A High-Sensitivity SPR Sensor with Bimetal/Silicon/Two-Dimensional Material Structure: A Theoretical Analysis

In this paper, a theoretical analysis of figure of merit (FOM) of a surface plasmon resonance (SPR) sensor with a buffer layer of magnesium fluoride has been carried out. While the FOM is the ratio of sensitivity and full width at half maximum and it is the measurement index for the SPR performance. The numerical simulation is based on side polished single mode fiber SPR sensor with the 66.5 μm residual fiber thickness and Drude model of metal with the 50 nm gold film thickness. Meanwhile, the comparisons for traditional surface plasmon resonance sensor, symmetrical surface plasmon resonance sensor and long range surface plasmon resonance sensor have performed differently for the FOM. The effect of sensitivity, full width at half maximum and transmittance depth has also been studied. All these studies, lead to a significant analysis to achieve the best possible design of a fiber optic SPR sensor with maximum FOM while the thickness of buffer layer is 100 nm. This design is expected to play an important role on chemical sensing and biological sensing.

High-sensitive optoelectronic SPR biosensor based on Fano resonance in the integrated MIM junction and optical layers

In this paper, we propose a surface plasmon resonance (SPR) sensor based on two-dimensional (2D) materials (graphene, MoS2, WS2 and WSe2) hybrid structure, and theoretically investigate its sensitivity improvement in the visible region. The thickness of metal (Au, Ag or Cu) and the layer number of each 2D material are optimized using genetic algorithms to obtain the highest sensitivity for a specific wavelength of incident light. Then, the sensitivities of proposed SPR sensors with different metal films at various wavelengths are compared. An Ag-based SPR sensor exhibits a higher sensitivity than an Au- or Cu-based one at most wavelengths in the visible region. In addition, the sensitivity of the proposed SPR sensor varies obviously with the wavelength of incident light, and shows a maximum value of 159, 194 or 155°/RIU for Au, Ag or Cu, respectively. It is demonstrated that the sensitivity of the SPR sensor based on 2D materials’ hybrid structure can be further improved by optimizing the wavelength of incident light.

A novel doublet-based surface plasmon resonance biosensor via a digital Gaussian filter method

A transmission-type surface plasmon resonance (SPR) sensor is presented. In the transmission-type SPR structure, surface plasmon waves are outcoupled to radiation modes by the use of dielectric grating on a thin-film layer of Ag. Compared with the traditional reflection-type SPR sensor, the new method provides larger detectable range, which might be useful to investigate thick targets such as in cell analysis. Theoretical simulations show that the structures provide high transmission efficiency for surface plasmon resonance and the devices present extremely linear sensing characteristics. Furthermore, it is found that the transmission efficiency and the refractive index detection sensitivity of the SPR sensor can be improved by the use of a lower refractive index glass prism.

Enhanced sensitivity of bimetallic optical fiber SPR sensor based on MoS2 nanosheets

To address the problems that the surface plasmon resonance (SPR) sensor is not sensitive enough to detect biomolecules in the refractive index range (RI=1.33-1.34), and the traditional methods to enhance the sensitivity cause the sensor poor bioaffinity, this paper proposed raspberry-like silica assisted high figure of merit (FOM) fiber-optic SPR sensor. The finite element method results show that when the raspberry-like silica is introduced to the SPR sensor, the resonant electric field intensity on the sensor surface is 2.97 times stronger than that of SPR sensors only. Raspberry-like silica particles composed of different noble metals nanoparticles (AuNPs, PtNPs, and CuNPs) were prepared to compare and analyze the effects of different nanoparticles on the sensing performance. The sensing experiments showed that AuNPs raspberry-like silica had the most excellent performance, enabling the sensor to achieve high sensitivity of 5264.3 nm/RIU, which is 2.65 times higher than the Au film SPR sensor. The fitting calculations showed that the AuNPs raspberry-like silica assisted SPR sensor had a high FOM of 42.9 RIU-1, 1.9 times more than the Au film SPR sensor. In addition, the sensor has good temperature stability, repeatability, and generality after the corresponding test. The proposed raspberry-like structure provides a new approach to obtaining both high sensitivity and high FOM for the SPR sensor, which makes the sensor potential for biosensing.

A high-sensitivity surface plasmon resonance (SPR) sensor based on the coupling of Au grating and Au film is investigated through simulations and experiments. The SPR sensor is designed by using a hybrid method composed of genetic algorithm (GA) and rigorous coupled wave analysis (RCWA). The numerical results indicate the sensor has an angular sensitivity of 397.3°/RIU (refractive index unit), which is approximately 2.81 times higher than the conventional Au-based sensor and it is verified by experiments. Theoretical analysis, by finite-difference time-domain (FDTD) method, demonstrates the co-coupling between surface plasmon polaritons (SPPs) propagating on the surface of Au film and localized surface plasmons (LSPs) in the Au grating nanostructure, improving the sensitivity of the SPR sensor. According to the optimized structural parameters, the proposed sensor is fabricated using e-beam lithography and magnetron sputtering. In addition, the proposed sensor is very sensitive to the detection of small molecules. The limit of detection (LOD) for okadaic acid (OA) is 0.72 ng/mL based on an indirect competitive inhibition method, which is approximately 38 times lower than the conventional Au sensor. Such a high-sensitivity SPR biosensor has potential in the applications of immunoassays and clinical diagnosis.

