Influence of Doped Ions on Persistent Luminescence Materials:a Review

Persistent luminescence materials(PLMs) are potential luminescent materials which can remain emitting light after stopping the excitation. PLMs can avoid the autofluorescence of biological tissues, and play an important role in biosensing, targeted imaging and other fields. However, the applications of PLMs are often restricted by their weak persistent luminescence and short decay time after excitation. Doped ions will directly affect the luminescence centers and trap levels of PLMs, thereby lea...     

SERS‐ and Electrochemically Active 3D Plasmonic Liquid Marbles for Molecular‐Level Spectroelectrochemical Investigation of Microliter Reactions

Liquid marbles are emergent microreactors owing to their isolated environment and the flexibility of materials used. Plasmonic liquid marbles (PLMs) are demonstrated as the smallest spectroelectrochemical microliter‐scale reactor for concurrent spectro‐ and electrochemical analyses. The three‐dimensional Ag shell of PLMs are exploited as a bifunctional surface‐enhanced Raman scattering (SERS) platform and working electrode for redox process modulation. The combination of SERS and electrochemistry (EC) capabilities enables in situ molecular read‐out of transient electrochemical species, and elucidate the potential‐dependent and multi‐step reaction dynamics. The 3D configuration of our PLM‐based EC‐SERS system exhibits 2‐fold and 10‐fold superior electrochemical and SERS performance than conventional 2D platforms. The rich molecular‐level electrochemical insights and excellent EC‐SERS capabilities offered by our 3D spectroelectrochemical system are pertinent in charge transfer processes.     

Bilayered phospholipid micelles and capillary electrophoresis: a new additive for electrokinetic chromatography

Phospholipid micelles and bilayered micelles (bicelles) were investigated as a new media for electrokinetic chromatography. The benefit to using these additives for micellar electrokinetic chromatography (MEKC) is the potential of a simple bilayer membrane model operated with fast analysis time, and low sample injection volumes. The system is used to separate peptides/protein and is tested with a series of beta-blockers. The results suggest that bicelle electrokinetic chromatography provides selectivity and holds potential as an alternative approach to modeling membrane phenomenon.     

Solvation of ions in hydrophilic layer of polyoxyethylated nonionic micelle. Cooperative approach by electrophoresis and ion-transfer voltammetry

Electrophoretic measurements of micellar mobility have revealed that polyoxyethylated nonionic surfactant micelles have negative zeta potential in various electrolytes, indicating that the partition of anions into the micelle dominates the entire electrolyte partition and the induced surface potential of the micelle. Although an excess of a negative charge is thus revealed in the micelle, it is uncertain whether anions are preferably solvated in the micelles or cations are expelled from the micelles. To determine the solvation energies of single ions in the hydrophilic layer of the micelle, we have performed ion transfer voltammetric measurements at microinterfaces between nitrobenzene and aqueous tetraethyleneglycol solution, which acts as a model for the palisade layer of the micelles. The cooperative utilization of these different methods has allowed us to determine the Gibbs free energy of transfer of a single ion without an extrathermodynamic assumption. On the basis of the resulting values, the partition of ions and the zeta potential induced by the imbalance of anionic and cationic partition have been quantitatively explained.     

Structure and interactions in micellar solutions: molecular simulations of pluronic L64 aqueous solutions

Coarse-grained, implicit solvent molecular simulations have been conducted to investigate the structure and interactions of L64 Pluronic micelles in aqueous solutions. Simulations of an L64 solution beginning with monodisperse micelles (aggregation number Nagg = 40 chains) resulted in a narrow Gaussian distribution of Nagg centered around 40. While not fully equilibrated, this distribution supports the supposition that L64 micelles with Nagg = 40 are representative of the conditions considered and model employed. Detailed analysis of intramicellar monomers distribution and micelle shapes revealed that L64 micelles have a scalene ellipsoidal shape. Additional simulations of solutions containing 125 micelles constrained to have Nagg = 40 at polymer volume fractions of 0.024 and 0.110 were performed to study micelle-micelle structure factor, single micelle form factor, and total scattering intensity. The ability of various models utilized in analysis of scattering profiles in micellar solutions to describe the structure of the model L64 solutions was investigated. Investigation of the potential of mean force between two micelles reveals that the interactions between micelles are repulsive but on a length scale smaller than the mean micelle diameter, indicating that the micellar shape fluctuations are important in determining intermicellar interactions.     

