Mixture Of Cations Research Articles

Solid-state solar cells co-sensitized with PbS/CdS quantum dots and N719 dye and based on solid polymer electrolyte with binary cations and nanofillers

Co-sensitized solar cells have gained more attention due to the ability of energy conversion process by absorbing photons from wide range of the solar spectrum including visible and near-infrared region. TiO2 electrodes were co-sensitized with PbS/CdS core-shell quantum dots and N719 dye. PbS/CdS/N719 dye-sensitized solar cells were fabricated with poly(ethylene oxide) based solid polymer electrolyte consisting iodide/triiodide redox couple. The iodide ion conductivity of the electrolyte was enhanced by incorporating a binary iodide salt mixture of different size cations, tetrapropylammonium iodide and potassium iodide. The performance of the solar cell was further enhanced by the incorporating TiO2 P90 nanofiller in the electrolyte. The best solid-state solar cell showed a significantly higher efficiency of 4.41 % with a short-circuit current density of 8.41 mA cm−2, open-circuit voltage of 748.3 mV and a high fill factor of 70.16 % under the simulated light of 100 mW cm−2 with AM 1.5 filter. This is the first report describing the efficiency enhancement in a solid-state dye sensitized solar cell based on a solid polymer electrolyte incorporating a binary cation iodide salt and TiO2 nanofiller and a photoanode co-sensitized with PbS/CdS quantum dots and N719 dye demonstrating the cumulative effect by the mixed cation effect and co-sensitization.

Biocompatible Catanionic Vesicles from Arginine-Based Surfactants: A New Strategy to Tune the Antimicrobial Activity and Cytotoxicity of Vesicular Systems.

Their stability and low cost make catanionic vesicles suitable for application as drug delivery systems. In this work we prepared catanionic vesicles using biocompatible surfactants: two cationic arginine-based surfactants (the monocatenary Nα-lauroyl-arginine methyl ester—LAM and the gemini Nα,Nϖ-bis(Nα-lauroylarginine) α, ϖ-propylendiamide—C3(CA)2) and three anionic amphiphiles (the single chain sodium dodecanoate, sodium myristate, and the double chain 8-SH). The critical aggregation concentration, colloidal stability, size, and charge density of these systems were comprehensively studied for the first time. These catanionic vesicles, which form spontaneously after mixing two aqueous solutions of oppositely charged surfactants, exhibited a monodisperse population of medium-size aggregates and good stability. The antimicrobial and hemolytic activity of the vesicles can be modulated by changing the cationic/anionic surfactant ratio. Vesicles with a positive charge efficiently killed Gram-negative and Gram-positive bacteria as well as yeasts; the antibacterial activity declined with the decrease of the cationic charge density. The catanionic systems also effectively eradicated MRSA (Methicillin-resistant Staphylococcus Aureus) and Pseudomonas aeruginosa biofilms. Interestingly, the incorporation of cholesterol in the catanionic mixtures improved the stability of these colloidal systems and considerably reduced their cytotoxicity without affecting their antimicrobial activity. Additionally, these catanionic vesicles showed good DNA affinity. Their antimicrobial efficiency and low hemolytic activity render these catanionic vesicles very promising candidates for biomedical applications.

