Showing papers on "Surface plasmon resonance published in 1999"
TL;DR: In this paper, the surface plasmon absorption of noble metal nanoparticles was studied and the effects of size, shape, and composition on the plasman absorption maximum and its bandwidth were discussed.
Abstract: The field of nanoparticle research has drawn much attention in the past decade as a result of the search for new materials. Size confinement results in new electronic and optical properties, possibly suitable for many electronic and optoelectronic applications. A characteristic feature of noble metal nanoparticles is the strong color of their colloidal solutions, which is caused by the surface plasmon absorption. This article describes our studies of the properties of the surface plasmon absorption in metal nanoparticles that range in size between 10 and 100 nm. The effects of size, shape, and composition on the plasmon absorption maximum and its bandwidth are discussed. Furthermore, the optical response of the surface plasmon absorption due to excitation with femtosecond laser pulses allowed us to follow the electron dynamics (electron−electron and electron−phonon scattering) in these metal nanoparticles. It is found that the electron−phonon relaxation processes in nanoparticles, which are smaller than t...
3,635 citations
TL;DR: In this paper, a linear relationship was found between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio as determined from TEM and it was shown that such a linear dependence is also predicted theoretically.
Abstract: Gold nanorods with different aspect ratios are prepared in micelles by the electrochemical method and their absorption spectra are modeled by theory. Experimentally, a linear relationship is found between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio as determined from TEM. It is shown here that such a linear dependence is also predicted theoretically. However, calculations also show that the absorption maximum of the longitudinal plasmon resonance depends on the medium dielectric constant in a linear fashion for a fixed aspect ratio. Attempts to fit the calculations to the experimental values indicate that the medium dielectric constant has to vary with the aspect ratio in a nonlinear way. Chemically, this suggests that the structure of the micelle capping the gold nanorods is size dependent. Furthermore, comparison with the results obtained for rods of different aspect ratios made by systematic thermal decomposition of the long rods further suggests that the medi...
1,539 citations
TL;DR: Theoretical analysis and comparison of the sensitivity of surface plasmon resonance (SPR) sensors using diffraction at gratings and attenuated total reflection (ATR) in prism couplers for two detection methods-resonant angle interrogation and resonant wavelength interrogation is presented in this article.
Abstract: Theoretical analysis and comparison of the sensitivity of surface plasmon resonance (SPR) sensors using diffraction at gratings and attenuated total reflection (ATR) in prism couplers for two detection methods-resonant angle interrogation and resonant wavelength interrogation is presented. Analytical expressions for sensitivity of these SPR sensors are derived and the influence of the major design parameters of the sensing structures on the sensor sensitivity is discussed. The analysis shows that grating-based SPR sensors using wavelength interrogation are much less sensitive then their prism coupler-based counterparts. In the angular interrogation mode, the sensitivity of SPR sensors using diffraction gratings depends on the diffraction order and does not differ much from that of SPR sensors based on prism couplers.
632 citations
TL;DR: Ten proteins and two low-molecular-weight ligands were immobilized on mixed self-assembled monolayers (SAMs) of alkanethiolates on gold generated from the tri(ethylene glycol)-terminated thiol 1 and these SAMs were resistant to nonspecific adsorption of proteins having a wide range of molecular weights and isoelectric points.
Abstract: This paper describes the immobilization of ten proteins and two low-molecular-weight ligands on mixed selfassembled monolayers (SAMs) of alkanethiolates on gold generated from the tri(ethylene glycol)-terminated thiol 1 (HS(CH2)11(OCH2CH2)3OH) (χ(1) = 1.0−0.0) and the longer, carboxylic acid-terminated thiol 2 (HS(CH2)11(OCH2CH2)6OCH2CO2H) (χ(2) = 0.0−1.0). The immobilization was achieved by a two-step procedure: generation of reactive N-hydroxysuccinimidyl esters from the carboxylic acid groups of 2 in the SAM and coupling of these groups with amines on the protein or ligand. Because this method involves a common reactive intermediate that is easily prepared, it provides a convenient method for attaching ligands to SAMs for studies using surface plasmon resonance spectroscopy (and, in principle, other bioanalytical methods that use derivatized SAMs on gold, silver, and other surfaces). These SAMs were resistant to nonspecific adsorption of proteins having a wide range of molecular weights and isoelectri...
