Plasmon Resonance-based Fiber Optic Sensor Research Articles

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

The surface plasmon resonance-based fiber optic sensors: A theoretical comparative study with 2D TMDC materials

In this study, the surface plasmon resonance-based fiber optic sensor using two-dimensional (2D) TMDC materials covering the Au/Ag bimetallic layer has been reported. Since MoS2, MoSe2, WS2, and WSe2 are the most popular ones, they are constructed as the resonant layer of the sensor. The layer-dependencies and heterostructures of the TMDC materials are examined for the determination of their effect on the performance of the SPR sensor. The performance parameters of the SPR sensor, the sensitivity, accuracy, and figure of merit, are calculated with the help of the MATLAB simulations. It is found out that considering the very small change in the refractive index of the sensing medium (0.0025), the monolayer MoSe2 has the highest sensitivity value of 8096 nm/RIU. In contrast, the monolayer WS2 has the highest accuracy and figure of merit values of 0.34 and 136.89 RIU−1, respectively. This study will be benefited for a better understanding of the performance of the SPR based fiber optic sensor depending on the number of layers of TMDC materials and based on their heterostructures.

Fluoride Fiber Sensor With Huge Performance Enhancement via Optimum Radiative Damping at Ag–Al2O3–Graphene Heterojunction on Silicon

Surface plasmon resonance-based fiber optic sensor with multilayer heterojunction is simulated and analyzed. The constituent materials are ZBLAN fluoride core, NaF clad, amorphous Si layer, Ag layer, Al2O3 interlayer, and graphene monolayer. The main idea behind the study is to optimize the radiative damping ( i.e. , optimum radiative damping, ORD) at the Ag–Al2O3–graphene heterojunction in order to enhance the sensor's figure of merit (FOM) as much as possible. The effect of graphene monolayer's presence on sensor's FOM is also examined. Multiple occurrences of ORD may be achieved by coordinated variation of Ag and Al2O3 layer thicknesses along with light wavelength. Among the several prominent ORD conditions, the combination of 45.3-nm-thick Ag layer, 11-nm-thick Al2O3 layer, and 938.7-nm wavelength leads to a massively large FOM of 31806.65 RIU–1. The above FOM of the FOSPR sensor is nearly six times that for the corresponding prism-based SPR sensor ( i.e. , 5500 RIU–1) reported earlier with Al2O3 interlayer and MoS2 monolayer at λ = 1200 nm. Further, the proposed sensor provides substantially greater FOM compared to existing prism-based and FOSPR sensors.

Localized surface plasmon resonance-based fiber-optic sensor for the detection of triacylglycerides using silver nanoparticles.

A label-free technique for the detection of triacylglycerides by a localized surface plasmon resonance (LSPR)-based biosensor is demonstrated. An LSPR-based fiber-optic sensor probe is fabricated by immobilizing lipase enzyme on silver nanoparticles (Ag-NPs) coated on an unclad segment of a plastic clad optical fiber. The size and shape of nanoparticles were characterized by high-resolution transmission electron microscopy and UV-visible spectroscopy. The peak absorbance wavelength changes with concentration of triacylglycerides surrounding the sensor probe, and sensitivity is estimated from shift in the peak absorbance wavelength as a function of concentration. The fabricated sensor was characterized for the concentration of triacylglyceride solution in the range 0 to 7mM. The sensor shows the best sensitivity at a temperature of 37°C and pH 7.4 of the triacylglycerides emulsion with a response time of 40s. A sensitivity of 28.5 nm/mM of triacylglyceride solution is obtained with a limit of detection of 0.016mM in the entire range of triacylglycerides. This compact biosensor shows good selectivity, stability, and reproducibility in the entire physiological range of triacylglycerides and is well-suited to real-time online monitoring and remote sensing.

Dual-channel fiber surface plasmon resonance biological sensor based on a hybrid interrogation of intensity and wavelength modulation.

We investigate an intensity and wavelength modulation combined plasmon resonance-based fiber-optic sensor technology. Composed of gold nanoparticles (GNPs) and sandwich configuration of Au/indium tin oxide (ITO)/Au film, two sensing regions are fabricated separately along with unclad portions of the fiber-optic probe. It can simultaneously monitor both the light intensity from the Au NP channel and the wavelength from the Au/ITO/Au film channel with a single detector. As the refractive index (RI) of the external environment changes, the transmission intensity and resonance wavelength in the two channels are modified, which provides an interrogation of intensity and wavelength modulation. The sandwich film structure is formed using magnetron sputtering technology, and the GNPs functioning as localized surface plasmon resonators are coated on a multimode optical fiber via the layer-by-layer method. The experimental results reveal that the RI sensitivities of the two sensing channels are 334.1% RIU?1 and 1963.2??nm/RIU, respectively. Based on the above sensing design, we conduct real-time and label-free monitoring of IgG/anti-IgG and Con A/RNase B biomolecular interaction. The resonant dips excited by different sensing modes make it more attractive as a multichannel surface plasmon resonance analysis technology, which is valuable in biological and life sciences research and rapid diagnostics.

