Optic Surface Plasmon Resonance Sensor Research Articles

Dual-tapered optical fiber structure-based localized surface plasmon resonance sensor for cholesterol detection in human body

Cholesterol plays an important role in biological systems, and the quantity of cholesterol in the human body serves as a diagnostic marker for a range of disorders. This article presents a localized surface plasmon resonance (LSPR) sensor based on dual-tapered optical fiber (DTOF) that can detect cholesterol levels in the human body. To stimulate the LSPR effect and increase the sensitivity of the sensing probe, gold nanoparticles were fixed on the DTOF’s surface. In this study, the reaction between cholesterol and cholesterol oxidase altered the refractive index near the sensing probe, and the related spectrum was obtained. In addition, the sensor’s performance, including linear range, repeatability, reusability, stability, and selectivity, was examined. The experimental results indicate that the proposed DTOF-based LSPR sensor is capable of reliably measuring cholesterol levels and has promising biomedical applications.

Simultaneous measurement of refractive index and temperature based on a side-polish and V-groove plastic optical fiber SPR sensor.

A simple plastic optical fiber (POF) based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. The sensor consists of a series of V-grooves along the POF and a side-polish structure at the other side of the fiber. The V-groove structure can alter the SPR excitation angle and act as a mode filter, effectively enhancing the SPR effect and narrowing the SPR wavelength width. After coating a layer of thermosensitive material-polydimethylsiloxane (PDMS) film on half part of the fiber probe, a dual-parameter sensor probe is obtained for RI and temperature measurement. Experimental results show the RI sensitivity of the prepared probe can reach 1546 nm/RIU in the RI range of 1.335-1.37 RIU and the temperature sensitivity is -0.83 nm/°C in the temperature range of 20-80°C. The sensor is simple in structure and low cost, and has potential applications in the biochemical sensing fields.

Sensitivity enhancement of a wavelength interrogation-based optical fiber surface plasmon resonance sensor for hemoglobin concentration using barium titanate

In this paper, the performances of a wavelength interrogation-based optical fiber surface plasmon resonance sensor for hemoglobin (Hb) concentration is investigated by theoretical simulation. The proposed configuration incorporates optical fiber, 70 nm silver, 18 nm barium titanate (BaTiO3), and 2 nm zinc oxide. Simulation results show the sensor exhibits refractive index sensitivity of 4023 nm/RIU and concentration sensitivity of 10.0873 nm/(g·dL), along with Hb concentration varying from 0 to 14 g/dL. This paper especially focuses on the influence of BaTiO3 on the performances of the proposed sensor with light wavelength ranging from 350 to 1000 nm. Comparison analysis indicates sandwiching 18 nm BaTiO3 between sensing layers not only enhances the concentration sensitivity by 30.14% but also decreases the nonlinear error of the sensor from 0.68% to 0.63%. For a wavelength accuracy of 0.1 nm, the proposed sensor can provide a resolution of 0.0099 g/dL for Hb concentration detection.

Simultaneous Measurement of Ultraviolet Irradiance and Temperature by Employing Optical Fiber SPR Sensor With Ag/ZnO/PDMS Coating

It is a challenging and valuable work to design and manufacture temperature-compensated all-fiber ultraviolet (UV) sensor. In this article, we creatively use a simple and compact optical fiber sensor based on surface plasmon resonance (SPR) for simultaneous detection of UV and ambient temperature. Different coatings [Ag/polydimethylsiloxane (PDMS) and Ag/ZnO/PDMS] are used to split a length of no-core optical fiber (NCF) into two sensing regions, which generates a transmission spectrum with two distinct SPR dips. The proposed sensor achieves a temperature sensitivity of −2.542 nm/°C in the 15 °C–35 °C range and a UV sensitivity of −0.605 nm/(mW/cm2) in the range of 0–17.20 mW/cm2. The matrix established by the wavelength shift of two dips can demodulate UV and temperature changes, and provide temperature compensation for UV detection. In addition, even in surroundings of complex and changeable UV intensity and ambient temperature, the sensor shows excellent stability and repeatability, as well as great potential in UV sensing, providing a reference for the development of multiparameter optical fiber sensors.

