Fiber Optic Surface Plasmon Resonance Research Articles

Online underwater abscission tracking of the ZnO film deposited on the optical fiber surface employing SPR technology

In this work, an optical fiber surface plasmon resonance (SPR) sensing technology is used to monitor the thickness of zinc oxide (ZnO) film in water online, and then study the hydrophilicity of ZnO film deposited by magnetron sputtering. Experimental results show that the ZnO films deposited on the surface of optical fiber, although different in thickness, will eventually detach from the fiber over time in the water. The surface characteristics of ZnO film before and after being soaked in water are compared to prove the existence of abscission of the film. Additionally, ultraviolet (UV) with different wavelengths and intensities affects the hydrophilicity of ZnO, which benefits from the adsorption of water molecules by more oxygen vacancies generated by photogenerated carriers. The ability of 365 nm UV in improving hydrophilicity increases with UV intensity and is much higher than that of 395 nm UV. It has been proved that hydrophilicity affects the performance of ZnO devices, so the proposed method is meaningful for the basic research on surface hydrophilicity and the application of controllable wettability of ZnO films.

Refractive index SPR sensor with high sensitivity and wide detection range using tapered silica fiber and photopolymer coating.

This paper introduces a surface plasmon resonance (SPR) sensor using tapered silica fiber and photopolymer coating for enhanced refractive index (RI) detection. Tapering the silica fiber to a diameter of 10 µm ensures the evanescent wave leaks into a 1.8-µm thick photopolymer film, which increases the average waveguide RI and broadens the RI detection range accordingly. A 50-nm thick single-side gold film is coated on the photopolymer film, exciting SPR and causing less light transmission loss than a double-side gold film. The method avoids the complex microfabrication processes of conventional polymer optical fiber SPR sensors, while the waveguide RI can be controlled by altering the curing time of the photopolymer during fabrication. The sensor has an overall sensitivity of 3686.25 nm/RIU, enabling RI detection of 1.333 - 1.493. Moreover, the sensor has an ultrahigh sensitivity of 6422.9 nm/RIU in the RI range of 1.423 - 1.493. The temperature response is about 1.43 nm/°C at 20 - 50 °C, which has little impact on RI detection. Finally, we demonstrate that the sensor can grade the severity of hepatic steatosis by measuring the RIs of cytoplasm/triglyceride emulsions with superior sensing performance.

Numerical study of a D-shaped optical fiber SPR biosensor for monitoring refractive index variations in biological tissue via a thin layer of gold coated with titanium dioxide

This study aims to explore the numerical analysis of the impact of integrating titanium oxide (TiO2) into a D-shaped optical fiber biosensor based on surface plasmon resonance (SPR). A thin layer of gold (Au) is applied to the flat section of the fiber, which is also coated with a thin layer of titanium dioxide (TiO2). The behavior and performance of the proposed biosensor for use in biological environments are evaluated using the finite element method (FEM). The optical response of SPR-based biosensors is highly dependent on the analyzed medium, enabling the detection of pathogenic cells and abnormalities in biological tissues. This provides high sensitivity and selectivity, as well as real-time detection accuracy and speed. In this study, the biosensor is incorporated into a biological medium with a refractive index that varies with wavelength. A series of simulations have been conducted to plot the spectra of transmissions, absorptions, and dielectric losses obtained in the output of the sensor instrument. From these spectra, the corresponding surface plasmon resonance (SPR) wavelength (λSPR) within the visible-near-infrared band can be determined. Taking into account the various parameters that influence plasmonic interactions, the biosensor's performance parameters, in particular sensitivity and refractive index resolution have been optimized. Our results show that the presence of the TiO2 layer improves the performance of the proposed sensor and offers the possibility of adjusting the resonance wavelength (λSPR). In addition, our proposed sensor can achieve a better resolution of 7.50×10-6[RIU] in 1.34-143 range of analyte refractive index, which notably exceeds that of current technologies. This opens up new prospects in the field of chemical and biological detection.

