Fiber Based Surface Plasmon Resonance Research Articles

A Highly Sensitive D-Shaped PCF-SPR Sensor for Refractive Index and Temperature Detection.

A novel highly sensitive D-shaped photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor for dual parameters of refractive index and temperature detecting is proposed. A PCF cladding polishing provides a D-shape design with a gold (Au) film coating for refractive index (RI) sensing (Core 1) and a composite film of silver (Ag) and polydimethylsiloxane (PDMS) for temperature sensing (Core 2). Comsol Multiphysics 5.5 is used to design and simulate the proposed sensor by the finite element method (FEM). The proposed sensor numerically provides results with maximum wavelength sensitivities (WSs) of 51,200 and 56,700 nm/RIU for Core 1 and 2 as RI sensing while amplitude sensitivities are -98.9 and -147.6 RIU-1 with spectral resolution of 1.95 × 10-6 and 1.76 × 10-6 RIU, respectively. Notably, wavelength sensitivity of 17.4 nm/°C is obtained between -20 and -10 °C with resolution of 5.74 × 10-3 °C for Core 2 as temperature sensing. This sensor can efficiently work in the analyte and temperature ranges of 1.33-1.43 RI and -20-100 °C. Due to its high sensitivity and wide detection ranges, both in T and RI sensing, it is a promising candidate for a variety of applications, including chemical, medical, and environmental detection.

Advances in 4-Nitrophenol Detection and Reduction Methods and Mechanisms: An Updated Review.

This review emphasizes the progress in identifying and eliminating para-nitrophenol (4-NP), a toxic organic compound. It covers various strategical methods and materials, including organic and inorganic nanomaterials, for detecting and reducing 4-NP. Detection techniques such as electrochemical methods. Optical fiber-based surface plasmon resonance and photoluminescence, as well as the mechanisms of Förster Resonance Energy Transfer (FRET) and Inner Filter Effect (IFE) in fluorescence detection, are presented. Removal techniques for this contaminant include homogeneous catalysis, electrocatalysis, photocatalysis, and thermocatalysis, and their reaction mechanisms are also discussed. Further, the theoretical perspectives of 4-NP detection and reduction, parameters influencing the activities, and future perspectives are also reviewed in detail.

Side-Opened Hollow Fiber-Based SPR Sensor for High Refractive Index Detection.

To facilitate the sensor fabrication and sensing operation in microstructured optical fiber-based surface plasmon resonance (SPR) sensors for high refractive index (RI) detection, we propose a special hollow fiber-based SPR sensor that comprises an opening on its body side and a thin gold layer coated on its outer surface. The analyte is able to flow into the hollow core through the side-opening to form new fiber core, with the Gaussian-like mode propagating in it. We investigate the sensing performance of the proposed sensor in a higher RI range of 1.48 to 1.54 at two feasible schemes: one is to only fill the fiber core with analyte (Scheme A), and the other is to directly immerse the sensor in the analyte (Scheme B). The results demonstrate that our sensor exhibits higher wavelength sensitivity at Scheme A with a maximum wavelength sensitivity of 12,320 nm/RIU, while a greater amplitude sensitivity was found at Scheme B with a maximum amplitude sensitivity of 1146 RIU-1. Our proposed sensor features the advantages of simple fabrication, flexible operation, easy analyte filling and replacing, enhanced real-time detection capabilities, high RI detection, and very high wavelength sensitivity and amplitude sensitivity, which makes it more competitive in SPR sensing applications.

Sensitivity enhancement in erbium-doped fiber laser intra-cavity SPR sensor

To enhance sensitivity of fiber-based surface plasmon resonance (SPR) sensor for refractive index detection, we propose a concept of fiber laser intra-cavity SPR sensor that is constructed by placing a hollow fiber-based SPR sensor in an erbium-doped fiber laser cavity. The hollow fiber-based SPR sensor is firstly designed and optimized to achieve maximum amplitude sensitivity of 65.576 RIU−1 in a detection range of 1.6–1.61 at the operation wavelength of 1530 nm, and then placed in the erbium-doped fiber laser cavity to form the fiber laser intra-cavity SPR sensing system. The relationships between the detection sensitivity, pump power, and SPR sensor length of the laser intra-cavity SPR sensor are investigated in detail by using three-level rate equations, and the numerical results demonstrate that the sensitivity is enhanced 82 times, achieves 5375.627 RIU−1 when the fiber-based SPR sensor is placed in the laser cavity, and can be further enhanced by tuning the pump power to close to threshold value. The work described here demonstrates a possible solution to enhance the sensitivity by combining the fiber-based SPR sensor and the fiber laser.

