Aqueous Dispersion Medium Research Articles

Dual-Pore Carbon Shells for Efficient Removal of Humic Acid from Water.

A template-mediated process for the preparation of mesoporous carbon shells with high surface area, dual-pore structure, and excellent performance in the adsorption of humic acid is reported. Their synthesis involves templating phenolic resin against wrinkled silica nanospheres, subsequent carbonization under Ar atmosphere, and final release of dual-pore mesoporous carbon shells by etching the silica templates. An additional silica layer was used to protect the phenolic resin from aggregation during carbonization, and its subsequent removal gives the carbon shells a hydrophilic surface, which significantly improves their dispersity in aqueous media. When used as adsorbents for humic acid removal, the as-prepared dual-pore mesoporous carbon shells show superior adsorption performance to activated carbon.

Arborescent Unimolecular Micelles: Poly(γ-Benzyl l-Glutamate) Core Grafted with a Hydrophilic Shell by Copper(I)-Catalyzed Azide–Alkyne Cycloaddition Coupling

Amphiphilic copolymers were obtained by grafting azide-terminated polyglycidol, poly(ethylene oxide), or poly(2-hydroxyethyl acrylate) chain segments onto alkyne-functionalized arborescent poly(γ-benzyl l-glutamate) (PBG) cores of generations G1–G3 via copper(I)-catalyzed azide–alkyne Huisgen cycloaddition (CuAAC) coupling. The alkyne functional groups on the arborescent PBG substrates were either distributed randomly or located exclusively at the end of the chains added in the last grafting cycle of the core synthesis. The location of these coupling sites influenced the ability of the arborescent copolymers to form unimolecular micelles in aqueous environments: The chain end grafting approach provided enhanced dispersibility in aqueous media and favored the formation of unimolecular micelles in comparison to random grafting. This is attributed to a better defined core-shell morphology for the copolymers with end-grafted shell segments. Aqueous solubility also depended on the type of material used for the shell chains. Coupling by CuAAC opens up possibilities for grafting a broad range of polymers on the arborescent substrates under mild conditions.

Metal-Organic Frameworks@Polymer Composites Containing Cyanines for Near-Infrared Fluorescence Imaging and Photothermal Tumor Therapy.

As a noninvasive treatment method, photothermal therapy (PTT) has been widely investigated for cancer therapy. In this work, metal-organic frameworks@polymer composites (UiO-66@CyP) with bioimaging and PTT activity were prepared by introducing cyanine-containing polymer (CyP) via multicomponent Passerini reaction in the presence of Zr-based nanoscale metal-organic frameworks (UiO-66). As-prepared UiO-66@CyP not only possesses uniformed size, controllable morphology, and excellent dispersibility in aqueous media, but also indicates strong near-infrared absorption and high photothermal conversion efficiency. Due to these combined merits, UiO-66@CyP appears to be an excellent phototherapy agent for ablation of tumor cells under a low-power laser irradiation and near-infrared fluorescence imaging agent. This work might open up a new avenue to develop multifunctional composites by integrating metal-organic frameworks with carboxyl, aldehyde, and isocyano-containing materials.

Investigation of the Adsorption of Amphipathic macroRAFT Agents onto Montmorillonite Clay.

