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Fiber optic surface plasmon resonance (SPR) sensor based on copper and tungsten disulfide is presented experimentally. The method of wavelength interrogation is used to analyze the sensor. Outcomes of thicknesses of these materials on the sensitivity of the sensor have been shown in detail. The presence of tungsten disulfide layer of certain thickness in the copper-based sensor has been shown to improve the sensitivity. The SPR sensor with 40 nm thick copper-10 nm thick tungsten disulfide layers exhibits highest sensitivity. [ABSTRACT FROM AUTHOR]

This paper reports a double-sided polished microstructured fiber based on the refractive index that simultaneously measures the refractive index and temperature. Two polished planes were introduced into the cladding. A gold film and polydimethylsiloxane are deposited on one side of the plane for temperature measurements, and graphene layers are coated on the surface of the silver film on the other side for refractive index measurements. The finite element method is used to characterize the sensing characteristics of the sensor. The results show that when the liquid refractive index is from 1.36 to 1.4 and the temperature from 70 °C to 110 °C, the maximum sensitivity of the sensor is 15,000 nm/RIU and 8.8 nm/°C, respectively. The double-sided polished structure facilitates the development of multi-parameter measurement sensors for various applications. [ABSTRACT FROM AUTHOR]

The present study proposes a photonic crystal fiber sensor based on a plasmon resonance. A thin gold metal layer was used as a plasmonic‐active material to produce the surface plasmons to detect changes in the refractive index (RI) around it. The performance of the proposed sensor is evaluated by the finite‐element method for various refractive indices. The sensitivity of this sensor ranges from 3740 to 51227 nm/RIU for the RI range of 1.36–1.42 in the wavelength range of 700–1900 nm. Within this range, we observed the highest resolution, the best FOM, and amplitude sensitivity with values of 1.95 × 10−6 RIU, 883.224 RIU−1, and 2328.59 RIU−1, respectively. This sensor has a simple structure and a better performance as compared with available sensors. The present study opens a new window to studies in the fields of biological materials, chemical materials, and the environment. [ABSTRACT FROM AUTHOR]

In this work, the performance of a single/ bimetal based surface plasmon resonance (SPR) sensor is probed utilizing a two-dimensional heterostructure composed of aluminium nitride (AlN) and transition-metal dichalcogenide (TMDC). The heterostructure is placed on the optimized Silver–Gold bimetal surface instead of single metal to achieve a stable sensor surface and better response. The presence of a high index AlN layer helps to enhance the sensitivity and TMDC material aids to adsorb more target biological molecules, with protection underneath layers from oxidation. To get a better response different heterostructures (AlN–TMDC) are incorporated into the structure and found that AlN–tungsten disulfide (WS2) outperforms others. The observed values of sensitivity, detection accuracy (DA), and figure of merits (FOM) are 179.00063 (°/RIU), 0.7294, and 46.1342 (RIU−1) respectively. Also, the evanescent electric field at the sensor interface provides maximum intensity (1.68E-04 V/nm) which is confirmed by the finite element analysis (FEA). The authors believe that the outcomes of this work will be beneficial to develop a highly sensitive and stable plasmonic device for different healthcare applications. [ABSTRACT FROM AUTHOR]

