Showing papers on "Surface plasmon resonance published in 2000"
TL;DR: In this article, the physical origin of surface plasmon absorption in gold nanoparticles with emphasis on the Mie and also the Maxwell-Garnett theory is discussed. And the effects of particle size and shape on the resonance condition are reviewed.
Abstract: Driven by the search for new materials with interesting and unique properties and also by the fundamental question of how atomic and molecular physical behaviour develops with increasing size, the field of nanoparticle research has grown immensely in the last two decades. Partially for these reasons, colloidal solutions of metallic (especially silver and gold) nanoparticles have long fascinated scientists because of their very intense colours. The intense red colour of colloidal gold nanoparticles is due to their surface plasmon absorption. This article describes the physical origin of the surface plasmon absorption in gold nanoparticles with emphasis on the Mie and also the Maxwell-Garnett theory and reviews the effects of particle size and shape on the resonance condition. A better understanding of the relationship between the optical absorption spectrum (in particular, the plasmon resonance) and such particle properties as its dimensions or surrounding environment can prove fruitful for the use of the ...
2,007 citations
TL;DR: The wavelength corresponding to the extinction maximum, λmax, of localized surface plasmon resonance (LSPR) of silver nanoparticle arrays fabricated by nanosphere lithography (NSL) can be systematically tuned from ∼400 nm to 6000 nm as discussed by the authors.
Abstract: The wavelength corresponding to the extinction maximum, λmax, of the localized surface plasmon resonance (LSPR) of silver nanoparticle arrays fabricated by nanosphere lithography (NSL) can be systematically tuned from ∼400 nm to 6000 nm. Such spectral manipulation was achieved by using (1) precise lithographic control of nanoparticle size, height, and shape, and (2) dielectric encapsulation of the nanoparticles in SiOx. These results demonstrate an unprecedented level of wavelength agility in nanoparticle optical response throughout the visible, near-infrared, and mid-infrared regions of the electromagnetic spectrum. It will also be shown that this level of wavelength tunability is accompanied with the preservation of narrow LSPR bandwidths (fwhm), Γ. Additionally, two other surprising LSPR optical properties were discovered: (1) the extinction maximum shifts by 2−6 nm per 1 nm variation in nanoparticle width or height, and (2) the LSPR oscillator strength is equivalent to that of atomic silver in gas or...
1,207 citations
TL;DR: A new approach to ultrasensitive detection of DNA hybridization based on nanoparticle-amplified surface plasmon resonance (SPR) is described, with a greater than 10-fold increase in angle shift and a more than 1000-fold improvement in sensitivity for the target oligonucleotide as compared to the unamplify binding event.
Abstract: A new approach to ultrasensitive detection of DNA hybridization based on nanoparticle-amplified surface plasmon resonance (SPR) is described. Use of the Au nanoparticle tags leads to a greater than 10-fold increase in angle shift, corresponding to a more than 1000-fold improvement in sensitivity for the target oligonucleotide as compared to the unamplified binding event. This enhanced shift in SPR reflectivity is a combined result of greatly increased surface mass, high dielectric constant of Au particles, and electromagnetic coupling between Au nanoparticles and the Au film. DNA melting and digestion experiments further supported the feasibility of this approach in DNA hybridization studies. The extremely large angle shifts observed in particle-amplified SPR make it possible to conduct SPR imaging experiments on DNA arrays. In the present work, macroscopic 4 × 4 arrays were employed, and a ∼10 pM limit of quantitation was achieved for 24-mer oligonucleotides (surface density ≤8 × 108 molecules/cm2). Even...
909 citations
TL;DR: The number and diversity of surface plasmon resonance (SPR) biosensor applications continue to increase, and innovations in instrument and sensor chip technology, experimental methodology, and data analysis are making it possible to examine a wider variety of biomolecular interactions in greater mechanistic detail.
676 citations
TL;DR: A strong dependence of the plasmon lifetime and resonance wavelength on the grating constant is found and it is found that gold nanoparticles arranged in regular two-dimensional patterns have regular grating effects.
Abstract: We probe the influence of grating effects on plasmon excitations in gold nanoparticles arranged in regular two-dimensional patterns. Samples produced by electron-beam lithography are investigated by femtosecond time-resolved and spectroscopic methods. We find a strong dependence of the plasmon lifetime and resonance wavelength on the grating constant.