Recently, there has been significant interest in the use of the reversible addition-fragmentation chain-transfer (RAFT) technique to generate a variety of organic/inorganic colloidal composite particles in aqueous dispersed media using the so-called macroRAFT-assisted encapsulating emulsion polymerization (REEP) strategy. In this process, special attention should be paid to the adsorption of the macromolecular RAFT (macroRAFT) agent onto the inorganic particles, as it determines the final particle morphology and can also influence latex stability. In this work, different amphipathic macroRAFT agents were synthesized by RAFT, and their adsorption onto commercial Montmorillonite clay Cloisite Na+ (MMT) was studied by means of adsorption isotherms. Three types of macroRAFT agents were considered: a nonionic one based on poly(ethylene glycol) methyl ether acrylate (PEGA) and n-butyl acrylate (BA), anionic ones, including a block copolymer and random copolymers, based on acrylic acid (AA), BA and PEGA, and cationic ones based on 2-(dimethylamino)ethyl methacrylate (DMAEMA), BA and PEGA. Six adsorption isotherm models (Langmuir, Freundlich, Tempkin, Redlich-Peterson, Sips, and Brunauer-Emmett-Teller) were adjusted to the experimental isotherms. The nonionic macroRAFT agent formed a monolayer on the clay surface with a maximum adsorption capacity of 400 mg g-1 at pH 8, as determined from the Sips adsorption model. Adsorption of the AA-based macroRAFT agents onto MMT was moderate at alkaline pH due to electrostatic repulsions, but increased with decreasing pH. The DMAEMA-based macroRAFT agents displayed a much stronger interaction with the oppositely charged MMT surface at acidic pH due to electrostatic interactions, and the concentration of adsorbed macroRAFT agent reached values as high as 800 mg g-1. The BET model fitted the experimental data relatively well indicating multilayer adsorption promoted by the presence of the hydrophobic BA units. In addition, the cationic macroRAFT agents afforded stable MMT/macroRAFT agent complexes as evaluated by dynamic light scattering and zeta potential analyses.

Selective biosensing of Staphylococcus aureus using chitosan quantum dots

Selective biosensing of Staphylococcus aureus (S. aureus) using chitosan modified quantum dots (CTS@CdS QDs) in the presence of hydrogen peroxide is reported. The method is based on the intrinsic positive catalase activity of S. aureus. CTS@CdS quantum dots provide high dispersion in aqueous media with high fluorescence emission. Staphylococcus aureus causes a selective quenching of the fluorescence emission of CTS@CdS QDs in the presence of H2O2 compared to other pathogens such as Escherichia coli and Pseudomonas aeruginosa. The intrinsic enzymatic character of S. aureus (catalase positive) offers selective and fast biosensing. The present method is highly selective for positive catalase species and requires no expensive reagents such as antibodies, aptamers or microbeads. It could be extended for other species that are positive catalase.

In Situ Formation of Autodispersing Cellulose Nanoparticles with Extreme Uniformity.

Autodispersing cellulose nanospheres with a uniform diameter of 20 nm were prepared via self-assembly of cellulose chains with controlled molar masses in an ionic liquid. To obtain nanospheres, cellulose was dissolved in 1-butyl-3-methylimidazolium chloride and then precipitated in deionized water. During dissolution, positive charges were induced at the reducing ends of cellulose by the reaction with the imidazolium. The reaction was more active when the molar mass was smaller than 100 kg·mol-1. As the molar mass decreased, the surface charge originating from the imidazolium increased, resulting in a stable dispersion in aqueous media. The increase of the surface charge also improved the crystallinity and the uniformity of the size dramatically.

A theoretical study on the stability of CNT encased cyclic peptide beyond hydrogen bond cut-off

The Carbon nanotubes (CNT) are potential candidate for many biomedical applications especially in targeted drug delivery for cancer diseases. However, the use of CNT has limitations due to its insolubility in aqueous media. The self-assembly of cyclic peptide encased on the CNT has enhanced its dispersion in aqueous medium which extend their applications as antibacterial and drug delivery agents. To understand this process, an attempt has been made to investigate the dynamics and stability of trimer cyclic peptide encasing with CNT using classical molecular dynamics. The model cyclic peptide monomer constitutes 14 series of amino acids viz.; (cyclo-[(D-ARG-L-VAL-D-ARG-L-THR-D-AGR-L-LYS-D-GLY-L-ARG-D-ARG-L-ILE-D-ARG-L-ILE-D-PRO-L-PRO)]). Each cyclic peptide in the assembly stacking far apart at approximately 15 Å each other beyond hydrogen bond cut-off distance. The trimer was observed to be stable only over 10 ns of entire MD trajectory. But when there is electrostatic interaction between cyclic peptides at 6.5 Å distance then assembly is stable for entire 50 ns. Our result reveals that for a stable assembly, beyond the hydrogen bond cut-off distance, the electrostatic interaction plays significant role.