Quality Enhancement of Fiber Optic Surface Plasmon Resonance Biosensor Consisting of Metal and Barium Titanate Layer by Using Aluminum Alloy in Medical Applications

Quality Enhancement of Fiber Optic Surface Plasmon Resonance Biosensor Consisting of Metal and Barium Titanate Layer by Using Aluminum Alloy in Medical Applications

11-MUA/Ag Modified Large-Core Fiber-Optic SPR Sensing Probe and Its Highly Sensitive Detection for Rabies Virus

11-MUA/Ag Modified Large-Core Fiber-Optic SPR Sensing Probe and Its Highly Sensitive Detection for Rabies Virus

Probe type optical fiber DNA hybridization biosensor based on polyethylenimine and Poly-L-Lysine surface functionalization method

Nucleotide hybridization technology is an effective method for achieving optical-based selective recognition of nucleotides. Unfortunately, the optimal work performance is always restricted by the lack of the coupling method used to bind sensors with nucleotide sequences. In this work, a series of nucleotide hybridization detection experiments based on optical fiber surface plasmon resonance (SPR) are conducted, aimed at comparing the ability to bind nucleotide of Polyethylenimine (PEI) and Poly-L-Lysine (PLL), which are common coupling agents in optical-based nucleotide hybridization study. In our work, qualitative nucleotide measurements using PEI and PLL are carried out in positive order, negative order, and temperature fluctuation, and confirm PEI has a higher work performance in nucleotide-binding and nucleotide-detection. Quantitative determination in the concentration range of 0–100 nmol/L demonstrates the DNA sensitivity reaches 0.13 nm/(nmol/L) and the detection limit (DL) lies in 4.9 nmol/L, which is outstanding compared with similar optical sensors. In this paper, two kinds of nucleotide molecule detection methods based on optical fiber SPR sensing technology with PEI and PLL are proposed and experimentally verified, and the nucleotide-binding capability of PLL and PEI is contrast analyzed according to experimental results for the first time. This study is of great significance for improving the measurement scheme of DNA sensors and the selection of gene carriers for manufacturing DNA complexes.

A high-performance long-range surface plasmon resonance sensor based on the co-modification of carbon nanotubes and gold nanorods

In order to solve the problem that the sensitivity of the optical fiber surface plasmon resonance (SPR) sensor is limited and the full width at half maxima (FWHM) is greatly increased after modification of two-dimensional materials such as carbon nanotubes (CNTs), this paper proposes a Long-Range Surface Plasmon Resonance (LRSPR) Sensors co-modified by CNTs and gold nanorods. Gold nanorods were used to further enhance the sensitivity, and a simple and convenient method was used to excite the LRSPR by using low refractive index UV glue as a dielectric matching layer (DML). Compared with SPR sensor, the FWHM is reduced. The LRSPR sensor produced in this paper has a sensitivity of 5056.35 nm/RIU and a figure of merit (FOM) of 23.52 RIU−1, which are 150.64% and 24.38% higher than conventional SPR sensors, providing a method to achieve high sensitivity and FOM of the sensor. At the same time, the large specific surface area of CNTs and gold nanorods can also improve the biocompatibility of the sensor surface, which makes it have the potential of biosensing. In this paper, the use of UV glue as a DML to excite LRSPR is proposed for the first time.

A polydopamine nanospheres modified fiber optic SPR biosensor for specific detection of C-reactive protein

C-reactive protein (CRP) is a vital inflammatory marker in humans and a key single marker of cardiovascular diseases. In this paper, the concentration of CRP was specifically detected by a polydopamine nanospheres (PDA-NPs) developed surface plasmon resonance (SPR) sensor with high accuracy. PDA-NPs is a self-polymerizing material that can be obtained from dopamine through the mussel adhesion effect. The PDA-NPs (diameter ≈ 100 nm) modified SPR sensor exhibits enhanced refractive index (RI) sensitivity and bio-sensitivity attributed to the large specific surface area and high surface reactivity of the PDA-NPs. The developed sensor demonstrates a RI sensitivity of 2427.68 nm/RIU, presenting a 55.7% increase compared to the raw sensor (RI sensitivity was 1559.08 nm/RIU). Moreover, the developed biosensor is used to detect CRP specifically. The bio-sensitivity reaches 0.09 nm/(µg/mL), while the limit of detection (LOD) reaches 0.22 µg/mL. These findings indicate that the developed biosensor can specifically detect CRP with a low LOD. Therefore, this PDA-NPs modified biosensor has great potential in clinical detection and other bio-detection filed.

