Surface Plasma Resonance Sensor Research Articles

Experimental Study of Dual-Parameter SPR Sensor With Integrated Sensing Channel

In order to meet the actual requirements for sensor miniaturization and integration, we propose a compact dual-parameter surface plasma resonance (SPR) fiber sensor, which can simultaneously measure the refractive index and temperature of liquid. The sensor is composed of input-output couplers and two sensing arms. The no-core fibers (NCFs) and microstructured optical fiber (MOF) with deposited films are used as input-output couplers and sensing arms, respectively. One sensing arm is the MOF with silver film for refractive index measurement, and another is that with silver film and PDMS for temperature measurement. Numerical simulation results show its cladding mode is more advantageous in stimulating the SPR effect. Experimental results demonstrate the maximum sensitivity of liquid refractive index is 4139 nm/RIU in the range of 1.333-1.365, and that of liquid temperature is 4.7 nm/°Cin the range of 20-70 °C. The compact structure makes the proposed sensor unique and has a promising application in refractive index and temperature monitoring.

Cu2+-imprinted optical fiber SPR sensor for intelligent recognition.

An optical fiber surface plasma resonance (SPR) sensor with MMF-TCF-MMF structure was designed to realize intelligent recognition of copper ions (Cu2+), and the selective adsorption sensitization was achieved by plating a layer of Cu2+-imprinted film on the surface of gold film excitation layer. Combining the principle of optical fiber interference and SPR, the proposed sensor realized the detection of the copper ions concentration through measuring the refractive index changes caused by ions adsorption on imprinted film. The Cu2+-imprinted optical fiber SPR sensor can realize the intelligent recognition and detection of copper ions in the complex environment and exhibits a detection sensitivity of -10.05 pm/ppm. The proposed sensor has tremendous development potential in practical application, and provides new ideas for the field of metal ions detection.

Simulation of liquid gas and displacement optical fiber sensing system based on vortex beam

This paper attempts to propose an optical fiber sensing system based on the vortex beam, which can be applied to measure liquid refractive index (RI), gas concentration and displacement. Its sensing structure consists of a silver-coated microfiber for surface plasma resonance (SPR) sensors, a fiber aligned with it, and a interference structure for Gaussian beam interfering with the transmitted vortex beam. Due to SPR effect, when the RI of liquid changes, the wavelength of resonance spectrum will shift accordingly, thus the sensitivity of the RI can be achieved. When the gas refractive index n and distance L between two fiber end face change, phase difference will be generated between the transmitted vortex beam and the bypass Gaussian beam. Thereupon, the interference pattern of the two beams will rotate, the measurement of the gas RI and displacement can be achieved. In comparison with the traditional optical fiber SPR sensor, the simulation result shows that SPR excited by the vortex beam is more explicit with higher sensitivity. When the RI of the external environment is 1.385, the sensitivity of 4600 nm/RIU under the condition of Gaussian beam, the sensitivity of sensor based on vortex beam increases to 6800 nm/RIU, which is 47.8% higher. When the RI of the external environment is 1.365–1.385, the average sensitivity of the sensor increases from 3950 nm/RIU to 5100 nm/RIU. Meanwhile, the gas RI sensitivity is 36°/0.0001 RIU and the displacement sensitivity is 36°/ 100 nm. In terms of the CCD angle resolution, the theoretical resolution of gas RI measurement is 1.54e-10 RIU, and the resolution of displacement is 1.54e-4 nm.

SPR sensor based on Bessel-like beam.

A proposal toward the enhancement in the sensitivity of a fiber-based surface plasma resonance (SPR) refractive index (RI) sensor is explored experimentally using a Bessel-like beam as the input source. We splice a section of single-mode fiber and a section of multimode fiber to construct the Bessel-like beam, which contains a series of concentric rings for the consistency of the resonance angle configuration to improve the performance of the SPR sensor. We fabricate a dual-truncated-cone (DTC) structure of the fiber to excite and receive the SPR signals. The larger the number of concentric rings, the higher the sensitivity. The number of concentric ring is determined by the length of the multimode fiber. When the grinding angle of the DTC-sensing probe is 15° and the length of the multimode fiber is 500 µm, the maximum testing average sensitivity is 6908.3 nm/RIU, which is more sensitive than the previous SPR sensor introduced by the Gaussian beam as the input source in multimode fibers.

