Electric field effects on adsorption/desorption of proteins and colloidal particles on a gold film observed using surface plasmon resonance
Richard A. MorrowDavid R. McKenzieMarcela M.M. BilekChristopher MacDonaldM. StindtG. AnetsbergerAimée Martin
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Surface-plasmon-resonance (SPR) sensors are widely used in biological, chemical, medical, and environmental sensing. SPR sensors supporting two surface-plasmon modes can differentiate surface binding interactions from bulk index changes at a single sensing location. We present a new approach to dual-mode SPR sensing that offers improved differentiation between surface and bulk effects. By using an angular interrogation, both long- and short-range surface plasmons are simultaneously excited at the same location and wavelength but at different angles. Initial experiments indicate that angular interrogation offers at least a factor of 3.6 improvement in surface and bulk cross-sensitivity compared to wavelength-interrogated dual-mode SPR sensors.
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Abstract Peroxidases are widespread heme‐containing enzymes able to catalyze the oxidation of a large array of organic substrates. There is growing interest in the measurements of peroxidase activity. We noticed that many substrates used in the routine assays for the biological and cytological determinations of peroxidase could be oxidized by lipoxygenase. We found interesting to set up a procedure to detect selectively peroxidase. In the present note, we report a fluorometric test for peroxidase detection using phenolic compounds or hydroxycoumarins.
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In this study, the optical properties of localized surface plasmon resonance sensor using optical fiber was analyzed as the variation of a size and surface density of gold nano particles on the etched optical fiber surface. It is shown that a size and surface density of gold nano particles on optical fiber surface are controlled by $Na_3$ citrate quantity and pH of gold colloid solution. To measure the sensitivity, peak wavelength of absorbance spectrum was detected as the reflective index of the solution. The sensor sensitivity is linearly dependent on the size and surface densities of gold nano particles from the results of optical experiments.
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We have systematically investigated the localized surface plasmon resonance (LSPR) of the silver nanoparticles by using electron energy loss spectroscopy (EELS) and optical simulation based on boundary element methods with respect to the diameter and the impact parameter variations. The both peaks of EELS and optical curve were occurred from 3.2 to 3.8 eV. Interestingly, we found two types of plasmon modes. At the impact parameter from 0 to R, the plasmon showed the properties as bulk plasmon, while at the greater value than R it showed the surface plasmon mode. This result showed the EELS simulation was better to observe a high-order of LSPR spectra than optical simulation. High-order was originated from a higher multipolar mode and weak interaction in surface plasmon phenomenon. As shown above, the EELS measurement can detect a high-order mode of LSPR than the optical measurement.
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This paper presents a new method to prepare localized surface plasmon resonance(LSPR) sensing film by self-assembly of polyelectrolyte. The optical signal arises from the dependence of the peak intensity and position of the localized surface plasmon spectrum of gold nanoparticles upon the refractive index of the surrounding medium. By using an electrostatic layer-by-layer assembly approach-PDDA/PSS/PVTC, 28 nm diameter colloidal gold nanoparticles are immobilized upon a glass substrate. The method yields a LSPR sensing film with good reproducibility and excellent stability. The spectroscopic response of the LSPR sensing film was investigated. The shift in the peak extinction wavelength and the change in the corresponding intensity of the LSPR band as a function of the refractive index of the solution are 71 nm/RIU and 0.21 a.u./RIU, respectively. The penetration depth of the electromagnetic field excited by LSPR upon the response of the sensing film is estimated to be about 16 nm.
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A surface plasmon resonance(SPR) sensor system was set up.Different Au films and nano-Au colloidal solutions with different concentration were prepared and characterized using the established SPR instrument.The refractive index of colloidal Au with different concentration was obtained from the SPR spectrum.
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Nanoparticles are finding more practical applications in various fields of human activity, including veterinary and medicine. Due to the fact that the effectiveness of colloidal solutions of nanoparticles is directly related to their aggregate state, convenient methods for assessing the physicochemical characteristics of such preparations is of high priority. Nanoparticles have unique optical properties that depend on their size and shape. They can be determined by the refractive index of light on the surface of nanoparticles in a phenomenon known as plasmon resonance, which makes the UV-Vis spectroscopy a valuable tool for studying and evaluating the properties of nanomaterials. Optical characteristics of NPs colloidal solutions of noble metals (silver) or bioelements (copper, silicon dioxide) were determined at various wavelengths (nm): 300-800 nm. The surface plasmon resonance has been found in all test preparations, while all of them exhibited obvious nonlinear optical properties. The most pronounced plasmon resonance peak was found in the colloidal solution of silver NPs within a wavelength of 420 nm. In the case of a colloidal solution of copper NPs, the peak of plasmon resonance was less pronounced and had a red shift (peak at 560 nm). In the colloidal solution of silicon dioxide, the plasmon resonance was less pronounced than in other test preparations, being shifted to the blue side of the spectrum (360 nm). UV-Vis spectroscopy of metal NPs requires further studies to assess their stability and influence of various external factors on their activity
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Gold nanoparticles (Au NPs) have been attracting more attention because they have many color varieties in the visible region based on plasmon resonance, which is due to the collective oscillation of the electrons at the surface of the nanoparticles. We prepared 6 nm Au NPs to modify the surface of the glass substrate. Surface plasmons resonance of Au NPs in toluene is between 500 nm and 600 nm. When Au NPs are modified on the glass substrate, the peak of surface plasmons resonance of Au NPs is shifted. We employed spectral ellipsometry to detect optical properties. Then the characteristics of surface plasmons resonance of Au NPs is determined by reflective index. The performance of surface plasmons resonance of Au NPs on the glass substrate is simulated and shown.
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