Utilizing Surface Plasmon Resonance Research Articles

Machine learning-enhanced surface plasmon resonance based photonic crystal fiber sensor

This study introduces what we believe to be a novel photonic crystal fiber sensor utilizing surface plasmon resonance (SPR), incorporating four gold nanowires to enhance sensing capabilities. The research employs machine learning, specifically artificial neural networks (ANN), to predict confinement loss and sensitivity, achieving high accuracy without needing the imaginary part of the effective refractive index. The machine learning technique is applied in three different scenarios, resulting in mean squared errors of 0.084, 0.002, and 0.003, highlighting the reliability of the ANN models in predicting sensor outputs. Additionally, the sensor demonstrates impressive wavelength sensitivities of 2000-18000 nm/RIU (nanometers per refractive index unit) for refractive indices of 1.31-1.4 within the 720-1280 nm wavelength range, and a notable maximum amplitude sensitivity of 889.89 RIU-1. This integration of SPR, photonic crystal fiber, and machine learning not only optimizes sensor performance but also offers an efficient methodology for prediction, showcasing the potential of machine learning in advancing optical sensor design.

Highly sensitive ZnO/Ag/BaTiO3/MoS2 hybrid structure-based surface plasmon biosensor for the detection of mycobacterium tuberculosis bacteria

This study presents a novel biosensor utilizing surface plasmon resonance (SPR) technology, comprising og zinc oxide (ZnO), silver (Ag), barium titanate (BaTiO3), and molybdenum disulfide (MoS2). The detection of mycobacterium tuberculosis bacteria was accomplished through the utilization of the hybrid structure. The transfer matrix method (TMM) and finite element method are employed to analyze the suggested surface plasmon resonance (SPR) structure. A comparative analysis has been conducted to evaluate the angular sensitivity between normal blood samples (NBS) and cells affected by tuberculosis (TB). The optimization of the performance of the surface plasmon resonance (SPR) structure involves adjusting the thickness of ZnO, Ag and BaTiO3 layer. The accurate measurement of the full width at half maximum (FWHM), detection accuracy (DA), quality factor and figure of merits (FOM) has also been conducted. The optimal angular sensitivity has been determined to be 10 nm for ZnO, 40 nm for Ag, 1.5 nm for BaTiO3, and one layer of MoS2 with a sensitivity of 525 deg./RIU. Additionally, this study compared the effects on sensitivity of two dimensional materials graphene, WS2 and MoS2. In contrast to the currently available biosensor utilizing surface plasmon resonance (SPR), the suggested structure exhibits higher angular sensitivity. Due to its improved sensitivity, the biosensor under consideration exhibits potential for detecting a wide range of biological analytes and organic compounds.

Utilizing surface plasmon resonance as a novel method for monitoring in-vitro P-glycoprotein efflux.

P-glycoprotein (Pgp) is known for its dichotomous roles as both a safeguarding efflux transporter against xenobiotics and as a catalyst for multidrug resistance. Given the susceptibility of numerous therapeutic compounds to Pgp-mediated resistance, compliance with Food and Drug Administration (FDA) guidelines mandates an in-depth in vitro transport assay during drug development. This study introduces an innovative transport assay that aligns with these regulatory imperatives but also addresses limitations in the currently established techniques. Using Pgp-reconstituted liposomes and employing surface plasmon resonance (SPR), this study developed a distinct method of measuring the relative transport rates of Pgp substrates in a controlled microenvironment. The Pgp substrates selected for this study-quinidine, methadone, and desipramine-resulted in transport ratios that corroborate with trends previously observed. To assess the kinetics of Pgp-mediated transport, the results were analyzed by fitting the data to both currently proposed Pgp substrate translocation models-the vacuum cleaner and flippase models. While the resulting kinetic analysis in this study lends support predominantly to the vacuum cleaner model, this study most notably developed a novel method of assessing Pgp-mediated transport rates and real-time kinetics using surface plasmon resonance.

