Kretchmann Configuration Research Articles

Surface Plasmon Resonance Binding Study on the Interaction of Acetazolamide and Bovine Serum Albumin

Objective: Serum albumins are major plasma proteins in systemic blood circulation and act as transport proteins for endogenous and exogenous compounds such as drugs. In pharmaceutical applications, it is essential to characterize how drugs bind to serum albumin in the evaluation of drug candidates. Surface plasmon resonance (SPR) is fast, real-time, label-free optical based detection technique that offers the monitoring of molecular interactions, analyzing binding reactions and determining the affinity constants with real-time and high sensitivity. Acetazolamide (AZA) is used in the treatment of epilepsy and glaucoma.
 Methods: To determine the binding kinetics of AZA-Bovine serum albumin (BSA) interaction, (i) SPR gold sensor surface was functionalized, (ii) amine coupling procedure was applied to activate the surface group and BSA was immobilized on functionalized sensor surface, (iii) the concentration series of AZA (10, 25, 50, 75, 100, 150, 200 and 250 µM) was injected to SPR system and (iv) kinetic values were measured using the software of SPR system. 
 Results: 5 mM MUA was coated for surface functionalization. 250 µg/mL BSA as ligand, 30 µL/min flow rate, 1X PBS buffer (pH 7.4) and 10 mM acetate buffer (pH 5.2) as running and coupling buffers, respectively, were performed for SPR binding study. According to result, equilibrium constant (KD) of AZA-BSA was determined as 67.72 µM.
 Conclusion: In this study, we investigated the AZA-BSA binding interaction using SPR system based on Kretchmann configuration. The study designed with fast, label-free and real-time approach will provide valuable knowledge for pharmaceutical and clinical applications.

Power dependent surface plasmon coupled emission studies of metal-dielectric-metal planar structure

Surface plasmon coupled emission (SPCE) was demonstrated in Metal-Dielectric-Metal Planar (MDMP) structure by coupling MDMP structure to a hemicylindrical prism by Reverse Kretchmann configuration. Here silver and Fluorescein dye dispersed in polyvinyl Alcohol (PVA) were used as metal and dielectric layers respectively. Due to the combined effect of (1) confinement of photon mode within MDMP structure and (2) excitation of plasmon modes by RK configuration, highly directional and enhanced emission was observed. Dependence of SPCE emissions on input excitation power were studied. Higher dielectric thickness (∼600 nm) shows a better emission efficiency as compared to lower dielectric thickness (∼140 nm). Our simulation results show that a higher field distribution within MDMP structure for dielectric thickness of 600 nm resulting in better surface plasmon emission coupling and hence in better emission efficiency.

Multiperiodic nanohole array for high precision sensing

Abstract In this article, we present a multiperiodic nanohole array structure for improved sensing. The structure consists a series of rows of nanoholes, each having a different period in an ascending order. A monochromatic source illuminates the structure, and a resonance condition is met for the row having a momentum matching Bloch wave, which leads to extraordinary optical transmission. With this new plasmonic structure, the sensing signal can be retrieved using the spatial position of the transmission maxima. This setup requires a simple optical setup while achieving increased resolution and accuracy. A resolution of 4.6×10−6 refractive index units is achieved, which is comparable to surface plasmon resonance system based on the Kretchmann configuration.

Broadly tunable and bidirectional terahertz graphene plasmonic switch based on enhanced Goos-Hänchen effect

