Spectral Properties and Solubilization Location of 2'-Ethylhexyl 4-(N,N-Dimethylamino)benzoate in Micelles

在阳离子、非离子和阴离子表面活性剂胶束溶液中,研究了4-(N,N-二甲氨基)苯甲酸2'-乙基己基酯(EHDMAB)的双重荧光和紫外吸收．当EHDMAB增溶在不同的胶束溶液中,紫外吸收增强,在离子型胶束溶液中,可观察到具有较长波长的EHDMAB分子内扭转电荷转移(TICT)荧光,相反,在非离子型胶束溶液中,可观察到具有较短波长TICT荧光,特别是位于阳离子胶束Stern层中的吡啶阳离子可强烈猝灭EHDMAB分子的双重荧光,所吸收的紫外辐射主要通过TICT荧光和非辐射去活化衰减．按照EHDMAB分子TICT荧光在有机溶剂中的极性依赖性,EHDMAB分子的4-(N,N-二甲氨基)在离子型胶束和非离子型胶束中处于不同的极性环境;根据EHDMAB和表面活性剂分子的结构和大小分析,EHDMAB分子的4-(N,N-二甲氨基)应朝向胶束的极性头基团,而2'-乙基己基链则朝向疏水性的胶束内核．动态荧光猝灭测量为EHDMAB分子在不同胶束中的位置进一步提供了佐证．     

Confinement of 4,4-Diaminodiphenyl Sulfone by γ –CD in Micellar Environment: A Spectroscopic Investigation

This paper reports the double confinement of 4,4-diaminodiphenyl sulfone (Dapsone) inside γ–cyclodextrin (CD) in presence of surfactants (cationic, anionic and nonionic) using steady-state and time-resolved fluorescence spectroscopy. Interpretation of fluorescence spectra, fluorescence anisotropy and time resolved fluorescence decay of the γ-CD?Dapsone?micellar system hints at lesser microviscosity and the partial release of the probe molecule from the supramolecular host–guest complex in ionic micelles, of which greater in cationic micelles, but due to greater restriction and rigidity in presence of non-ionic micelle makes the probe more rigidly inside CD. Changes in computed rotational decay also corroborate the above findings.

Modulation of Intramolecular Charge Transfer Emission Inside Micelles: A Fluorescence Probe for Studying Microenvironment of Micellar Assemblies

Modulation of intramolecular charge transfer reaction of ethyl ester of N,N-Dimethylaminonaphthyl-(acrylic)-acid (EDMANA) in anionic sodium dodecyl sulfate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and non-ionic p-tert-octylphenoxy polyoxyethanol (Triton-X 100, TX-100) micelles has been addressed using steady state and time resolved spectroscopy. The interaction of the CT probe EDMANA with micelles and its location inside the micelles have been investigated by the study of fluorescence spectral band position of EDMANA in micelle, the effective polarity of micelle-water interface and cetyl pyridinium chloride induced fluorescence quenching measurement. The effects of urea on the properties of the micelles such as Critical Micelle Concentration and the interaction between EDMANA and micelles have been explored using EDMANA as emission probe.     