Simultaneous measurement of refractive index and temperature using a SPR-based fiber optic sensor

A surface plasmon resonance-based fiber-optic sensor for simultaneous measurement of refractive index and temperature of liquid samples is proposed and experimentally demonstrated. The sensor consists of a gold-coated MM-SM-MM optical fiber structure, whose sensitive section was partially covered with polydimethylsiloxane (PDMS) to generate two independent SPR resonance dips in the fiber transmission spectrum. One of the dips is generated by the bare gold-coated fiber section whose wavelength resonance is tuned by the refractive index and temperature of the surrounding medium. The other dip that is exclusively used to monitor the temperature variations of the liquid sample, whose central wavelength at 900nm corresponds to PDMS refractive index at 20°C, is produced by the polymerized gold-coated fiber section. The high refractive index and temperature sensitivity achieved, 2323.4nm/RIU and −2.850nm/°C respectively, the small size, the ease fabrication process, and the bio-compatibility of the proposed device are appealing characteristics that makes it ideal for practical bio-sensing applications.

Theoretical Study of Surface Plasmon Resonance-based Fiber Optic Sensor Utilizing Cobalt and Nickel Films

A surface plasmon resonance (SPR) based fiber optic sensor with cobalt (Co) and nickel (Ni) layers (one layer at a time) is theoretically analyzed. The sensitivity of sensor increases linearly with increase in refractive index of sensing medium for all thicknesses of Co and Ni layers. Besides it, SPR sensor with Co layer has been shown to demonstrate higher sensitivity than that of Ni layer. The usage of Co in place of noble metals (such as gold and silver) curtails the cost of SPR sensor. Optimized thicknesses of Co and Ni layers are found to be 80 nm and 60 nm, respectively.

Monitoring of patient glucose infusion using a surface plasmon resonance-based fiber optic sensor

A surface plasmon resonance (SPR)-based optic fiber monitoring system was introduced in this paper to monitor patients’ infusion process. The SPR-based fiber optic sensor provides a dramatically enhanced flexibility during the monitoring process. The experimental results showed that the spectral shift of sensor is correlated with glucose concentration and its flowing speed. The presence of fatal air bubbles in a glucose infusion solvent is detectable in real time, so that the consequent medical accident is avoidable. This sensor can simultaneously provide the information of liquid concentration and its flowing velocity, and make a judgment on the presence of air bubbles in solution during infusion. It provides experimental guidance on designing and manufacturing a sensor for on-line clinical monitoring systems in the future.

Surface Plasmon Resonance-Based Fiber Optic Sensor for the Detection of Ascorbic Acid Utilizing Molecularly Imprinted Polyaniline Film

An effort for the fabrication and characterization of a fiber optic sensor based on surface plasmon resonance for the detection of ascorbic acid utilizing molecularly imprinted (MIP) polyaniline film has been reported. The probe is fabricated by coating a thin film of silver over the unclad core of an optical fiber which is further coated with the molecularly imprinted polyaniline film using ascorbic acid as template molecule. The MIP layer creates binding sites complementary of the shape and size of the template molecule on the surface. The sensor is characterized for ascorbic acid concentration solution in the range from 10−8 to 10−4 M. A shift of 22 nm in resonance wavelength for this concentration range has been obtained. The concentration of ascorbic acid in the MIP preparation solution is optimized to maximize the sensitivity of the sensor. In addition, the effect of pH of the sample solution of ascorbic acid on the performance of the sensor has been studied and it has been found that the proposed sensor is most sensitive at pH 7.0. The selectivity of the probe has been checked by using different analytes and has found that the probe is highly selective for ascorbic acid. The sensor has various advantages such as fast response, high selectivity and sensitivity, low cost, and can be used for online monitoring and remote sensing applications.

Surface plasmon resonance-based fiber-optic hydrogen gas sensor utilizing palladium supported zinc oxide multilayers and their nanocomposite.

We analyze surface plasmon resonance-based fiber-optic sensor for sensing of small concentrations of hydrogen gas in the visible region of the electromagnetic spectrum. One of the two probes considered has multilayers of zinc oxide (ZnO) and palladium (Pd) while the other has layer of their composite over a silver coated unclad core of the fiber. The analysis is carried out for different volume fractions of palladium nanoparticles dispersed in zinc oxide host material in the nanocomposite layer. For the analysis, a Maxwell-Garnett model is adopted for calculating the dielectric function of a ZnO:Pd nanocomposite having nanoparticles of dimensions smaller than the wavelength of radiation used. The effects of the volume fraction of the nanoparticles in the nanocomposite and the thickness of the nanocomposite layer on the figure of merit of the sensor have been studied. The film thickness of the layer and the volume fraction of nanoparticles in the ZnO:Pd nanocomposite layer have been optimized to achieve the maximum value of the figure of merit of the sensor. It has been found that the figure of merit of the sensing probe coated with ZnO:Pd nanocomposite is more than twofold of the sensing probe coated with multilayers of Pd and ZnO over a silver coated unclad core of the fiber; hence, the sensor with a nanocomposite layer works better than that with multilayers of zinc oxide and palladium. The sensor can be used for online monitoring and remote sensing of hydrogen gas.

