检测溶液中单分子

科学的进步不但要求对物质的整体特征进行鉴定和测定，同时还要求对单分子化学和物理性质进行深入探索。在单分子水平对物质进行研究，是一项重要的学科前沿交叉领域，对分子工程学、分子生物学、分子医学、纳米材料和信息科学具有非常重要的意义。本文评述近年来溶液中单分子检测研究的最新进展，包括激光诱导荧光检测、电化学检测及我们最近提出的化学发光检测等。并对这一学科前沿领域进行了展望。     

激光双光子电离方法对水溶液表面的蒽及其衍生物的测定

激光双光子电离方法用水溶液表面的蒽及其衍生物分子的检测，Ｎｄ－ＹＡＧ激光的第三谐波３５５ｍ用作激发和电离。光电离电荷数在－３个数量级内随浓度呈线性关系。     

单波长荧光交叉相关光谱单分子检测系统

基于激光共焦构型建立了一套单波长荧光交叉相关光谱检测系统, 并对检测系统进行了优化, 阐述了荧光交叉(相关)光谱基本理论. 以荧光量子点和有机染料为标记探针, 以人免疫球蛋白与羊抗人免疫球蛋白的结合反应为研究对象, 利用该系统成功地实现了在单分子水平上对免疫结合产物的分子数、浓度、特征扩散时间和动力学半径等参数的表征.     

荧光相关光谱单分子检测系统的研究

基于激光共焦构型,构建了一套高灵敏度和高稳定性的荧光相关光谱单分子检测系统。采用高数值孔径物镜使激光束高度聚焦,并用同一物镜收集样品的荧光,单光子计数器用于实时记录荧光信号。优化系统保持物镜焦点、针孔以及单光子计数器光敏区高度同轴。采用60×1.2(NA)的水浸物镜及直径为160μm的针孔得到的检测系统结构参数为ω0和z0分别为0.42μm和1.33μm,照射微区的体积为1.3fL。单个RhodamineGreen分子可获得13倍的信噪比。用该系统获得了小分子和生物大分子(DNA片段和蛋白质)的高质量荧光相关图谱,成功实现了单个分子的检测。     

超痕量分析中的激光诱导荧光检测

本文对激光诱导荧光检测器(LIF-D)及其主要器件激光器、滤光片、透镜、光电检测器、荧光探针及扫描装置的现状和发展趋势作了综述,介绍了LIF在单分子检测中的应用.     

激光诱导荧光光谱分析进展

本文对激光诱导荧光光谱分析的研究现状和发展趋势进行了综述。着重介绍了激光诱导原子荧光光谱、激光诱导分子荧光光谱、激光低温光谱,时间分辨光谱和激光诱导荧光光谱与其它分析技术的联用研究。     

微柱分离中的激光诱导荧光检测

 激光诱导荧光检测 (LIFD)以其高的灵敏度和选择性而被广泛应用于微柱分离技术中。以检测池为轴线 ,概述了激光诱导荧光检测系统新进展及其应用。引用了 5 2篇文献     

266nm激光激励的SO2（X^1A,A^1A2,B^1B1）体系的态间转移研究

用ＹＡＧ四马ＳＯ２分子从电子基态Ｘ＾１Ａ１激励到电子激发态Ａ＾１Ａ格Ｂ＾１Ｂ１的高振动耦合区，获得了３２０－３８０ｎｍ范围内ＳＯ２（Ｂ＾１Ｂ１→Ｘ＾１Ａ１１）的激光诱导荧光色散谱，并给出初步标识：提出一个三能太模型来处理２６６ｎｍ激光激励的ＳＯ２（Ｘ＾１Ａ１，Ａ＾１Ａ２，Ｂ＾１Ｂ１）体系的态间转移，并获得了Ａ态和Ｂ 高振动能区的耦合系数ζ及耦合达到动态平衡的弛豫时间τ，发现二者反映的是被研究体系的     

荧光标记聚苯乙烯微球的激光捕获及其原位稳态和时间分辨荧光光谱研究

本工作设计研制了一套激光捕获与原位稳态及时间分辨荧光光谱检测系统,该系统将激光捕获技术与稳态及时间分辨荧光光谱检测技术相结合,实现了对亚微米级微粒的原位稳态及时间分辨发光性质研究.利用研制的仪器研究了荧光标记聚苯乙烯微球的激光捕获过程、以及捕获微粒的原位稳态及时间分辨荧光光谱.本工作为单个纳米粒子发光性质的研究开辟了一条新的途径.     

