Showing papers on "Surface plasmon resonance published in 2002"
TL;DR: The LSPR nanobiosensor provides a pathway to ultrasensitive biodetection experiments with extremely simple, small, light, robust, low-cost instrumentation that will greatly facilitate field-portable environmental or point-of-service medical diagnostic applications.
Abstract: Triangular silver nanoparticles (∼100 nm wide and 50 nm high) have remarkable optical properties. In particular, the peak extinction wavelength, λmax of their localized surface plasmon resonance (LSPR) spectrum is unexpectedly sensitive to nanoparticle size, shape, and local (∼10−30 nm) external dielectric environment. This sensitivity of the LSPR λmax to the nanoenvironment has allowed us to develop a new class of nanoscale affinity biosensors. The essential characteristics and operational principles of these LSPR nanobiosensors will be illustrated using the well-studied biotin−streptavidin system. Exposure of biotin-functionalized Ag nanotriangles to 100 nM streptavidin (SA) caused a 27.0 nm red-shift in the LSPR λmax. The LSPR λmax shift, ΔR/ΔRmax, versus [SA] response curve was measured over the concentration range 10-15 M < [SA] < 10-6 M. Comparison of the data with the theoretical normalized response expected for 1:1 binding of a ligand to a multivalent receptor with different sites but invariant af...
2,018 citations
TL;DR: In this paper, the effect of size and shape on the spectral response of individual silver nanoparticles was studied and it was shown that specific geometrical shapes give distinct spectral responses.
Abstract: We present a systematic study of the effect of size and shape on the spectral response of individual silver nanoparticles. An experimental method has been developed that begins with the detection and characterization of isolated nanoparticles in the optical far field. The plasmon resonance optical spectrum of many individual nanoparticles are then correlated to their size and shape using high-resolution transmission electron microscopy. We find that specific geometrical shapes give distinct spectral responses. In addition, inducing subtle changes in the particles’ morphology by heating causes a shift in the individual particle spectrum and provides a simple means of tuning the spectral response to a desired optical wavelength. Improved colloidal preparation methods could potentially lead to homogeneous populations of identical particle shapes and colors. These multicolor colloids could be used as biological labels, surface enhanced Raman scattering substrates, or near field optical microscopy sources cove...
1,687 citations
TL;DR: The surface plasmon resonance of gold nanoshells exhibited a much more sensitive response toward environmental changes even when compared with solid colloids with a mean size much smaller than that of gold nanoparticles.
Abstract: Gold nanoshells have been synthesized by reacting aqueous HAuCl4 solutions with solid templates such as silver nanoparticles. The morphology, void space, and wall thickness of these hollow nanostructures were all determined by the templates, which were completely converted into soluble species during the replacement reaction. The surface plasmon peaks of these gold nanoshells were considerably red-shifted as compared to gold solid colloids having approximately the same dimensions. In addition, the surface plasmon resonance of gold nanoshells exhibited a much more sensitive response toward environmental changes even when compared with solid colloids with a mean size much smaller than that of gold nanoshells. For example, the sensitivity factor (i.e., the shift in peak position per unit change in the refractive index of the surrounding medium) was 408.8, 60.0, and 70.9 nm per refractive index unit for gold nanoshells with a mean diameter of 50 nm and wall thickness of 4.5 nm, gold solid colloids of 50 nm in...
589 citations
TL;DR: It is shown that the surface plasmon contribution is not the prime effect and that waveguide mode resonance and diffraction are responsible for the extraordinary transmission of metallic grating with very narrow slits and the transmittance of subwavelength metallic gratings is always nearly zero.
Abstract: It is generally admitted that the extraordinary transmission of metallic grating with very narrow slits is mainly due to the excitation of surface plasmons on the upper and lower interfaces of the grating We show that the surface plasmon contribution is not the prime effect and that waveguide mode resonance and diffraction are responsible for the extraordinary transmission Additionally and surprisingly, we reveal that the transmittance of subwavelength metallic gratings is always nearly zero for frequencies corresponding to surface plasmon excitation This finding implies that surface plasmons play a negative role in the transmission
585 citations
TL;DR: It is shown that single molecules can be trapped at junctions between closely spaced nanoparticles, which are simultaneously pulled together by optical forces and could significantly influence surface-enhanced Raman scattering and related spectroscopies under normal experimental conditions and contribute to single-molecule sensitivity.
