Appearance of pure fluorocarbon micelles surveyed by fluorescence quenching of amphiphilic quinoline derivatives in fluorocarbon and hydrocarbon surfactant mixtures

A halide-sensitive fluorescence probe was utilized to evaluate the miscibility of fluorocarbon and hydrocarbon surfactants in aqueous micellar systems. The fluorescence of 6-methoxy-N-1,1,2,2-tetrahydroheptadecafluorodecylquinolinium chloride, FC10MQ, was quenched by halide ions dissociated from the surfactant. The fluorescence in micellar solutions showed an initially rapid decay. This suggests that halide ions effectively quench FC10MQ fluorescence at the micellar surface. The subsequent slow decay corresponds to the quenching of FC10MQ fluorescence in the aqueous bulk phase by the free counterions. The Stern-Volmer plots for fluorescence quenching gave a distinct break at the critical micelle concentration of the cationic surfactants. The abrupt increase in fluorescence quenching is attributed to the solubilization of the probe in the micelles. The fluorescence quenching behavior provides direct information about the immiscibility of fluorocarbon and hydrocarbon species in micelles, and the results indicate that almost pure fluorocarbon micelles appear in surfactants mixtures.     

Electrochemiluminescence Quenching by Halide Ions at Bipolar Electrodes

Quenching of Ru(bpy)₃²⁺ electrochemiluminescence (ECL) by Cl^?, Br^?, and I^? ions was studied as a function of halide concentration in a bipolar electrochemical cell. All of the halides investigated showed similar qualitative behavior: above a critical concentration, ECL intensity was found to decrease linearly as the halide ion concentration was increased, due to dynamic quenching of Ru(bpy)₃²⁺ ECL. Stern‐Volmer slopes (K_SV) of 0.111±0.003, 4.2±0.3, and 6.2±0.3 mM^?1 were measured for Cl^?, Br^? and I^?, respectively. The magnitude of K_SV correlates with halide ion oxidation potential, consistent with an electron transfer quenching mechanism. Using the bipolar platform described herein, aqueous, halide‐containing solutions could be quantified rapidly using the sequential standard addition method. The lower detection limit is determined by a complex mechanism involving the competitive electrooxidation of halide ions and the ECL co‐reactants, as well as the passivation of the surface of the bipolar electrode, and was found to be 0.20±0.01, 0.08±0.01 and 10±1 mM, respectively, for I^?, Br^?, and Cl^?. The performance of the bipolar ECL quenching assay is comparable to previously published fluorescence quenching methods for the determination of halide ions, while being much simpler and less expensive to implement.     

A Fluorescence Quenching Method for the Determination of Iodide Ion with Salicylfluorone and Hydrogen Peroxide

Abstract

A highly sensitive and selective fluorescence quenching method has been developed for rapid determination of iodide ion with salicylfluorone (SAF) as fluorogenic reagent (λ_ex = 495 nm, λ_em = 520 nm) at pH 2.5-3.0. The calibration graph is linear over the range 0.05-300 μg/25 ml. The detection limit is 0.05 μ/25 ml iodide. Other halide ions do not interfere with the determination even when present in large excess. The method is rapid and was successfully applied for the determination of iodide ion in sodium chloride, table salt and low sodium salt.     

Fluorescence quenching of coumarins by halide ions

Fluorescence quenching of 4-methyl-7-methoxy coumarin (1) and 4-methyl-5-ethoxy-7-methoxy coumarin (2) in aqueous solutions have been studied at different concentrations of halide ions (Cl-, Br-, I-), at room temperature approximately 20 degrees C. It is observed that the fluorescence intensity of both the coumarin compounds (1 and 2) decrease with increase in the concentration of Br- and I- ions but remains almost constant in case of Cl- ion. It is observed that the quenching due to halide ions proceeds via both a diffusional and static quenching processes. The rate constants for diffusional as well as static component of quenching process have been calculated using modified Stern-Volmer relation. It is further observed, that I- ion has very high quenching ability than Br- ion and Cl) ion almost behaves as a non-quencher. It is explained in terms of the sphere of action model by showing that the value of radius of sphere of action of the halide quencher is greater than the sum of the radii of the respective coumarin and quencher. Further, pattern of the quenching ability of the halide quenchers is found to be as I- > Br- > Cl- and interestingly this is in the same order as of their ionization energy. Finally, the present quenching process has been attributed to the electron transfer resulting between colliding species.     