A new surface plasmon resonance (SPR) mechanism based photonic crystal fiber (PCF) biosensor has been investigated to probe petrol adulteration in the bio-sensing research field. The adulteration level is assumed and measured at normal room temperature (298 K or 25 °C) based on the petrol mixture and concentration in adulterated fuel. The SPR-PCF full vector simulation is run on a simulation software called COMSOL Multiphysics (Version 5.3a) by applying the differential finite element method. The mesh elements are applied at their finest. The geometry of the proposed sensor is optimized by varying the adulteration level of the fuel (10%, 20%, 30%, 40% & 50% concentration), plasmonic layer width, analyte layer length, fiber core diameter, and plasmonic materials (Gold, Niobium, Platinum). The maximum performance of amplitude sensitivity of 320 RIU - 1 and wavelength sensitivity of 7352 nm/RIU are recorded by the optimization of fiber geometry and choosing platinum as plasmonic material for a 10% petrol adulteration level. The proposed PCF sensor has also shown higher linear response. As a result, this SPR-PCF sensor is a worthy candidate for measuring the adulteration of bio-fuel or petrol. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is used in this article to introduce a novel multilayer configuration and investigate its efficacy as a cancer detection sensor. Our proposed structure comprises an analyte-containing sensing layer underneath an alloy (Au–Ag) and a WS2 layer on top. Utilizing angle interrogation for analysis and a BK7 prism set up in the Kretschmann configuration, SPR is induced. Sellmeier equations are utilized to compute reflectivity and additional parameters of the multilayer design. According to our analysis, the maximum sensitivity of 304°/RIU was achieved with alloy metal and 2*WS2 layered SPR sensor configuration, which is significantly higher than recent SPR-based sensors at 662-nm wavelength. The proposed sensor measured the refractive index (RI) of the sensing medium (SM) at 1.399, which is a tiny change, and found a penetration depth (PD) of 189.79 nm. The proposed sensor performance parameters for various cancer types, including skin, cervical, and breast cancers, have been examined. The proposed SPR sensor shows a high potential for accurately detecting different biomolecules, as evidenced by the 39.33/RIU FoM achieved at 1.399 RI of SM with 37 nm thickness of alloy metal layer. [ABSTRACT FROM AUTHOR]

The surface plasmon resonance (SPR) sensing in the ultraviolet (UV) region, achieved through the optimization of aluminum (Al) film conditions, has attracted attention due to its heightened energy levels and more plentiful molecular electronic transitions compared to the visible region. In this research, the stability of the UV-SPR sensor is improved by applying a protective thin layer of gold (Au) onto the Al film. This reduces spectral alterations observed when the Al film was uncoated in water pre and post flow system measurements. This exploration presents the initial experimental confirmation of the reliability of Al-Au bilayer coatings as SPR sensors in the UV region, highlighting advancements in UV-SPR sensor technology. [Display omitted] • Au-coated Al film successfully functions as UV-SPR sensor. • UV-SPR sensor could have high sensitivity due to molecular electronic resonances. • SPR property of Al film without Au layer changed during flow system measurements. • UV-SPR sensor stability enhanced with Au protective layer. • Flow system is introduced to UV-SPR sensor for real-time monitoring. [ABSTRACT FROM AUTHOR]

The features of plasmonic surface frequency sensor technology, such as the small number of sensor samples required, electromagnetic interference, and high sensitivity, have been found to be highly important.. In this paper, a simulation program was created in Matlab_b2018 by adopting Fresnel equations for calculating the reflectivity of the electromagnetic wave between different media. A surface plasmon resonance sensor based on electromagnetic wavelengths within the range (100 nm to 1000 nm) has been proposed. The transfer matrix was used for a system consisting of four different media. The first medium is a semicircular BK7 glass prism, the second medium is a gold layer (40 nm thick), then a bismuth layer of variable thicknes(10–80) nm, and the last medium is air as the sensing medium. The surface plasmon resonance (SPR) technique was adopted based on the Kretschmann configuration in the simulation of the proposed system. The simulation results showed that there is no SPR within the range of wavelengths (100-500nm), while SPR appears in the visible region and in the IR region at wavelengths (900 and 1000nm). The SPR phenomenon starts to weaken gradually with an increase in the thickness of the bismuth layer. The full width at half maximum (FWHM) decreases with the decrease of thickness of bismuth layer. The best value for it is (10) at thickness (d=10 nm) and wavelength (900 nm). While the height (H) of the SPR dip increased, with the best value of (0.95) at thickness (d=10 nm) and wavelength (700 nm). Also, the sensitivity increased with increasing the bismuth layer thickness at wavelengths (700, 800, and 1000 ) nm. The highest obtained sensitivity(S) was (112.5 deg/RIU). [ABSTRACT FROM AUTHOR]

