表面活性剂对共轭聚合物荧光性质及电荷转移的影响

探讨了表面活性剂存在下, 水溶性阴离子共轭聚合物聚[5-甲氧基-2-(3-磺酰化丙氧基)-1,4-苯撑乙烯](简写为MPS-PPV)的微环境变化对荧光性质及电荷转移的影响. 结果表明, 阳离子表面活性剂及非离子表面活性剂使MPS-PPV荧光增强, 阴离子表面活性剂使其荧光先增强后减弱; 在MPS-PPV/表面活性剂体系中加入电子接受体Pd^2＋, 发现非离子表面活性剂体系的荧光猝灭效率提高, 阴离子及阳离子表面活性剂体系荧光猝灭效率下降. 此研究对研制基于阴离子共聚物的新型生物化学传感器具有一定的指导意义.     

水杨酸-2′-乙基己基酯在胶束中的增溶位点

考察了阳离子、非离子和阴离子表面活性剂存在下水杨酸-2′-乙基己基酯(EHS)的吸收光谱和激发态分子内质子转移(ESIPT)荧光光谱.结果表明,EHS可增溶在胶束中,2′-乙基己基碳链朝向胶束内核,而水杨酸基朝向胶束-水界面;胶柬环境有利于EHS分子对紫外光的吸收和分子内氢键的形成,从而使ESIPT荧光显著增强,激发态分子以发射可见光和非辐射去活化方式衰减;并根据EHS和表面活性剂分子的结构和大小,解释了EHS分子在胶束中的结合位点,荧光猝灭和酯水解的光谱测量进一步为此结合位点提供了佐证.     

水杨酸-2’-乙基己基酯在胶束中的增溶位点

考察了阳离子、非离子和阴离子表面活性剂存在下水杨酸-2’-乙基己基酯(EHS)的吸收光谱和激发态分子内质子转移(ESIPT)荧光光谱. 结果表明, EHS可增溶在胶束中, 2’-乙基己基碳链朝向胶束内核, 而水杨酸基朝向胶束-水界面; 胶束环境有利于EHS分子对紫外光的吸收和分子内氢键的形成, 从而使ESIPT 荧光显著增强, 激发态分子以发射可见光和非辐射去活化方式衰减; 并根据EHS和表面活性剂分子的结构和大小, 解释了EHS分子在胶束中的结合位点, 荧光猝灭和酯水解的光谱测量进一步为此结合位点提供了佐证.     

新型近红外试剂的合成及其现场二聚体与DNA作用的研究

合成了一种新型近红外阴离子染料,并对其水溶液及阳离子表面活性剂ＣＴＡＢ存在下的吸收荧光光谱进行了研究。结果表明,低浓度的ＣＴＡＢ与该近红外阴离子染料形成离子缔合物而使阴离子染料的荧光强度降低,当ＣＴＡＢ的浓度进一步加大时,其胶束前预聚集促使该染料形成非荧光二聚体,导致荧光急剧猝灭。     

稳态荧光猝灭法确定胶束聚集数的研究

选用芘作为荧光探针, 二苯酮作为猝灭剂, 以稳态荧光猝灭法测定了十二烷基硫酸钠、十二烷基磺酸钠和十六烷基三甲基演化铵的胶束聚集致, 并对其测定胶束聚集数方法的有效范围进行了讨论. 实验结果表明, 选择的探针-猝灭剂体系适用于稳态荧光猝灭法确定阴离子和阳离子表面活性剂的胶束浓度和聚集数.     

阳离子表面活性剂与曙红Y的荧光反应及其分析应用

研究阳离子表面活性剂(CSAA)在水溶液中与曙红Y的荧光反应, 发现当CSAA单体与曙红Y形成离子缔合物时, 荧光发生猝灭, 而CSAA胶束与曙红Y作用又会出现一个新的、更强的荧光。荧光猝灭反应具有很高的灵敏度, 对于不同的CSAA, 其检测限在6.6-12.0ng/mL之间, 可用于痕量CSAA的测定。此外, 荧光猝灭和新荧光的产生也为研究表面活性剂和荧光染料在溶液中的存在状态提供了新的途径。还研究了反应体系的荧光特征、适宜条件并讨论了反应机理。     

阳离子表面活性剂与曙红Y的荧光反应及其分析应用

研究阳离子表面活性剂(CSAA)在水溶液中与曙红Y的荧光反应,发现当CSAA单体与曙红Y形成离子缔合物时,荧光发生猝灭,而CSAA胶束与曙红Y作用又会出现一个新的、更强的荧光.荧光猝灭反应具有很高的灵敏度,对于不同的CSAA,其检测限在6.6～12.0ng/mL之间,可用于痕量CSAA的测定.此外,荧光猝灭和新荧光的产生也为研究表面活性剂和荧光染料在溶液中的存在状态提供了新的途径.还研究了反应体系的荧光特征、适宜条件并讨论了反应机理.     