Measuring ADAMTS-13 activity to diagnose thrombotic thrombocytopenic purpura: a novel, fast fiber-optic surface plasmon resonance immunoassay

BackgroundThrombotic thrombocytopenic purpura (TTP) is characterized by severe ADAMTS-13 activity deficiency (<10%). Diagnostic testing is challenging because of unavailability, high cost, and expert technician requirement of ADAMTS-13 enzyme assays. Cost-effective, automated fiber-optic surface plasmon resonance (FO-SPR) platforms show potential for developing diagnostic tests. Yet, FO-SPR has never been explored to measure enzymatic activities. ObjectivesTo develop an easy-to-use ADAMTS-13 activity assay utilizing optical fibers to rapidly diagnose TTP. MethodsThe ADAMTS-13 activity assay was designed and optimized using FO-SPR technology based on a previously described enzyme-linked immunosorbent assay setup. A calibration curve was generated to quantify ADAMTS-13 activity in plasma of healthy donors and patients with acute immune-mediated TTP (iTTP), hemolytic uremic syndrome, or sepsis. ADAMTS-13 activity data from FO-SPR and fluorescence resonance energy transfer-based strategies (FRETS)-VWF73 reference assays were compared. ResultsAfter initial assay development, optimization improved read-out magnitude and signal-to-noise ratio and reduced variation. Further characterization demonstrated a detection limit (6.8%) and inter-assay variation (Coefficient of variation, 7.2%) that showed good analytical sensitivity and repeatability. From diverse plasma samples, only plasma from patients with acute iTTP showed ADAMTS-13 activities below 10%. Strong Pearson correlation (r = 0.854) between FO-SPR and reference FRETS-VWF73 assays were observed for all measured samples. ConclusionsA fast ADAMTS-13 activity assay was designed onto automated FO-SPR technology. Optimization resulted in sensitive ADAMTS-13 activity measurements with a detection limit enabling clinical diagnosis of TTP within 3 hours. The FO-SPR assay proved strong correlation with the reference FRETS-VWF73 assay. For the first time, this assay demonstrated the capacity of FO-SPR technology to measure enzymatic activity in pre-clinical context.

Optical fiber SPR biosensor with frequency multiplexing compensated laser heterodyne feedback for ultrasensitive detection of fluoroquinolones

The widespread usage and discharge of fluoroquinolones (FQs) have caused negative environmental consequences that can threaten human health. The development of ultrasensitive and simple devices for detection of various FQs is an important requirement. Here, we proposed a novel optical fiber surface plasmon resonance biosensor to achieve the ultrasensitive detection of FQs, in which the frequency-shifted light returned to the laser resonator and stimulated laser heterodyne feedback interferometry to amplify the intensity changes caused by the refractive index (RI) variations. In addition, we further presented a quasi-common path frequency multiplexing compensation method to compensate for the noise of the developed biosensor, resulting in a RI resolution of 1.06 × 10−6 RIU. Besides, the gold nanorods were used to generate localized surface plasmon resonance to further amplify the signal to achieve the ultrasensitive detection. A variety of FQs were detected with ultra-low detection limits, including enrofloxacin (0.61 ng/L), ciprofloxacin (0.54 ng/L), norfloxacin (0.31 ng/L), pefloxacin (0.32 ng/L), and sarafloxacin hydrochloride (0.97 ng/L). With the advantages of high sensitivity, compact size, and remote operation capability, the developed biosensor holds the promise of detecting other antibiotics with universality in hard-to-reach spaces, thus having the potential to demonstrate a promising approach to environmental monitoring.

A L-glutamine binding protein modified MNM structured optical fiber biosensor based on surface plasmon resonance sensing for detection of L-glutamine metabolism in vitro embryo culture

A surface plasmon resonance (SPR) optical fiber sensor with multimode-coreless-multimode (MNM) structure was developed, which modified by L-glutamine-binding protein (QBP) for detection of L-glutamine (Gln). The QBP was immobilized on the surface of gold films by chemical cross-linking and exhibited a binding affinity for L-glutamine. The conformation of QBP can be changed from the “open” to the “closed”, which led to a red-shift of the SPR peak when QBP bounded to L-glutamine. There was a good linear correlation between is a dependence of the SPR peak on and the concentration of L-glutamine concentration in the range 10–100 μM, with a sensitivity of 10.797nm/log10[Gln] for L-glutamine in the in vitro embryo culture (IVC) medium environment, and the limit of detection (LOD) is 1.187 μM. This QBP-modified MNM structure optical fiber SPR sensor provides a new idea for the developmental potential assessment of embryos in the process of in vitro embryo culture.

