Hexane Solution Research Articles

Optical Activity and Optical Anisotropy in Photomechanical Crystals of Chiral Salicylidenephenylethylamines.

Introducing chirality into photomechanical crystals is beneficial for the diversification of mechanical motion. Measurement of the chiroptical and optical anisotropic properties of chiral crystals is indispensable for evaluating photomechanical crystals. The platelike crystals of S- and R-enantiomers of photochromic N-3,5-di-tert-butylsalicylidene-1-phenylethylamine in enol form (enol-(S)-1 and enol-(R)-1) caused bending motion with twisting upon ultraviolet (UV) light irradiation, due to shrinkage along the length and width directions of the irradiated surface, based on the optimized crystal structure of the photoisomerized trans-keto-(S)-1. By employing the generalized high-accuracy universal polarimeter (G-HAUP), optical anisotropic (linear birefringence, LB; linear dichroism, LD) as well as chiroptical (circular birefringence, CB; circular dichroism, CD) spectra of both the enantiomeric crystals on the (001) face were simultaneously measured before and under continuous UV irradiation. The LD peak was observed at 330 nm in the negative sign, derived from the π-π* transition of the intramolecularly hydrogen-bonded salicylidenimino moiety. The CD spectra of the S and R crystals revealed the negative and positive Cotton effect at 330 nm, respectively, and new peaks appeared at 460 nm under UV light irradiation due to photoisomerization to the S and R trans-keto isomers at around 10% conversion. The CB and CD spectra evaluated by the HAUP measurement were opposite to those measured in the hexane solution, as well as those simulated by quantum chemical calculation. The dissymmetry parameter, g, of the enol-(S)-1 crystal along the c axis (0.013) was approximately 10 times larger than the g values in the solution (0.0010) and by calculation (0.0016).

Dynamics of the sorption of phosphatidylcholine by mesoporous composites based on MCM-41

The possibility of predicting the breakthrough curves of a phospholipid (PL) during its sorption by mesoporous composites based on MCM-41 using models of the dynamics of sorption that consider the kinetics of adsorption (the Thomas model) and mixed diffusion (the asymptotic model) is demonstrated using phosphatidylcholine (PC) as an example. The effect the kinetic parameters have on the tailing of the sorption front with respect to the mixed diffusion limitation of the sorption of nonpolar biologically active substances (BASes) is shown. It is found that the ordered structure of composite materials based on MCM-41 ensures a high rate of mass transfer and thus little tailing of the sorption front, when compared to sorbents with a lower degree of order (silica gel and polymer materials) during the sorption of a phospholipid under dynamic conditions. Based on calculations of the parameter of pattern Λ under the conditions of the dynamic mode of sorption in mixed diffusion kinetics, it is shown that the sorption of phosphatidylcholine from hexane solutions by mesoporous composites based on MCM-41 allows the sorption chromatographic process to proceed in the most advantageous (quasi-equilibrium) mode.

Synthesis of thin film composite polyamide membranes: Effect of monohydric and polyhydric alcohol additives in aqueous solution

Thin film composite (TFC) polyamide (PA) membranes are the most widely used membranes in current water filtration processes. Over the past decade, extensive efforts have been made to improve the permeation properties of the TFC PA membranes via different techniques. In the present work, the effect of incorporating monohydric and polyhydric alcohols into the aqueous solution on surface morphology and permeation properties of resulting TFC PA membranes was studied. The TFC PA membranes were prepared by interfacial polymerization (IP) reaction between m-phenylenediamine (MPD)-aqueous and trimesoyl chloride (TMC)-hexane solutions over polyethersulfone (PES) support. Different concentrations of ethanol (C2H6O), ethylene glycol (C2H6O2), and xylitol (C5H12O5) were added into the MPD-aqueous solution. The results showed that addition of alcohols with low molar volumes such as ethanol and ethylene glycol significantly improved water flux of the synthesized membranes. However, in the case of alcohols with larger molar volumes, like polyhydric xylitol, the water flux enhanced by increasing the alcohol concentration up to ~1.0wt%, and then decreased, suggesting the presence of an optimum concentration of xylitol. This observation indicated the presence of a complex interaction between the hydrophilic hydroxyl groups and hydrophobic aliphatic carbon chain in the structure of large alcohol molecules. Furthermore, all the modified membranes showed higher rejection percentage than the original membrane which is highly desirable for fabrication of high-performance TFC membranes. The findings of this study provide insight into the synergistic effects of structural properties and surface characteristics, which are altered by the addition of alcohols, on the permeation properties of the TFC membranes.