由激光诱导荧光确定对称陀螺分子定向和取向的理论研究

采用密度矩阵方法推导了从激光诱导荧光强度中抽出对称陀螺分子定向和取向参数的一般表达式. 分子定向和取向由分子态多极矩描述. 激发激光和探测荧光分别为圆偏振和线偏振光. 在一般情况下, 激光诱导荧光强度是初始分子态多极矩、动力学因子和激发-探测几何因子的复杂函数. 它包含一个布居(population)、10个定向(orientation)和14个取向(alignment)态多极矩. 讨论了如何从分辨荧光强度中抽出所有初始分子态多极矩问题.     

An ultrafast time-resolved fluorescence spectroscopy system for metal ion complexation studies with organic ligands

A dedicated spectrofluorimeter using ultrashort laser pulses as an excitation source was developed to measure the fluorescence properties of organic ligands for metal ion complexation with organic ligands. The laser system consists of an oscillator system for generation of femtosecond laser pulses, an amplifier system to increase the pulse energy of the generated pulses to about 2 mJ and an optical parametrical amplifier system to provide tunable laser pulses over a wide wavelength range (280 nm-10 microm). The laser pulses were applied to the sample and the emitted fluorescence was detected using a fast-gating intensified CCD camera-based spectrometer. To verify the performance of the laser, the well-known protonation constant [Pure Appl. Chem. 69 (1997) 329] of 2,3-dihydroxybenzoic acid was determined. The fluorescence lifetime of the excited species was determined as 375+/-32 ps in the pH range from 1.0 to 6.0, having a fluorescence emission maximum at 438 nm. The first protonation constant was determined from fluorescence data as log K(3)=3.17+/-0.05 at an ionic strength of 0.1 M and at 294 K exploiting the Stern-Volmer mechanism. The agreement of the protonation constant with literature data (log K(3)=3.10+/-0.20, I=0.1 M, T=298 K [Bull. Soc. Jpn. 44 (1971) 3459]) demonstrates the excellent performance of our system. Furthermore, we determined the complex formation constant log K(1)=-3.11+/-0.16 by measuring the fluorescence properties of the ligand for the 1:1 uranyldihydroxobenzoate complex in the pH range from 3.0 to 4.5 at ionic strength of 0.1 M and at 294 K. We also determined the complex formation constant via the fluorescence emission of the metal ion uranium(VI). The fluorescence of the uranyl ion is influenced by dynamic quenching of the non-dissociated ligand and by static quenching due to the complex formation. After correction of these effects using the determined fluorescence lifetime, the complex formation constant was calculated to be log K(1)=-3.99+/-0.44. A 1:1 metal:ligand stoichiometry was determined with both measurement methods. However, the difference of the obtained formation constants and the derived standard deviations indicate a superimposition of effects with the excited-state reactions of the ligand.     

InAsSb/InAsSbP double heterostructure lasers for 3-4 micrometer spectral range

InAsSb/InAsSbP double heterostructure diode lasers for the spectral range of 3-4 microm grown by liquid phase epitaxy have been investigated. The laser tuning was studied as a function of the stripe width. The temperature and current tuning of such lasers was measured. Emission spectra, far-field patterns and wavelength tuning versus current have been studied in the wide current range from threshold, Ith, up to 6Ith at liquid nitrogen temperature. Current wavelength tuning in single-mode lasing has been obtained both towards the shorter wavelengths (up to 4.56 cm-1) and towards the longer wavelengths (up to 0.9 cm-1) at the temperature T=77K. Comparison of the emission properties of the lasers, driven by different types of current pulses showed the same quantum-mechanical nature of current tuning. The theoretical model of this nonlinear optical phenomenon is proposed. The estimated times of current tuning defined mainly by the photon lifetime in the cavity are about 10(-9) to 10(-12) s. The emission line-width was determined to be 20 MHz. Optimal conditions were found for the use of the lasers and were employed for the detection of NH3, CH3Cl, OCS and atmospheric water.     

