表面等离子共振传感器的研究进展

表面等离子体是在金属和电介质交界面上所形成的电荷层,在电磁波的激励下表面等离子体发生共振现象,影响电磁波的传播。根据这一原理制作的表面等离子共振传感器可对化学和生物等量进行探测。介绍了表面等离子共振传感器的工作原理和最新研究进展。由于具有体积小、准确度高、抗电磁干扰能力强和可用于遥测等优点,SPR传感器将有广泛的应用前景。     

表面等离子体共振成像技术的进展与应用

简单介绍了表面等离子体共振成像(SPRI)的原理之后,比较详细地介绍近年来其应用情况及相关技术的发展.     

Diffractive optical coupling element for surface plasmon resonance sensors

Design, technological features, and performance of polymeric diffractive optical coupling elements (DOCEs), developed for surface plasmon resonance (SPR) sensors are reported. The concept is based on input and output coupling of collimated and perpendicularly incident light beams to exchangeable SPR sensor chips. In the SPR sensor chips, one DOCE couples the input light beam to a (bio-)chemical sensor surface and another DOCE images the output light beam onto a detector array. The manufacturing technique is based on an injection moulding process similarly to the manufacturing process of compact discs allowing precision manufacturing and reproduction of the grating topography of the DOCEs. The DOCE-based SPR sensor chip is specifically suitable for miniaturisation and large scale production, while maintaining high optical quality and performance.     

Site-directed antibody immobilization on gold substrate for surface plasmon resonance sensors

A simple method for the site-directed immobilization of antibodies on gold substrates has been developed for surface plasmon resonance (SPR) applications. A freshly prepared gold surface on a glass slide was modified with Protein A via homobifunctional cross linker dithiobissuccinimide propionate (DSP) to achieve uniform, stable, and sterically accessible antibody coating. The density of the immobilized antibodies bound to Protein A was examined as a function of the protein concentration, buffer pH, buffer type and reaction time. The suggested scheme was also employed for the modification of gold-coated substrates for quartz crystal microbalance (QCM) applications. The modified gold surface was stable for several weeks and the reproducibility was satisfactory. The current fabrication technique could be applied to construct other immunosensors or biochips.     

Interrogation of surface plasmon resonance sensors using temporally stretched ultrashort optical pulses

We propose a novel technique that has the potential to realize interrogation of surface plasmon resonance (SPR) sensors at very high speed. In contrast to the incoherent light source used in the traditional wavelength interrogation schemes, a broadband coherent laser generating short optical pulses at a high repetition rate is used along with a highly dispersive optical element. The dispersion causes strong broadening of the optical pulses, and the temporal pulse shape could exactly resemble the spectral distribution of the pulses due to the induced linear chirp. Therefore, by measuring the changes in the pulse shapes with a single high-speed photodetector, the spectral response of the SPR sensor can be obtained for each input pulse and the interrogation speed could reach the repetition rate of the pulse train. This could enable SPR measurements at the speed of tens of MHz or higher, which is well beyond that of other current SPR interrogation techniques. We experimentally demonstrate that, by measuring the variations in the pulse shapes of the chirped pulses, sensitive SPR measurements can be made. Implementing this scheme with a femtosecond fiber laser and other fiber optic components also show the potential to realize more compact and integrated SPR systems.     

Fast surface plasmon resonance imaging sensor using Radon transform

Surface plasmon resonance (SPR) imaging technique is proposed in which a diverging laser beam at given frequency was used to illuminate the entire sensor surface in Kretschmann-Raether configuration. A pattern of dark intensity line on bright background is observed corresponding to the SPR dip at an angular range depending on the refractive index of the adjacent analyte and monitored by a two-dimensional CCD detector. A novel Radon transform based detection algorithm for the SPR line pattern is proposed, which is non sensitive to the laser speckle noise and improves the accuracy.     

A single chip multi-channel surface plasmon resonance imaging system

A single chip, multi-channel surface plasmon resonance (SPR) imaging system has been developed. The equipment has no moving parts and uses a single sensor chip on which multiple channels can be incorporated. A light emitting diode is used as a photon source while a CCD camera forms the detector. The optical configuration has been designed to achieve a uniform illumination of the sample over a fixed area with a range of incident angles. A calibration test using sucrose solutions shows that the sensitivity of the equipment is 4.3×10⁻⁴ refractive index units per pixel line-pair. The use of the system for simultaneous interrogation of different polyelectrolyte thin films, formed by the electrostatic layer-by-layer deposition method, is demonstrated. A reversible pH-dependent response for these organic layers is also reported.     

