Bulk Aqueous Phase Research Articles

Use of silver\u2013bentonite in sorption of chloride and iodide ions

Ag–bentonite was prepared by ion exchange process to sorb iodide and chloride ions in batch experiments. The modified bentonite was examined with XRF and XRD. 75% of the cation exchange capacity was exchanged by silver ions. It was found that the sorption of chloride ions is an exothermic precipitation process because the solubility decreases with increasing temperature. In the case of iodide sorption, the dissolution of AgI was observed under high concentration of non-radioactive iodide ions, which is well known in analytical chemistry. The phenomenon occurs not only in the bulk aqueous phase but also in the interlayer space of montmorillonite.

Potential Role of Dissolved Oxygen and Manganese Concentration on the Development of Biofilms Causing Reduction in Hydraulic Capacity of a Gravity-Fed Irrigation System

Water from the Blyderiver dam in the Mpumalanga province, South Africa (SA), is used for gravity-fed irrigation. Biofilm development in the irrigation pipelines causes an increase in pipeline surface roughness leading to reduction of hydraulic capacity, resulting in water delivery below design capacity for the production of a variety of produce. The potential role of manganese (Mn) concentration on biofilm development is of interest, since the water is currently extracted at depth near the bottom of the reservoir (approximately 45-50 m when at 100% capacity) where high Mn levels were measured during four sampling events spread over two years. In the water body, dissolved oxygen (DO) and Mn concentrations showed a strong, inverse correlation, with rapid decrease in DO at increased depth, mirrored by an increase in both total and soluble Mn. The depth of this inflection point was found to correlate with the reservoir’s water level. DO concentrations typically remained constant between 8 and 9 mg l-1 in the upper regions of the water column, followed by a rapid decline to lower than 2 mg l-1 at deeper depths. Similarly, Mn concentrations remained constant with increasing depth, ranging between 10 and 100 µg l-1, followed by a rapid increase once the depth is reached where DO levels started to decline, up to 8631 µg l-1 near the bottom. In the main, 1.5 m diameter pipeline, Mn concentrations decreased with distance; from 8631 µg l-1 at the extraction point to 134 µg l-1 at 23 km downstream in the bulk aqueous phase, while in the biofilm biomass, Mn concentrations decreased from 30105.4 mg kg-1 at 4.5 km to 23501.9 mg kg-1 at 12.5 km, and 13727.7 mg kg-1 at 28.4 km downstream. This decrease in Mn concentration with distance suggests that biofilm accumulation has not yet reached a steady state.

Anomalous pH-Dependent Enhancement of p-Methyl Benzoic Acid Sum-Frequency Intensities: Cooperative Surface Adsorption Effects.

Vibrational sum-frequency generation (SFG) spectroscopy is used to determine the surface pKa of p-methyl benzoic acid (pMBA) at the air-water interface by monitoring the carbonyl and carboxylate stretching modes over the pH range of 2 to 12. The SFG intensities of pMBA and its conjugate base, p-methyl benzoate (pMBA-), exhibit an anomalously large enhancement over a narrow pH range (∼0.5) centered at pH 6.3 near the SFG-determined surface pKa, 5.9 ± 0.1. The increase in the surface pKa relative to the bulk value of 4.34 is consistent with the trend previously observed for long chain carboxylic acids in which the surface pKa is higher than the bulk solution pKa. SFG polarization studies help distinguish the orientation and number density contributions to this observed anomalous surface phenomenon. The large SFG intensity increase is attributed to an increase in the pMBA and pMBA- surface concentrations in this narrow pH range due to a cooperative adsorption effect between pMBA and pMBA-. This cooperativity is manifested only on the 2D air-water interface, where the interactions between the acid and base are not as dielectrically screened as in the aqueous bulk phase. Surface effects are critical to understanding and controlling the reactivity, solubility, and behavior of organic acids at interfaces and can have an impact on biomedical applications.

