensing of chemical and biological analytes. Plasmon coupling between metal nanoparticle pairs is also discussed, which forms the basis for nanoparticle assembly-based biodiagnostics and the plasmon ruler for dynamic measurement of nanoscale distances in biological systems.
1,157 citations
TL;DR: This work discusses recent advances in the study and use of selectively targeted Au nanospheres in cancer photodiagnostics and photothermal therapy, and the use of Au nanorods and silica-Au core-shell nanoparticles for in vivo cancer detection and therapy.
1,103 citations
TL;DR: It is found that enhancement of the molecular fluorescence by more than a factor of 50 can be achieved for ICG next to a nanoparticle with a large scattering cross section and a plasmon resonance frequency corresponding to the emission frequency of the molecule.
Abstract: Metallic nanoparticles are known to dramatically modify the spontaneous emission of nearby fluorescent molecules and materials. Here we examine the role of the nanoparticle plasmon resonance energy and nanoparticle scattering cross section on the fluorescence enhancement of adjacent indocyanine green (ICG) dye molecules. We find that enhancement of the molecular fluorescence by more than a factor of 50 can be achieved for ICG next to a nanoparticle with a large scattering cross section and a plasmon resonance frequency corresponding to the emission frequency of the molecule.
TL;DR: The localized surface plasmon resonance (LSPR) of oxide-free Cu nanoparticles fabricated by nanosphere lithography is examined by UV−vis extinction spectroscopy and electrodynamics theory.
Abstract: The localized surface plasmon resonance (LSPR) of oxide-free Cu nanoparticles fabricated by nanosphere lithography is examined by UV−vis extinction spectroscopy and electrodynamics theory. The LSPR of the Cu nanoparticles is significantly affected by the presence of copper oxides and the removal of the oxide species yields a dramatic difference in the observed LSPR. From a comparison of the LSPR of Cu, Ag, and Au nanoparticles of similar geometry, we conclude that Cu displays an intense and narrow LSPR peak that is comparable to Ag and Au.
TL;DR: The optical responses of 75-150 nm diameter gold nanorings to changes in local refractive index have been quantified by near-infrared extinction spectroscopy and compared to DDA calculations and an analytical approach.
Abstract: The optical responses of 75−150 nm diameter gold nanorings to changes in local refractive index have been quantified by near-infrared extinction spectroscopy and compared to DDA calculations and an analytical approach. The “bulk” refractive index sensitivities of gold nanorings are substantially (>5 times) larger than those of nanodisks with similar diameters. Nanorings retain a significantly larger sensitivity than nanodisks at the same spectral position, demonstrating a clear shape dependence that may correlate to a systematic difference in the influence of the dielectric substrate. The nanoring bulk refractive index sensitivity scales linearly with plasmon peak position. The spectral sensitivity to thin films of alkanethiols gave a shift of ∼5.2 nm/CH2 unit while bulk sensitivities as high as 880 nm/RIU were observed, the highest such reported sensitivities. Both bulk and thin dielectric film sensitivities correlated well with theory. Real-time label-free monitoring of protein binding via molecular rec...
TL;DR: On average, the brightest fluorescence from dyes attached to metal nanoparticles that have a LSPR scattering peak approximately 40-120 meV higher in energy than the emission peak of the fluorophore is observed.
Abstract: We investigate the fluorescence from dyes coupled to individual DNA-functionalized metal nanoparticles. We use single-particle darkfield scattering and fluorescence microscopy to correlate the fluorescence intensity of the dyes with the localized surface plasmon resonance (LSPR) spectra of the individual metal nanoparticles to which they are attached. For each of three different dyes, we observe a strong correlation between the fluorescence intensity of the dye and the degree of spectral overlap with the plasmon resonance of the nanoparticle. On average, we observe the brightest fluorescence from dyes attached to metal nanoparticles that have a LSPR scattering peak ∼40−120 meV higher in energy than the emission peak of the fluorophore. These results should prove useful for understanding and optimizing metal-enhanced fluorescence.
TL;DR: With a combination of discrete-dipole approximation calculations and single-nanoparticle spectroscopy, the effect of nanostructure aspect ratio and corner sharpness on the frequency of plasmon resonance is explored.
