Biosensors using integrated optical devices

Summary A label-free, homogeneous immunoassay can be realised using surface single-mode wave guide structures. The evanescent field of the guided mode penetrates the adjacent vicinity of the wave guide, the biochemical layer. Thus, changes in its thickness and refractive index during an antigen-antibody interaction cause a change in the effective refractive index of the wave guide itself. Such small changes can be transformed into intensity modulations using an interferometric set-up. Investigations are described using an integrated optical Mach-Zehnder interferometer (IO-MZ-chip) and the experimental results are compared with model calculations. The theoretical sensitivity of the IO-MZ-chips used was determined applying Maxwell's equations to the propagation of light in stripe wave guides. For the experimental formation of a protein adlayer a three-step biotinavidin protocol for the immobilisation of biotinylated immunoglobulins was employed.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

High Photosensitive Sol-Gel Hybrid Materials for Direct Photo-Imprinting of Micro-Optics

Sol-gel derived inorganic-organic hybrid materials (HYBRIMERs) were found to have high photosensitivity arising from large changes in refractive index and volume upon exposure to light. These materials combined different photosensitive mechanisms due to the presence of polymers and silica in the HYBRIMER structure. Photo-induced densification of a germanium-doped HYBRIMER gave an increase in refractive index accompanying a volume contraction. A methacrylate HYBRIMER was decomposed by long UV illumination, giving a low refractive index and resulting in a reduction in film thickness. Also, photo-initiators were locked inside the methacrylate HYBRIMER during illumination, giving a simultaneous increase in the refractive index and film thickness. Direct photo-imprinting using the photosensitive HYBRIMER was demonstrated for simple fabrication of gratings, microlens, and waveguides using a photomask, a phase mask, an interferometer, and laser writing.     

一些液相色谱文献中反射式折光检测器基本方程的错误

指出了一些液相色谱文献中对反射式折光检测器基本方程的错误表示,并推导出了正确公式。     

Fibre optic coupler as a detector for microfluidic applications

A new construction of a fibre optic coupler is presented in the paper. Two polymer optical fibres were used to build a coupler in which coupling efficiency of optical power depends on the refractive index of liquid delivered to a microchannel formed by the fibres. The coupler was tested as a detector in saccharose concentration measurements, and was used in absorbance measurements. A red light emitting diode and a spectrometer were used as a light source and a photodetector, respectively. Experiments confirmed that the coupler can be used for the real time monitoring of the changes in the refractive index of a saccharose solution exhibiting repeatable changes in the signal, with no hysteresis. Absorbance tests were performed with a solution of bromothymol blue at different pH.     

Composition determination of binary polymer mixtures by size exclusion chromatography with light scattering detection

<正>Base on the principle of absolute quantification of size exclusion chromatography(SEC),a light scattering(LS) detector coupled with a concentration detector(refractive index detector) is utilized to determine the compositions of complicated binary mixtures.A theoretical analysis predicts that the response factors for both LS and RI detectors are linear functions with the composition of any specified polymer mixtures in the binary polymer mixtures.Two pairs of complicated binary mixtures were used to test the theory mentioned in the present paper,and the experimental results show an excellent accordance with the theory.     

Microbore liquid chromatography and refractive index gradient detection of low-nanogram and low-ppm quantities of carbohydrates

A refractive index gradient detector is presented as a universal detector in the microbore high-performance liquid chromatography analysis of carbohydrates. Simultaneously, low-ng and low-ppm injected quantities of carbohydrates were detected at the 3 x root-mean-square baseline noise level. A typical microbore high-performance liquid chromatography chromatogram separating fructose from sucrose followed by refractive index gradient (RIG) detection is reported. Use of a position sensitive detector (PSD) in the RIG detector design is reported and experimental considerations discussed. Optimization of the PSD-based RIG detector is addressed. Potential for the device in industrial and clinical applications is considered.     

