Localized Surface Plasmon Resonance Fiber Research Articles

Fiber Optic based Localized SPR for Nutrients Detection in Modern Agricultural Applications

Detection of nutrients in the hydroponics system, particularly nitrogen, phosphorus, and potassium (NPK) are critical to ensure the good production of crops. Currently, nutrients are analyzed using spectroscopy and electrochemical techniques, which are tedious and sophisticated. This study was conducted to develop a localized surface plasmon resonance (LSPR) fiber optic sensor technique to measure how much content of these nutrients should be added in the soil to increase crop fertility. The main objectives of this study are to study the LSPR fiber sensor technology on NPK in hydroponic systems, to create a fiber optic sensor technique for measuring NPK in hydroponic systems, and finally to characterize the performance of fiber optic sensors for measuring NPK in hydroponic systems. The utilization of the sensing materials, chitosan in this work is to improve the sensitivity feature of the sensor. Chitosan is coated on the surface of the tapered optical fiber prior to the LSPR NPK detection. The results of the absorption spectra will be visible at the end of the experiment where the obtained data are analyzed using SpectraSuite software. The results show that a good linearity was obtained when used AgNP/chitosan as the sensing material with the sensitivity of 0.041 nm ppm-1 in comparison to that of AgNP with the sensitivity of 0.039 nm ppm-1. A better limit of detection (LOD) and limit of quantification (LOQ) was also observed for AgNP/chitosan which are 35.61 ppm and 107.91 ppm, respectively. Meanwhile, AgNP exhibits LOD and LOQ of 106.16 ppm and 494.43 ppm, respectively. It is expected that this work will be a good contributor to the United Nations Sustainable Development Goals (UN SDG), No. 2: Zero Hunger.

Quantifiable Effect of Interparticle Plasmonic Coupling on Sensitivity and Tuning Range for Wavelength-Mode LSPR Fiber Sensor Fabricated by Simple Immobilization Method

Herein a gold nanosphere (AuNS)-coated wavelength-mode localized surface plasmon resonance (LSPR) fiber sensor was fabricated by a simple and time-saving electrostatic self-assembly method using poly(allylamine hydrochloride). Based on the localized enhanced coupling effect between AuNSs, the LSPR spectrums of the AuNS monolayer with good dispersity and high density exhibited a favourable capability for refractive index (RI) measurement. Based on the results obtained from the optimization for AuNS distribution, sensing length, and RI range, the best RI sensitivity of the fiber modified by 100 nm AuNS reached up to about 2975 nm/RIU, with the surrounding RI range from 1.3322 to 1.3664. Using an 80 nm AuNS-modified fiber sensor, the RI sensitivity of 3953 nm/RIU was achieved, with the RI range increased from 1.3744 to 1.3911. The effect of sensing length to RI sensitivity was proven to be negligible. Furthermore, the linear relationship between the RI sensitivity and plasma resonance frequency of the bulk metal, which was dependent on the interparticle plasmon coupling effect, was quantified. Additionally, the resonance peak was tuned from 539.18 nm to 820.48 nm by different sizes of AuNSs-coated fiber sensors at a RI of 1.3322, which means the spectrum was extended from VIS to NIR. It has enormous potential in hypersensitive biochemistry detection at VIS and NIR ranges.

Gold Nanoparticles Modified a Multimode Clad-Free Fiber for Ultrasensitive Detection of Bovine Serum Albumin

Gold nanoparticles (Au NPs) were almost chosen as the first option for biological and biosensor applications due to their enhancement and their outstanding properties. The combining of optical fiber with localized surface plasmon resonance (LSPR) for forming a biosensor is widely used in diagnosis. In this work, we report a fiber optical biosensor based on LSPR of Au NPs for the detection of bovine serum albumin (BSA) protein. BSA was functionalized on Au NPs immobilized fiber optic sensing head (length of 1 cm) via methanesulfonic acid (MSA) by carboxylic binding. It is the binding between the analytes with the surface-modified Au NPs that caused refractive index changes in the sensing medium led to changes in optical power at the output of the sensor. The detection limit of the LSPR fiber biosensor was found to be 0.18 ng/mL for the BSA detection with the low coefficient of variation (CV) at under 1%. We have demonstrated the effectiveness of combining multimode fiber with Au NPs to generate the biosensor as the label-free sensor that can be a feasible tool for highly sensitive, rapid response time, stable, and miniaturized point-of-care analytical systems.

