Multistimuli responsive micelles formed by a tetrathiafulvalene-functionalized amphiphile

An electroactive tetrathiafulvalene (TTF)-functionalized amphiphile 1 was designed and synthesized to investigate its self-assembling behavior in water. Dynamic light scattering (DLS), (1)H NMR, fluorescence spectrum, and cryogenic transmission electron microscopy (cryo-TEM) studies revealed that amphiphile 1 can form micelle-like aggregates via direct dissolution into water, and the micellar architectures could be disrupted either by addition of chemical oxidant Fe(ClO(4))(3) or by complexation with electron-deficient cyclobis(paraquat-p-phenylene) tetracation cyclophane (CBPQT(4+)) to release encapsulated hydrophobic dye Nile Red from the interior of micelles.     

Gelation of organic solvents by N-(n-tetradecylcarbamoyl)-l-amino acids

A series of N-(n-alkylcarbamoyl)-l-amino acid amphiphiles with different amino acid head groups were designed and synthesised. The gelation abilities of these amphiphilic molecules were studied in toluene and p-xylene solvents. The hypothesis that steric crowding at the chiral head group destroys gelation ability of the amphiphile was examined. Indeed, beside l-alanine-based amphiphile, only l-serine and l-aspartic acid derivatives were found to gelate the organic liquids efficiently in the presence of a small quantity of water. The gels were characterised by a number of methods, including FT-IR, NMR and X-ray diffraction spectroscopy, scanning electron microscopy (SEM) and rheology. The SEM micrographs revealed three-dimensional networks of ribbon-like aggregates. The organogels were observed to be thermo-reversible in nature and have sufficient mechanical strength. The gels have gel-to-sol transition temperatures above the physiological temperature (310 K).     

Alkyl chain order in a lamellar lyotropic liquid crystal with varying surface charge density

Abstract

The alkyl chain order in the lamellar liquid-crystalline phase formed in the octylamine/octylammonium chloride/water system has been investigated by ²H N.M.R. at constant mole ratio water/amphiphile and varying charge of the lamellae. The results are correlated to the dimensions of the aggregate obtained from X-ray low angle diffraction measurements.     

Multi-responsive cyclodextrin vesicles assembled by ‘supramolecular bola-amphiphiles’

Multi-responsive cyclodextrin vesicles (CDVs) self-assembled by ‘supramolecular bola-amphiphiles’, consisting of a guest (N,N′-bis(ferrocenylmethylene)-diaminohexane, 1) and a host (γ-hydroxybutyric-β-cyclodextrin, γ-HB-β-CD), were prepared and investigated for the first time. The morphologies and sizes of these novel vesicles in water were observed by transmission electron microscopy (TEM), scanning electron microscopy and dynamic light scattering. The effects of the host–guest ratio, the concentration and the solvent composition are also discussed. The host–guest interactions, complex stoichiometry and structures of 1·γ-HB-β-CD in water were investigated by cyclic voltammetry, UV and NMR spectroscopy. According to the complex stoichiometry, TEM observations and Chem3D estimation, the ‘supramolecular bola-amphiphiles’, made from 1·γ-HB-β-CD and assumed for the first time, formed the membranes of the CDVs. The CDV system was responsive to an oxidising agent, which is the first report on redox-responsive systems in this field. The CDVs are also responsive to pH and the presence of metal ions, such that they disassemble upon addition of acetic acid or Cu²⁺ ions, providing possible routes to drug delivery systems.     

NMR self-diffusion measurements in inverse micellar cubic phases

Abstract

We have measured self-diffusion coefficients of amphiphile and water molecules in novel inverse micellar lyotropic cubic phases using the pulsed field gradient NMR technique. We investigated two different ternary lyotropic systems: oleic acid/sodium oleate/water, and dioleoylglycerol/dioleoylphosphatidylcholine/water. Both of these systems have previously been shown by one of us to form a cubic phase of space group Fd3m, whose structure is a complex packing of two types of disconnected quasi-spherical inverse micelles embedded in a 3D hydrocarbon matrix. The amphiphile translational diffusion coefficients determined for the first time by ¹H NMR in both systems are surprisingly large. Thus the self diffusion coefficients of amphiphiles may not provide a reliable way of distinguising inverse micellar from inverse bicontinuous phases. The water self-diffusion coefficient has been determined to have a value of 2·4 × 10^?12 m² s^?1, a value which is more than two orders of magnitude lower than that typically observed for inverse bicontinuous cubic phases. This confirms unambiguously the inverse micellar topology of the Fd3m cubic phase, and indicates that the value of the water diffusion coefficient should permit inverse micellar and inverse bicontinuous structures to be reliably distinguished, even for systems where the structure has not been previously determined by diffraction.     