Nanopowders of gallium nitride GaN surface functionalized with manganese

Four GaN nanopowders of systematically varying surface properties, prepared via an anaerobic synthesis method from gallium imide (ammonia assisted decomposition in the range 600–975 °C), were subjected to functionalization with manganese centers. Each powder was slurried in a diluted hexane solution of manganese (II) bis{bis[trimethylsilyl]amide} Mn{N[Si(CH3)3]2}2 and stirred overnight at ambient conditions. This was followed by filtering out of the solid, rinsing it with hexane to remove excess of the manganese precursor, and evacuating volatiles. The raw solid with some adsorbed Mn precursor was then subjected to transamination/deamination chemistry at 200 °C, 18 h, under a flow of ammonia to afford Mn surface-functionalized GaN nanopowders. The powders were thoroughly characterized including investigation of their magnetic properties with a SQUID magnetometer. They were confirmed to have tightly bound manganese and significantly modified surface properties with relatively decreased BET specific surface areas and helium densities. Magnetic measurements were consistent with the formation of a paramagnetic surface (Ga,Mn)N-type of phase and some antiferromagnetic by-product, the latter formed from adventitious oxidation of excessive quantities of the manganese precursor.

Small-angle x-ray scattering study of polymer structure: Carbosilane dendrimers in hexane solution

The three-dimensional organization of monodisperse hyper-branched macromolecules of regular structure—carbosilane dendrimers of zero, third, and sixth generations—has been studied by small-angle X-ray scattering (SAXS) in solution. The use of modern methods of SAXS data interpretation, including ab initio modeling, has made it possible to determine the internal architecture of the dendrimers in dependence of the generation number and the number of cyclosiloxane end groups (forming the shell of dendritic macromolecules) and show dendrimers to be spherical. The structural results give grounds to consider carbosilane dendrimers promising objects for forming crystals with subsequent structural analysis and determining their structure with high resolution, as well as for designing new materials to be used in various dendrimer-based technological applications.

Synthesis, crystal structure and photoluminescence study of green light emitting bis(1[(4-butylphenyl)imino]methyl naphthalen-2-ol) Ni(II) complex

Synthetically feasible and cost effective Ni(II) complex phosphor (4) as green organic light emitting diode (OLED) was prepared by using Schiff base 1-[(4-butylphenyl)imino]methyl naphthalen-2-ol (3). The single crystals of Ni(II) complex were grown from chloroform and hexane (1:1 v/v) solution. The green crystals of the complex were characterized by using single crystal XRD studies and were evaluated for their photophysical properties. From the Diffused Reflectance Spectrum of the complex, the measured band gap energy was found to be 1.83 eV and the PL spectrum of the complex showed emission peak at 519 nm. The excitation peaks at 519 nm were appeared at 394 nm and 465 nm. The Commission Internationale De L'Eclairage (CIE) chromaticity diagram indicated that, the complex exhibit green color. Hence, Ni(II) complex (4) could be a promising green OLED for developing strong electroluminescent materials for flat panel display applications.