A Near-Infrared Plasmonic Sensor Based on Wedge Fiber-Optic for Ultra-Sensitive Hg Detection

The growing number of serious diseases caused by ever-increasing heavy metal ions pollution have necessitated the use of ion sensors in healthcare and environment monitoring systems. Even with low concentrations heavy metal ions can cause significant harm, so ultra-sensitive on-site and label-free monitoring of heavy metal ions is of great importance. In this work, a simple, portable and high sensitivity optical fiber surface plasmon resonance (SPR) sensor is demonstrated for the detection of Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . On the basis of the investigation of the effects of different incident angles, the optical fiber sensor adopts wedged tip probe with a 75° incident angle. The plasmonic sensor exhibits a superior refractive index bulk sensitivity of up to 13830 nm/RIU in near-infrared band, which is a further step in ultrasensitive sensing detection, compared with the traditional optical fiber SPR sensors. In addition, we validate the optical fiber sensor's performance for Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> sensing. By self-assembling monolayer of 1,6-Hexanedithiol (HDT) on the sensing surface, the Au-coated fiber-optic probe is modified to capture Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . The lowest detection limit is found to be 0.324 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{ug}/\mathbf{mL}$</tex-math></inline-formula> for the near-infrared band and the sensitivity can reach up to 0.22 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$({\mathbf{ug}/\mathbf{mL}})$</tex-math></inline-formula> . The experimental results show the excellent promise for our sensor in applications of environmental monitoring due to high sensitivity, selectivity and low-cost.

Wedged Fiber Optic Surface Plasmon Resonance Sensor for High-Sensitivity Refractive Index and Temperature Measurements.

Here, we experimentally demonstrate a wedged fiber optic surface plasmon resonance (SPR) sensor enabling high-sensitivity temperature detection. The sensing probe has a geometry with two asymmetrical bevels, with one inclined surface coated with an optically thin film supporting propagating plasmons and the other coated with a reflecting metal film. The angle of incident light can be readily tuned through modifying the beveled angles of the fiber tip, which has a remarkable impact on the refractive index sensitivity of SPR sensors. As a result, we measure a high refractive index sensitivity as large as 8161 nm/RIU in a wide refractive index range of 1.333-1.404 for the optimized sensor. Furthermore, we carry out a temperature-sensitivity measurement by packaging the SPR probe into a capillary filled with n-butanol. This showed a temperature sensitivity reaching up to -3.35 nm/°C in a wide temperature range of 20 °C-100 °C. These experimental results are well in agreement with those obtained from simulations, thus suggesting that our work may be of significance in designing reflective fiber optic SPR sensing probes with modified geometries.

A Dual-Parameter Optical Fiber SPR Sensor for Simultaneous Measurement of Glucose and Cholesterol Concentrations

A surface plasmon resonance (SPR) dual-parameter sensor is designed and fabricated. It was electroless plated with silver on the surface of the core of the plastic-clad optical fiber and a gold film was plated near the end face side to produce the double SPR resonance valleys. 4-mercaptophenylboronic acid (4-MPBA) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -cyclodextrin ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -CD) were coated separately on the surface of the silver and gold films. 4-MPBA can selectively recognize the structures of cis-vicinal diols, and thus can capture glucose that contains such structures. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -CD is a class of cyclic oligosaccharides whose unique hydrophilic outer surface and lipophilic central cavity help facilitate the formation of inclusion complexes with cholesterol through multiple interactions. The sensor can detect 0–4 mM glucose and 0–500 nM cholesterol, and it has a linear response in the concentration range of 0–0.1 mM glucose and 0–15 nM cholesterol. The sensitivity of glucose and cholesterol concentration of the sensor is 89.6 and 0.994 nm/nM, respectively. The detection limits for quantifying glucose and cholesterol are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.12~\mu \text{M}$ </tex-math></inline-formula> and 0.1 nM, respectively. The experimental results also show that the sensor has good selectivity and stability. The proposed technique can be further applied in medicine, environment, and biology monitoring.

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.

Highly reproducible fiber optic surface plasmon resonance biosensors modified by CS2 for disposable immunoassays

To achieve fiber optic surface plasmon resonance (SPR) biosensors for disposable immunoassays, the following activities are required: first, to manufacture highly consistent fiber optic SPR sensors; second, to develop highly reproducible and reliable surface modification methods for the sensors; third, to establish methods of analysis and evaluation to determine the capability and reliability of biomolecular detection. In this work, we prepared microprobe-type fiber optic SPR sensors and selected highly consistent sensors according to the Pearson correlation coefficient (PCC) model. To obtain reliable surface modification, carbon disulfide (CS2) was introduced as a crosslinker to modify anti-human IgG on the surface of fiber optic SPR biosensors for the first time. After systematic improvement and optimization, the CS2-based biosensors obtained a higher human IgG sensitivity and lower human IgG detection limit than conventional (11-MUA)-based biosensors. The PCC model was employed to evaluate the consistency of the surface-functionalized biosensors, and experimental results showed that the CS2-based biosensors exhibited reliable consistency, while the (11-MUA)-based biosensors did not. Finally, the proposed CS2-based biosensors have high selectivity and work well in serum. The surface modification method and reliable and consistency evaluation model for the sensors reported in this paper can contribute to the development of disposable fiber optic SPR biosensors.