Synergistic effect of mixed DDA/surfactants collectors on flotation of quartz

In this study, five types of surfactants including non-ionic lipophilic surfactant Span series surfactant, non-ionic hydrophilic surfactant Tween and OP series surfactant, characteristics of both anionic and hydrophilic surfactant NaOL and triethanolamine oleate (named as OL series for short), characteristics of both cationic and hydrophilic surfactant AC1201 and AC1205 (named as AC series for short) were chosen as research subjects to investigate the relationship between the structure and synergistic ability of surfactants, focusing on the adsorption of the typical cationic collector dodecylamine (DDA) and surfactant mixture at liquid/air and solid/liquid interface to investigate the application potential of structure in the development of an effective surfactant to apply for quartz flotation. Flotation experiments, surface tension measurements, microcalorimetric experiments, interaction parameter calculation and Fourier Transform Infrared Spectroscopy (FTIR) analysis were used to analyze the characteristics of different DDA/surfactant systems and the interaction mechanism between quartz and collector mixture. The flotation results indicated that the synergistic capacity of these surfactants was in the following ranking: AC > OP > Tween > Span > OL. AC1201 showed a stronger synergistic ability than the other surfactants, accompanying with a recovery promotion over 20% compared with pure DDA. The physicochemical properties including surface activity parameters, the micelles and interfacial compositions, and interaction parameters were evaluated according to the theory of regular solutions. The surface tension and critical micelle concentration of the mixture solution decreased with the addition of the surfactant. According to the basic Rubingh equations, the interaction parameter of these surfactants was in the following ranking: OL > Span > OP > Tween > AC, indicating that the flotation recovery of quartz was negatively correlated with the interaction parameters. While there was a positive correlation between the interaction heat changes obtained from microcalorimetry and the trend from the flotation experiments. The obtained results demonstrated that it should be chosen this type of surfactant, which can be able to intensify collector adsorption at the solid/liquid interface. AC1201 has a potential for industrial application in the flotation of quartz.

Influence of additive on the aggregation behavior of drug and cationic hydrotrope aniline hydrochloride mixtures: a physicochemical assessment

AbstractWe investigated the influence of an additive (50 mmol kg–1 NaCl/300 mmol kg–1 urea [U]) on the aggregation of amphiphilic promethazine hydrochloride (PMH) drug and cationic hydrotrope–aniline hydrochloride (AnHCl) mixtures at various temperatures and ratios. The drug PMH is mostly used for the treatment of allergic symptoms. The obtained critical micelle concentration (cmc) values are well below the cmcid (ideal cmc) value, which confirms interactions between components PMH and AnHCl in the solution mixture. The micellar mole fraction (X1Rub, X1Rod, and X1id) of the first component (AnHCl) was evaluated using different models, which suggested greater involvement of AnHCl in mixed micelles (as expected); besides, the obtained micellar mole fraction values increase with increase in the mole fraction (α1) of AnHCl. The interaction parameter (β) values obtained were negative, which confirms attractive interaction or synergism among the components. Activity coefficients ( [AnHCl] and [PMH]) values are always found below one confirming the nonideality as well as attractive interaction between the components. Different physicochemical parameters evaluated suggested attractive interaction between the components (PMH and AnHCl) in all studied solvents; however, in salt media, the interaction increases to some extent, whereas in urea media, it decreases to some extent. Diverse thermodynamic parameters (Gibbs free energy [ΔGm0], enthalpy [ΔHm0], and entropy [ΔSm0]) of micellization were computed and discussed separately. The excess free energy ( ) values of all systems were negative, suggesting higher stability of formed mixed micelles as compared with singular‐component micelles.

New water-soluble colorimetric pH and metal ione sensor based on graphene quantum dot modified with alizarine red S

A new colorimetric sensor was designed for the screening pH changes in solutions, as well as, detection of some cations. The sensor preparation includes the chemical binding of alizarine red S (ARS) as a sensor of pH and cation to graphene quantum dots (GQD). Loading ARS on GQD led to the formation of water soluble sensor which finally responded to the colorimetric detection of some cations in water. Solubility and stability of the sensor in water indicate that the sensor is an ideal system for the biological and environmental applications. To demonstrate the applicability of the new sensor, the colorimetric responds of sensor were examined for some cations including Fe3+, Co2+, Ca2+, As3+, Cd2+, Hg2+, Pb2+, Sn2+, Al3+, and Cr3+. The colorimetric detections of all the ions were performable individually in a solution. In addition, GQD-ARS as a colorimetric sensor detected Co2+ at pH < 0.6 with limit of quantification 0.08 mM and Fe3+ at 0.6 < pH < 4.0 with limit of quantification 0.03 mM in the mixture of cations.