Theoretical investigation of an enhanced Goos-Hänchen shift sensor based on a BlueP/TMDC/graphene hybrid.

The Goos-Hänchen (GH) shift caused by blue phosphorene/transition metal dichalcogenides (BlueP/TMDCs) and graphene surface plasma resonance (SPR) in Kretschmann configuration are studied theoretically. In this structure, graphene and BlueP/TMDCs coated on Cu thin film are optimized to improve the GH shift. The highest GH shift of sensor Cu-BlueP/WS2-graphene is 1004λ with three layers BlueP/WS2 and a graphene monolayer. For the sensing application, the sensitivity corresponding to the optimal GH shift is 3.199×106λ/RIU, which is 210.8 times higher than the traditional Cu film, 181.4 times higher than the Cu-BlueP/WS2 (monolayer) structure, and 56.6 times higher than the Cu-graphene structure. Therefore, the SPR sensor with high GH shift can be extensively used in the fields of chemical, biomedical, and environmental monitoring.

Damping resonance and refractive index effect on the layer-by-layer sputtering of Ag and Al2O3 on the polystyrene template

In this study, an ordered metal oxide-metal composite system was designed. By changing the thickness of film of Ag/Al2O3 nanoparticles (NPs), the red and blue shifts of local surface plasma resonance (LSPR) were realized in the proposed system and discussed by damping resonance theory and Mie's scattering theory to demonstrating the relationship between wavelength (λ) and particle diameter (D). With the increasing of sputtering time of Ag, the SPR of Ag was red shifted under the influence of damped vibration, obtaining that square of wavelength (λ2) is proportional to D. The surface plasma resonance (SPR) of Ag/Al2O3 showed an obvious blue shift, and then red shift suddenly, which is affected by the competition between damping resonance and refractive index. When the blue shift occurs, the change of wavelength (∆λ) is exponentially related to the diameter (D). The modulation of LSPR of the proposed composite nano-metal materials will have a potential application in SPR sensor and surface enhanced Raman scattering (SERS).

Enhanced sensitivity of fiber SPR sensor by metal nanoparticle

PurposeThis paper aims to clarify the relationship between the performance of the metal nanoparticles and the sensitivity of the fiber surface plasma resonance (SPR) sensor. It proposes modeling the sensing effects of a single-mode fiber SPR sensor with a cone angle structure decorated with metal nanoparticles. This study uses the metal nanoparticles to the realize enhanced sensitivity of refractive index sensing.Design/methodology/approachThis paper opted for an exploratory study using a simulation approach of finite-difference time-domain (FDTD). Specifically, the effect of size, the material and the shape of the metal nanoparticle on sensing performance are investigated theoretically.FindingsIn conclusion, it is evident that the localized SPR (LSPR) effect weakens as the diameter of the gold nanosphere increases, the SPR effect enhances and the SPR sensitivity increases first and then decreases. The metal nanoparticle with the different materials and different shapes also have different LSPR and SPR sensitivity and wavelength length dynamic range. The investigation shows that, by changing parameters, the reflection spectra of the fiber SPR sensor exhibit an obvious transition from LSPR to SPR characteristics, and enhanced sensitivity of the refractive index is realized.Originality/valueThis paper fulfills an identified need to study how the sensitivity of the fiber SPR sensor can be enhanced by the metal nanoparticle. After the optimization of parameters, the sensitivity of 5,140 nm/RIU is achieved, which provides a new research direction for sensitivity enhancement of fiber SPR sensor.

Magnetic Field Sensing Based on SPR Optical Fiber Sensor Interacting With Magnetic Fluid

A novel magnetic field sensing system based on surface plasma resonance (SPR) optical fiber sensor and filled with magnetic fluid (MF) is proposed and demonstrated for the first time. In the magnetic field SPR optical fiber sensor, SPR is excited by Ag as metallic material and MF is filled into the capillary sealed with epoxy glue, which utilizes the tunable refractive index (RI) of MF, and the transmission spectrum will change with different magnetic field intensities. The magnetic-optic effect of MF and the high RI sensitivity of optical fiber SPR sensor are utilized to enhance the sensitivity of the novel magnetic field sensor significantly. In the experiment, the performances of the magnetic field sensing system are tested by applying different measured magnetic fields. The final results indicated that a sensitivity of 303 pm/Gs is achieved. Compared with other optical fiber magnetic field sensors, the advantages of the proposed sensor in this paper are simple structure, small in size, easy to make, low cost, high sensitivity, and anti-interference.