In the traditional surface plasmon resonance sensor, the sensitivity is calculated by the usage of angular interrogation. The proposed surface plasmon resonance (SPR) sensor uses a diamagnetic material (Al2O3), nickel (Ni), and two-dimensional (2D) BlueP/WS2 (blue phosphorous-tungsten di-sulfide). The Al2O3 sheet is sandwiched between silver (Ag) and nickel (Ni) films in the Kretschmann configuration. A mathematical simulation is performed to improve the sensitivity of an SPR sensor in the visible region at a frequency of 633 nm. The simulation results show that an upgraded sensitivity of 332°/RIU is achieved for the metallic arrangement consisting of 17 nm of Al2O3 and 4 nm of Ni in thickness for analyte refractive indices ranging from 1.330 to 1.335. The thickness variation of the layers plays a curial role in enhancing the performance of the SPR sensor. The thickness variation of the proposed configuration containing 20 nm of Al2O3 and 1 nm of Ni with a monolayer of 2D material BlueP/WS2 enhances the sensitivity to as high as 374°/RIU. Furthermore, it is found that the sensitivity can be altered and managed by means of altering the film portions of Ni and Al2O3 [ABSTRACT FROM AUTHOR]

Ochratoxin A (OTA), a group of highly toxic fungal secondary metabolites, is one of the most common mycotoxins that contaminate a wide range of agricultural products. Herein, we designed a label-free and selective surface plasmon resonance (SPR) based sensor for detection of OTA contamination in dried fig. The molecularly imprinted polymer film (MIP) was fabricated onto the SPR sensor chip by using light-initiated polymerization of N-methacryloyl-(L)-phenylalanine and 2-Hydroxyethyl methacrylate in the presence of OTA as a template. SPR chips were characterized by using contact angle, atomic force microscopy, and ellipsometry. OTA imprinted sensor was displayed a broad linear range, between 0.1 ng/mL and 20 ng/mL. The limit of detection was calculated as 0.028 ng/mL. The selectivity studies of the OTA imprinted SPR sensor was performed in the presence of aflatoxin M1, aflatoxin B1, and citrinin. The imprinting factor was found to be 2.85. The adsorption behavior of the OTA imprinted sensor was found as suitable for the Langmuir model. Results displayed that the OTA imprinted SPR sensor was successfully applied to determine OTA in dried fig samples. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a highly toxic gas, which can cause death if it is inhaled in small quantities for a long time or in large quantities for a short time. Since this gas can be lethal, it is essential to detect it from minute to large concentrations. Our study consists of the design of a superficial plasmonic resonance (SPR) CO sensor of tiny dimensions which is capable of giving an immediate response at different concentrations. It is designed to work at different heights above sea level since the refractive index of this gas depends on a mixture with air and the air pressure. Due to its low weight and tiny dimensions, it is ideal for space travel or on airplanes. The results show a high resolution and sensitivity (~10−5 RIU of resolution and a sensitivity of 13.51–81.26 RIU−1). [ABSTRACT FROM AUTHOR]

