Toluene Medium Research Articles

Ultrafine-grained, high-strength NiAl with Al2O3 and Al4C3 nanosized particles dispersed via mechanical alloying in toluene with spark plasma sintering

A 50:50 atomic ratio of elemental Ni and Al powders were subjected to mechanical alloying (MA) in a toluene medium and were consolidated via spark plasma sintering (SPS). The transmission electron microscopy (TEM) results indicated that the ultra-fine grains (226±107nm and 307±150nm) and nanometre-sized Al2O3 and Al4C3 particles dispersed in the NiAl samples sintered at 900 and 1000°C. A high hardness of 670 HV and a compressive yield strength of 2251MPa were obtained in the NiAl sintered at 900°C. A maximum plastic strain of ~16.5% with a compressive yield strength of 2041MPa was realised for the NiAl sample sintered at 1000°C. The contributions of the grain size and particles to the strength were calculated using the appropriate strengthening models, and the calculated theoretical yield strength of the synthesised NiAl was found to closely match the experimental values.

Quantitative study of the quasiequilibrium in the system (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)-molybdenum(V)-piperidine in toluene medium

The quasiequilibrium interaction of (hydroxo)oxo-(5,10,15,20-tetraphenylporphynato)molybdenum(V) and piperidine in the toluene medium has been studied by means of chemical kinetics and spectrophotometric titration. It has been revealed that the molecular complex formation proceeds as slow irreversible salt formation reaction. It is preceded by the stages of equilibrium substitution of the hydroxo group OH-with piperidine, the outer sphere cationic complex formation [K1 (2.03±0.28)×103 M−1]; and by the coordination of the second piperidine molecule to the cationic complex (K2 1.76±0.39 M−1). The complex formation has been completely kinetically described: the rate equations and rate constants have been derived, and the rate limiting stage has been identified. In addition, the physicochemical data on the intermediates and products are presented. The prospects of application of the mixed porphyrin-containing complex as piperidine receptor, alkaloids and pharmaceuticals building block, have been justified.

The Preparation of a Molybdenum Based High Temperature Refractory Alloy by Powder Processing Route

Molybdenum-based TZC alloy having nominal composition of Mo–1.2 Ti–0.3 Zr–0.1 C (wt%) possesses several attractive features for high temperature structural applications. These include high melting point, high tensile and creep strength, high resistance to heat and corrosion, good thermal diffusivity and satisfactory welding properties. However, synthesis of TZC alloy with micro-alloying additions of Ti, Zr and C by conventional high vacuum melt-casting route is a challenging task to achieve homogeneous alloy composition in view of segregation of alloying components. Hence, in the present investigation, an alternative approach to prepare homogenous TZC alloy was adopted by a powder processing route, namely, mechanical alloying (MA) at room temperature. As, Mo is a major ingredient (~98.25%) in TZC alloy, hence, this component was prepared in the laboratory to satisfy the requirement for indigenous development of the alloy. Apart from pure elements used for the alloy preparation, carbon requirement of the alloy was fulfilled from toluene medium used during milling. MA powder that was obtained exhibited fine grained microstructure with nano sized grains available in the range of 10-20 nm having polyhedral shapes. A high rate of densification, close to theoretical density, was achieved during sintering of MA powder between the temperature ranges of 1500-1700°C. XRD analysis confirmed the formation of carbides phases and the composition of the sintered alloy nearly matched the desired alloy composition. Transmission electron microscopy (TEM) studies have revealed the uniform distribution of carbides in the MA alloy having round shapes.

Terpolymerization of carbon monoxide, ethylene and styrene in the presence of supported palladium catalyst

Terpolymers of carbon monoxide with ethylene and styrene are synthesized in the presence of supported palladium catalyst in toluene and heptane medium for the first time. The terpolymerization rate exceeds the rate of carbon monoxide and ethylene copolymerization. The maximum terpolymer yield amounts 7.9 g per g of supported catalyst per hour or 321 g per g of palladium per hour. The influence of reaction temperature, pressure, 1.4-benzoquinone amount and co-monomers mole ratio on the yield and the composition of terpolymer have been studied. The NMR 13C data obtained testify to a distribution of ethylene and styrene units in terpolymer with the predominance of short blocks at equal contents of comonomer units.