A plethora of research in recent years has been reported on free space optical switches based on Goos-Hänchen shift of the reflected light in the surface plasmon resonant systems. However, very little research has reported the tunable Goos-Hänchen shift in a fixed configuration. Thus, the main purpose of this investigation is to: (a) Bidirectional and tunable switch consisting of graphene plasmonic Kretchmann configuration is designed based on the analytical approaches at the terahertz frequency range, (b) Owing to tunable optical properties of graphene, the effect of different parameters including the chemical potential, temperature, and scattering time of graphene on the Goos-Hänchen shift are investigated. Our analytical calculations show that by strong coupling the incident light to the surface plasmons of the structure, giant Goos-Hänchen shift as high as 540 times the free space wavelength can be achieved. Furthermore, the application of white graphene as the substrate of graphene layer increases the propagation of the graphene surface plasmons while the required external voltage decreases. It is also shown that by considering the small change of chemical potential: Δμc = 0.4 eV (external voltage of ΔV = 0.5 V), the Goos-Hänchen shift variation of 440 λ0 (λ0 = 1.55 μm) can be easily provided. Finally, to verify our analytical results, the proposed structure is numerically simulated using finite-difference time-domain method. Based on these findings, this work present an alternate ways for improving both the tunability and magnitude of the Goos-Hänchen shift in a fixed configuration for bidirectional switching applications.

Monitoring Microalgae Population Growth by using Fe3O4 Nanoparticles-based Surface Plasmon Resonance (SPR) Biosensor

The population growth of microalgae has been successfully monitored by using the surface plasmon resonance (SPR)-based biosensor activated by using PEG-4000 functionalized Fe3O4 magnetic nanoparticles. The SPR-based biosensor in this work used Kretchmann configuration and Ha-Ne laser beam (λ = 633nm). The population of microalgae were estimated by using calibration curve. The shift of SPR angle happens due to the change of dielectric medium from prism/Au/air system to prism/Au/Fe3O4+PEG+microalgae/cover glass system. The change of dielectric medium occurs due to deposition of Fe3O4+PEG+microalgae samples that were monitored for seven days. The population of microalgae on the first day was estimated of 1188146 cell/ml and SPR angle had shifted from 42.80 to 69.00. The SPR angle shifted as much as 26.20. The population of microalga grew significantly on the third day as much as 1649106 cell/ml and the SPR angle had shifted 43.80 to 71.10. The SPR angle shifted as much as 27.30. On fourth to seventh day, the population of microalgae decreased. The population of microalgae on the seventh day was estimated of 1206961 cell/ml and the SPR angle had shifted from 44.00 to 68.80. The SPR angle shifted as much as 24.8 degrees. The shift of SPR angle was influenced by the population of microalgae so that the SPR-based biosensor has the potential for use in monitoring the microalgae population.

Angle modulated surface plasmon resonance spectrometer for refractive index sensing with enhanced detection resolution

We design and manufacture an angle modulated surface plasmon resonance (SPR) spectrometer with high detection resolution for refractive index sensing. The presented SPR spectrometer is based on a five-layer Kretchmann configuration. To enhance the sensitivity and resolution of the SPR spectrometer, we introduce a reference beam into the system, which has improved the stability of the system by nearly one order of magnitude. Numerical simulation and experimental study are presented and the results show that a sensitivity of 85 degrees/RIU (refractive index unit) and a good repeatability (standard deviation=3.7×10−6 RIU) have been achieved.

SURFACE PLASMON RESONANCE SENSOR OF SILVER FILM BASED ON KRETCHMANN CONFIGURATION

Performance of a surface plasmon resonance (SPR) sensor based on Kretchmann configuration for silver (Ag) film is evaluated via theoretical simulation. The film thickness and incident angle are varied to obtain the SPR wavelength in the range of 500-550 nm. Shift of SPR wavelength with refractive index of the dielectric defines the sensitivity whereas the resolution is obtained from the ratio of the instrumental resolution to the sensitivity. The SPR sensor shows increasing sensitivity for thicker film however the absorption magnitudes of such films are high and unfavourable for data acquisition. Film thickness of 45 nm and 50 nm which has good sensitivity and resolution with high absorbance magnitude of the SPR wavelength is the best thickness to be employed for sensing purpose.

Design of transverse magnetic-reflected polarizing film

We propose a wideband transverse magnetic-reflected polarizing film composed of Cr and SiO2. Based on the polarization characteristics of reflected light from Cr/SiO2 film, the film can serves as a polarizer to severely attenuate the transverse electric (TE)-polarized light and reflect the transverse magnetic (TM)-polarized light in a wavelength range from 600 to 900 nm. By suitably choosing the film thicknesses, the operation angles of such polarizers can be adjusted over a wide angle range greater than the critical angle of total reflection. Cr/SiO2 film has potential use in surface plasmon resonance (SPR) sensors based on Kretchmann configuration to form integrated structures.

