Search

The interaction between biological surfactant sodium deoxycholate (NaDC) and nonionic surfactants polyoxyethylene (n) nonylphenol ether (NPn) for the formation of micelles in aqueous solution were investigated. Surface tension, interfacial dilational viscoelasticity, and transmission electron microscopy (TEM) were characterized to systematically study the interaction between NaDC and NPn in buffer solution. At last, the mechanism of the interaction between NPn and NaDC were analyzed. The surface tension results show that the interaction between NaDC and NPn was displayed synergism action. The composition of the mixed systems has been estimated on account of the regular solution theory, Clint's equation, Rubingh theory and Rosen theory. The surface dilational rheology provided abundant effective information on the feature of adsorbed layers. From the oscillating barrier measurements, the peak values of the dilational modulus moved to lower concentrations in NaDC/NPn binary system compared to single surfactant. The dilational elasticity of the binary system decreased distinctly on the basis of the rigid structure of NaDC. The interaction of these two substances was proved directly by TEM images, that the boundaries of the aggregates are clearer due to the protection of NPn molecules. The new complex systems have potential application in environmental protection. Schematic illustration of the aggregation in NPn/NaDC mixed systems and concentration increased from left to right. [ABSTRACT FROM AUTHOR]

In this article, a sensitive and selective turn-off fluorescence chemosensor, Tyloxapol (one kind of water soluble oligomer), was developed for the label-free detection of Fe 3+ ions in aqueous solution. Fluorescence (FL) experiments demonstrated that Tyloxapol was a sensitive and selective fluorescence sensor for the detection of Fe 3+ directly in water over a wide range of metal cations including Na + , K + , Ag + , Hg 2+ , Cd 2+ , Co 2+ , Cu 2+ , Cr 3+ , Mn 2+ , Ba 2+ , Zn 2+ , Ni 2+ , Mg 2+ , Ca 2+ , and Pb 2+ . Moreover, the fluorescence intensity of Tyloxapol has shown a linear response to Fe 3+ in the concentration range of 0–100 μmol L −1 with a detection limit of 2.2 μmol L −1 in aqueous solution. Next, based on a competition mechanism, another turn-on sensing application of the Tyloxapol/Fe 3+ platform to probe dopamine (DA) against various other biological molecules such as other neurotransmitters or amino acids (norepinephrine bitartrate, acetylcholine chloride, alanine, valine, phenylalanine, tyrosine, leucine, glycine, histidine) were also investigated. It is expected that our strategy may offer a new approach for developing simple, cost-effective, rapid and sensitive sensors in biological and environmental applications. [ABSTRACT FROM AUTHOR]

Surface tension, fluorescence and circular dichroism (CD) methods have been used to investigate the interaction between a biological surfactant sodium deoxycholate (NaDC) and proteins including bovine serum albumin (BSA) and gelatin. It can be seen from the surface tension measurements that both NaDC/BSA and NaDC/gelatin systems can form complexes and the ability of NaDC/BSA to lower surface tension is more obvious than that of NaDC/gelatin. The formation of the complexes influences not only the polarity of the microenvironment of the systems but also their fluorescence spectra. The far-UV CD spectra shows that the α-helical network of BSA increases first and then decreases as the concentration of NaDC increases, while the random coil content of gelatin always increases. A model of interaction between protein and NaDC influenced by the concentration of NaDC has been brought out based on the data gained from this study. [ABSTRACT FROM AUTHOR]

Silicone surfactants favor spreading at interfaces and siloxane has strong interaction with carbon nanotubes (CNT), thus silicone surfactant may be a good dispersant of CNT. Here, four silicone surfactants (named S1E19, S2E38, S2E16 and S1E16P8) were used to disperse CNT in aqueous solutions. The effects of surfactant structure and concentration on the ability at dispersing CNT were considered. All of the four silicone surfactants can disperse CNT in aqueous solution and the sample with 1,000 mg L S1E16P8 was the best one. The hydrophilic group polyoxyethylene (PEO) and the hydrophobic groups siloxane and polypropylene (PPO) are crucial factors in the ability of dispersing CNT. S2E38 with more ethylene oxide (EO) groups has a stronger ability to disperse CNT than S2E16. The dispersion system provided by S1E19 which contains fewer siloxane and EO groups is relatively unstable and disperses less CNT. These experimental results are explained by molecular dynamics simulation. S2E38 compared with S1E19 and S2E16 has stronger interactions with CNT. The interaction energy of CNT with S1E16P8 which has a PPO moiety but fewer siloxane groups is close to that of S2E16. Furthermore, it can be concluded that these four surfactants are adsorbed on CNT mainly by van der Waals forces and the Si-O-Si chain of silicon surfactant was flexible due to the long Si-C bond and it could easily wrap onto the surface of CNT through hydrophobic and other intermolecular interactions. The hydrophilic part of PEO helped the CNT dispersed in the aqueous solution and prevented CNT from aggregating in water through steric stabilization. [ABSTRACT FROM AUTHOR]

