Fiber Optic Plasmon Resonance Sensor Research Articles

Fabricate a highly sensitive surface plasmon resonance optical fiber sensor based on a D-shape fiber coated with gold (Au) nano-layer

In this study, a D-shape fiber coated with a gold (Au) nano-layer is proposed as the basis for a highly sensitive surface plasmon resonance (SPR) optical fiber sensor that is used to detect the refractive index RI of the glucose solution, with the possibility of using this sensor as a biosensor. By variety side-polishing multimode fiber with different sensing lengths (1 cm, 1.5 cm, and 2 cm) and coating it with a thin layer of 50 nm gold film, the SPR D-shape fiber sensor was developed. The impacts of the sensing area and various residual fiber thicknesses are explored in order to acquire the optimal values of the SPR D-shape fiber sensor. Observations revealed that various concentrations of glucose, ranging from 1% to 9%, were tested on an SPR D-shape fiber sensor, with sensitivity growing to 3.101 au. RIU−1 and linearity reaching 98%. The sensor responded quickly to the refractive index from 1.334 to 1.346 RIU. The future of glucose sensors looks bright with gold-coated D-shaped fiber sensors, they may also work well with other factors like temperature or strain due to their excellent sensitivity, stability, and repeatability.

L-cysteine/MoS2 modified robust surface plasmon resonance optical fiber sensor for sensing of Ferritin and IgG

L-cysteine conjugated molybdenum disulphide (MoS2) nanosheets have been covalently attached to a gold coated surface plasmon resonance (SPR) optical fiber to prepare a robust and stable sensor. Owing to the multifunctionality of the deposited nanosheet conjugate, the antibodies are also covalently conjugated in the subsequent step to realize the design of a SPR optical fiber biosensor for the two important bioanalytes namely, Ferritin and Immunoglobin G (IgG). The different stages of the biosensor preparation have been characterized and verified with microscopic and spectroscopic techniques. A uniform and stable deposition of the L-cysteine/MoS2 nanosheets has allowed the biosensor to be reused for multiple times. Unlike the peeling-off of the MoS2 coatings from the gold layer reported previously in the case of physically adsorbed nanomaterial, the herein adopted strategy addresses this critical concern. It has also been possible to use the single SPR fiber for both Ferritin and IgG bioassay experiments by regenerating the sensor and immobilizing two different antibodies in separate steps. For ferritin, the biosensor has delivered a linear sensor response (SPR wavelength shifts) in the concentration range of 50–400 ng/mL, while IgG has been successfully sensed from 50 to 250 µg/mL. The limit of detection for Ferritin and IgG analysis have been estimated to be 12 ng/mL and 7.2 µg/mL, respectively. The biosensors have also been verified for their specificity for the targeted molecule only. A uniform and stable deposition of the nanomaterial conjugate, reproducibility, regeneration capacity, a good sensitivity, and the specificity can be highlighted as some of key features of the L-cysteine/MoS2 optical fiber biosensor. The system can be advocated as a useful biosensor setup for the sensitive biosensing of Ferritin and IgG.

Highly sensitive self-referenced surface plasmon resonance fiber optic sensor with indium tin oxide/metal/dielectric structure

A highly sensitive self-referenced surface plasmon resonance (SPR) fiber optic sensor with an indium tin oxide (ITO)/metal/dielectric structure is proposed and theoretically analyzed using the transfer matrix method-based numerical simulations. First, the thicknesses of the metal and ITO films are optimized to realize self-referenced sensing with low normalized transmission power at the resonance peak. Then, a thickness-optimized dielectric (TiO2) film is employed on top of the metal film to improve the sensitivity of the proposed self-referenced sensor. In addition, a comparison between the traditional self-referenced sensor and the proposed self-referenced sensor with the dielectric film are carried out. The self-referenced sensor with a 36 nm ITO/37 nm Ag/70 nm TiO2 structure obtains up to 14510 nm/RIU in sensing sensitivity when the refractive index of the analyte varies from 1.33 to 1.37, which is improved by 421% compared with the traditional one without the dielectric. At the same time, the shift of the self-referenced resonance wavelength changes little for the proposed structure. The proposed ITO/metal/dielectric structure-based fiber optic sensor exhibits highly sensitively self-referenced sensing performance in the near infrared band, which can promote its application in the field of biosensors.