Graphene-Oxide Coated Ag-Island-Based Inline LSPR Fiber Sensor

Graphene Oxide (GO) coated silver (Ag) island system based on localized surface plasmon resonance (LSPR) phenomenon have been developed using optical fiber as a sensing probe. The Ag-island is used to excite LSPR field which is responsible for the analyte sensing through a shift in resonance wavelength. The deposition of Ag-islands is confirmed from UV-VIS spectra and Field Emission Scanning Electron Micro-graph (FESEM). The usage of GO helps to protect Ag-island from oxidation along with opening a new window for bio-sensing due to its structural compatibility with the bio-sensing system. We have experientially observed that the GO as a dielectric overlayer on Ag-island shows a refractive index sensitivity of 2217.04 nm/RIU with a resolution of $4.05 \times 10^{-4}$ RIU.

A wavelength-modulated localized surface plasmon resonance (LSPR) optical fiber sensor for sensitive detection of mercury(II) ion by gold nanoparticles-DNA conjugates

The study presented herein investigated an easy preparation, high performance, wavelength-modulated LSPR optical fiber chemosensor coated by gold nanospheres(AuNS) for Hg2+ detection based on thymine-Hg2+-thymine base pair mismatches and the coupled plasmonic resonance effect.Utilizing electrostatic self-assembly method, the high density and dispersivity monolayer AuNS coated LSPR fiber sensor had the near field refractive index sensitivity up to 2016 nm/RIU. The single-strand probe DNA served as a binding element for free AuNS labelled-target DNA conjugates was attached to the monolayer AuNS by Au-S bond. In the present of Hg2+, the coupled plasmonic resonance band between monolayer AuNS and free AuNS was produced by thymine-Hg2+-thymine structure and leaded to red-shift of LSPR peak. Under the optimal conditions, the enlarged red-shift in peak of LSPR spectroscopy was linearly with the concentration of Hg2+ in the range from 1.0 × 10−9 to 5.0 × 10−8 M with the coefficient of 0.976. The limit of detection was 0.7 nM(S/N = 3). The specificity of the sensor was proved high by evaluating the response to other heavy metal ions. The proposed fiber sensor provided a label-free, miniature, low-cost approach for the Hg2+ detection and had potential in real environmental evaluations.

Highly sensitive, localized surface plasmon resonance fiber device for environmental sensing, based upon a structured bi-metal array of nano-wires.

We demonstrate a bi-metal coated (platinum and gold or silver), localized surface plasmon resonance fiber sensor with an index sensitivity exceeding 11,900 nm/RIU, yielding an index resolution of 2×10⁻⁵ in the aqueous index regime. This is one of the highest index sensitivities achieved with an optical fiber sensor. The coatings consist of arrays of bi-metal nano-wires (typically 36 nm in radius and 20 μm in length), supported by a silicon dioxide thin film on a thin substrate of germanium, the nano-wires being perpendicular to the longitudinal axis of the D-shaped fiber.

Novel and high-performance LSPR biochemical fiber sensor

To enhance further the performance of the current localized surface plasmon resonance (LSPR) biochemical fiber sensor, a novel design model for a short length, high resolution, and high sensitivity was developed in this study. Based on a cross-sectional view of the component, the proposed new LSPR biochemical fiber sensor comprises a single-mode fiber and two types of nano-metal gears. The difference between these two types of nano-metal gears is the angular displacement of a single pitch. In a cylindrical coordinate system, if the φ axis is considered a straight, the LSPR fiber sensor exhibits a clear tessellation array. The numerical simulation method that combines the finite element method (FEM) and eigenmode expansion method (EEM) was used to design and analyze the sensor. In addition, to increase the accuracy of the numerical simulation results, the proposed numerical simulation method included a perfectly matched layer (PML) and a perfectly reflecting boundary condition (PRB). After the design procedures had been performed, the LSPR biochemical fiber sensor designed in this study possesses the advantageous attributes of a short length (74.34779μm), high resolution (−110dB), and high sensitivity (93987nm/RIU). As far as I know, up to present it possesses the best resolution and sensitivity compared with the other LSPR sensors.

Nanometal ring-array LSPR fiber sensor based on the perfectly matched layer and perfectly reflecting boundary

To reduce the error between actual operations and numerical simulations, thereby enabling effective design parameters to be obtained during the sensor production process and increasing the precision of simulated results, we integrated theories relevant to the perfectly matched layer and perfectly reflecting boundary condition with the finite element method and eigenmode expansion method. In addition, the modified simulation method was used to design and research a high-performance nanometal ring-array localized surface plasmon resonance (LSPR) sensor, comprising single-mode fibers (SMFs) and nanometal ring arrays. The existence of LSPR waves is the primary reason that determines whether LSPR sensors exhibit high sensitivity; thus, we examined the ability of the sensor structure to trigger LSPR waves by using the electric field Er of the core mode HE11 on the optical fiber. After employing the relevant algorithms, the resulting images demonstrated the excitation of the LSPR. This nanometal ring-array LSPR fiber sensor is advantageous because of its short length (393.59788μm), high resolution (approximately −90dB), and high sensitivity (approximately 38,600nm/RIU).

