Fiber cladding dual channel surface plasmon resonance sensor based on S-type fiber

Fiber cladding surface plasmon resonance(SPR)sensors have few structures,and a clad SPR sensor based on S-type fiber is proposed in this paper.This new type of fiber cladding SPR sensor was formed by electrofusing an S-shaped structure on the fiber to couple the light in the fiber core to the cladding.In this paper,the effects of fiber parameters on the performance of the sensor were studied by simulation and experiment.Based on the conclusion that the smaller the core diameter is,the closer the working band of the SPR resonance is to long wavelengths,and that the geometric characteristics mean that a multimode fiber can receive the fiber cladding light from a small core diameter few-mode fiber,a dual channel SPR sensor with a double S-type fiber cascade was proposed.In the refractive index detection range of 1.333–1.385refractive index units(RIU),the resonant working band of channel I is 627.66 nm–759.78 nm,with an average sensitivity of 2540.77 nm/RIU,and the resonant working band of channel II is 518.24 nm–658.2 nm,with an average sensitivity of2691.54 nm/RIU.The processing method for the S-type fiber cladding SPR sensor is simple,effectively solving the problem of this type of SPR sensor structure and the difficult realization of a dual channel.The sensor is expected to be used in the fields of medical treatment and biological analysis.

Dual-channel fiber-optic surface plasmon resonance sensor with cascaded coaxial dual-waveguide D-type structure and microsphere structure

To address the restriction of fiber-optic surface plasmon resonance(SPR) sensors in the field of multi-sample detection, a novel dual-channel fiber-optic SPR sensor based on the cascade of coaxial dual-waveguide D-type structure and microsphere structure is proposed in this paper. The fiber sidepolishing technique converts the coaxial dual-waveguide fiber into a D-type one, and the evanescent wave in the ring core leaks, generating a D-type sensing region;the fiber optic fused ball push technology converts the coaxial dual waveguides into microspheres, and the stimulated cladding mode evanescent wave leaks, producing the microsphere sensing region. By injecting light into the coaxial dual-waveguide middle core alone, the sensor can realize single-stage sensing in the microsphere sensing area;it can also realize dual-channel sensing in the D-type sensing area and microsphere sensing area by injecting light into the ring core. The refractive index measurement ranges for the two channels are 1.333–1.365 and 1.375–1.405, respectively, with detection sensitivities of 981.56 nm/RIU and 4138 nm/RIU. The sensor combines wavelength division multiplexing and space division multiplexing technologies, presenting a novel research concept for multi-channel fiber SPR sensors.

Analysis of 17β-Estadiol from Sewage in Coastal Marine Environment by Surface Plasmon Resonance Technique

In this study, surface plasmon resonance （SPR） for monitoring 17β-eatradiol （E2） was developed. The small molecule E2 was immobilized on a CM5 sensor chip for an indirect competitive immunoassay to detect E2. The SPR response bahed on the antigen-antibody reaction was measured by injecting the sample solution into the flow system. The limitation of detection was 0.445 μg/L. The developed SPE-SPR system was applied to analyze the seawater samples. Recovery of E2 was 91.6%-93. 1%. Relative standard deviations（RSD） for the E2 assay were between 10.9%-15.1% （n = 3）. The range of determination of E2 samples from the sewage in the coastal marine environ-ment was between ND（lower than detection limit） and ca. 11.78 ng/L.

Detection of Penicillin via Surface Plasmon Resonance Biosensor

A method of using Au colloid to capture the decomposed product of penicillin, penicillamine, on a surface plasmon resonance（SPR） biosensor for the quantitative determination of penicillin was developed. Based on the de-composition of penicillin to generate penicillamine and penilloaldehyde, a high sensitive biosensor for detecting penicillin was also developed. In our experiment, it was penicillamine rather than penicillin that has been measured. This is because penicillamine contains a functional group that makes it self-assembling on Au colloid to increase the molecular weight so as to improve the surface plasmon resonance signal. On a UV-Vis spectrophotometer, a high concentration of penicilliamine-Au complex was determined, indicating that penicillamine was already well combined with Au colloid. The method, using the combination of Au colloid with penicillamine, proved to detect penicillin.

Advances in Phase Detection Technique of Surface Plasmon Resonance Biosensor

Surface plasmon resonance (SPR) sensing is an optical method based on evanescent wave.SPR biosensor can detect interaction of label-free biomolecules in real-time.With further development,it can become a research instrument in proteomics.SPR biosensor can be divided intensity measurement and phase measurement,and the latter possesses higher sensitivity than the former one.This paper attempts to summarize the SPR phase detection theory,discuss the major developments,compare the merits and deficiencies of various methods,and look forward to future prospects.

