Fluorescence Enhancement of Aflatoxins Using Native and Substituted Cyclodextrins

Cyclodextrins have been used as fluorescence enhancers in HPLC to improve thedetection limits of aflatoxins, cancerogens which can be found in severalfoodstuffs. In this work, a screening of several cyclodextrins has been performedin order to find the factors affecting the fluorescence enhancement. Evidence for formationof a 1 : 1 AF-CD inclusion complex has been achieved by titration and competitiveexperiments with adamantanecarboxylic acid and by fluorescence quenching by KI.Stability constants of the AF-CD complexes were evaluated.     

基于小分子的铜离子与汞离子双识别荧光探针

铜离子在不同细胞生理过程中作为催化辅助因子起着很重要的作用,但是体内铜离子浓度出现异常也会导致疾病甚至死亡。与铜离子相比,汞离子是各种重金属污染物中最普遍、最危险的一种。因此,对它们高灵敏度、高选择性检测具有非常重要的意义。荧光探针法由于具有灵敏度高、快速便捷、可视化和原位无损检测等优点而成为Cu²⁺与Hg²⁺离子重要的检测手段之一。本文总结了近几年基于小分子Cu²⁺和Hg²⁺离子双识别荧光探针的设计合成、性能及其在分析方面的研究与最新进展,并展望了此类荧光探针未来的研究与发展方向。     

同步荧光光谱法研究丹参素-牛血清白蛋白体系的光增强效应

采用紫外光谱法和同步荧光光谱法研究了丹参素与牛血清白蛋白的结合特性.体系的紫外光谱显示,丹参素与牛血清白蛋白(BSA)之间发生了相互作用并生成新的复合物,同步荧光光谱则表明,丹参素对BSA存在荧光增强效应.随着丹参素浓度的增加,Δλ=15 nm时体系荧光强度明显增强,最大发射波长为285 nm,且不随浓度增加而发生变化...     

氢化物发生-双道原子荧光光谱法同时测定钢中砷和锑

建立了一种氢化物发生双道原子荧光光谱法同时测定钢中痕量砷和锑的方法．对实验条件进行了优化,在最佳工作条件下,砷和锑的检出限分别为0．012ng／g和0．034ng／g,RSD分别为1．24％和1．97％．将本法应用于钢中的砷和锑的测定,采用加标回收实验控制方法的准确性,砷的回收率为96％～98％,锑的回收率98％～102％．     

Microwave-Optical Double Resonance and Intermodulated Fluorescence Studies of Thioformaldehyde

Studies of the 4¹₀ band of the à ¹A₂ X?¹A₁ transition of thioformaldehyde by means of intermodulated fluorescence and microwave-optical double resonance have revealed numerous small perturbations in the excited state levels caused by high rovibronic levels of the ground state. Singlet-triplet perturbations have been studied by the same techniques and also by anticrossings produced in the presence of a magnetic field. The use of microwave-optical double resonance for studying collisional processes is discussed.     

双道原子荧光光谱法测定蔬菜中的砷和汞

采用湿法消解蔬菜样品,用AFS-230E型双道原子荧光光度计测定蔬菜中的As和Hg重金属含量。在最佳实验条件下,As和Hg元素的工作曲线相关系数(r)分别为0.999 2和0.999 6,检出限分别为0.011 9和0.013 9μg/L,加标回收率分别为:91.6%~101.5%和89.8%~97.3%,相对标准偏差(RSD,n=7)分别为1.4%和0.52%,方法可供各地测定各类蔬菜中As和Hg等重金属元素含量作参考。     

Fabrication of Dye-sensitized Solar Cells and Fluorescence Quenching Study Using Thiophene Based Copolymers

Photovoltaic performance of dye sensitized solar cells fabricated with a commercially available thiophene based copolymer was investigated. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)], a highly soluble polythiophene, was used as a sensitizer. An open-circuit voltage of 0.64 V and a short-circuit current density of 0.36 mA/cm² were measured. The incident photon to current conversion efficiency for the polymer was measured. Fluorescence from the other polythiophene, poly(3,3′-didodecyl quarter thiophene) was found to be quenched when blended with phenyl C₆₁ butyric acid methyl ester (PCBM) (1:1 wt ratio), indicating the charge transfer from the conjugated polymer to PCBM.     