Hydroformylation of alkenes in supercritical carbon dioxide catalyzed by rhodium complexes with amidophosphite derivatives of carboranes

New carborane-containing amidophosphites are synthesized. Their effectiveness as ligands in the Rh-catalyzed hydroformylation of alkenes in supercritical carbon dioxide (SC-CO2) is tested. It is shown that the use of carboranylamidophosphites makes it possible to achieve a high degree of conversion at a low catalyst loading. In the SC-CO2 medium, the regioselectivity is higher as compared to the toluene medium.

Effect of PEG-200 and Tween-20 on photoisomerization of 1-alkyl-2-(arylazo)imidazoles in toluene

The photoisomerization of 1-alkyl-2-(arylazo)imidazole, trans-to-cis, has been studied in the matrix of PEG-200 and Tween-20 in toluene medium by UV light irradiation. The trans and cis-isomers have different absorption spectra. The cis-to-trans isomerization proceeds slowly in visible light irradiation while it is appreciably fast in thermal process. The rate of trans-to-cis isomerization is decreased by 30–60% in presence of PEG-200 and Tween-20. The quantum yield of the photoisomerization is also decreased by 35–55% and follows the rate sequence: free state>PEG-200-phase>Tween-20 phase. The activation energy (Ea) of cis→trans, thermal backward isomerization, is reduced in PEG-200 and Tween-20 phase following free state>PEG-200-phase>Tween-20-phase. The branched polyhydroxo structure of Tween-20 may help to wrap the polar photochrome more efficiently than major ether functionalized PEG-200 and stabilizes trans-isomer.

Influence of temperature on AC conductivity of nanocrystalline CuAlO2

Nanocrystalline CuAlO2 was synthesized by mechanical alloying of Cu2O and α-Al2O3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies (f co ). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

Refinement and carbon incorporation effects on the superconducting properties of MgB2 through wet milling process of low purity boron powder

The wet milling effects of boron (B) powder on the full width at half maximum (FWHM) value of X-ray reflexes, grain size, carbon (C) substitution, critical temperature (Tc), critical current density (Jc), irreversibility field (Hirr), and upper critical field (Hc2) have been investigated for MgB2 bulk superconductors. The semi-crystalline B powder with a low purity of 95–97% was refined with different milling times of 1 to 15h using a toluene medium. As a result of B powder milling, the particle size of the B powder decreased and the semi-crystalline phase became an amorphous phase. As the milling time increased, Tc of MgB2 bulk decreased by the deterioration of the crystallinity and Jc increased over the applied magnetic fields. With the refinement of the B powder, the grain boundary pinning increased due to smaller MgB2 grain size. In addition, it was found that a C substitution for the B site occurred from a toluene medium during wet milling process. The increased electron scattering due to an increase of the defects like grain boundary and lattice disorder by C substitution led to enhance the superconducting properties with an increase of the FWHM value of the MgB2 peaks and a decrease of the Tc. The MgB2 prepared from B powder mechanically milled for 7h showed the highest magnetic Jc of approximately 104A/cm2 at 5K and 8T. The Hc2 and Hirr were also improved due to the increase of grain boundary pinning and lattice disorder as a result of milling in toluene.

Influence of the energy of charge transfer on non-covalent interactions between fullerenes and a designed bisporphyrin

The present paper reports the spectroscopic and theoretical investigations on the formation of supramolecular complexes of a designed bisporphyrin (1) with C60 and C70 in toluene. Absorption spectrophotometric studies establish appreciable amount of ground state electronic interaction between fullerenes and 1. The interaction is facilitated through charge transfer (CT) transition as evidenced from well defined CT absorption bands in the visible region of the electronic spectra. In our present case, the CT interaction may be claimed as one of the rare findings, especially on account of interaction between fullerenes and bisporphyrin in a non-polar solvent. Other than fullerenes C60 and C70, various other electron acceptors, viz., 2,3-dichloro-5,6-dicyano-p-benzoquinone, tetracyanoethylene, o-chloranil and p-chloranil form CT complexes with 1. Utilizing the CT transition energies for various electron donor–acceptor complexes of 1, vertical ionization potential (IDv) of 1 is determined to be 6.37eV in solution. Estimation of degrees of CT, oscillator and transition dipole strengths evoke that the fullerene–1 non-covalent complexes are of neutral character in ground state. Higher magnitude of electronic coupling elements for the C70–1 complex compared to C60–1 complex indicates strong binding between C70 and 1. Steady state fluorescence studies elicit efficient quenching of the fluorescence of 1 in presence of fullerenes. Both UV–Vis and steady state fluorescence measurements reveal large value of binding constant (K) for C70–1 system (∼6.94×104dm3mol−1) than that of C60–1 system (K∼2.1×104dm3mol−1). Time resolved emission studies establish charge-separated state for the fullerene–1 systems. Transient absorption measurements in the visible region establish the formation of 1+ and fullerene− in toluene medium. Molecular mechanics calculations employing force field method in vacuo evoke the single projection structures of the fullerene–1 complexes and interpret the stability difference between C60 and C70 complexes of 1 in terms of heat of formation values of the respective complexes.