Polyelectrolyte micelles in salt‐free solutions: Micelle size and electrostatic potential

The structural and electrical characteristics of polyelectrolyte micelles formed by diblock copolymers with one charged block and one solvophobic block are studied by the means of molecular dynamics simulations using the Primitive model at different Bjerrum lengths. The properties of interest are the mean aggregation number, the shape, the electrical potential as a function of the distance of the micelle's center of mass and the zeta potential. We found that for partially charged short A blocks the micelles’ mass distribution function is at least bimodal, indicating the coexistence of small and large micelles in agreement with theoretical and experimental findings. The zeta potential is not a monotonic function of the length of the charged block. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 924–934     

反胶束系统及萃取蛋白质的分子热力学模型1: 反胶束系统的分 子热力学模型

以反胶束系统稳定性的热力学分析为基础,综合分析了反胶束系统的三大效应,即低界面张力效应、界面弯矩效应、混合熵效应,提出了一个分子热力学模型,模型所预言的反胶束水分含量随无机盐种类、浓度、表面活性剂浓度以及助表面活性剂含量的变化与所获实验规律定量相符,还能预言反胶束内表面处电势值、表面活性剂解离度。     

Thermo and pH Dual-Responsive Micelles of N-phthaloylchitosan-g-Poly(N-isopropylacrylamide) and Poly(acrylic acid-co-tert-butyl acrylate) for Drug Delivery

A novel amphiphilic copolymer N-phthaloylchitosan graft poly(N-isopropylacrylamide) and poly(acrylic acid-co-tert-butyl acrylate) (PHCS-g-PNIPAAm&P(AA-co-tBA)) was synthesized. The graft copolymer could form micelles in aqueous medium, and the critical micelle concentration (CMC) of the copolymer was 7.5 × 10^{? 3}mg/mL. The lower critical solution temperature (LCST) of the micelles was measured to be 30°C. Transmission electron microscopy (TEM) image showed that the micelles exhibited a regular spherical shape, and the mean diameter of the micelles was 94.1 ± 0.8 nm as determined by dynamic light scattering (DLS). The potential usefulness of the micelles as drug delivery systems was investigated using anti-inflammation drug prednisone acetate as the model. The drug loading capacity of the micelles was measured to be 22.86 wt%, and the DLS results showed that the mean diameter of the drug-loaded micelles was 133.3 ± 2.4 nm. In vitro drug release studies indicated that the micelles exhibited thermo and pH dual-responsive release profiles.     

Nonideal mixed micelles of Gemini surfactant homologues and their application as templates for mesoporous material MCM-48

The micellization properties of aqueous solutions of the mixed Gemini surfactant homologues GEM16-6-16 and GEM16-12-16 with various compositions were investigated. The measured critical micelle concentration (CMC) deviated significantly from the ideal mixing model. Good agreement was found with a nonideal mixing model, the Margules model, which has two optimal parameters, A12=-3.611 and A21=-6.318. It was shown that the properties of mixed micelles were not sensitive to the compositions, and most of the GEM16-12-16 molecules were aggregated into the micelles. Dynamic laser light-scattering measurements revealed that the mixed micelles had almost the same size and similar zeta potential. When the mixed micelles were used as templates, a series of highly ordered cubic MCM-48 mesoporous materials, characterized by XRD and TEM, were produced through self-assembly. The N2 adsorption-desorption measurements suggested that the pores of these materials had similar average diameters of 2.2-2.5 nm. This further demonstrated the nonideal behavior of the homologue mixture.     

Stability of model membranes in the presence of organotin compounds

The influence of tri‐ and di‐alkyltins (TATs and DATs) as well as di‐ and triphenyltin compounds (DPhTs and TPhTs) on haemolysis of red blood cells (RBCs) and stability of planar lipid membranes (PLMs) has been studied. The results obtained show that the efficiency of TATs (trimethyl‐, triethyl‐, tri‐n‐propyl‐ and tributyl‐tin chlorides) in destroying PLMs did not differ greatly when the compounds were studied in solutions of physiological pH (phosphate buffer, pH 7.4). A decrease in pH to 5.0 caused small changes in the efficiency of the three largest TAT molecules and a significant decrease in the efficiency of trimethyltin chloride. Both haemolytic and PLM experiments showed that the most active TAT was tri‐n‐propyltin chloride. The destructive action of DAT (dimethyl‐ and dibutyltin) and DPhT dichlorides was somewhat more differentiated. Dimethyltin dichloride (DMT) interaction with model membranes was a little weaker than that of DPhT and dibutyltin dichlorides and all these compounds influenced the model membranes to a lesser extent than TATs or TPhT. To bring about comparable haemolysis effects the dichlorides had to be used at much greater concentrations than the chlorides. The haemolytic properties of the dichlorides, especially of that of DMT, significantly increased in solution at pH 5.0. TPhT chloride interacted with model membranes similarly to TAT chlorides. Also, no great difference in efficiency of this compound was found for the two buffer solutions used. Copyright © 2000 John Wiley & Sons, Ltd.     

