High-performance Surface Plasmon Resonance Research Articles

Theoretical investigation of detection accuracy of surface plasmon resonance sensor with dielectric layer

We theoretically investigated detection accuracy (DA) of a surface plasmon resonance (SPR) sensor with a top dielectric layer. The effects of the variation of thickness and the material of the dielectric layer on the DA of the SPR sensor were investigated. The result indicated that adding a top dielectric layer with a small refractive index (less than the refractive index of the analyte) can improve the DA of a traditional SPR sensor. In addition, by comparing the variation law of the DA and the electric field intensity at the analyte–dielectric interface of the SPR sensor, we studied the physical mechanism of DA variation. This study can be helpful for high-performance SPR sensor development.

Performance analysis of surface plasmon resonance sensor with high-order absentee layer**Project supported by the National Natural Science Foundation of China (Grant Nos. 11547183 and 11547241), the Higher Education and High-quality and World-class Universities, China (Grant No. PY201612), the National Key Research and Development Program of China (Grant No. 2016YFB0302003), and the Natural Science Foundation of Beijing (Grant No. 2162033).

A surface plasmon resonance (SPR) sensor with a high-order absentee layer on the top of metallic film is proposed. The performance of the SPR sensor with NaCl, MgO, TiO2 or AlAs high-order absentee layer is analyzed theoretically. The results indicate that the sensitivity and the full width at half maximum of those SPR sensors decrease with the increasing of the order of absentee layer, but the variation of the figure of merit (FOM) depends on the refractive index of absentee layer. By improving the order of absentee layer with high-refractive-index, the FOM of the SPR sensor can be enhanced. The maximum value of FOM for the SPR sensor with high-order TiO2 (or AlAs) absentee layer is 1.059% (or 2.587%) higher than the one with one-order absentee layer. It is believed the proposed SPR sensor with high-order absentee layer will be helpful for developing the high-performance SPR sensors.

Figure of Merit Enhancement of a Surface Plasmon Resonance Sensor Using a Low-Refractive-Index Porous Silica Film.

In this paper; the surface plasmon resonance (SPR) sensor with a porous silica film was studied. The effect of the thickness and porosity of the porous silica film on the performance of the sensor was analyzed. The results indicated that the figure of merit (FOM) of an SPR sensor can be enhanced by using a porous silica film with a low-refractive-index. Particularly; the FOM of an SPR sensor with 40 nm thick 90% porosity porous silica film; whose refractive index is 1.04 was improved by 311% when compared with that of a traditional SPR sensor. Furthermore; it was found that the decrease in the refractive index or the increase in the thickness of the low-refractive-index porous silica film can enlarge the FOM enhancement. It is believed that the proposed SPR sensor with a low-refractive-index porous silica film will be helpful for high-performance SPR sensors development.

Design of high performance surface plasmon resonance biosensor using silver-based sinusoidal diffraction grating

A high performance sinusoidal grating-based surface plasmon resonance (SPR) biosensor is proposed. The angular interrogation method has been used to study the performance of the sensor. The sensitivity as well as the width of the SPR curves and reflective amplitude is considered for designing the sensor. Compared with the gold(Au)-based SPR sensor, we find that the silver(Ag)-based sensor has the better performance. Numerical simulations show that the sensitivity of the Ag-based sensor is 193.9°/RIU.

Multilayer with periodic grating based high performance SPR waveguide sensor

We propose a high performance periodic grating coupled multi-layered surface plasmon resonance (SPR) waveguide based on Al+Au. High sensitivity is obtained by using grating filled with silver instead of air. Further sensor's performance is analysed by optimising width and thickness of SPR active metal layer as well as grating period also. Using finite difference time domain (FDTD) method, we have shown that sensitivity and detection accuracy can be improvised using appropriate multi-layered grating configuration.

On the electric field enhancement and performance of SPR gas sensor based on graphene for visible and near infrared

We propose a high performance surface plasmon resonance (SPR) affinity gas sensor based on graphene on Ag in visible and near infrared. Proposed sensor configuration has been optimized for maximum surface plasmon field at the sensing layer interface. The field intensity enhancement factor at sensing layer interface is found to be higher than that of silicon over layer on Ag thereby increasing the imaging sensitivity by 340%, 120% and 82% and detection accuracy by 440%, 150% and 100% as compared to Si on Ag configuration at λ=653nm, λ=850nm and λ=1000nm respectively. The performance of the sensor is found to be high over a broad refractive index range (1.0000–1.0008) of gaseous analyte with sensor resolution of 8×10−5RIU and 2×10−5RIU at λ=653nm and λ=1000nm respectively. We believe the proposed SPR based gas sensor configuration will open a new route for efficient gas sensing by riding on the advantage of graphene and latest nanofabrication techniques.