Spectroscopic and theoretical insights on fullerene–octaethylporphyrin self assembled non-covalent conjugates studied in solution

The present paper highlights the UV–Vis and fluorescence spectroscopic studies on spontaneous non-covalent interaction between a designed monoporphyrin, namely, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin (1) and fullerenes (C60 and C70) in toluene medium. While UV–Vis studies reveal considerable amount of fullerene/1 interaction in ground state, steady state fluorescence study establishes remarkable quenching of fluorescence intensity of 1 in the presence of fullerenes C60 and C70. Stoichiometry of both the fullerene complexes of 1 is determined to be 1:1. The magnitude of average binding constant (K) values for C70/1 and C60/1 systems is estimated to be 8705 and 3440dm3mol−1, respectively, which also prove that moderate value of selectivity in binding between C70 and C60 complexes of 1 is resulted in our present work. The genetics of the photo-physical characteristics of fullerene/1 complexes get tremendous support from lifetime experiment, which signifies the importance of static quenching phenomenon for our presently investigated supramolecules. Life time experiment yields larger magnitude of charge separated rate constant for the fullerene/1 species in toluene. Theoretical calculations at molecular mechanics level evoke the single projection geometric structures for the C60/1 and C70/1 systems in vacuo which also proves that interaction between C70 and 1 is governed by the dispersive forces associated with π–π interaction rather than electrostatic mechanism associated with charge transfer mechanism.

Spectroscopic and theoretical insights on determination of binding strength and molecular structure for the supramolecular complexes of a designed bisporphyrin with C60 and C70

The present article examines the binding affinity of the newly designed Zn2-bisporphyrin molecule, syn-1, towards C60 and C70 in toluene medium. The investigation is carried out by UV-vis spectrophotometric, steady state and time-resolved fluorescence spectroscopic techniques. The bisporphyrin, syn-1, serves as an effective and selective molecular tweezer for C70 as average value of binding constants (K) for the non-covalent complexes of syn-1 with C60 and C70 are estimated to be 1.65 × 104 and 1.05 × 105 dm3 · mol-1, respectively. Binding of C70 in the cleft of syn-1 is clearly demonstrated by the quantum chemical calculations at ab initio level of theory. Molecular electrostatic potential maps demonstrate significant redistribution of charges in these supramolecules. Proton NMR studies suggest that the C70 moiety remains at the shallow part of the cleft of syn-1.

Microstructure and Mechanical Property of Fe-Al<sub>2</sub>O<sub>3</sub> Nanocomposites Synthesized by Reactive Milling Followed by Spark Plasma Sintering

The in-situ Fe based nanocomposite containing Al2O3 particle is synthesized by reactive milling of Fe2O3-Al-Fe powder mixture in toluene medium followed by consolidation of powders using Spark Plasma Sintering process. Transmission electron microscopy investigation of consolidated Fe-Al2O3 nanocomposites has shown heterogenous grain structure of Fe consisting of nano, submicron and micron size grains together with nanometer Al2O3 particles. The hardness of Fe-Al2O3 nanocomposites consolidated at 800°C is 795 MPa.

Scope of network polysilanes in the synthesis of fluorescent silver and gold nanoparticles/nanoclusters-modulations of their optical properties in the presence of Hg(II) ions