Study of the Fluorescence Enhancement of Eu-Y-DEM-Dibenzoylmethane-Ammonia System

Abstract

The fluorescence enhancement and solvent effect of Eu-dibenzoylmethane-ammonia system was studied. The fluorescence intensity of the system can be greatly increased by y³⁺. The maximum fluorescence intensity was obtained at pH 8.9 – 9.5. The fluorescence intensity is a linear function of Eu²⁺ in the range of 1.0x10^?9 M -4.0x10^?8 M. The detection limit is 1.1x10^?10 M. The optimized procedure is applied to the determination of europium in lanthanide oxide samples.     

双光子荧光有机纳米粒子的细胞染色

本文采用具有较大双光子吸收截面的有机分子2,5,2′,5′-(4′-N,N-二苯胺苯乙烯基)联苯(DPA-TSB)(双光子吸收截面δ: 3288 GM, 1 GM=1×10^-50 cm⁴·s·photon^-1·molecule^-1), 通过再沉淀法制备水相分散的纳米粒子. 研究表明, 这种有机双光子纳米粒子可以有效地富集在细胞质中, 对细胞染色显示出良好的荧光成像能力.     

CdSe量子点荧光增敏法测定甘草酸

以巯基乙酸为稳定剂水相法一步合成了CdSe量子点,并以此量子点为荧光探针,基于甘草酸(GL)对量子点的荧光增强效应,建立了一种简便、快速、灵敏测定GL的分析方法,同时对GL与CdSe量子点的反应机理进行了初步探讨.考察了多种因素对GL测定的影响.结果表明,在pH 7.4的Na2 HPO4 - NaH2 PO4缓冲溶液中...     

Fluorescence Signal Amplification by Cation Exchange in Ionic Nanocrystals

Lighting‐up time : A cation‐exchange reaction releases thousands of divalent cations from nonfluorescent CdSe ionic crystals and triggers fluorescence from thousands of originally nonfluorescent Fluo‐4 fluorophores to obtain a large fluorescence amplification (see picture) and a low detection limit in bioassays. The technique is fast, simple, with a large dye‐to‐reporter labeling ratio, and flexible in selection of nanocrystals and fluorophores.

     

Fluorescence Dynamics in the Endoplasmic Reticulum of a Live Cell: Time‐Resolved Confocal Microscopy

Fluorescence dynamics in the endoplasmic reticulum (ER) of a live non‐cancer lung cell (WI38) and a lung cancer cell (A549) are studied by using time‐resolved confocal microscopy. To selectively study the organelle, ER, we have used an ER‐Tracker dye. From the emission maximum of the ER‐Tracker dye, polarity (i.e. dielectric constant, ?) in the ER region of the cells (≈500 nm in WI38 and ≈510 nm in A549) is estimated to be similar to that of chloroform ( =506 nm, ?≈5). The red shift by 10 nm in in the cancer cell (A549) suggests a slightly higher polarity compared to the non‐cancer cell (WI38). The fluorescence intensity of the ER‐Tracker dye exhibits prolonged intermittent oscillations on a timescale of 2–6 seconds for the cancer cell (A549). For the non‐cancer cell (WI38), such fluorescence oscillations are much less prominent. The marked fluorescence intensity oscillations in the cancer cell are attributed to enhanced calcium oscillations. The average solvent relaxation time (<τ_s>) of the ER region in the lung cancer cell (A549, 250±50 ps) is about four times faster than that in the non‐cancer cell (WI38, 1000±50 ps).     

Recent Progress in Fluorescence Signal Design for DNA-Based Logic Circuits

DNA-based logic circuits, encoding algorithms in DNA and processing information, are pushing the frontiers of molecular computers forward, owing to DNA′s advantages of stability, accessibility, manipulability, and especially inherent biological significance and potential medical application. In recent years, numerous logic functions, from arithmetic to nonarithmetic, have been realized based on DNA. However, DNA can barely provide a detectable signal by itself, so that the DNA-based circuits depend on extrinsic signal actuators. The signal strategy of carrying out a response is becoming one of the design focuses in DNA-based logic circuit construction. Although work on sequence and structure design for DNA-based circuits has been well reviewed, the strategy on signal production lacks comprehensive summary. In this review, we focused on the latest designs of fluorescent output for DNA-based logic circuits. Several basic strategies are summarized and a few designs for developing multi-output systems are provided. Finally, some current difficulties and possible opportunities were also discussed.     