PdZn intermetallic on a CN@ZnO hybrid as an efficient catalyst for the semihydrogenation of alkynols

This work highlights a novel hybrid catalyst, intermetallic PdZn on CN@ZnO (PdZn/CN@ZnO), which serves as a highly efficient heterogeneous catalyst for semihydrogenation of 2-methyl-3-butyn-2-ol utilizing water as the solvent. Compared with intermetallic PdZn on ZnO (PdZn/ZnO), PdZn/CN@ZnO displays almost sixfold higher TOF while retaining high selectivity. It is assumed that the introduction of biomass-derived hydrophilic nitrogen-doped carbon into the ZnO helped to promote catalyst dispersion in aqueous media, ensuring better mass transfer. Further experiments and theoretical calculations showed that from Pd particles to intermetallic PdZn, the decrease of corner and edge Pd atoms might be a factor leading to the improvement of selectivity. Recycling experiments demonstrated that the PdZn/CN@ZnO catalyst could be reused at least eight times without significant decrease in activity or selectivity. Furthermore, when applied to industrially relevant alkenols that are building molecules for the production of vitamin E, the present catalyst still offered excellent performance. It is expected that the present catalytic system will demonstrate its high potential for practical production of vitamin E.

Photocatalyst performance in wastewater treatment applications: Towards the role of TiO2 properties

The photocatalytic activity of twelve TiO2 samples prepared by different sol-gel methods have been evaluated in order to comprehensively understand the role of the different TiO2 physico-chemical properties on the catalyst performance. These catalysts have been extensively characterized (analyzed by TEM, XRD, UV–vis, N2-isotherms, NH3-isotherms, DRIFTs and Laser Diffraction techniques) and tested to analyze the effect of each property by comparing, for example, samples with different rutile contents but with similar anatase crystal sizes and surface areas.The results of this work suggest that best efficiencies can be obtained with samples constituted by only anatase phase and characterized by a relatively high crystal size and a high degree of crystallinity. On the other hand, the results have shown that even though significantly high surfaces areas do not seem to be a prerequisite to achieve the best efficiencies when phenolic pollutants (poorly adsorbed substrates) are evaluated, a certain grade of textural properties must be maintained to keep the surface quality, and a high degree of TiO2 sample dispersion in aqueous media is also desirable to optimize the photocatalytic activity. The results of this work may provide valuable information to design and produce new highly efficient TiO2 photocatalysts materials for wastewater treatment applications.

Metal–Organic Framework@Porous Organic Polymer Nanocomposite for Photodynamic Therapy

The limitation for the biomedical application of porous organic polymers (POPs) is the big size and poor dispersibility in aqueous media. Herein, a nanoscale metal–organic framework (MOF)@POP composite, named UNM, has been synthesized by epitaxial growth of the photoactive porphyrin-POPs (H2P-POP) on the outer surface of amine containing UiO-66 (UiO-AM). After the growth of POPs, the crystallization, pore structure, and size distribution of UNM are retained well. The formed UNM possesses a small size of less than 200 nm and could be internalized by cancer cells. Such light-activated UNM exhibits efficient ability to generate 1O2 under various experimental conditions, which can be further applied for PDT efficacy. The present work demonstrates the great potential of nanoscale porous polymers in biomedical fields and cancer treatment.