Plasmonic Imaging of Spatiotemporal Electrochemical Bubble Evolution on Smooth Electrodes with Different Wettabilities

Although evolution dynamic investigation onto electrochemically generated bubbles on electrode surfaces is crucial for releasing “bubble blocking” effects, traditional “top view” or “side view” methods make spatiotemporal interfacial revolutions difficult to achieve, which are critical for a deeper understanding and better electrode design. In this study, a novel method utilizing surface plasmon resonance (SPR) is proposed to probe bubble interfacial dynamics. By monitoring reflectivity changes and utilizing differential imaging, real‐time fluctuations in the contact area can be accurately visualized. The investigation onto bubble growth events on both aerophilic and aerophobic surfaces reveals that they occur in very distinct patterns. Due to the “necking effect”, the reflectivity of aerophilic electrodes rushed to its highest value and remained or gradually decreased, followed by a sudden drop due to bubble disengagement. While the aerophobic ones increased to the bubble release threshold after a downward parabola function, then dropped abruptly without plateau. This in situ imaging technique provides a feasible tool for bubble disengagement dynamic investigations on electrode surface. Based on current observations, it is revealed that changing the wettability of electrodes causes substantial changes in bubble evolution dynamics.

A high magnetic field sensitivity PCF‐SPR sensor working in the near‐infrared wavelength band

AbstractA novel form of photonic crystal fiber (PCF) magnetic field sensor, utilizing surface plasmon resonance, has been developed and investigated. By depositing a layer of gold onto the interior surface of the left‐sided air hole and introducing magnetic fluid into the aperture to detect magnetic field changes, the plasma resonance effect was ingeniously combined with a dual‐core PCF to achieve magnetic field measurement. The displacement of the loss peak in the output spectrum was observed to gain insights into the magnetic field changes. By means of modulations in the thickness of the gold film, and the spacing and size of the air holes, the optimal parameters for the sensor were obtained. The optimized sensor exhibited a maximum magnetic field sensitivity of up to 6.23 nm/Oe, and the magnetic field detection resolution was approximately 10 μT, enabling precise detection of weak magnetic fields. This fiber sensor boasts a simple structure, ease of production, high sensitivity, and robust environmental adaptability, making it an attractive option for implementation.

Research on optimization of magnetic field sensing characteristics of PCF sensor based on SPR.

A photonic crystal fiber utilizing surface plasmon resonance (PCF-SPR) sensor based on refractive index (RI) control of magnetic fluid (MF) is designed. The air holes of the sensor are arranged in a hexagonal shape, and the optical field transmission channels on both sides of the central air hole can effectively confine the energy of the optical field. We use MF as the sensing medium, and coat the inner wall of the central air hole with gold. It can effectively stimulate the SPR effect to achieve the purpose of magneto-refractive modulation. We study the sensing characteristics of the proposed sensor by finite element analysis. The results show that the highest refractive index sensitivity reaches 19520 nm/RIU in the RI range of 1.42-1.435 and the maximum figure of merit (FOM) is 374.3 RIU-1. In addition, the magnetic field and the temperature response characteristics of the designed sensor are also investigated. In the magnetic field range of 50-130 Oe, the magnetic field sensitivity is 590 pm/Oe. In the temperature range of 24.3-144.3 °C, the temperature sensitivity is only -29.7 pm/℃. The proposed sensor has significant advantages such as stable structure, high sensitivity, easy integration, resistance to electromagnetic interference and can be used for weak magnetic magnitude detection. It has wide application prospects in industrial production, military, and medical equipment.

Design and analysis of surface plasmon resonance based photonic crystal fiber sensor employing gold nanowires

A simple design of photonic crystal fiber (PCF) sensor which utilizes surface plasmon resonance (SPR) for refractive index detection is inspected to achieve high sensitivity. The offered sensor comprises of air holes in square lattice arrangement where two gold nanowires as a plasmonic material are located at the surface. Size-dependent plasmonic features of nanowires facilitates the coupling of SPR and fundamental core modes which leads to enhancement of sensor performance. With the propose of achieving the best result, the geometrical structure including the size of air holes and their arrangement in the PCF and also the size of nanowires are examined, in this work. Sensing performance of the proposed sensor is evaluated by finite element method using Comsol Multiphysics software. In y-polarization mode, the maximum wavelength and amplitude sensitivities of 50000 (nm/RIU) and 672.2 1/RIU have been obtained. The corresponding maximum values of figure of merit and resolution are 250 (1/RIU) and 2×10−6(RIU), respectively. This sensor includes remarkable prospect in chemical and biomedical detection because of its high sensitivity and low fabrication complexity. For example, the sensor performance is investigated for the cervical cancer cell detection and high sensitivity as 40000 (nm/RIU) is obtained.