硫杂杯[4]芳烃基胶束自组装荧光探针的结构性质及检测性能的研究

水体中重金属污染因威胁生态环境和人类健康而被受广泛关注。荧光探针由于具有快速高效检测重金属的特性,一直是该领域的研究热点。通常,荧光探针在结构上包括对待测物质起识别作用的受体和能产生信号响应的荧光体,并逐步形成了内在型、共轭型、系综型和模板辅助自组装型等四种结构类型。近年来,基于受体和荧光体在表面活性剂胶束内自组装而形成的胶束自组装型荧光探针因结构简单、易于制备、能直接应用于水环境等特点逐渐受到重视。以对铜离子具有优异结合性能的对叔丁基硫杂杯[4]芳烃（TCA）为受体,以芘、荧蒽、蒽、菲、苝等分子为荧光体,通过表面活性剂胶束自组装制备针对Cu2+检测的胶束自组装型荧光探针,采用参比法测定了胶束自组装荧光探针的荧光量子产率,采用稳态荧光法测定了胶束聚集数,同时通过计算荧光猝灭率分别考察了荧光体种类、复配表面活性剂等因素对该探针的Cu2+检测性能的影响情况。实验结果显示,采用十二烷基硫酸钠（SDS）、曲拉通100（TX-100）、聚氧乙烯月桂醚（Brij35）等三种不同的表面活性剂对探针荧光体的荧光量子产率产生了明显影响,测得的荧光探针荧光量子产率介于0.25~0.47,且三者逐渐增大,说明表面活性剂改变了胶束内荧光分子芘所处微环境的极性,且不同类型表面活性剂对微环境极性的影响程度有所差异,微环境极性的增强对极性更大的激发态芘具有更强的稳定作用。而受体TCA的加入对荧光体所处微环境极性影响较小,未对荧光量子产率产生较大影响。但TCA的加入使探针的胶束聚集数明显减少,这归因于具有两亲性的受体TCA分子通过胶束自组装进入并分散在表面活性剂分子层中,形成共胶束结构,从而改变了表面活性剂分子的聚集状态。荧光体变更对荧光探针的Cu2+检测性能有显著影响,在同样条件下,以荧蒽、蒽、菲作为荧光体的探针检测Cu2+所得到的荧光猝灭率远高于芘、苝,这主要是因为不同荧光体在从激发态返回基态时辐射跃迁所释放能量不同,其能量与受体TCA识别Cu2+所需能量之间的匹配度越高,荧光猝灭率越大。不同类型的表面活性剂之间的复配能明显提升荧光探针检测性能,当非离子/阴离子、非离子/阳离子型复配表面活性剂之间的复配比例分别为7∶3和1∶1时荧光猝灭率达到最大值,且均高于单一表面活性剂时的荧光猝灭率。这说明不同类型表面活性剂复配的最佳比例存在较大差异,但均有效地增强了受体与荧光体的分散性及自组装性能,提高了对Cu2+的检测性能。研究结果将为新型胶束自组装荧光探针的设计和应用提供数据参考。     

Role of the head group on the mixed micellization process in binary systems containing a sugar-based surfactant: decanoyl- N -methylglucamide

The mixed micelles of nonionic decanoyl-N-methylglucamide (MEGA-10) with the anionic sodium dodecyl sulphate (SDS), the cationic dodecyltrimetylammonium bromide (DTAB), and the nonionic octaoxyethylene monododecyl ether (C₁₂E₈) have been studied using the fluorescence probe technique. The critical micelle concentration of the three mixed systems in the whole composition range were determined by the pyrene 1:3 ratio method, and the experimental results were analysed in the context of the pseudophase separation model, by using the regular solution theory. It was found that the mixed micelles containing the anionic surfactant are more stable than the pure micelles. This fact was attributed to the occurrence of ion–dipole interactions between the head groups of the component surfactants in the mixed micelle. The static quenching method was used to determine the mean aggregation number of pure and mixed micelles. It was found that whereas mixed micelles containing SDS show a positive deviation from the ideal behaviour, those constituted by DTAB deviate negatively. This different tendency was interpreted on the basis of both steric and electrostatic interactions. The evolution of the microstructure of the mixed micelles upon the participation of the co-surfactant was followed through the micropolarity and microviscosity of the mixed systems. Although the micropolarity studies do not allow definite conclusions, the microviscosity assays indicate that the participation of the co-surfactant induces the formation of less ordered micelles, this effect being more pronounced in the case of mixtures with the anionic surfactant.     