Effect of PEG functionalized carbon nanotubes on the enhancement of thermal and physical properties of nanofluids

In this study, pristine carbon nanotubes and polyethylene glycol functionalized carbon nanotubes (CNT-PEG) have been used to enhance the heat capacity, viscosity, thermal conductivity, heat transfer rate and pressure drop of nanofluids. Multi-walled carbon nanotubes (MWCNT) were functionalized with polyethylene glycol (PEG) using a Fischer esterification method to improve their dispersion in aqueous media. Three concentrations of 0.01wt%, 0.05wt% and 0.1wt% of pristine and functionalized CNTs in the nanofluids have been used. The heat-transfer rate and pressure drop of these nanofluids have been measured in a shell and tube heat exchanger. Differential Scanning Calorimetry (DSC) was used to study the specific heat capacity of the nanofluids. The specific heat capacity of pristine and functionalized CNTs mixed with water was found to be significantly higher than of the pure water by 10% and 45% respectively. The results of the heat transfer of the nanofluids increased suddenly with the increasing the concentrations of both pristine and functionalized CNTs. It can be concluded that the functionalizing CNT with Polyethylene glycol enhanced the dispersion of the CNTs and increased their heat capacities. The viscosity of the nanofluids was found to be dependent on the concentration of CNTs in solution. The pressure drop of the nanofluid compared with that of pure water was almost unchanged resulting in no extra pumping energy penalty.

Elucidating the influence of materials-binding peptide sequence on Au surface interactions and colloidal stability of Au nanoparticles.

Peptide-mediated synthesis and assembly of nanostructures opens new routes to functional inorganic/organic hybrid materials. However, understanding of the many factors that influence the interaction of biomolecules, specifically peptides, with metal surfaces remains limited. Understanding of the relationship between peptide sequence and resulting binding affinity and configurations would allow predictive design of peptides to achieve desired peptide/metal interface characteristics. Here, we measured the kinetics and thermodynamics of binding on a Au surface for a series of peptide sequences designed to probe specific sequence and context effects. For example, context effects were explored by making the same mutation at different positions in the peptide and by rearranging the peptide sequence without changing the amino acid content. The degree of peptide-surface contact, predicted from advanced molecular simulations of the surface-adsorbed structures, was consistent with the measured binding constants. In simulations, the ensemble of peptide backbone conformations showed little change with point mutations of the anchor residues that dominate interaction with the surface. Peptide-capped Au nanoparticles were produced using each sequence. Comparison of simulations with nanoparticle synthesis results revealed a correlation between the colloidal stability of the Au nanoparticles and the degree of structural disorder in the surface-adsorbed peptide structures for this family of sequences. These findings suggest new directions in the optimization and design of biomolecules for in situ peptide-based nanoparticle growth, binding, and dispersion in aqueous media.

Contemporary Strategies in Emulsified Drug Delivery Systems : A Retrospective Overview = الإستراتيجيات المعاصرة في المستحلب المخدرات أنظمة التسليم : لمحة استعادية

Oral bioavailability of drugs can be augmented by self-emulsifying systems. Different self-emulsifying systems such as self-emulsifying drug delivery systems (SEDDS), self-microemulsifying drug delivery systems (SMEDDS), and self-nanoemulsifying drug delivery systems (SNEDDS) offerstrategic drug delivery systems to improve the solubility, permeability and bioavailability of both hydrophilic andhydrophobic drug moieties. The success of commercial formulations such as Sandimmune Neoral brand of cyclosporine A and Fortovase of Saquinavir escalated interest in lipid based formulations. Self-micro-emulsifying drug delivery systems (SMEDDS) are isotropic mixtures of lipids (oils), surfactant and co-surfactant with unique property of producing oil-in-water (o/w) microemulsion upon gentle agitation. Current research is focused on self-double emulsifying drug delivery systems (SDEDDS) for effective administration of hydrophilic active moieties, proteins and peptide drugs. The SDEDDS comprises double emulsions of larger oil droplets incorporating an aqueous internal phase existing in a dispersed phase in an aqueous dispersion medium. The solid forms of lipid based drug delivery systems have been developed to overcome their stability problems. This article provides an overview on novel emulsions, physico-chemical factors of SMEDDS, excipients used for self emulsification, aspects on formulation and the mechanism of drug transport through SDEDDS. This review specially emphasizes on the techniques which are employed in converting the liquid/semi solid self-microemulsifying systems into solid-self microemulsifying formulations. Encapsulation process, spray drying, adsorption onto inert vehicles, melt granulation and melt extrusion techniques were evidenced retrospectively in this article. Solid SEDDS are suitable for lipophilic drugs while solid SDEDDS are most suited for hydrophilic moieties.