Optical gain characteristics of C 460 and C 450

Dye concentration dependent gain spectra for Coumarin 460 (C 460) and Coumarin 450 (C 450) in ethanol have been studied using Amplified Spontaneous Emission (ASE) technique under Nitrogen laser (337.1 nm) excitation in the concentration range 10(-2)-10(-5) m/l. The dependence of lasing wavelength and peak gain on concentration have been understood in terms of variation of fluorescence lifetime, which is due to photo-physical processes such as radiation trapping and concentration-quenching. Pump intensity dependence of efficiency is also explained in terms of fluorescence lifetime. A comparison of the stability of the two dyes has also been made on the basis of the functional groups at different positions of the basic coumarin.     

A compact NIR fiber-optic diode laser spectrometer for CO and CO(2): analysis of observed 2f wavelength modulation spectroscopy line shapes

A compact fiber-optic diode laser spectrometer for the measurement of CO and CO(2) gas concentrations in the near infrared around 1580 nm is described. By use of a balanced receiver to suppress diode laser intensity noise a sensitivity of 6.4 x 10(-7) at 1 Hz system bandwidth was achieved. At a reduced pressure of 80 hPa this equals to a detection limit of 5.1 ppm CO and 9.1 ppm CO(2) with 1m absorption path length. The observed line shapes of the 2f wavelength modulation spectroscopy (WMS) scheme are analyzed theoretically and experimentally. Accurate measurements of magnitude and phase of the diode laser frequency and intensity modulation responses were found critically for modeling the observed line shapes. In situ measurements of gas dissociation processes inside of a medium-power carbon dioxide laser are presented as an application example.     

Measurements of line strengths in the 2nu1 band of the HO2 radical using laser photolysis/continuous wave cavity ring-down spectroscopy (cw-CRDS)

Absolute absorption cross sections of the absorption spectrum of the 2nu1 band of the HO2 radical in the near-IR region were measured by continuous wave cavity ring-down spectroscopy (cw-CRDS) coupled to laser photolysis in the wavelength range 6604-6696 cm(-1) with a resolution better than 0.003 cm(-1). Absolute absorption cross sections were obtained by measuring the decay of the HO2 self-reaction, and they are given for the 100 most intense lines. The most important absorption feature in this wavelength range was found at 6638.20 cm(-1), exhibiting an absorption cross section of sigma = 2.72 x 10(-19) cm2 at 50 Torr He. Using this absorption line, we obtain a detection limit for the HO2 radical at 50 Torr of 6.5 x 10(10) cm(-3).     

A Neutral Carrier Membrane Calcium-Sensitive Electrode with Wide Working pH Range

Abstract

A poly(vinyl chloride) (PVC) membrane calcium-sensitive electrode based on a new type of synthetic carrier 1,7-di[2-(1-phenylazo)naphtyl]-1,4,7-trioxaheptan is introduced. This electrode exhibited Nernstian response over the concentration range 1.0×10^?1 - 3.0×10^?8 mol/L Ca²⁺ with a slope of 28.8 mV/pCa in calcium ion buffer solutions. The detection limit for calcium ion was 1.0X10^?8 mol/L. The response time varied from 10 to 30 seconds. The working pH range for the electrode was 3.5 - 12.3 when the concentration of Ca²⁺ was 10^?3 mol/L. The lifetime of the electrode was proved to exceed 8 months. It was applied successfully in the determination of calcium ion in river water, mineral water and cosmetic. A method for the determination of total calcium in urine was developed.     