In an optical fiber based SPR sensor, a segment of metal clad silica fiber is used as the sensing element and resonant coupling occurs to the surface plasmon mode excited at the interface of the metal and ambient which surrounds the sensing element. When polychromatic light is transmitted through the sensing element, the spectrum of light detected at the other end shows minima at a resonance wavelength. In wavelength interrogation, the shift in the resonance wavelength is a measure of change in the refractive index of the ambient. Alternatively, intensity interrogation can be used in which the change in transmitted power at a given wavelength is a measure of change in refractive index of the ambient. The sensitivity and detection accuracy of the sensor depend on the numerical aperture (NA) of the multimode optical fiber used to fabricate the sensor. In the present work, we have carried out a study of the dependence of the sensitivity and detection accuracy on numerical aperture to obtain the optimal value for a multimode optical fiber which is used to fabricate the sensing element under both wavelength and intensity interrogation. For a gold clad sensing element with l/a = 33.33 for the refractive index of the ambient in the range 1.33 to 1.38, the optimized numerical aperture is obtained as NA = 0.2 for spectral interrogation mode. At this optimal value, the sensitivity is estimated to be 4040 nm/RIU and detection accuracy lies between 20 and 48 μm−1. In single wavelength intensity interrogation, at the He–Ne laser wavelength (633 nm), the optimized numerical aperture is obtained as NA = 0.42. Experimental results on a sensing element fabricated with gold coating on the core of a plastic clad silica fiber are also reported. [ABSTRACT FROM AUTHOR]

In this study, we propose a silver-coated (SPR—surface plasmon resonance)-based biosensor for the detection of diesel adulteration for the first time in the field of biosensing. Here, the numerical analysis is done by COMSOL Multiphysics V-5.1 and fully simulation software MATLAB-V16 on 30190 mesh elements, 2792 boundary elements, and 206593 degrees of freedom using finite element method (FEM) at 25 0 C (298 K) for different concentration levels. Moreover, the entire experiment on SPR-PCF is done for the major optical parameters, for instance, birefringence ( B i ), coupling length ( L c ), power fraction ( P f ), confinement loss ( α c ), amplitude sensitivity ( S a ), wavelength sensitivity ( S w ), resolution ( R l ), transmittance ( T x ), transmittance variance ( T v ), relative sensitivity ( S r ), figure of merit (FOM) and resonance ( R 2 ) which are with respect to their corresponding maximum performance profiles of 2.5 × 10 - 3 , 1300 μ m, 99.93%, 1200 –1600 dB/cm, -7950 R I U - 1 , 49941.169 nm/RIU, 6.319 × 10 - 4 RIU, -180 dB, 170 dB/RIU, 97.25%, 980 and 0.98312 at operating wavelength 0.5–2 μ m. Therefore, it is noticed that the proposed sensor can be able to establish itself as one of the toughest candidates in fiber sensing. Also, working procedure of diesel adulteration sensing as we as the entire working procedure by using a SPR platform will be regarded as a novel procedure for diesel sensing in the history of photonics. [ABSTRACT FROM AUTHOR]

We propose two new sensors based on surface plasmon resonance (SPR) and optical fibers to determine the concentration of sucrose in products such as beverages, honey, condensed milk, etc., in real-time during the fabrication process or when the product has been manufactured. The sensors have been made with a hemispherical prism, a layer of MgF2, and another of Ag or Al with the Kretschmann configuration, and they are modulated in intensity. We have optimized these sensors from the modeling of reflectance curves. We have carried out a numerical simulation with these sensors to show how they can detect small changes in the refractive index depending on the concentration of sucrose where the device is immersed. The maximum sensitivity of the sensors is 11.9 RIU−1 and 5.7 RIU−1, the resolutions 1.7 × 10−4 RIU and 7.9 × 10−4 RIU, and the detection limits between 0-78Brix. Moreover, the sensors have an alarm system that is triggered when the sucrose concentration is insufficient or excessive. Data can also be sent in real-time to a remote place. [ABSTRACT FROM AUTHOR]

In the present work, a novel surface plasmon resonance (SPR) sensor consisting of the nickel (Ni) film with hybrid structure of blue phosphorene (BlueP)/transition metal dichalcogenides (TMDCs) is reported. By optimizing the thickness of Ni layer and BlueP/TMDCs, the maximum sensitivity with 270°/RIU for the Ni-BlueP/WS2 is achieved. Use of BlueP/TMDCs layer facilitates the sensitivity due to its high electron concentration, high mobility, optical, and electronic properties. Compared with the conventional Ni-based SPR sensor, the sensitivity of the proposed one is enhanced up to ~ 60.7%. We hope that the SPR sensor has potential application prospects in chemical detection, medical diagnostic, optical sensing, etc. due to its high sensitivity. [ABSTRACT FROM AUTHOR]