High-Sensitivity Triple-Channel Optical Fiber Surface Plasmon Resonance Sensor

Optical fiber surface plasmon resonance (SPR) sensors are widely used for refractive index (RI) sensing, thanks to their high sensitivity. However, with the increasing demand for multiple analytes detection and sensor integration, a traditional single-channel optical fiber SPR sensor is outdated. We propose and demonstrate a novel triple-channel optical fiber SPR sensor with high sensitivity. The sensor is fabricated with side-polished single-mode fiber (SMF), where the sensing film consists of a layer of gold nanofilm and a layer of TiO2 nanofilm. The resonance wavelength range of the SPR sensing zone can be adjusted significantly by changing the TiO2 nanofilm thickness. Experimentally, by cascading three sensing zones whose TiO2 nanofilm thicknesses are 10, 30, and 60 nm, respectively, a triple-channel SPR sensor is realized. The average sensitivities of three sensing channels reach up to 2637.8, 3962.2, and 6097.3 nm/RIU in the RI range of 1.333–1.370 RIU, which is superior to most current multichannel SPR sensors. Besides, three sensing channels are independent without crosstalk. The proposed triple-channel SPR sensor has great potential in biological and chemical sensing fields, especially in multiple analytes detection applications.

Multi-channel Optical Fiber Surface Plasmon Resonance Sensor with Narrow FWHM, High Figure of Merit, and Wide Detection Range

Multi-channel Optical Fiber Surface Plasmon Resonance Sensor with Narrow FWHM, High Figure of Merit, and Wide Detection Range

Surface plasmon resonance sensor using a polarization-maintaining fiber on a hetero-core optical fiber structure with gold thin film.

This study experimentally demonstrated the effects of two polarization-maintaining fibers (PMFs) as a sensing region instead of conventional single-mode fiber (SMF) using Au-coated hetero-core optical fiber surface plasmon resonance (SPR) sensor. We experimentally observed that the SPR resonant wavelength is shifted toward longer wavelength with refractive index (RI) increasing from 1.332 to 1.396. A PMF sensor exhibits the broad SPR spectra, resulting in a higher sensitivity with a 1.5-fold change in the light intensity at 850 nm relative to RI, compared with the SMF case. Discussions most likely responsible for this effect are given by the lower angular distribution peak in the hetero-core region of PMFs.

Chlorophyll Detection by Localized Surface Plasmon Resonance Using Functionalized Carbon Quantum Dots Triangle Ag Nanoparticles.

An optical sensor-based localized surface plasmon resonance (LSPR) sensor was demonstrated for sensitive and selective chlorophyll detection through the integration of amino-functionalized carbon quantum dots (NCQD) and triangle silver nanoparticles (AgNPs). The additions of amino groups to the CQD enhance the detection of chlorophyll through electrostatic interactions. AgNPs-NCQD composite was fabricated on the surface of the silanized glass slide using the self-assembly technique. The experimental results showed that the AgNPs-NCQD film-based LSPR sensor detects better than AgNPs and AgNPs-CQD films with a good correlation coefficient (R2 = 0.9835). AgNPs-NCQD showed a high sensitivity response of 2.23 nm ppm−1. The detection and quantification limits of AgNPs-NCQD are 1.03 ppm and 3.40 ppm, respectively, in the range of 0.05 to 6 ppm. Throughout this study, no significant interference was observed among the other ionic species (NO2−, PO4−, NH4+, and Fe3+). This study demonstrates the applicability of the proposed sensor (AgNPs-NCQD) as a sensing material for chlorophyll detection in oceans.

Identification of milk quality and adulteration by surface-enhanced infrared absorption spectroscopy coupled to artificial neural networks using citrate-capped silver nanoislands

Milk is one of the most important multicomponent superfoods owing to its rich macronutrient composition. It requires quality control at all the production stages from the farm to the finished products. A localized surface plasmon resonance optical sensor based on a citrate-capped silver nanoparticle (Cit-AgNP)–coated glass substrate was developed. The fabrication of such sensors involved a single-step synthesis of Cit-AgNPs followed by surface modification of glass slides to be coated with the nanoparticles. The scanning electron microscope micrographs demonstrated that the nanoparticles formed monolayer islands on glass slides. The developed surface-enhanced infrared absorption spectroscopy (SEIRA) sensor was coupled to artificial neural networking (ANN) for the qualitative differentiation between cow, camel, goat, buffalo, and infants’ formula powdered milk types. Moreover, it can be used for the quantitative determination of the main milk components such as fat, casein, urea, and lactose in each milk type. The qualitative results showed that the obtained FTIR spectra of cow and buffalo milk have high similarity, whereas camel milk resembled infant formula powdered milk. The most difference in FTIR characteristics was evidenced in the case of goat milk. The developed sensor adds several advantages over the traditional techniques of milk analysis using MilkoScan™ such as less generated waste, elimination of pre-treatment steps, minimal sample volume, low operation time, and on-site analysis.Graphical abstract