575 citations
TL;DR: Folate-linked nanoparticles represent a potential new drug carrier for tumor cell-selective targeting in PEG-coated biodegradable nanoparticles coupled to folic acid to target the folate-binding protein.
536 citations
TL;DR: A review of the diversity of SPR analysis shows the broad range of techniques that are routinely used alongside SPR analysis, and particular emphasis is given to the use of SPR as a complimentary tool.
529 citations
TL;DR: Using a combination of the quartz crystal microbalance and surface plasmon resonance techniques, the spontaneous formation of supported lipid bilayers from small unilamellar vesicles is studied for the first time.
Abstract: Using a combination of the quartz crystal microbalance and surface plasmon resonance techniques, we have studied the spontaneous formation of supported lipid bilayers from small (approximately 25 nm) unilamellar vesicles. Together these experimental methods measure the amount of lipid adsorbed on the surface and the amount of water trapped by the lipid. With this approach, we have, for the first time, been able to observe in detail the progression from the adsorption of intact vesicles to rupture and bilayer formation. Monte Carlo simulations reproduce the data.
449 citations
TL;DR: The absorption spectra of the the gold colloid monolayers, which were immersed in liquid samples or coated with thin films, were measured and increases of both the resonance wavelength and the absorbance as the refractive indices of the sample liquids or the thickness of the coated films increased.
Abstract: A new optical sensor that uses local plasmon resonance is proposed. A peak that is due to the local plasmon resonance appears in the absorption spectrum of a gold colloid suspension in the visible region, and its height and wavelength depend on the refractive index of the suspension. These properties are used for optical sensors. We used gold colloid monolayers in which colloidal gold particles a few tens of nanometers in diameter were immobilized upon a glass slide by a functional organic coupling agent. We measured the absorption spectra of the the gold colloid monolayers, which were immersed in liquid samples or coated with thin films. We observed increases of both the resonance wavelength and the absorbance as the refractive indices of the sample liquids or the thickness of the coated films increased. The proportional constants of the resonance wavelength to the film thickness were 3.6 and 5.7 for a 13.9- and a 20.2-nm gold colloid monolayer, respectively.
431 citations
TL;DR: In this article, a simple, fast, and flexible technique to measure optical scattering spectra of individual metallic nanoparticles was developed to measure the effect of particle diameter on the dephasing time of the particle plasmon resonance in gold nanoparticles.
Abstract: We have developed a simple, fast, and flexible technique to measure optical scattering spectra of individual metallic nanoparticles. The particles are placed in an evanescent field produced by total internal reflection of light from a halogen lamp in a glass prism. The light scattered by individual particles is collected using a conventional microscope and is spectrally analyzed by a nitrogen-cooled charge-coupled-device array coupled to a spectrometer. This technique is employed to measure the effect of particle diameter on the dephasing time of the particle plasmon resonance in gold nanoparticles. We also demonstrate the use of this technique for measurements in liquids, which is important for the potential application of particle plasmons in chemical or biological nanosensors.
394 citations
TL;DR: A new type of biosensor element for detecting proteins in solution at nanomolar concentrations tethered to the lumen of the transmembrane protein pore allows detection of a protein analyte at the single-molecule level, facilitating both quantification and identification through a distinctive current signature.
Abstract: Here we describe a new type of biosensor element for detecting proteins in solution at nanomolar concentrations. We tethered a 3.4 kDa polyethylene glycol chain at a defined site within the lumen of the transmembrane protein pore formed by staphylococcal α-hemolysin. The free end of the polymer was covalently attached to a biotin molecule. On incorporation of the modified pore into a lipid bilayer, the biotinyl group moves from one side of the membrane to the other, and is detected by reversible capture with a mutant streptavidin. The capture events are observed as changes in ionic current passing through single pores in planar bilayers. Accordingly, the modified pore allows detection of a protein analyte at the single-molecule level, facilitating both quantification and identification through a distinctive current signature. The approach has higher time resolution compared with other kinetic measurements, such as those obtained by surface plasmon resonance.
TL;DR: This review highlights many recent developments in SPR-based immunoassay, functionalizations of the gold surface, novel receptors in molecular recognition, and advanced techniques for sensitivity enhancement, and describes the challenge of current problems and some insights toward the future technologies.