Germanium selenide (GeSe) nanosheets are stable and inexpensive and considered to have a great potential for photovoltaic applications, however we have demonstrated that GeSe nanosheets are also promising for sensing technology, in this paper. By spin-coating the GeSe nanosheets on the surface of noble metal (Au), we have obtained a surface plasmon resonance (SPR) sensor with significantly enhanced sensitivity, and the performance of the sensor is closely related to the thickness of the GeSe film. By detecting different refractive index solutions, we have obtained the optimized sensitivity with 3581.2 nm/RIU (which is nearly 80% improvement compared to traditional SPR sensors) and figure of merit with 14.37 RIU−1. Moreover, the proposed SPR sensor was vastly superior in sensing Pb2+ heavy metal ions after coating it with chitosan and GeSe composite. A maximum sensitivity of 30.38 nm/μg/l has been verified, which is nearly six times better than that of conventional SPR sensor. Our results demonstrated that GeSe nanosheets overlayer with modified SPR sensor has its great potential in heavy metal detection and chemical-specific molecular identification.

Abstract The purpose of this work is to investigate theoretically the characteristics of confined electromagnetic modes propagating along the interfaces of a multilayer device. This one dimensional (ID) sensor is formed by stacking a left-handed material (LHM) layer between a SiCt2-glass prism and a dielectric gap layer in contact with gold (Au). The results indicate that the total thickness of the LHM layer and dielectric gap, in optimum conditions, give the ability of tuning significantly the characteristics of the resonant modes correlated to surface plasmons (SPs) propagation along the interfaces of the designed device. By considering two arrangements between LHM and Au, two opposite resonant behaviors observed in p-reflectance spectra are analyzed in the angular interrogation mode and discussed thoroughly.

The utilization of surface plasmon resonance (SPR) sensors for real-time label-free molecular interaction analysis is already being employed in the fields of in vitro diagnostics and biomedicine. However, the widespread application of SPR technology is hindered by its limited detection throughput and high cost. To address this issue, this study introduces a novel multifunctional MetaSPR high-throughput microplate biosensor featuring 3D nanocups array structure, aiming to achieve high-throughput screening with a reduced cost and enhanced speed. Different types of MetaSPR sensors and analytical detection methods have been developed for accurate antibody subtype identification, epitope binding, affinity determination, antibody collocation, and quantitative detection， greatly promoting the screening and analysis of early-stage antibody drugs. The MetaSPR platform combined with nano-enhanced particles amplifies the detection signal and improves the detection sensitivity, making it more convenient, sensitive, and efficient than traditional ELISA. The findings demonstrate that the MetaSPR biosensor is a new practical technology detection platform that can improve the efficiency of biomolecular interaction studies with unlimited potential for new drug development., (© 2024 Wiley‐VCH GmbH.)

In this paper, a graphene-coated surface plasmon resonance sensor is designed for the examination of Rodent urine which is responsible for Leptospirosis bacteria. Rodent urine is considered as sensing medium. Graphene surface is activated by phosphate-buffered saline solution for better attachment of Leptospirosis bacteria on its surface. Oliguria and Polyuria are the Rodent urine with high and low concentrations of Leptospirosis bacteria, respectively. The transfer matrix method is used for the formulation of reflection intensity of p-polarized light. The reflectance curves for angular interrogation are plotted and the results are obtained in terms of sensitivity, detection accuracy, and quality factor. The significantly high sensitivity and detection accuracy for Oliguria distinguishes it from Polyuria having lower sensitivity. [ABSTRACT FROM AUTHOR]