Highly sensitive externally metal coated plasmonic refractive index sensor based on photonic crystal fiber

A simple configuration of a photonic crystal fiber (PCF) with dual-core is proposed that utilizes surface plasmon resonance (SPR) to work as a refractive index (RI) sensor. The PCF structure is asymmetric; thus, the PCF shows birefringence. A plasmonic metal layer of gold is placed over the fiber sensor to form an analyte channel externally. The sensing range and sensitivity are extended by investigating the best field path that moves from the core throughout the cladding towards the plasmonic layer. The best field path increases the analyte sensing range from 1.33 to 1.43, where the analyte flows through the external channel. The light-guiding properties of the sensor are explored by the finite element method. The optical properties of the sensor are numerically analyzed by the wavelength and amplitude integration methods. The numerical analysis found that the maximum wavelength sensitivity is 44,000 nm/RIU and 50,000 nm/RIU for x- and y-polarization, respectively. Additionally, the maximum amplitude sensitivity for x- and y- polarization is 2244 RIU-1 and 1605 RIU-1, respectively. The highest figure of merit (FOM) of the sensor is 721 and 769 for the x- and y- polarization, respectively. We also investigate the fabrication tolerance of the PCF detector. The sensor can be used for unknown biological or biochemical samples finding because of its wide sensing range with high sensitivity.

In-situ and simultaneous evaluation of optical absorption and deposition for phthalocyanine layer-by-layer thin films using an optical waveguide sensor utilizing surface plasmon resonance

A novel optical waveguide sensor utilizing surface plasmon resonance (SPR) that enables the measurement of optical absorption and the thickness of a thin film was proposed. A BK-7 glass slide was used as a waveguide core, and an Ag/Au film of 5 mm width and transparent polymethyl methacrylate-co-methacrylic acid (PMMA-co-PMAA) were consecutively deposited to develop the sensor. The PMMA-co-PMAA film was used to control the SPR wavelength. This sensor allows us to measure the optical absorption and thickness of the deposited film using the evanescent wave from the waveguide and the SPR phenomena, respectively. In order to demonstrate this, a layer-by-layer deposit of a film of water-soluble phthalocyanine dye (Alcian blue, pyridine variant, AB) and polystyrenesulfonate was observed. Additionally, adsorptions from a mixed solution of AB and polydiallyldimethylammonium chloride were observed.

Detection of Initial Stage of Aluminum Corrosion in NaCl Solution Utilizing Surface Plasmon Resonance

Surface plasmon resonance (SPR) spectra on Al films in the Kretschmann configuration is investigated aiming at the rapid detection of the Al corrosion in NaCl solution. The angle of the dip, occurred in the SPR spectra, was observed to decrease in the first 20 min and then increase with the increase of the immersion time. Calculations based on a simple multilayer model suggest that the observed initial decrease and the subsequent increase in the dip angle correspond to the thinning of the oxide layer and that of Al, respectively. The model also explains the observed deepening of the dip. The decrease in the effective Al thickness is estimated to be about 10 nm after the immersion in 3 wt% NaCl solution for 20 hours, though the quantitative discussion becomes difficult for longer immersion time. The corrosion is surely detectable for the change smaller than 5 nm in the effective Al thickness corresponding to the immersion time of 2 hours. The results indicate that the SPR-based method is promising for detecting the initial stage of Al corrosion in nanoscale.

Direct Comparison of Label-Free Biosensor Binding Kinetics Obtained on the Biacore 8K and the Carterra LSA.

Funding pressure on the pharmaceutical industry to deliver new medicines to the market under aggressive timelines has led to a demand for analytical tools with higher detection sensitivity, increased throughput, and automation to speed up research and discovery efforts and converge upon clinically fit leads faster. In the quest for therapeutic antibodies, the early adoption of interaction analysis platforms utilizing surface plasmon resonance (SPR) detection provides insightful molecular-level information about the binding properties of antibody libraries that are key to understanding an antibody's mechanism of action and can guide the library-to-leads triage. Here, we sought to compare the binding kinetics obtained on two state-of-the-art high-throughput SPR platforms in an independent study conducted by unrelated groups located on different continents. We show that when experiments were performed by skilled users adhering to SPR best practices and allowed freedom in their assay design, the two platforms yielded near-identical results, establishing them both as reliable tools in accelerating the characterization of antibody libraries in providing critical information needed to advance leads to the clinic.