碳纳米管与CTMAB协同加强荧光探针并应用于测定痕量锰

提出将碳纳米管(CNT)作为一种新型分析增效试剂用于加强荧光探针,研究了其与阳离子表面活性剂-十六烷基溴化铵(CTMAB)的协同增敏机理,并应用于苯基荧光酮(PF)荧光猝灭法测定锰离子的体系中。结果表明,在CNT与CTMAB复配的影响下,PF与Mn2+形成的络合物荧光猝灭强度最大,据此建立了CNT加强荧光猝灭法测定痕量锰的新方法。方法的检出限为0.2μg/L,线性范围为0.4~10μg/L,回归方程:ΔF=10.48ρ(μg/L)+10.77,R=0.9992。本法可用于自来水中Mn2+含量的检测。     

水溶性荧光聚合物用于测定聚赖氨酸

合成了一种水溶性荧光聚合物聚[5-甲氧基-2-(3-磺酰化丙氧基)-1,4-苯撑乙烯](MPS-PPV),对该聚合物进行了元素分析、红外光谱及透射电子显微镜表征.实验结果表明,聚赖氨酸(PLL)对该聚合物荧光具有明显的猝灭作用,据此建立了一种快速灵敏测定聚赖氨酸的新方法,检出限为5.0×10^-10mol/L.探讨了聚赖氨酸猝灭MPS-PPV荧光的机理.     

离子型表面活性剂在水溶液中的分子构型

本文利用表面活性剂分子中内在的荧光探针及外加荧光探针,研究了离子型表面活性剂分子在水溶液中的构型,烷基三苯基鱗盐及N-烷基吡啶盐对芘的单体荧光猝灭服从Stern-Volmer方程,是扩散控制的碰撞猝灭,但不同链长的猝灭剂的荧光猝灭行为呈反常状态,即链越长,猝灭速率常数越大,在十六烷基三甲基铵(CTMAB)水溶液中观察到了芘的激基缔合物荧光,同时观察到了CTMAB对芘的荧光猝灭的阻碍(阳离子猝灭剂)和促进(阴离子猝灭剂)作用,提出离子型表面活性剂在水溶液中呈绕曲状的分子构型,且是一种动态构型。     

New fluorescence method for the determination of the critical micelle concentration by photosensitive monoazacryptand derivatives

A novel fluorescence method for the determination of the critical micelle concentration (cmc) is reported. The cmc values of nonionic and anionic surfactants were evaluated utilizing a photosensitive monoazacryptand-Ba2+ complex, whose fluorescence intensity is sensitively changed by environmental conditions based on the photoinduced electron transfer (PET) mechanism as a fluorescent probe (PET method). Based on a comparison of the cmc values obtained by the PET method versus those obtained by conventional fluorescence-based methods as well as the values reported in the literature, one can conclude that the PET method is useful for the cmc determination. In particular, the PET method was more effective for the cmc determination of nonionic surfactants with very low cmc values (< 10(-5) M) than any other fluorescence-based method. In the cases of anionic surfactants, the PET method revealed the formation of the premicellar aggregates comprised of surfactant molecules and fluorescent probes below the cmc. Moreover, the hydrophobicity around the monoazacryptand-Ba2+ complex incorporated into various nonionic surfactant micelles was evaluated by this PET method.     

Enhanced conjugated polymer fluorescence quenching by dipyridinium-based quenchers in the presence of surfactant

Poly[(2-methoxy-5-propyloxysulfonate)phenylene vinylene] (MPS-PPV) was synthesized directly from its bischloromethylated monomer, considerably reducing the total number of steps involved in the polymer preparation. For the first time, a simple technique of ultracentrifugation was employed for final purification of the polymer. The interactions among the polymer, surfactant, and quencher molecules, as well as amplified fluorescence quenching and fluorescence enhancement associated with the interactions, were investigated and discussed. When compared with methyl viologen [MV]2+, higher values of Stern-Volmer constant K(SV) values on the order of > or =10(7) M(-1) were observed for the newly synthesized N-(2-carboxyhexadecanoyl)-N'-methyl-4,4'-bipyridinium iodide bromide ([CHMB]2+) quencher in the presence of 1,2-dioleoyl-3- trimethylammonium propane (DOTAP) surfactant. Comparisons of surfactants demonstrated that the K(SV) of [CHMB]2+ was 10-fold higher in the presence of dodecyltrimethylammonium bromide (DTAB) surfactant than with DOTAP. Polymer fluorescence was totally recovered upon addition of DOTAP surfactant to a MV-quenched polymer system, whereas only 50% of fluorescence was recovered upon addition of DOTAP surfactant to the CHMB-quenched polymer solution. In contrast, no fluorescence was recovered when DTAB was added to either the MV- or CHMB-quenched polymer systems. Thus, fluorescence enhancement was observed for the polymer complex with DOTAP, whereas fluorescence quenching was predominant in the polymer complex with DTAB. Such studies will not only help to better understand the intrinsic properties of the ionic conjugated polymer and amplified fluorescence quenching and enhancement but also provide guidelines to develop the next generation of ionic conjugated-polymer-based biosensors.     