In this paper, we presented surface plasmon resonance (SPR) sensors with high performance consisting prism (BK7), silver (Ag), titanium dioxide (TiO2), hybrid organic-inorganic halide perovskites (CH3NH3PbX3 ≡ MAPbX3, with CH3=M, NH3=A and X=I, Br) and graphene layers. An SPR sensor based on Ag-TiO2-MAPbI3-graphene and an SPR sensor based on Ag-TiO2-MAPbBr3-graphene. The sensitivity of these sensors is compared with a traditional Ag-TiO2-graphene based SPR sensor. The results show that the proposed sensors have a better sensitivity than the traditional one. Moreover, the thicknesses of Ag, TiO2 and MAPbX3 layers have been optimized to achieve the best performance of the sensors. For SPR sensor based on Ag-TiO2-MAPbI3-graphene, the best performance is obtained where the optimized thicknesses of Ag, TiO2 and MAPbI3 are 60 nm, 5nm and 1.5 nm, respectively. For SPR sensor based on Ag-TiO2-MAPbBr3-graphene, the best performance is obtained where the optimized thicknesses of Ag, TiO2 and MAPbBr3 are 60 nm, 5nm and 2.5 nm, respectively. In addition, the number of graphene layers are investigated and optimized to one layer. Also, compared with existing sensors in the literature, the proposed sensors exhibit higher sensitivity, better detection accuracy and greater quality. Lastly, the sensitivity of the proposed sensor in biomedical application is investigated. Reported sensitivity is 0.0212 deg/gl−1 for sensor based on MAPbI3 and sensor based on MAPbBr3. [ABSTRACT FROM AUTHOR]

• A four layered sensor configuration (CaF 2 Prism-Ag-Ti 3 C 2 T x -Sensing medium) is studied at characteristic wavelengths ranging from visible to near infrared regime. • Maximum sensitivity achieved for the proposed sensor is 350.87°/RIU at 532 nm wavelength. • The proposed sensor outperforms over conventional SPR sensors. • Use of MXene (Ti 3 C 2 T x) enhances attachment of bio-analytes due to its unique sensing abilities. • The greater sensitivity is obtained at shorter wavelengths at the expense of detection accuracy. This paper evaluated the performance parameters of a CaF 2 -Ag-MXene-based surface plasmon resonance (SPR) sensor at different wavelengths. The MXene (Ti 3 C 2 Tx) layer is coated on top of the silver (Ag) layer to act as a protective layer against oxidation and to improve the sensitivity and figure of merit (FoM). The proposed sensor could provide novel opportunities for achieving high sensitivity at different wavelengths. At an excitation wavelength of 532 nm, the maximal sensitivity of 350.87°/RIU is achieved. At various wavelengths, a sensitivity of 245.45, 140, and 129.25°/RIU has been attained at 633, 1000, and 1300 nm, respectively. The study also reveals that greater sensitivity is obtained at shorter wavelengths at the expense of detection accuracy. In the study for implementing the proposed sensor, a fabrication perspective is also included. [ABSTRACT FROM AUTHOR]

Abstract An improved glucose sensitive membrane (GSM) is prepared by immobilizing glucose oxidase (GOD) onto a mixture of silica mesocellular foams (SiMCFs) and SiO2 nanoparticles (SiNPs) and then trapping it in a polyvinyl alcohol (PVA) gel. The membrane is coated onto a gold-glass sheet to create a surface plasmon resonance (SPR) sensor. A series of experiments are conducted to determine the optimized parameters of the proposed GSM. For a GSM with a component ratio of SiMCFs: SiNPs = 7: 3 (mass rate), the resonance angle of the sensor decreases from 68.57° to 63.36°, and the average sensitivity is 0.026°/(mg/dL) in a glucose concentration range of 0 mg/dL‒200 mg/dL. For a GSM with a component ratio of SiMCFs: SiNPs = 5: 5 (mass rate), the resonance angle of the sensor decreases from 67.93° to 63.50°, and the sensitivity is 0.028°/(mg/dL) in a glucose concentration range of 0 mg/dL‒160 mg/dL. These data suggest that the sensor proposed in this study is more sensitive and has a broader measurement range compared with those reported in the literature to date.

