SPR-based Sensor Research Articles

Design and analysis of SPR-based refractive index sensor with enhanced sensitivity based on graphene/BP heterostructure

Design and analysis of SPR-based refractive index sensor with enhanced sensitivity based on graphene/BP heterostructure

Preliminary Study of Resonance Systems States in Surface Plasmon Resonance Systems

Abstract Resonance between light and collective electrons is known as Surface Plasmon Resonance or SPR. The development of SPR-based sensors can generate the use of a Kretschmann configuration prism. Otto configuration dielectric medium between prism and gold thin film. For the Kretschmann configuration, a gold thin film between the prism and dielectric medium. So, this research focuses on the use of the Kretschmann configuration in the SPR system because the setup of the half-cylindrical prism is less complicated than using the Otto configuration. In this research, we compare the reflectance of an uncoated half-cylindrical prism and a half-cylindrical prism coated with a gold thin film to see the resonance effect. The beam reflected by the back surface of the prism was detected using a photodiode sensor (OPT-101, Texas Instruments). The photodiode sensor is connected to Arduino Uno, and the voltage reading results are processed with Arduino Ide software. Adjusting the He-Ne laser light’s angle of incidence and the prism’s angle of impact 30° – 50°. The experimental results show that the TIR (total internal reflection) phenomenon occurs in half-cylindrical prisms without a gold coating. Meanwhile, in the half-cylindrical prism coated with gold, a resonance phenomenon can be seen, this case, at a particular angle of incidence, can be detected through a reduction in the beam’s intensity of the reflected light. The photodiode sensor detects a decrease in voltage value, which indicates an intensity decrease, which was originally 4.34 volts to 2.52 volts when the incident angle of the light beam was 45°.

Advances in SPR-Based Fiber Optic Sensors for Voltage/Electric Field Measurement—A Review

Advances in SPR-Based Fiber Optic Sensors for Voltage/Electric Field Measurement—A Review

Surface plasmon resonance sensor with photodiode integrated beneath plasmonic layer

Surface plasmon resonance (SPR)-based sensors have demonstrated exceptional sensitivity in detecting changes in the refractive index (RI) occurring near the sensor surface due to variations in concentration within the medium, chemical reactions, analyte binding with its ligand, and similar factors. However, most conventional SPR sensors rely on an external photodiode system and a complex mechanical system to measure changes in both intensity and position of reflected light. This is the main limitation of typical SPR sensors, making them non-portable and challenging to apply in experiments beyond the laboratory. Here, we propose SPR sensor chips integrated with a photodiode that eliminates the disadvantage of conventional SPR sensors. The photodiode is based on an n-type Silicon (nSi)-intrinsic Silicon (iSi) junction, sandwiched between a transparent conductive oxide layer, specifically Indium Tin Oxide (ITO), and a plasmonic material, namely Gold (Au). The working principle of our photodiode-integrated SPR sensors was revealed, and the impact of nSi and iSi film thicknesses on sensor sensitivity was investigated. Our SPR sensors enhance the efficiency of SPR-based sensors across diverse applications and facilitate integration into completed electronic devices.

Enhancing urine glucose sensing performance through the introduction of two dimensional-transition metal dichalcogenides and gold nanoparticles into silver/UiO-66 chip of surface plasmon resonance

This work presents a high-performance surface plasmon resonance (SPR)-based biosensor for glucose detection. While adding a metal–organic framework layer, UiO-66, to the biosensor improves selectivity and enables direct detection without additional receptors, it does not significantly enhance sensitivity. A SPR-based biosensor is proposed to overcome this limitation by introducing a layer of 2D-transition metal dichalcogenides (2D-TMD) and decorating the UiO-66 structure with gold nanoparticles (UiO-66AuNP). The optical properties of the biosensor for glucose detection in urine are investigated by employing the finite difference time domain (FDTD) method with Kretschmann configuration at a wavelength of 633 nm, and its performance is effectively improved by incorporating 2D-TMD and AuNP layers into the biosensor structure. Notably, the SPR-based biosensor with the decorated UiO-66 layer exhibits a further change in the SPR angle in the presence of glucose-containing urine. Using computational studies, various performance parameters, such as the biosensors’ signal-to-noise ratio and quality factor, are evaluated in addition to sensitivity. The maximum sensitivity achieved is 309.3°/RIU for the BK7/Ag/PtSe2/WSe2/MoS2/UiO-66AuNP/sensing medium structure. The exceptional performance of the proposed biosensor structure demonstrates its suitability for precise glucose detection in urine while also opening new avenues for developing bioreceptor-free SPR-based sensors.