Structural Evolution of Layered Hybrid Lead Iodide Perovskites in Colloidal Dispersions

Controlling the structure of layered hybrid metal halide perovskites, such as the Ruddlesden-Popper (R-P) phases, is challenging because of their tendency to form mixtures of varying composition. Colloidal growth techniques, such as antisolvent precipitation, form dispersions with properties that match bulk layered R-P phases, but controlling the composition of these particles remains challenging. Here, we explore the microstructure of particles of R-P phases of methylammonium lead iodide prepared by antisolvent precipitation from ternary mixtures of alkylammonium cations, where one cation can form perovskite phases (CH3NH3+) and the other two promote layered structures as spacers (e.g., C4H9NH3+ and C12H25NH3+). We determine that alkylammonium spacers pack with constant methylene density in the R-P interlayer and exclude interlayer solvent in dispersed colloids, regardless of length or branching. Using this result, we illustrate how the competition between cations that act as spacers between layers, or as grain-terminating ligands, determines the colloidal microstructure of layered R-P crystallites in solution. Optical measurements reveal that quantum well dimensions can be tuned by engineering the ternary cation composition. Transmission synchrotron wide-angle X-ray scattering and small-angle neutron scattering reveal changes in the structure of colloids in solvent and after deposition into thin films. In particular, we find that spacers can alloy between R-P layers if they share common steric arrangements, but tend to segregate into polydisperse R-P phases if they do not mix. This study provides a framework to compare the microstructure of colloidal layered perovskites and suggests clear avenues to control phase and colloidal morphology.

Catanionic mixtures of surface-active ionic liquids and N-lauroyl sarcosinate: Surface adsorption, aggregation behavior and microbial toxicity

The surface activity and aggregation behavior of catanionic mixtures of imidazolium- or pyridinium-based surface-active ionic liquids (SAILs) and sodium N-lauroyl sarcosinate (Na-LS) in aqueous solution were investigated. The effects of the alkyl chain length, the polar head group and functional groups in the SAIL molecule on the interfacial properties and self-assembly of the catanionic mixtures were evaluated by surface tension and dynamic light scattering measurements. In addition, the toxicity of the catanionic surfactant mixtures against bacteria and fungi was studied. The SAIL-LS mixed systems reduced water surface tension with high effectiveness and efficiency, and had a lower critical aggregation concentration compared to the individual components. In all the catanionic systems investigated, synergistic effects caused by strong electrostatic and hydrophobic interactions resulted in negative interaction parameter values, which increased with the alkyl chain length and in the order of non-functionalized < amide-functionalized < ester-functionalized SAILs. The structure of the mixed aggregates in the SAIL-LS catanionic systems depended on the hydrophobicity of the SAIL, the micelle-vesicle transition being driven by the alkyl chain length. The catanionic systems exhibited similar microbial toxicity to that of individual SAIL components and behaved like broad-spectrum antimicrobials.

Synergistic Adsorption Mechanism of Anionic and Cationic Surfactant Mixtures on Low-Rank Coal Flotation.

Mixed surfactants have a prominent synergistic effect and show advantages in many aspects. In this work, the effects of a mixture of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the flotation of low-rank coal were studied from the wetting rate, contact angle, surface tension, and zeta potential. Furthermore, the adsorption configuration of the mixed surfactant on the surface of oxygen-containing graphite was simulated at the molecular level by molecular dynamics simulation. The experimental results show that the combustible matter recovery of low-rank coal flotation is improved using the mixed surfactant, and the contact angle test and wetting rate test confirmed the synergistic effect of the mixed surfactant. In the mixed surfactant system, the addition of SDS with an opposite charge to DTAB can reduce the mutual repulsion between DTAB molecules and enhance the degree of DTAB alignment in solution, which was analyzed by surface tension and zeta potential tests. Meanwhile, the simulation results reveal the adsorption behavior of anionic and cationic surfactants on the surface of oxygen-containing graphite from the molecular level and also verify the experimental results. This investigation provides a good understanding of the interaction mechanism of mixed surfactants in low-rank coal flotation.