Design and validation of a uniform flow microreactor

We present a design method to characterize uniform flows in a microreactor for high performance surface plasmon resonance (SPR) a general-purpose biosensor chips. The shape of the microreactor is designed based on an approximate pressure drop model. The number of micro-pillars and the slopes of the inlet and outlet linear chambers are two dominant parameters used to minimize the velocity difference in the microreactor. The flow uniformity was examined quantitatively by numerical and experimental visualization methods. A computational fluid dynamics (CFD) analysis demonstrates that the designed microreactor has a fairly uniform velocity profile in the reaction zone for a wide range of flow rates. The velocity field in the fabricated microreactor was measured using the micro-particle image velocimetry (μ-PIV) method, and the flow uniformity was confirmed experimentally. The performance of the uniform flow microreactor was verified using the fluorescence antibody technique.

Design of a plasmonic optical sensor probe for humidity-monitoring

High performance surface plasmon resonance (SPR) sensor is proposed for relative humidity (RH) monitoring. The structure is based on widely used 2S2G chalcogenide glass and gold as SPR active metal applied with silica-based porous film. The angular interrogation method has been used to study the performance of the sensor in terms of intrinsic sensitivity (SI) that includes the width and shifts of SPR curve for the entire RH-range between 0% and 100%. The effect of temperature is also studied on the proposed sensor's performance. Any possibility of oxidation problem to the proposed SPR sensor due to constantly being in contact with humid environment may be addressed by using a stable buffer layer. Intrinsic sensitivity of the proposed sensor is significantly high for almost entire range of RH values. The proposed sensor has a good resolution of the order of 10−2% RH.

Graphene oxide and dextran capped gold nanoparticles based surface plasmon resonance sensor for sensitive detection of concanavalin A

Carbohydrate–protein interactions mediate the important physiological and pathophysiological processes in living organism. Their study has attracted great attention due to its importance in understanding these biological processes and in fabricating biosensors for diagnostics and drug development. Here, by using concanavalin A (ConA) as a model protein, a novel surface plasmon resonance (SPR) sensor was developed for sensitive detection ConA. In this sensing platform, dextran (Dex) capped gold nanoparticles (Dex-Au NPs) were initially synthesized in one-pot and utilized as amplification reagent. After deposition of graphene oxide (GO) on the SPR gold film, phenoxy-derivatized dextran (DexP) was assembled onto the GO-modified gold chip surface through π–π interaction. The resultant GO/DexP sensing interface could specifically capture ConA which could further react with Dex-Au NPs through the specific interaction between ConA and Dex, forming a sandwich configuration. The morphologies and the electrochemistry of the formed sensing surface were investigated by using scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammogram. Owing to the high surface area of GO and the excellent amplification of Dex-Au NPs, the developed sandwich SPR sensor successfully fulfilled the sensitive detection of ConA in the range of 1.0–20.0μgmL−1 with a detection limit of 0.39μgmL−1. Compared to the direct assay format, the prepared sandwich SPR sensor led to an improvement of 28.7-fold in the sensitivity. The results demonstrated that the proposed method might provide a new direction in designing high-performance SPR biosensors for sensitive and selective detection of a wide spectrum of biomolecules.

Rational design of high performance surface plasmon resonance sensors based on two-dimensional metallic hole arrays

We have rationally designed two-dimensional Au and Ag hole arrays for high performing surface plasmon resonance (SPR) sensing. The figure-of-merit (FOM), which is defined as sensitivity/linewidth, is found to be highly geometry-dependent. For sensitivity, we find it is equal to the period of array when exciting low order surface plasmon modes at low incident angle. Therefore, increasing period improves sensitivity. On the other hand, narrow linewidth can be obtained from small hole size so that the radiative decay loss is minimized. By using a pair of orthogonally oriented polarizer and analyzer, the signal-to-noise ratio (SNR) can be greatly enhanced due to the elimination of the nonresonant reflection background. As a proof of our strategy, we have obtained FOM larger than 100/RIU and SNR higher than 110 from Au arrays. Our results show the importance of understanding the basic properties of surface plasmon polaritons in order to systematically optimize the performance of the plasmonic system for a given application.

Magnetic Nanoparticle Enhanced Surface Plasmon Resonance Sensing and Its Application for the Ultrasensitive Detection of Magnetic Nanoparticle-Enriched Small Molecules