Synthesis and Fluorescence Quenching Study of the Novel Cationic Probe Derived from Luminarosine

A simple and efficient transformation of the zwitterionic luminarosine into a brightly fluorescent cationic analogue, namely 1‐amino‐9‐methoxy‐2,4,10‐triaza‐4b‐azoniaphenanthrene ( 3 ), is reported. The fluorescence quenching of 3 by common nucleotides, calf‐thymus (CT) DNA, and halide ions was investigated by means of spectrophotometric and spectrofluorometric methods. Intermolecular static and dynamic fluorescence‐quenching constants for quenching of 3 by nucleotides and halide ions were determined in aqueous solution. Evidence for formation of nonfluorescent ground‐state complexes of 3 with nucleotides and CT‐DNA is presented. Scatchard analysis of the CT‐DNA quenching data resulted in a binding constant of 2.8×10⁴ M ⁻¹ and a number of binding sites per base pair of 0.049.     

离子液体中卤素离子杂质的离子色谱-直接电导检测法分析

研究了离子色谱-直接电导检测法分离测定离子液体中的卤素离子(F~-、Cl~-、Br~-)杂质.采用Shim-pack IC-A3阴离子交换色谱柱,考察了淋洗液种类及浓度、流速和色谱柱温度对分离测定的影响.最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,色谱柱温45 ℃.在此条件下可以基线分离卤素离子,且NO~-_3、BF~-_4、SO~(2-)_4不干扰测定.该法测定卤素离子的检出限(S/N=3)为0.02 ～0.11 mg/L,峰面积的相对标准偏差(n=5)不大于0.7%,F~-、Cl~- 和Br~- 的标准曲线的线性范围分别为0.1 ～50、0.1 ～50、0.5 ～100 mg/L.将方法用于烷基咪唑四氟硼酸盐离子液体中卤素离子杂质的测定,加标回收率为98% ～102%.     

卤代荧光素荧光猝灭法测定肾上腺色腙

在pH=6.6 的缓冲介质中, 肾上腺色腙(CBZC)与二氯荧光素(DCF)、二溴荧光素(DBF) 和二碘荧光素(DIF)通过静电引力、芳基堆积作用和范德华力形成摩尔比为2: 1的复合物, 引起上述二卤代荧光素的荧光发生猝灭, 最大猝灭波长分别位于533, 536和560 nm. 其荧光猝灭值(ΔF)在一定范围内与肾上腺色腙浓度成正比, 荧光猝灭反应具有较高的灵敏度, 对CBZC的检出限分别为3.3 ng/mL(CBZC-DCF体系), 5.7 ng/mL(CBZC-DBF体系)和129.6 ng/mL(CBZC-DIF体系). 考察了共存物质的影响、荧光猝灭反应的适宜条件和影响因素, 结果表明, 该方法具有良好的选择性, 可用于CBZC的血药和尿药浓度的快速检测. 从温度的影响、荧光寿命以及Stern-Volmer图判断该反应为静态猝灭反应.     