Supramolecular assembly of a succinyl-calix[4]arene derivative in multilamellar vesicles

Abstract

Amphiphilic calixarenes are interesting building blocks with high propensity to assemble in well-defined supramolecular architectures. In this work, we report that a succinyl-calix[4]arene derivative (2), exposing four terminal carboxylic acid groups at the calixarene upper rim and four dodecyl chains at the lower rim, forms discrete and stable nanoaggregates in aqueous medium. Field-emission scanning electron microscopy and transmission electron microscopy images showed that the aggregates of 2 possess a spherical shape and a vesicular structure with a multilamellar wall. The vesicular nature was confirmed by encapsulation of a hydrophilic dye rhodamine B. A preliminary study also evidenced that compound 2 increases water solubility of a hydrophobic drug such as curcumin.     

The first liquid crystalline diol compound which exhibits nematic,smecticA +, and smecticC + mesophases in the presence of water

A new amphiphilic ethane-1,2-diol derivative with a rodlike 2-phenylpyrimidine rigid core has been synthesized. From the combined results of differential scanning calorimetry and optical polarization microscopy a phase diagram amphiphile/water was constructed. The system exhibits a nematic phase at a very low water content, a smecticA ⁺ and a smecticC ⁺ phase at higher water concentrations. Such a phase sequence has been found for a lyotrophic system for the first time.     

合成双分子膜的研究（Ⅱ）：HBBTAB的合成及其在水溶液中的自组织行为

1977年Kunitake等首次报道了双十二烷基二甲基溴化铵在水溶液中自组织成类似于卵磷脂双层结构的囊泡,泡壁即为双分子膜。该发现表明可以用人工合成方法建造仿生组织,开辟了合成双分子膜研究的新领域。单链两亲性成膜物质,一般由亲水基团、间链、刚性生色基和尾链4部分组成。本文报道4-(4′-十六烷氧基-4-联苯氧基)丁基三甲基溴化铵     

Sonochemical synthesis of a novel nanorod diaqua(pyridine-2,6-dicarboxylato)copper(II) 3-D supramolecular network: new precursor to prepare pure phase nanosized copper(II) oxide

A nanosized copper(II) supramolecular compound, [Cu(dipic)(H₂O)₂] _n (1) [dipic?=?2,6-pyridinedicarboxylate], has been synthesized by sonochemical method and characterized by elemental analysis, scanning electron microscopy, X-ray powder diffraction, IR spectroscopy, TGA/DTA, and BET surface area studies. The structure of single crystalline 1 developed from nanosized 1 has been determined by X-ray crystallography and further characterized by scanning electron microscopy, TGA/DTA, and BET surface area studies. The XRD studies reveal that nanorod copper(II) supramolecular compound adopts a 3-D supramolecular network owing to extensive hydrogen-bonding and π–π stacking. Solvent effects on size and morphology of nanosized 1 have been studied. Calcination of nanosized 1 at 500°C under air yields CuO nanoparticles.     

Magnetic solid-phase extraction of malachite green using soluble eggshell membrane protein doped with magnetic graphene oxide nanocomposite

ABSTRACT

This study describes a new magnetic solid-phase extraction (MSPE) technique based on Fe₃O₄/graphene oxide-soluble eggshell membrane protein (Fe₃O₄/GO-SEP) for accurate measurement of malachite green (MG) residue in various water samples residues by UV-Vis spectroscopy. The morphology of the prepared adsorbent has been studied by scanning electron microscopy and atomic force microscopy in details. Parameters affecting the MSPE were optimised and determined with UV-Vis spectrophotometry thoroughly. Under the optimised extraction circumstances, the introduced method represented a wide linearity over the concentration of 0.5–250 ng mL^?1, a high enrichment factor of 83.3 and low detection limit of 0.2 ng mL^?1. The prepared Fe₃O₄/GO-SEP was successfully used for preconcentration and determination of MG in river and fish farming water samples with suitable precision and accuracy.     