Surface Plasmon Resonance-Based Fiber Optic Sensor for the Detection of Low Concentrations of Ammonia Gas

Fabrication and characterization of a highly sensitive surface plasmon resonance-based fiber optic sensor for the detection of low concentrations of ammonia gas have been reported. The sensor probe is fabricated by coating an unclad core of the optical fiber with successive layers of indium tin oxide (ITO) and bromocresol purple (BCP). Increase in the concentration of ammonia gas around the sensing probe increases the resonance wavelength linearly implying that the absorption of ammonia gas by BCP layer increases its refractive index. In addition, ITO layer also contributes to the increase in the resonance wavelength because it is porous and has grains, which allow the reaction products to enter the pores of the ITO layer causing swelling of the layer resulting in mechanical stress and hence increase in the refractive index. To achieve maximum sensitivity of the sensor, the thickness of the BCP layer is optimized and is found to be 70 nm. The sensitivity of the sensor with optimized thickness of BCP layer is 1.891 nm/ppm and is larger than the sensitivity values obtained in the cases of Ag/BCP and Cu/BCP-coated probes for the concentration range 1-10 ppm of the ammonia gas. The selectivity of the probe is checked by carrying out experiments on the probe with different gases and it is observed that the probe is highly selective for ammonia gas. The sensor has many advantages, such as low cost, online monitoring, and remote sensing, due to the fabrication of the surface plasmon resonance probe on an optical fiber.

Numerical simulation of wavelength-modulated surface plasmon resonance-based fiber optic sensor

A systematically theoretical analysis of a surface plasmon resonance (SPR)-based optical fiber sensor is carried out. A three-layer mode (fiber core/gold/sample) is used to simulate the SPR-based optical fiber sensor. Several parameters including the thickness of gold layer, numerical aperture (NA) of fiber, sensing region length and fiber core diameter have been investigated to evaluate the sensitivity and measurement accuracy of sensor. A detailed explanation for the effect of these parameters on the sensor is presented to give a guideline to optimally design the SPR-based optical fiber sensor.

Simulation of a surface plasmon resonance-based fiber-optic sensor for gas sensing in visible range using films of nanocomposites

A surface plasmon resonance-based fiber-optic sensor coated with nanocomposite film for sensing small concentrations of gases in the visible region of the electromagnetic spectrum has been analyzed. The nanocomposites considered are nanoparticles of Ag, Au and indium tin oxide (ITO) with their varying fraction dispersed in the host dielectric matrix of WO3, SnO2 and TiO2. For analysis, the effective indices of nanocomposites are calculated by adopting the Maxwell–Garnett model for nanoparticles of dimensions much smaller than the wavelength of radiation used for investigation. The effects of the volume fraction of nanoparticles in different nanocomposites and the thickness of the nanocomposite layer on the sensitivity of the sensor have been studied. It has been found that the sensor with the ITO–TiO2 coated nanocomposite with a small volume fraction and optimized film thickness possesses higher sensitivity.

Effect of fiber core dopant concentration on the performance of surface plasmon resonance-based fiber optic sensor

In the present work we study the influence of varying concentrations of different fiber core dopants on the sensor performance in terms of sensitivity, signal to noise ratio (SNR) and operating range of surface plasmon resonance (SPR)-based fiber optic sensors. We consider the use of different concentrations of GeO 2, B 2O 3 and mixture of both in the core of plastic cladded silica (PCS) optical fiber. The study is further extended to consider the performance of quenched fiber. We show how sensitivity and signal to noise ratio of surface-plasmon-based fiber optic sensors can be optimized by wisely choosing their fiber core doping.

Sensitivity evaluation of a multi-layered surface plasmon resonance-based fiber optic sensor: a theoretical study

A multi-layered surface plasmon resonance (SPR)-based fiber optic absorption sensor has been studied theoretically. The sensitivity is evaluated for the p-polarized light launched in the fiber using ray approximation. Four-layers configuration is used to excite the surface plasmon wave. The first layer or the medium considered is the core of the fiber. Second and third layers are metallic (silver and gold). The fourth layer or medium is absorbing medium. The effect of the ratio of the thickness of the metallic layers (silver:gold) on the sensitivity of the sensor has been investigated. The sensitivity increases as the silver to gold thickness ratio increases. The gold should be used only to protect silver layer. In addition, the influences of various parameters like numerical aperture (NA), ratio of sensing region length to fiber core diameter, total bimetallic thickness, maximum absorption wavelength, and half maximum width of the sensing medium on the sensitivity of the sensor have been studied. It has been found that the sensitivity is better for the lower off-resonance excitation frequency. Replacing gold by self-assembled monolayers like thiol does not improve sensitivity much. Further, adding ZrO 2 as the fourth layer does not improve the sensitivity of the four layers configuration.