Efficiency of H2O2-treated eucalyptus biochar on the removal of Cu(II), Cd(II) and Ni(II) from aqueous solution

The present work had the goal to produce H2O2-treated biochar from eucalyptus wood and testing its efficiency in the removal of heavy metals from aqueous solutions. Oxidizing treatment was performed by reacting biochar with H2O2 (10% m/m) during 4 hours at pH 8.0 and 80 °C. Fresh and H2O2-treated biochar samples were characterized by thermogravimetry and elemental analysis. Point of zero charge and specific surface area were determined. Adsorption kinetics tests with Cu were carried out and Langmuir and Freundlich isotherms were adjusted. Adsorption tests were conducted with a mixture of Cu, Ni and Cd cations in aqueous solution. The best adsorption capacity was achieved in acid pH. H2O2-treated biochar had adsorption capacity of 170.41 mg&nbsp;L?1 for Cu alone and 305.35&nbsp;mg L?1 for the mixture of metals. Adsorption was best predicted by the Langmuir isotherm (R2 = 0.9976). Despite the significant decrease in the specific surface area, the H2O2-treated biochar showed better performance in the adsorption of heavy metals compared to the original biochar, especially in the presence of more than one metallic cation.

From Electronic Waste to Suzuki-Miyaura Cross-Coupling Reaction in Water: Direct Valuation of Recycled Palladium in Catalysis.

From electronic waste to Pd-catalyzed reaction! The straightforward valuation of palladium recovered from electronic waste is reported here. Following a classical leaching stage, palladium is selectively extracted from a complex aqueous mixture of metallic cations into an organic phase. Afterwards, the judicious choice of a surfactant enables stabilization of palladium during back extraction cycles, and the direct preparation of an aqueous micellar solution, which can be employed in a model Suzuki-Miyaura cross-coupling reaction. Clean phase separation is observed, and distribution of all components between organic and aqueous phases is mastered. The proposed process avoids several waste generating steps dedicated to palladium isolation and ultimate purification, as well as the preparation of palladium pre-catalyst. This novel approach enables a better use of both natural resources and industrial wastes, through new cycles in circular economy.

Li2MnO3/LiMnBO3/MnFe2O4 ternary nanocomposites: Pechini synthesis, characterization and photocatalytic performance

Li2MnO3/LiMnBO3/MnFe2O4 ternary nanocomposites were synthesized via modified pechini sol-gel approach employing the mixture of metal cations, boric acid, ethylene glycol and ethylene diamine tetra acetic acid gelating agent. Shape and size of nanocomposites was controlled by changing molar ratio of metal ions, ethylene glycol and gelating agent. In order to confirmation of crystalline and structural features of products, analyses of X-ray diffraction, Fourier transform infrared and energy dispersive X-ray were carried out. Scanning electron microscopy and transmission electron microscopy images were taken for morphology investigation of nanostructure products. Band-gap of ternary nanocomposites calculated by UV–Vis data is 2.6 eV. Magnetic property of Li2MnO3/LiMnBO3/MnFe2O4 ternary nanocomposites investigated through vibrating sample magnetometer presents ferromagnetic behavior. Moreover, photocatalytic activity of Li2MnO3/LiMnBO3/MnFe2O4 and Li2MnO3/LiMnBO3 nanocomposites was investigated in aqueous solution via UV and visible light for degradation acid red 88 dye. Some effective parameters such as dye concentration, irradiation and nanocomposite type were evaluated for optimum removal of water pollutant dye.

Comparison of monocrystalline and secondary LiNi0.5Co0.2Mn0.3O2 cathode material for high-performance lithium-ion batteries

Secondary(S-NCM) and monocrystalline (M-NCM) LiNi0.5Co0.2Mn0.3O2 cathode materials were prepared via synthesizing Ni-Co-Mn hydroxide precursors following by heat treatment operations. The materials of S-NCM and M-NCM are characterized by various means in order to describe the microstructure in detail, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The results of the physical characterization and electrochemistry measurement identify that the 3-4 μm thick monocrystalline cathode materials exhibit lower cation mixture and avoid the cracks of the particles. Electrochemical performance tests were taken at the various voltage of 3.0–4.3/4.4 V under different temperatures (25 °C and 45 °C) respectively. The electrodes of S-NCM always show higher discharge capacity than that of M-NCM at 0.1–2 C, while the electrochemical performances of M-NCM electrode become better at a high rate (5 C), especially at a high temperature (45 °C). The M-NCM electrode reaches 101.4 mAh g−1 (61.9%, 3.0–4.3 V, 258 cycles), 112.7 mAh g−1 (63.4%, 3.0–4.4 V, 258 cycles), which exhibits better electrochemistry performance than that of S-NCM sample, demonstrating the expected properties of the micron-sized single crystal cathode. In addition, the single crystal cathode materials can alleviate side reactions and keep up the layered structures stability during the charging/discharging process. It is testified that the M-NCM cathode materials are propitious for LIBs with long-life and high-rate, and the S-NCM cathode has better performances at 3C digital products.