611 citations
TL;DR: The plasmon resonance of metal nanoshells displays a geometric tunability controlled by the ratio of the core radius to the total radius for gold-coated Au2S as discussed by the authors.
Abstract: A metal nanoshell consists of a nanometer-scale dielectric core surrounded by a thin metallic shell. The plasmon resonance of metal nanoshells displays a geometric tunability controlled by the ratio of the core radius to the total radius. For gold-coated Au2S this ratio varies from 0.6 to 0.9, yielding a plasmon resonance tunable from 600 to greater than 1000 nm. Mie scattering theory for the nanoshell geometry quantitatively accounts for the observed plasmon resonance shifts and linewidths. In addition, the plasmon linewidth is shown to be dominated by electron surface scattering.
575 citations
TL;DR: In this article, the authors examined the electrodynamics of silver nanoparticles and of clusters of nanoparticles, with an emphasis on extinction spectra and of electric fields near the particle surfaces that are important in determining surfaceenhanced Raman (SER) intensities.
Abstract: In this paper we examine the electrodynamics of silver nanoparticles and of clusters of nanoparticles, with an emphasis on extinction spectra and of electric fields near the particle surfaces that are important in determining surface-enhanced Raman (SER) intensities. The particles and clusters are chosen to be representative of what has been studied in recent work on colloids and with lithographically prepared particles. These include spheres, spheroids, truncated tetrahedrons, and clusters of two or three of these particles, with sizes that are too large to be described with simple electrostatic approximations but small compared to the wavelength of light. The electrodynamics calculations are mostly based on the discrete dipole approximation (DDA), which is a coupled-finite element approach which produces exact or nearly exact results for particles of arbitrary size and shape if fully converged. Mie theory results are used to study the validity of the DDA for spherical particles, and we also study the validity of the modified long wavelength approximation (MLWA), which is based on perturbative corrections to the electrostatic limit, and of the single dipole per particle approximation (SDA). The results show how the dipole plasmon resonance properties and the electric field contours around the particle vary with particle shape and size for isolated particles. For clusters of particles, we study the effect of interparticle spacing on plasmon resonance characteristics. We also show that the quadrupole resonance is much less sensitive to particle shape and interparticle interactions than the dipole plasmon resonance. These results provide benchmarks that will be used in future comparisons with experiment.
567 citations
TL;DR: In this paper, the authors examined the effect of solvent on the optical extinction spectrum of periodic arrays of surface-confined silver nanoparticles fabricated by nanosphere lithography (NSL) and showed that the defect sites that occur as a byproduct of the NSL fabrication process play a negligible role in the macroscale extinction spectrum.
Abstract: In this paper we examine the effect of solvent on the optical extinction spectrum of periodic arrays of surface-confined silver nanoparticles fabricated by nanosphere lithography (NSL). By use of NSL, it is possible to systematically vary the out-of-plane height of the nanoparticles, and by thermal annealing, we can control the nanoparticle shape. We have studied four separate samples of nanoparticle arrays; three samples have nanoparticles that are truncated tetrahedral in shape but that differ in out-of-plane height and one sample has nanoparticles that are oblate ellipsoidal in shape. By performing UV−vis extinction spectroscopy measurements at 12 μm spatial resolution, we show that the defect sites that occur as a byproduct of the NSL fabrication process play a negligible role in the macroscale extinction spectrum. We find that the extinction spectrum of the nanoparticles that are oblate ellipsoidal in shape is least sensitive to the surrounding dielectric medium, and the extinction spectrum of the na...
522 citations
TL;DR: In this paper, surface enhanced Raman scattering (SERS) is observed when enough gold is deposited on the silica cores to form a nearly complete metal shell, and the SERS signal is due to both the local enhancement of the dielectric field via the plasmon resonance of the nanostructure and to the localized regions of high field intensity provided by the nearly completed gold shell.