Second harmonic generation in NLO polymers excited by Surface Plasmon enhanced electric field induced by femtosecond optical pulses

We will report second harmonic generation (SHG) in nonlinear optical (NLO) polymers excited by surface plasmon enhanced optical fields. The surface plasmon (SP) polariton was excited in an attenuated total reflection geometry having the Kretchmann configuration. The NLO polymers, consisting of Disperse Red1 as guest chromophores and poly (methyl methacrylate) as host materials, were coated upon the Ag layers. Our experimental results indicated that the SHG signal intensity from the polymer coated Ag films was more than 10 times higher than that from the non-coated Ag films. The SHG autocorrelation traces excited by SP-enhanced fields were also studied and the correlation time was shorter than 150 fs, the temporal resolutions of the present spectrometer.

Nanostructuring of Continuous Gold Film by Laser Radiation Under Surface Plasmon Polariton Resonance Conditions

The physical mechanisms of metallic nanoparticles formation by laser technology were studied. The system air/Au film/glass was irradiated by laser at the conditions of surface plasmon resonance. A surface electromagnetic wave was excited in Kretchmann configuration by the fundamental and second harmonics of the Q-switched YAG/Nd+3 laser with pulse power density close to the threshold of melting. Nanostructuring of Au film was observed only for the second harmonic (λ = 0.532 μm) irradiation at the surface plasmon polariton resonance (SPR) conditions. Estimations were done using the interference model of the differently directed plasmon polariton waves excited by a surface electromagnetic wave on the metal surface. It was shown that a regular pattern of locally heated spots can be formed in a metallic film by pulsed laser irradiation. The spatial distribution of this pattern is close to the period of interference. The observed effect of laser nanofragmentation is explained by the self-organization of plasmon polariton subsystem in the process of Au nanoparticles formation at high laser intensity levels. These methods open new possibilities for nanostructured surfaces formation utilizing simple self-organization processes.

On the implementation of nano-structured materials in surface plasmon resonance sensors

In this work, we review the implementation of nano-structured materials in surface plasmon resonance (SPR) sensors for the detection of adsorbed molecules. More specifically, we study nano-porous alumina films supported by gold (Au) or aluminum (Al) thin films in SPR sensors under the Kretchmann configuration. The enhanced response of such a sensor is calculated by theoretical simulation and is compared to the most widely used “classic” Au SPR sensor. It is concluded that both Al/nano-porous alumina and Au/nano-porous alumina setup provide better response than the “classic” Au SPR sensor with Au/nano-porous alumina setup providing the best response.

Real-Time Visualization Method of Surface Plasmon Resonance with Spectroscopic Attenuated Total Reflection

AbstractWe report the real-time visualization method of surface plasmon resonance with the spectroscopic attenuated total reflection. Recently, surface plasmon resonance (SPR) had been studied for plasmonics devices to construct faster processor in the electronic microprocessors. SPR is strong interaction between light and free electron near metal surface, which cause absorption of light due to its resonance. The behavior can be explained with Fresnel’s equation. As the wave number of light with a certain frequency is not matched with that of surface plasmon, a prism or a grating is used in order to compensate this mismatching. In the prism case, the wave number is changed by changing the incident angle to the metal surface inside the prism as ksp=n*k0sinθ, where ksp and k0 is the wave numbers of surface plasmon and incident light, respectively, n is the refractive index of the prism and θ is the incident angle to the metal surface inside the prism. Therefore, the SPR can be observed by absorption of light as functions of the wavelength and the incident angle. This resonance behavior as functions of the wavelength and the incident angle can be observed directly with a two-dimensional detector such as a CCD camera. As the two-dimensional SPR images for 50nm-thick silver films on the prism surface have been observed experimentally, they have good agreement with calculated ones. Kretchmann configuration using a glass prism and an approximately 50-nm-thick silver or gold film was often used in order to evaluate the optical constants of the film. Most of SPR signals had been measured with either angular or spectral dependence with this geometry. In the case of angular dependence, the monochromatic laser, e.g. He-Ne laser at 632.8nm, is often used for the incident light. One can measure reflection loss as a function of an incident angle in the total reflection region. Increase in the resonance angle of SPR is well known when the thin oxide film on the metal film. The two-dimensional image of SPR is called “surface plasmon spectral fingerprint”, because it can inform conditions of metal films whether they are reacted or oxidized. Many fingerprints are expected by changing the thickness of the coating layer on the silver surface. In our method, thin metal film on a prism was excited by focusing beam of white light. SPR was clearly visualized with a spectrometer equipped with a two-dimensional CCD detector in the coordination of the incident angle and the wavelength. Various metal films could be distinguished even in partially oxidized condition. This real-time SPR visualization method would be useful not only for monitoring of surface reaction but for fabricating plasmonic devices.