SPR-Based Sensor for Colorectal Cancer Detection using Al–Cu and Graphene

SPR-Based Sensor for Colorectal Cancer Detection using Al–Cu and Graphene

A theoretical analysis of performance enhancement of SPR sensor based on ZnO and BaTiO3 for NH3 detection

Surface plasmon resonance (SPR) sensors have attracted enormous attention due to their applications in various fields. A novel SPR-based sensor with ZnO and BaTiO3 metal oxide layers is designed for NH3 gas detection. Gold and silver are used as plasmonic materials and corresponding results are compared. The prism and plasmonic materials effects on sensor response are investigated. Moreover, thicknesses of gold and silver and metal oxide layers are optimized to obtain suitable performance parameters. sensor response is analyzed in terms of minimum reflectance, sensitivity, detection accuracy and quality parameter. Applying ZnO and BaTiO3 layers lead to 37.88% and 26.03% enhancement of quality parameter and 37.91% and 26.07% improvement of detection accuracy, and more than 3.4 times improvement of detection resolution in gold and silver-based sensors, respectively. The recommended sensor structure provides appropriate performance parameters for 1 to 200 ppm of NH3 gas that can have potential applications in toxic gas sensing.

SPR-based sensor for ultra-high sensitivity high refractive index measurements in the near-infrared

SPR-based sensor for ultra-high sensitivity high refractive index measurements in the near-infrared

SPR-Based refractive index sensor using BaTiO3 and WS2 with Al-Ni bimetal for glucose sensing

In this work, we propose a high-performance surface plasmon resonance (SPR)-based refractive index biosensor to determine the glucose concentration in the urine samples. To achieve the most efficient design for the sensor, four possible designs have been investigated. The proposed design of the sensor uses the Kretschmann configuration, which consists of a BK7 glass prism with Aluminum (Al) and Nickel (Ni) metallic layers separated by a dielectric layer of barium titanate (), and a 2D material tungsten disulfide () layer placed above the Ni layer. The dielectric layer of is used to enhance the shift in the resonance angle and to increase the absorption of the biomolecules, which results in an increase in the sensitivity of the sensor. The performance of the sensor has been numerically investigated using the transfer matrix method at wavelength. Minimum reflectance at resonance is studied to show the coupling strength of the incident light with the surface plasmons. The thicknesses of the Al and Ni metallic layers have been optimized for maximum sensitivity and minimum reflectance at the resonance. The performance of the proposed sensor has been investigated to obtain sensitivity for different glucose concentrations in the urine samples. The sensor has a sensitivity of for glucose concentration in the range The corresponding glucose concentration sensitivity is 0.4 The proposed study would be helpful in designing the refractive index-based biosensor for medical diagnostics applications.

SPR-Based Label-Free Sensor for RI-Based Detection of Urea Concentration

SPR-Based Label-Free Sensor for RI-Based Detection of Urea Concentration

Au-strip structure dependent performance investigation of D-shaped SPR sensors for biosensing applications

