Detection of unlabeled particles in the low micrometer size range using light scattering and hydrodynamic 3D focusing in a microfluidic system

In this paper, we describe a microfluidic device composed of integrated microoptical elements and a two-layer microchannel structure for highly sensitive light scattering detection of micro/submicrometer-sized particles. In the two-layer microfluidic system, a sample flow stream is first constrained in the out-of-plane direction into a narrow sheet, and then focused in-plane into a small core region, obtaining on-chip three-dimensional (3D) hydrodynamic focusing. All the microoptical elements, including waveguides, microlens, and fiber-to-waveguide couplers, and the in-plane focusing channels are fabricated in one SU-8 layer by standard photolithography. The channels for out-of-plane focusing are made in a polydimethylsiloxane (PDMS) layer by a single cast using a SU-8 master. Numerical and experimental results indicate that the device can realize 3D hydrodynamic focusing reliably over a wide range of Reynolds numbers (0.5 < Re < 20). Polystyrene particles of three sizes (2, 1, and 0.5 μm) were measured in the microfluidic device with integrated optics, demonstrating the feasibility of this approach to detect particles in the low micrometer size range by light scattering detection.     

光散射法快速灵敏测定和表征啤酒酵母

研究了啤酒酵母的光散射光谱. 结果表明， 在波长308.0 nm处, 光散射强度与啤酒酵母浓度在2.0×104-2.0×106 Cell/mL 范围内呈线性关系, 检出限(3σ)为4.94×102 Cell/mL. 将此方法成功地应用于培养液中啤酒酵母含量的快速、 灵敏的测定, 并对其散射光谱进行了表征.     

分形表面粗糙度与光散射关系的研究

用Weielstxass－Mandelbrot函数产生了一维的分形表面，在几何光学适用的范围内研究了这些表面的光散射特性．发现分形线数D越大，通常被认为越粗糙的表面，其光散射的角分布反而比D小的表面更集中．文章最后解释了这种现象的成因．     

The size and shape of silica particles

Negatively charged silica particles were investigated at pH 10.0. They were found to be rod-shaped (cylinder) with a diameter of 5–5.5 nm and a full length of 44–67 nm depending on the rod model used. Moreover, the particles were found to be stable against aggregation in the region 0.4–50 mM NaCl. Received: 2 December 1998 Accepted in revised form: 2 February 1999     

Direct Measurement of Electron Beam Scattering in the Low Vacuum SEM

The beam-gas interactions in the low-vacuum SEM is investigated through experimental and simulation approaches. An original experimental way to characterise the skirting is proposed. We obtained directly image distribution of the primary electron beam and the scattered electrons in the low-vacuum SEM. The experimental results are compared to the electron beam profile obtained with Monte-Carlo simulation.     

Absorption of scattered light in colloidal systems of aggregated particles

Scattering and extinction of colloidal systems containing either nonabsorbing or strongly absorbing spherical particles of some nanometers in diameter were examined in the wavelength range from the near UV to the near IR. If aggregation occurs, scattering and extinction are modified with respect to the single sphere systems. The influence of aggregation can best be recognized for absorbing particles when already the single sphere shows resonant extinction. In this case, the resonance of the single sphere splits into many new resonances for the aggregate, most of which are positioned at larger wavelengths than the single sphere resonance. They strongly depend on the size and shape of the aggregate.Looking at the scattering, additional problems arise in systems of absorbing particles caused by reabsorption by neighboring spheres or aggregates. A simple model was developed to interpret the obtained scattering data.     

人血清蛋白-丙酮(乙醇)体系的荧光光谱及共振散射光谱特性

人血清蛋白-丙酮(乙醇)体系的荧光光谱及共振散射光谱特性     

分光光度法与激光热透镜光谱分析法测定高散射物质光吸收的比较

通过理论和实验比较了分光光度法与激光热透镜光谱分析法在高散射背景下测量物质光吸收的差异。研究了在不同含量纳米TiO2的散射背景下，散射对分光光度法和热透镜光谱分析法测定耐尔蓝溶液含量的影响。结果表明，分光光度法对具有光散射性质试样的测定存在较大误差，而激光热透镜光谱分析法能较好的避免散射影响，测定结果准确。实验结果与理论分析相一致。     

Formation of Vesicles and Micelles in Aqueous Systems of Tetrameric Acids as Determined by Dynamic Light Scattering

A comprehensive dynamic light scattering (DLS) study on the system BP10Na₄/water is presented. BP 10Na₄ is a tetrameric fatty acid in sodium form. In order to change molecular packing conditions both electrolyte (NaCl) and alcohol (1-butanol, 1-pentanol) are added to the surfactant system. Phase diagrams of the systems reveal not only an extensive micellization, but also the occurrence of a lamellar liquid crystalline D phase. The DLS study shows an existence of vesicles at very dilute BP10Na₄ concentrations ( ?cmc) and also a co-existence of micelles and vesicles at higher BP10Na₄ concentrations. Cryo-TEM pictures verify the existence of the vesicles. Based on the DLS and SLS experiments the weight-average molar mass of the micelles are estimated to be 13500 g/mol at 100 mM NaCl and 22700 g/mol at 600 mM. The corresponding aggregation numbers are 13 and 22, respectively.     

Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.     

光散射技术在高分子表征研究中的应用

光散射技术是高分子领域中重要的表征手段之一.静态光散射和动态光散射的结合能够获得丰富的关于高分子的信息,如重均分子量、回转半径、第二维里系数、流体力学半径、尺寸分布、分子链构象等.除合成高分子外,光散射技术同样适用于研究生物大分子、微生物、胶体、纳米粒子、病毒、囊泡等在溶液或悬浮液中的行为.本综述重点介绍稀溶液中静态光...     

曙红Y的共振光散射与共振荧光

研究了曙红Y（EY）的共振散射光谱、荧光光谱和吸收光谱,讨论了共振光散射与共振荧光的区别与联系。在EY水溶液三维荧光等高线光谱图中,瑞利散射线与荧光等高线有部分相交。EY的共振散射峰（525nm）介于荧光激发峰（514nm）和发射峰（536nm）之间。由光偏振实验,测得EY共振散射光谱525nm处的偏振度P=0．20。上述实验结果证明,EY的共振散射峰主要是共振荧光。在改变pH的实验中发现,EY共振光散射增强是由于酸碱平衡的移动导致荧光型体的形成。由于自吸收的影响,共振散射光强度与EY浓度之间不是严格的线性关系。     

Computer simulation of the shape of absorption bands in electronic spectra ofJ-aggregates

The shape of absorption bands of aggregates formed by two, four, and nine molecules of a polymethine dye was calculated by the Monte-Carlo method. The energy of interaction of the molecules in the ground state was simulated using atom-atom potentials, and the energies of interaction between dipole moments of electronic transitions of the monomers were estimated by quantum-chemical methods. In the dimer aggregate the dipole moments of the electronic transitions in the monomers interact weakly; therefore, the electron absorption spectrum should be similar to that of the monomer. On going from the dimer to the aggregates consisting of four and nine monomers, the relative positions of monomers change and this, in turn, increases the energy of interaction between the dipole moments of their electronic transitions, resulting in a red shift characteristic ofJ-aggregates and narrowing of the absorption bands. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya. No. 1, pp. 67–69, January, 1997.     

氟喹诺酮类抗生素与磷钨酸体系的共振瑞利散射光谱研究及其分析应用

在5.0 mol/L的HCl缓冲介质中,磷钨酸（Pwa）与莫西沙星(MXFX)和加替沙星（GTF）等氟喹诺酮类抗生素(FLQs)相互作用形成摩尔比1∶1离子缔合物,导致体系的共振瑞利散射(RRS)显著增强并出现新的RRS光谱。 MXFX和GTF的反应产物具有相似的光谱特征,最大散射波长位于320 nm附近,且药物浓度与散射增强(ΔI)成正比,2种氟喹诺酮类药物的线性范围分别为0.025~6.0 mg/L（MXFX）和0.023~9.0 mg/L（GTF）。 据此可建立用于测定氟喹诺酮类药物的简捷快速灵敏的新方法,方法用于胶囊和人尿液中的FLQs测定并取得满意结果。 并对反应机理和RRS增强的原因进行了讨论。     

Monte Carlo Simulation of Electron Transport and X-Ray Generation. I. Electron Elastic and Inelastic Scattering

We present different theoretical approaches to determine differential cross sections for elastic and inelastic interactions of electrons. These cross sections are the basic ingredients for accurate Monte Carlo simulation of electron transport in matter. The considered models range from simple analytical approximations employed in early calculations to purely numerical differential cross sections described by large databases calculated with state-of-the-art theory.     

Synthesis,characterization and cd spectra studies of chiral calixsalen complexes

A chiral macrocyclic Schiff base ligand and its binuclear metal complexes of Fe, Co, Ni and Cu were synthesized by a modified method with 1,2‐diaminocyclobexane as the starting material, which is readily obtained. The characters of those complexes were studied by elemental analyses, MS, NMR, FT‐IR, UV‐Vis and CD (Circular Dichroism) spectra. Furthermore, the electronic absorption spectra and CD spectra properties of the chiral complexes were discussed.     

