Surface Plasmon Resonance Curve Research Articles

A theoretical design of evanescent wave biosensors based on gate-controlled graphene surface plasmon resonance

A surface plasmon resonance (SPR) sensor based on gate-controlled periodic graphene ribbons array is reported. Different from the conventional methods by monitoring reflectivity variations with respect to incident angle or wavelength, this approach measures the change in SPR curve against the variation of graphene chemical potential (via dynamically tuning the gate voltage) at both fixed incident angle and wavelength without the need of rotating mirror, tunable filter or spectrometer for angular or wavelength interrogation. Theoretical calculations show that the sensitivities are 36,401.1 mV/RIU, 40,676.5 mV/RIU, 40,918.2 mV/RIU, and 41,160 mV/RIU for analyte refractive index (RI) equal to 1.33, 1.34, 1.35 and 1.36; their figure of merit (1/RIU) are 21.84, 24, 23.74 and 23.69, respectively. Significantly, the enhancement in the non-uniform local field due to the subwavelength graphene ribbon resonator can facilitate the detection in redistribution of protein monolayers modeled as dielectric bricks.

A Simple Simulation of Surface Plasmon Resonance in The Kretschmann Configuration Using Google Sheets

This article describes a simple numerical simulation of three-layer surface plasmon resonance (SPR) in the Kretschmann configuration. The calculation was performed in Google Sheets, a web-based spreadsheet environment that functions similarly to Microsoft Excel where it is easily accessible for students via the internet. Specifically, Fresnel’s equations were utilized to calculate the intensity of the reflected light for the p-polarized incident light on a three-layer system. The complex functions were utilized to plot the SPR curves. We examined the change of the resonance angle by the influence of the incident wavelength. The simulation was also performed for different thicknesses of the gold film layer. To demonstrate the sensitivity, we obtained the SPR curves with the variation of the refractive index in the sensitive medium. The SPR accuracy was analysed by comparing our obtained result with the published work. It is intended to incorporate into undergraduate instrumental analysis courses.

Gaussian Beam Shaping and Multivariate Analysis in Plasmonic Sensing.

This work demonstrates a novel strategy to improve the sensing performance of a prism-coupled surface plasmon resonance system by Gaussian beam shaping and multivariate data analysis. The propagation of the beam along the optical system has been studied using the Gaussian beam approximation to design the incident beam such that the beam waist is aligned precisely and that stability is assured at the metal-dielectric interface. This renders a collimated incident beam, hence least angular dispersion, yielding a stronger and sharper plasmonic resonance. Moreover, we use the multivariate analysis method partial least squares that combines multiple features of the surface plasmon resonance curve and allows for a more precise analysis of the plasmonic response. Compared to univariate analysis, partial least squares improves typical sensing performance parameters remarkably. The combination of both aspects, beam shaping and multivariate analysis, overcomes current limitations of plasmonic detection systems. Thereby, we improve analytical sensitivity by a factor of 16, decrease the prediction error of the concentration of an unknown analyte by a factor of 11, and enhance resolution to the order of 5 × 10-7 RIU in angular interrogation.

Smart Noise Reduction in SPR Sensors Response Using Multiple-ANN Design

Surface plasmon resonance (SPR) based sensors are commonly applied to detect molecular interactions from features extracted of the so-called SPR curve. The SPR curve represents the position of the resonance occurrence, and reflects the quality of the sensor measurements. The instrumentation used in the SPR sensors require very specific coupling conditions for optical-electronic, mechanical, and fluidic components to properly excitate the surface plasmons. Noise sources inherent to the sensor instrumentation are reflected in the SPR curve and affect the quality of its extracted features. A smart-filter based on multilayer artificial neural networks is designed to eliminate the main instrumental noise sources and noise due to sensing proceedings at the SPR sensor usage, which are perceived as distortions in the SPR curves. The filter, called NNSF, is embedded to SPR sensors operating in both spectral (WIM) and angular (AIM) interrogation modes, and achieved responses with a mean square error of 10−5, and tested model correlation indexes over 90%. The filter redressed noises, including artifacts such as metal-layer roughness, light source input angle/wavelength disagreements, prism birefringence and general oscillations in amplitude and phase of the curve due to no-rigorous control process in the environment and experimental routines. Thus, the NNSF delivers curves with enhanced features and consequently increases the sensor performances in the monitoring of the resonance features (Width, Energy, Phase, Asymmetry, and minimum Position). Furthermore, the proposed filter avoids replacement or incorporation of new components that cause considerable instrumental maintenance cost.