Modulated photophysics of 2-anthracene sulphonate in micellar assembly

The association of a non-ionic surfactant of polyoxyethylene-p-(1,1,3,3-tetramethylbutyl)phenyl ether (Triton X) series with 2-AS in aqueous solution has been studied by means of steady-state, time-resolved fluorescence and fluorescence anisotropy techniques. The effect of the hydrophobic chain length on the structural dynamism of the fluorophore has been reported. Experimental results demonstrate that the equilibrium of this dynamism is sensitive to the environment. The association constant of the probe molecule with the non-ionic micelles of Triton X (TX), location of the probe in the micellar environment, have been determined from the change in emission characteristics of the probe as a function of surfactant concentration. The rate constant of quenching and mode of quenching of probe in micellar media have been ascertained. Quantitative estimates of the micropolarity at the binding sites of the probe molecule have been determined. Some of the environment-dependent relevant fluorescence parameters, fluorescence anisotropy (r), have been monitored for exploring the imposed motional restriction of the microenvironment around the probe. An attempt has been made to correlate the steady-state results with time resolved study.     

Total dissolved solids estimation with a fiber optic sensor of surface plasmon resonance

In this paper, surface plasmon spectra of ion influence was investigated by using a fabricated fiber optic sensors, then spectrum subtraction of ion and non-ionic solutions were developed for field applications of total dissolved solids (TDS) estimation. We confirmed the SPR spectral difference between seven ionic and three non-ionic liquid samples, that for the same refractive index, resonance wavelength in SPR spectrum is much higher for ionic samples than that in the case of non-ionic ones due to the ions influence. The positive correlation of ion content and extra resonance wavelength shift has been established for TDS estimation in water. With three groups of water samples investigation and field testing, the proposed SPR technique showed a good performance comparable to the conductivity method.     

Effect of Surfactant Type and Concentration on Surfactant Migration,Surface Tension,and Adhesion of Latex Films

The effect of surfactant type and concentration on the migration behavior of surfactant in a latex film was investigated. Two types of surfactant, including an anionic (sodium lauryl sulfate, SLS) and a non-ionic (nonylphenol ethoxylate, average number of ethylene oxide units = 40, NP-40) surfactant, were used in an emulsion polymerization of methyl methacrylate butyl acrylate copolymer (MMA–BA). The total amount of surfactant was varied in three levels, i.e., 1.5, 3, and 4.5 wt%, and the surfactants were used both pure and in a mixture state. The surfactant migration to the film–air (F–A) and film–substrate (F–S) interfaces of the latex films was determined by using an attenuated total reflection-Fourier transform infrared (ATR-FTIR) method. In addition, the adhesion of the latex films to glass substrates was measured by a pull-off test. The results showed that the migration of anionic surfactant to the interfaces was greater than the non-ionic one. It was also found that the use of non-ionic surfactant along with anionic surfactant could decrease the migration of the anionic surfactant to the interfaces.     

Comparison of the coating properties and corrosion rates in electroless Ni-P/PTFE composites prepared by different types of surfactants

The effects of the addition of three types of surfactants (cationic, anionic, non-ionic) at different concentrations in the plating bath on the deposition rate, PTFE content and surface morphology of electroless Ni-P/PTFE composite coatings were investigated. It was demonstrated that the cationic and non-ionic surfactants created a uniform distribution of PTFE particles in the coatings. The effects of the surfactant type and concentration on the corrosion properties of Ni-P/PTFE coatings were also studied. The corrosion resistance was increased by the incorporation of PTFE particles into the Ni-P matrix. The level of improvement depended largely on the type and concentration of the applied surfactants.     