Dynamically modulated intensity interrogation scheme using waveguide coupled surface plasmon resonance sensors

An electro-optically modulated intensity interrogation method based on tunable waveguide coupled surface plasmon resonance sensors has been proposed. It has been theoretically and experimentally demonstrated that the proposed scheme can enable sensitive measurement of measurand variations. By modulating the refractive index in the waveguide layer, this interrogation method yields modulated signal whose amplitude is related to measurand's refractive index. This amplitude modulated signal offers a higher signal to noise ratio and eliminates additive noise in the sensor system. A preliminary investigation using saline buffers with different NaCl concentrations shows a resolution of 2.3 × 10^?6 refractive index unit by our approach. Resolution can be controlled by the amplitude of the applied modulation voltage and can be further enhanced by optimizing the device structure or improving the electro-optical (E-O) coefficient of the E-O material. This approach is simple, stable, and promising for low-cost or multi-channel SPR biosensor applications.     

表面等离子体共振传感器的仿真

为了得到基于相位检测、角度检测和波长检测的表面等离子体共振(SPR)生物传感器的高检测精度,利用Matlab建立了Kretschmann模型SPR传感器的数值仿真软件.系统地进行了棱镜折射率、测试介质折射率、金膜的厚度等因素对3种不同检测方式的SPR曲线的影响.理论分析结果表明:角度调制时与介质折射率增加时,SPR角也相应增加,相位检测对传感层的折射率具有选择性.     

Development of an integrated CMOS DNA detection biochip

This paper presents a CMOS DNA detection biochip using an electrical detection method with self-assembly multilayer gold nanoparticles (AuNPs). Each measuring spot of this biochip consists of three major parts; a pair of electrodes with a nanogap, a current amplifier circuit, and a heater with an embedded temperature sensor. The biochip is first fabricated by a TSMC (Taiwan Semiconductor Manufacturing Company Ltd.) 0.35 μm 2P4M standard CMOS process. Then, post-CMOS micromachining etch processes are used to expose the surface of the nanogap to test samples for the establishment of multilayer AuNPs through hybridization between single strand DNAs in the samples. The gap distance between a pair of electrodes is 350 nm. Before taking DNA detection measurements, self-assembly monolayer AuNPs is established on the nanogap surface between two microelectrodes. Multilayer AuNPs can be observed if hybridization between single strand DNAs occurs. An approximately 1000-fold increase in electric current between the multilayer AuNPs over the monolayer AuNPs serves an indication of the presence of target DNA in test samples. After integrating the electrodes with an embedded current amplifier, the electric current of multilayer AuNPs is amplified to the order of mA that can be easily measured by a commercial Volt-Ohm-Milliammeter. The heating system with a heating element and a temperature sensor can be used to distinguish single base-pair mismatch hybridization from complementary hybridization for the establishment of multilayer AuNPs. The lowest detectable concentration of target DNA on this biochip is 0.1 nM.     

Sensitivity of surface plasmon resonance sensors based on metallic columnar thin films in the spectral and angular interrogations

Surface Plasmon Resonance (SPR) from metallic Columnar Thin Films (CTFs) of porosity as high as 0.5 was experimentally and theoretically investigated. The CTF layers were prepared by the Glancing Angle Deposition (GLAD) method. The SPR features were investigated in both the angular and the spectral modes. In the angular interrogation, increasing the porosity causes broadening to the dip width, shift to larger resonance angles, and increase of the sensitivity to analyte refractive index (RI) changes by about threefold compared with closed metal films. In the spectral interrogation, on the other hand, the resonance wavelengths are red-shifted for porous films; hence their spectral sensitivities are higher than those of closed films under the same experimental conditions. Nevertheless, the sensitivity behavior versus the resonance wavelength is similar to that of SPR sensors based on dense film layers. The shapes of the nanostructures constituting the CTF are described as ellipsoidal inclusions in which the effective permittivity dyadic of the composite material is calculated using the Bruggeman formalism with exact depolarization dyadics. The correlation between the sensitivity enhancement and the electromagnetic field intensity at the interface between the metallic film and the analyte was examined. Electromagnetic fields analyses were performed using the general 4 × 4 propagation matrices of general homogenous biaxial layers.     

Modeling of surface plasmon resonance nanobiosensor with the transverse resonance method

This article describes a new approach for the detection and identification of a molecular interaction in real‐time and non‐label with surface plasmon resonance (SPR). This approach is based on the transverse resonance method, modeling the nanobiosensor by an equivalent circuit that allows studying the dispersion characteristics of surface plasmon and the reflectivity. The results obtained from these two studies show that the dispersive study is very precise than the reflectivity one to determine the presence and nature of molecular interactions.     

Sensitivity optimization of surface plasmon sensors for detection of intermediate layers

A sensitivity optimization method for the detection of an intermediate layer using a surface plasmon sensor is presented. The dependence of detection sensitivity on distance from the metal surface and the average refractive index over the sensing region are considered. Based on the calculated results, the sensitivity for detecting an intermediate layer in a multilayered sample is determined by varying the refractive index and thickness of each layer. It is shown that, in particular cases, controlling the refractive index and thickness increases the detection sensitivity. The proposed method is useful for designing multilayered samples.     