Highly sensitive photonic crystal fiber based surface plasmon resonance biosensor for detection of wide range of organic solutions

This study introduces a dual-core photonic crystal fiber incorporating a highly responsive plasmonic refractive index (RI) sensor. The performance of the RI sensor is evaluated based on amplitude sensitivity, wavelength resolution, wavelength sensitivity, and the linearity of the resonance wavelength. Employing the finite element technique (FEM), a numerical analysis of the proposed design is conducted. Results indicate that employing the amplitude interrogation method yields a peak amplitude sensitivity of 605.82 RIU−1 for y-polarization. Furthermore, the wavelength interrogation approach for y-polarized modes demonstrates a maximum wavelength sensitivity of approximately 17,000 nm/RIU and a maximum wavelength resolution of 5.88 × 10−6 RIU. The proposed sensor exhibits a figure of merit of approximately 298 and effectively responds to refractive index variations within the range of 1.28 to 1.40. These promising outcomes, coupled with the broad sensing range, establish the suggested sensor as a promising candidate for the detection of organic chemical solutions.

Cascaded plastic optical fiber based SPR sensor for simultaneous measurement of refractive index and temperature.

A cascaded side-polish plastic optical fiber (POF) and FONTEX optical fiber based surface plasmon resonance (SPR) sensor is proposed for simultaneous measurement of refractive index (RI) and temperature. The side-polish POF and FONTEX optical fiber are connected by using the UV glue in a Teflon plastic tube. The SPR phenomenon can be excited at both of the side-polish region and the FONTEX fiber cladding. The polydimethylsiloxane (PDMS) is coated on the side-polish POF to get a temperature sensing channel. Due to the low RI sensitivity of the FONTEX optical fiber, the cascaded fiber sensor can obtain a broader RI measurement range with a low crosstalk. An RI sensitivity of 700 nm/RIU in the RI measurement range of 1.335-1.39 and a temperature sensitivity of -1.02 nm/°C measured in deionized water with a range of 20-60 °C are obtained. In addition, the cascaded POF based SPR sensor has potential application prospects in the field of biochemical sensing.

Design and Analysis of High-Performance Optical Fiber-Based Surface Plasmon Resonance Sensor for Early Detection of Colorectal Cancer

Design and Analysis of High-Performance Optical Fiber-Based Surface Plasmon Resonance Sensor for Early Detection of Colorectal Cancer

Design and analysis of arc-shaped single core photonic crystal fiber sensor based on surface plasmon resonance

The selection of a suitable plasmonic material is crucial for achieving high-performance photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensors. However, most numerical investigations have been limited to PCF-SPR sensors with conventional circularly coated plasmonic metals due to their availability and rigid properties. In this work, a single-core arc-shaped PCF is designed and studied with sensing ingredients coated outside the fiber. The simulation and numerical analyses are performed using the full-vector finite element method to examine the effects of using gold as an active metal and also the deposition of Ta2O5 on gold. The results show that the arc-shaped sensor with gold film can obtain the maximum wavelength interrogation sensitivity (WIS) of 9500 nm/RIU within the refractive index (RI) range of 1.25–1.39 while the maximum amplitude interrogation sensitivity (AIS) reaches 579.26 RIU−1 at 1.39 and resolution is 1.05 × 10−5. However, depositing Ta2O5 on the gold gives an improved maximum WIS and AIS of 22,000 nm/RIU and 1209.21 RIU−1, respectively. With the coating of Ta2O5, the resolution improves to 4.55 × 10−6, making the proposed sensor design undoubtedly effective in detecting food chemicals such as butyl acetate and hydrocarbons along with different bio-analyte samples with a wide range of RI.

High refractive index sensing highly sensitive and low loss SPR sensor based on hollow-core D-shaped optical fiber

A hollow-core D-shaped optical fiber-based surface plasmon resonance (SPR) sensor for low-loss and highly sensitive liquid analytes detection is theoretically investigated. The gold (Au) metal nanolayer is coated on the cladding etched D-shaped flat surface to develop the plasmonic effect. The nanolayer coating on the outer flat surface is very easy compared to the inside hollow-core, so our hollow-core sensor manufacturing is too easy compared to other hollow-core refractive indices (RIs) detection sensors. The resonance effect between analytes filled fundamental guided core mode and surface plasmon polariton mode of the D-shaped hollow-core optical fiber sensor is used to obtain the detections of analytes RIs variations. We have found good linear results ([Formula: see text]) in analytes RIs versus resonance wavelength for gold layers thicknesses for the analytes RIs range of 1.45–1.52. This hollow-core D-shaped optical fiber sensor achieves the maximum wavelength sensitivity of 23500[Formula: see text]nm RIU[Formula: see text] and a corresponding resolution of [Formula: see text] RIU. We have obtained the maximum figure of merit (FOM) of 228 1/RIU. The proposed sensor may be highly active in detecting the biological and chemical liquid analytes.