Spontaneous formation of vesicles and chiral self-assemblies of sodium N-(4-dodecyloxybenzoyl)-L-valinate in water

A novel N-acylamino acid surfactant, sodium N-(4-dodecyloxybenzoyl)-L-valinate (SDLV), has been synthesized. The aggregation behavior of the surfactant in aqueous solution has been studied by surface tension, fluorescence probe, microscopy, and dynamic light scattering (DLS) techniques. The amphiphile has a very low critical aggregation concentration (cac). These studies have suggested formation of large bilayer structures in water. The mean apparent hydrodynamic radius, RH, of the self-assemblies in dilute aqueous solution obtained from DLS measurements confirmed formation of large aggregates. The FT-IR spectra of the amphiphile have indicated strong intermolecular amide hydrogen bonding in the self-assemblies in aqueous solution. The microenvironment of the fluorescence probes is highly nonpolar and viscous in nature. The circular dichroism (CD) spectra of SDLV were recorded in water and in a 1:1 water-methanol mixture. The CD spectra have indicated the presence of chiral aggregates in aqueous solution above the cac. The microstructure of the aggregates has been studied by use of optical and transmission electron microscopy. Both types of micrographs have shown the presence of a variety of morphologies including giant spherical vesicles, tubules, twisted ribbons, and helical strands in aqueous solutions.     

Substrate specific nanoreactors based on pyrimidine-containing amphiphiles of various structures for cleavage of phosphonates

ABSTRACT

The series of novel pyrimidine-containing amphiphiles were examined as catalysts for cleavage of phosphonates having various hydrophobicities. Kinetic data showed marked substrate specificity of three different types (i) inhibition for both substrates, (ii) catalysis for more hydrophobic phosphonate and inhibition for less hydrophobic phosphonate, and (iii) catalysis for both substrates. The highest acceleration (more than 11 times in comparison with the reaction in the absence of amphiphile) has been reached in the case of dicationic amphiphile with three hydrophobic tails.     

A Better Understanding of the Formation of Silica Nanococoons

Silica nanococoons with coiled or concentric circular pore channels in the walls attracted much attention, recently. However, the formation of them is not well illustrated. Herein, hollow silica shells with organized pore channels parallel to the shell surface were prepared through a single‐templating method using the self‐assemblies of a chiral low‐molecular‐weight amphiphile,L‐18Phe6PyBr, as templates under a dilute concentration. These nanococoons were characterized using X‐ray diffractometer and N₂ sorption. The formation of them was clearly shown in the field‐emission electron microscopy images which were taken at a low voltage. Moreover, transmission electron microscopy images taken after different reaction times indicated a cooperative self‐assemble mechanism. It was also found that the nanocoons were formed from coiled nanoribbons.     

SURFACE STRUCTURE OF THE MICELLE OK AN AMPHOTERIC AMPHIPHILE DERIVED FROM LYSINE

ABSTRACT

Micelle structure in aqueous colloid of an amphoteric amphiphile N^αN^α-dimethyl-N^? -lauroyl lysine (DMLL), which was derived from lysine, was studied through light scattering, SAXS and a rheological method. The critical micelle concentration of the colloid system is 216 UM and the weight average molecular weight of the micelle is 2.40 × 10⁴, i.e. the aggregation number is 67.4. The diameter of the micelle is about 43.4 Å and the spherical micelle is likely to be retained in a concentration up to about 20 %, The SAXS measurements show that the electron density Fluctuation in the micelle is almost negligible and that the surface area of the micelle is approximately 3.5 times larger than that of a completely smooth sphere.     

Proton-coupled electron transfer from photo-excited CdS nanoparticles

Abstract

Polyoxometalate (POM) cluster anions form monolayers on metal(0) nanoparticles (NPs) in water, serve as protecting ligands for binary-salt nanocrystals (such as AgCl), and as covalently attached ligands on anatase TiO₂ nanocrystals. We now show that the lacunary-Keggin ion [α-AlW₁₁O₃₉]^9? (1) binds strongly to Cd²⁺ in water, providing control over the growth and stability of CdS nanoparticles (NPs) that form upon addition of sulfide. When reduced by a single electron, the already highly negatively charged POM, 1 is protonated by water, and 1-protected CdS NPs were used as visible-light driven electron donors to assess whether combined reduction and protonation of 1 occurred via sequential electron- and proton-transfer steps (an ETPT mechanism), or simultaneously, via concerted proton-electron transfer (CPET). Comparison of the kinetic profiles for reduction of 1 in D₂O and in H₂O showed the absence of a kinetic isotopic effect (KIE), characteristic of ETPT mechanisms.     