Abstract: We use extended Mie theory to investigate optical forces induced by and acting on small silver nanoparticle aggregates excited at surface plasmon resonance. It is shown that single molecules can be trapped at junctions between closely spaced nanoparticles, which are simultaneously pulled together by optical forces. These effects could significantly influence surface-enhanced Raman scattering and related spectroscopies under normal experimental conditions and contribute to single-molecule sensitivity.
467 citations
TL;DR: Results of kinetic, equilibrium, and temperature-dependent studies, obtained using in-situ surface plasmon resonance (SPR) spectroscopy, show that hybridization for surface immobilized DNA is quite different from the well-studied solution-phase reaction.
Abstract: We investigate how probe density influences hybridization for unlabeled target oligonucleotides that contain mismatched sequences or targets that access different binding locations on the immobilized probe. We find strong probe density effects influencing not only the efficiency of hybridization but also the kinetics of capture. Probe surfaces are used repeatedly, and the potentially large contributions of sample-to-sample variations in surface heterogeneity and nonspecific adsorption are addressed. Results of kinetic, equilibrium, and temperature-dependent studies, obtained using in-situ surface plasmon resonance (SPR) spectroscopy, show that hybridization for surface immobilized DNA is quite different from the well-studied solution-phase reaction. Surface hybridization depends strongly on the target sequence and probe density. Much of the data can be explained by the presence of steric crowding at high probe density; however, the behavior of mismatched sequences cannot be understood using standard models of hybridization even at the lowest density studied. In addition to unusual capture kinetics observed for the mismatched targets, we find that the binding isotherms can be fit only if a heterogeneous model is used. For mismatched targets, the Sips model adequately describes probe-target binding isotherms; for perfectly matched targets, the Langmuir model can be used.
398 citations
TL;DR: In this paper, the Raman spectra of several molecules adsorbed on gold nanospheres (NSs) and nanorods (NRs) were studied using an off-plasmon resonance excitation condition.
395 citations
01 Feb 2002
TL;DR: Quartz crystal microbalance with dissipation measurements were used to investigate the adsorption of human fibrinogen, human serum albumin, bovine hemoglobin, horse heart cytochrome c, human immunoglobulin, and 10% fetal bovines serum on supported bilayers of egg-phosphatidylcholine (eggPC) lipids.
Abstract: Quartz crystal microbalance with dissipation (QCM-D) measurements were used to investigate the adsorption of human fibrinogen, human serum albumin, bovine hemoglobin, horse heart cytochrome c, human immunoglobulin (hIgG), and 10% fetal bovine serum on supported bilayers of egg-phosphatidylcholine (eggPC) lipids. For comparison the adsorption of fibrinogen and hIgG to eggPC bilayers was also studied with surface plasmon resonance (SPR). The supported bilayers were formed in situ by vesicle adhesion and spontaneous fusion onto a SiO(2) surface. The supported lipid bilayer is highly protein resistant: The irreversible adsorption measured with the QCM-D technique was below the detection level, while reversible protein adsorption was detected for all the proteins in the range 0.3-4% of the saturation coverage on a hydrophobic thiol monolayer on gold. The adsorbed amounts were slightly higher for the SPR measurements. Possible mechanisms for the protein resistance of eggPC bilayers are briefly discussed.
296 citations
TL;DR: By studying variants based on the FLAG binding motif, it was possible to distinguish peptides differing by a single amino acid substitution using SPR imaging, and quantitative analysis of the signal was accomplished using the peptide array to simultaneously determine the binding constants of the antibody-peptide interactions for four peptides.