Label-Free Analysis with Multiple Parameters Separates G Protein-Coupled Receptor Signaling Pathways.

Real-time label-free techniques are used to profile G protein-coupled receptor (GPCR) signaling pathways in living cells. However, interpreting the label-free signal responses is challenging, and previously reported methods do not reliably separate pathways from each other. In this study, a continuous angular-scanning surface plasmon resonance (SPR) technique is utilized for measuring label-free GPCR signal profiles. We show how the continuous angular-scanning ability, measuring up to nine real-time label-free parameters simultaneously, results in more information-rich label-free signal profiles for different GPCR pathways, providing a more accurate pathway separation. For this, we measured real-time full-angular SPR response curves for Gs, Gq, and Gi signaling pathways in living cells. By selecting two of the most prominent label-free parameters: the full SPR curve angular and intensity shifts, we present how this analysis approach can separate each of the three signaling pathways in a straightforward single-step analysis setup, without concurrent use of signal inhibitors or other response modulating compounds.

MACROCYCLE RING AND PERIPHERAL GROUP SIZES-DEPENDENT VAPOR SENSING PROPERTY OF COPPER PHTHALOCYANINE THIN FILMS

Spin-coated thin films of copper phthalocyanine (CuPc) were fabricated using different rotation speeds from 250 rpm to 1250 rpm. The structural characterization of these films was analyzed using UV-vis spectroscopy and atomic force microscopy (AFM). Gas sensing properties of these spun thin films were investigated against different volatile organic compounds such as chloroform, dichloromethane and toluene using surface plasmon resonance (SPR) technique. CuPc thin films were found to be highly sensitive to chloroform and dichloromethane vapor with fast response and recovery times. These measurements clearly indicated that the CuPc molecule is a promising material for the development of the room temperature vapor sensing applications with sensitivities between [Formula: see text] and [Formula: see text] percent response ppm[Formula: see text]. Three different functional groups of CuPc structures coded as CuPc I, II and III were investigated which differ from each other in their chemical structures in terms of their microcycle ring groups and peripheral groups, all attached to the same free base porphyrin skeleton. The number of microcycle ring groups and peripheral groups were found to be efficient on the gas sensing properties. The calculated refractive index and extinction coefficients using SPR curves were [Formula: see text] for CuPc I thin film, [Formula: see text] for CuPc II thin film and [Formula: see text] for CuPc III thin film, respectively. For different substrate rotation speeds, the thin film thicknesses vary between 2[Formula: see text]nm and 6[Formula: see text]nm for CuPc I and CuPc III thin films whereas it ranges between 4[Formula: see text]nm and 9[Formula: see text]nm for CuPc II thin film.

Enhancing the Sensitivity of a Surface Plasmon Resonance Sensor with Glancing Angle Deposited Nanostructures

In this paper, we demonstrate that the glancing angle deposition (GLAD) technique is a competitive and efficient method to fabricating a nanostructured surface that enhances the sensitivity of surface plasmon resonance (SPR) sensors, because of its simplicity and unique characteristics of material selection. The theoretical investigations were conducted by employing a rigorous coupled-wave analysis for design metrics, i.e., shift in resonance angle, SPR curve angular width, and minimum reflectance at resonance. An optimized geometry was achieved with enhanced characteristics of the SPR sensor. The SPR features of hybrid GLAD nanostructures deposited onto metallic thin films were investigated. An optical setup that used the Kretschmann-Reather configuration was utilized to monitor changes in the refractive index of water solution using the optical power interrogation method. The experimental results demonstrate that the SPR sensor fabricated with hybrid GLAD nanostructures of 30 nm height and ~ 12 nm inter-structural gap size achieved the sensitivity ~ 4× higher that of a than conventional SPR sensor.