Effects of molecular orientation of fluorescently-labeled duplex DNA on emission anisotropy

The molecular orientation of Cy5-labeled target DNA hybridized on a probe DNA layer was studied on a planar waveguide in the Kretchmann configuration at various target DNA bulk concentration. Optical waveguide fluorescence spectroscopy (OWFS) was employed to evaluate the fluorescence emission anisotropy by analyzing two polarized modes, i.e., TM and TE modes propagating in a waveguide. In this way, the orientational order parameter S could be determined. It was found that the orientation of DNA duplex molecules is disordered at lower concentrations, while relatively ordered at higher concentrations.

Cyclic olefin copolymer (COC) 폴리머 프리즘을 사용한 광섬유 기반 표면 플라즈몬 공명 (SPR) 바이오 센서

A novel fiber optic surface plasmon resonance (SPR) sensor using cyclic olefin copolymer (COC) prism with the spectral modulation is presented. The SPR sensor chip is fabricated using the SU-8 photolithography, Ni-electroplating and COC injection molding process. The sidewall of the COC prism is partially deposited with Au/Cr (45/2.nm thickness) by e-beam evaporator, and the thermal bonding process is conducted for micro fluidic channels and optical fibers alignment. The SPR spectrum for a phosphate buffered saline (0.1.M PBS, pH.7.2) solution shows a distinctive dip at 1300.nm wavelength, which shifts toward longer wavelength with respect to the bovine serum albumin (BSA)concentrations. The sensitivity of the wavelength shift is <TEX>$1.16\;nm{\cdot}{\mu}g^{-1}{\cdot}{\mu}l^{-1}$</TEX>. From the wavelength of SPR dips, the refractive indices (RI) of the BSA solutions can be theoretically calculated using Kretchmann configuration, and the change rate of the RI was found to be <TEX>$2.3{\times}10^{-5}RI{\cdot}{\mu}g^{-1}{\cdot}l^{-1}$</TEX>. The realized fiber optic SPR sensor with a COC prism has clearly shown the feasibility of a new disposable, low cost and miniaturized SPR biosensor for biochemical molecular analyses.

Computer screen photo-excited surface plasmon resonance imaging

Angle and spectra resolved surface plasmon resonance (SPR) images of gold and silver thin films with protein deposits is demonstrated using a regular computer screen as light source and a web camera as detector. The screen provides multiple-angle illumination, p-polarized light and controlled spectral radiances to excite surface plasmons in a Kretchmann configuration. A model of the SPR reflectances incorporating the particularities of the source and detector explain the observed signals and the generation of distinctive SPR landscapes is demonstrated. The sensitivity and resolution of the method, determined in air and solution, are 0.145 nm pixel −1, 0.523 nm, 5.13 × 10 −3 RIU degree −1 and 6.014 × 10 −4 RIU, respectively, encouraging results at this proof of concept stage and considering the ubiquity of the instrumentation.