Experiments and Modeling for Investigation of Oily Sludge Biodegradation in a Wastewater Pond Environment

Historic operating and abandoned refineries frequently contain ponds or lagoons that contain oily sludge from historic wastewater treatment processes and separator sludge disposal activities that occurred prior to the implementation of regulations forbidding such disposal. These oily sludge-containing wastewater ponds represent a long-term liability at older operating refineries or abandoned refinery sites. Dewatering and solidification/stabilization are the most common technologies used to treat these sludges; however, these approaches are labor, equipment, and material-intensive. For sites where the time required to complete treatment is not a high priority, biodegradation treatment may be effective for final site remedy. The objective of this study was to investigate potential improvements in oily material biodegradation using dispersants and petroleum-degrading microbial consortia, along with the modeling of this system. The oil dispersed with mixing or remaining in the bulk aqueous phase with biodegradation was measured using methods from a dispersant effectiveness test. The experimental results indicated that mixing at levels of 200 rpm or higher resulted in positive effects on both the extent of hydrocarbon dispersion (80 to 90% of oil dispersed) and the biodegradation of the oil phase (50 to nearly 100% degraded), while the modeling results, taken along with the experimental results, indicated smaller dispersed phase droplet sizes and promoted more efficient biodegradation.

Polymer Type Impacts Amorphous Solubility and Drug-Rich Phase Colloidal Stability: A Mechanistic Study Using Nuclear Magnetic Resonance Spectroscopy.

The polymer used in an amorphous solid dispersion (ASD) formulation plays a critical role in dosage form performance. Herein, drug-polymer interactions in aqueous solution were evaluated in order to better understand the dispersion stability of the colloidal drug-rich phase generated when the amorphous solubility is exceeded. The amorphous solubility (Sa,IBP) of ibuprofen (IBP) decreased when hypromellose (HPMC) or polyvinylpyrrolidone/vinyl acetate (PVP-VA) were present in solution. Solution nuclear magnetic resonance (NMR) spectroscopy revealed that a large amount of HPMC and PVP-VA distributed into the IBP-rich phase. The mixing of HPMC and PVP-VA with the IBP-rich phase led to the decreased Sa,IBP. In contrast, the charged amino methacrylate copolymer (Eudragit E PO, EUD-E) showed minimal mixing with the IBP-rich phase; however, this polymer did lead to solubilization of IBP in the bulk aqueous phase. Although the IBP-rich phase generated by dissolving IBP at concentrations above Sa,IBP rapidly coarsened followed by creaming in the absence of polymer, all of the polymers stabilized the IBP dispersion to some extent. The droplet size of the IBP-rich phase immediately after formation was around 300 nm in HPMC and PVP-VA solutions, and around 800 nm in the EUD-E solution. The mixing of the former two polymers with the drug-rich phase is thought to account for the smaller droplet size. Despite a smaller initial size, the dispersion stability of the IBP-rich droplets was relatively poor in the presence of PVP-VA. In contrast, the coalescence of the IBP-rich droplets was effectively suppressed by the steric repulsion and electrostatic repulsion derived from adsorbed HPMC and EUD-E, respectively. The present study highlights the complex effects of a polymer on the drug amorphous solubility and colloidal stability, which should be considered when optimizing ASD formulations with the goal of maximizing drug absorption.

The study on the properties of the newly extended Gemini surfactants and their application potentials in the petroleum industry

In this study, the newly extended Gemini surfactants (EGSs) were studied as potential candidates in the petroleum industry applications. The performances of EGSs with respect to variant spacer lengths were studied through surface tension, conductivity, dynamic light scattering (DLS), interfacial tension, rheological behavior, field emission electron microscopy (FESEM), core flooding, and corrosion inhibition measurements. The surface pressure (πCMC), surface efficiency (pC20), critical micelle concentration (CMC), maximum surface excess concentration (Γmax), minimum area per molecule of surfactant at the air-water interface (Amin), average the degree of counterion binding to micelle (β), Gibb's free energy of micellization (ΔGmic), and Gibb's free energy of adsorption (ΔGads) of the EGSs were determined from surface tension and conductivity data. The results showed that the EGSs exhibited more surface activity properties, low CMCs, and spontaneously adsorbed at the air-water interface and micellized in the bulk aqueous phase. The surfactants reduced the oil-water interfacial tension (IFT) to ultralow values (10−3 mN/m) at low concentration, and it decreased substantively to very ultralow values (10−4 mN/m) due to the addition of inorganic salts. Also, they exhibited fascinating viscosifying effect and viscoelastic behavior at the experimental temperatures (30 °C–60 °C). The rheological behaviors were influenced by the formation of entangled micelles in aqueous solutions. Furthermore, through core flooding, EGS1 increased oil recovery by 12.30% which is an interesting incremental recovery. Besides, the EGSs surfactants showed high anticorrosion efficacy on A3 carbon steel in 1 M HCl aqueous solution and the inhibitive action mechanism was revealed to be by creating a protective film on the carbon steel surface through physisorption.Overall, the surface activity, interfacial activity, rheological behaviors, and anticorrosion property were dependent on the length of the spacer group. The surfactants, particularly EGS1 demonstrated a more promising interfacial activity and rheological behavior for enhanced oil recovery (EOR) in heterogeneity reservoirs as well as a remarkable anticorrosion property.