Characteristics of Surface Plasmon Resonance Imaging lnterferometer

In recent life science research,identifying and characterizing entire biomolecular interaction networks is prerequisite to understanding cellular processes on a molecular and biophysical level.A surface plasmon resonance (SPR) imaging interferometer based on spatial phase modulation detection is presented to meet this demand.In this method,the SPR sensing chip surface is illuminated with collimated parallel light beam,and a Wollaston prism is introduced into the reflected light path to produce the interference of polarized light reflected from SPR sensing chip.Information of biomolecular interactions can be obtained by extracting the phase change from the SPR interference patterns.Using our interferometer,we made experiments on a series concentration of NaCl solutions to investigate its detection range,linearity,sensitivity and resolution.The results indicate that the SPR imaging interferometer is mainly sufficient for biomolecular interaction detection.

Surface plasmon resonance sensor based on molecularly imprinted films for the detection of pentaerythritol tetranitrate （PETN）

A novel surface plasmon resonance （SPR） sensor based on molecularly imprinted films （MIFs） was developed for the detection of pentaerythritol tetranitrate （PETN）. In this work, the thin MIFs were formed on a gold sensor chip through thermal co-polymerization of functional mono- mers （methacrylic acid, MAA） and crosslinking monomers （ethylene glycol dimethacrylate, EGD- MA） in the presence of template molecules PETN. The template molecules PETN were subsequently removed from the MIFs simply by rinsing the MIFs with a mixture of acetonitrile and acetic acid 9：1 （ v/v）, thus the recognition sites were formed for specific detection of PETN. According to the mass coverage equation, the surface coverage of removed PETN from MIFs was about 10. 8 ng/mm~. The developed SPR sensor allowed for the detection of PETN at concentration down to 10-~~ mol/L. A control experiment utilizing an analogue cyclotrimethylenetrinitramine （RDX） showed MIFs＇ good selectivity to PETN.

Improvement of the Specificity of Surface Plasmon Resonance with BSA-modified Chip

A chip was modified with bovine serum albumin （BSA）, then interaction between glutathione （GSH） immobilized on the top of BSA and glutathione-S-transferase （GST） was examined, using surface plasmon resonance （SPR）. The SPR results showed that BSA-modified chip was effective not only in binding the target proteins but also in suppressing the nonspecific binding （NSB） of proteins.

Development and Application of Time-Resolved Surface Plasmon Resonance Spectrometer

Surface plasmon resonance (SPR) sensor, an optical sensor exploiting special electromagnetic waves-surface plasmon polaritons to probe interactions between an analyte in solution and a molecular recognition element immobilized on the SPR sensor surface, has been widely used in various realms, such as investigating biomolecular interactions and binding properties, detection of biological and chemical analytes, environmental monitoring, food safety and medical diagnostics. This paper reviews the development of SPR sensors and SPR commercial instruments, and emphatically introduces the time-resolved surface plasmon resonance (TR-SPR) techniques. The excellent performances of high sensitivity and rapid detection are easily achieved with TR-SPR spectrometer, whereas the traditional SPR spectrometer cannot be accomplished. Therefore, TR-SPR spectrometer is appropriate for real time analysis of bio-recognition events and small molecular dynamics. However, only two commercial TR-SPR instruments have been exhibited at present, Thermo FT-SPR 100 and Autolab ESPRIT (SPRINGLE). Unfortunately, the high-priced instruments are not suitable for extensive applications in laboratories at present. Herein, a novel commercial TR-SPR spectrometer has been introduced in this review.

Surface plasmon polaritons frequency-blue shift in low confinement factor excitation region

