Surface Plasmon Resonance Based Fiber Optic Sensor Research Articles

Highly selective SPR based fiber optic sensor for the detection of hydrogen peroxide

The present study reports the fabrication and characterization of a surface plasmon resonance (SPR) based fiber optic hydrogen peroxide sensor using enzymatic approach. The sensing probe is fabricated by depositing gold and graphene oxide (GO) layers over the unclad core of an optical fiber followed by the immobilization of catalase enzyme via EDC-NHS coupling. In this probe, gold provides stability and repeatability to the sensor because it does not oxidize in the presence of oxygen environment like silver, GO being of high refractive index enhances the sensitivity of the sensor while the catalase provides specificity to the sensor due to its very specific interaction with hydrogen peroxide. Further, GO also plays an important role in sensing mechanism by interacting with water molecules released from the enzymatic reaction which changes its effective refractive index. GO is synthesized using modified Hummer’s method and characterized by SEM, TEM and AFM. The operation of the fabricated probe is tested for the concentration of hydrogen peroxide ranging from 0–1000 μM. The sensor possesses 55 μM as the limit of detection and its performance is pH dependent. It is highly selective, stable, repeatable and fast in response. The probe being fabricated on optical fiber substrate gives additional advantages of simplicity, miniaturization, online monitoring and remote sensing of hydrogen peroxide. These advantages promise its applications in health monitoring.

Optical Constant Determination of Crosslinked Chitosan-Polyethylene Glycol (PEG) using Attenuated Total Reflection Method by Surface Plasmon Resonance Phenomenon

Application of chitosan as a sensing layer for heavy metal ions in surface plasmon resonance (SPR)-based sensor with Kretschmann configuration has been done extensively using polypyrrole and gruteraldehid. The deposition methods that are very widely used in depositing chitosan onto the sensing surface are spin coating, electrodeposition and dip coating (for SPR based fiber optic sensor). The deposition technique of chitosan-polyethylene glycol (PEG) composite material as sensing layer in SPR based sensor by using the drop-casting method has not been done to the best of our knowledge. In order to use chitosan-PEG composite material as a sensing layer for heavy metal ion detection, it is necessary to determine the optical constant of chitosan-PEG which is deposited by the drop-casting method. The refractive index of chitosan-PEG with mass composition 0.4 grams chitosan and 0.04 grams PEG was determined by attenuated total reflection (ATR) method by utilizing surface plasmon resonance phenomenon on the prism/silver/chitosan-PEG interfaces in Kretschmann configuration. The refractive index then was extracted from the ATR curve by using Winspall software. Based on the experimental result, it was found that the ATR curve was shifted from 44.3° to 68.9° with the presence of a chitosan-PEG layer deposited onto the silver surface, about 0.01 ml in solution form. From the fitting result, it was found that the refractive index of chitosan-PEG was n = 1.32.

Sensitivity enhancement of a lossy mode resonance based tapered fiber optic sensor with an optimum taper profile

In this study, we have presented the design considerations of lossy mode resonance (LMR) based tapered fiber optic sensors for sensitivity enhancement. The study includes the effect of the taper ratio and the taper profile, i.e. exponential-linear, linear, parabolic, gaussian and quadratic, on the sensitivity. Also, we have analyzed the effect of various coating materials on the sensitivity. It is revealed from the analysis that with an increase in the taper ratio, the sensitivity increases. The effect of the taper profile shows that among five profiles considered for comparison, the exponential-linear profile has the maximum sensitivity value whereas the quadratic profile has the lowest value. For indium tin oxide (ITO), for the exponential-linear taper profile, the sensitivity corresponding to the first and second lossy modes is 12.005 µm/RIU (refractive index unit) and 0.8 µm/RIU, respectively, at the taper ratio 1.7; whereas for aluminum doped zinc oxide (AZO), the corresponding values are 0.515 µm/RIU and 0.235 µm/RIU, respectively, at the taper ratio 2.0. For surface plasmon resonance (SPR) based tapered fiber optic sensors, the maximum sensitivity value for the exponential-linear taper profile for platinum is 6.39 µm/RIU at the taper ratio 2.0, whereas for copper its value is 3.665 µm/RIU. At the taper ratio 1.0, i.e. the uniform core, the sensitivity of the LMR based tapered fiber optic sensors using an ITO coating is two times greater than the platinum-coated SPR based fiber optic sensor. Increasing the taper ratio further enhances the sensitivity around 40% when compared to the uniform core fiber optic sensor. Therefore, LMR based tapered fiber optic sensors with the considered optimum design parameters demonstrate around a 2.5-fold enhancement in sensitivity compared with conventionally used SPR based fiber optic sensors, giving an optimum structure for sensitivity enhancement. We believe that this study will find suitable applications in research/industry for those working in the area of chemical and biological sensing.