Insight into the Mechanisms Driving the Self-Assembly of Functional Interfaces: Moving from Lipids to Charged Amphiphilic Oligomers.

Polymer-stabilized liquid/liquid interfaces are an important and growing class of bioinspired materials that combine the structural and functional capabilities of advanced synthetic materials with naturally evolved biophysical systems. These platforms have the potential to serve as selective membranes for chemical separations and molecular sequencers and to even mimic neuromorphic computing elements. Despite the diversity in function, basic insight into the assembly of well-defined amphiphilic polymers to form functional structures remains elusive, which hinders the continued development of these technologies. In this work, we provide new mechanistic insight into the assembly of an amphiphilic polymer-stabilized oil/aqueous interface, in which the headgroups consist of positively charged methylimidazolium ionic liquids, and the tails are short, monodisperse oligodimethylsiloxanes covalently attached to the headgroups. We demonstrate using vibrational sum frequency generation spectroscopy and pendant drop tensiometery that the composition of the bulk aqueous phase, particularly the ionic strength, dictates the kinetics and structures of the amphiphiles in the organic phase as they decorate the interface. These results show that H-bonding and electrostatic interactions taking place in the aqueous phase bias the grafted oligomer conformations that are adopted in the neighboring oil phase. The kinetics of self-assembly were ionic strength dependent and found to be surprisingly slow, being composed of distinct regimes where molecules adsorb and reorient on relatively fast time scales, but where conformational sampling and frustrated packing takes place over longer time scales. These results set the stage for understanding related chemical phenomena of bioinspired materials in diverse technological and fundamental scientific fields and provide a solid physical foundation on which to design new functional interfaces.

Enhancing aqueous stability and radiative-charge-transfer efficiency of CsPbBr3 perovskite nanocrystals via conductive silica gel coating

The poor aqueous stability of perovskite nanocrystals (NCs) limits their electrochemical applications. Herein, we reported a waterproof and conductive silica gel shell encapsulating CsPbBr3 NCs, enhancing its aqueous stability and radiative-charge-transfer efficiency. Upon introducing small volume of CsBr aqueous solution in hexane containing tetramethoxysilane (TMOS) and Cs4PbBr6 NCs, the conversion reaction of Cs4PbBr6 → CsPbBr3+3CsBr was triggered to form Cs4PbBr6@CsPbBr3@silica gel (CsBr) hybrid. The silica gel shell can block the contact between CsPbBr3 NCs and bulk aqueous phase. The CsBr enclosed in the silica gel can reduce the conversion rate and increase dramatically the electrical conductivity of the silica gel. The electrochemiluminescence (ECL) of CsPbBr3 NCs in aqueous phase was enhanced greatly. The strong ECL of CsPbBr3 NCs in the hybrid was still observed after stored in CsBr solution for 30 day. The as-obtained perovskite hybrid displays improved electrochemical charge-injecting performance and radiative-charge-transfer in ECL. Annihilation ECL demonstrates that all the electrons injected onto the perovskite hybrid can recombine with the holes injected onto it for light-emitting. Both annihilation and co-reactant ECL, as well as photoluminescence reveal that encapsulating CsPbBr3 NCs into a conductive and waterproof silica gel shell is favorable to enhance aqueous performance of perovskite NCs with negligible effects on their excited states. The ECL of the core-shell perovskite hybrid was applied to detect dopamine in the concentration range of 0.01–10 μM, with the limit of detection of 3 nM.