Tailoring thermal properties of multi-component rare earth monosilicates

This work explores the possibility of tailoring the thermal conductivity and thermal expansion of rare earth monosilicates through the introduction of multiple rare earth cations in solid solution. Six rare earth monosilicates are studied: Sc2SiO5, Y2SiO5, Nd2SiO5, Dy2SiO5, Er2SiO5, and Yb2SiO5. Four equimolar binary cation mixtures and a five-cation equimolar mixture were characterized. Thermal expansion was measured up to 1200 °C with X-Ray Diffraction (XRD) and bulk thermal conductivity was measured by Hot Disk technique. The linear coefficient of thermal expansion (CTE) of mixed-cation systems followed a rule of mixtures, with average linear CTEs between 6 - 9 × 10−6 /°C. Scandium monosilicate showed a lower linear CTE value as well as a notably lower degree of CTE anisotropy than other rare earth monosilicates. Thermal conductivity was found to decrease below rule of mixtures values through increasing heterogeneity in rare earth cation mass and ionic radii, as expected for the thermal conductivity of solid-solutions. The five-cation equimolar RE2SiO5 (RE=Sc, Y, Dy, Er, and Yb) shows a thermal conductivity of 1.06 W/mK at room temperature, demonstrating that multi-component rare earth silicates are strong candidates for novel dual-purpose thermal and environmental barrier coatings.

Dialysis of one sample drop on-line connected with electrophoresis in short capillary

An analytical apparatus is described, based on on-line connection of electrophoresis in a short capillary with a dialysis unit enabling dialysis in micro-litre sample volumes into submicro-litre volumes of an acceptor solution in a dialysing fibre. After a defined dialysis time, the dialysate from the dialysing fibre is injected into a separation capillary through an air-assisted flow-gating interface cast from PDMS. In the flow-gating injection space, the exit from the delivery capillary bringing the dialysate is placed directly opposite the entrance into the separation capillary at a distance of 380 μm. In order to enable injection of a very small volume of dialysate, the background electrolyte is forced out of the injection space with air before the injection, so that a drop of dialysate with a volume of about 0.1 μL is formed between the exit from the delivery and the entrance into the separation capillary; the dialysate is injected hydrodynamically from this dialysate drop. Then the injection space is filled with the background electrolyte and the separation is commenced. The basic properties of the apparatus were tested on model mixtures of inorganic cations (K+, Ba2+ and Na+) and organic molecules (creatinine, histidine and arginine). The applicability to real samples was tested on the determination of basic amino acids (histidine, lysine and arginine) in a blood serum sample.

Hybrid-Supported Bilayers Formed with Mixed-Charge Surfactants on C18-Functionalized Silica Surfaces.

Mixtures of cationic-anionic surfactants have been shown to spontaneously form ordered monolayers at hydrophobic-hydrophilic boundaries, including air-water and oil-water interfaces. In this work, confocal Raman microscopy is used to investigate the structure of hybrid-supported surfactant bilayers (HSSBs) formed by deposition of a distal leaflet of mixed cationic-anionic surfactants onto a proximal leaflet of n-alkane (C18) chains on the interior surfaces of chromatographic silica particles. The surface coverage of the two surfactants in a hybrid bilayer was determined from carbon analysis and the relative Raman scattering of their respective head-groups. Within the measurement uncertainty, the stoichiometric ratio of the two surfactants is one-to-one, equivalent to mixed-charge-surfactant monolayers at air-water and oil-water interfaces and consistent with the role of the head-group electrostatic interactions in their formation. When self-assembled on the hydrophobic surface, pairs of oppositely charged n-alkyl chain surfactants resemble a phospholipid (phosphatidylcholine) molecule, with its zwitterionic head-group and two hydrophobic acyl chain tails. Indeed, the structure of these hybrid-supported surfactant bilayers on C18-modified silica surfaces is similar to that of hybrid-supported lipid bilayers (HSLBs) on the same supports, but with denser and more-ordered n-alkyl chains. Hybrid-supported surfactant bilayers exhibit a melting phase transition (gel to liquid-crystalline phase) with structural and energetic characteristics similar to those of hybrid-supported bilayers prepared from a zwitterionic phospholipid of the same alkyl chain length. These mixed-charge surfactants on n-alkane-modified silica are stable in water over time (months), results that suggest the potential use of these hybrid bilayers for generating supported lipid-bilayer-like surfaces or for separation applications.