Preparation and characteristics of linoleic acid-grafted chitosan oligosaccharide micelles as a carrier for doxorubicin

The linoleic acid (LA)-grafted chitosan oligosaccharide (CSO) (CSO-LA) was synthesized in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), and the effects of molecular weight of CSO and the charged amount of LA on the physicochemical properties of CSO-LA were investigated, such as CMC, graft ratio, size, zeta potential. The results showed that these chitosan derivatives were able to self-assemble and form spherical shape polymeric micelles with the size range of 150.7–213.9 nm and the zeta potential range of 57.9–79.9 mV, depending on molecular weight of CSO and the charged amount of LA. Using doxorubicin (DOX) as a model drug, the DOX-loaded CSO-LA micelles were prepared by dialysis method. The drug encapsulation efficiencies (EE) of DOX-loaded CSO-LA micelles were as high as about 75%. The sizes of DOX-loaded CSO-LA micelles with 20% charged DOX (relating the mass of CSO-LA) were near 200 nm, and the drug loading (DL) capacity could reach up to 15%. The in vitro release studies indicated that the drug release from the DOX-loaded CSO-LA micelles was reduced with increasing the graft ratio of CSO-LA, due to the enhanced hydrophobic interaction between hydrophobic drug and hydrophobic segments of CSO-LA. Moreover, the drug release rate from CSO-LA micelles was faster with the drug loading. These data suggested the possible utilization of the amphiphilic micellar chitosan derivatives as carriers for hydrophobic drugs for improving their delivery and release properties.     

The gibbs energy,chemical potential,and state parameters of the surface of an ionic micelle in the form of an ellipsoid of revolution

A molecular-thermodynamic model of an ionic micelle in the form of an ellipsoid of revolution was suggested. Equations for the chemical potential of an ellipsoidal micelle, the work of transfer of ions from solution volume into the micelle, and the state parameters of the surface of the micelle (fraction of free hydrophobic surface, surface tension coefficient, and surface charge density) were obtained. The Gibbs energy, chemical potential, work of transfer, and state parameters of an ellipsoidal micelle were determined as depending on the form factor of the corresponding ellipsoid. The model was verified for the example of sodium decyl sulfate micelles. The calculated parameters were close to the thermochemical data on the asymmetrization of spherical micelles in a solution of sodium decyl sulfate. The equilibrium ion-micellar solution composition was estimated.     

Micelle or polymersome formation by PCL-PEG-PCL copolymers as drug delivery systems

Polymeric micelles and polymersomes may have great potential as the drug delivery vehicles for solubilization of hydrophobic drugs.     

SERS- and Electrochemically Active 3D Plasmonic Liquid Marbles for Molecular-Level Spectroelectrochemical Investigation of Microliter Reactions

Liquid marbles are emergent microreactors owing to their isolated environment and the flexibility of materials used. Plasmonic liquid marbles (PLMs) are demonstrated as the smallest spectroelectrochemical microliter-scale reactor for concurrent spectro- and electrochemical analyses. The three-dimensional Ag shell of PLMs are exploited as a bifunctional surface-enhanced Raman scattering (SERS) platform and working electrode for redox process modulation. The combination of SERS and electrochemistry (EC) capabilities enables in situ molecular read-out of transient electrochemical species, and elucidate the potential-dependent and multi-step reaction dynamics. The 3D configuration of our PLM-based EC-SERS system exhibits 2-fold and 10-fold superior electrochemical and SERS performance than conventional 2D platforms. The rich molecular-level electrochemical insights and excellent EC-SERS capabilities offered by our 3D spectroelectrochemical system are pertinent in charge transfer processes.     