A flow-batch manipulated Ag NPs based SPR sensor for colorimetric detection of copper ions (Cu2+) in water samples

Using flow-batch analysis, a highly sensitive and selective method for automatic colorimetric detection of copper ions (Cu2+) was produced on the basis of the surface plasma resonance (SPR) of silver nanoparticles (Ag NPs). The Ag NPs were catalytically etched by thiosulfate in the presence of Cu(NH3)42+, resulting in a color change of the solution induced by the absorbance decrease at 401nm of the SPR peak of Ag NPs. The proposed method showed high selectivity for Cu2+ over various metallic ions, including Fe3+, Mn2+, Co2+, Ni2+, Zn2+, Pb2+, Ba2+, Cd2+, Bi3+, Sb2+, As3+, Hg2+, Cr3+ and K+. The linear range was 0.5–35μg/L with a coefficient of 0.9954. The limit of detection was as low as 0.24μg/L. The relative standard deviation (RSD, n=7) for the determination of Cu2+ spiked samples at concentrations of 10μg/L was 1.21% and for 25μg/L was 1.03%. The proposed method was successfully applied to analyze Cu2+ in lake water, tap water, rainwater and bottled water samples, as well as leaf samples for food packaging. The results were in good agreement with those obtained by graphite furnace atomic absorption spectrometry, the classical technique.

Yeast cell assay with a surface plasma resonance sensor at multiple penetration depths

We demonstrated a novel yeast cell assay using a multiple depth surface plasmon resonance platform, which has three detection depths. In the study we first identified the minimal and maximum number of cells required for detection and then used the platform to conduct a drug potency study. The study showed that the rank order of potency for 3 drugs could be clearly determined and was the same regardless of the penetration depth used for the measurement. The rank order made sense based on their respective mechanism of action. However the data quality of the inhibition curve was best when measured at the 1500nm depth. The dose dependent response was noticeable even after only 15min treatment, which is much earlier than those from traditional methods. By comparing the response units obtained at 3 different penetration depths in various yeast cell assays, we have confirmed that simultaneously monitoring from multiple penetration depths likely offers advantages to better detect robust signals from yeast cells, which proves difficult with other optical sensors with a short penetration depth of <300nm. The assay could be broadly applicable to other rigid and spherical cell types for biology studies and for antibiotic discovery.

SPR based Studies for Pentagalloyl Glucose Binding to α-Amylase

Abstract Astringency is an organoleptic property resulting mostly from the interaction of salivary proteins with dietary polyphenols. It is of great importance to consumers but being typically measured by sensorial panels it turns out subjective and expensive. The main goal of the present work is to develop a sensory system to estimate astringency relying on protein/polyphenol interactions. For this purpose, a model protein was immobilized on a sensory gold surface and its subsequent interaction with polyphenols was measured by Surface Plasma Resonance (SPR). α-amylase and pentagalloyl glucose (PGG) were selected as model protein and polyphenol, respectively. To ensure specific binding between these, various surface chemistries were tested. Carboxylic terminated thiol decreased the binding ability of PGG and allowed covalent attachment of α-amylase to the surface. The pH 5 was the optimal condition for α-amylase immobilization on the surface. Further studies focus on Localized SPR sensor and application to wine samples, providing objectivity when compared to a trained panel.

Perturbation analysis of fiber surface plasma resonance sensor

AbstractPerturbation method is used to calculate the resonance wavelength shift and the sensitivity of fiber surface plasma resonance sensor. We show that the resonance wavelength always shifts to long wavelength direction as the sensed medium dielectric index increases. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2425–2427, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21956

Adaptive optical design in surface plasma resonance sensor

A double-prism adaptive optical design in surface plasma resonance (SPR) sensor is proposed, which consists of two identical isosceles right-triangular prisms. One prism is used as a component of Kretschmann configuration, and the other is for regulation of the optical path. When double-prism structure is angle-scanned by an immovable incident ray, the output ray will be always parallel with the incident ray and just has a small displacement with the shift of output point. The output ray can be focused on a fixed photodetector by a convex lens. Thus it can be avoided that a prism and a photodetector rotate by θ and 2θ respectively in conventional angular scanning SPR sensor. This new design reduces the number of the movable components, makes the structure simple and compact, and makes the manipulation convenient.