The network polysilanes (polysilynes) [RMe2SiCH2CH2Si]n, [R=Ph (1), 2-Furyl (2)] have been synthesized by room temperature reaction of the corresponding organotrichlorosilane with Na dispersion in tetrahydrofuran (THF) medium. The method allows the formation of high molecular weight polymers [Mw/PDI = 10,504/2.2 (1), 9176/1.5 (2)] in improved yields than those obtained from classical Wurtz coupling reaction (Na, toluene, 110 °C). These polymers act as reducing agents for Ag(I) and Au(III) ions to afford stable metal nanoparticles of 4–8 nm size domains in toluene medium. The corresponding polymer–silver nanocomposites, 1a and 2a, are fluorescent in the green light region (λmax = ∼ 530 nm) due to the formation of silver nanoclusters (AgNCs) along with the nanoparticles (AgNPs). A simple chemical approach has been developed to modulate the plasmonic and emission intensities of the nanocomposite 1a by reacting with varying concentrations (10−12 to 10−7M) of HgI2 in toluene. The method allows enhancement of the fluorescence intensity associated with AgNCs. The results are explained by invoking coupling between the energies of surface plasmon resonance and the nanocluster electronic transition. The polymer–gold nanocomposites, 1b and 2b, are non-fluorescent and the plasmonic resonance at 530 nm associated with AuNPs is found to be insensitive to Hg(II) ions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Gas Chromatography–Mass Spectrometry Assessment of Amines in Port Wine and Grape Juice after Fast Chloroformate Extraction/Derivatization

A simple, reliable, and sensitive gas chromatography-mass spectrometry method for the quantification of volatile and nonvolatile biogenic amines in Port wines and grape juices was developed and evaluated. The method was based on a previously reported two-phase derivatization procedure with isobutyl chloroformate in a toluene medium, which provides a quantitative reaction in 10 min. Following the derivatization step, the excess of reagent was eliminated by treatment with alkaline methanol. The derivatization procedure was performed directly on 1 mL of sample, avoiding any fastidious and time-consuming cleanup extraction steps. The method allows the simultaneous quantification of 22 amines, which can be found in wines: methylamine, dimethylamine, ethylamine, diethylamine, propylamine, isopropylamine, butylamine, isobutylamine, amylamine, isoamylamine, 2-methylbutylamine, hexylamine, pyrrolidine, piperidine, morpholine, 1,3-diaminopropane, putrescine, cadaverine, 1,6-diaminohexane, 2-phenylethylamine, histamine, and tyramine. Because of the fact that histamine and tyramine derivatives are degraded during the isobutyl chloroformate elimination step, the corresponding determination was made after removal of the excess of derivatizing reagent by evaporating an aliquot of the toluene layer obtained after the reaction. The presented method showed excellent analytical characteristics in what linearity, recovery, repeatability, and limit of detections were respected. It was used to assess the concentration of biogenic amines in juice grapes and Tawny and Vintage Port wines with different aging times. On the whole, the total content of amines in Port wines was low. Most of the amines found in wines have their origin in the raw material used for their elaboration, so the Port winemaking process is not prone to the production of this kind of compounds. Total biogenic amine contents have shown a decrease with the aging of both types of Port wines.

Synthesis, photophysical investigations and molecular structure of the supramolecular complexes of a newly designed diporphyrin receptor with fullerenes C 60 and C 70 in solution

The present paper reports the synthesis of a designed diporphyrin ( 1), and its supramolecular complexes with C 60 and C 70 in toluene medium. While UV–Vis studies reveal ground state interaction between fullerenes and 1, steady state fluorescence measurements establish quenching of fluorescence of 1 by fullerenes. Binding constants data evoke that 1 may not be employed as an efficient molecular receptor for C 70 in said solvent. Time resolved emission studies establish relatively long-lived charge separated state for the C 70/ 1 complex in non-polar solvent. Transient absorption measurements reveal that electron transfer takes place from the diporphyrin 1 to the fullerenes in solution. Cyclic voltammetric studies enable us to calculate various important physicochemical parameters like free energy of charge separation, free energy of charge recombination (Δ G CR) and free energy of radical ion-pair formation for the fullerene/ 1 complexes. The positive Δ G CR values for both the C 60/ 1 and C 70/ 1 complexes suggest that the charge-recombination process is very much susceptible in fullerene/ 1 complexation process and they do not correspond to the inverted region of Marcus parabola. Molecular mechanics force field calculations in vacuo establish the single projection structures of the fullerene/ 1 complexes and interpret the stability difference between C 60- and C 70 complexes of 1. 1HNMR analysis provides very good support in favor of strong binding between C 70 and 1 in comparison to C 60- 1 system.

Multiobjective adaptive feedback control of two-photon absorption coupled with propagation through a dispersive medium

This work uses shaped femtosecond laser pulses to control the two-photon absorption (TPA) of coumarin 153 in a dispersive toluene medium. The dispersive medium reshapes the pulse along the optical path, and management of this effect is used to achieve spatial localization of TPA. Other control objectives were successfully implemented, including dual localization and high resolution local optimization of TPA. The solutions to these objectives were explored by means of evolutionary single- and multi-objective algorithms within a laboratory feedback loop.