Auxiliary Top‐Illumination in the Kretschmann–Raether Configuration: A Theoretical Study on the Surface Plasmon Resonance Response

A new variation of surface plasmon resonance (SPR) sensors design with Kretschmann–Raether (KR)‐type configuration is presented. Using a rotational incident angle scanning platform, the conductor nanolayer is normally irradiated with an auxiliary unpolarized light beam from the dielectric side. Both illumination sources should have a coherence length much larger than their source/Au layer optical path. Beginning with a Lorentzian‐type oscillator model, a general dispersion equation for the metal nanolayer is developed that incorporates interband transitions and polychromaticity of the top‐illumination beam. SPR curves are then predicted based on the transfer‐matrix method. Simulation results show that the top‐illumination frequency and its relative amplitude with respect to the bottom laser beam may impart significant changes to the SPR curve. It is shown that the implementation of short‐wave ultraviolet light (180 nm) may considerably improve the performance of SPR sensors in terms of the figure‐of‐merit. Larger wavelengths generally lead to performance deterioration. Based on the transverse magnetic solutions of the wave equation, a theoretical interpretation of the results is presented that confirms the strong effect of top illumination on the magnitude of the decay lengths in the conductor/dielectric and the propagation constant.

Characterization of the interaction between hen egg white lysozyme and ovalbumin: Interaction between lysozyme and ovalbumin

As two major proteins of egg white, the interaction between lysozyme (LYZ) and ovalbumin (OVA) has been studied. In the present research, the mechanism and kinetics of the interaction between LYZ and OVA were studied using several methods, including cyclic voltammetry (CV), dual polarization interferometry (DPI) and surface plasmon resonance (SPR), and the effect of their interaction on the activity of LYZ was investigated using a bacteriolytic activity assay. Cyclic voltammograms showed that there was an interaction between these two proteins. DPI results indicated that the interaction is a type of chimeric mode, and the KA and KD of the interaction were 498 and 2.01 × 10−3 mol/L, respectively, calculated from the fitting of the surface plasmon resonance curve. The bacteriolytic activity assay showed that the interaction between these two proteins reduced the bacteriolytic activity of LYZ.

Quantitative and Selective Surface Plasmon Resonance Response Based on a Reduced Graphene Oxide-Polyamidoamine Nanocomposite for Detection of Dengue Virus E-Proteins.

Dengue viral infection is one of the most common deadliest diseases and has become a recurrent issue for public health in tropical countries. Although the spectrum of clinical diagnosis and treatment have recently been established, the efficient and rapid detection of dengue virus (DENV) during viremia and the early febrile phase is still a great challenge. In this study, a dithiobis (succinimidyl undecanoate, DSU)/amine-functionalized reduced graphene oxide-–polyamidoamine dendrimer (DSU/amine-functionalized rGO–PAMAM) thin film-based surface plasmon resonance (SPR) sensor was developed for the detection of DENV 2 E-proteins. Different concentrations of DENV 2 E-proteins were successfully tested by the developed SPR sensor-based system. The performance of the developed sensor showed increased shift in the SPR angle, narrow full-width–half-maximum of the SPR curve, high detection accuracy, excellent figure of merit and signal-to-noise ratio, good sensitivity values in the range of 0.08–0.5 pM (S = 0.2576°/pM, R2 = 0.92), and a high equilibrium association constant (KA) of 7.6452 TM−1. The developed sensor also showed a sensitive and selective response towards DENV 2 E-proteins compared to DENV 1 E-proteins and ZIKV (Zika virus) E-proteins. Overall, it was concluded that the Au/DSU/amine-functionalized rGO–PAMAM thin film-based SPR sensor has potential to serve as a rapid clinical diagnostic tool for DENV infection.

Detection of phenol by incorporation of gold modified-enzyme based graphene oxide thin film with surface plasmon resonance technique.

In this study, the incorporation between gold modified-tyrosinase (Tyr) enzyme based graphene oxide (GO) thin film with surface plasmon resonance (SPR) technique has been developed for the detection of phenol. SPR signal for the thin film contacted with phenol solution was monitored using SPR technique. From the SPR curve, sensitivity, full width at half maximum (FWHM), detection accuracy (DA) and signal-to-noise ratio (SNR) have been analyzed. The sensor produces a linear response for phenol up to 100 µM with sensitivity of 0.00193° µM-1. Next, it can be observed that deionized water has the lowest FWHM, with a value of 1.87° and also the highest value of DA. Besides, the SNR of the SPR signal was proportional to the phenol concentrations. Furthermore, the surface morphology of the modified thin film after exposed with phenol solution observed using atomic force microscopy showed a lot of sharp peaks compared to the image before in contact with phenol proved the interaction between the thin film and phenol.

Experimental Investigation of the Dielectric Constants of Thin Noble Metallic Films Using a Surface Plasmon Resonance Sensor.