Analysis of chloride, bromide and iodide using miniaturised isotachophoresis on a planar polymer chip

A new method has been developed to allow the determination of the halide anions chloride, bromide and iodide using isotachophoresis. This method employs a new electrolyte system which incorporates the novel application of indium(III) as a complexing agent. This electrolyte system was devised based on the findings of an investigation into the potential for using indium(III) as a complexing counter ion to selectively manipulate the effective mobilities of halide ions. A leading electrolyte incorporating 3.5 mmol dm(-3) of indium(III) allowed the simultaneous determination of chloride, bromide and iodide to be successfully achieved. The new procedure allows such separations to be made without interference from common inorganic anions such as sulfate and nitrate. Separations were performed using a miniaturised planar poly(methyl methacrylate) chip with integrated platinum wire conductivity detection electrodes. Using this instrumentation the limits of detection were calculated to be 0.7 mg dm(-3), 1.7 mg dm(-3) and 2.2 mg dm(-3) for chloride, bromide and iodide respectively.     

The dependence of quinine fluorescence quenching on ionic strength

The Stern-Volmer constant for the quenching of quinine fluorescence by chloride ions has been found to be markedly dependent on acid concentration. Steady-state and time-resolved fluorescence measurements under different acid and salt concentrations have further shown that the decrease in quenching arises from the influence of increasing ionic strength on the diffusion-controlled rate constant for the bimolecular quenching process. Two possible mechanisms for this dependence are discussed: a decrease in the intrinsic rate constant for the reaction due to the kinetic salt effect, and a decrease in the effective encounter distance due to screening of the charges on the reactants. © 1996 John Wiley & Sons, Inc.     

硅掺杂碳量子点荧光猝灭法测定水样中铜(Ⅱ)

3-氨丙基三甲氧基硅烷(APTMS)与戊二醛(GA)混合前驱物合成的硅掺杂碳量子点(SDCQDs),其最大吸收、激发和发射波长分别为259,245,395 nm,量子产率为13.60%,XPS谱图表明碳量子点掺杂Si,且富含甲亚胺基团和硅氧键。Cu~(2+)对碳量子点荧光产生猝灭作用,依据Cu~(2+)浓度与碳量子点荧光强度猝灭率的相关性,建立碳量子点荧光探针测定水样中Cu~(2+)的分析方法,其它金属离子对Cu~(2+)干扰程度较小,回收率为91.4%~100.8%,检出限为0.13μmol/L,相对标准偏差为0.20%~0.92%。     

以吖啶染料荧光猝灭为基础的卤素阴离子检测研究

合成了两种吖啶及吖啶橙盐类小分子化合物和带有吖啶盐的三元共聚物.研究了它们在溶液中的荧光被卤素离子猝灭的问题.发现它们能强烈地被碘离子所猝灭而不易被氯离子猝灭,表明这类化合物有可能用于在有氯离子存在条件下对碘、溴离子的检测.对荧光猝灭机理进行的研究发现,卤素离子的猝灭能力并不和它们对发光化合物的系间窜越和三重态的生成等有关,而是和阴离子对极化分子的作用减弱了分子内的电荷转移能力相关.     

2-氯化-n-氨基葡萄糖乙酰基三苯基季膦盐与DNA作用的荧光光谱研究及其应用

本文合成了2-氯化-n-氨基葡萄糖乙酰基三苯基季膦盐(2-GATPC)。利用荧光光谱法研究了2-GATPC与DNA的作用。实验结果表明,在pH3左右,DNA以静态猝灭的方式使2-GATPC的荧光强度显著降低。DNA的浓度在1.6×10-6~4.8×10-5mol.L-1的范围内,对2-GATPC的荧光有良好的线性猝灭关系,据此可以测定DNA,检出限可达8.4×10-7mol.L-1。方法简便快速,背景干扰小,对合成样品中DNA的测定,结果令人满意。     

Acid/Base‐Mediated Uptake and Release of Halide Anions with a Preorganized Aryl‐Triazole Foldamer

A new approach for the construction of artificial receptors capable of selectively uptake and release of halides to mimic the biological halide ions pumps is developed, in which the preorganized aryl‐triazole foldamer was designed to bear a resorcinolic group in the central strand as a switch regulator. By using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene/picric acid as the trigger, the foldamer can be switched between “w”‐shape and helical conformation. Due to the large, half‐open cavity as well as the additional electrostatic repulsion between oxyanions and guest halide, the foldamer in “w”‐shape possesses a much weaker affinity for chloride, bromide, and iodide anions than those in the helical conformation in 6:94 (v/v) [D₆]DMSO/CDCl₃. When the foldamer and chloride ions have the same initial concentrations of 1 mM , 70 % chloride ions in the solution could be reversibly bound or released upon switching.     