A comparative analysis of fiber-based surface plasmonic resonance sensors utilizing various fluoride glass cores and the influence of different oxide layers on the sensor performance in near-infrared

In a fiber-based surface plasmon resonance (SPR) sensor, with multiple layers, including fluoride glass core, cladding, metal (Ag), graphene and alcohols as the analyte, we focused on comparing the effects of 12 different types of fluoride glass cores from three main groups of fluorozirconate (ZrF4-based), fluoroaluminate (AlF3-based) and fluoroindate (InF3-based). The comparison was conducted to evaluate the sensor’s sensitivity and figure of merit (FOM) at specific near infrared (NIR) wavelengths (785 nm, 852 nm, 895 nm and 980 nm) while keeping other parameters constant. The highest FOM was consistently observed at the wavelength of 980 nm for all three categories of fluoride glass cores. Among them, the fluoride glass core IZBSC (40 InF3-20 ZnF2-15 BaF2-20 SrF2-5 CaF2) from InF3-based group presented the largest FOM = 1459.15 RIU−1. Furthermore, we observed that the FOM of the fiber types belonging to the ZrF4-based and InF3-based categories increased with the wavelength. However, the fluoroaluminate fibers showed different trend and they also exhibited the smallest FOM values at 852 nm, 895 nm and 980 nm wavelengths. To enhance the sensor’s performance, we explored the incorporation of an oxide layer into the to the SPR sensor with a ZBLAN (55.8 ZrF4-14.4 BaF2-5.8 LaF3-3.8 AlF3-20.2 NaF) core. We analyzed the effects of various oxide coatings (Sc2O3, Lu2O3, Al2O3, GeO2, TeO2, Ta2O5, MgO, TiO2, and ZnO) on the Ag layer, which has not previously studied, to the best of our knowledge. Among the different oxide coatings, the Ta2O5 layer, with optimized thickness, exhibited a significant enhancement, achieving FOM of 1631.43 RIU−1.

Air-silica core microstructured optical fiber-based SPR sensor for temperature and refractive index measurement

We propose an air-silica core microstructured optical fiber-based surface plasmon resonance (SPR) sensor to simultaneously measure temperature and refractive index (RI). The sensing channel is formed by coating the outside of the fiber with a gold film and a polydimethylsiloxane (PDMS) layer as a temperature sensing medium, and then being immersed into the liquid analyte. The plasmon mode can penetrate through the PDMS layer and then into the analyte, therefore both the temperature and the analyte RI changings can lead to the variations of SPR spectra that will be measured. Our numerical results demonstrate that the proposed sensor can support two resonance peaks in the x-polarized core mode and one resonance peak in the y-polarized core mode, therefore providing two detection approaches, peak-based and polarization-based approaches. By measuring the two peaks in the x-polarized core mode, for the peak-based approach, the temperature coefficients are −2.077 nm/°C and −2.723 nm/°C, and the RI coefficients are 1252 nm/RIU and 1931 nm/RIU, respectively. While by measuring the second peak in x-polarized core mode and the peak in y-polarized core mode, for the polarization-based approach, the temperature coefficients are −2.723 nm/°C and −3.401 nm/°C, and the RI coefficients are 1931 nm/RIU and 2973 nm/RIU, respectively.

Performance comparison and analysis of D-type single and dual-core PCF-SPR sensors

Surface plasmon resonance sensors, based on photonic crystal fibers, have demonstrated immense potential in various application fields, owing to their structural design flexibility, operability, and superior sensing capabilities. Despite the potential, the design of photonic crystal fibers with various structures has been a challenging task, due to manufacturing constraints. Thus, this paper aims to explore the design rules of photonic crystal fibers based on surface plasmon resonance, by proposing and designing four photonic crystal fiber sensors with distinct structures. The study investigates the influence of single-core, double-core, and large and small air holes on the sensor’s performance, through theoretical analysis, numerical simulation, data acquisition, and analysis. Through our research, we have discovered that by altering the size of pores surrounding the fiber core, as well as the fiber core’s single-mode and dual-mode configurations, we were able to increase the sensitivity of the sensor from its lowest value of 266 nm RIU−1 to as high as 2066 nm RIU−1, an improvement of nearly eightfold. The findings suggest that the sensor with double-core air hole structure exhibits relatively better performance. This analysis is expected to aid in the design of high-performance photonic crystal fiber-based surface plasmon resonance sensors.