Surface Plasmon Resonance (SPR)-based sensing technologies show great promise in diverse applications (e.g. biosensing) as one of the most innovative and exciting label-free sensing techniques in the last few years. In general, SPR-based sensors combine metal and dielectric interfaces, where the oscillation of metal’s free electrons occurs by the incident incoming photons. Thus, the SPR signal strength depends on the metal’s optical properties as well as the surrounding dielectric medium. This work thoroughly investigates the performance of a single mode D-shape SPR-based refractive index (RI) sensor with its gold (Au) strip topology to improve the detection sensitivity. Seven distinct Au strip designs: single-arc, inverted single-arc, multi-arc, inverted multi-arc, half-circle, coil, and sinusoidal wave are introduced to explore sensor performances, which are investigated numerically using Comsol Multiphysics. Systematic investigations are carried out for all seven proposed designs and relative comparisons are made in terms of sensitivity (wavelength and amplitude), resolution, and figure of merit (FoM). Coil and sinusoidal wave-shaped designs show excellent performance among all seven designs with a wide range of analytes’ RI (i.e. 1.31 to 1.39). The maximum wavelength and amplitude sensitivities are found to be 48000 nm/RIU and 18.55 RIU−1 respectively, with a wavelength resolution of 2.08 × 10-6 RIU and a consequent FoM of 141.18 RIU−1 for the sinusoidal wave-shaped Au-strip design. Alternatively, the coil-shaped design shows the maximum wavelength and amplitude sensitivities of 45000 nm/RIU and 32.17 RIU−1 respectively, with a wavelength resolution of 2.22 × 10-6 RIU and a FoM of 85.71 RIU−1. As a wide range of analyte’s RI can be detected by the proposed sinusoidal wave and coil Au-strip-based D-shaped sensors with improved sensitivity, these designs could be effectively used for the detection of different bio-analytes.

A D-Shaped SPR-Based PCF Sensor with an Extremely High-Amplitude Sensitivity for Measuring the Refractive Index.

In this work, a new D-shaped photonic crystal fibre sensor structure based on surface plasmon resonance (SPR) is purposed for measurement of analyte refractive index (RI). In this design, a silica cylinder is polished into a D-shaped silica material structure with a flattened surface where two Au nanowires are coated. Some air holes are omitted to form the core mode region. With the implementation of gold nanowires and a core region for the exciting SPR effect with variate physical values, analyte RI can be measured with a wavelength coverage from 850 to 1350nm. The numerical simulation shows the maximum wavelength sensitivity of the purposed design achieves 19,600nm/RIU with an RI coverage from 1.37 to 1.42. Moreover, the sensor has a tremendous amplitude sensitivity and the maximum absolute value is about 2300RIU-1. Benefiting from these outstanding performance, the purposed structure can be given priority when it is applied in biomedical detecting and environmental assessment science.

A surface plasmon resonance nanostructure containing graphene and BaTiO3 layers for sensitive defection of organic compounds.

Organic compound-based sensors are used in a variety of significant fields, including medical research, azeotropic calibration, vegetable oil extraction, the shoe industry and geothermal power plants. Here, a high-performance, two-dimensional material-based organic compound sensor has been proposed using a surface plasmon resonance (SPR) nanostructure consisting of a BK7 glass prism, Ag, BaTiO3, Ag, graphene and sensing layer. The reflectivity curves of the SPR device have been investigated when the sensing media are Pentane, n-Hexane, n-Heptane and n-Octane. The thickness of the BaTiO3 layer and the number of graphene sheets have been optimized to maximize the sensitivity. The highest sensitivity attained is 220.83 deg/RIU for n-Octane with 45 nm silver/10 nm BaTiO3/8 nm silver and four layers of graphene. We believe that the SPR-based sensors are simple and can replace the spectrometry, chromatography and electrochemical based sensors. The proposed design is extremely effective for diverse applications in biological, industrial and chemical detection because of its simple structure and great performance.

Design of Optimal SPR-Based Multimode Waveguide Sensor for a Wide Range of Liquid Analytes

Surface plasmon resonance (SPR)-based sensors have attracted huge interest due to their ability to provide real-time sensing of a wide range of quantities, while still boasting high sensitivity, low cost, and electromagnetic immunity. Among various types of these sensors, waveguide-based sensors show great promise in terms of integrability into more complex circuits while still maintaining similar sensitivity and versatility as their stand-alone counterparts. This paper presents the results of investigation based on design and simulation of optimal parameters for multimode SPR-based waveguide sensor sensitive to any commonly used liquid analytes. The sensitivity for a wider range of analytes is achieved by utilisation of SiON material platform because refractive index adjustability of SiON offers a way to tailor sensor’s sensitivity to exact applications and analytes. One of the research goals in this work was to show that multi-mode waveguides may be suitable for such sensors with comparable sensitivity and higher transmission rates as single-mode waveguides. To showcase design possibilities, two variations with the same design and material’s refractive index adjustment only were investigated, and their optimal parameters have been found. Sensitivity for all commonly used liquid analytes was validated, with sensitivity rising to 1400 nm/RIU for label-free refractive index sensing, even without the use of any sensitivity-enhancing structures.