利用凝胶渗透色谱示差-紫外检测器联用测定丁苯共聚物的组成分布

将凝胶渗透色谱(GPC)中的示差与紫外检测器联用,测定了无规共聚丁苯橡胶和SBS三元嵌段共聚物中各级分的组成变化.实验方法选择中对比了两种浓度参数的确定方法,发现通过改变注射量来实现浓度变化的方法优于使用系列浓度样品的方法.分别测定标准样品在紫外和示差检测器上信号产生的时间间隔可以确定两个检测器上信号的时间差.根据紫外-示差检测器联用可以看到SBR无规共聚物和三嵌段SBS共聚物样品中每一个级分中随着相对分子质量的变化,苯乙烯含量的变化.     

折射＼率对流动注射峰形影响的研究

本文利用折射定律、菲涅耳公式和流体力学原理研究不同浓度乙醇溶液为试剂或载流的单流路体系中，正向流动注射与反向流动注射的信号峰形，对每个正、负峰高度和位置进行解释。给出不同相界面曲面方程，计算不同条件下反射率，反射光和折射光被流通池壁吸收时的径向半径及发生全反射时的径向半径，从理论上计算各种条件下的吸光度。     

Specific Refractive Index Increment Measurements on Macromolecules Using a Waters R401 Differential Refractometer

Abstract

An accurate and simple method for determining the specific refractive index increment, dn/dc, of synthetic polymers during size-exclusion chromatography has been developed using a modified Waters R401 differential refractive index (DRI) detector. The only modification required on the R401 involved the replacement of the standard white light source with a monochromatic source. The use of this instrument offers a number of advantages over more classical instruments and procedures normally employed in evaluating this parameter. The only requirement which must be met in order to successfully measure this parameter is the conservation of mass (in terms of the amount of polymer injected on to the columm and which passes through the DRI detector). However, in some cases, even this requirement may be relaxed. The application of this procedure will be demonstrated for several synthetic polymers in mixed and single solvent systems.     

Controlling the evolution of polypropylene microstructure during melt free radical modification using zinc dithiocarbamate with different N-substituted groups

The effects of zinc dithiocarbamates on degradation and branching of polypropylene (PP) were studied during melt radical modification using a tri-functional monomer (trimethylol propane triacrylate (TMPTA)). High-temperature size-exclusion chromatography (HT-SEC) coupled with differential refractive index detector (DRI), light scattering detector (LSD) and viscometer detector (VD) and rotational rheometry were used to analyse the microstructure of modified PP samples. The chemical structure of the N-substituted group showed an important influence in controlling the evolution of PP microstructure during melt radical reaction. The chain cleavage of PP was controlled in the presence of zinc N, N-dimethyldithiocarbamate (ZDMC), and a substantial long chain branched (LCB) fraction was formed. Without co-agent, the molecular weight of PP decreased measurably, and only a minor LCB fraction was formed. Importantly, considerable amounts of highly branched (microgel and hyperbranched) structures were formed in this case.     

Investigations of the optical properties of thin, highly absorbing films under attenuated total reflection conditions: Leaky waveguide mode distortions

Spectra of thin highly absorbing Nafion films doped with Ru(bpy)₃²⁺ on SF11 glass substrates were studied by internal reflection spectroscopy using a single reflection configuration. For the system under study, two modes of light interaction with the film are available: attenuation due to evanescent wave penetration and light propagation within the absorbing film. Unlike evanescent wave spectroscopy, light propagation within the film causes distortions in the measured spectra due to leaky waveguide propagation modes. Upon light propagation in a film doped with Ru(bpy)₃²⁺ spectral shifts up to 50 nm to longer wavelengths can occur and additional absorbance peaks can appear in the spectra. These film-based distortions depend on the complex refractive index, the thickness of the film and the angle of incidence. These effects become significant for an extinction coefficient above 0.01 and a film thickness above 200 nm. It is shown that spectral distortions can lead to quite complex dynamics in the internal reflection spectra upon analyte preconcentration in the film. Ru(bpy)₃²⁺ partitioning into the Nafion film causes significant refractive index changes that in turn alter leaky waveguide mode conditions in the film and, can even lead to a reduction of measured absorbance despite the increase in the extinction coefficient of the film.     