Carbon monoxide (CO) is a highly toxic gas, which can cause death if it is inhaled in small quantities for a long time or in large quantities for a short time. Since this gas can be lethal, it is essential to detect it from minute to large concentrations. Our study consists of the design of a superficial plasmonic resonance (SPR) CO sensor of tiny dimensions which is capable of giving an immediate response at different concentrations. It is designed to work at different heights above sea level since the refractive index of this gas depends on a mixture with air and the air pressure. Due to its low weight and tiny dimensions, it is ideal for space travel or on airplanes. The results show a high resolution and sensitivity (~10−5 RIU of resolution and a sensitivity of 13.51–81.26 RIU−1).

A graphene-coated U-shaped fiber surface plasmon resonance sensor with high refractive index sensitivity is proposed. With the combination of graphene coating and U-shape design, the proposed sensor exhibits a significantly enhanced sensitivity as compared with the conventional Au-based straight fiber surface plasmon resonance sensor. The refractive index sensitivity of 15.52 μm/RIU (refractive index unit) is achieved by coating monolayer graphene on U-shaped fiber with a bent radius of 1.1 cm. A sensitivity enhancement factor of about 5-fold is obtained when compared with the conventional straight fiber surface plasmon resonance sensor with and without monolayer graphene coating. The effect of Au thickness, number of graphene layers, and the bent radius on the sensor performance was investigated. The high sensitivity of the proposed graphene-coated U-shaped fiber surface plasmon resonance sensor makes it a promising candidate for biosensing and chemical sensing. [ABSTRACT FROM AUTHOR]

We propose two new sensors based on surface plasmon resonance (SPR) and optical fibers to determine the concentration of sucrose in products such as beverages, honey, condensed milk, etc., in real-time during the fabrication process or when the product has been manufactured. The sensors have been made with a hemispherical prism, a layer of MgF2, and another of Ag or Al with the Kretschmann configuration, and they are modulated in intensity. We have optimized these sensors from the modeling of reflectance curves. We have carried out a numerical simulation with these sensors to show how they can detect small changes in the refractive index depending on the concentration of sucrose where the device is immersed. The maximum sensitivity of the sensors is 11.9 RIU−1 and 5.7 RIU−1, the resolutions 1.7 × 10−4 RIU and 7.9 × 10−4 RIU, and the detection limits between 0-78Brix. Moreover, the sensors have an alarm system that is triggered when the sucrose concentration is insufficient or excessive. Data can also be sent in real-time to a remote place.

In this study, the authors present an electromagnetic model of a nanodipole array above a double‐layer Graphene (DLG) operating at Terahertz. The graphene layers deposited between the dielectric mediums are modelled as surface impedances with conductivities described by the Kubo model. The electromagnetic fields are defined by the spectral representation of the periodic Green's function with impedance condition between the mediums. The main objective of this work is to propose an equivalent and analytical electromagnetic model of a nanodipole array above a DLG, which can be used to describe a surface plasmon resonance sensor that operates at the terahertz frequency. As a way of validating the method, the authors compared the proposed model with a software based on the finite element method. In addition, still, as a form of validation, the authors verified the convergence of the method from the spectral analysis of the proposed Green's Function. As results, spatial and spectral parametric analyses are shown as a function of the concentration of nanodipoles in the array, and the chemical potential applied to the graphene layers. In these results, the authors verify the appearance of plasmonic, optical and acoustic modes, and their contributions in the total field. [ABSTRACT FROM AUTHOR]