Displacive Order–Disorder Behavior and Intrinsic Clustering of Lattice Distortions in Bi‐Substituted NaNbO3

AbstractPerovskite‐like NaNbO3‐Bi1/3NbO3 solid solutions are studied to understand the interactions between octahedral rotations, which dominate the structural behavior of NaNbO3 and displacive disorder of Bi present in Bi1/3NbO3. Models of instantaneous structures for representative compositions are obtained by refining atomic coordinates against X‐ray total scattering and extended X‐ray‐absorption fine structure data, with additional input obtained from transmission electron microscopy. A mixture of distinct cations and vacancies on the cuboctahedral A‐sites in Na1−3xBixNbO3 (x ≤ 0.2) results in 3D nanoscale modulations of structural distortions. This phenomenon is determined by the inevitable correlations in the chemical composition of adjacent unit cells according to the structure type—an intrinsic property of any nonmolecular crystals. Octahedral rotations become suppressed as x increases. Out‐of‐phase rotations vanish for x &gt; 0.1, whereas in‐phase tilts persist up to x = 0.2, although for this composition their correlation length becomes limited to the nanoscale. The loss of out‐of‐phase tilting is accompanied by qualitative changes in the probability density distributions for Bi and Nb, with both species becoming disordered over loci offset from the centers of their respective oxygen cages. Symmetry arguments are used to attribute this effect to different strengths of the coupling between the cation displacements and out‐of‐phase versus in‐phase rotations. The displacive disorder of Bi and Nb combined with nanoscale clustering of lattice distortions are primarily responsible for the anomalous broadening of the temperature dependence of the dielectric constant.

Comprehensive study of the formation of stable colloids of Cu[sbnd]Al layered double hydroxide assisted by double hydrophilic block copolymers

The formation of stable aqueous colloidal suspensions of CuAl layered double hydroxide (LDH) assisted by double-hydrophilic block copolymers was investigated. It was of utmost importance since the direct preparation LDH colloids of controlled size is still a major challenge; moreover, regarding the CuAl system, the mechanism of formation of the LDH phase is not well understood yet. CuAl LDH nanoparticles were obtained by complexing Cu2+ and Al3+ cation mixture (Cu2+/Al3+ = 2) with an asymmetric poly(acrylamide)-b-poly(acrylic acid) block copolymer, followed by metal cation hydroxylation. The mechanism of formation of the CuAl LDH was studied and compared to that of MgAl LDH. ICP-MS analysis of the hybrid polyion complex (HPIC) micelles obtained at increasing complexation ratio, i. e. the ratio of the molar concentration of complexing acrylate group of DHBC to M2+ and Al3+ cations (R = AA/(M2+ + Al3+)), showed higher selectivity of DHBC toward Al3+ and, among M2+ cations, for Cu2+ than for Mg2+. Hydroxylation of the HPIC micelles led to macroscopic precipitates at R values below flocculation thresholds, i. e. R1 = 0.43 for DHBC/Cu-Al and 0.13 for DHBC/Mg-Al suspensions, while stable suspensions were formed above R1. The hydrodynamic diameter (Dh) of the colloids determined by DLS decreased from 160 to 50 nm and from 350 to 50 nm in the DHBC/Cu-Al and DHBC/Mg-Al colloids, respectively, when R increased from R1 to 1. XRD and TEM analyses of the dried colloidal suspensions (R > R1) revealed the presence of CuAl LDH and MgAl LDH phases and elemental analyses confirmed that M(II)/Al = 2. Particle sizes were lower in CuAl LDH than in MgAl LDH. Titration curves corresponding to progressive hydroxylation of DHBC/Cu(or Mg)-Al solutions at fixed complexation ratio R allowed establishing that formation of CuAl and MgAl LDH obeyed to a similar sequential mechanism in two steps but involving different aluminum hydroxide precursors according to the different pH values of precipitation. CuAl LDH was obtained by combination of aluminum poly(hydr)oxide species with dissolved copper-based species at pH ~ 5.5, while MgAl LDH resulted from combination of Al(OH)3 and dissolved Mg2+ at pH ~ 8.