TL;DR: In this article, the pump-probe signals near the plasmon resonance of the nanoparticles reveal the importance of electron-electron scattering during several hundreds of femtoseconds.
TL;DR: A quantitative study of the kinetics of formation for a two-component tethered ssDNA monolayer film using in situ two-color surface plasmon resonance (SPR) spectroscopy, which can be understood in terms of a simple physical model and self-consistent parameters.
Abstract: We report a quantitative study of the kinetics of formation for a two-component tethered ssDNA monolayer film using in situ two-color surface plasmon resonance (SPR) spectroscopy. The attachment of the DNA to gold is facilitated by functionalization at the 5‘ end with a thiol group connected by a hexamethylene linker (HS-C6-ssDNA). Detailed data analysis is performed by quantitative comparison of the DNA coverage versus time kinetic data obtained from SPRS with numerical solutions for the differential equations for simultaneous adsorption, desorption, and diffusion at the interface. The kinetics of adsorption of HS-C6-ssDNA onto bare gold as well as the kinetics of loss of HS-C6-ssDNA from the surface during subsequent treatment with mercaptohexanol can be understood in terms of a simple physical model and self-consistent parameters. The kinetics of HS-C6-ssDNA adsorption on bare gold are compared to the kinetics of hybridization of surface-attached thiolated ssDNA with the fully complementary ssDNA in fr...
TL;DR: Improvements in instrument hardware, experimental design and data processing have made it possible to use surface plasmon resonance (SPR) biosensor technology in the discovery and development of small-molecule drugs and it is poised to play a significant role in the pharmaceutical industry.
TL;DR: At resonance frequencies, extremely large enhancements of the electromagnetic fields occur near the surface of the particle, with amplitudes several hundred-fold that of the incident field.
Abstract: We study the plasmon resonances of 10–100(nm) two-dimensional metal particles with a non-regular shape. Movies illustrate the spectral response of such particles in the optical range. Contrary to particles with a simple shape (cylinder, ellipse) non-regular particles exhibit many distinct resonances over a large spectral range. At resonance frequencies, extremely large enhancements of the electromagnetic fields occur near the surface of the particle, with amplitudes several hundred-fold that of the incident field. Implications of these strong and localized fields for nano-optics and surface enhanced Raman scattering (SERS) are also discussed.
TL;DR: The dynamic properties of GFP alone and fused to a single chain antibody raised against lipopolysaccharide of the outer cell wall of Gram-negative bacteria were investigated and the scFv moiety was functional as was proven in binding assays.
TL;DR: In this article, the plasmon resonance effect was used to enhance the efficiency of photochemical cells, and the photoresponse in the visible region increased as the mass-equivalent Ag-island film thickness, tAg, increased to 3.3
TL;DR: A polyclonal anti-aflatoxin B(1) antibody was produced and was found to be regenerable using an organic solution consisting of 1 M ethanolamine with 20% (v/v) acetonitrile, pH 12.0, which combined high ionic strength and extreme pH, as well as chaotrophic properties and allowed the development of an inhibitive immunoassay.
Abstract: Aflatoxins are a group of highly toxic fungal secondary metabolites that occur in Aspergillus species and may contaminate foodstuffs and feeds. Two different anti-aflatoxin B1 antibodies were examined to develop a surface plasmon resonance (SPR)-based immunoassay to aflatoxin B1. A conjugate consisting of aflatoxin B1−bovine serum albumin (BSA) was immobilized on the dextran gel surface. Competition between immobilized aflatoxin B1 conjugate and free aflatoxin B1 in solution for binding to antibody injected over the surface formed the basis for the assay. Regeneration of the antibody from the immobilized conjugate surface is essential for the development of such an inhibitive immunoassay. Problems were encountered with the regeneration of the sensor surface, due to the high-affinity binding of the antibodies. Conventional regeneration solutions consisting of low concentrations of NaOH and HCl worked to a degree, but regeneration was at the expense of the integrity of the immobilized conjugate. A polyclona...
TL;DR: In this paper, a study of the surface-enhanced infrared absorption (SEIRA) spectroscopy of para-nitrobenzoic acid (PNBA) adsorbed on thermally evaporated silver films has been conducted to determine the effect of film architecture on the magnitude of SEIRA enhancement.