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.

SPR based fiber optic sensor with bi layers of indium tin oxide and platinum: A theoretical evaluation

Theoretical analysis of surface plasmon resonance (SPR) based fiber optic sensor with bi layers of ITO-Pt is carried out. Sensitivity and figure of merit (FOM) of sensor increase with increase in Pt layer thickness for all thicknesses of ITO layers. Though, for a fixed thickness of Pt layer, sensitivity and FOM are reduced with increase in ITO layer thickness. 50nm ITO–25nm Pt based SPR sensor reveals maximum sensitivity and FOM.

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.

Surface Plasmon Resonance based fiber optic sensor for mercury detection using gold nanoparticles PVA hybrid

ABSTRACT Fabrication of Surface Plasmon Resonance (SPR) based fiber optic sensor for mercury detection utilizing gold nanoparticles (AuNPs)–PVA hybrid as sensing material is reported. Films of citrate capped AuNPs in PVA matrix are prepared and their optical properties are studied. UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and Particle size analysis (DLS) are performed to ascertain the formation of Au-NPs. Aqueous Hg 2+ sensing of citrate capped gold nanoparticles in PVA matrix are investigated. Further SPR based fiber optic sensor has been fabricated using citrate capped AuNPs-PVA hybrid as sensing material. The detection limit of the proposed sensor is found to be 1 ×10 −6 M.

Theoretical analysis of surface plasmon resonance based fiber optic sensor using ITO and ZnO thin films

Surface plasmon resonance (SPR) based fiber optic sensor with bi layers of ITO–ZnO is theoretically analyzed. The top ZnO layer over ITO layer has been shown to improve the sensitivity of SPR sensor. For all thicknesses of ITO layers, the sensitivity enhances with increase in ZnO layer thickness. SPR based fiber optic sensor with bi layers of 50 nm ITO-30 nm ZnO displays the highest sensitivity of 2202 nm/RIU.

Fabrication and Characterization of a SPR Based Fiber Optic Sensor for the Detection of Chlorine Gas Using Silver and Zinc Oxide

A fiber optic chlorine gas sensor working on surface plasmon resonance (SPR) technique fabricated using coatings of silver and zinc oxide films over unclad core of the optical fiber is reported. The sensor probe is characterized using wavelength interrogation and recording SPR spectra for different concentrations of chlorine gas around the probe. A red shift is observed in the resonance wavelength on increasing the concentration of the chlorine gas. The thickness of the zinc oxide film is optimized to achieve the maximum sensitivity of the sensor. In addition to wavelength interrogation, the sensor can also work on intensity modulation. The selectivity of the sensor towards chlorine gas is verified by carrying out measurements for different gases. The sensor has various advantages such as better sensitivity, good selectivity, reusability, fast response, low cost, capability of online monitoring and remote sensing.

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.

SPR based fiber optic sensor for refractive index sensing with enhanced detection accuracy and figure of merit in visible region

We, theoretically, propose a surface plasmon resonance (SPR) based indium tin oxide (ITO)–silver (Ag) coated fiber optic sensing probe for refractive index sensing in visible regime of the electromagnetic spectrum. A comparative study of ITO+Ag coated probe with Ag coated probe and with ITO coated probe using their respective optimized film thicknesses is carried out. We show that the proposed probe is endowed with the better sensitivity characteristic of ITO and better detection accuracy (DA) characteristic of Ag, and can sense change in refractive index with enhanced DA and figure of merit (FOM) in the visible region.

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.