Absorption-based fiber optic surface plasmon resonance sensor: a theoretical evaluation

In this paper, an optical absorption based fiber optic surface plasmon resonance (SPR) sensor has been studied theoretically. The theoretical treatment is based on Kretschmann’s SPR theory and the Lorentz model that expresses a damped harmonic oscillator is included in the treatment for optical absorption in the sensing layer. The optical source considered is an un-polarized collimated beam. The light is coupled to the fiber using a microscope objective that focuses the beam at the center of the input face of the fiber. The effects of the parameters related to the sensing region, the light source and the optical fiber on the sensitivity and the operating range of the SPR sensor have been studied with the help of numerical calculations and computer simulations. It has been found that the excitation frequency in absorption-based fiber optic SPR sensor is an important parameter. The sensitivity is better for the lower off-resonance excitation frequency. The sensitivity and the operating range of the sensor are better for large value of the core diameter. The optimization of numerical aperture of the fiber, film thickness and the length of the sensing region is required to achieve the maximum sensitivity. Further, the increase in the extinction coefficient of the sample increases the sensitivity of the sensor while the decrease in the width of its absorption spectrum increases the sensitivity. The sensitivity and the operating range of the sensor are better for small values of the refractive index of the absorbing sample.     

表面等离子共振生物传感器检测磺胺类药物残留

利用表面等离子共振光学生物免疫传感器,在金膜芯片表面固定抗原技术,实现了磺胺二甲嘧啶药物的定量检测.介绍了抗原分子膜的生长方法,当配置样品中磺胺二甲嘧啶浓度分别为0,1.2,2.4,8,11.5 mg/L,与工作浓度的抗体混合,测量了传感的信号强度值,得到抑制标准曲线.在无抗牛奶中添加系列质量浓度的磺胺二甲嘧啶样品,利用免疫竞争抑制原理构建标准曲线,检测的浓度线性范围为3～48 mg/L,对浓度为40mg/L的样品,检测的相对标准偏差小于10％,回收率为99％.检测结果表明:基于表面等离子共振的光学生物免疫传感器在磺胺二甲嘧啶药物残留方面具有很好的应用前景.     

Use of a low refractive index prism in surface plasmon resonance biosensing

A way to improve the angular sensitivity of surface plasmon resonance (SPR) biosensor by tuning the resonance position to a higher incident angle region using a lower refractive index glass prism is described in this paper. A novel effective 3-layer (E3L) model is described to transform a multiple layer biosensor configuration in context of SPR condition. The E3L model supports the use of a low refractive index prism for biosensing. The performance of the sensor in immunosensing is checked for two glass prisms of different refractive index materials. The experimental results showed an enhancement in the amount of resonance angle shift of the immunosensor for the lower refractive index glass prism.     

Investigations of prussian blue films using surface plasmon resonance

A fiber-optic based surface plasmon resonance (SPR) instrument is used to characterize electrodeposited prussian blue (PB) films. PB films are deposited potentiostatically or galvanostatically onto the gold sensing surface. When reduced to prussian white (PW), the film undergoes a reversible refractive index change that is observed using SPR. The strong absorbance of PB films within the sensing region of the instrument inhibits quantitative characterization of these films; however qualitative characterization has been achieved. The PB coated SPR probe can be used as an optical transducer of electrochemical phenomena. A PB film is deposited on the gold SPR sensing surface; the probe is submerged in 0.1 M KNO₃ in a tube terminated with a porous vycor frit. The isolated PB half-cell and a AgCl-coated Ag wire are placed in a beaker containing 0.1 M KNO₃ and connected by a variable battery. Addition of chloride to the bulk solution changes the potential of the AgCl wire, which induces a change in the PB film that can be observed using SPR. A change in chloride concentration of 40 μM can be detected using this system.     

基于SAW表面气液相效应和GC分离柱的气敏传感器的研究

限于传统涂敷敏感膜的声表面波（SAW）气敏传感器存在成膜困难和选择性差、重复性差以及再生性差等问题，本研究提出一种基于压电基底表面气体气液相转换效应机理的瑞利波传感器。首先建立了挥发性有机气体(VOCs)液相凝聚体薄层负载下的SAW波传模型，并仿真计算了其波传频散和波传衰减。然后在此基础上开发了一种基于瑞利声表面波传感器和气相色谱（GC）分离柱的便携式气体检测系统。最后实验论证了方案的可行性，初步的实验结果表明该系统具有分析时间短、选择性好、灵敏度高（可检测ppb浓度的混合VOCs）以及成本低等优势，因此其在痕量挥发性有机气体检测和分析应用上有良好的潜力和前景。     

声表面波传感器的原理及应用综述

详细论述了声表面波传感器的工作模式、工作原理;结合目前声表面波传感器的发展状况,详细论述了声表面波在智能变电站、电力设备、列车、湿度检测以及在复杂多变环境中的应用;对声表面波传感器的发展给出了展望.