Polyelectrolyte-Enhanced Localized Surface Plasmon Resonance Optical Fiber Sensors: Properties Interrogation and Bioapplication

Polyelectrolyte-Enhanced Localized Surface Plasmon Resonance Optical Fiber Sensors: Properties Interrogation and Bioapplication

Surface plasmon resonance optical fiber sensor for relative humidity detection without temperature crosstalk

A new method to overcome temperature crosstalk in humidity detection is proposed in this manuscript, which is realized by integrated surface plasmon resonance (SPR) and Mach-Zehnder (MZ) interference in the same optical fiber detection structure. The proposed sensor is made by photonic crystal fiber and multimode fiber, SPR excited by half coated gold film on one side of photonic crystal fiber, MZ interference is made by photonic crystal fiber without gold film coating and multimode fiber. Graphene quantum dots and polyvinyl alcohol (GQDs-PVA) are adopted as relative humidity sensitive materials. By data demodulation, the sensitivity of proposed sensor to relative humidity is 23 pm/%RH. Compared with other RH sensors, the proposed sensor in this manuscript is high integrated, and overcomes the problems of complex data demodulation, which provides a novel idea for the sensor to overcome crosstalk of other factors.

A Surface Plasmon Resonance Optical Fiber Sensor for Simultaneous Measurement of Relative Humidity and Temperature

In this work, a new method was explored for developing temperature and relative humidity (RH) optical fiber sensors based on surface plasmon resonance (SPR). A SPR optical fiber sensor coated with carboxymethyl cellulose (CMC) and polydimethylsiloxane (PDMS) was proposed for the simultaneous measurement of RH and temperature. The sensor was fabricated by connecting two no-core optical fibers (NCFs) using multimode optical fibers (MMFs). Metal films were deposited on the surface of NCFs and further coated with CMC and PDMS. CMC coating was used for RH sensing based on the change of refractive index (RI) caused by water absorption; PDMS coating was used for temperature sensing based on its RI change with temperature. Univariate analysis showed that there was very weak interaction between RH and temperature measurement. For RH sensing, the sensitivities were −1.230 nm/RH%, −2.932 nm/RH% and −0.431 nm/RH% when RH were 50%~65%, 65%~70% and 70%~80%, respectively; for temperature sensing, the sensitivity was −2.213 nm/°C at 10 °C~50 °C. The proposed sensor can not only respond to both temperature and RH variation, but also compensate the cross sensitivity between the two parameters. It is simple in structure, easy to manufacture and efficient in the simultaneous detection of temperature and RH, which promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

Study of a Surface Plasmon Resonance Optical Fiber Sensor Based on Periodically Grating and Graphene

In this paper an optical fiber sensor based on plasmonic resonance of graphene and periodically grating is designed and investigated. The proposed sensor consists of an optical fiber core coated by a copper film, a periodically grating layer and a mono-layer graphene, respectively. Originality of the design comes from insertion of periodically grating layer accompanied by a mono-layer graphene sheet. The structure is optimized and parameters for best performance are introduced. It is shown that applying the periodically grating results in performance enhancement of the sensor. Parametric study is performed and optimized values of copper and grating thicknesses are calculated. With varying refractive index of sensing layer in the range 1.3–1.36, the proposed sensor is investigated and compared with designs based on plasmonic resonances of copper coated by monolayer graphene. It is shown that with applying periodically grating a maximum sensitivity improvement of 5.1 μ m/RIU is achieved, while Quality Factor and Detection Accuracy are maintained in their reasonable ranges.

Influence of ions on dynamic response of surface plasmon resonance fiber optic sensor

In this paper, the effects of exposed sensing region length on fiber optic sensor based on surface plasmon resonance (SPR) had been experimentally investigated. The refractive index sensitivity of SPR fiber optic sensor increased with increasing refractive index. Compared to other two counterparts, the sensor with short sensing region length of 5mm demonstrated the highest refractive index sensitivity. For the change in the same magnitude of refractive index, this sensor of 5mm sensing region length showed significantly different dynamic response curve when it was exposed to ionic (NaCl solution) and non-ionic (ethanol) solution. This result suggests that ions have dramatic influence on the resonance wavelength of surface plasmon resonance spectrum, due to the interaction of ions with gold film surface. This feature provides a great potential of SPR fiber optic sensor to on-line monitor of flowing solution.