Polymeric electrooptic light modulator based on grating-coupled surface plasmon resonance

In summary, in this work, we demonstrated the application of the grating-coupled SPR for the fabrication of an EO light modulator. SPR-based EO modulators reported to date have mostly used the Kretchmann configuration. To the best of authors’ knowledge, this work reports the first fabrication and demonstration of a grating-coupled EO modulator. By switching on and off of the applied voltage of 5 V, the subsequent variation of SPR was observed clearly. It should be mentioned that currently our study was limited to show the feasibility of our concept. For practical applications, further optimization of SPR signal will be required, which is a subject of our ongoing research.

Numerical simulation of a D-type optical fiber sensor based on the Kretchmann's configuration and heterodyne interferometry

A theory of a D-type optical fiber sensor based on the Kretchmann's configuration and heterodyne interferometry is proposed. In the paper, we try to design a D-type optical fiber sensor, which is the Kretchmann's configuration of a three-layer scheme, and measure the phase difference variations instead of the light intensity. Therefore, its accuracy and resolution are very high. From numerical simulations, we can achieve the best sensitivity of the D-type optical fiber sensor by choosing suitable parameters, e.g., the thickness of the thin film layer of gold and the length of the sensor. The D-type fiber sensor has the tunable high sensitivity only if we choose different incident angle. Because the sensitivity of the sensor can reach a refractive index unit (RIU) of 2 × 10 −6 the D-type fiber sensor could be valuable for chemical, biological and biochemical sensing.

An absorption-based surface plasmon resonance sensor applied to sodium ion sensing based on an ion-selective optode membrane.

A surface plasmon resonance (SPR) sodium ion sensor using an ion optode membrane film was experimentally and theoretically described based on an absorption-based SPR principle proposed in our previous article (Kurihara, K; Suzuki, K. AnaL Chem. 2002, 74, 696-701). The sodium ion concentrations from 10(-6) to 10(-1) have been successfully determined not only by the resonance angle diagnosis of the SPR curve but also by the minimum reflectance one. The ion optode film was plasticized poly(vinyl chloride) including a neutral sodium ionophore, a pH-sensitive cationic dye, and an anionic additive. Its optical absorption intensity changed with the sodium ion concentrations. The SPR ion sensor physically measured the complex refractive index caused by the absorption in the ion optode film. We have exhaustively investigated the experimental response behavior of the SPR curve relative to the sodium ion concentrations by comparison with numerically simulated SPR curves using a three-layer Fresnel equation including experimental values for the sodium ion optode membrane film. As predicted by the absorption-based SPR principle, the SPR curve behavior of the SPR ion sensors depended on two factors: one was the relation between the excitation frequency of the light source and the absorption maximum frequency in the ion optode film while the other was the gold metallic thickness in the Kretchmann configuration. The concept and practical theory of an absorption-based SPR sensor not only have been proved by the experimental results of the SPR sodium ion sensor but also have successfully allowed flexible ion sensing in an SPR sensor, which would be very difficult without the absorption mechanism in the ion optode film.

Excitation of Surface Plasmon-Polariton Waves at a Semiconductor-Metal Interface

The excitation of surface plasmon-polariton waves propagating across an external magnetic field (Voigt geometry) in a semiconductor-metal structure by means of the attenuated total reflection method is investigated. The phase matching conditions for the surface waves excitation in the Kretchmann configuration are derived and analyzed. The effect of different nonlinearities on the excitation of the surface waves is studied as well.

Surface plasmon-polariton study of the optical dielectric function of zinc

The optical dielectric function of zinc is measured by excitation of surface plasmon-polaritons on a silica prism coated in MgF2 and zinc in the Kretchmann configuration and on a zinc-covered silica grating for a range of wavelengths in the visible spectrum. By exciting the surface plasmon at the zinc-MgF2 or zinc-grating interfaces, the zinc is protected from oxidization and contamination. Comparison of angle-dependent reflectivities with either Fresnel's theory or grating modelling theory gives both the real and imaginary parts of the dielectric function of the zinc over the visible spectrum. The results compare very favourably with those obtained by other workers using more conventional methods for samples held in vacuum.