Deposition of Graphene Oxide on an SPR Fiber Refractometer for Sensor Applications.

Graphene-based materials have been increasingly incorporated to optical fiber plasmonic sensors due to the peculiar physical and chemical properties of these materials (hardness and flexibility, high electrical and thermal conductivity, and very good adsorption for many substances, etc.). In this paper, we theoretically and experimentally showed how the addition of graphene oxide (GO) to optical fiber refractometers permits the development of surface plasmon resonance (SPR) sensors with very good characteristics. We used doubly deposited uniform-waist tapered optical fibers (DLUWTs) as supporting structures because of their already proven good performance. The presence of GO as an effective third layer is useful to tune the wavelength of the resonances. In addition, the sensitivity was improved. We depict the procedures for the production of the devices and characterize the GO+DLUWTs produced in this way. We also showed how the experimental results are in agreement with the theoretical predictions and used these to estimate the thickness of deposited GO. Finally, we compared the performance of our sensors with other ones that have been recently reported, showing that our results are among the best reported. Using GO as the medium in contact with the analyte, in addition to the good overall performance of devices, permit consideration of this option as an interesting possibility for the future development of SPR-based fiber sensors.

Sensing Mechanisms of Rough Plasmonic Surfaces for Protein Binding of Surface Plasmon Resonance Detection.

Surface plasmon resonance (SPR) has been utilized in various optical applications, including biosensors. The SPR-based sensor is a gold standard for protein kinetic measurement due to its ultrasensitivity on the plasmonic metal surface. However, a slight change in the surface morphology, such as roughness or pattern, can significantly impact its performance. This study proposes a theoretical framework to explain sensing mechanisms and quantify sensing performance parameters of angular surface plasmon resonance detection for binding kinetic sensing at different levels of surface roughness. The theoretical investigation utilized two models, a protein layer coating on a rough plasmonic surface with and without sidewall coatings. The two models enable us to separate and quantify the enhancement factors due to the localized surface plasmon polaritons at sharp edges of the rough surfaces and the increased surface area for protein binding due to roughness. The Gaussian random surface technique was employed to create rough metal surfaces. Reflectance spectra and quantitative performance parameters were simulated and quantified using rigorous coupled-wave analysis and Monte Carlo simulation. These parameters include sensitivity, plasmonic dip position, intensity contrast, full width at half maximum, plasmonic angle, and figure of merit. Roughness can significantly impact the intensity measurement of binding kinetics, positively or negatively, depending on the roughness levels. Due to the increased scattering loss, a tradeoff between sensitivity and increased roughness leads to a widened plasmonic reflectance dip. Some roughness profiles can give a negative and enhanced sensitivity without broadening the SPR spectra. We also discuss how the improved sensitivity of rough surfaces is predominantly due to the localized surface wave, not the increased density of the binding domain.

Illustration of an extremely sensitive SPR based fiber optic gas sensor irradiated by Bessel-Gauss beam and wave theory based approach

Corroboration with the already described experimental data, an exploration of a more sensitive SPR-based bimetallic fiber optic gas sensor (FOGS) using wave theory by illuminating the Bessel-Gauss beam is analytically proposed and designed here for methane gas sensing. The results are verified with the already reported experimental outcomes presented by Z. Shao et al. 2016 [43]. From a comparative assessment with the existing articles, it is observed that the RI sensitivity is 8936 dB/RIU, and the resolution is 1.12 × 10−6, which is one order superior to the reported FOGSs till date. The vital reason behind adopting the wave theory-based approach is for efficient computation of the coupling coefficient of the generated higher order modes and to acquire the similarities between the methodical and experimental solutions. With this process, first time utilizing the Bessel-Gauss beam, enhanced sensitivity is manifested for bimetallic FOGS. A higher dynamic range of refractive index from 1.06 to 1.22 and the consequences of the coupling of different modes are also discerned here. Here, the minimum detectable concentration is 1 ppm for the minimum change in transmission loss of 0.22 dB/RIU. This idea has various applications with the advantages like enhanced sensitivity, small size and broader detection ranges.