Determination of binding strength for the supramolecular complexation of a designed bisporphyrin with C 60, C 70 and their derivatives employing absorption spectrophotometric, fluorescence and quantum chemical calculations

The present paper reports the synthesis of a designed bisporphyrin ( 1), and its supramolecular complexes with C 60, C 70 and their derivatives, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate ( 2) and [6,6]-phenyl C 70 butyric acid methyl ester ( 3) in toluene medium. C 60, C 70 and their derivatives undergo ground state non-covalent interaction with 1 is evidenced from absorption spectrophotometric study in which it is observed that the intensity of the Soret absorption band of 1 decreases considerably in presence of C 60, C 70 and their derivatives. Steady state fluorescence studies reveal efficient quenching of fluorescence of 1 in presence of fullerenes. The binding constant ( K) values of the fullerene/ 1 complexes follows the trend: 2/ 1 < C 60/ 1 < 3/ 1 < C 70/ 1. However, selectivity in K values of the bisporphyrin complexes is found to be higher for fullerene derivatives in comparison to C 60 and C 70. Time resolved emission studies establish relatively long-lived charge separated state for the C 70/ 1 complex. Molecular mechanics calculations at force field model in vacuo evoke the single projection geometric structures of various fullerene/ 1 complexes and interpret their stability differences in terms of heat of formation values.

Photophysical and theoretical insights on non-covalently linked fullerene–zinc phthalocyanine complexes

The photo-physical aspects of non-covalently linked assemblies of a series of fullerenes, namely, C 60, C 70, tert-butyl-(1,2-methanofullerene)-61-carboxylate ( 1) and [6,6]-phenyl C 70 butyric acid methyl ester ( 2) with a designed zinc phthalocyanine (ZnPc), viz., zinc-1,4,8,11,15,18,22,25-octabutoxy-29 H,31 H-phthalocyanine ( 3) in toluene medium are studied employing absorption spectrophotometric, steady state and time resolved fluorescence spectroscopic measurements. Of central interest in these investigations is the preferential binding of various fullerenes with ZnPc in toluene. The ground state interaction between fullerenes and 3 is first evidenced from UV–Vis measurements. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 3 in presence of both underivatized and derivatized fullerenes. K values for the complexes of C 60, C 70, 1 and 2 with 3 are determined to be 6500, 22,230, 47,800 and 54,770 dm 3 mol −1, respectively. The magnitude of K suggests that 3 preferentially binds C 70 and derivatized C 70 in comparison to C 60 and 1. Time resolved emission measurements establish that C 70- 3 and 2– 3 complexes are stabilized much more in comparison to C 60- 3 and 1– 3 systems in terms of charge separation process. Semi empirical calculations employing third parametric method substantiate the strong binding of C 70 and its derivative with 3 in terms of heat of formation values of the respective complexes, and at the same time, determine the orientation of bound guest (here fullerenes) with the molecular plane of 3.

Magnetic nanofilms of nickel prepared at the liquid–liquid interface

Thin films of metallic nickel with a thickness of the order of 20 nm have been prepared at the organic–aqueous interface at room temperature by the reaction of nickel cupferronate [Ni(C 6H 5N 2O 2) 2] in toluene medium and sodium borohydride (NaBH 4) in aqueous medium. The films were characterized with transmission electron microscopy, scanning electron microscopy and atomic force microscopy. Thicker Ni films could be prepared by carrying out the reaction at the interface at 60 °C. The Ni nanofilms exhibit superparamagnetic behavior.

Semiconductor-doped liquid-core optical fiber

A semiconductor liquid-core optical fiber has been made by simply filling the hollow core of a capillary waveguide with nanoparticles suspended in toluene media. Under a low continuous optical power excitation at 532 nm, the emission of PbSe particles was clearly demonstrated in the infrared region and then partially maintained in the core of the fiber by the total internal reflection mechanism. Finally, due to the guided propagation, which results in multiple absorption effects, a linear shift of the emission peak toward longer wavelengths was observed (~0.32 nm/cm). As a proof of concept, this original demonstration of visible-to-infrared conversion could lead to the development of active fibered devices at wavelengths not covered by the conventional rare-earth ion doping.