Abstract: The characterization of peptide arrays on gold surfaces designed for the study of peptide−antibody interactions using surface plasmon resonance (SPR) imaging is described. A two-step process was used to prepare the peptide arrays: (i) a set of parallel microchannels was used to deliver chemical reagents to covalently attach peptide probes to the surface by a thiol−disulfide exchange reaction; (ii) a second microchannel with a wraparound design was used as a small-volume flow cell (5 μL) to introduce antibody solutions to the peptide surface. As a demonstration, the interactions of the FLAG epitope tag and monoclonal anti-FLAG M2 were monitored by SPR imaging using a peptide array. This peptide−antibody pair was studied because of its importance as a means to purify fusion proteins. The surface coverage of the FLAG peptide was precisely controlled by creating the peptide arrays on mixed monolayers of alkanethiols containing an amine-terminated surface and an inert alkanethiol. The mole fraction of peptide...
272 citations
TL;DR: The binding interactions of small molecules with carbonic anhydrase II were used as model systems to compare the reaction constants determined from surface‐ and solution‐based biophysical methods and binding kinetics were shown to provide more detailed information about complex formation than equilibrium constants alone.
Abstract: The binding interactions of small molecules with carbonic anhydrase II were used as model systems to compare the reaction constants determined from surface- and solution-based biophysical methods. Interaction data were collected for two arylsulfonamide compounds, 4-carboxybenzenesulfonamide (CBS) and 5-dimethyl-amino-1-naphthalene-sulfonamide (DNSA), binding to the enzyme using surface plasmon resonance, isothermal titration calorimetry, and stopped-flow fluorescence. We demonstrate that when the surface plasmon resonance biosensor experiments are performed with care, the equilibrium, thermodynamic, and kinetic constants determined from this surface-based technique match those acquired in solution. These results validate the use of biosensor technology to collect reliable data on small molecules binding to immobilized macromolecular targets. Binding kinetics were shown to provide more detailed information about complex formation than equilibrium constants alone. For example, although carbonic anhydrase II bound DNSA with twofold higher affinity than CBS, kinetic analysis revealed that CBS had a fourfold slower dissociation rate. Analysis of the binding and transition state thermodynamics also revealed significant differences in the enthalpy and entropy of complex formation. The lack of labeling requirements, high information content, and high throughput of surface plasmon resonance biosensors will make this technology an important tool for characterizing the interactions of small molecules with enzymes and receptors.
254 citations
TL;DR: In this paper, surface plasmon fields can be imaged in real time by detecting the fluorescence of a molecular film close to the plasman carrying metal surface, which can be used to image the field profile of surface plasmons launched at lithographically designed nanoscopic defects.
Abstract: We demonstrate that surface plasmon fields can be imaged in real time by detecting the fluorescence of a molecular film close to the plasmon carrying metal surface. We use this method to image the field profile of surface plasmons launched at lithographically designed nanoscopic defects.
TL;DR: In this article, the authors examined several physical mechanisms that influence the plasmon lineshape of nanoshells with diameters of 100-250 nm, including phase retardation effects, inhomogeneous broadening due to core and shell size distributions, and electron scattering at the shell interfaces.
Abstract: Nanoshells are mesoscopic particles consisting of a dielectric core coated with a metal shell, in particular gold or silver, of uniform nanometer scale thickness. This topology supports plasmon excitations with frequencies that are sensitively dependent on the relative radii of the nanoparticle's core and shell. The plasmon linewidth for this geometry is typically quite broad, nominally 100 nm or more in wavelength at plasmon resonance wavelengths in the near infrared. Several distinct physical mechanisms control the plasmon lineshape: phase retardation effects, including multipolar plasmon contributions; inhomogeneous broadening due to core and shell size distributions; and electron scattering at the shell interfaces. These mechanisms are examined in terms of their relative contributions to the plasmon line shape for nanoshells fabricated with diameters of 100--250 nm.
TL;DR: In this paper, a new structure of resonant metallic film based on bimetallic silver/gold layers (gold as an outer layer) is suggested, which combines advantages of both gold and silver resonant layers.