High-Performance LSPR Fiber Sensor Based on Nanometal Rings

A novel localized surface plasmon resonance (LSPR) fiber sensor was proposed. This LSPR fiber sensor was primarily constructed by conducting etching of the cladding layer and core layer on a single-mode fiber, followed by plating of 1444 nanometal rings. Sensor design and relevant calculations were conducted using a semi-analytical simulation method, which integrated the exact mode solver for the cylindrical coordinate and eigenmode expansion method. It was examined that the current metallic patterns in the fiber sensor can trigger the LSPR by the electric field Er of the core mode HE11, and this is the main reason why this novel fiber sensor can obtain high performance. After performing algorithms, images showed evident excitation of the LSPR. The LSPR fiber sensor designed in this paper possesses excellent attributes of short length (185.173 μm), high resolution (approximately - 70 dB), and high sensitivity (approximately 34 257 nm/RIU).

High-performance localized surface plasmon resonance fiber sensor based on nano-metal-gear array

Utilizing the outstanding-sensitivity characteristic of localized surface plasmon resonance (LSPR), this study developed a new high-performance sensor design model. Based on a cross-sectional view of the component, the proposed new LSPR fiber sensor comprises a single-mode fiber (SMF), nano-metal rings, and nano-metal gears. The numerical simulation method that combines the finite element method (FEM) and eigenmode expansion method (EEM) was used to design and analyze the sensor. In addition, to increase the accuracy of the numerical simulation results, the proposed numerical simulation method included a perfectly matched layer (PML) and a perfectly reflecting boundary condition (PRB). In other words, the FEM and EEM numerical methods involve not only discrete guided modes and discrete LSPR modes in the simulation and design process, but also discrete radiation modes, that is, continuous radiation modes converted using PML and PRB. This study found that the current metallic patterns in the fiber sensor can trigger the LSPR by the electric field Er of the core mode HE11, which is the main reason the novel fiber sensor yields a high performance. After algorithms were performed, images showed evident excitation of the LSPR. The LSPR fiber sensor designed in this study possesses the advantageous attributes of a short length (77.01764μm), high resolution (approximately −80dB), and high sensitivity (approximately 45,062nm/RIU).

Dengue immunoassay with an LSPR fiber optic sensor

Dengue fever is a viral disease that affects millions of people worldwide. Specific tests for dengue are not usually performed due to high costs, complicated procedures and, in some cases, long time to yield a result. For widespread use of specific tests to be possible, fast, reliable and fairly simple methods are needed. In this paper, we present a new dengue diagnostic method for the acute phase of the infection. The method proposed uses an all-optical fiber sensor based on Localized Surface Plasmon Resonance (LSPR) and specular reflection from gold nanoparticles (AuNPs). Dengue anti-NS1 antibody was immobilized on AuNPs deposited on the endface of a standard multimode fiber (62.5 µm/125 µm). The sensor is able to detect NS1 antigen at different concentrations, with limit of quantification estimated to be 0.074 μg/ml = 1.54 nM. These results indicate that the sensor could potentially be used for dengue diagnosis in the acute phase of the infection.

Novel D-shape LSPR fiber sensor based on nano-metal strips

In this study, a novel D-shaped localized surface plasmon resonance (LSPR) fiber sensor was introduced. The construction of this sensor involved etching of a single-mode fiber on the cladding layer and core layer, followed by plating using nano-metal strips. The design and calculations of the entire sensor were based on a numerical simulation method combining the finite element method (FEM) and the eigenmode expansion method (EEM). By using graphical representations of the algorithm results, the excitation of the LSPR was clearly observed. The finished D-shaped LSPR fiber sensor possesses several excellent properties, including a short length (2494.4301 μm), high resolution (approximately 35 dB), and high sensitivity (approximately 20183.333 nm/RIU). In addition, compared with LPG-SPR fiber sensor, the framework provides three advantages, namely, a fabrication process that is compatible with semiconductor fabrication, as well as the low-temperature cross-talk and high-temperature stability of surface grating.

Fabrication of Localized Surface Plasmon Resonance Fiber Probes Using Ionic Self-Assembled Gold Nanoparticles

An nm-thickness composite gold thin film consisting of gold nanoparticles and polyelectrolytes is fabricated through ionic self-assembled multilayers (ISAM) technique and is deposited on end-faces of optical fibers to construct localized surface plasmon resonance (LSPR) fiber probes. We demonstrate that the LSPR spectrum induced by ISAM gold films can be fine-tuned through the ISAM procedure. We investigate variations of reflection spectra of the probe with respect to the layer-by-layer adsorption of ISAMs onto end-faces of fibers, and study the spectral variation mechanism. Finally, we demonstrated using this fiber probe to detect the biotin-streptavidin bioconjugate pair. ISAM adsorbed on optical fibers potentially provides a simple, fast, robust, and low-cost, platform for LSPR biosensing applications.