Modern theory of energy coupling and ATP synthesis. Violation of Gauss’s law by the chemiosmotic theory and validation of the two-ion theory

Adenosine triphosphate (ATP) is the universal biological energy fuel, or nature’s gasoline. The vast quantities of ATP required for sustenance of living processes in cells are synthesized by oxidative phosphorylation and photosynthesis. The chemiosmotic theory of energy coupling was proposed by Mitchell more than 50 years ago but has a contentious history. Part of the accumulated body of experimental evidence supports Mitchell’s theory, and part of the evidence conflicts with the theory. Although Mitchell’s theory was strongly criticized by several prominent scientists, the controversy was never resolved. Certain theoretical arguments and electrostatic calculations were originally made to justify the central tenet of the chemiosmotic theory of electrogenic proton transfer and violation of electrical neutrality in bulk aqueous phases by creation of a delocalized field. However, these calculations have not been scientifically scrutinized previously. Here it is proved from first principles that the original physical arguments and calculations made in support of steady state electrogenic ion transfer and chemiosmosis violate Gauss’s law. Nath’s two-ion theory of energy coupling in which the field is local, and ion translocation is dynamically electrogenic but overall electroneutral is shown to satisfactorily resolve the difficulties. Characterization of length scales in mitochondrial systems is shown to impose strong constraints on possible mechanisms of energy transduction. Some biological implications for energy coupling, transduction and ATP synthesis arising as a result of the above analysis are discussed. Examples of several other biological processes where the new theory is useful such as apoptosis, muscle contraction, the joint multisite regulation of oxidative phosphorylation and the Krebs cycle, and hindered protein aggregation arising from ATP’s hydrotropic properties are outlined.

Understanding the Coacervate-to-Vesicle Transition of Globular Fusion Proteins to Engineer Protein Vesicle Size and Membrane Heterogeneity.

Protein-rich coacervates are liquid phases separate from the aqueous bulk phase that are used by nature for compartmentalization and more recently have been exploited by engineers for delivery and formulation applications. They also serve as an intermediate phase in an assembly path to more complex structures, such as vesicles. Recombinant fusion protein complexes made from a globular protein fused with a glutamic acid-rich leucine zipper (globule-ZE) and an arginine-rich leucine zipper fused with an elastin-like polypeptide (ZR-ELP) show different phases from soluble, through an intermediate coacervate phase, and finally to vesicles with increasing temperature of the aqueous solution. We investigated the phase transition kinetics of the fusion protein complexes at different temperatures using dynamic light scattering and microscopy, along with mathematical modeling. We controlled coacervate growth by aging the solution at an intermediate temperature that supports coacervation and confirmed that the size of the coacervate droplets dictates the size of vesicles formed upon further heating. With this understanding of the phase transition, we developed strategies to induce heterogeneity in the organization of globular proteins in the vesicle membrane through simple mixing of coacervates containing two different globular fusion proteins prior to the vesicle transition. This study gives fundamental insights and practical strategies for development of globular protein-rich coacervates and vesicles for drug delivery, microreactors, and protocell applications.

New sulfonate Gemini surfactants: synthesis and evaluation for enhanced oil recovery applications

In this work, a series of new sulfonate Gemini surfactants (abbreviated as m-3-m) were studied as an attempt to develop a single surfactant that can effectively reduce the oil-water interfacial tension to ultralow values. The novel surfactants were synthesized and characterized by 1HNMR and 13CNMR spectroscopies. The surface activeness of those surfactants at the air-water interface and thermodynamic properties in the bulk aqueous phase were investigated. The oil-water interfacial tension, viscous and viscoelastic properties of solutions were studied. The results showed that the novel surfactants exhibit fascinating surface activeness and low values of CMC; spontaneously formed micelles and adsorbed at the air-water interface. They can substantially reduce the oil-water interfacial tension to ultralow values () when the surfactant concentration is less than 0.5 wt%. The surfactants possess attractive viscous and viscoelastic properties towards EOR applications through flooding methods. In accordance with the experimental studies, the surfactants are promising in formulating fluid systems with ultralow interfacial tension.