Magnetic nanoparticles (MNPs) have been frequently used in bioseparation, but their applicability in bioassays is limited due to their extremely small size so that sensitive detection is difficult to achieve using a general technique. Here, we present an amplification technique using MNPs for an enhanced surface plasmon resonance (SPR) bioassay. The amplification effect of carboxyl group modified Fe(3)O(4) MNPs of two sizes on SPR spectroscopy is first demonstrated by assembling MNPs on amino group modified SPR gold substrate. To further evaluate the feasibility of the use of Fe(3)O(4) MNPs in enhancing a SPR bioassay, a novel SPR sensor based on an indirect competitive inhibition assay (ICIA) is developed for detecting adenosine by employing Fe(3)O(4) MNP-antiadenosine aptamer conjugates as the amplification reagent. The results confirm that Fe(3)O(4) MNPs can be used as a powerful amplification agent to provide a sensitive approach to detect adenosine by SPR within the range of 10-10,000 nM, which is much superior to the detection result obtained by a general SPR sensor. Importantly, the present detection methodology could be easily extended to detect other biomolecules of interest by changing the corresponding aptamer in Fe(3)O(4) MNP-aptamer conjugates. This novel technique not only explores the possibility of the use of SPR spectroscopy in a highly sensitive detection of an MNP-based separation product but also offers a new direction in the use of Fe(3)O(4) MNPs as an amplification agent to design high performance SPR biosensors.

Compact and low-cost biosensor based on novel approach to spectroscopy of surface plasmons

A high-performance surface plasmon resonance (SPR) sensor based on a novel approach to spectroscopy of surface plasmons is reported. This approach employs a special diffraction grating structure (referred to as surface plasmon resonance coupler and disperser, SPRCD) which simultaneously couples light into a surface plasmon and disperses the diffracted light for spectral readout of SPR signal. The developed SPRCD sensor consists of a miniature cartridge integrating the diffraction grating and microfluidics and a compact optical system which simultaneously acquires data from four independent sensing channels in the cartridge. It is demonstrated that the SPRCD sensor is able to measure bulk refractive index changes as small as 3 × 10 −7 RIU (refractive index units) and to detect short oligonucleotides in concentrations down to 200 pM.

High-throughput SPR sensor for food safety

High-throughput surface plasmon resonance (SPR) biosensor for rapid and parallelized detection of nucleic acids identifying specific bacterial pathogens is reported. The biosensor consists of a high-performance SPR imaging sensor with polarization contrast and internal referencing (refractive index resolution 2 × 10 −7 RIU) and an array of DNA probes microspotted on the surface of the SPR sensor. It is demonstrated that short sequences of nucleic acids (20–23 bases) characteristic for bacterial pathogens such as Brucella abortus, Escherichia coli, and Staphylococcus aureus can be detected at 100 pM levels. Detection of specific DNA or RNA sequences can be performed in less than 15 min by the reported SPR sensor.

High-performance Surface Plasmon Resonance Immunosensors for TNT Detection

Detection of 2,4,6-trinitrotoluene (TNT) is an important environmental, security and health concern for the global community. TNT is a prime constituent of most of the landmines and bombs and is highly toxic and mutagenic. Various military and terrorist activities (e.g., manufacturing, waste discharge, testing and training) have resulted in extensive contamination of soil and ground water by TNT and its derivatives. Consequently, the development and application of new sensing techniques for detection and quantification of TNT has grown steadily over the years. Despite wide variety of analytical techniques, surface plasmon resonance (SPR) based immunosensors received great attention as a promising mean for TNT detection due to their advantages including high sensitivity, selectivity, good versatility and high throughput. This review explores the recent trend and advancements in immunochemical techniques for environmental monitoring and field detection of TNT. The advantages of the surface plasmon resonance as an optical signal transduction and indirect competitive immunoassay as the sensing principle are discussed with special emphasis on our investigations on TNT detection. A brief description on explosives, land-mines and the current detection techniques (bulk and trace detection) is also provided.

Compact, high performance surface plasmon resonance imaging system

We report the construction and characterization of a new compact surface plasmon resonance imaging instrument. Surface plasmon resonance imaging is a versatile technique for detection, quantification and visualization of biomolecular binding events which have spatial structure. The imager uses a folded light path, wide-field optics and a tilted detector to implement a high performance optical system in a volume 7 in. × 4 in. × 2 in. A bright diode light source and an image detector with fast frame rate and integrated digital signal processor enable real-time averaging of multiple images for improved signal-to-noise ratio. Operating angle of the imager is adjusted by linear translation of the light source. Imager performance is illustrated using resolution test targets, refractive index test solutions, and competition assays for the antiepileptic drug phenytoin. Microfluidic flowcells are used to enable simultaneous assay of three sample streams. Noise level of refractive index measurements was found to decrease proportional to the square root of the number of pixels averaged, reaching approximately 5 × 10 −7 refractive index units root-mean-square for 160 × 120 pixels image regions imaged for 1 s. The simple, compact construction and high performance of the imager will allow the device to be readily applied to a wide range of applications.

Simultaneous excitation of long and short range surface plasmons in an asymmetric structure

An asymmetric multilayer structure allowing nearly 100% simultaneous excitation of both symmetric and antisymmetric surface plasmons is proposed. It is shown that the two surface plasmons can be excited at a fixed angle of incidence with polychromatic light or with monochromatic light at different angles of incidence, depending on the design. The structure can be of interest in high-performance surface plasmon resonance sensing and in all-optical signal processing.