高荧光量子产率钕、氮双掺杂碳点用于柳氮磺吡啶检测及Hela细胞成像

以柠檬酸氢二铵、缓血酸铵和硝酸钕为起始原料,通过水热法合成了荧光量子产率为93.05%、发蓝色荧光的钕、氮双掺杂碳点（Nd,N-CDs）。采用透射电子显微镜（TEM）、粉末X射线衍射（XRD）、红外光谱（FT-IR）及X射线光电子能谱（XPS）等技术对Nd,N-CDs的形貌及表面结构进行了详细表征,采用紫外可见吸收光谱及荧光光谱考察了其光学性质和稳定性。结果显示,药物分子柳氮磺吡啶（SSZ）能够使Nd,N-CDs的荧光显著降低,而金属离子及另外4种药物分子没有明显效果。由此,建立了一种选择性检测SSZ的荧光检测方法,线性检测范围在0.1~50 μmol/L之间,检出限低至0.05 μmol/L。机理探讨表明,荧光猝灭主要涉及动态猝灭和荧光共振能量转移两种机制。所建立的分析方法能用于测定实际药片中的SSZ含量,回收率为98.1%~104.2%。此外,Nd,N-CDs表现出很好的生物相容性,能够作为荧光探针穿透细胞壁使细胞质染色,因不会进一步穿透进入细胞核,很好的避免了对细胞的深层次破坏。     

11-Mercaptoundecanoic acid functionalized gold nanoclusters as fluorescent probes for the sensitive detection of Cu2+ and Fe3+ ions

Metal ions are physiologically essential,but excessive metal ions may cause severe risk to plants and animals.Here,we prepared gold nanoclusters(Au NCs) protected by 11-mercaptoundecanoic acid(11-MUA),which have excellent fluorescence properties for the detection of metal ions.The results showed that the copper ions(Cu~(2+)) and iron ions(Fe~(3+)) in the solution have obvious quenching effect on the fluorescence intensity of Au NCs.The detection range of Fe~(3+) was 0.8–4.5 mmol/L(R~2= 0.992) and 4.5–11.0 mmol/L(R~2= 0.997).And Cu~(2+) has a lower linear range(0.1–1.0 mmol/L,R2= 0.993).When EDTA was added into the reaction system,it was observed that the quenching effect of Cu~(2+) and Fe~(3+)on Au NCs showed different phenomenon.Then,the effect of metal ions on the fluorescence of Au NCs was investigated.The selective detection of Cu~(2+) was achieved by EDTA masking of Fe~(3+).In addition,we realized the metal ions detection application of Au NCs in the serum     

Oligomer Sensor Nanoarchitectonics for “Turn-On” Fluorescence Detection of Cholesterol at the Nanomolar Level

Sensitive and rapid monitoring of cholesterol levels in the human body are highly desirable as they are directly related to the diagnosis of cardiovascular diseases. By using the nanoarchitectonic approach, a novel fluorescent conjugated oligofluorene (OFP-CD) functionalized with β-cyclodextrin (β-CD) was assembled for “Turn-On” fluorescence sensing of cholesterol. The appended β-CD units in OFP-CD enabled the forming of host-guest complexes with dabsyl chloride moieties in water, resulting in fluorescence quenching of the oligofluorene through intermolecular energy transfer. In the presence of cholesterol molecules, a more favorable host-guest complex with stoichiometry 1 cholesterol: 2 β-CD units was formed, replacing dabsyl chloride in β-CD’s cavities. This process resulted in fluorescence recovery of OFP-CD, owing to disruption of energy transfer. The potential of this nanoarchitectonic system for “Turn-On” sensing of cholesterol was extensively studied by fluorescence spectroscopy. The high selectivity of the sensor for cholesterol was demonstrated using biologically relevant interfering compounds, such as carbohydrates, amino acids, metal ions, and anions. The detection limit (LOD value) was as low as 68 nM, affirming the high sensitivity of the current system.     