Methylamine’s Effects on Methylglyoxal-Containing Aerosol: Chemical, Physical, and Optical Changes

Methylamine, a common atmospheric amine species, is found in the gas, particle, and aqueous phases. It has been shown to form light-absorbing, oligomeric species in reactions with methylglyoxal and other aldehyde species in bulk aqueous-phase experiments and when mixed into seed aerosol as a sulfate salt. Here, we explore the influence of multiphase methylamine chemistry on aerosol production, properties, and molecular composition. When methylglyoxal aerosol particles were exposed to ∼2 ppm methylamine gas in a humid chamber, rapid browning was observed, but not growth. Aerosol bounce measurements indicated that particles became slightly more viscous and hydrophobic upon methylamine exposure. Subsequent cloud processing increased both viscosity and hygroscopicity but had little effect on browning, consistent with high-resolution mass spectrometry results showing that aerosol oligomer dicarbonyl functional groups were transformed into cationic imidazole rings. Photolytic cloud processing triggered the inco...

Probing Charged Aqueous Interfaces Near Critical Angles: Effect of Varying Coherence Length

Angle-resolved vibrational sum frequency generation experiments have been used to study the silica–water interface as a function of ionic strength. Well below the critical angle, the sum frequency intensity increases up to 10–4 M NaCl and then drops. However, near the critical angle, a plateau may be observed up to 10–4 M. We first demonstrate that this is a result of the interaction of a long Debye length at low ionic strength with a long coherence length near the critical angles. In order to account for the behavior at the lowest concentrations where surface potentials are typically large, it is necessary to consider an electrostatic potential that extends into the bulk aqueous phase beyond the Debye–Huckel approximation. Because the extent of second- and third-order contributions to the nonlinear polarization can vary with ionic strength, but not with the angle of incidence, we perform a global fit to the experimental data using our proposed model to extract the relative magnitude of the two susceptibi...

The role of turbulence in internal phosphorus release: Turbulence intensity matters

Hydrodynamic fluctuations can trigger sediment suspension concomitantly with internal phosphorus release, while the interactive effect of turbulence mixing and sediment suspension on the regulation of phosphorus dynamics is in need of deep understanding. This study addressed the changes in total phosphorus (TP), phosphate (PO43--P) and suspended sediment (SS) in the overlying water, and measured the profile of dissolved oxygen (DO), Fe(II) and soluble reactive phosphorus (SRP) across the sediment-water interface in the simulated environmental turbulence scenario, For a turbulence intensity (ε) of 3.6 × 10−3 m2/s3, the SRP flux increased hence PO43--P showed a 36.36% increase relative to its initial level. Although ε of 1.3 × 10−2 m2/s3 benefited the delivery of oxygen from the bulk aqueous phase to the upper sediment which can trigger the formation of Fe oxides and hydroxides, the turbulence-induced phosphorus diffusion from the sediment exceeded its inactivation and resulted in a large SRP flux. However, a protion of the released PO43--P can be immobilized through SS adsorption and biotic (likely cyanobacteria) assimilation. Higher turbulence intensities (ε of 3.3 × 10−2 and 7.4 × 10−2 m2/s3) led to an approximately 40-fold increase in TP concentration and a significant increase in sediment suspension, which contributed to the immobilization of a majority of the phosphate through adsorption; thus, the PO43--P concentrations in the overlying water displayed 47.75% and 41.67% decline, respectively. This study also confirmed the sequential phosphorus buffer mechanisms associated with increasing turbulence intensities. With an ε of 3.6 × 10−3 m2/s3, bounding to Fe ion had a significant impact on phosphorus inactivation but with an ε of 7.4 × 10−2 m2/s3, the main immobilization mechanism is switched to phosphorus adsorption from the large quantity of suspended sediment.

Managing efficacy and toxicity of drugs: Targeted delivery and excretion

Medicine is a natural companion of mankind in the present era for mere survival from the deadly diseases in ever-increasing polluted environments. Hence, in recent years, major focus of pharmaceutical, medicinal and biophysical research has been navigated in exploring and developing new and simple avenues to enhance the efficacy of the administered drugs on one hand and to get rid of, or at least reduce, the toxic side effects of the excess drugs accumulated in human body on the other. A potential approach to amplify the efficacy of the administered drug is to develop proficient targeted drug delivery systems (DDSs). This review provides an essence of some newly developed simple but prospective strategies on enhancing the efficacy of drugs/bioactive molecules exploiting various drug delivery systems like micelles, cyclodextrins, liposomes etc. to serve the purpose of targeted delivery towards DNA, by endogenous and/or exogenous means. Improved bio-availability and solubilization of ionic drugs within the less polar target regions from the bulk aqueous phase has also been achieved through the introduction of some physiologically permissible salts. In the other context, in vitro and in vivo studies demonstrate a simple technique for easy removal of the excess adsorbed drug molecules from the cell membranes/lipid bilayers by exploiting health-amiable supramolecular assemblies.In this review, we summarize the recent experimental findings, mostly from our lab, encompassing the development of simple biocompatible methods to enhance the benevolent role of drugs through their safe, effective and convenient administration. It also presents easy and effective means to remove the excess adsorbed drugs from human body to diminish their malign effects. These prospective approaches of drug delivery and excretion of drug molecules have promising roles to play from both physicochemical and pharmaceutical perspectives, ensuring enhanced bioavailability of drugs as well as disposing of drug-induced adverse side effects.