Abstract: Silver nanobars with rectangular side facets and an average aspect ratio of 2.7 have been synthesized by modifying the concentration of bromide added to a polyol synthesis. Subsequent rounding of nanobars transformed them into nanorice. Due to their anisotropy, nanobars and nanorice exhibit two plasmon resonance peaks, scattering light both in the visible and in the near-infrared regions. With a combination of discrete-dipole approximation calculations and single-nanoparticle spectroscopy, we explored the effect of nanostructure aspect ratio and corner sharpness on the frequency of plasmon resonance. Near-field calculations and surface-enhanced Raman scattering measurements on single particles were performed to show how local field enhancement changes with both the wavelength and polarization of incident light.
TL;DR: The spectral tunability of this antenna effect is demonstrated and it is shown that maximum enhancement is achieved when the emission frequency is red-shifted from the surface plasmon resonance of the particle.
Abstract: The fluorescence from a single molecule can be strongly enhanced near a metal nanoparticle acting as an optical antenna. We demonstrate the spectral tunability of this antenna effect and show that maximum enhancement is achieved when the emission frequency is red-shifted from the surface plasmon resonance of the particle. Our experimental results, using individual gold and silver particles excited at different laser-frequencies, are in good agreement with an analytical theory which predicts a different spectral dependence of the radiative and non-radiative decay rates.
TL;DR: This work is an important step toward using silver nanoparticle-oligonucleotide conjugates for a variety of purposes, including molecular diagnostic labels, synthons in programmable materials synthesis approaches, and functional components for nanoelectronic and plasmonic devices.
Abstract: We report a new strategy for preparing silver nanoparticle−oligonucleotide conjugates that are based upon DNA with cyclic disulfide-anchoring groups. These particles are extremely stable and can withstand NaCl concentrations up to 1.0 M. When silver nanoparticles functionalized with complementary sequences are combined, they assemble to form DNA-linked nanoparticle networks. This assembly process is reversible with heating and is associated with a red shifting of the particle surface plasmon resonance and a concomitant color change from yellow to pale red. Analogous to the oligonucleotide-functionalized gold nanoparticles, these particles also exhibit highly cooperative binding properties with extremely sharp melting transitions. This work is an important step toward using silver nanoparticle−oligonucleotide conjugates for a variety of purposes, including molecular diagnostic labels, synthons in programmable materials synthesis approaches, and functional components for nanoelectronic and plasmonic devices.
TL;DR: Commercial SPR microscopes now make it possible to simultaneously monitor binding kinetics on >1300 spots within a protein microarray with a detection limit of approximately 0.3 ng/cm(2), or <50 fg per spot with a time resolution of 1s, and spot-to-spot reproducibility within a few percent.
TL;DR: The photothermal heterodyne imaging method is used to study for the first time the absorption spectra of individual gold nanoparticles with diameters down to 5 nm, and disturbances in the peak energies and homogeneous widths of the single-particle resonances are revealed.
Abstract: The Photothermal Heterodyne Imaging method is used to study for the first time the absorption spectra of individual gold nanoparticles with diameters down to 5 nm. Intrinsic size effects wich result in a broadening of the Surface Plasmon resonance are unambiguously observed. Dispersions in the peak energies and homogeneous widths of the single particle resonances are revealed. The experimental results are analysed within the frame of Mie theory.
TL;DR: In this article, the electromagnetic interaction between Au nanoparticles positioned atop a Si pn junction photodiode and incident electromagnetic plane waves has been performed as a function of wavelength, leading to increased electromagnetic field amplitude within the semiconductor and consequently increased photocurrent response, over a broad range of wavelengths extending upward from the nanoparticle surface plasmon polariton resonance wavelength.
Abstract: Experimental characterization and finite-element numerical simulations of the electromagnetic interaction between Au nanoparticles positioned atop a Si pn junction photodiode and incident electromagnetic plane waves have been performed as a function of wavelength. The presence of the Au nanoparticles is found to lead to increased electromagnetic field amplitude within the semiconductor, and consequently increased photocurrent response, over a broad range of wavelengths extending upward from the nanoparticle surface plasmon polariton resonance wavelength. At shorter wavelengths, a reduction in electromagnetic field amplitude and a corresponding decrease in photocurrent response in the semiconductor are observed. Numerical simulations reveal that these different behaviors are a consequence of a shift in the phase of the nanoparticle polarizability near the surface plasmon polariton wavelength, leading to interference effects within the semiconductor that vary strongly with wavelength. These observations hav...