Ratiometric determination of Hg2+ ions based on simple molecular motifs of pyrene and dioxaoctanediamide

A new podand-type dioxaoctanediamide-based chemosensor having two pyrene moieties was prepared, and its fluoroionophoric behaviors toward transition-metal ions were investigated. Pyrene-appended dioxaoctanediamide 1 showed a selective fluorescence quenching toward Hg2+ ions over other transition-metal ions in an aqueous methanol solution. Unique responses in pyrene monomer and excimer emissions allowed selective ratiometric determination of Hg2+ ions in aqueous environments, and the detection limit was found to be 1.6 x 10(-6) M. [structure: see text]     

High Sensibility of Quantum Dots to Metal Ions Inspired by Hydroxyapatite Microbeads

An approach for the sensitive and selective determination of Ag⁺, Cu²⁺ and Hg²⁺ ions was developed based on the fluorescence quenching of mercaptopropionic acid (MPA) capped CdTe quantum dots in the existence of hydroxyapatite (HAP) nanoribbon spherulites. Among various metal ions investigated, it was found that the fluorescence of CdTe QDs was only sensitive to Ag⁺, Cu²⁺ and Hg²⁺ ions. The addition of HAP into the CdTe system could bring forward a sensitivity improvement of about 1 to 2 orders of magnitude in the detection of Ag⁺ and Cu²⁺ compared with the plain CdTe system without the existence of HAP; while there was no sensitization effect for Hg²⁺. Under optimal conditions, the detection limits for Ag⁺, Cu²⁺ and Hg²⁺ were 20, 56 and 3.0 nmol·L^?1, respectively, and the linear ranges were 0.02–50, 0.056–54 and 0.003–2.4 µmol·L^?1, respectively. Mechanisms of both QDs fluorescence quenching by metal ions and the sensitization effect by HAP were also discussed.     

Donor–acceptor interactions between resonance-excited silver nanoparticles and halide ions in water solutions

Donor–acceptor interactions between silver nanoparticles (NPs), resonance-excited by optical quanta of light, and halide ions are studied in aqueous solutions. It is shown that deactivation of the plasmon excitation of Ag NP proceeds according to the exchange mechanism of electron transfer. Plasmon excitation quenching constants are determined and a correlation between quenching and the donor properties of halide ions is found. The efficiency of electrostatic interaction between resonantly-excited Ag NPs and halide ions is studied, and their dipole moment is determined.

     

2-Aminopyridine derivative as fluorescence ‘On–Off’ molecular switch for selective detection of Fe3+/Hg2+

2-Amino-6-methyl-4-phenyl-nicotinonitrile 1, a 2-aminopyridine-based fluorescent compound, was found to be a fluorescent chemosensor for the detection of Fe³⁺ and Hg²⁺ ions over a number of other metal ions. Compound 1 was synthesized in one step using a multicomponent reaction, and characterized using common spectroscopic tools. During Fe³⁺/Hg²⁺ sensing the compound 1 followed a ‘switch-off’ mechanism. Further, compound 1 could sense Fe³⁺ over Hg²⁺ by its distinct absorption and fluorescence quenching behaviors. 1:1 complex formation of 1 with Fe³⁺ and Hg²⁺ was clearly understood from Job’s plot. The present work brings additional evidence on the importance of multicomponent reactions which could lead to the development of fluorescence chemosensor in one step for the selective detection of biologically important metal ions.