Ultrasensitive and Specific Clustered Regularly Interspaced Short Palindromic Repeats Empowered a Plasmonic Fiber Tip System for Amplification-Free Monkeypox Virus Detection and Genotyping.

The urgent necessity for highly sensitive diagnostic tools has been accentuated by the ongoing mpox (monkeypox) virus pandemic due to the complexity in identifying asymptomatic and presymptomatic carriers. Traditional polymerase chain reaction-based tests, despite their effectiveness, are hampered by limited specificity, expensive and bulky equipment, labor-intensive operations, and time-consuming procedures. In this study, we present a clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a-based diagnostic platform with a surface plasmon resonance-based fiber tip (CRISPR-SPR-FT) biosensor. The compact CRISPR-SPR-FT biosensor, with a 125 μm diameter, offers high stability and portability, enabling exceptional specificity for mpox diagnosis and precise identification of samples with a fatal mutation site (L108F) in the F8L gene. The CRISPR-SPR-FT system can analyze viral double-stranded DNA from mpox virus without amplification in under 1.5 h with a limit of detection below 5 aM in plasmids and about 59.5 copies/μL when in pseudovirus-spiked blood samples. Our CRISPR-SPR-FT biosensor thus offers fast, sensitive, portable, and accurate target nucleic acid sequence detection.

U-Grooved Selectively Coated and Highly Sensitive PCF-SPR Sensor for Broad Range Analyte RI Detection

Point-of-care (POC) diagnostic medical devices require simple but sensitive and inclusive detection capabilities. This study develops a unique photonic crystal fiber-based surface plasmon resonance (PCF-SPR) sensor that uses a u-grooved selective coating for extremely sensitive remote and biosensing applications. Scale-down (SCD) air holes control the path that incoming light takes through the sensor in order to activate the free electrons that are present there. To reduce outward radiation, perfectly matched layers (PML) of the absorbing boundary are integrated in addition to optimizing the structural geometry and material thickness. The Finite Element Method (FEM) is employed to quantitatively tune the properties of light directing and sensitivity of the proposed sensor. The proposed sensor has the maximum amplitude sensitivity (AS) of 1189 RIU <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , the highest wavelength sensitivity (WS) of 12,500 nm/(RIU), and an outstanding resolution of 8.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> RIU. The constructed model covers a large refractive index (RI) range of unknown samples, ranging from 1.29 to 1.40. This range allows this sensor to cover the detection of a wide range of bio-analytics, including viruses, cancer cells, carbohydrates, proteins, and DNA/RNA etc. We strongly believe that the suggested sensor will play an extremely useful role in the detection of POC bio-sample detection.

Fiber-Based Surface Plasmon Resonance Biosensor for Leptospira DNA Detection

Fiber-based surface plasmon resonance (SPR) sensors are the ideal configuration for rapid and label-free biomolecule detection. Gold-coated tapered optical fiber was used to excite the SPR mode that propagates at the metal–dielectric interface. By forming self-assembled monolayers (SAMs) of active chemical functional groups, the deoxyribonucleic acid (DNA) probe targeting the secY gene of Leptospira was immobilized onto the sensor surface. Red shifts in the SPR wavelengths were observed at different concentrations of leptospiral DNA target against the immobilized DNA probe due to the ability of plasmonic interaction to sensitively detect the binding of biomolecules on the sensor area. The developed sensor showed satisfactory linear responses at two target concentration ranges; low (1.0 fM to 1.0 pM) and high (0.1 nM to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0~\mu \text{M}$ </tex-math></inline-formula> ), with the highest sensitivity of 1.22 nm per log M. The negative control test also revealed high sensor specificity toward the complementary DNA strand. This sensor will represent a significant step toward laboratory-free diagnosis of leptospirosis.

High-sensitivity biconical optical fiber SPR salinity sensor with a compact size by fiber grinding technique

For seawater salinity measurement, a high-sensitivity, ultra-compact, and corrosion-resistant biconical optical fiber surface plasmon resonance (SPR) sensor deposited with a 40 nm thick gold film based on fiber grinding technique was fabricated and demonstrated in this article. The ultra-compact biconical sensing structure with different grinding angles were fabricated by applying the optical fiber grinding machine, and the length of the sensing region was only hundreds of microns. The experimental results indicated that when the grinding angle was 14°, the sensor showed the highest sensitivity: a high refractive index sensitivity of 3965 nm/RIU and a high salinity sensitivity of 0.6898 nm/‰. Meanwhile, this biconical sensor had acceptable repeatability and stability. Therefore, this article demonstrated the feasibility of the biconical structure to improve the sensitivity of fiber-based SPR sensors, and provided a novel and practical solution for seawater salinity measurement.