Assessment of solubility and viscosity of ultra-high molecular weight polymeric thickeners in ethane, propane and butane for miscible EOR

Natural gas liquid (NGL), a mixture consisting primarily of ethane, propane, and butane, is an excellent enhanced oil recovery (EOR) solvent. However, NGL is typically about ten times less viscous than the crude oil within the carbonate or sandstone porous media, which causes the NGL to finger through the rock toward production wells resulting in low volumetric sweep efficiency in five-spot patterns or during a linear drive displacement. The viscosity of candidate polymeric NGL thickeners is measured with a windowed, close-clearance falling ball viscometer, and an expression for the average shear rate associated with this type of viscometer is derived. High molecular weight polydimethyl siloxane (PDMS, Mw 9.8 105) can thicken ethane, propane and butane, but the viscosity enhancement is very modest (e.g. a doubling of butane viscosity with 2% PDMS at 7MPa and 25°C), making field application of PDMS unlikely. A dilute concentration of a drag-reducing agent (DRA) poly-α-olefin that has an average molecular weight greater than 2.0 107 is more promising as a potential thickener for liquid butane, liquid propane and liquid or supercritical ethane. The DRA polymer, which is introduced as an extremely viscous 1% or 2% solution in hexane, is soluble in butane and propane at 25–60°C and concentrations up to at least 0.5wt% at pressures slightly above the vapor pressure of butane or propane. The DRA polymer is much more difficult to dissolve in ethane, however, requiring pressures of more than 20MPa. The DRA polymer is especially effective for thickening butane (e.g. a 4.8-fold viscosity increase at 25°C, 55.16MPa and 0.2wt% DRA). The DRA is less effective for increasing propane viscosity (e.g. a 2.3-fold viscosity increase at the same conditions), and even less effective for thickening ethane. In general, viscosity enhancement increases with decreasing temperature, increasing pressure, and an increase in the carbon number of the light alkane, which are reflective of increased NGL solvent strength at low temperature and high pressure. Practical application of DRA during EOR may be hindered, however, by the relatively high concentration (~5000ppm) of DRA polymer required for order-of-magnitude viscosity increases, very high pressure requirements for DRA dissolution if the ethane content of the NGL is high, and the large amount of hexane that would have to be introduced if the DRA polymer if it is introduced as a solution in hexane.

Distance-Dependent Triplet Energy Transfer between CdSe Nanocrystals and Surface Bound Anthracene.

We investigate triplet energy transfer (TET) across variable-length aromatic oligo-p-phenylene and aliphatic bridges in a covalently linked CdSe nanocrystal (NC)-bridge-anthracene hybrid system. Photon upconversion measurements in saturated 9,10-diphenylanthracene hexane solutions under air-free conditions at room temperature provided the steady-state rate of TET (ket) across this interface. For flexible transmitters, ket is similar for different lengths of aliphatic bridges, suggesting that the ligands bend backward. For the rigid phenylene spacer, triplet sensitization of anthracene transmitter molecules by CdSe NCs shows a strong distance dependence, with a Dexter damping coefficient of 0.43 ± 0.07 Å(-1). The anthracene transmitter bound closest to the NC surface gave the highest quantum yield of 14.3% for the conversion of green to violet light, the current record for a hybrid platform.

Facile fabrication of white-emitting hybrid colloids and nanocomposite films using CdSe/CdS quantum dots and zinc phthalocyanines as building blocks

In this work, we have designed a facile protocol to prepare white emitting colloid solutions and polymer nanocomposite films via the self-assembly of zinc phthalocyanine (ZnPc) in the presence of semiconductor CdSe/CdS quantum dots (QD). Specifically, a dendritic zinc phthalocyanine showing two independent emission bands at blue (∼450nm) and red region (∼690nm) in N, N-dimethylformamide (DMF) solution was synthesized by using a biphenyl phthalonitrile based precursor. In order to fulfill the missing green emission band and overcome the strong intermolecular aggregation tendency of ZnPc that normally results to obviously quenched fluorescence in solution, an ultrasmall sized CdSe/CdS QD with green emitting capabilities, was synthesized, surface modified with a hydrophobic capping agent (oleic acid) and dispersed uniformly in nonpolar hexane. When the hexane solution of QD was introduced to the immiscible ZnPc solution in DMF, nanoconjugates exhibiting three independent emission bands can be formulated by using ZnPc and QD as building blocks via the non-covalent hydrophobic interaction established in the incompatible DMF/hexane interface. Furthermore, the white emitting ZnPc/QD colloid solutions and nanocomposite films can be readily obtained by controlling the relative concentration of ZnPc and QD.