Abstract: Two metals are used in resonant layers for chemical sensors based on surface plasmon resonance (SPR) - gold and silver. Gold displays higher shift of the resonance angle to changes of ambient refraction index and is chemically stable. Silver posses narrower resonance curve thus providing a higher signal/noise ratio of SPR chemical sensors, but has a poor chemical stability. A new structure of resonant metallic film based on bimetallic silver/gold layers (gold as an outer layer) is suggested. It combines advantages of both gold and silver resonant layers. Bimetallic resonant films display so high shift of resonance angle on changes of ambient refraction index as gold films, but show narrower resonance curve, thus providing a higher signal / noise ratio. Additionally, the outer gold layer protects silver against oxidation.
TL;DR: In this paper, the effects of deposition parameters on surface plasmon resonance wavelengths were quantified using a so-called "design of experiment" analysis, which produces reliable predictive models for producing Ag and Au films with predetermined surface resonance wavelengths.
Abstract: Precise control of thermal evaporation deposition parameters allows the reproducible production of silver and gold island films on glass substrates with tunable surface plasmon resonance wavelengths. Specific combinations of substrate temperature, deposition rate, and film thickness produce films exhibiting surface plasmon resonance wavelengths that can be adjusted from throughout the visible and into the near infrared regions of the electromagnetic spectrum. The effects of deposition parameters on surface plasmon resonance wavelengths are quantified using a so-called “design of experiment” analysis. The analysis produces reliable predictive models for producing Ag and Au films with predetermined surface plasmon resonance wavelengths.
TL;DR: The photoluminescence of Er3+ in borosilicate glass is strongly enhanced by the presence of silver as discussed by the authors, and it is possible to increase the excitation efficiency by up to a factor of 70 when excited at 488 nm.
Abstract: The photoluminescence of Er3+ in borosilicate glass is strongly enhanced by the presence of silver Samples prepared by a combination of erbium ion implantation and Na+↔Ag+ ion exchange show an increase of the Er3+ excitation efficiency of up to a factor 70 when excited at 488 nm Excitation of Er3+ is possible over a broad wavelength range in the near ultraviolet and visible Our data suggest that absorption of light occurs at a silver ion/atom pair or similar defect, followed by energy transfer to Er3+ We can exclude that silver nanocrystals are part of the dominant excitation mechanism, neither via local field enhancement effects due to their surface plasmon resonance nor via absorption and subsequent energy transfer to Er3+
TL;DR: The theory of this new type of sensor based on optical absorption was explained and demonstrated by the simulation of the SPR curves using optical parameters relating to a silver-metal-based SPR sensor.
Abstract: An optical-absorption-based surface plasmon resonance (SPR) sensor is proposed, and its theoretical aspects are discussed in terms of mathematical descriptions and numerical simulations of the SPR curve. The response theory of the absorption-based SPR sensing is based on the expansion of Kretchmann's SPR theory into the case in which optical absorption in the sensing layer is expressed by the Lorentz model. The numerical simulations were performed using a three-layer Fresnel equation of p-polarization. It was found that SPR curve behavior of the absorption-based SPR sensor depends on the frequency relation between the light source and the optical absorption and the thickness of the metal layer. The SPR curve behavior is divided into three types according to the large, small, and equal relations between excitation and absorption frequencies. Each type of behavior is further divided into two types that are due to thin and thick metal layers. The theory of this new type of sensor based on optical absorption ...
TL;DR: In this paper, a concept to electrically control the scattering of light is introduced, which is to embed noble metal nanoparticles in an electro-optical material such as a liquid crystal in order to induce a spectral shift of the particle plasmon resonance by applying an electric field.
Abstract: A concept to electrically control the scattering of light is introduced. The idea is to embed noble metal nanoparticles in an electro-optical material such as a liquid crystal in order to induce a spectral shift of the particle plasmon resonance by applying an electric field. Light scattering experiments on single gold nanoparticles show that spherically shaped nanoparticles become optically spheroidal when covered by an anisotropic liquid crystal. The two particle plasmon resonances of the optically spheroidal gold nanoparticles can be spectrally shifted by up to 50 meV when electric fields of more than 10 kV/cm are applied.
TL;DR: In this paper, a surface plasmon resonance (SPR) detection with a biospecific sensor chip is described. But the method is not suitable for the detection of biomolecular interactions.