Abstract: A metal nanoshell is a composite nanoparticle consisting of a dielectric core coated by a thin metal shell; its peak plasmon resonance wavelength is determined by the ratio of the core diameter to the shell thickness. When p-mercaptoaniline (p-MA) is in solution with gold nanoshells that have their plasmon resonance near a 1.06 μm excitation source, significant surface enhanced Raman scattering(SERS) is observed. The strongest Raman enhancements are obtained when enough gold is deposited on the silica cores to form a nearly complete metal shell. Correlations between transmission electron microscopy (TEM)-defined structure, ultraviolet (UV)-visible spectra, SERS signal strength, and electromagnetic theory show that the SERS signal is due to both the local enhancement of the dielectric field via the plasmon resonance of the nanostructure and to the localized regions of high field intensity provided by the nearly completed gold shell. Comparison with SERS enhancements on completed nanoshell structures indicates the relative contribution of these two effects.
395 citations
TL;DR: In this article, the effects of nanometer-sized silver particles on the optical properties of Eu3+ ions in SiO2 glass were investigated by using Mie-Drude theory modified by electron mean free path model.
Abstract: We have investigated the effects of nanometer-sized silver particles on the optical properties of Eu3+ ions in SiO2 glass. Glass samples were prepared by the sol-gel method. The mean particle size and volume fraction of silver particles, which were estimated from UV-VIS absorption spectra using Mie-Drude theory modified by electron mean free path model, rapidly increased with the reduction time of Ag+ up to ∼3 min at 900 °C. The fluorescence from Eu3+ ions for the excitation by N2 laser was greatly enhanced in the presence of silver particles of 4.3 nm size. Our experimental results suggest that the origin of enhanced fluorescence is from local field enhancement around Eu3+ ions, owing to the surface plasmon resonance of small silver particles.
359 citations
TL;DR: A multistep surface modification procedure for the creation of DNA arrays on chemically modified gold surfaces that can be used in surface plasmon resonance (SPR) imaging studies of protein−DNA interactions is demonstrated in this article.
Abstract: A multistep surface modification procedure for the creation of DNA arrays on chemically modified gold surfaces that can be used in surface plasmon resonance (SPR) imaging studies of protein−DNA interactions is demonstrated. The multistep procedure is required to create an array of spots that are surrounded first by a hydrophobic background which allows for the pinning of aqueous DNA solutions onto individual array elements and then to replace that hydrophobic background with one that resists the nonspecific adsorption of proteins during in situ SPR imaging measurements. An amine-terminated alkanethiol monolayer is employed as the base layer, and Fmoc and PEG modifiers are used to create the sequentially hydrophobic and protein adsorption-resistant surfaces, respectively. Specifically, the chemical modification steps are the following: (1) the adsorption and self-assembly of an 11-mercaptoundecylamine (MUAM) monolayer on an evaporated gold thin film, (2) the reaction of the MUAM monolayer with an Fmoc pro...
359 citations
Patent•
21 Apr 1999TL;DR: In this paper, the authors proposed a method of bringing the article into contact with a medium containing or suspected of containing the target biological molecule and allowing the biological molecule to biologically bind to the binding partner.
Abstract: An article suitable for use as a biosensor includes a molecule of a formula X—R—Ch adhered to a surface of the article as part of a self-assembled monolayer. X is a functionality that adheres to the surface, R is a spacer moiety, and Ch is a chelating agent. A metal ion can be coordinated by the chelating agent, and a polyamino acid-tagged biological binding partner of a target biological molecule coordinated to the metal ion. A method of the invention involves bringing the article into contact with a medium containing or suspected of containing the target biological molecule and allowing the biological molecule to biologically bind to the binding partner. The article is useful particularly as a surface plasmon resonance chip.
TL;DR: In this paper, the authors measured the optical extinction spectrum of a periodic array of silver nanoparticles fabricated by nanosphere lithography (NSL) and compared the results with predictions of electrodynamic theory.