Mechanochemical Influence on the Stereoselectivity of Halide Metathesis: Synthesis of Group 15 Tris(allyl) Complexes

The stereochemical outcomes of reactions conducted in solution and those under mechanochemical conditions need not be the same; this is a well-established observation in organic synthesis, but few examples are known in organometallic systems. Halide metathesis is now shown to be a type of mechanochemical reaction that can produce different ratios of stereoisomers depending on whether the reagents are dissolved or ball-milled. Trihalides of As (X = I), Sb (X = Cl), and Bi (X = Cl) react with K[A′] (A′ = 1,3-(SiMe3)2C3H3) (As, Sb) or [AlA′3] (Bi) to generate the tris(allyl) complexes [EA′3]. All three complexes are found in two diastereomeric forms of C1 (R,S,S) and C3 (R,R,R) symmetry, and mechanochemical synthesis increases the C1:C3 ratio relative to that produced in hexanes solution (up to 3.3× in the case of [AsA′3]). The stereoselectivity of the metathesis in the solid state can be correlated with the asymmetric environment found in the group 15 trihalides; mechanochemical induction provides a new too...

Aggregation-Induced Emission of Platinum(II) Metallacycles and Their Ability to Detect Nitroaromatics.

Two new acceptors containing platinum-carbazole (1) and platinum-triphenylamine (2) backbones with bite angles of 90° and 120°, respectively, have been synthesised and characterised. Reactions of the rigid acceptor 1 with linear dipyridyl-based donors (3 and 4) generated [4+4] self-assembled molecular squares (5 and 6), and similar treatments with acceptor 2 instead of 1 yielded [6+6] self-assembled molecular hexagons (7 and 8). The metallacycles were characterised by multinuclear NMR spectroscopy ((1) H and (31) P) and ESI-MS. The geometries of the metallacycles were optimised by using the PM6 method. When aggregates of the metallacycles were formed by adding hexane solutions in dichloromethane, aggregation-induced emission was observed for metallacycles 5 and 7, and aggregation-caused quenching was observed for metallacycles 6 and 8. The formation of aggregates was verified by dynamic light scattering and TEM analyses. Macrocycles 5 and 7 are white-light emitters in THF. Moreover, their high luminescence in both solution and the solid state was utilised for the recognition of nitroaromatic explosives.

Solvato-polymorph of [(η6-C6H6)RuCl (L)]PF6 (L = (2,6-dimethyl-phenyl-pyridin-2-yl methylene amine)

A half-sandwich complex salt of ruthenium containing the Schiff base ligand, 2, 6-dimethyl-N-(pyridin-2-ylmethylene)aniline has been synthesized and structurally characterized. The complex salt 1, [(η6-C6H6)RuCl(C5H4NCHN(2,6-(CH3)2C6H3)]PF6 was obtained from the reaction of the ruthenium arene precursor, [(η6- C6H6)Ru(μ-Cl)Cl]2 with the Schiff base in a 1:2 ratio followed by treatment with NH4PF6. Its acetone solvate 2, [(η6-C6H6)RuCl(C5H4NCHN (2, 6- (CH3)2C6H3)]PF6. (CH3)2CO was obtained by recrystallization of 1 from a solution of hexane and acetone. 1 and 2 crystallize in the monoclinic P21/c and P21/n space groups as blocks and as prisms respectively. The ruthenium centers in 1 and 2 are coordinated to the bidentate Schiff base, to a chloride atom, and to the arene ring to give a pseudo-octahedral geometry around them. The whole arrangement is referred to as the familiar three-legged piano stool in which the Schiff base and the Cl atom serve as the base while the arene ring serve as the apex of the stool. Polymorph 2 has an acetone molecule in the asymmetric unit. Of interest is the similar behavior of the solvate on heating which shows the crystals shuttering at about 531.6 and 523.4 K for 1 and 2 respectively.