A novel plasmonic sensor using solid core D-shaped negative curvature optical fiber with AU–TiO2 layer

Recently, unique structure fiber enacts a significant role in sensing applications. A novel D-shaped negative curvature fiber based surface plasmon resonance (SPR) sensor is proposed. The design consists of negative curvature solid core fiber surrounded by a cladding composed of double-layer adjoined airholes. An outside layer of the cladding contains semi-circular airholes, and the interior layer has small circular air holes to overwhelm the higher-order modes. The external sensing approach detects changes in the refractive index between 1.33 and 1.37. Employing gold as a plasmonic material, SPR is developed on top of the photonic crystal fiber (PCF). Between the gold layer and the PCF, a small layer of titanium dioxide is placed for binding the plasmonic material to the fiber. And it acts as an adhesive layer. The finite element method is used to perform numerical analyses. After improving the structural parameters, an enhanced sensitivity of 26 000 nm RIU−1 is achieved. Because of its enhanced sensitivity, this sensor is used in a bio-medical application to detect and prevent diseases in the early stage.

Photonic crystal fiber-based SPR sensor for broad range of refractive index sensing applications

Until now, the use of photonic crystal fiber (PCF) based sensors has been limited. Environmental monitoring, the chemical industry, the food industry, and biomedicine are merely some of the fields. In this work, a surface plasmon resonance (SPR) sensor based on PCF is designed and simulated for a wide range of refractive index (RI) sensing applications with high sensitivity. The outer surface of PCF is coated with gold (Au), and a thin coating of titanium dioxide serves as an adhesive between the Au and silica. Using the SPR interaction between the core mode and Surface Plasmon Polariton mode of the proposed sensor, the RI of the analyte is detected. The simulated sensor has shown wavelength sensitivity of 10000 nm/RIU, sensor resolution of 2 × 10−5 RIU and amplitude sensitivity of 1115 RIU−1. Its operating wavelength ranges from 0.5 µm to 1.35 µm and it can detect the RI ranges from 1.35 to 1.40. The proposed sensor is exceptional for biochemical sensing, medical testing, and environmental monitoring due to its extensive range of RI detection and sensing.

A Fiber-Based SPR Aptasensor for the In Vitro Detection of Inflammation Biomarkers.

It is widely accepted that the abnormal concentrations of different inflammation biomarkers can be used for the early diagnosis of cardiovascular disease (CVD). Currently, many reported strategies, which require extra report tags or bulky detection equipment, are not portable enough for onsite inflammation biomarker detection. In this work, a fiber-based surface plasmon resonance (SPR) biosensor decorated with DNA aptamers, which were specific to two typical inflammation biomarkers, C-reactive protein (CRP) and cardiac troponin I (cTn-I), was developed. By optimizing the surface concentration of the DNA aptamer, the proposed sensor could achieve a limit of detection (LOD) of 1.7 nM (0.204 μg/mL) and 2.5 nM (57.5 ng/mL) to CRP and cTn-I, respectively. Additionally, this biosensor could also be used to detect other biomarkers by immobilizing corresponding specific DNA aptamers. Integrated with a miniaturized spectral analysis device, the proposed sensor could be applied for constructing a portable instrument to provide the point of care testing (POCT) for CVD patients.

Mechanically hot-pressed flattened plastic optical fiber-based SPR sensor and its RI sensing

This paper presents a surface plasmon resonance (SPR) sensor based on a flattened plastic optical fiber (POF) for refractive index (RI) sensing. The flattened POF is fabricated by mechanical hot pressing. Afterwards, a thin film of Ag and Au is first deposited on one side of the flat surface to excite the SPR effect. The results show that the flattened POF-based SPR probe coated with the Au film has a sharper SPR peak and a narrower peak width than the probe coated with Ag film. To improve the SPR effect, two flat surfaces of the flattened POF are coated with metal film (Ag and Au). It was found that the sensor showed better RI sensing performance compared to the sensor with only one flat surface coated with metal film. For the flattened POF with two flat surfaces coated with Ag film, achieving the highest RI sensitivity of 2507 nm/RIU in the RI range of 1.33–1.39. The proposed sensor is a low-cost solution for RI measurement with potential applications in the medical and biochemical fields.