Gold and silver have an extremely low refractive index value of about 0.04 in the visible to near infrared (NIR) regions, and this induces a relative error of about 50% in refractive index measurements. This can lead to a large uncertainty in the imaginary part of the dielectric constants. A large difference exists between the experimental results and the classic models. The surface plasmon resonance (SPR) sensors, which use tens of nanometer thick noble metal film as the sensing layer, show ultra-high sensitivity (reaching 10−8 RIU) in this spectral range. As the spectral sensitivity and amplitude of SPR curves depend on the thickness and the dielectric constant of the sensing layer, we obtained high precision optical constants of the noble metal film using a multi-wavelength angle-modulated SPR sensing technology. The dielectric constant inferred from the parameters of the SPR curves, rather than from the refractive index and absorption ratio of noble metals, introduced a relative error within 10% of the resonance angle measurement. The measurement results demonstrate that the dielectric constants of gold and silver nano-films are more consistent with the widely used experimental results than with the classical theoretical model and always fall in the upper half of the imaginary part of the uncertainty range in the spectra of 500–900 nm.

SURFACE PLASMON RESONANCE IN As2Se3 PLANAR WAVEGUIDES FOR THE IR SPECTRAL REGION

The surface plasmon resonance (SPR) four layers configuration that contains prism of BK7-gold metal film-As2Se3 waveguide-air was realized. As2Se3 thin films with low roughness were obtained by thermal evaporation using cvasi-closed evaporator. The surface roughness’s was less than 2.5 nm. The SPR curves shape calculated by MATLAB solver were identical to these one calculated by matrix method. The As2Se3 films were characterized by ellipsometric spectroscopy and the obtained optical constants were used for calculations. Experimentally obtained SPR curves at the 1064 nm wavelength shown sharp resonance and are in accordance with calculus.

Metal Oxide Grating Based Plasmonic Refractive Index Sensor With Si Layer in Optical Communication Band

Nanostructure based devices are crucial for many applications including surface plasmon resonance (SPR) sensors, in particular. In this work, an aluminum oxide (Al2O3) grating based plasmonic sensor with Si and Ag layers is proposed and simulated for the detection of hemoglobin (Hb) concentration (en route its refractive index measurement) in human blood in optical communication band (1400-1550 nm). The simulations are based on rigorous coupled wave analysis (RCWA). In general, a plasmonic sensor's performance is closely evaluated in terms of sensitivity and figure of merit (FOM) but we have also extended the analysis by considering the SPR curves (of both reference and analyte samples) even more meticulously in terms of spectral FOM (FOM*) based on depth of reflectance curve. In order to further deepen the performance analysis, a quality factor (QF) is introduced by combining the maximum FOM* (m-FOM*) and FWHM of the analyte SPR curve. The effect of grating variables and the thicknesses of Si and Ag layers on FOM* and QF is analyzed. The simulation results are explained in relevant physical concepts such as radiation damping. The results indicate that the proposed sensor with optimized design parameters is able to provide significantly better sensitivity, detection limit, FOM, and m-FOM* compared with existing grating-based SPR sensors.

Surface Plasmon Resonance Chemical Sensors Based on Amorphous Chalcogenide Waveguides

AbstractSoftware uses matrices method for finding the surface plasmon resonance (SPR) is developed and calculations are provided for four‐layer thin‐film geometry. Numerical simulations concerning SPR curves with As2S3 amorphous chalcogenide film are done. The structure is very sensitive to changes of refractive indices of liquids that are in contact with amorphous film. The SPR sharpness is higher in comparison with well‐known three‐layer Kretschmann configuration that means better sensibility up to 10−5 of chemical sensors based on optical SPR.

Studying corrosion of silver thin film by surface plasmon resonance technique

A novel strategy is proposed by using surface plasmon resonance technique to investigate the corrosion process of silver thin film within 100 nm thickness exposed to laboratory air. Specifically, we continuously test surface plasmon resonance curves of silver thin film for 40 days and calculate its permittivity and thickness. Measurements of energy dispersive spectrometer indicate that there are silver sulfide formations on the film surface in the corrosion process. By using Maxwell–Garnett effective medium theory, the volume fraction of silver sulfide was confirmed in the silver/silver sulfide composites film. The results reveal that the concentration of silver sulfide in the film sample increases exponentially during the corrosion process and increases rapidly in the initial stage.