A triply-responsive supramolecular amphiphile fabricated by a thermal-responsive pillar[5]arene-based host–guest recognition motif

A novel molecular recognition motif was built between a neutral water soluble pillar[5]arene and decyltrimethylammonium bromide in water. Its thermal-controlled complexation with G1 in water was investigated. Furthermore, based on this new thermal responsive host–guest recognition motif, we further constructed a supramolecular amphiphile between this pillar[5]arene and a trimethylammonium bromide derivative containing an azobenzene group at the other end. This supramolecular amphiphile showed triply-responsiveness, that is, thermal responsiveness of the host–guest complex, photo-responsiveness of the azobenzene group and chemical-responsiveness by adding β-CD.     

Synthesis and structure of tin tetrachloride adducts with crown ether: Crystal structure of [Sn(H2O)2Cl4] · 18C6 and [Sn(H2O)2Cl4] · 18C6 · 2H2O

Tin coordination compounds [Sn(H₂O)₂Cl₄] · 18C6 (I) and [Sn(H₂O)₂Cl₄] · 18C6 · 2H₂O (II) were synthesized and identified by IR spectroscopy, CH analysis, and X-ray powder diffraction. The crystal structures of compounds I and II were determined. The crystals of I and II are orthorhombic; a = 16.871(1) ?, b = 7.7305(7) ?, c = 16.939(1) ?, Z = 4, space group Cmca for I; a = 14.206(2) ?, b = 20.376(3) ?, c = 8.319(1) A, Z = 4, space group Pna21 for II. The structural units of I and II are [Sn(H₂O)₂Cl₄] · 18C6 complex molecules (in II, also water molecules of crystallization). The coordinated water molecules in I are trans and those in II are cis to each other. The structural units in the crystals of I and II are combined only by hydrogen bonds between water molecules and the crown-ether oxygen atoms with the formation of the chain structure. Complex I was tested as the precursor of tin dioxide in a chemical vapor deposition (CVD) process. The morphology of the obtained film was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the composition was studied by laser mass spectrometry for elemental analysis.     

Imidazolium ionic liquids as bifunctional materials (morphology controller and pre-catalyst) for the preparation of xerogel silica’s

This article describes the preparation of xerogel silica’s by the sol–gel technique in the presence of the ionic liquids (ILs) 1-triethylene glycol monomethyl ether-3-methylimidazolium methanesulfonate 1 and 1-monoethylene glycol monomethyl ether-3-methylimidazolium methanesulfonate 2, using tetraethoxysilane as precursor. The addition of water to these ILs resulted in the formation of protonic acid. As a consequence, the ILs functioned as morphology controller and acid pre-catalyst at the same time. Characterization of these materials was performed by photography, scanning electron microscopy, thermogravimetric analysis and powder X-ray diffraction. Compact lamellar monoliths with interlamellar distances of approximately 1.5 nm and flat surfaces were obtained with both ILs. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Agar: a natural and environmentally-friendly support composed of copper oxide nanoparticles for the green synthesis of 1,2,3–triazoles

ABSTRACT

A novel, green and cost-effective heterogeneous nanocatalyst was synthesized by supporting copper (I) oxide nanoparticles on magnetic agar (Cu₂O/Agar@Fe₃O₄). Then, it was characterized with multiple techniques, such as scanning electron microscopy and transmission electron microscopy images, energy-dispersive X-ray analysis, Fourier-transform infrared (FT–IR) spectroscopy, thermogravimetric (TG) analysis, X-ray diffraction pattern, vibrating sample magnetometer curve, and inductively coupled plasma analysis. The catalytic activity of the newly designed catalyst was investigated in a one-pot three-component reaction of alkyl halides, sodium azide, and alkynes to obtain 1,4–disubstituted 1,2,3–triazoles in high yields in water–ethanol media. The present catalyst was simply separated from the reaction media by an external magnet and reused at least five subsequent runs without significant activity loss.     

Preparation of a simple biocompatible magnetite@citric acid: An efficient reusable solid acid catalyst for the rapid synthesis of antipyrine Schiff’s bases and study of their radical scavenging potential

Citric acid immobilized magnetic nanoparticles (MNPs@CA) have been synthesized and used for the preparation of bio-important antipyrine (1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) derived Schiff’s bases (3a–k) in lesser reaction time with very high yield under ultrasonication. The catalyst was characterized by FT-IR, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis (TGA). The functionalized nanoparticles were easily separated using an external magnet during work-up procedure and show excellent reusability upto 8 cycles without any significant loss in catalytic activity. All the synthesized compounds (3a–k) were screened by DPPH (2,2-diphenyl-1-picrylhydrazyl) method with respect to ascorbic acid for their antioxidant activity and some of them gave promising results.