Micellar-enhanced ultrafiltration of cadmium ions with anionic–nonionic surfactants

Micellar-enhanced ultrafiltration (MEUF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The micellar-enhanced ultrafiltration of cadmium from aqueous solution was studied in systems of anionic surfactant and mixed anionic/nonionic surfactants. The micelle sizes and zeta potentials were investigated by dynamic light scattering measurements. The effects of feed surfactant concentration, cadmium concentration and the molar ratio of nonionic surfactants to sodium dodecyl sulfate (SDS) on the cadmium removal efficiency, the rejection of SDS and nonionic surfactants and the permeate flux were investigated. The rejection efficiencies of cadmium in the MEUF operation were enhanced with higher SDS concentration and moderate Cd concentration. When SDS concentration was fixed at 3 mM, the optimal ranges of the molar ratios of nonionic surfactants to SDS for the removal of cadmium were 0.4–0.7 for Brij 35 and 0.5–0.7 for Triton X-100, respectively. With the addition of nonionic surfactants, the SDS dosage and the SDS concentration in the permeate were reduced efficiently.     

SOLUBILIZATION IN MIXED REVERSE MICELLAR SYSTEMS OF AOT/NONIONIC SURFACTANTS/n-HEPTANE

Solubilization of water and aqueous NaCl solutions in mixed reverse micellar systems of anionic surfactant AOT and nonionic surfactants in n-heptane was studied. It was found that the maximum solubilization capacity of water was higher in the presence of certain concentrations of NaCl electrolyte, and these concentrations increased with the increase of nonionic surfactant content and their EO chain length. Soluibilization capacity was enhanced by mixing AOT with nonionic surfactants. The observed phenomena were interpreted in terms of the stability of the interfacial film of reverse micellar microdroplet and the packing parameter of the surfactant that formed mixed reverse micelles.     

Fluorescence probing of albumin-surfactant interaction

Protein-surfactant interactions were studied using bovine serum albumin (BSA) and the three surfactants sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and poly(oxyethylene)isooctyl phenyl ether (TX-100). The surfactants used belong to three broad classes, i.e., anionic, cationic, and nonionic. These categories of surfactants were used to elucidate the mechanism of surfactant binding to BSA, at pH 7. The interactions were followed fluorimetrically using both intrinsic tryptophan (Trp) fluorescence and the fluorescence of an external label. The aggregation behavior of the surfactants were studied in the presence of BSA. Steady-state fluorescence studies indicate that all three surfactants bind to BSA in a cooperative manner. This cooperative binding affects the binding of the external label to BSA. All these effects are also manifested in time-resolved fluorescence studies. The effects of surfactants on acrylamide quenching and energy transfer from Trp in BSA to bound dye provided valuable insights into the structural modification of BSA in presence of surfactants. The surfactant-induced conformational change of BSA was also confirmed by circular dichroism studies. However, among the three categories of surfactants, the nonionic surfactant shows the least interaction with BSA.     

Sensitivity Enhancement of the Fluorometric Determination of Aluminum by the Use of Surfactant

Abstract

The effects of surfactants on fluorescence analysis were studied. The addition of surfactants to a metal complex solution causes a remarkable enhancement of fluorescence. By means of such phenomenon the sensitivity of the fluorometric determination of aluminum was increased about six-fold over conventional methods. From the stability of the chelate complex in the presence of surfactant and the degree of enhancement of fluorescence, the nonionic surfactant was judged to be the most useful of the types of surfactants: cationic, anionic and nonionic. An ultramicro amount of aluminum, 5 × 10^?10 g Al/ml, could be determined by the proposed method.     

Effect of Surfactants on the Formation,Morphology, and Surface Property of Synthesized SiO2 Nanoparticles

Abstract

This study investigated the effect of cationic, anionic (saturated and unsaturated), and nonionic surfactants on the formation, morphology, and surface properties of silica nanoparticles synthesized by the ammonium‐catalyzed hydrolysis of tetraethoxysilane in alcoholic media. Results indicate that at a relatively low surfactant concentration (1 × 10^?3–1 × 10^?6 M), cationic surfactants significantly affected the growth of silica particles as measured by dynamic light scattering and transmission electron microscopic analyses. In contrast, the anionic and nonionic surfactants showed relatively minor effects in the low concentration range. The magnitude of negative zeta potential was reduced for silica colloids that were synthesized in the presence of cationic surfactant because of charge neutralization. The presence of anionic surfactants only slightly increased the negative zeta potential while the nonionic surfactant showed no obvious effects. At high surfactant concentrations (>1 × 10^?3 M), cationic and anionic surfactants both induced colloid aggregation, while the nonionic surfactant showed no effect on particle size. Raman spectroscopic analysis suggests that molecules of cationic surfactants adsorb on silica surfaces via head groups, aided by favorable electrostatic attraction, while molecules of anionic and nonionic surfactants adsorb via their hydrophobic tails.     