Abstract: In this paper we measure the optical extinction spectrum of a periodic array of silver nanoparticles fabricated by nanosphere lithography (NSL) and present detailed comparisons of the results with predictions of electrodynamic theory. The silver nanoparticles are small (∼100 nm) compared to the wavelength of light but too large to have their optical properties described adequately with a simple electrostatic model. We make use of the discrete dipole approximation (DDA), which is a coupled finite element method. With the DDA one can calculate the extinction of light as a function of wavelength for particles of arbitrary size and shape. We show that NSL-fabricated Ag nanoparticles can be modeled without adjustable parameters as truncated tetrahedrons, taking their size and shape parameters directly from atomic force microscopy (AFM) measurements and using literature values of the bulk dielectric constants of silver. These AFM measurements are presented as part of this paper, and the resulting theoretical li...
TL;DR: A new method for observing cell/substrate contacts of living cells in culture based on the optical excitation of surface plasmons is developed, which obtained a cell/ substrate distance of 160 +/- 10 nm for most parts of the cells.
TL;DR: In this paper, surface plasmon resonance (SPR) measurements were applied to the study of ultrathin organic and inorganic films adsorbed onto gold surfaces utilizing near-infrared (NIR) excitation from 800 to 1152 nm.
Abstract: The application of surface plasmon resonance (SPR) measurements to the study of ultrathin organic and inorganic films adsorbed onto gold surfaces utilizing near-infrared (NIR) excitation from 800 to 1152 nm is described. SPR scanning angle measurements of film thickness are demonstrated at 814 and 1152 nm using low-power diode and HeNe laser sources, respectively. Several advantages of SPR in the NIR are noted. The in situ reflectivity versus angle of incidence curves sharpen greatly (as compared to 632.8 nm) at longer wavelengths so that there is no loss in sensitivity in the measurement of film thickness despite a doubling of the excitation wavelength. The sharper resonance and longer wavelengths also allow for the measurement of thicker films. Examples of SPR thickness measurements for self-assembled alkanethiol monolayers and composite biopolymer/SiO2 nanoparticle electrostatic multilayer films are given. SPR imaging experiments are also performed at various NIR wavelengths using an incoherent white l...
TL;DR: In this paper, the fundamental mechanical radial mode of silver nanoparticles is coherently excited and probed via its interaction with the electron gas, and the mechanical oscillations are launched by an indirect displacive process and are detected via the induced modulation of the surface plasmon resonance frequency.
Abstract: Using a femtosecond pump-probe technique, the fundamental mechanical radial mode of silver nanoparticles is coherently excited and probed via its interaction with the electron gas. The mechanical oscillations are launched by an indirect displacive process and are detected via the induced modulation of the surface plasmon resonance frequency. The measured fundamental radial mode period and damping time are found to be proportional to the nanoparticle radius in the range of 3–15 nm, in agreement with theoretical predictions.
TL;DR: In this article, the influence of colloid diameter on the surface plasmon resonance (SPR) response of a colloidal Au modified Au film was described, and it was shown that 30−59 nm diameter colloid Au can significantly increase the SPR response.
Abstract: The influence of colloid diameter on the surface plasmon resonance (SPR) response of a colloidal Au modified Au film is described. Adsorption of 30−59 nm diameter colloidal Au on the surface of a 4...
TL;DR: In this paper, a simple methodology was developed to enable a greater enhancement of fluorescence from europium (Eu3+)-doped silica gels containing adsorbed silver (Ag) islands.
Abstract: A simple methodology has been developed to enable a greater enhancement of fluorescence from europium (Eu3+)-doped silica gels containing adsorbed silver (Ag) islands. The procedure involves the preparation of Eu3+-doped silica gels by a sol−gel method and then immersion in a Ag sol for ca. 48 h to allow the adsorption of Ag islands on the pore surfaces of silica gels. UV−vis spectra show the characteristic surface plasmon resonance of the Ag at around 390 nm, and transmission electron microscopy (TEM) presents Ag islandlike particles on the surface of silica gels. The photoluminescence studies reveal the fact that the enhanced fluorescence originates from the local field enhancement around Eu3+ ions, caused by the electronic plasmon resonance of the Ag islands.