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.

Polarization-independent tilted fiber Bragg grating surface plasmon resonance sensor based on spectrum optimization.

We experimentally demonstrated polarization multiplexing schemes in a tilted fiber grating (TFBG) to achieve polarization-independent fiber-optic surface plasmon resonance (SPR) sensors. The first used two orthogonal polarized lights separated by a polarization beam splitter (PBS) that are p-polarized in polarization-maintaining fiber (PMF) and precisely aligned with the tilted grating plane, so as to achieve the transmission of p-polarized light in two opposite directions of the Au-coated TFBG to excite SPR. Alternatively, polarization multiplexing was also achieved by exploring two polarization components to achieve the SPR effect through a Faraday rotator mirror (FRM). The SPR reflection spectra are polarization-independent of the light source and any perturbations to fibers, which are explained by the superposition of p- and s-polarized transmission spectra in equal proportions. The spectrum optimization is presented to reduce the proportion of the s-polarization component. A polarization-independent TFBG-based SPR refractive index (RI) sensor with a wavelength sensitivity of 555.14 nm/RIU and an amplitude sensitivity of 1724.92 dB/RIU for small changes is obtained, exhibiting unique advantages of minimizing the polarization alterations by mechanical perturbations.

An axisymmetric metal and metal-oxide grating-structured self-reference fiber optic SPR sensor

An optical-fiber-based surface plasmon resonance (SPR) sensing probe consisting of axisymmetrical grating is proposed and studied theoretically for the detection of the refractive index (RI). The sensing probe is formed by depositing a plasmonic metal layer on a bare core of optical fiber, followed by an axisymmetric grating layer and an analyte. The grating consists of metal and metal oxide in an alternate manner. The proposed structure of a single channel provides two resonance modes in the transmission SPR spectra. It is found that the mode present at the lower wavelength remains fixed, and the mode present at the higher wavelength is varied when the RI of the analyte is varied, so that the previous one works as a reference mode while the latter one works as a sensing mode. These properties provide the self-referencing capability of the proposed RI sensor in ambient conditions. We have calculated the sensitivity, detection accuracy (DA) and signal to width ratio (SWR) using the SPR spectra of various probes of different combinations of plasmonic metal and metal-oxide gratings to enhance the study. The best performing probe is found to be Ag/Cu-ITO. This optimum probe attained a maximum SWR of 42, sensitivity of 5400 nm RIU−1 and DA of 0.08 nm−1 with the self-referencing capability. The optimum probe also works well for a dispersive analyte within the spectral range. The use of metal oxide provides better adsorption of the analyte as well as high sensitivity. The cumulative properties of self-referencing and the metal oxide of the designed probe make it accurate and useful for the detection of biological elements in the ambient atmosphere.

A Field-Enhancement Optical Fiber SPR Sensor Using Graphene, Molybdenum Disulfide, and Zinc Oxide

Graphene, molybdenum disulfide (MoS $$_2$$ ), and zinc oxide (ZnO) are proposed here to enhance the evanescent field of an optical fiber surface plasmon resonance (SPR) sensor. Gold and silver are the plasmonic materials, and the fiber core material is made of polymethylmethacrylate (PMMA). A Fresnel equations-based analysis is used, and the obtained results pointed out higher values of sensitivity, figure of merit, and FWHM (full-width at half maximum) when compared to conventional SPR sensors. In despite of silver-only based SPR sensor has a better performance, oxidation occurs, and the sensor’s lifetime is reduced. The addition of graphene layers leads to sensitivity values $$50\%$$ higher than the conventional sensor. On the other hand, the MoS $$_2$$ -based sensor improves the interaction of the sensor with the bio-recognition molecules, which is attractive for biomedical applications. When ZnO was added to the silver-based sensor, a highest sensitivity, 4740.9 nm/RIU, was obtained. Graphene-based silver SPR exhibit the highest FOM values.