Chemiluminescence of phthalhydrazide derivatives in organized media: Interactions with surfactants and cyclodextrins

The chemiluminescent oxidation of some phthalhydrazide derivatives, luminol (LUM), isoluminol (ISOL), N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), has been carried out in micellar media and in the presence of natural cyclodextrins (CDs), using Co(II) as catalyst and H₂O₂ as oxidant. The cationic cetyltrimethylammonium bromide (CTAB) and, in a lesser extent, the anionic sodium dodecyl sulfate (SDS) produce quenching in the chemiluminescence (CL) of all the luminophores at concentrations above the cmc, whereas slight enhancements are attained with the non-ionic pentaethylene glycol monododecyl ether (C₁₂E₅). On the contrary, the incorporation of the CDs to the reaction produces a remarkable intensification of the CL. Binding of the luminophores to the macrocycles and the micelles has been studied by Pulsed-Gradient-Spin-Echo-NMR (PGSE-NMR) and fluorescence anisotropy. The cationic CTAB decreases the emission mainly due to charge compensation as a result of the association of the luminophores and the luminescent intermediates to the micelles. The presence of the alkyl substituents of ABEI and AHEI provides an additional hydrophobic contribution to the binding process. SDS quenches this reaction as the micelles retain Co(II) on their anionic layer. The protection and stabilization of these luminophores or their luminescent intermediates provided by the cavities of the CDs make this family of cyclic oligosaccharides much more suitable agents than the surfactants for enhancing the CL in aqueous media for this specific reaction.     

Confined diffusion of hydrophilic probes inserted in lyotropic lamellar phases

The dynamic behaviour of three hydrophilic probes (two dyes and one fluorescently-labelled protein) inserted in the water layers of lyotropic lamellar phases has been studied by confocal fluorescence recovery experiments. Two different, ionic (AOT/NaCl/ H(2)O and non-ionic ( C(12)E(5) /hexanol/ H(2)O host systems were studied. The confinement effect has been carefully monitored using the swelling properties of the lamellar phases. In all cases, we measure the evolution of the probe diffusion coefficient in the layer plane D ( perpendicular) versus the separation between the membranes d(w). Depending on the composition of the lamellar phase, this distance can be continuously adjusted from 500A to about 20A. For all systems, we observe a first regime, called dilute regime, where the diffusion coefficient decreases almost linearly with 1/d (w) . In this regime, the Faxén theory for the friction coefficient of a spherical particle symmetrically dragged between two rigid walls can largely explain our results. More unexpectedly, when the membranes are non-ionic, and also quite flexible ( C(12)E(5) /hexanol in water), we observe the existence of a second, concentrated (or confined) regime, where the diffusion coefficient is nearly constant and different from zero for membrane separations smaller than the particle size. This new regime can be heuristically explained by simple arguments taking into account the membrane fluidity.     

Photophysics of 2-(4′-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylaminophenyl)imidazo[4,5-b]pyridine in Micelles: Selective Dual Fluorescence in Sodium dodecylsulphate and Triton X-100

The photophysical behavior of 2-(4′-N,N-dimethylaminophenyl)imidazo[4,5-b]pyridine (DMAPIP-b) has been studied in nonionic triton X-100 (TX-100), cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecylsulfate (SDS) micelles using steady state and time resolved fluorescence techniques. The molecule emits both normal and TICT fluorescence in SDS and TX-100 but emits only normal fluorescence in CTAB. This difference in behavior of the fluorophore is due to varying extent of hydrogen bonding experience by it in different micelles. Of the three possible monocations, only two kinds of monocations, MC1 (formed by protonation of pyridine ring nitrogen) and MC2 (formed by the protonation of imidazole nitrogen) are present in all the micelles (Scheme 1). DFT calculations performed on the monocations reveal that MC1 and MC2 are more stable than MC3, the monocation formed by the protonation of dimethylamino nitrogen.      