Abstract: A study of the surface-enhanced infrared absorption (SEIRA) spectroscopy of para-nitrobenzoic acid (PNBA) adsorbed on thermally evaporated silver films has been conducted to determine the effect of film architecture on the magnitude of the SEIRA enhancement. Ordered arrays of uniformly sized silver nanoparticles, termed periodic particle arrays (PPAs), were prepared on several different infrared transparent substrates (germanium, silicon, and mica) by nanosphere lithography (NSL). It was found that the ordered arrays deposited by NSL produced well-defined and intense surface plasmon resonance (SPR) bands in the infrared at frequencies between 1500 and 4000cm -1. The peak frequency of these infrared SPR bands depended on the array architecture and the substrate material. By appropriate design of the nanoparticle array, the infrared SPR band can be made to be coincident with the SEIRA sensitive infrared bands of the PNBA. The trends in the infrared SPR peak frequencies and band shapes were consistent with predictions from electrodynamic theory. The SEIRA responses per unit area of deposited metal obtained with the PPA-type films were at best comparable to results obtained with disordered silver and gold films deposited on the same substrate materials by thermal evaporation (i.e., in the absence of any NSL masking spheres). The results of this study are most consistent with theories and models that attribute SEIRA to the dielectric constant and optical extinction spectrum of the metal film. Index Headings: Infrared spectroscopy; Surface-enhanced infrared absorption; Plasmon; SEIRA.
TL;DR: The refractive index increments (RIIs) of several important low-molecular-weight compounds that bind to DNA or RNA were determined with a differential refractometer for correction of data obtained on surface plasmon resonance (SPR) biosensors to demonstrate that RII values for small molecules can be significantly different than those of protein or nucleic acid receptors.
TL;DR: A novel sensor chip for use in surface plasmon resonance (SPR) biosensors has been developed to capture vesicles which may contain membrane-bound receptors and binding of cholera toxin to captured vesicle containing ganglioside GM(1) was demonstrated using SPR.
TL;DR: Two different previously unobserved decay channels of the collective excitation have been identified, namely, decay into one or several single-particle excitations of the surface plasmon in silver nanoparticles on graphite.
Abstract: Multiphoton photoelectron spectroscopy reveals the multiple excitation of the surface plasmon in silver nanoparticles on graphite. Resonant excitation of the surface plasmon with 400 nm femtosecond radiation allows one to distinguish between photoemission from the nanoparticles and the substrate. Two different previously unobserved decay channels of the collective excitation have been identified, namely, decay into one or several single-particle excitations.
TL;DR: In this article, a multiple wavelength surface plasmon resonance apparatus for imaging applications is presented, which can be used for biosensing, e.g., for monitoring of chemical and biological reactions in real time with label-free molecules.
Abstract: A new, multiple wavelength surface plasmon resonance apparatus for imaging applications is presented. It can be used for biosensing, e.g., for monitoring of chemical and biological reactions in real time with label-free molecules. A setup with a fixed incident angle in the Kretschmann configuration with gold as the supporting metal is described, both theoretically and experimentally. Simulations of the sensor response based on independently recorded optical (ellipsometric) data of gold show that the sensitivity for three-dimensional recognition layers (bulk) increases with increasing wavelength. For two-dimensional recognition layers (adlayer) maximum sensitivity is obtained within a limited wavelength range. In this situation, the rejection of bulk disturbances, e.g., emanating from temperature variations, decreases, with increasing wavelength. For imaging surface plasmon resonance the spatial resolution decreases with increasing wavelength. Hence, there is always a compromise between spatial resolution, bulk disturbance rejection, and sensitivity. Most importantly, by simultaneously using multiple wavelengths, it is possible to maintain a high sensitivity and accuracy over a large dynamic range. Furthermore, our simulations show that the sensitivity is independent of the refractive index of the prism. (C) 2000 American Institute of Physics. [S0034-6748(00)02909-9].
TL;DR: It is demonstrated here that a high-resolution multiwavelength SPR technique can measure the electronic states of the molecules and thus allow direct identification of the atoms or molecules through surface plasmon resonance spectroscopy.