Abstract: A recent development in instruments to investigate biomolecular interactions is surface plasmon resonance (SPR) detection with a biospecific sensor chip. In this method, a probe (P) or a target molecule (T) is bound to a gold-plated cell and a solution containing the other molecule is passed over it. Light is beamed through a prism and strikes the glass surface of the flow cell containing the sample at an angle, such that the beam is totally reflected. At a particular wavelength and incident angle between the beam and glass, a surface plasmon wave of excited electrons (plasmon resonance) is produced at the gold layer and is detected as a reduced intensity of the reflected light beam. By measuring the deflection of the beam, binding of P &T can be easily quantitated. This article describes the mechanism and applicatioins of the SPR technique.
TL;DR: A fiber optic surface plasmon resonance (SPR) biosensor for detection of Staphylococcal enterotoxin B is reported and is demonstrated to be able to detect ng/ml concentrations of SEB in less than 10 min.
TL;DR: In this paper, the polarization-dependent scattering of light from homogeneous and multisegment silver, gold, and nickel nanowires is analyzed using an optical microscope configured for single particle spectroscopy.
Abstract: We present an experimental study of the polarization-dependent scattering of light from homogeneous and multisegment silver, gold, and nickel nanowires. The metallic nanowires are prepared within a polycarbonate membrane template by a combination of electroplating (gold and nickel) and electroless (silver) growth processes. The size range of the nanowire segments is such that surface plasmon resonances are supported, dominating the optical spectra. We characterize the light scattering properties of individual composite nanowires using an optical microscope configured for single particle spectroscopy. Because of the scattering efficiency associated with the plasmon resonance, very narrow (∼30 nm diameter) nanowires can be readily observed under white-light illumination, with the spectral characteristics of each subsection easily distinguishable. Because of their compactness, these simply prepared multiisegment plasmon resonant nanowires are capable of hosting a large number of segment sequences over a comp...
TL;DR: In this article, the optical response of surface plasmon resonance (SPR) sensors based on colloidal metal nanoparticles using extended Mie theory is modeled using the particle adsorption layer, the surrounding medium as well as particle-particle and particle-substrate electromagnetic coupling effects.
Abstract: We model the optical response of surface plasmon resonance (SPR) sensors based on colloidal metal nanoparticles using extended Mie theory. The theoretical description includes the particle adsorption layer, the surrounding medium as well as particle–particle and particle–substrate electromagnetic coupling effects. We obtain quantitative agreement with recently reported experimental results on gold nanoparticle SPR sensors, indicating the possibility to perform accurate a priori estimates of detector sensitivity for different particle sizes and compositions in a variety of electromagnetic environments. The possibility to increase sensitivity by using non-spherical silver particles as SPR sensors is discussed.
TL;DR: In this paper, a two-channel surface plasmon resonance (SPR) biosensors were used for real-time monitoring of Staphylococcus aureus enterotoxin B (SEB).
01 Jan 2002
TL;DR: An SPR sensor system based on a prototype two-channel system similar to the single channel Spreeta devices, which provides a reference channel to compensate for bulk refractive index (RI), non-specific binding and temperature variations.
Abstract: Surface plasmon resonance (SPR) biosensors offer the capability for continuous real-time monitoring. The commercial instruments available have been large in size, expensive, and not amenable to field applications. We report here an SPR sensor system based on a prototype two-channel system similar to the single channel Spreeta devices. This system is an ideal candidate for field use. The two-channel design provides a reference channel to compensate for bulk refractive index (RI), non-specific binding and temperature variations. The SPR software includes a calibration function that normalizes the response from both channels, thus enabling accurate referencing. In addition, a temperature-controlled enclosure utilizing a thermo-electric module based on the Peltier effect provides the temperature stability necessary for accurate measurements of RI. The complete SPR sensor system can be powered by a 12V battery. Pre-functionalized, disposable, gold-coated thin glass slides provide easily renewable sensor elements for the system. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detectable at sub-nanomolar levels and with amplification at femtomolar levels. A regeneration procedure for the sensor surface allowed for over 60 direct detection cycles in a 1-month period.