Highly dispersed AuPd alloy nanoparticles immobilized on UiO-66-NH2 metal-organic framework for the detection of nitrite

In this work, highly dispersed AuPd alloy nanoparticles (NPs, 3–6nm) decorated amino-functionalized Zr(IV)-based metal–organic framework (i.e. UiO-66-NH2) was prepared via a novel adsorption/reduction method in ethanol-water solution. In this process, the UiO-66-NH2 acted as both supporting platform and protective agent. The pores of UiO-66-NH2 could limit the aggregation and migration of AuPd alloy NPs. The resulting AuPd/UiO-66-NH2 catalyst possessed large specific surface area and excellent stability and dispersity in aqueous media. When it was used to construct a nitrite sensor, the composite material exhibited higher catalytic activity than the metal counterparts (i.e., Au/UiO-66-NH2 and Pd/UiO-66-NH2) due to the strong metallic synergistic effect. The electrochemical study demonstrated that the AuPd/UiO-66-NH2 based sensor had an extended linear response concentration range of 0.05–5666μM for nitrite detection, with a detection limit of 0.01μM. It was successfully applied to determine nitrite in sausage and pickle samples.

Study of Products of Metallic Titanium Electrospark Dispersion in Aqueous Medium

The results of electrospark dispersion of the metallic titanium loading in aqueous medium are presented in the paper. Raster electronic microscopy, X-ray phase analysis and BET method were used to investigate properties of the obtained powder. Values of specific surface are given in the paper, and morphology and structure of the obtained powders are studied. It is established that chemical and phase composition of the obtained powders is identified by properties of the molten titanium to interact with the dissolved in dispersion medium gaseous products.

HYDROGEN BONDS AND INTERACTIONS IN DRILLING FLUIDS

The article analyzes the intermolecular interactions in drilling fluids according to the conceptions of the supramolecular chemistry. Using the calculation method the values and the validity of orientation, induction and dispersion interactions in the formation of hydrogen bonds were obtained. It is shown that the interactions between the «nanoclay », multicharge, multifield and molecules of water lead to the formation of stable hydrogen bonds in the aqueous dispersion medium of the drilling fluid.

Nanocomposites based on Soluplus and Angelica gigas Nakai extract fabricated by an electrohydrodynamic method for oral administration

Nanocomposites (NCs) based on Soluplus (SP) were fabricated by an electrohydrodynamic (EHD) method for the oral delivery of Angelica gigas Nakai (AGN). Nano-sized particles were obtained after dispersing the resultant, produced by the EHD technique, in the aqueous environment. AGN/SP2 (AGN:SP=1:2, w/w) NC dispersion in aqueous media exhibited a 130nm mean diameter, narrow size distribution, and robust stability in the tested concentration range of the ethanol extract of AGN (AGN EtOH ext) and at pH 1.2 and 6.8. Amorphization of the components of AGN and their interactions with SP in the AGN/SP2 NC formulation were demonstrated by X-ray diffractometry (XRD) analysis. The released amounts of decursin (D) and decursinol angelate (DA), major components of AGN, from NCs were improved compared with those from the AGN EtOH ext group at both pH 1.2 and 6.8. As D and DA can be metabolized into decursinol (DOH) in the liver after oral administration, the DOH concentrations in plasma were quantitatively determined to evaluate the oral absorption of AGN. In a pharmacokinetic study in rats, higher oral absorption and the maximum concentration in plasma (Cmax) were presented in the AGN/SP2 NC group compared with the AGN EtOH ext and AGN NC groups. These findings indicate the successful application of developed SP-based NCs for the oral delivery of AGN.