Abstract: To date, surface plasmon resonance (SPR) spectroscopy identifies molecules via specific bindings with their ligands immobilized on a surface. We demonstrate here that a high-resolution multiwavelength SPR technique can measure the electronic states of the molecules and thus allow direct identification of the molecules. Using this new capability, we have studied the electronic and conformational differences between the oxidized and reduced states of cytochrome c immobilized on a modified gold electrode. When the wavelength of the incident light is far away from the optical absorption bands of the protein, a ∼0.008° decrease in the resonance angle, due to a conformational change, occurs as the protein is switched from the oxidized to reduced states. When the wavelength is tuned to the absorption bands, the resonance angle oscillates at the wavelengths of the absorption peaks, which provides electronic signatures of the protein.
TL;DR: An approach to enlarge preformed colloidal Au nanoparticles in solution based on the Au colloidal surface-catalyzed reduction of Au3+ by NH2OH (seeding) has been adapted to 12-nm-diameter colloidal AU nanoparticles immobilized in monolayers and multilayers.
Abstract: An approach to enlarge preformed colloidal Au nanoparticles in solution based on the Au colloidal surface-catalyzed reduction of Au3+ by NH2OH (“seeding”) has been adapted to 12-nm-diameter colloidal Au nanoparticles immobilized in monolayers and multilayers. Bulk characterization of the ensuing films was carried out by atomic absorption, UV−vis−near-IR optical spectroscopy, cyclic voltammetry, and dc resistance measurements. Exposure of a 12-nm-diameter Au colloid monolayer on organosilane-modified glass surfaces to NH2OH/Au3+ leads to rapid particle growth and coalescence: after roughly 5−10 min, the optical and electrical properties closely resemble that of conductive Au thin films prepared by evaporation. Evolution of the nanometer-scale architecture was followed using atomic force microscopy (AFM), surface-enhanced Raman scattering (SERS), surface plasmon resonance (SPR), and field emission scanning electron microscopy (FE-SEM), leading to the following key findings: (i) Seeding of surface-confined...
TL;DR: In this article, surface plasmon excitation and surfaceenhanced Raman scattering (SERS) were investigated for periodic grating-type substrates such as binary silver gratings and silver on silica.
Abstract: Surface plasmon excitation and surface-enhanced Raman scattering (SERS) are investigated for periodic grating-type substrates such as binary silver gratings and silver gratings on silica. Electromagnetic near fields are calculated by an efficient implementation of a Rayleigh-expansion technique for rectangular-groove gratings. Far-field signals of Raman-active molecules adsorbed at the grating surface are determined by application of the Lorentz reciprocity theorem. SERS enhancement factors are considered for different types of gratings and for structures with different dimensions with respect to both the intensity and angular width of the emitted Stokes light. Thus, consideration of plasmon resonance widths leads to optimum structures for periodic SERS substrates if realistic experimental configurations involving a lens for detection are taken into account. For binary silver gratings, optimum grating depths of more than 80 nm are proposed for SERS measurements in a realistic experimental configuration, whereas maximum SERS signals are emitted into a single direction at shallow gratings with depths between 10 nm and 20 nm. Furthermore, silica gratings with isolated silver layers are superior to binary silver gratings. Due to both the large intensity and angular width of the emitted signals, SERS enhancement factors are additionally increased on such structures.
TL;DR: Surface plasmon resonance (SPR)-based biosensors were investigated with a view to providing a portable, inexpensive alternative to existing technologies for "real-time" biomolecular interaction analysis of whole cell-ligand interactions.
TL;DR: In this article, the ultrafast surface plasmon resonance nonlinearities and their connection with the conduction band electron dynamics are discussed in metal nanoparticles in the light of the results of high sensitivity femtosecond pump-probe experiments in silver nanoparticles embedded in a glass matrix.
TL;DR: In this paper, the phase reveals abrupt jumps in response to a minute increase in the effective thickness of a receptor layer that binds analyte particles on the sensor surface, which forms the basis for biosensing with sensitivity much higher as compared to traditional SPR sensors.
Abstract: Interferometry that detects the phase of a beam reflected under surface plasmon resonance (SPR) has been developed for bio and chemical sensing. The conditions have been found, under which the phase reveals abrupt jumps in response to a minute increase in the effective thickness of a receptor layer that binds analyte particles on the sensor surface. This forms the basis for biosensing with sensitivity much higher as compared to traditional SPR sensors. Besides, SPR interferometry (SPRI) provides spatial resolution at the micron scale. The enhanced sensitivity attributed to the phase jump and interferometric imaging of variations of the phase over the surface are demonstrated, which open up new avenues for micro-array biosensing.