Unsaturation of the phospholipid side-chain influences its interaction with cyclodextrins: A spectroscopic exploration using a phenazinium dye

The interaction of a cationic photosensitizer Safranin-O with liposome membranes having similar surface charge (negative) but differing in the presence of saturation on the lipid side-chain has been studied. To this end, dimyristoyl-l-R-phosphatidylglycerol (DMPG) and 1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (DOPG) phospholipids were employed to prepare small unilamellar vesicles. The dye is found to bind in the headgroup region of both the liposome membranes with significantly higher affinity to DOPG lipid containing unsaturated side chain. The effects of various cyclodextrins (CDs) on the stability of the probe-bound liposome membranes have also been investigated using steady-state and picosecond-resolved fluorescence as well as dynamic light scattering techniques. The modulations of the fluorescence properties of the lipid-bound dye were exploited to rationalize the membrane destabilization following interaction with the cyclodextrins. Experimental results reveal the selective interaction of DMPG membrane with CDs leading to rupture of the integrated structure of the liposome units accompanying release of the bound probe to the bulk aqueous phase. On the contrary, no discernible interaction of the CDs was observed with DOPG liposome membrane. Our results also show the differential extents of interaction of various CDs (α-CD, β-CD, methyl-β-CD, and γ-CD) with DMPG leading to varying degrees of release of the bound-dye molecule.

A study on the kinetics of extraction of Ti(IV) from sulphate medium by Cyanex 302

The kinetics of Ti(IV)-extraction by Cyanex 302 (H2A2) were investigated by measuring initial Ti(IV)-transfer flux, using a constant interfacial area stirring cell, operated at 3 Hz. The empirical flux equation, at 293 K, is: F = 10−4.40 [Ti(IV)] (1 + 233[H+])−1 [H2A2](o)0.5 (1 + 3.20[SO42−])−1 (F in kmol/m2 s and [ ] terms are in kmol/m3). The activation energy, Ea is measured to be (36–58) × 103 kJ/kmol depending on experimental conditions. The enthalpy change on activation, ΔS±, is always highly negative. Analysis of the flux equation has been done, at various concentration regions of H+ and SO42−, to elucidate the mechanism of extraction. The rate-determining chemical reaction step, irrespective of extraction condition, appears as: TiO2+ + A− → TiOA+. This step occurs in the bulk aqueous phase via an SN2 mechanism. The pseudo first order rate constant for the system is 7.5–55 times smaller than the maximum mass transfer coefficient attainable in a Lewis cell. This indicates that the process is chemically controlled or at least mixed controlled.

Spontaneous nano-emulsification with tailor-made amphiphilic polymers and related monomers

In general, nano-emulsions are submicron droplets composed of liquid oil phase dispersed in liquid aqueous bulk phase. They are stable and very powerful systems when it regards the encapsulation of lipophilic compounds and their dispersion in aqueous medium. On the other hand, when the properties of the nano-emulsions aim to be modified, e.g. for changing their surface properties, decorating the droplets with targeting ligands, or modifying the surface charge, the dynamic liquid / liquid interfaces make it relatively challenging. In this study, we have explored the development of nano-emulsions which were not anymore stabilized with a classical low-molecular weight surfactant, but instead, with an amphiphilic polymer based on poly(maleic anhydride-alt-1-octadecene) (PMAO) and Jeffamine®, a hydrophilic amino-terminated PPG/PEG copolymer. Using a polymer as stabilizer is a potential solution for the nano-emulsion functionalization, ensuring the droplet stabilization as well as being a platform for the droplet decoration with ligands (for instance after addition of function groups in the terminations of the chains). The main idea of the present work was to understand if the spontaneous emulsification –commonly performed with nonionic surfactants– can be transposed with amphiphilic polymers, and a secondary objective was to identify the main parameters impacting on the process. PMAO was modified with two different Jeffamine®, additionally different oils and different formulation conditions were evaluated. As a control, the parent monomer, octadecyl succinic anhydride (OSA) was also modified and studied in the similar way as that of polymer. The generated nano-emulsions were mainly studied by dynamic light scattering and electron microscopy, that allows discriminating the crucial parameters in the spontaneous process, originally conducted with polymers as only stabilizer.