Performance Evaluation of Hybrid Fibers and Nano-zeolite Modified Asphalt Micro-surfacing

Abstract Micro-surfacing is a cationic mixture for reparation and maintenance of asphalt pavement and contains polymer-modified bitumen emulsion, 100 % manufactured well-graded fine aggregate, mineral filler, water, and chemical additives. The object of this study was to extend the lifespan of a Micro-surfacing mixture against traffic loads to obtain a higher performance asphalt mixture using different additives, including Diatomite filler, nano-zeolite, styrene butadiene rubber, and glass fiber. To evaluate the performance of the mixtures, a variety of experimental tests, including the abrasion test (International Slurry Surfacing Association [ISSA] TB 100), adhesion test (ISSA TB109), and Wet Cohesion test (ISSA TB139) and Scanning Electron Microscopy, were conducted to classify Micro-surfacing quality control against traffic loads. Cohesion test results showed that adding 2 % nano-zeolite and 4 % polypropylene increased loading resistance up to 25 % (Quick Set and Quick Traffic). In addition, using 10 % of Diatomite improved abrasion resistance. It is worth noting that with an increasing dosage of asphalt emulsion, the effect of the additives will also increase. Moreover, adding 0.26 % of glass fiber in the mixtures increased bleeding resistance around 14 %.

Scalable Synthesis of Salt-free Quaternary Ammonium Carboxylate Catanionic Surfactants

Surfactants in commercial products commonly contain catanionic mixtures thus many studies of aqueous surfactant mixtures have been carried out. However, hardly any studies have been dedicated to pure catanionic surfactants often termed salt-free catanionic surfactants. One of the difficulties is in acquirement of samples with required purity due to difficult separation of these compounds from inorganic salts. In this work we present an alternative method of synthesis using dimethyl carbonate as the alkylating agent in order to obtain alkyl trimethylammonium alkanecarboxylates with medium alkyl chain lengths (6-10).

Surface activity, self-aggregation and antimicrobial activity of catanionic mixtures of surface active imidazolium- or pyridinium-based ionic liquids and sodium bis(2-ethylhexyl) sulfosuccionate

The surface activity and spontaneous formation of vesicles in aqueous solution of catanionic mixtures composed of different surface active ionic liquids (SAILs), methylimidazolium- or pyridinium-based, non-functionalized or bearing an ester or amide group in the alkyl chain, and the anionic surfactant sodium bis(2-ethyl-1-hexyl) sulfosuccinate (Na-AOT) have been studied. Furthermore, the antimicrobial activity of these catanionic mixtures against bacteria and fungi has been investigated. Catanionic mixtures were prepared by mixing aqueous solutions of SAIL-Br and Na-AOT in equimolar ratio. The resulting SAIL-AOT catanionic surfactant mixtures aggregate in vesicles and display high surface activity, enhanced interfacial adsorption and low critical aggregation concentration (cac) as compared to the individual components. The critical aggregation concentration decreases with the elongation of the alkyl chain of the ionic liquid and, for the same chain length, the cac values of SAIL-AOT mixtures follow the order, non-functionalized > amide functionalized > ester functionalized. The zeta-potential of SAIL-AOT vesicles increases from negative to positive values with the alkyl chain lengthening, consistently with the composition of the aggregates determined by the Regular Solution Theory. The vesicle formation in SAIL-AOT catanionic mixtures affects the intrinsic antimicrobial activity of individual amphiphilic components. The catanionic mixtures investigated exhibit high antimicrobial activity against fungi and most Gram-positive bacteria and low toxicity to Gram-negative microorganisms.