Photodriven Regeneration of G-Quadruplex Aptasensor for Sensitively Detecting Thrombin.

Aptamers have been widely used as recognition elements in electrochemical sensors. However, as the most expensive consumable, the aptasensors regeneration is still a critical challenge for sustainable feasibility and attracting great interest from researchers, due to the high affinity between the aptamers and their targets (the dissociation constant Kd is low to subnanomolar or nanomolar). In this work, we propose a photochromic five-azobenzene-inserted thrombin-aptamer based aptasensor to improve the regenerativity. With ultraviolet light exposure, the trans-structure of azobenzene changes to cis-structure, and open the folded aptamer to realize the aptasensor regeneration. The limit of detection can be sensitive to 3 pM (S/N = 3). The thrombin concentrations were detected to be 2.48 ± 0.02 and 20.26 ± 0.98 nM (n = 3) in duck whole blood and blood serum, respectively. Utilizing surface plasmon resonance, we demonstrated that the certain azobenzene moieties can exactly increase Kd of aptamer-thrombin bounding. The photodriven conversion of thrombin-aptamer from G-quadruplex to loosen structure approaches a convenient regeneration for aptasensor, which will promote its popularization and sustainable feasibility.

Laser-induced nano-heater performance of B4C submicrometer spherical particles fabricated by pulsed laser melting in liquid

Gold nanoparticles as promising nano-heater particles utilizing surface plasmon resonance have been extensively studied for various chemical and medical applications, even though the suitable wavelength for nano-heater is only in the visible range and possible maximum temperature is limited due to its relatively low melting point. About a decade ago, a technique called pulsed laser melting in liquid (PLML) was developed to fabricate submicrometer spherical particles as main products. In this process, particles in the submicrometer size range are effectively heated over the melting point by laser irradiation, indicating that submicrometer spherical particles can be developed as novel heater particles that may overcome the drawback of gold nanoparticles. This study examined the potentials of PLML-fabricated B4C submicrometer spherical particles as nano-heater particles since B4C has a wider optical absorption wavelength range and higher melting point than gold. From the thermal modification induced by melting the materials in contact with the B4C particles, the highest attained temperature was estimated by laser irradiation. This experiment showed that B4C particles have sufficient response in 300–1100 nm wavelength range and can act as nano-heater even at temperatures over 2000 K. Thus, B4C submicrometer spherical particles can be used as novel space-selective heater particles.

Assaying with PCF-based SPR refractive index biosensors: From recent configurations to outstanding detection limits

Abstract Optical sensing has undergone tremendous advancements with the advent of photonic crystal fibers (PCFs). Similarly, optical sensing utilizing surface plasmon resonance (SPR) operation has produced remarkable outcomes and new paradigms for providing prompt and label-free platforms for ultra-sensitive and high-resolution determinations in chemical, biological, and related sensing applications. Here we review refractive index photonic crystal fiber surface plasmon resonance biosensors (RI PCF SPRBs) with a focus on low, high, and wide-ranged RI PCF SPRBs. A performance comparison based on operating refractive index range amongst various RI PCF SPRBs shows that, to date, most of the RI PCF SPRBs proposed and/or fabricated belong to the high index category. Due to their extensive operating range, wide-ranged RI PCF SPRBs can function both as low and as high RI PCF SPRBs making them more attractive for lab-on-photonic crystal fiber (LOPCF), lab-in-photonic crystal fiber (LIPCF), and allied applications, where one or more laboratory functions are scaled to a single device for in vitro or in vivo screening and analysis. It is suggested that future research should continue to improve upon sensing metrics based on innovativeness not only in core and cladding designs but also in optimization of structural parameters and implementation of new plasmonic materials such as silicene, germanene, and phosphorene whose growths have been demonstrated recently.

Plasmonic Sensing on Symmetric Nanohole Arrays Supporting High-Q Hybrid Modes and Reflection Geometry.