TL;DR: The SPR was able to detect changes in the relative surface concentration of each component demonstrating that the protein's residence time at the interface was dependent upon its molecular weight, bulk concentration and surface affinity.
TL;DR: In this article, a method of interferometric surface plasmon resonance imaging is proposed and applied to develop ultrasensitive affinity array sensors with a monoatomic thickness resolution, and conditions at which phase of light demonstrates a markedly different behavior for close values of system parameters as well as the Heaviside jump are explained in terms of phase topology.
Abstract: Conditions at which phase of light demonstrates a markedly different behavior for close values of system parameters as well as the Heaviside jump are discussed and explained in terms of phase topology. On this basis, a method of interferometric surface plasmon resonance imaging is proposed and applied to develop ultrasensitive affinity array sensors with a monoatomic thickness resolution.
TL;DR: The effect of colloidal Au nanoparticle immobilization on surface plasmon resonance (SPR) reflectivity is reported in this paper, where the authors show that colloidal nanoparticles on an evaporated Au film results in a large shift in the plasmin resonance angle, a broadening of the surface resonance, and an increase in minimum reflectance.
Abstract: The effect of colloidal Au nanoparticle immobilization on surface plasmon resonance (SPR) reflectivity is reported. Immobilization of 25 nm diameter colloidal Au on to an evaporated Au film results in a large shift in plasmon angle, a broadened plasmon resonance and an increase in minimum reflectance. This results in increased SPR sensitivity, demonstrated in several ways, including a sandwich immunoassay for human IgG, enlargement of a 1.4 nm diameter Au cluster, and detection of displacement of surface-bound biotinylated colloidal Au by free biocytin in solution. Similarly large changes in reflectivity are realized upon binding of colloidal Au to electrolessly deposited Au films prepared entirely by wet-chemical methods. These results represent potentially significant advances in the generality and sensitivity of SPR.
TL;DR: The phase behavior under surface plasmon resonance (SPR) interferometry has been comprehensively described by theoretical analysis, numerical simulations, and a number of experiments.
Abstract: Surface plasmon resonance (SPR) interferometry is reported as a novel technique for biological and chemical sensing, which employs not only the amplitude of a resonantly reflected light wave, but its phase as well. In this connection, the phase behavior under SPR has been comprehensively described by theoretical analysis, numerical simulations, and a number of experiments. Near optimum SPR conditions, a resonant phase dependence is step-like, the ‘step’ being at the reflectivity minimum. For SPR-based sensors, the slope of the ‘step’ can always be made by several orders steeper than that of the resonant reflectivity contour. The ‘step’ has been imaged by the fringe of a 2-dimensional interference pattern where one coordinate was the incidence angle, and the other was the phase. The inversion of the ‘step’ has been observed for the first time during antigen–antibody binding, when the system passes through the optimum SPR conditions. Monitoring the inversion provides for ultra-high sensitivity to an analyte while recording angular position of the ‘step’, does for dynamic range as wide as that of traditional SPR sensors. The SPR interferometry technique has confirmed theoretical findings and opened up new possibilities for (bio)chemical sensing.
TL;DR: In this paper, numerical simulations and microwave measurements on a loop-wire structure that acts as an effective medium exhibiting a well-defined bulk plasma frequency in the microwave regime, with an effective negative dielectric function below this plasma frequency.
Abstract: We present numerical simulations and microwave measurements on a loop-wire structure that acts as an effective medium exhibiting a well-defined bulk plasma frequency in the microwave regime, with an effective negative dielectric function below this plasma frequency. The dependence of this plasmonic response on the self-inductance of the constituent wire elements is made explicit. A finite structure, approximately spherical, composed of this inductive medium is studied, and reveals subwavelength surface plasmon resonances below the bulk plasma frequency.