A reliable, sensitive and fast optical fiber hydrogen sensor based on surface plasmon resonance

We report for the first time on the experimental response of a Surface Plasmon Resonance fiber optic sensor based on wavelength modulation for hydrogen sensing. This approach of measuring the hydrogen concentration makes the sensor insensitive to intensity fluctuations. The intrinsic fiber sensor developed provides remote sensing and enables the possibility of multi-points sensing. The sensor consists of a multilayer of 35 nm Au/180 nm SiO2/Pd deposited on a step- index multimode fiber core. The sensitivity and selectivity of the sensor are optimal at a Pd thickness of 3.75 nm. The sensor is sensitive to a hydrogen concentration ranging between 0.5 and 4% H2 in Ar, with a response time less than 15 s.

High-sensitive SPR sensing with Indium Nitride as a dielectric overlay of optical fibers

In this work, an Indium Nitride (InN) dielectric overlay has been used to develop a surface plasmon resonance optical fiber sensor. Although InN is a very promising material in electronics industry, this is the first time that this kind of material is used for optical sensing. The obtained results show an improvement of the reliability and long term stability with respect to previous devices made with the same technology. More remarkably, the sensitivity increases up to 11,800 nm/RIU in the range of outer refractive indices between 1.415 and 1.429, the highest sensitivity achieved with this kind of devices. Therefore, a novel application of the InN to optical fiber sensors is demonstrated. The use of this material would be of great interest to produce new SPR-based devices for chemical and biological sensing.

Absorption as a selective mechanism in surface plasmon resonance fiber optic sensors

A new concept of surface plasmon resonance fiber optic sensor is presented. By tuning the plasmon resonance to a wavelength for which the outer medium is absorptive, a significant variation of the spectral transmittance of the device is produced as a function of the concentration of the analyte. With this mechanism, selectivity can be achieved without the need of any functionalization of the surfaces or the use of recognizing elements, which is a very interesting feature for any kind of chemical sensor or biosensor. Doubly deposited uniform-waist tapered fibers are well suited for the development of these new sensors. Multiple surface plasmon resonance, obtainable in those structures, can be used for the development of microspectrometers based on this principle.

High-resolution refractive index sensing by means of a multiple-peak surface plasmon resonance optical fiber sensor

When a thin metal layer is deposited on a single-mode tapered optical fiber the layer takes a semi-cylindrical shape. The fundamental fiber mode can excite the different hybrid surface plasmon modes supported by the semi-cylindrical metallic shell. As a consequence, the transmission spectrum of the device exhibits multiple resonance peaks with either TE- or TM-polarized light. The positions of those peaks are remarkably shifted when the refractive index of the medium adjacent to the metal layer changes. Experimentally, we have found that by monitoring the first three resonance peaks a refractive index resolution of about 7×10−7 can be achieved. Our devices can be used for high-resolution biosensing.

Enhanced sensitivity of wavelength modulated surface plasmon resonance devices using dispersion from a dye solution

A dispersion technique for enhancing the sensitivity of wavelength modulated surface plasmon resonance devices is presented. Using the dye, 1,1′3,3,3′,3′-hexamethylindodicarbocyanine (HIDC) iodide, which contains a strong absorption band centered in the dynamic range of the surface plasmon resonance coupling wavelength, the sensitivity to the bulk solution refractive index and the detection of analyte near the sensor surface is increased. A quantitative theory for the enhancement effect is derived from the fundamental equation for surface plasmon resonance. Experimental results are presented for a surface plasmon resonance fiber optic sensor. As much as a 4-fold enhancement in the sensitivity of the surface plasmon resonance response was obtained for bulk sucrose solutions, and a 2-fold enhancement was obtained for binding of proteins to the sensor surface. The theoretical analysis shows that it should readily be possible to obtain significantly greater enhancements of the sensitivity.