Nitrogen-containing secondary organic aerosol formation by acrolein reaction with ammonia/ammonium

Abstract. Ammonia-driven carbonyl-to-imine conversion is an important formation pathway to the nitrogen-containing organic compounds (NOCs) in secondary organic aerosols (SOAs). Previous studies have mainly focused on the dicarbonyl compounds as the precursors of light-absorbing NOCs. In this work, we investigated whether acrolein could also act as an NOC precursor. Acrolein is the simplest α, β-unsaturated mono-carbonyl compound, and it is ubiquitous in the atmosphere. Experiments probing multiphase reactions of acrolein as well as bulk aqueous-phase experiments were carried out to study the reactivity of acrolein towards ammonia and ammonium ions. Molecular characterization of the products based on gas chromatography mass spectrometry, high-resolution mass spectrometry, surface-enhanced Raman spectrometry and ultraviolet/visible spectrophotometry was used to propose possible reaction mechanisms. We observed 3-methylpyridine (commonly known as 3-picoline) in the gas phase in Tedlar bags filled with gaseous acrolein and ammonia or ammonium aerosols. In the ammonium-containing aqueous phase, oligomeric compounds with formulas (C3H4O)m(C3H5N)n and pyridinium compounds like (C3H4O)2C6H8N+ were observed as the products. The pathway to 3-methylpyridine was proposed to be the intramolecular carbon–carbon addition of the hemiaminal, which resulted from sequential carbonyl-to-imine conversions of acrolein molecules. The 3-methylpyridine was formed in the aqueous phase, but some of the 3-methylpyridine could revolatilize to the gas phase, explaining the observation of gaseous 3-methylpyridine in the bags. The (C3H4O)2C6H8N+ was a carbonyl-to-hemiaminal product from acrolein dimer and 3-methylpyridine, while the oligomeric products of (C3H4O)m(C3H5N)n were polymers of acroleins and propylene imines formed via carbonyl-to-imine conversion and condensation reactions. The pH value effect on the liquid products was also studied in the bulk aqueous-phase experiments. While the oligomeric compounds were forming in both acidic and alkaline conditions, the pyridinium products favored moderately acidic conditions. Both the oligomeric products and the pyridinium salts are light-absorbing materials. This work suggests that acrolein may serve as a precursor of light-absorbing heterocyclic NOCs in SOA. Therefore, secondary reactions of α, β-unsaturated aldehydes with reduced nitrogen should be taken into account as a source of light-absorbing NOCs in SOA.

Controlling the Kinetics of Self-Reproducing Micelles by Catalyst Compartmentalization in a Biphasic System.

Compartmentalization of reactions is ubiquitous in biochemistry. Self-reproducing lipids are widely studied as chemical models of compartmentalized biological systems. Here, we explore the effect of catalyst location on copper-catalyzed azide–alkyne cycloadditions which drive the self-reproduction of micelles from phase-separated components. Tuning the hydrophilicity of the copper-ligand complex, so that hydro-phobic or -philic catalysts are used in combination with hydro-philic and -phobic coupling partners, provides a wide range of reactivity patterns. Analysis of the kinetic data shows that reactions with a hydrophobic catalyst are faster than with a hydrophilic catalyst. Diffusion-ordered spectroscopy experiments suggest compartmentalization of the hydrophobic catalyst inside micelles while the hydrophilic catalyst remains in the bulk aqueous phase. The autocatalytic effects observed can be tuned by varying reactant structure and coupling a hydrophilic alkyne and hydrophobic azide results in a more pronounced autocatalytic effect. We propose and test a model that rationalizes the observations in terms of the phase behavior of the reaction components and catalysts.