Surface plasmon polaritons'(SPPs')frequency blue shift is observed in finite-difference time-domain(FDTD)simulation of parallel electron excitation Au bulk structure.Comparing with cold dispersion of SPPs,an obvious frequency blue shift is obtained in low confinement region excitation simulation results.Then,according to SPPs'transverse attenuation characteristics,the excited frequency mode instead of cold dispersion corresponding frequency mode matches it.Thence,this excited mode is confirmed to be SPPs'mode.As is well known the lower the frequency,the smaller the confinement factor is and the lower the excitation efficiency,the wider the bandwidth of excited SPPs is.And considering the attenuation in whole structure,the excited surface field contains attenuation signal.In a low confinement factor region,the higher the SPPs'frequency,the higher the excitation efficiency is,while broadband frequency information obtained in attenuation signal provides high frequency information in stimulation signal.Thence,in the beam-wave interaction,as the signal oscillation time increases,the frequency of the oscillation field gradually increases.Thus,compared with cold dispersion,the frequency of excited SPP is blueshifted This hypothesis is verified by monitoring the time domain signal of excited field in low and high confinement factor regions and comparing them.Then,this frequency-blue shift is confirmed to have commonality of SPPs,which is independent of SPPs'material and structure.Finally,this frequency-blue shift is confirmed in an attenuated total reflection(ATR)experiment.Owing to frequency dependence of most of SPPs'devices,such as coherent enhancement radiation and enhancement transmission devices,the frequency-blue shift presented here is of great influence in the SPPs applications.

Molecularly imprinted polymers for highly sensitive detection of morphine using surface plasmon resonance spectroscopy

Molecular imprinting technology is applied in surface plasmon resonance spectroscopy for highly sensitive and selective detection of morphine（MO）.As SPR-based sensor of MO,the preparation of molecular imprinted polymer is as follows： methacryhc acids（MAA）,ethylene glycol dimethacrylate（EGDMA）,azodiisobutyronitrile（AIBN） were used as functional monomer,cross-linker and initiator,respectively.The experiment results showed that morphine imprinted polymer had the performance of high sensitivity and specificity,i.e.the relative signal of SPR response was proportional to the concentration of morphine in acetonitrile in the range of 10^（-9）mol/L to 10^（-6）mol/L（1 ppb-1 ppm） with LOD of 10^（-10）mol/L,and MO was distinguished from its analogs,such as codeine.

Molecularly Imprinted Polymers Based Surface Plasmon Resonance Sensor for Sulfamethoxazole Detection

Sulfamethoxazole(SMX)is a sulfonamide antibiotic primarily used to treat urinary tract infections and used in veterinary and industrialized husbandry to treat diseases and food additives.Like other antibiotics,SMX is considered as a pollutant in water and food that threaten local life.This study developed a surface plasmon resonance(SPR)sensor chip that is fast,highly selective,and reusable,and requires no pretreatment for detecting SMX.As a receptor,SMX imprinted methacrylic acid-2-hydroxyethyl methacrylate-ethylene glycol dimethacrylate polymer[poly(MAA-HEMA-EGDMA)]was used.The surface of the gold SPR chips was coated with a drop-casting method.The nanofilm coated chips were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM),ellipsometer,contact angle measurement,and Fourier-transform infrared spectrometry(FTIR).Imprinting factor(IF)was calculated as:ΔR[MIP(molecularly imprinted polymers)]/ΔR[NIP(non-imprinted)]=12/3.5=3.4.Limit of detection(LOD)and limit of quantification(LOQ)values were calculated with 3 s/m and 10 s/m methods,and the results were found to be 0.0011μg/L for LOD 0.0034μg/L for LOQ.Adsorption studies on both standard SMX solution and commercial milk samples were applied.Also,we investigated the developed chip’s reusability,storability,and selectivity with amoxicillin and cefalexin.

Comparison of Surface-enhanced Raman Scattering Spectra of Two Kinds of Silver Nanoplate Films

Surface-enhanced Raman scattering（SERS） spectra of different silver nanoplate selt-assembled tllmS at different excitation wavelengths were fairly compared. Shape conversion from silver nanoprisms to nanodisks on slides was in situ carried out. The SERS spectra of 4-mercaptopyridine（4-MPY） on these anisotropic silver nanopar- ticle self-assembled films present that strong enhancement appeared when the excitation line and the surface plasmon resonance（SPR） band of silver substrate overlapped. In this model, the influence of the crystal planes of silver na- noplates on SERS enhancement could be ignored because the basal planes were nearly unchanged in two kinds of silver nanoplate self-assembled films.