Electrophoretic behaviour and viscosities of metal oxides in mixed surfactant systems

 The electrokinetic behavior and viscosity of anatase and alumina in mixed-surfactant solutions were investigated. Sodium dodecylsulfate and nonionic polyoxyethylene ethers were investigated as model surfactants. Pure nonionic surfactants adsorbed on anatase and coated the particles, so that the zeta potential was nearly zero near the critical micelle concentration of surfactant. At higher surfactant concentrations, an increase in the zeta potentials was observed, suggesting a change in the microstructure of the adsorbed layer. Addition of nonionic surfactant to positively charged anatase and alumina with some preadsorbed sodium dodecylsulfate reversed the surface charge of the oxide to negative, indicating enhanced coadsorption of the anionic surfactant. At higher concentrations of the nonionic surfactant, the charge reversed back to positive. Nonionic surfactants did not reverse the surface charge of these oxides in the absence of the anionic surfactant. Coenhanced adsorption of nonionic and anionic surfactants was used to stabilize alumina at the isoelectric point, where neither surfactant adsorbed appreciably on its own. These results suggest a dramatic change in conformation of the surfactant chains in mixed systems. Further explanation and justification of the proposed changes in adsorbed surfactant conformation require spectroscopic evidence. Received: 12 March 1997 Accepted: 22 July 1997     

Interplay of electrostatic and hydrophobic effects with binding of cationic gemini surfactants and a conjugated polyanion: experimental and molecular modeling studies

Understanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}copolymer (PBS-PFP) and cationic gemini surfactants alpha,omega-(CmH2m+1N+(CH3)2)2(CH2)s(Br-)2 (m-s-m; m=12, s=2, 3, 5, 6, 10, and 12) has been studied experimentally in aqueous solution. These surfactants are chosen to see whether molecular recognition and self-assembly occurs between the oppositely charged conjugated polyelectrolyte and gemini surfactant when the spacer length on the surfactant is similar to the intercharge separation on the polymer. Without surfactants, PBS-PFP exists as aggregates. These are broken up upon addition of gemini surfactants. However, as anticipated, the behavior strongly depends upon spacer length (s). Fluorescence measurements show three surfactant concentration regimes: At low concentrations (<2x10(-6) M) quenching occurs and is most marked with the small spacer 12-2-12; at intermediate concentrations (approximately 2x10(-6)-10(-3) M), fluorescence intensity is constant, with a 12-carbon spacer 12-12-12 showing the strongest fluorescence; above the critical micelle concentration (CMC; approximately 10(-3) M) increases in emission intensity are seen in all cases and are largest with the intermediate spacers 12-5-12 and 12-6-12, where the spacer length most closely matches the distance between monomer units on the polymer. With longer spacer length surfactants, surface tension measurements for concentrations below the CMC reveal the presence of polymer-surfactant aggregates at the air-water interface, possibly reflecting increased hydrophobicity. Above the CMC, small-angle neutron scattering experiments for the 12-6-12 system show the presence of spherical aggregates, both for the pure surfactant and for polyelectrolyte/gemini mixtures. Molecular dynamics simulations help rationalize these observations and show that there is a very fine balance between electrostatic and hydrophobic interactions. With the shortest spacer 12-2-12, Coulombic interactions are dominant, while for the longest spacer 12-12-12 the driving force involves hydrophobic interactions. Qualitatively, with the intermediate 12-5-12 and 12-6-12 systems, the optimum balance is observed between Coulombic and hydrophobic interactions, explaining their strong fluorescence enhancement.     

混合反胶束的电导与微结构研究

反胶束是两亲分子在非极性溶剂中形成的一种有序组合体，在医药、化工、采油、胶束催化及酶催化等领域中有重要应用．与胶束溶液相比，人们对反胶束的形成与结构的了解至今仍不充分．特别是对于由混合表面活性剂形成的反胶束的研究几乎无人涉及．本文采用动态光散射、电导及荧光光谱等手段对阴离子表面活性剂AOT与非离子表面活性剂形成的混合反胶束进行了研究，旨在探讨利用表面活性剂的复配来调节和控制反胶束的结构和性能．亚实验部分二异辛基磺化琉璃酸钠（AOT，Sigma公司）；Brij30为含4个氧乙烯基（EO基）的十二碳醇（AcrosOrgani…