The interaction between an ethoxylated alkylphenol polymer with formaldehyde (EAPPF) and a triblock polyEO-polyPO-polyEO copolymer (TBCP) in aqueous solutions has been investigated in detail by means of surface tension, steady-state fluorescence, dynamic light scattering (DLS) measurements and computer simulations. For comparison, the ethoxylated alkylphenol oligomer (EAPO), which is the monomer unit of EAPPF, and another nonionic water-soluble polymer PEG were also selected to get more information about the interaction between different types of surfactants and polymers. The surface properties of mixed systems at the air/water surface were evaluated from surface tension measurements. Information about the hydrophobic microenvironment and size of the aggregates was obtained from steady-state fluorescence using pyrene as a hydrophobic probe and DLS measurements, respectively. The dissipative particle dynamics simulation method was applied to simulate the interaction between EAPPF (or EAPO) and TBCP (or PEG) in aqueous solutions. The synergetic interaction between EAPPF (or EAPO) and TBCP in binary mixed solution enhanced the adsorption of surfactant molecules (EAPPF or EAPO) at the interface, while no obvious interaction between EAPPF (or EAPO) and PEG was observed. [ABSTRACT FROM AUTHOR]

A water-in-oil microemulsion was prepared by using nonionic surfactant Triton X-100, 1-hexanol, cyclohexane and AgNO3 aqueous solution with a concentration of 0.2 mol L−1. Successive addition of sodium borohydride (NaBH4), ammonium hydroxide (NH3·H2O) and tetraethyl orthosilicate (TEOS) to this microemulsion leads to the formation of hierarchically-organized Ag@SiO2 hybrid nanoparticles with Ag nanocrystals randomly distributed inside amorphous SiO2, as proved by transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM) observations. In many cases, H2 gas bubbles, which were produced during the reduction of Ag+, were found to influence the structures of Ag nanocrystals. The morphologies of the hybrid nanoparticles and the H2-induced cavities can be easily tuned by the molar ratio of AgNO3 to NaBH4 and the volume ratio of AgNO3 aqueous solution to TEOS. Embedded in amorphous SiO2, the Ag nanoparticles are highly stable, while the unprotected Ag nanocrystals underwent fast aggregation. The inner Ag nanocrystals have dominant (111) planes and are optically active, as shown by X-ray powder diffraction (XRD) and UV-vis measurement, respectively. These properties make these Ag@SiO2 hybrid nanoparticles fascinating candidates for a variety of applications in catalysis and life science. [ABSTRACT FROM AUTHOR]

Copper nanoclusters (Cu-NCs), as a luminescent material, have received widespread attention due to their low cost, non-toxicity and excellent biocompatibility. However, research on the preparation of stable dispersions containing hydrophobic Cu-NCs are rare because of its difficulty to achieve. In this work, by the help of polyoxometalates (Na 9 [EuW 10 O 36 ]·32 H 2 O, EuW 10), atomically precise Cu-NCs (Cu 4 I 4 clusters, the ligand is triphenylphosphine (PPh 3)) was successfully introduced into water in the presence of co-solvent (dimethylsulfoxide, DMSO) to form stable dispersions. This strategy makes the dispersions to achieve aggregation-induced luminescence (AIE) with a high absolute quantum yield of 19.34 % and also greatly improve the stability of the hydrophobic Cu 4 I 4 clusters in the water system. One reason is that the copperophilic interaction between Cu 4 I 4 clusters leads to the high compactness of the assembly and suppresses the intramolecular vibrations and rotations of the Cu 4 I 4 clusters ligands which induced the AIE phenomenon; another reason is that the hydrophobic interaction between the hydrophobic part of EuW 10 and the peripheral ligands of Cu 4 I 4 clusters and the solvation of EuW 10 with the mixed solvent make the Cu 4 I 4 clusters disperse stably in the mixed system. Furthermore, Cu 4 I 4 clusters/EuW 10 stable dispersions can be used for Fe3+ sensing. The results indicated that the dispersion has good recognition ability, and high selectivity with a low detection limit of 40.34 nM for Fe3+. Our strategy of combining polyoxometalates with hydrophobic Cu-NCs to construct AIE systems in mixed solvents is expected to provide new insights into the development of biological probe, bioimaging, catalytic and sensitive sensors for environmental applications such as metal ion detection. [Display omitted] [ABSTRACT FROM AUTHOR]

A water-in-oil (W/O) microemulsion was prepared by mixing cyclohexane and HAuCl 4 aqueous solution at the presence of a nonionic surfactant Triton X-100 and 1-hexanol. By successively adding sodium borohydride (NaBH 4 ), ammonium hydroxide (NH 3 ·H 2 O) and tetraethyl orthosilicate (TEOS) to this microemulsion, Au@SiO 2 hybrid nanoparticles were produced which have been fully characterized by transmission electron microscopy (TEM) and high resolution TEM (HR-TEM) observations, UV–vis measurements and thermo gravimetric analysis (TGA). It was found that in each Au@SiO 2 hybrid nanoparticle, the silica shell can encapsulate multiple Au nanodots. The parameters of the Au@SiO 2 hybrid nanoparticles including the thickness of the silica shell, the number of encapsulated Au nanodots and the size of the nanoparticles can be easily tuned by changing the volume of TEOS and the reaction time before adding TEOS, respectively. These interesting core–shell nanoparticles provide ideal candidates for a variety of applications in materials science, biology and catalysis. [ABSTRACT FROM AUTHOR]