TL;DR: In this paper, the necessary high SHG efficiency is obtained by nanoparticles produced by an electron beam lithographic method, which enables them to fabricate a two-dimensional array of nearly identical, parallel oriented particles of designed shape without centrosymmetry.
Abstract: . The necessary high SHG efficiency is obtained by nanoparticles produced by an electron beam lithographic method, which enables us to fabricate a two-dimensional array of nearly identical, parallel oriented particles of designed shape without centrosymmetry, essential for high SHG efficiency and the tuning of the plasmon resonance to the driving laser wavelength of 780 nm.
TL;DR: A new variant of this technique, coupled plasmon-waveguide resonance (CPWR) spectroscopy, allows the characterization of anisotropic biological membranes.
TL;DR: Through thiolipids a planar lipid bilayer was immobilized on a gold support for use as an electrode, which allows the detection of the ligand-gating function of the natural transmembrane channel protein OmpF reconstituted in the artificial membrane.
Abstract: Through thiolipids a planar lipid bilayer (1) was immobilized on a gold support (2) for use as an electrode. This allows the detection of the ligand-gating function of the natural transmembrane channel protein OmpF (3) reconstituted in the artificial membrane: the binding of a domain (4) of the toxin colicin N, observed by surface plasmon resonance, induces the blocking of the OmpF channel protein, as shown by impedance spectroscopy.
TL;DR: In this paper, a theoretical analysis of the phenomenon of excitation of surface plasma waves in integrated-optical waveguide structures is carried out using a bi-directional mode expansion and propagation method.
Abstract: A theoretical analysis of the phenomenon of excitation of surface plasma waves in integrated-optical waveguide structures is carried out. Rigorous approach to analysis of light propagation through a waveguide structure with a thin metal overlayer supporting surface plasma waves is formulated using a bi-directional mode expansion and propagation method. It is demonstrated that because the back-reflections in the structure are very weak and most of optical power is transmitted by only a limited number of modes of the sensing structure, the method can be considerably simplified.
TL;DR: In this paper, a method for detecting surface plasmon resonance with high resolution (∼10−5 degrees or ∼10−8 refractive index units) and fast response time (1 μs) is described.
Abstract: A method for detecting surface plasmon resonance with high resolution (∼10−5 degrees or ∼10−8 refractive index units) and fast response time (1 μs) is described. In the method, light is focused through a prism onto a metal film on which molecules to be detected are adsorbed. The total internal reflection of the incident light is collected with a bicell photodetector instead of a single cell or an array of photodetectors that are widely used in previous works. The ratio of the differential signal to the sum signal of the bicell photodetector provides an accurate measurement of shift in surface plasmon resonance angle caused by the adsorption of molecules onto the metal films or by conformational changes in the adsorbed molecules. Using the method, we have studied subtle conformational changes in redox protein, cytochrome c, due to an electron transfer reaction.
TL;DR: This paper describes a generally applicable method using a synthetic chelator thioalkane that can be self-assembled on gold surfaces that opens possibilities for the development of biosensors.
TL;DR: In this article, the authors presented the advantages of modifying the geometry of the sensing tip of a white-light, multimode optical fiber SPR sensor to optimize the dynamic range and sensitivity.
Abstract: This paper presents the advantages of modifying the geometry of the sensing tip of a white-light, multimode optical fiber SPR sensor to optimize the dynamic range and sensitivity. By selectively beveling the distal end of the fiber probe, the wavelength of resonance can be red-shifted by more than 100 nm and blue-shifted by more than 30 nm. This increases the flexibility of a white-light SPR sensor by increasing the dynamic range of accessible RIs and by shifting the resonance to the most sensitive regions of the detector. Sensitivity, measured in wavelength shift per RI change, can be increased by a factor of 4. Also, multiple-wavelength regions of SPR activity can simultaneously be observed on the same probe, thus increasing the information content of a SPR spectrum.
TL;DR: Two systems, one for the analysis of oligosaccharides and the other for glycoproteins, were developed after a rigorous analysis and evaluation of such parameters as binding conditions, buffers, and regeneration conditions.