Dramatic Fluorescence Enhancement of Bare Carbon Dots through Facile Reduction Chemistry

Reduction of bare carbon dots (CDs) in aqueous NaBH₄ solution is a facile and effective approach to enhance their fluorescence without any surface coverage. CDs are treated with dilute aqueous NaBH₄ solutions, enhancing their quantum yields (QYs) successfully from 1.6 % to 16 % which is comparable to semiconductive QDs in aqueous environments. If pristine CDs are treated hydrothermally prior to reduction by NaBH₄, QYs reach 40.5 %. This value is among the highest QYs reported for bare CDs in the literature. The approach to enhance fluorescence through chemical reduction is generally applicable to other kinds of CDs synthesized by various methods. Alteration of the chemical structure of the CDs by NaBH₄‐reduction is analyzed by ¹³C NMR, X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy, which demonstrate that the carbonyl group content is decreased after NaBH₄‐reduction, whereas the number of sp³‐type carbon defects is increased. The valence‐band maxima (VBM) near the surface related to the surface energy bands of the CDs are estimated by XPS. VBM data show a semiconducting layer on the surface of the CDs, and the VBM of the CDs decrease with increasing NaBH₄‐reduction time. The layered graphite structures in the cores of the CDs are clearly observed by transmission electron microscopy (TEM). CDs could perhaps be regarded as semiconductive surface defect layers formed by chemical erosion over conductive graphite cores. Chemical reduction by NaBH₄ changes the surface‐energy bands of the CDs, thus, enhances their fluorescence. The fluorescence properties of aqueous NaBH₄‐reduced CDs are also studied for possible biological applications.     

Multipolar Porphyrin-Triazatruxene Arrays for Two-Photon Fluorescence Cell Imaging

Two-photon excited fluorescent (TPEF) materials are highly desirable for bioimaging applications owing to their unique characteristics of deep-tissue penetration and high spatiotemporal resolution. Herein, by connecting one, two, or three electron-deficient zinc porphyrin units to an electron-rich triazatruxene core via ethynyl π-bridges, conjugated multipolar molecules TAT-(ZnP) _n (n=1–3) were developed as TPEF materials for cell imaging. The three new dyes present high fluorescence quantum yields (0.40–0.47) and rationally improved two-photon absorption (TPA) properties. In particular, the peak TPA cross section of TAT-ZnP (436 GM) is significantly larger than that of the ZnP reference (59 GM). The δ_TPA values of TAT-(ZnP)₂ and TAT-(ZnP)₃ further increase to 1031 and up to 1496 GM, respectively, indicating the effect of incorporated ZnP units on the TPA properties. The substantial improvement of the TPEF properties is attributed to the formation of π-conjugated quadrapole/octupole molecules and the extension of D -π-A-D systems, which has been rationalized by density function theory (DFT) calculations. Moreover, all of the three new dyes display good biocompatibility and preferential targeting ability toward cytomembrane, thus can be superior candidates for TPEF imaging of living cells. Overall, this work demonstrated a promising strategy for the development of porphyrin-based TPEF materials by the construction and extension of D -π-A-D multipolar array.     

用荧光猝灭和荧光加强两种理论研究头孢类药物与白蛋白的作用

应用荧光加强和荧光猝灭两种理论公式，对七种头孢类抗菌药物与人血清和牛血清白蛋白的作用作进行了对比研究，对药物与白蛋白的结合特点和通常的表征量：解离常数、猝灭常数、猝灭效率、能量转移效率、给体-受体作用距离等，进行了深入地分析。     

基于氮掺杂碳点的荧光增强简便、快速而准确地检测环丙沙星

以苹果酸为碳源,磷酸铵提供氮源,采用固态热解法一步合成一种水溶性的、氮掺杂的蓝色荧光碳点(N-CDs)。 所得到的碳点荧光量子产率高达20.7%,形貌近似球形,平均粒径约为3.3 nm。 基于环丙沙星(CIP)对碳点的荧光增强作用,建立了一种CIP的定量检测方法。 最佳实验参数为:碳点浓度为7.5 μg/mL,pH值为5.9,孵化时间为5 min。 在此实验条件下,碳点的荧光强度增加值(ΔF)和CIP的浓度在0.39~40.00 μmol/L范围内呈良好的线性关系,方法的检出限为0.12 μmol/L,相对标准偏差(n=5)为4.2%。 干扰实验结果指出,除了铜离子具有明显的影响外,其它共存物质的干扰可以忽略不计,而铜离子的干扰可通过加入草酸铵来掩蔽。 最后利用所构建的荧光传感器对实际样品中CIP进行检测,回收率在93%~107%之间。 本研究为CIP定量分析提供了一种简单、快速、灵敏度高、选择性好而有效的测定方法。