Entropic screening preserves non-equilibrium nature of nematic phase while enthalpic screening destroys it.

The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV-Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the "depletion force" model for entropic screening in hexane and "screening-self-screening" model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (-C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV-Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence.

Organic Solvent’s Effect in the Deposition of Platinum Particles on MWCNTs for Oxygen Reduction Reaction

We reported the synthesis of platinum particles anchored on the surface of multiwall carbon nanotubes (MWCNTs). The synthesis of platinum particles was carried out by microemulsion method using hexadecyltrimethylammonium bromide (CTAB) as surfactant to enhance the dispersion of platinum particles in hexane (C6), heptane (C7), and octane (C8) solutions. The effects of the microemulsion dispersion medium on the synthesis of platinum particles on MWCNTs (MWCNT/Pt) hybrid materials and their catalytic activities of the oxygen reduction reaction (ORR) in HClO4were investigated. The anchored platinum particles showed good dispersion on carbon nanotubes surface with the average particle sizes of2.65±0.60,2.89±0.68, and0.97±0.29 nm for the dispersion medium of C6, C7, and C8, respectively. The experimental results of ORR experiments indicated a relationship between the size and the dispersion media of the platinum particles; also the catalytic activity of the anchored platinum on MWCNT particles strongly depends on the dispersion medium employed in the microemulsion process.

Solvent-dependent on/off valving using selectively permeable barriers in paper microfluidics.

We report on a new way to control solvent flows in paper microfluidic devices, based on the local patterning of paper with alkyl ketene dimer (AKD) to form barriers with selective permeability for different solvents. Production of the devices is a two-step process. In the first step, AKD-treated paper (hydrophobic) is exposed to oxygen plasma for re-hydrophilization. 3D-printed masks are employed to shield certain areas of this paper to preserve well-defined hydrophobic patterns. In the second step, concentrated AKD in hexane is selectively deposited onto already hydrophobic regions of the paper to locally increase the degree of hydrophobicity. Hydrophilic areas formed in the previous oxygen plasma step are protected from AKD by wetting them with water first to prevent the AKD hexane solution from entering them (hydrophilic exclusion). Characterization of the patterns after both steps shows that reproducible patterns are obtained with linear dependence on the dimensions of the 3D-printed masks. This two-step methodology leads to differential hydrophobicity on the paper: (i) hydrophilic regions, (ii) low-load AKD gates, and (iii) high-load AKD walls. The gates are impermeable to water, yet can be penetrated by most alcohol/water mixtures; the walls cannot. This concept for solvent-dependent on/off valving is demonstrated in two applications. In the first example, a device was developed for multi-step chemical reactions. Different compounds can be spotted separately (closed gates). Upon elution with an alcohol/water mixture, the gates become permeable and the contents are combined. In the second example, volume-defined sampling is introduced. Aqueous sample is allowed to wick into a device and fill a sample chamber. The contents of this sample chamber are eluted perpendicularly with an alcohol/water mixture through a selectively permeable gate. This system was tested with dye solution, and a linear dependence of magnitude of the signal on the sample chamber size was obtained.