Predictive control and verification of conversion kinetics and polymer molecular weight in semi-batch free radical homopolymer reactions

Polymer molar mass distributions critically affect macroscopic characteristics and performance of polymeric materials. While multi-detector methods coupled to size exclusion chromatography (SEC) are widely used to measure endproduct mass distributions, less progress has been made in simultaneously controlling and verifying the evolution of these distributions during synthesis. This work focuses on quantitative predictions and online verification of conversion kinetics and of molecular weight during free radical homopolymerization of acrylamide, where reagents were fed into the reactor during the reaction. The central task is to establish and experimentally test a formalism combining free radical polymerization kinetics with time dependent processes related to flows of material into and out of the reactor. Monomer feed experiments were performed that alternately hold molecular weight constant and ramp the weight up, in contrast to batch reactions, where molecular weight decreases. Three types of initiator feed ‘tapers’ were also used to produce predictable conversion kinetics and mass distributions: (i) constant initiator feed, (ii) linearly stepped feed to produce Gaussian conversion kinetics, and (iii) booster shots to produce multi-modal masses. Automatic Continuous Online Monitoring of Polymerization reactions (ACOMP) was used to follow the conversion and evolution of the average mass distribution, and multi-detector SEC was used to cross-check results and measure full distributions of endproducts. In general, there was good agreement between the predictions and results. In future work this approach can be used as an Ansatz for reaction trajectory prediction, and the online monitoring signals exploited to make feedback controlled corrections to the reagent flows and other reaction conditions.     

Monte Carlo simulations and analysis of scattering from neutral and polyelectrolyte polymer and polymer-like systems

Methods for analyzing small-angle scattering data from complex liquids with particles with many internal degrees of freedom have progressed substantially during the past years. This is mainly due to the use of Monte Carlo simulation techniques for obtaining scattering functions and the use of an approach in which the obtained scattering functions are subsequently parameterized, so that they can be used for data fitting. The present paper reviews recent applications of the Monte Carlo technique for obtaining parameterized scattering functions, and the application of these with emphasis on semiflexible polymers and wormlike micelle systems with and without electrostatic interactions.     

Raman scattering spectra and molecular conformations of bis(quaternaryammonium bromide)-water systems

The dimeric bis(quaternaryammonium bromide) surfactants, [Br⁻(CH₃)₂N⁺(C _m H_{2 m +1})—(CH₂) _s —(C _m H_{2 m +1})N⁺(CH₃)₂Br⁻, s = 2, 3 and m = 4, 6, 10 and 12, s = 6 and m = 8, 10, 12], have been synthesized and the phase maps of the sm6-8-water, sm6-10-water and sm6-12-water binary systems have been determined (sm6-8 implies s = 6, m = 8). In order to examine the molecular structures of these solid samples and of their dimeric surfactant-water binary systems, Raman spectra of the simple dimeric surfactants, sm2-4 and sm3-4, in which crystal structures of the trans- and cis-type conformations have been determined by single-crystal X-ray diffraction analysis, have been investigated, and Raman bands characteristic of these skeletal structures were found in the skeletal deformation region. On the basis of these characteristic Raman bands for the two conformations, it has been concluded that the dimeric surfactants, sm6-8, sm6-10 and sm6-12 also take up a cis-type conformation in the crystalline state. Furthermore, it has been found that the Raman bands in the C—H stretching, skeletal stretching and CH₂ scissoring regions are sensitive to phase structure. Received: 21 July 1998 Accepted in revised form: 9 November 1998     

Solvatochromic effects in the absorption and fluorescence spectra of indazole and its amino derivatives

Absorption and fluorescence spectra of Indazole (In) in five solvents and those of 5-amino, 6-amino, and 7-aminoindazoles (5-AI 6-AI, 7-Al) in thirteen solvents have been studied. Using the multiparametric approach of Taft et al., spectral characteristics of these molecules have been analysed on the basis of electrostatic effects, hydrogen bond donor ability and hydrogen bond accepting ability of the solvents. In the excited singlet state, all three effects are nearly equally prominent, whereas in the ground state 5-AI acts as a better hydrogen bond acceptor than the other amines. Stokes shifts and the difference between the radiative decay constants determined experimentally and using Strickler and Berg's equation indicate different geometries of the amines in the S₀ and S₁ states. A decrease in the non-radiative decay constants of 5-AI and 6-AI with an increase in the polarity of the solvents predict better planar geometry in the S₁ state in comparison to that in the S₀ state. Semi-empirical quantum mechanical calculations have been used to find the nature of transitions, total atomic charges at the basic centres and dipole moments of all the aromatic amines in the S₀ and S₁ states. Results so obtained are compared and discussed.