Black Phosphorous-Based Highly Sensitive Surface Plasmonic Sensor for Detection of Formalin

In the present work, a highly sensitive prism-based surface plasmon resonance (SPR) sensor for the detection of formalin using multilayer black phosphorous (BP) is proposed. Formalin, which is widely used as a preservative, can cause a variety of diseases, making its detection crucial. The transfer matrix method is utilized to compare and analyze the proposed structures of the SPR-based prism sensor in the Kretschmann configuration. The effect of prism materials (BAK3, BK7, SF10, SF11, and 2S2G), metals (gold, silver, copper, and aluminum), and 2-D materials (graphene, MoS2, WS2, and BP) on the performance of the sensor for formalin detection has been analyzed and discussed. The analysis of the impact of employing multilayer 2-D materials is carried out. Optimization of the thickness of the 2-D material is performed to achieve a structure that gives better sensitivity. The sensitivity achieved for structures with multilayer graphene, MoS2, and WS2 are 172.82°/RIU, 195.97°/RIU, and 218.04°/RIU, respectively. A highly sensitive structure for formalin detection is proposed with BK7, silver, and nine layers of BP. A sensitivity of 289.4565°/RIU and a detection accuracy (DA) of 0.3125/° are obtained. The limit of detection of the proposed sensor for different concentrations of formalin lies in the range of 3.45– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.56~ \mu $ </tex-math></inline-formula> RIU.

The Effect of Relative In-Plane Twisting in Graphene Bilayer on Sensing Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) is generally observed by the excitation of surface plasmon polaritons on the metal (Au/Ag) surface. In order to utilize the SPR phenomenon for sensing application, the metal surface is functionalized with suitable ligands. Although such functionalization can enhance the specific adsorption capability of the sensor however due to the large thickness of the ligands, the plasmonic field of the metal surface becomes less sensitive towards the adsorption of analytes. In the next generation SPR-based sensor, graphene can be utilized not only as plasmonic material but also as a suitable ligand for attracting analytes through π-π interaction. In this article, we present our theoretical simulation studies on the observation of the SPR phenomenon using graphene monolayer (MLG), bilayer graphene (BLG), and in-plane twisted layers of BLG (T-BLG) as plasmonic materials deposited over zinc-selenide substrate. The Kretschmann configuration under wavelength interrogation setup was simulated, and SPR wavelength for graphene systems/water interface was estimated. The bio-sensing simulation was performed, and the sensing parameters viz. sensitivity, figure-of-merit (FOM), and plasmonic field for different graphene systems were obtained. Interestingly, the excellent sensing parameters were found in T-BLG system with relative in-plane twist angle near to magic angle viz. 1°. The enhancement is due to strong coupling between the layers twisted at the magic angle. This study demonstrates that the MLG, BLG and T-BLG can be employed as a standalone layer system for not only the generation of plasmonic fields but also enhanced sensing due to its intrinsic interactions with bio-analytes.

Heterogeneous Optical Fiber Sensor System for Temperature and Turbidity Assessment in Wide Range.

This paper presents the development of an optical fiber sensor system for multiparametric assessment of temperature and turbidity in liquid samples. The sensors are based on the combination between fiber Bragg gratings (FBGs), intensity variation and surface plasmon resonance (SPR) sensors. In this case, the intensity variation sensors are capable of detecting turbidity with a resolution of about 0.5 NTU in a limited range between 0.02 NTU and 100 NTU. As the turbidity increases, a saturation trend in the sensor is observed. In contrast, the SPR-based sensor is capable of detecting refractive index (RI) variation. However, RI measurements in the turbidity calibrated samples indicate a significant variation on the RI only when the turbidity is higher than 100 NTU. Thus, the SPR-based sensor is used as a complementary approach for the dynamic range increase of the turbidity assessment, where a linearity and sensitivity of 98.6% and 313.5 nm/RIU, respectively, are obtained. Finally, the FBG sensor is used in the temperature assessment, an assessment which is not only used for water quality assessment, but also in temperature cross-sensitivity mitigation of the SPR sensor. Furthermore, this approach also leads to the possibility of indirect assessment of turbidity through the differences in the heat transfer rates due to the turbidity increase.