Polyelectrolyte/magnetite nanoparticle multilayers: preparation and structure characterization

Polyelectrolyte composite planar films containing a different number of iron oxide (Fe3O4) nanoparticle layers have been prepared using the layer-by-layer adsorption technique. The nanocomposite assemblies were characterized by ellipsometry, UV-vis spectroscopy, and AFM. Linear growth of the multilayer thickness with the increase of the layer number, N, up to 12 reflects an extensive character of this parameter in this range. A more complicated behavior of the refractive index is caused by changes in the multilayer structure, especially for the thicker nanocomposites. A quantitative analysis of the nanocomposite structure is provided comparing a classical and a modified effective medium approach taking into account the influence of light absorption by the Fe3O4 nanoparticles on the complex refractive index of the nanocomposite and contributions of all components to film thickness. Dominant influence of co-adsorbed water on their properties was found to be another interesting peculiarity of the nanocomposite film. This effect, as well as possible film property modulation by light, is discussed.     

Design of new integrated optical substrates for immuno-analytical applications

Integrated optical Mach-Zehnder interferometers supply information on changes in refractive index and/or thickness of a film placed as a superstrate on top of one of its surface wave-guides. The internal propagation of light is influenced by the evanescent field reaching into the superstrate. This propagating light interferes with an uninfluenced wave in the second arm after recombination. The result is an intensity modulation depending on the refractive index parameters of the substrate, the waveguide itself and the properties of the superstrate. Taking an antigen layer as the superstrate, its interaction with antibodies changes its thickness by several nanometers. This can be observed by recording the change in intensity of the signal of the interferometer. The sensitivity of such a device depends on particular values of the optical parameters of substrate and waveguide with respect to the given superstrate properties. Computer calculations help to select optimum glass and waveguide fabrication conditions. The numerical results of a variety of assumed conditions have been tested experimentally. The application to the improved detection of triazines is discussed.     

A black beam borne by an incandescent field self-traps in a photopolymerizing medium

We report that a self-trapped black optical beam that is spatially and temporally incoherent forms spontaneously in a nascent photopolymerization system. The black beam inscribes a permanent cylindrical channel, which prevents the propagation of visible light even under passive conditions (in the absence of polymerization). The finding opens a powerful new mechanism to manipulate light signals from incoherent sources such as LEDs through selective suppression of light propagation. This contrasts with approaches employed by photonic crystals and optical waveguides, which concentrate and guide light intensity within spatially localized regions. The self-trapped black beam forms when a broad incandescent beam bearing a negligible depression was launched into a photopolymerizable medium. Because of refractive index changes caused by polymerization, the depression narrows, deepens, and continually rejects the visible spectrum of light until it stabilizes as a black beam that propagates over long distances (? effective Rayleigh range) without significant divergence. As refractive index changes due to polymerization are irreversible, the cylindrical region occupied by the self-trapped black beam is inscribed as a black channel waveguide in the medium.     

Studies of orientation and structure of crazed matter in polystyrene. I. Optical measurements

The optical birefringence and refractive index have been measured for crazes grown in specimens of varying thickness. The birefringence was found to consist of the sum of a small negative orientation term and a large positive form term. The latter term could be altered by filling the craze with liquids of various different refractive indexes. Two crazes, which showed a relatively constant width as the specimen thickness changed, could be described by a model with craze having a constant refractive index and birefringence but with impervious dense skins on either side. The numerical value of the form birefringence was approximately 0.6 of that predicted from a model of parallel rods which is not surprising as crazes have a networklike structure. The values of craze refractive index were in good agreement with other measurements. The existence of skins, of thickness approximately 300 nm, places some doubt on the relevance of thin-film electron microscope observations to the situation in the bulk. Other crazes which tapered in width were found to show both varying skin thickness and refractive index along their length.     