TL;DR: In this article, an optical fiber surface plasmon resonance (SPR) sensor was developed for the detection of hydrogen leakages using a thin palladium layer deposited on the bare core of a multimode fiber.
Abstract: An optical fibre surface plasmon resonance (SPR) sensor has been developed for the detection of hydrogen leakages. A thin palladium layer deposited on the bare core of a multimode fibre was used as the transducer. In this device, modification of the SPR is due to variation in the complex permittivity of palladium in contact with gaseous hydrogen. This effect is enhanced by using selective injection of high-order modes in the fibre via a collimated beam with non-normal incidence on the input end of the fibre. Measurements of concentrations as low as 0.8% of hydrogen in pure nitrogen have been found to be possible. The response time varies between 3 s for pure hydrogen and 300 s for the lowest concentrations. Such a large range can be explained by the two different crystallographic phases of the palladium-hydrogen system. Moreover, the response of the sensor is dependent on the length of the sensing area. In preliminary experiments, it has been possible to split the sensing area in order to achieve a two-point detection device.
TL;DR: In this article, a simple quasistatic treatment for the plasmon resonance spectra of nanoparticle rod−rod and rod−sphere pairs is presented, where the spectral changes that occur as a result of interparticle interaction are different for end-to-end (axial) and side-toside (lateral) orientations.
Abstract: A simple quasistatic treatment for the plasmon resonance spectra of nanoparticle rod−rod and rod−sphere pairs is presented. Spectra are calculated for gold particle pairs at different distances and mutual orientations. For rod−rod and rod−sphere pairs, the spectral changes that occur as a result of interparticle interaction are different for end-to-end (axial) and side-to-side (lateral) orientations. Axial interactions generally lead to a red shift of the most intense (longitudinal axis) plasmon resonance band. Lateral interactions usually lead to a blue shift of the main plasmon band. In general, lateral orientation yields more pronounced spectral changes than the axial case, especially as the aspect ratio of the rod member(s) increases.
TL;DR: SPR sensors can detect biologically significant signals in a real-time manner from the interactions between cells and molecules reactive to the cells, using mast cells and mast cell-reactive antigens.
TL;DR: Gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies.
Abstract: Citrate-capped gold nanoparticles as well as planar gold surfaces can be efficiently grafted with a covalently attached polymer monolayer a few nanometers thick, by simple contact of the metal surface with dilute aqueous solutions of hydrophilic polymers that are end-capped with disulfide moieties, as shown by UV/vis absorption, dynamic light scattering, and surface plasmon resonance studies. The hydrophilic polymer-coated gold colloids can be freeze-dried and stored as powders that can be subsequently dissolved to yield stable aqueous dispersions, even at very large concentrations. They allow for applying filtrations, gel permeation chromatography, or centrifugation. They do not suffer from undesirable nonspecific adsorption of proteins while allowing the diffusion of small species within the hydrogel surface coating. In addition, specific properties of the original hydrophilic polymers are retained such as a lower critical solution temperature. The latter feature could be useful to enhance optical responses of functionalized gold surfaces toward interaction with various substrates.
TL;DR: In this article, it was shown that the thermodynamic stability and nature of binding are dictated by the availability of d-orbitals for back-bonding, while the surface plasmon resonance (SPR) band frequency is largely modulated by the electrostatics of the ligand.
Abstract: Colloidal gold nanoparticles can be isolated from excess citric acid buffer by electrolyte-induced precipitation from water solutions through the addition of oxyanions This allows the nanomaterials to be isolated as freely soluble powders that can be readily redissolved in water or buffer solution for other applications, such as biolabeling Analysis by UV−vis and FTIR spectroscopy allows direct analysis of the oxyanion interaction at the surface of the Au nanomaterial For a series of oxyanions, the order of thermodynamic stability is CO32- CO32- > SO42- These studies indicate that the thermodynamic stability and nature of binding are dictated by the availability of d-orbitals for back-bonding, while the surface plasmon resonance (SPR) band frequency is largely modulated by the electrostatics of the ligand Comparison of the extinction coefficient of the SPR band to Mie theory predictions further illustrates the effect of lig