Investigation of the sign of the Soret coefficient in different ionic and surfacted magnetic colloids using forced Rayleigh scattering and single-beam Z -scan techniques

The sign of the Soret coefficient S T of a large set of ionic magnetic colloids (ionic ferrofluids (IFFs)) and surfacted magnetic colloids (surfacted ferrofluids (SFFs)) is determined using forced Rayleigh scattering and the single-beam Z -scan techniques. Different samples were investigated: acid and alkaline colloids with different values of pH; colloids with different concentrations of magnetic grains; colloids with grains of different typical diameters; colloids with magnetic grains with different coating natures; colloids with different non-polar and polar liquid carriers. Our results indicate that the sign of S T depends on the sign of the surface charge of grains in IFFs. In the case of water-based SFFs, the thermodiffusive behaviour is opposite to that of IFFs; that is, grains coated with a cationic surfactant behave like negatively charged IFF (alkaline) grains and grains coated with an anionic surfactant behave like positively charged IFF (acid) grains. SFFs with grains coated with non-ionic surfactants dispersed in non-polar fluid carriers behave like SFFs with grains coated with a cationic surfactant. The nature of the liquid carrier itself is not the only determinant factor, except apparently in the case of non-polar fluids, where only S T > 0 is found. These results cannot be explained with the available theories and it is highly probable that different mechanisms are present in the thermodiffusive behaviour of these complex fluids.     

Interactions of Nile Blue with Micelles, Reverse Micelles and a Genomic DNA

In this contribution we report studies on the nature of binding of a small ligand/drug Nile blue (NB) with sodium dodecyl sulfate (SDS) micelles, bis-(2-ethylehexyl) sulfosuccinate (AOT)/isooctane reverse micelles (RM) and a genomic DNA extracted from Salmon sperm. With detailed steady state and picosecond resolved optical spectroscopic techniques, we examined the fluorescence quenching of the ligand upon complexation with the SDS monomers and DNA. Polarization analyzed picosecond-resolved fluorescence measurements reveal geometrical restriction on the probe in SDS micelles, AOT-RM and DNA. Steady state and time resolved studies on the probe in nanocages of AOT RM with various degrees of hydration (w₀) reveal the existence of NB as two distinct species namely, neutral and cationic. This study confirms that the emission of NB in aqueous micelles and DNA solution is due to the cationic form of the drug. Our experiments clearly identified non-specific electrostatic and intercalative modes of interaction of the probe with the DNA at lower and higher DNA concentrations respectively. The nature of binding of NB in presence of the DNA and SDS micelles reveals that the binding affinity of the probe is higher with the micelles than with the DNA. The complex rigidity of NB with DNA and its fluorescence quenching with DNA elucidate a strong recognition mechanism between NB and DNA.     

Enhancement of the Fluorescence Quenching Efficiency of DPPH<Superscript>•</Superscript> on Colloidal Nanocrystalline Quantum Dots in Aqueous Micelles

Luminescent CdS quantum dots capped with thioglycolic acid (CdS-TGA QDs) were demonstrated to serve as a fluorescence probe for a model organic radical, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•), employing the quenching of the CdS-TGA QDs emission signal by the radical. Under the optimum conditions, the quenching efficiency of DPPH^• on CdS-TGA QDs was proportional to the concentration of DPPH^•, following Stern-Volmer relationship. Different types of surfactants (cationic, anionic and neutral surfactants) were introduced to CdS-TGA QDs in order to increase the detection sensitivity. The fluorescence intensity of CdS-TGA QDs was greatly enhanced by cationic and neutral surfactants. Moreover, the quenching efficiency of DPPH^• on the QDs in the presence of micelles was remarkably ca. 13 times higher than that in the system without micelles. Effects of pH and concentration of surfactants on the fluorescence quenching of CdS-TGA QDs were investigated. Electron spin resonance (ESR) spectroscopy was also used to monitor the DPPH radical species in CdS-TGA QDs mixtures with and without micelles. Fluorescence quenching mechanisms of CdS-TGA QDs by DPPH^• in the presence and in the absence of CTAB were proposed.     