Fiber Optic Localized Surface Plasmon Resonance Sensor Based on Carboxymethylated Dextran Modified Gold Nanoparticles Surface for High Mobility Group Box 1 (HMGB1) Analysis

Rapid, sensitive, and reliable detection of high mobility group box 1 (HMGB1) is essential for medical and diagnostic applications due to its important role as a biomarker of chronic inflammation. Here, we report a facile method for the detection of HMGB1 using carboxymethyl dextran (CM-dextran) as a bridge molecule modified on the surface of gold nanoparticles combined with a fiber optic localized surface plasmon resonance (FOLSPR) biosensor. Under optimal conditions, the results showed that the FOLSPR sensor detected HMGB1 with a wide linear range (10-10 to 10-6 g/mL), fast response (less than 10 min), and a low detection limit of 43.4 pg/mL (1.7 pM) and high correlation coefficient values (>0.9928). Furthermore, the accurate quantification and reliable validation of kinetic binding events measured by the currently working biosensors are comparable to surface plasmon resonance sensing systems, providing new insights into direct biomarker detection for clinical applications.

Plasmonic Resonance Coupling of Nanodisk Array/Thin Film on the Optical Fiber Tip for Integrated and Miniaturized Sensing Detection.

Fiber-optic surface plasmon resonance (FOSPR) sensing technology has become an appealing candidate in biochemical sensing applications due to its distinguished capability of remote and point-of-care detection. However, FOSPR sensing devices with a flat plasmonic film on the optical fiber tip are seldom proposed with most reports concentrating on fiber sidewalls. In this paper, we propose and experimentally demonstrate the plasmonic coupled structure of a gold (Au) nanodisk array and a thin film integrated into the fiber facet, enabling the excitation of the plasmon mode on the planar gold film by strong coupling. This plasmonic fiber sensor is fabricated by the ultraviolet (UV) curing adhesive transferring technology from a planar substrate to a fiber facet. The experimental results demonstrate that the fabricated sensing probe has a bulk refractive index sensitivity of 137.28 nm/RIU and exhibits moderate surface sensitivity by measuring the spatial localization of its excited plasmon mode on Au film by layer-by-layer self-assembly technology. Furthermore, the fabricated plasmonic sensing probe enables the detection of bovine serum albumin (BSA) biomolecule with a detection limit of 19.35 μM. The demonstrated fiber probe here provides a potential strategy to integrate plasmonic nanostructure on the fiber facet with excellent sensing performance, which has a unique application prospect in the detection of remote, in situ, and in vivo invasion.

U-fiber-based biosensor for temperature-compensated acetylcholine-specific measurement.

This paper presents a U-fiber-based biosensor to achieve temperature-compensated acetylcholine-specific measurement. The surface plasmon resonance (SPR) and multimode interference (MMI) effects are simultaneously realized in a U-shaped fiber structure for the first time, to the best of our knowledge. The experimental results show refractive index (RI) sensitivities of 3042 and 2958 nm/RIU and temperature sensitivities of -0.47 and -0.40 nm/°C for the MMI and SPR, which are greatly improved compared with the traditional structure. Simultaneously, a sensitivity matrix for detecting two parameters is introduced to solve the problem of temperature interference of biosensors based on RI changes. Label-free detection of acetylcholine (ACh) was achieved by immobilizing acetylcholinesterase (AChE) on optical fibers. The experimental results show that the sensor can realize the specific detection of acetylcholine and has good stability and selectivity, and the detection limit of the sensor is 30 nM. The sensor has the advantages of simple structure, high sensitivity, convenient operation, direct insertion into small spaces, temperature compensation, etc., which provide an important supplement to traditional fiber-optic SPR biosensors.

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.

Optimization of tapered optical fiber sensor based on SPR for high sensitivity salinity measurement

High sensitivity detection of seawater salinity has important practical significance. SPR fiber optic sensors based on tapered fiber optic have high sensitivity to refractive index and are widely used in fields such as physics, chemistry, and biology. In this paper, a tapered fiber optic was prepared using a fusion tapering process, and the morphology of the SPR sensor was optimized by adjusting three important parameters: taper length, waist diameter, and coating thickness. The influence of these factors on the sensor performance was studied through simulations. Based on the quality factor as the main evaluation criterion, a tapered fiber optic SPR sensor with a taper length of 27 mm, waist diameter of 25 μm, and coating thickness of 40 nm (Au) was selected through experiments. This sensor was used to detect seawater salinity, and its sensitivity reached 0.708 nm/‰ with good linearity. The experiment also proved the long-term effectiveness of the sensor.