In this present paper, we propose a surface plasmon resonance(SPR)sensor having better performance parameters based on Kretschmann configuration. The proposed SPR sensor is a modified Kretschmann configuration comprised of BK7 prism-Cu-Pt-Graphene/BP/WS2. The bimetallic layer provides consistent enhancement of sensitivity over other SPR structures. Extensive numerical analysis based on transfer matrix theory has been performed to characterize the sensor response considering sensitivity, full width at half maxima (FWHM), detection accuracy(DA), quality factor(QF) with other conventional reported SPR sensor. We have also analyzed the electric field intensity enhancement factor(EFIEF) for the proposed SPR sensor. We have found that maximum sensitivity of 309deg/RIU corresponds to the four layer of BP configuration. We believe that this proposed SPR sensor could find the new platform for the chemical examination, medical diagnosis, gas detection and biological detection.

Due to their extreme sensitivity to refractive index changes, surface plasmon resonance (SPR) sensors have long been established as extremely valuable tools for biosensing. In the past few years researchers have begun investigating various other metallic nanostructures as candidates for localized SPR (LSPR) sensing. Although LSPR is not nearly as sensitive to bulk refractive index changes as standard SPR, is has the advantage of being extremely sensitive to local refractive index changes, thereby providing detection on the level of a single molecule. In practice such sensitivity criterion is of paramount importance since the analyte layer under investigation is often only a few nanometers thick and deposited directly on the surface of the metal. Most desirable, however, is a sensor that retains the total integrated sensitivity of a traditional SPR sensor and at the same time localizes this sensitivity right at the sensor surface. For this reason, we have investigated a hybrid structure composed of a 2D Au nanoparticle array coupled to a Au film. We show that this structure, when excited in the Kretschmann configuration, retains to a surprising degree the total integrated sensitivity of an ideal SPR sensor and is able to concentrate that sensitivity within a few nanometers of the sensor surface, thereby yielding a hybrid sensor with the advantages of both LSPR and SPR sensing, i.e. both a high local sensitivity and a high figure of merit (FOM).

With the ongoing advancement of modern society, the demand for high‐sensitivity and real‐time detection sensors continues to grow, thereby accelerating the development of sensing technologies. Surface plasmon resonance (SPR) sensing has emerged as a valuable technique owing to its real‐time, label‐free, and rapid detection capabilities. However, its limited sensitivity and detection range remain major challenges in optical sensing. MXenes, as two‐dimensional (2D) materials, have garnered considerable attention owing to their large specific surface area, high electrical conductivity, excellent biocompatibility, and stability, establishing them as one of the most prominent materials for optical sensing. This paper first provides a concise overview of the properties of MXenes, followed by an analysis of various SPR sensor configurations and performance improvement strategies. Finally, it summarizes the latest advances in the application of MXenes in SPR sensors, discusses their potential for enhancing sensing performance, and offers a perspective on development directions. Despite being in its early stages, MXene‐based SPR sensing has demonstrated significant potential for expanding into broader applications.

In this paper, a TMDC-based surface plasmon resonance (SPR) sensor for detecting fat concentration milk, incorporating an Ag-Pt (bimetallic) layer, is presented. The Pt (Platinum) layer provides chemical stability and increases sensitivity with the TMDC layer. Compared to the conventional SPR sensor, the maximum sensitivity, detection accuracy (DA), and figure of merit (FoM) of 314∘/RIU, 0.142/degree, and FoM 44.05/RIU are achieved with the WS2 layer. The sensor’s increased sensitivity is due to the increased field intensity and depth of penetration into the sensor layer, resulting in a larger interaction volume. The presence of the WS2 layer, with its significant imaginary part of the dielectric constant, helps improve sensitivity and broadens the SPR curves. This broadening SPR curve ultimately affects the DA and FoM of the sensor. The capability of the proposed sensor to detect various biological analytes with a refractive index (1.3452–1.3657) can be demonstrated.

Sensitivity enhancement in erbium-doped fiber laser intra-cavity SPR sensor

In this work, we theoretically and experimentally demonstrate a highly sensitive porous silicon membrane waveguide biosensor in the Kretschmann configuration, and show how the cladding material directly impacts the waveguide sensor detection sensitivity and resonance width. Dielectric and metal-clad porous waveguides in the Kretchmann configuration have the potential to achieve significantly enhanced performance for small molecule detection compared to planar waveguide and surface plasmon resonance sensors due to increased surface area and strong field confinement in the porous waveguide layer. First order perturbation theory calculations predict that the quality factors of polymer-cladded porous silicon waveguides with porous silicon losses less than ~500 dB/cm are at least two times larger than the quality factors of gold-cladded porous silicon waveguides and traditional surface plasmon resonance sensors.

This paper presents low-cost, multi-channel, nano-grating SPR (Surface Plasmon Resonance) sensor chips for applications to disposable biomolecule detection. The present SPR sensor chip consists of two fluidic channels, including a sample channel and a reference channel, each having 833 nm-pitch PDMS gratings. The SPR signals from each channel are coupled by an external mirror and the SPR dip shift in the coupled signals is detected by a single spectrometer. Compared to the previous multi-channel SPR sensors using fiber-optic switches or special prisms, the present SPR sensor chips with PDMS nanogratings result in more compact and less expensive SPR detectors. We have designed and fabricated the SPR sensor chips with two channel gratings having the refractive index sensitivity of 321.78 nm/RI and 514.26 nm/RI, respectively. From the fabricated SPR sensor chips, we measure the SPR dip shift of 1.13±0.16 nm for the target biomolecules of 0.5 μM streptavidin binded on a 10% biotinylated surface. The real-time binding reaction rates of m-antibiotin has been monitored for the fixed concentration of 0.2 μM streptavidin as well as for the varying concentration range of 2-50 nM; thus obtaining the results for the fixed and varying concentration in good agreement with those obtained from a commercialized SPR sensor. It is demonstrated that the polymer nanograting SPR sensor chips offer simple and disposable biomolecule detection methods for point-of-care applications. [DOI: 10.1380/ejssnt.2009.750]