Permeation liquid membrane for trace metal speciation in natural waters. Transport of liposoluble Cu(II) complexes

In this paper, the transport of Cu(II) in the presence of lipophilic Cu(II) organic complexes through permeation liquid membranes (PLMs) have been investigated. In natural waters, small organic compounds, which form liposoluble neutral complexes with Cu(II), are potentially toxic and bioavailable. Hence, to understand the role of liposoluble Cu(II) complexes in natural waters, four organic ligands: phthalic acid, bipyridyl, pyrocatechol and hydroxyquinoline, which form uncharged or lipophilic Cu(II) complexes, were tested. The results showed that the transport of lipophilic Cu(II) complexes through PLM depends on the lipophilicity of the complex. Applications of PLMs in natural waters are presented.     

Some Thoughts Regarding Theoretical Aspects of the Corrin-Harkins Relation and the Micellization Product of Ionic Micelles

The dependence of the stability of ionic micelles on the ionic strength of the medium is examined analytically without recourse to any explicit expression of the surface potential of micelles. The present study is based on the idea developed by Evans, Mitchell, and Ninham (D. F. Evans, D. J. Mitchell, and B. W. Ninham, J. Phys. Chem. 88, 6344 (1984)) that the interfacial free energy at the water/hydrocarbon core interface is independent of the ionic strength of the medium. The Corrin-Harkins (C-H) relation, a linear relation between the logarithm of the critical micelle concentration (cmc) and the logarithm of the counterion concentration n(C), is obtained in the range of n(C) where the salting-out effect is negligible, under the condition that the area per monomer on the micelle surface decreases very weakly with n(C). The "micellization product" of the charged pseudophase model of ionic micelles is discussed. The linear dependence of the surface potential of ionic micelles on n(C) is derived while a part of the effects of salt on the micelle size/shape is allowed. Copyright 2001 Academic Press.     

Viscoelastic micellar water/CTAB/NaNO(3) solutions: rheology, SANS and cryo-TEM analysis

Aqueous micellar solutions of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and sodium nitrate (NaNO(3)) were examined using steady and dynamic rheology, small-angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM). Upon addition of NaNO(3), the CTAB spherical micelles transform into long, flexible wormlike micelles, conveying viscoelastic properties to the solutions. The zero-shear viscosity (eta(0)) versus NaNO(3) concentration curve exhibits a well-defined maximum. Likewise, upon increase in temperature, the viscosity decreases. Dynamic rheological data of the entangled micellar solutions can be well described by the Maxwell model. Changes in the structural parameters of the micelles with addition of NaNO(3) were inferred from SANS measurements. The intensity of scattered neutrons at the low q region was found to increase with increasing NaNO(3) concentration. This suggests an increase in size of the micelles and/or decrease of intermicellar interactions with increasing salt concentration. Analysis of the SANS data using prolate ellipsoidal structure and Yukawa form of interaction potential between micelles indicates that addition of NaNO(3) leads to a decrease in the surface charge of the ellipsoidal micelles and consequently an increase in their length. The structural transition from spherical to entangled threadlike micelles, induced by the addition of NaNO(3) to CTAB micelles is further confirmed by cryo-TEM.     

Structural characterization of micelles formed of cholesteryl-functionalized cyclodextrins

Amphiphilic cholesteryl 2,6-di-O-methyl-β-cyclodextrins (chol-DIMEB) can self-aggregate into spherical micelles of noteworthy potential for drug delivery. All-atom molecular dynamics simulations of chol-DIMEB micelles consisting of 3-24 monomers have been performed in aqueous solution. chol-DIMEB exhibits a pronounced tendency to self-assemble into core-shell structures. van der Waals interactions within the cholesteryl nucleus constitute the main driving force responsible for the formation of the micelle. The calculated radii of the hydrophobic core and of the hydrophilic shell for the micellar structure formed by 24 monomers agree well with the experiment. The cyclodextrin moieties are found to be exposed toward the aqueous medium and possess the appropriate flexibility to capture drugs in an effective fashion. Analysis of the solvent accessible surface area and hydration number indicates that the micelles are highly hydrosoluble species and can, therefore, enhance significantly the aqueous solubility of lipophilic drugs. In addition, the spatial structure of the micelles is suggestive of multiple potential drug binding sites. The present contribution unveils how micelles endowed with specific characteristics can form, while opening exciting perspectives for the design of novel micellar nanoparticles envisioned to be drug carriers of high potential.