Selective ultra-trace detection of NO and NO2 in complex gas mixtures using broad-bandwidth REMPI mass spectrometry

In this paper we demonstrate the feasibility of ultra-trace resonance enhanced multiphoton ionization (REMPI) detection employing a small broad-bandwidth solid state laser system. The results reported here are compared with measurements carried out with a conventional excimer pumped dye laser combination. Mass selected broad-bandwidth REMPI spectra for the environmentally relevant nitrogen oxides NO and NO2 are presented. Tunable broad-bandwidth laser radiation with a spectral resolution of > 10 cm(-1) in the wavelength range 560-400 nm was employed for the detection of NO2. For NO detection, the range 230-224 nm was covered. Laser radiation was generated using an optical parametric oscillator pumped by an unseeded Nd:YAG laser. A mobile time-of-flight mass spectrometer equipped with an atmospheric pressure laser ionization source allowed for mass selective parent ion detection at m/z 30 for NO and m/z 46 for NO2. The limit of detection was 10 pptV for NO and 20 pptV for NO2. A selectivity of > 2000 for both compounds with respect to N2O5, organic nitrates and NO2 in the case of NO is reported. An improved laser system currently under construction is expected to provide detection limits below pptv mixing ratios for both nitrogen oxides in a 20 s integration interval.     

Rapid determination of lactulose in milk by microdialysis and biosensors

A simple and rapid flow system for the determination of lactulose in milk samples was developed. It is based on the hydrolysis of lactulose to galactose and fructose by the enzyme beta-galactosidase immobilised in a reactor. The amount of fructose produced was measured with an electrochemical biosensor based on the fructose dehydrogenase enzyme, K3[Fe(CN)6] as mediator and a platinum based electrochemical transducer. Parameters such as the enzyme immobilisation in the reactor and under the electrode surface, the lifetime of the beta-galactosidase reactor and of the dehydrogenase biosensor and the flow parameters were studied and optimised. Fructose was determined in the range 1 x 10(-6)-5 x 10(-3) mol l-1 with an RSD of about 2% and a detection limit of 5 x 10(-7) mol l-1. The use of a microdialysis probe as the sampling system permitted the direct measurement of lactulose in milk samples without pre-treatment in the range 1 x 10(-5)-5 x 10(-3) mol l-1. The sensitivity of the procedure allowed pasteurised, UHT and in-container sterilised milk to be distinguished.     

Semiconducting Group 15 Monolayers: A Broad Range of Band Gaps and High Carrier Mobilities

Optoelectronic applications require materials both responsive to objective photons and able to transfer carriers, so new two‐dimensional (2D) semiconductors with appropriate band gaps and high mobilities are highly desired. A broad range of band gaps and high mobilities of a 2D semiconductor family, composed of monolayer of Group 15 elements (phosphorene, arsenene, antimonene, bismuthene) is presented. The calculated binding energies and phonon band dispersions of 2D Group 15 allotropes exhibit thermodynamic stability. The energy band gaps of 2D semiconducting Group 15 monolayers cover a wide range from 0.36 to 2.62 eV, which are crucial for broadband photoresponse. Significantly, phosphorene, arsenene, and bismuthene possess carrier mobilities as high as several thousand cm² V^?1 s^?1. Combining such broad band gaps and superior carrier mobilities, 2D Group 15 monolayers are promising candidates for nanoelectronics and optoelectronics.     

Studies on properties and application of non-protected room temperature phosphorescence of propranolol

A direct and simple non-protected room temperature phosphorimetry (NP-RTP) for determine propranolol, which using I- as a heavy atom perturber and sodium sulfite as a deoxygenator, has been developed. The phosphorescence peak wavelength maxima lambda(ex)/lambda(em) = 288/494, 522 nm. The analytical curve of propranolol gives a linear dynamic range of 8.0 x 10(-8)-2.0 x 10(-5) mol l(-1) and a detection limit of 3 x 10(-8) mol l(-1). The influence of I- concentration on RTP lifetime of propranolol was studied and the luminescence kinetic parameters were calculated. It is found that the relation between I- concentration (x) and RTP lifetime (tau) can be expressed as tau = 1.25e(-0.477x) and the rate constants of phosphorescence emission k(p) was 0.800 per ms. The method was applied directly to determination of propranolol in urine and drug tablets with a satisfactory result. The recoveries were 96.6-97.4% and the relative standard deviation was 2% for the 1.00 x 10(-6)-4.00 x 10(-6) mol l(-1) propranolol in spiked urine sample.