Nanoassemblies constructed from bimodal mesoporous silica nanoparticles and surface-coated multilayer pH-responsive polymer for controlled delivery of ibuprofen.

The pH-sensitive poly(D-A) grafted amine-functionalized bimodal mesoporous silica (D-A/BMMs) was prepared by a facile method used as a drug delivery vehicle. They exhibited superior properties such as good dispersion in aqueous medium, high drug loading efficiency, improved stability and high drug release rates. Meanwhile, its structural features and performances in a controlled delivery of ibuprofen (IBU) were systematically investigated by using XRD, N2 adsorption and desorption, SEM, TEM, FT-IR, elemental analysis and TG techniques. The results demonstrated that the obtained nanocomposite presented a flexible control over drug release by controlling the grafting amount of D-A onto the mesopores surface of aminated BMMs. The cumulative percent release of IBU from D-A/BMMs was found to be much higher at pH 7.4 than at pH 2.0. The release rate was very slow in an acidic medium but became faster in a neutral medium, owing to hydrogen bonding in an acidic medium and electrostatic repulsion between negatively charged carboxyl groups in an alkaline medium.

Covalent Grafting of Tethered Homopolymer Film on p-Si(100).

Covalent grafting of a homopolymer film onto a p-Si(100) surface was performed by use of surface electroinitiated emulsion polymerization. This polymerization method was one-step and cost-effective, and worked in the aqueous dispersed media containing both nitrobenzenediazonium (NBD) tetrafluoroborate and methyl methacrylate (MMA) monomer. NBD was reduced in the vicinity of substrate at the cut-on voltage of the pulsed voltage and was successively grafted on a Si surface, leading to a polynitrophenyl (PNP) layer. The reduction of NBD simultaneously initiated the polymerization of MMA. The resulting PMMA macroradicals in the solution can react with the previously grafted PNP at the cutoff voltage of the pulsed voltage for thickening the polymer film. The prepared polymer layer completely covered the Si surface, as investigated by the scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Importantly, chemical components and the thickness of the grafted polymer film were well controlled by the applied voltage and the charge flow passing through the Si electrode. X-ray photoelectron spectroscopy (XPS) measurement further confirmed the Si-C bond between the polymer layer and the Si substrate. The homopolymer film was extremely effective in protecting the underlying Si from atmospheric oxidation.

Surface-imprinted polymer coating l-cysteine-capped ZnS quantum dots for target protein specific recognition

This paper demonstrated a new method for preparing fluorescent molecularly imprinted polymer (MIP) for specific recognition of a target protein. The MIP-based fluorescent receptor was developed by coating MIP layer on the surface of l-cysteine modified Mn2+-doped ZnS quantum dots (QDs) using the surface molecular imprinting process. These MIP-QDs composites demonstrated fast adsorption kinetics, high stability, and good dispersibility in aqueous media. Since the fluorescence quenching of MIP-QDs composites is proportional to the concentration of the lysozyme, the MIP-based fluorescent receptor was successfully applied to the direct fluorescence quantification of lysozyme without further pretreatment. The MIP-based fluorescent receptor exhibited good selectivity and sensitivity for lysozyme detection. The optimum fluorescence intensity of the MIP-QDs was found to be at pH 6.0, and the linear range of lysozyme was from 0.1 to 2.0 μM with the detection limit of 25.2 nM. Moreover, the proposed fluorescent receptor was satisfactorily applied to the determination of lysozyme in real samples. This study provides a new approach for recognizing and detecting of specific proteins in biological samples.