Spectroscopic investigations on the interaction of an anionic probe with nonionic micelles of Igepal surfactants in aqueous media

The behaviour of the anionic dye 8-anilino-1-napthalenesulfonic acid ammonium salt, or ANS, in aqueous solutions containing the Igepal series of polyoxyethylene nonionic surfactants was investigated using fluorescence spectroscopic technique. The interactions of the dye with the nonionic surfactants were examined in micellar media, to prevent dye aggregate formation and to ensure maximum dye and surfactant interaction. From the relative fluorescence enhancements, binding constants of the dye to the surfactant micelles and aggregation numbers of the micelles were determined. The aggregation numbers were also separately determined by static fluorescence quenching of pyrene by cetylpyridinium chloride in aqueous surfactant mixtures at a fixed concentration of surfactant, and compared with the value obtained from the present investigation of the interaction of the micelles with the ANS probe. The values of binding constants, micropolarity values sensed by pyrene and the Stern–Volmer constants for quenching of pyrene fluorescence by cetylpyridinium chloride were correlated with the number of ethylene oxide groups in the Igepal series.     

Molecular dynamics study of the vibrational relaxation of OCl and OCl in the bulk and the surface of water and acetonitrile

The vibrational relaxation of OCl and OCl⁻ in the bulk and the liquid/vapor interface of water and acetonitrile is studied by molecular dynamics computer simulations. Both equilibrium calculations of the vibrational friction and non-equilibrium simulation of the energy relaxation are used to elucidate the factors that influence the rate of energy relaxation in systems that represent polar ionic and non-ionic solutes in polar protic and non-protic solvents. We find that, in agreement with previous experimental and theoretical studies, the relaxation of the ionic solute is much faster than that of the non-ionic solute in both the solvents. However, while the relaxation is slowed down considerably when the non-ionic solute is transferred from the bulk to the interface, no such surface effect is found in the case of the ionic solute. This behavior can be explained by noting that the ionic solute is able to keep its first solvation shell intact upon transfer to the interface and that the main contribution to the friction is due to the Lennard-Jones part of the intermolecular potential.     

Form-factors for different aggregation models of micelles

Spherical micelles in ionic micellar solutions, often aggregate to form spherical, cylindrical or chain-like aggregates on addition of salt to the solution. It is known that the technique of small angle neutron scattering (SANS) can be used to distinguish spherical and cylindrical aggregates. To examine if SANS can be used to distinguish the latter two aggregation processes, we have calculated the angular distribution of scattered neutrons from 0.002 M CTAB solutions. These calculations show that aggregation of CTAB micelles results in large changes in SANS spectra. The shapes of SANS spectra are different for the above three types of aggregates, suggesting that technique of SANS can indeed be used to distinguish the three aggregation processes. The size of the aggregate can also be obtained from such studies.     

Micelle induced generation of photovoltage using Fluorescein dye

Photovoltage generation using Fluorescein dye in aqueous and aqueous-micellar medium at different pH has been studied in photogalvanic cell. The photopotential and photocurrent generated were maximum in non-ionic micellar medium. The observed solar energy efficiency in non-ionic micellar medium, diethylene glycol hexadecyl ether (Brij-52) was 0.06% and maximum power of the cell was 15.5 μw. The output of the cell was sensitive to surfactant nature. The rate constants of the reactions during photovoltage growth and decay were calculated. The thermodynamic properties of the cell were also discussed. A comparison of the micelle induced photovoltage generation of anionic dye Fluorescein with cationic dye Safranine T in different micellar media and at different pH has been presented.     

Evidence of ionic adsorption on C12E6 non-ionic micellar solutions

Summary In this paper we present conductivity measurements on different concentrations of C₁₂E₆ non-ionic surfactant solutions as a function of temperature and buffer ionic strength. The experimental data were analysed by means of Looyenga equation. The isothermal slopes of the linearized Looyenga equation depend on the ionic strength, showing saturation effect. Our results indicate that one of the basic hypotheses of the mixture equations is not fulfilled. Adsorption of light ions at micellar interface is necessary to justify the experimental data. Then for non-ionic surfactant solutions the ion adsorption prevents any explicit computation of the micellar hydrated volume. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.