Maghemite/reduced graphene oxide nanocomposite has been successfully deposited onto the surface of a gold-coated D-shaped optical fiber. The synergetic combination of gold, graphene, and iron oxide nanoparticles has shown enhancement of the resonance field and sensitivity of the fiber-based plasmonic sensor. In particular, the sensor exhibited its capability to detect lead ions (Pb2+) in aqueous solution via monitoring the spectral response of the sensor probe to different concentrations of Pb2+. A sensor sensitivity of 1.2 nm per μg/L was attained at the lowest detected Pb2+ concentration, which is 0.001 ppm (limit of detection). This robust, compact, and highly sensitive fiber-based plasmonic sensor will be of a great interest for an in situ and real-time water safety environmental monitoring. [ABSTRACT FROM AUTHOR]

The purpose of this work is to investigate theoretically the characteristics of confined electromagnetic modes propagating along the interfaces of a multilayer device. This one dimensional (ID) sensor is formed by stacking a left-handed material (LHM) layer between a SiCt2-glass prism and a dielectric gap layer in contact with gold (Au). The results indicate that the total thickness of the LHM layer and dielectric gap, in optimum conditions, give the ability of tuning significantly the characteristics of the resonant modes correlated to surface plasmons (SPs) propagation along the interfaces of the designed device. By considering two arrangements between LHM and Au, two opposite resonant behaviors observed in p-reflectance spectra are analyzed in the angular interrogation mode and discussed thoroughly. [ABSTRACT FROM AUTHOR]

An improved glucose sensitive membrane (GSM) is prepared by immobilizing glucose oxidase (GOD) onto a mixture of silica mesocellular foams (SiMCFs) and SiO2 nanoparticles (SiNPs) and then trapping it in a polyvinyl alcohol (PVA) gel. The membrane is coated onto a gold-glass sheet to create a surface plasmon resonance (SPR) sensor. A series of experiments are conducted to determine the optimized parameters of the proposed GSM. For a GSM with a component ratio of SiMCFs: SiNPs = 7: 3 (mass rate), the resonance angle of the sensor decreases from 68.57° to 63.36°, and the average sensitivity is 0.026°/(mg/dL) in a glucose concentration range of 0 mg/dL‒200 mg/dL. For a GSM with a component ratio of SiMCFs: SiNPs = 5: 5 (mass rate), the resonance angle of the sensor decreases from 67.93° to 63.50°, and the sensitivity is 0.028°/(mg/dL) in a glucose concentration range of 0 mg/dL‒160 mg/dL. These data suggest that the sensor proposed in this study is more sensitive and has a broader measurement range compared with those reported in the literature to date. [ABSTRACT FROM AUTHOR]

Both increasing demand for ultrasensitive detection in the scientific community and significant new breakthroughs in materials science field have inspired and promoted the development of new-generation multifunctional plasmonic sensing platforms by adopting promising plasmonic nanomaterials. Recently, high-quality surface plasmon resonance (SPR) sensors, assisted by two dimensional (2D) nanomaterials including 2D van der Waals (vdWs) materials (such as graphene/graphene oxide, transition metal dichalcogenides (TMDs), phosphorene, antimonene, tellurene, MXenes, and metal oxides), 2D metal−organic frameworks (MOFs), 2D hyperbolic metamaterials (HMMs), and 2D optical metasurfaces, have emerged as a class of novel plasmonic sensing platforms that show unprecedented detection sensitivity and impressive performance. This review of recent progress in 2D nanomaterials-enhanced SPR platforms will highlight their compelling plasmonic enhancement features, working mechanisms, and design methodologies, as well as discuss illustrative practical applications. Hence, it is of great importance to describe the latest research progress in 2D nanomaterials-enhanced SPR sensing cases. In this review, we present some concepts of SPR enhanced by 2D nanomaterials, including the basic principles of SPR, signal modulation approaches, and working enhancement mechanisms for various 2D materials-enhanced SPR systems. In addition, we also demonstrate a detailed categorization of 2D nanomaterials-enhanced SPR sensing platforms and comment on their ability to realize ultrasensitive SPR detection. Finally, we conclude with future perspectives for exploring a new generation of 2D nanomaterials-based sensors. [ABSTRACT FROM AUTHOR]