Quantitative characterization of the optical properties of absorbing polymer films: Comparative investigation of the internal reflection intensity analysis method

Nondestructive, three‐dimensional refractive‐index measurements are used for the determination of both the crystallinity and orientation in thin polymer films. The prism wave‐guide coupler is particularly suited for three‐dimensional isotropic and anisotropic thin‐film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to determining only the refractive index of transparent or weakly absorbing thin‐film samples. On the basis of thin‐film optics, this study develops a new internal reflection intensity analysis (IRIA) method, which uses the intensity information rather than the conventional mode angle values to acquire both the refractive index and the extinction coefficient over a range of transparent to highly absorbing polymer films. Therefore, the IRIA method overcomes the limitations of this prism wave‐guide coupler technique, which can only measure the refractive index of a weakly absorbing sample. With a Metricon PC‐2010 as the skeletal framework, a prototype instrument has been developed to apply and test the IRIA method. A study comparing both the refractive index and extinction coefficient obtained with ellipsometry, ultraviolet–visible/near‐infrared reflectometry, and IRIA for solvent blue 59 dyed polystyrene films confirms that the IRIA method is effective for obtaining the three‐dimensional refractive indices and extinction coefficients of polymer films. In addition, the refractive index and extinction coefficient spectrum (400–800 nm) of solvent blue 59 have been determined with the effective media theory. Furthermore, the three‐dimensional complex refractive indices of highly absorbing black electrical tape, inaccessible to other optical measurement because of its surface character, has been determined by the IRIA method. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 842–855, 2003     

二元复杂共混体系组成的SEC-LS分析

提供了一种利用体积排阻色谱-光散射(SEC-LS)联用技术来解决二元复杂共混体系组成的定量分析问题.基于体积排除色谱的绝对定量化原则,首先从理论上分析了共混物的光散射响应因子与组成呈线性关系.通过分析六组复杂共混体系的光散射响应因子与组成的关系,验证了该线性关系确实存在.进而利用该线性关系计算了共混体系的组成.在某些共混体系中,通过光散射响应因子得出的组成比利用示差法得出的组成更加接近原料组成.通过分析这两种方法产生误差的来源,阐述了产生该现象的原因.     

光漂白全过程中聚合物薄膜折射率和厚度的实时分析

在基于衰减全反射原理的基础上提出一种新的测量方法, 动态研究漂白动力学过程, 即利用波导的衰减全反射吸收峰对聚合物材料的折射率和厚度敏感的特性, 实时测量聚合物材料的折射率和厚度. 实验系统采用CCD摄像头将标志波导模式的一组暗线显示在计算机屏幕上, 然后根据暗线的移动, 可以精确测量每一时刻波导薄膜的折射率和膜厚. 利用这种技术, 对聚合物薄膜的光漂白过程进行了实时监控. 发现在光漂白全过程中, 聚合物薄膜的折射率和厚度的变化同时存在化学和物理两种变化过程.     

Determination of water by flow injection analysis with the karl fischer reagent: Minization of effects caused by differences in physical properties of the samples

In the previously described flow-injection method for the spectrophotometric determination of water with the Karl Fischer reagent, problems can arise from the rather large variation between the calibration curves for different types of samples. Different combinations of flow-injection arrangements and detector types are described here, to establish a system which levels out this undesirable spreading between the calibration curves. One necessary condition for attaining a low spread is shown to be the use of a spectrophotometric detector especially constructed to minimize refractive index effects. The best results, including samples with large differences in refractive indices and viscosities, were obtained by a combination of peak area measurements and the use of this detector. For example, the relative mean deviation for a sample containing 0.1% water was about 2%.