Refractometric sensors utilizing surface plasmon resonance (SPR) should satisfy a series of performance metrics, bulk sensitivity, thin-film sensitivity, refractive-index resolution, and high-Q-factor resonance, as well as practical requirements such as manufacturability and the ability to separate optical and fluidic paths via reflection-mode sensing. While many geometries such as nanohole, nanoslit, and nanoparticles have been employed, it is nontrivial to engineer nanostructures to satisfy all of the aforementioned requirements. We combine gold nanohole arrays with a water-index-matched Cytop film to demonstrate reflection-mode, high-Q-factor (Qexp = 143) symmetric plasmonic sensor architecture. Using template stripping with a Cytop film, we can replicate a large number of index-symmetric nanohole arrays, which support sharp plasmonic resonances that can be probed by light reflected from their backside with a high extinction amplitude. The reflection geometry separates the optical and microfluidic paths without sacrificing sensor performance as is the case of standard (index-asymmetric) nanohole arrays. Furthermore, plasmon hybridization caused by the array refractive-index symmetry enables dual-mode detection that allows distinction of refractive-index changes occurring at different distances from the surface, making it possible to identify SPR response from differently sized particles or to distinguish binding events near the surface from bulk index changes. Due to the unique combination of a dual-mode reflection-configuration sensing, high-Q plasmonic modes, and template-stripping nanofabrication, this platform can extend the utility of nanohole SPR for sensing applications involving biomolecules, polymers, nanovesicles, and biomembranes.

High performance dual core D-shape PCF-SPR sensor modeling employing gold coat

In this paper, an enhanced performance of dual core D-shape photonic crystal fiber utilizing surface plasmon resonance (DD-PCF-SPR) based sensor is numerically proposed and analyzed. The thickness of gold and pitch parameter are optimized to 30 nm and 1.9 um, respectively, which ensures superior sensor performance. It is revealed; at optimized geometrical parameter, the offered sensor displays a supreme wavelength sensitivity of 8000 nm/RIU, wavelength resolution of 1.25 × 10−5 RIU, a supreme amplitude sensitivity of 700 RIU−1, amplitude resolution 1.7857 × 10−5 RIU and a figure of merit (FoM) of 138 RIU−1 due to the analyte refractive index changing from 1.47 RIU to 1.48 RIU. The identifying features are investigated using modal analysis based finite element method (FEM) incorporating COMSOL commercial software. Finally, a relative review is executed comparing amplitude sensitivity, resolution and wavelength sensitivity of the offered sensor with previously reported sensors. As high sensitivity, simple structure, and tremendous linear polynomial characteristics, the offered sensor will be a talented candidate for the detection of various biochemical and biological samples (DNA, mRNA, proteins, sugar).

Optical Constant Determination of Crosslinked Chitosan-Polyethylene Glycol (PEG) using Attenuated Total Reflection Method by Surface Plasmon Resonance Phenomenon

Application of chitosan as a sensing layer for heavy metal ions in surface plasmon resonance (SPR)-based sensor with Kretschmann configuration has been done extensively using polypyrrole and gruteraldehid. The deposition methods that are very widely used in depositing chitosan onto the sensing surface are spin coating, electrodeposition and dip coating (for SPR based fiber optic sensor). The deposition technique of chitosan-polyethylene glycol (PEG) composite material as sensing layer in SPR based sensor by using the drop-casting method has not been done to the best of our knowledge. In order to use chitosan-PEG composite material as a sensing layer for heavy metal ion detection, it is necessary to determine the optical constant of chitosan-PEG which is deposited by the drop-casting method. The refractive index of chitosan-PEG with mass composition 0.4 grams chitosan and 0.04 grams PEG was determined by attenuated total reflection (ATR) method by utilizing surface plasmon resonance phenomenon on the prism/silver/chitosan-PEG interfaces in Kretschmann configuration. The refractive index then was extracted from the ATR curve by using Winspall software. Based on the experimental result, it was found that the ATR curve was shifted from 44.3° to 68.9° with the presence of a chitosan-PEG layer deposited onto the silver surface, about 0.01 ml in solution form. From the fitting result, it was found that the refractive index of chitosan-PEG was n = 1.32.