Graphene-MoS2-Au-TiO2-SiO2 Hybrid SPR Biosensor: A New Window for Formalin Detection

In this article, numerically a surface plasmon resonance (SPR) biosensor is developed based on Graphene-M­­­­OS2-Au-TiO2-SiO2 hybrid structure for formalin detection. This developed sensor sensed the presence of formalin by applying attenuated total reflection (ATR). In ATR method, we developed and observed two characteristics curve, one is “SPR angle versus minimum reflectance (Rmin)” and another is “SPR frequency (SPRF) versus maximum transmittance (Tmax). In the proposed sensor, Chitosan is used as probe legend to perform specific reaction with the formalin (40% formaldehyde) as target legend. Here, graphene and MoS2 both are used as biomolecular acknowledgment element (BAE). And TiO2 as well as SiO2 bilayers are used to improve sensor sensitivity and Gold (Au) is to sharp SPR curve. In numerical results, the variation of SPRF and SPR angle for inappropriate sensing of formalin is quiet insignificant which confirms the absence of formalin. On the other hand, these variations for appropriate sensing is considerably significant that confirms the presence of formalin. At the end of this article, a study of variation of sensitivity of the proposed biosensor in corresponding to the increment of refractive index with a refractive index step 0.01 RIU is measured. In inclusion of TiO2-SiO2 bilayers with Graphene-M­­­­OS2, maximum sensitivity of 85.375% more is numerically reported.

High performance refractive index SPR sensor modeling employing graphene tri sheets

This article illustrates a graphene tri sheets based surface plasmon resonance (SPR) biosensor. The exciting configuration consists of Gold (Au), graphene, prism (SF11 glass) and sensing medium. The angular interrogation scheme is basically utilized owing to inspect the light reflection from the sensor. For sake of the augmentation of sensor sensitivity (S), signal to noise ratio (SNR), quality factor (QF), first of all, the impact of adding graphene layer is investigated and then the number of graphene layers are optimized to tri layers. According to that tri sheets, the SPR curves are sketched and comparison of sensor sensitivity, SNR, the quality factor is made among the existing works. It is audited that an extraordinary improvement of sensitivity to 121.67° RIU−1. The most effective graphene layers states with improved SNR of 2.21 and QF of 36.87 RIU−1 respect conventional SPR sensor. After then, the electric field intensity on implanting graphene sheet is analyzed by incorporating the finite difference time domain (FDTD) method by applying the Opti FDTD multiphysics commercial software environment. The proposed design bears the advantages of high sensitivity, QF and SNR comparing with the existing sensors along with simple stricture, no need of plasmonic coatings of other dielectrics, compactness, light weight, real time fabrication flexibility due to avoid multi materials optical structure.

Unraveling Compositional Changes of the Double Layer upon Sulfate Adsorption on Au(111) by Surface Plasmon Resonance

The potential-induced sulfate adsorption on (111)-textured Au films in 0.1 M sulfuric acid was studied by surface plasmon resonance (SPR) measurements. Full SPR curves were recorded with millisecon...

Design and analysis of graphene–MoS2 hybrid layer based SPR biosensor with TiO2–SiO2 nano film for formalin detection: numerical approach

In this paper, a Surface Plasmon Resonance (SPR) biosensor has been numerically developed that used Graphene–MoS2–Au–TiO2–SiO2 hybrid structure for the detection of formalin. This developed sensor has been sensed the presence the formalin based on attenuated total reflection (ATR) method by observing the change of “surface plasmon resonance angle-the change of minimum reflectance attributor” and “the resonance frequency characteristics (RFC)-maximum transmittance attributor”. Chitosan has been used as probe sensing medium to accelerate particular reaction with the formalin. Here, graphene is used as biomolecular recognition element because of its high adsorption ability and optical characteristics which helps to improve sensor sensitivity, MoS2 used for it has larger band gap, high fluroscence quenching ability, higher optical absorption efficiency, TiO2–SiO2 bilayer as the improvement of sensitivity and Gold (Au) as the sharp SPR curve. Numerical results give the impression that the variation of RFC and SPR angle for improper sensing of formalin is quiet negligible that confirms no formalin is detected whereas for proper sensing these change are considerably countable that confirms the detection of formalin. From the sensor sensitivity analysis, owing to add TiO2–SiO2 bilayer with Graphene–MoS2 Hybrid layer, maximum sensitivity of 85.375% has been numerically resulted. This high sensor performance is for taking advantages of Graphene surface high selectively which detect bio molecular compounds through pi-stacking force, larger work function (5.1 eV) of MoS2 which allows the high sensitive detection of bio targets and Rich plasmon happens at the TiO2–SiO2 interface.