Solvent-Mediated Crystallization of Nanocrystal 3D Assemblies of Silver Nanocrystals: Unexpected Superlattice Ripening

Solvent–ligand interactions in colloidal nanocrystals are of significant importance as they can be used to modulate the way they pack into superlattices. Here, we demonstrate that the crystal structures of the nanocrystal superlattices made of 2.2 nm Ag nanocrystals can be controlled by using different carrier solvents. Specifically, the superlattice structures are tuned from body-centered cubic (bcc) to face-centered cubic (fcc) when varying solvents from hexane to tetrachloroethylene (TCE). Furthermore, by simultaneously annealing these two samples at different temperatures, bcc structures originating from hexane solutions are dominated by a simple coalescence mechanism, while the fcc structure stemming from TCE solutions undergoes an Ostwald ripening process that can produce a variety of binary nanocrystal superlattices such as NaCl, AlB2, NaZn13, and MgZn2, the formation of those structures being well explained by a pure entropy driven process. This is believed to be due to variations in the ligand co...

Physicochemical properties of unbleached softwood cellulose with a modified titanium tetrachloride surface

Fine powders with a modified surface have been prepared via treatment of unbleached softwood cellulose with titanium tetrachloride solutions in hexane. Titanium and chlorine have been detected in the composition of the aglomerates adsorbed onto the powder particles surfaces. Physicochemical properties of the samples have been shown to be dependent on Ti(IV) content on the modified surface.

Enhancing the performance of a phospholipase A1 for oil degumming by bio-imprinting and immobilization

When phospholipase A1 (PLA1) was bio-imprinted with 5% soybean lecithin at pH 5.0, its phospholipase (PLA) activity in lecithin–hexane solution increased by 30.9-fold and its substrate specificity was substantially enhanced. A further increase in PLA activity of the bio-imprinted PLA1 (bi-PLA1) from 562U/g to 1288U/g was obtained when 105mg diatomite/mg bi-PLA1 was incorporated as an immobilization carrier. The degumming abilities of PLA1, bi-PLA1, and immobilized bi-PLA1 (im-bi-PLA1) in crude soybean oil and crude oil–hexane (1:1 w/w) miscella were also investigated. The phosphorus content in the crude soybean oil was reduced to 7.3mg/kg from an initial level of 406.9mg/kg after incubation with 100mg/kg im-bi-PLA1 and 2% water at 50°C for 180min. In miscella degumming, the residual phosphorus content was reduced from 406.9mg/kg to 18.7mg/kg by incubation with 100mg/kg im-bi-PLA1 and 2% water at 50°C for 180min and neutralization with 3M NaOH solution. In comparison, the original PLA1 reduced the residual phosphorus content to 62.9mg/kg and 92.4mg/kg in crude oil and miscella degumming, respectively.

Characteristics of the mass transfer of phosphatidylcholine during its sorption on mesoporous composites based on MCM-41

The kinetic parameters of sorption of phosphatidylcholine on mesoporous composites based on MCM-41 are considered. It is noted that the possibility of both the diffusion and adsorption rate limitations of the process should be taken into account in the description of the kinetics of sorption of non-polar fat-soluble physiologically active compounds (PACs) from hexane solutions onto mesoporous materials of MCM- 41 type. The adequacy of using the Boyd diffusion model and the Lagergren, Ho and McKay, and Elovich models to describe the kinetics of sorption of phosphatidylcholine on mesoporous composites based on MCM-41 is shown. The contributions from diffusion limitation (internal and external) and the rate of the chemical step of adsorption to the overall rate of the sorption process are determined. It is found that the sorption of the phospholipid is a mixed diffusion process.

Preparation and photoluminescence properties of red-emitting SrMoO4:Eu nanophosphor microcapsules

We prepared SrMoO4:Eu nanophosphors with a mean size of 5 nm from Sr-oleate and Eu-oleate complexes in a hexane layer and an aqueous (NH4)6Mo7O24 solution by performing solvothermal reactions. A bright redemitting SrMoO4:Eu suspension was obtained in hexane solution. The SrMoO4:Eu suspension was found to be sufficiently hydrophobic for the formation of SrMoO4:Eu phosphor microcapsules. Melamine-formaldehyde polymers were used to prepare the SrMoO4:Eu phosphor microcapsules. We tested the SrMoO4:Eu phosphor microcapsules in a wearable outdoor application.