TL;DR: Electrophoretic mobilities are quantitatively explained by a model based on the Henry formula, providing a theoretical framework for predicting gel mobilities of polymer coated nanoparticles.
Abstract: We demonstrate the separation of gold and silver nanoparticles according to their size and shape by agarose gel electrophoresis after coating them with a charged polymer layer. The separation is monitored optically using the size- and shape-dependent plasmon resonance of noble metal particles and confirmed by transmission electron microscopy (TEM). Electrophoretic mobilities are quantitatively explained by a model based on the Henry formula, providing a theoretical framework for predicting gel mobilities of polymer coated nanoparticles.
01 Jan 2007
TL;DR: SURFACE PLASMONS as discussed by the authors is a well-known NANOPHOTONICS tool for light transmission through perIODICally-strUCTured NANO-APERTURES.
Abstract: SURFACE PLASMON NANOPHOTONICS.- NEAR-FIELD AND FAR-FIELD PROPERTIES OF NANOPARTICLE ARRAYS.- THEORY OF LIGHT TRANSMISSION THROUGH PERIODICALLY STRUCTURED NANO-APERTURES.- DEVELOPMENT AND NEAR-FIELD CHARACTERIZATION OF SURFACE PLASMON WAVEGUIDES.- NUMERICAL SIMULATIONS OF LONG-RANGE PLASMONIC TRANSMISSION LINES.- SURFACE PLASMON POLARITON GUIDING IN PHOTONIC BANDGAP STRUCTURES.- SUBWAVELENGTH-SCALE PLASMON WAVEGUIDES.- OPTICAL SUPERLENS.- OPTICAL FIELD ENHANCEMENT WITH PLASMON RESONANT BOWTIE NANOANTENNAS.- NEAR-FIELD OPTICAL EXCITATION AND DETECTION OF SURFACE PLASMONS.- PRINCIPLES OF NEAR-FIELD OPTICAL MAPPING.- OVERVIEW OF SIMULATION TECHNIQUES FOR PLASMONIC DEVICES.- PLASMON HYBRIDIZATION IN COMPLEX NANOSTRUCTURES.- SENSING PROTEINS WITH ADAPTIVE METAL NANOSTRUCTURES.- INTEGRATED OPTICS BASED ON LONG-RANGE SURFACE PLASMON POLARITONS.- LOCALIZED SURFACE PLASMONS FOR OPTICAL DATA STORAGE BEYOND THE DIFFRACTION LIMIT.- SURFACE PLASMON COUPLED EMISSION.
TL;DR: The controllable synthesis of nanocrystals with different shapes is very important and challenging as discussed by the authors, and the controllability of the synthesis of nanoparticles with different shape is also very important.
Abstract: The controllable synthesis of nanocrystals with different shapes is very important and challenging. In the present work, silver nanoparticles with different structural architectures, from nanorods, triangular plates, hexagonal plates, and nanocubes to polyhedrons have been synthesized successfully in high yield by a solvothermal process. Especially, the unique silver enneahedral nanoplates are also observed. These nanoparticles exhibit tunable surface plasmon resonance properties from the visible to near-infrared regions. Those nanoparticles were also self-assembled on glass substrates and evaluated as potential surface-enhanced Raman scattering (SERS) substrates using trans-1,2-bis(4-pyridyl)ethylene molecules. Thanks to the enhanced local field effect around their sharp corners and edges, those Ag triangular plates exhibit enhanced SERS properties and can serve as high-sensitivity substrates for SERS-based measurements.
TL;DR: Gold nanorods are covalently conjugated with a nuclear localization signal peptide through a thioalkyl-triazole linker and incubated with an immortalized benign epithelial cell line and an oral cancer cell line to reveal a difference between benign and cancer cell lines.
TL;DR: The fabrication of a label-free, chip-based biosensor based on the localized surface plasmon resonance (LSPR) of gold nanorods is described, which has the significantly lower detection limit and the internal self-reference that the signal of the nanorod sensor providesbased on the measurement of peak wavelength shift.