Engineering Gold Nanorod–Copper Sulfide Heterostructures with Enhanced Photothermal Conversion Efficiency and Photostability

Plasmonic gold nanorods (Au NRs)-copper sulfide heterostructures have recently attracted much attention owing to the synergistically enhanced photothermal properties. However, the facile synthesis and interface tailoring of Au NRs-copper sulfide heterostructures remain a formidable challenge. In this study, the rational design and synthesis of Au NRs-Cu7 S4 heterostructures via a one-pot hydrothermal process is reported. Specifically, core-shell and dumbbell-like Au NRs-Cu7 S4 heterostructures are obtained with well-controlled interfaces by employing the Au NRs with different aspect ratios. Both core-shell and dumbbell-like Au NRs-Cu7 S4 have proven effective as photothermal therapy agents, which offer both high photothermal stability and significant photothermal conversion efficiency up to 62%. The finite-difference time domain simulation results confirm the coupling effect that leads to the enhanced local field as well as the optical absorption at the heterostructure interface. Importantly, these Au NRs-Cu7 S4 heterostructures can be compatibly used as an 808 nm laser-driven photothermal therapy agents for the efficient photothermal therapy of cancer cells in vitro. This study will provide new insight into the design of other noble metal-semiconductor heterostructures for a broad range of applications utilizing surface plasmon resonance enhancement phenomena.

Di-functional nanocomposite films for efficient conversion and storage of solar energy

There is no doubt that renewable sources, such as solar energy, have played an important role in the future renewable energy system. And solar heat has great potential and a high contribution towards the future energy supply. How to directly collect, fast convert and efficiently store solar heat is still a problem to be solved in solar energy application. Herein, the di-functional nanocomposite film was designed and fabricated toward efficient conversion and storage of solar thermal energy. The di-functional nanocomposite film was feasibly prepared by uniformly imbedding phase change materials (PCMs) and Au nanoparticles into PVA matrix uniformly through the hydrogen-bonding interactions. The Au nanoparticles, as photothermal nanoabsorbers, with a low concentration (~0.23% m/m), can instantly and intensely realize solar-to-heat conversion by utilizing surface plasmon resonance. Subsequently, efficiently conversion heat could be stored into the PCMs through film-interior reversible phase transformation. Meanwhile, no leakage and evaporation of the PCMs is observed due to the strong hydrogen-bonding confinement at interface between PCMs and the film matrix. This kind of di-functional nanocomposite films is of great importance and wide usage in the fields of solar thermal energy conversion and storage, thermal interface materials, protective layers and sensing, etc.

Evidence That Factor VIII Forms a Bivalent Complex with the Low Density Lipoprotein (LDL) Receptor-related Protein 1 (LRP1): IDENTIFICATION OF CLUSTER IV ON LRP1 AS THE MAJOR BINDING SITE

Hemophilia A is a bleeding disorder caused by a deficiency in coagulation factor VIII (fVIII) that affects 1 in 5,000 males. Current prophylactic replacement therapy, although effective, is difficult to maintain due to the cost and frequency of injections. Hepatic clearance of fVIII is mediated by the LDL receptor-related protein 1 (LRP1), a member of the LDL receptor family. Although it is well established that fVIII binds LRP1, the molecular details of this interaction are unclear as most of the studies have been performed using fragments of fVIII and LRP1. In the current investigation, we examine the binding of intact fVIII to full-length LRP1 to gain insight into the molecular interaction. Chemical modification studies confirm the requirement for lysine residues in the interaction of fVIII with LRP1. Examination of the ionic strength dependence of the interaction of fVIII with LRP1 resulted in a Debye-Hückel plot with a slope of 1.8 ± 0.5, suggesting the involvement of two critical charged residues in the interaction of fVIII with LRP1. Kinetic studies utilizing surface plasmon resonance techniques reveal that the high affinity of fVIII for LRP1 results from avidity effects mediated by the interactions of two sites in fVIII with complementary sites on LRP1 to form a bivalent fVIII·LRP1 complex. Furthermore, although fVIII bound avidly to soluble forms of clusters II and IV from LRP1, only soluble cluster IV competed with the binding of fVIII to full-length LRP1, revealing that cluster IV represents the major fVIII binding site in LRP1.