Ge[formula omitted]Sb[formula omitted]Te[formula omitted]-coated fiber optic SPR sensor: Improving sensitivity

This paper proposes and demonstrates a fiber optic surface plasmon resonance (SPR) sensor based on Au–Ge2 Sb2Te5 (GST). The GST is deposited on the Au film, which increases the dielectric constant of the metal layer due to the high refractive index (RI) of GST. Therefore, compared with conventional Au SPR sensor, the resonance wavelength of the Au–GST SPR sensor red-shifts, and the sensitivity is improved. When environmental RI varies in the range of 1.333∼1.403, the experimental results show that the sensor performs the best when the thicknesses of Au film is 50 nm and the GST layer’s thickness is 25 nm. The proposed sensor’s sensitivity is 5210 nm/RIU (refractive index unit), which is much higher than that of the conventional Au-based SPR sensor (2418 nm/RIU). The sensor achieves relatively high sensitivity based on a very simple structure, and it has potential applications in biological and biochemical such as DNA hybridization, cancer screenings, environmental temperature and humidity detection, and chemical analysis.

Effect of oxide layer on the performance of silver based fiber optic surface plasmon resonance sensor

Effect of oxide layer on the performance of silver based fiber optic surface plasmon resonance sensor

Theoretical study of distance-dependent optical fiber SPR sensor based on MoS2 nanosheets

Sandwich assay employing gold nanoparticles and DNA is a common signal amplification strategy designed for surface plasmon resonance sensor. To further improve the sensitivity employing sandwich assay, sandwich-structured optical fiber surface plasmon resonance sensors based on AuNPs and MoS2 nanosheets has been theoretically studied. Au film deposited on fiber core is the bottom nanomaterial of sandwich structure while AuNPs and MoS2 nanosheets are optional used as top nanomaterials. Top and bottom nanomaterials are separated by double stranded DNA, which allows solvent to perform as a spacer. The thickness of spacer is able to be tuned by the number of base pairs of double stranded DNA. Spacer thickness and nanomaterials play important roles to regulate the performance of optical fiber surface plasmon resonance sensor. The refractive index sensitivity has been found to be enhanced by the presence of MoS2 nanosheets compared to AuNPs. Large spacer thickness supported by long double stranded DNA further improves the performance of sensor. This study yields new insight into the structural design of optical fiber surface plasmon resonance sensor enhanced by sandwich structure and will open exciting avenues to apply sandwich-like assay for biosensing.

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.

A method for the controllable fabrication of optical fiber-based localized surface plasmon resonance sensors

Optical fiber-based Localized Surface Plasmon Resonance (OF-LSPR) biosensors have emerged as an ultra-sensitive miniaturized tool for a great variety of applications. Their fabrication by the chemical immobilization of gold nanoparticles (AuNPs) on the optic fiber end face is a simple and versatile method. However, it can render poor reproducibility given the number of parameters that influence the binding of the AuNPs. In order to develop a method to obtain OF-LSPR sensors with high reproducibility, we studied the effect that factors such as temperature, AuNPs concentration, fiber core size and time of immersion had on the number and aggregation of AuNPs on the surface of the fibers and their resonance signal. Our method consisted in controlling the deposition of a determined AuNPs density on the tip of the fiber by measuring its LSPR signal (or plasmonic signal, Sp) in real-time. Sensors created thus were used to measure changes in the refractive index of their surroundings and the results showed that, as the number of AuNPs on the probes increased, the changes in the Sp maximum values were ever lower but the wavelength shifts were higher. These results highlighted the relevance of controlling the relationship between the sensor composition and its performance.

Multichannel Fiber Optic SPR Sensors: Realization Methods, Application Status, and Future Prospects

AbstractFiber optic sensors based on surface plasmon resonance (SPR) have demonstrated outstanding performance in biomedical, environmental monitoring, public safety, and other aspects, which provide powerful platforms for qualitative detection and quantitative analysis of molecular interactions. Among them, multichannel fiber optic SPR sensor has become a core tool in parallel detection scenarios due to the superiorities of compensating for nonspecific binding and environmental fluctuations and implementing multianalyte determination. The realization methods of multichannel sensing revolve around fiber microstructures, enhancement by materials, and hybrid fiber. The applications of multichannel fiber optic SPR sensors are demonstrated in sensing of liquid refractive index (RI), RI and temperature, biochemical molecules, and physical parameters. This review thoroughly analyzes and compares the structure, excitation effect, sensing performance, and the advantages and disadvantages of each type of multichannel fiber optic SPR sensor. Even though there are still some challenges, such as insufficient sensing channels and difficulty in fabrication, in their advancement, efforts in multidiscipline including developing high‐performance sensitive films and innovating micro–nano fabrication processes will overcome these bottlenecks. Lastly, the future development directions of multichannel fiber optic SPR sensors from principle, structure, and material aspects are discussed.