Abstract: We describe the fabrication of a label-free, chip-based biosensor based on the localized surface plasmon resonance (LSPR) of gold nanorods. Gold nanorods were chemisorbed onto a mercaptosilane-modified glass substrate, followed by conjugation of biotin to the nanorods. Streptavidin binding to biotin was monitored by the wavelength shift of the LSPR peak in the UV−vis extinction spectrum of the immobilized gold nanorods due to the change in local refractive index at the gold nanorod surface induced by streptavidin binding. The limit of detection of the sensor is 0.005 μg/mL (94 pM) in PBS and 1 μg/mL (19 nM) in serum, and the dynamic range spans 94 pM to 0.19 μM. The advantages of the nanorod-based sensor over an LSPR sensor that we had previously fabricated from gold nanospheres (Nath, N.; Chilkoti, A. Anal. Chem. 2002, 74, 504−509; J. Fluoresc. 2004, 14, 377−389; Anal. Chem. 2004, 76, 5370−5378) are the significantly lower detection limit and the internal self-reference that the signal of the nanorod sen...
TL;DR: In this article, it was shown that the normal incidence transmission of circularly polarized light through a nanostructured anisotropic planar chiral metamaterial is asymmetric in the opposite directions.
Abstract: We show that in the visible to near-IR part of the spectrum, normal incidence transmission of circularly polarized light through a nanostructured anisotropic planar chiral metamaterial is asymmetric in the opposite directions. The new effect is fundamentally different from the conventional gyrotropy of bulk chiral media and the Faraday effect. It has a resonance nature associated with a new type of excitation in the metal nanostructure: the enantiomerically sensitive plasmon.
TL;DR: In this paper, an ultra-high sensitive surface plasmon resonance (SPR) sensor based on excitation of a long range SVM was developed, which employed more advanced photonic components like superluminescent diode source and polarization-maintaining fibers, which allowed a dramatic decrease of the sensor detection limit.
Abstract: An ultra-high sensitive surface plasmon resonance (SPR) sensor based on excitation of a long range surface plasmon was developed. Compared to previous reports, the sensor employs more advanced photonic components like superluminescent diode source and polarization-maintaining fibers, which allowed for dramatic decrease of the sensor detection limit. The attained refractive index detection limit of 2.5 × 10−8 is so far the highest value reported for any SPR-based sensor.
TL;DR: This letter proposes a simple expression for predicting the dipolar plasmon resonance of a silica-gold nanoshell of given dimensions, and uses the universal scaling behavior in the Nanoshell system to extend it to the dielectric core-metal shell nanostructure.
Abstract: It has been recently shown that the strength of plasmon coupling between a pair of plasmonic metal nanoparticles falls as a function of the interparticle gap scaled by the particle size with a near-exponential decay trend that is universally independent of nanoparticle size, shape, metal type, or medium dielectric constant. In this letter, we extend this universal scaling behavior to the dielectric core-metal shell nanostructure. By using extended Mie theory simulations of silica core-metal nanoshells, we show that when the shift of the nanoshell plasmon resonance wavelength scaled by the solid nanosphere resonance wavelength is plotted against the shell thickness scaled by the core radius, nanoshells with different dimensions (radii) exhibit the same near-exponential decay. Thus, the nanoshell system becomes physically analogous to the particle-pair system, i.e., the nanoshell plasmon resonance results from the coupling of the inner shell surface (cavity) and the outer shell surface (sphere) plasmons over a separation distance essentially given by the metal shell thickness, which is consistent with the plasmon hybridization model of Prodan, Halas, and Nordlander. By using the universal scaling behavior in the nanoshell system, we propose a simple expression for predicting the dipolar plasmon resonance of a silica-gold nanoshell of given dimensions.
TL;DR: This label-free biomolecular absorption nanospectroscopic method has ultrahigh molecular sensitivity and quantized plasmon quenching dips in resonant Rayleigh scattering spectra by plAsmon resonance energy transfer (PRET).
Abstract: 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.
TL;DR: In this article, a combination of the enhanced transmission effect and shape resonances in a periodic array of nanoscale double-hole structures in a gold film was used to enhance the detection sensitivity of surface plasmon biosensors.
Abstract: The authors report a combination of the enhanced transmission effect and shape resonances in a periodic array of nanoscale double-hole structures in a gold film to enhance the detection sensitivity of surface plasmon biosensors. Finite-difference time-domain calculations are used to quantify field enhancement at the apexes of the double-hole structure. The double-hole array was used to measure the formation of a self-assembled monolayer and for real-time sensing of protein adsorption onto a gold surface. This result demonstrates the potential to integrate propagating surface plasmons and localized shape resonances to improve real-time biosensors.