纳米金用于SPR传感器检测小分子的研究进展

近年来,表面等离子体共振(Surface Plasmon Resonance,SPR)技术因具有可实时、动态监测SPR芯片上分子间相互作用的优点,而广泛应用于小分子传感检测领域。信号放大是小分子SPR传感器的重要研究内容,它决定小分子能否被检出及传感器灵敏度,因此信号放大技术对其发展非常重要。纳米金因其高电子密度、介电特性及易修饰等特性而用于多种传感器的信号放大。重点介绍近5年来纳米金在小分子SPR传感器方面的应用情况,旨在为小分子SPR传感器的进一步发展提供参考依据。

群智能优化的动态基线调整在光纤SPR传感器信号处理中的应用

将谱宽(β)、基线下测量点数(m)、面积比(λ)作为最佳动态基线的选择依据,在两级适应度函数条件下,利用粒子群优化算法跟踪β、m、λ,寻找最佳组合参数下的动态基线,有效克服了传统基线选择较为随意的问题。搭建了光纤SPR测试装置,采集8种不同浓度的蔗糖标准溶液的光谱数据,将4种质心跟踪法进行实验对比。结果表明群智能优化动态基线法的预测精度和相关性均最好,可以有效提取质心参数,消除光源波动对测试结果的影响,为实现光纤SPR实时在线监测提供了一种有效途径,其共振波长拟合度为0.996 3,RMSE为1.78。另外,考察了三种质心计算参数的主导地位,结果表明:在设定相同适应度情况下,固定m方法效果最好,进而为质心参数的选择控制提供有效依据。

Effect of prism material on design of surface plasmon resonance sensor by admittance loci method

A theoretical study on the design of surface plasmon resonance （SPR） based sensor by admittance loci method has been reported in this paper with the main emphasis being given to the effect of the prism material in a conventional Kretschmann structure in attenuated total internal reflection （ATIR） mode. Several sensing media such as water, acetone, methanol etc have been investi- gated using different types of prism materials to study their effect on SPR sensing and validated by corresponding admittance loci plots as well as respective SPR curves. The performance of the sensor based on choice of the prism material has been discussed with the help of sensitivity plots giving due to the importance of dynamic range of the designed sensor. Simulations have been carried out in MATLAB 7.1 environment.

Interaction of straight chain alcohol vapors with self-assembled MOF film by surface plasmon resonance sensing and imaging

Interaction of straight chain alcohol vapors with MOF-199-functionalized films was studied by SPR. The signals had linear relationships with the concentration of alcohols over a wide range from 0 to 70% （v/v） and were reversible in proportional to the chain length, with R2 all above 0.99.

Nano-film aluminum-gold for ultra-high dynamic-range surface plasmon resonance chemical sensor

An analytical and experimental study of nanofilm aluminum (Al) for ultra-high dynamic range surface plasmon resonance (SPR) biosensor is presented in this article. A thin film of 16 nm Al is proposed for metallic sensing layer for SPR .s*ensoi For the protective layer, a 10 nm of gold (Au) layer was configured on top of Al as a protection layer. This ultra-high dynamic range of SPR biosensor reached the bulk refractive index sample limit up to 1.45 RIU. For the analytical study, with the assumption of anisotropic refractive indices experiment, the dynamic range showed a refractive index value of around 1.58 RIU. The refractive index value limit achieved by the proposed sensing design is potentially implemented in various applications, such as in chemical detection and environ- mental monitoring study with high refractive index solution sample. The experimental results are presented as a proof-of-concept of the proposed idea.

Single polarization photonic crystal fiber filter based on surface plasmon resonance

In this paper,we propose a photonic crystal fiber(PCF)polarization filter based on surface plasmon resonance(SPR)characteristics.Gold nanowire is used as the active plasmonic material.Light into silica core becomes coupled to gold nanowire stimulating SPR. It soplits light into two orthogonal(x-polarization and y-polarization)polarization in the second order of surface plasmon polarization.Numerical investigations of the proposed PCF filter is finite element method(FEM).By position,the performance of the propsed PCF filter is inspected rigorously.Filtering of any polarization can be obtained by properly placing the metal wires.The maximum cnfinement loss of x-polarization is 692.25dB/cm and y-polarization is 1.13dB/cm offers at resonance position 1.42μm.Such a confinement loss difference between two orthogonal polarizations makes PCF a talented candidate to filter devicees.Consequently,the recommended PCF structure is useful for polarization device.

波长型SPR检测仪的灵敏度探讨

利用自行设计构建的可变入射角的波长型表面等离子体共振(SPR)检测仪,在不同浓度的蔗糖溶液中测定了不同入射角度(80°～66°)的共振曲线,经过处理得到共振峰位、半高宽及灵敏度随入射角和样品折射率变化的三维图像.在此基础上探讨了波长型SPR检测仪的主要参数对仪器性能的影响,从理论和实验上证明了影响灵敏度的主要因素为共振波长,并且随着共振波长的增大,检测灵敏度迅速提高.