Tetrabutylammonium Ion Research Articles

Dual-Site Binding of Quaternary Ammonium Ions as Internal K+-Ion Channel Blockers: Nonclassical (C-H···O) H Bonding vs Dispersive (C-H···H-C) Interaction.

A molecular-level study of the influence of the alkyl chain length of quaternary ammonium ions (QAs) on the blocking action and the mode of binding with the bacterial KcsA K+-ion channel is carried out by molecular dynamics (MD) simulations as well as quantum mechanics/molecular mechanics (QM/MM) methods. The present work unveils distinct modes of binding for different QAs, due to differences in size and hydrophobicity. The QAs bind near the channel gate as well as at the central cavity, leading to a possible dual-site blocking action. Small-sized tetraethylammonium (TEA) and tetrabutylammonium (TBA) ions enter inside the channel cavity in the open state of KcsA but bind strongly in the closed state. TEA binds to the polar hydroxyl group of threonine residues situated at the channel gate via nonclassical H-bonding interaction (C-H···O), while TBA binds to a second binding site, the central cavity, with hydrophobic benzyl and sec-butyl side chains of phenylalanine and isoleucine residues via alkyl-π and hydrophobic interactions (C-H···H-C). On the contrary, large tetrahexylammonium (THA) and tetraoctylammonium (TOA) ions bind the hydrophobic side-chain methyl and isopropyl of alanine and valine at the channel gate both in the open and closed states, thereby restricting the free movement of large QAs toward the center of the cavity. However, the binding to the hydrophobic benzyl and sec-butyl side chains of phenylalanine and isoleucine residues in the closed state is thermodynamically preferable. Also, the binding energy is found to increase with an increase in the alkyl chain length from ethyl (-16.4 kcal/mol) to octyl (-65.5 kcal/mol), due to an almost linear increase in dispersive interaction.

Cation‐Specific Electrokinetic Separations Using Prussian Blue Intercalation Reactions

AbstractWe report a new approach for forming ion depletion zones (IDZs) using intercalation reactions at an electrochemically controlled Prussian blue (PB) film. The experiments described here were performed using a microfluidic device, wherein a charged fluorophore in solution was used as a proxy to monitor IDZ formation. In the presence of K+, intercalation reactions proceed readily to form an IDZ, and thus enrich the fluorophore up to 37‐fold. In the presence of the larger hydrated Li+ or tetrabutylammonium (TBA+) ions, however, ion intercalation proceeded less quickly than with K+. Slower ion intercalation resulted in a weaker IDZ and correspondingly lower enrichment factors of eight‐ and six‐fold, respectively. These results are significant because they show that PB intercalation reactions selectively form an IDZ. Accordingly, we anticipate that these findings will lead to a better understanding and further interesting applications of intercalation materials like PB for efficient and selective enrichment and separations.

Dual-functional alginate crosslinker: Independent control of crosslinking density and cell adhesive properties of hydrogels via separate conjugation pathways

Alginate is an abundant natural polysaccharide widely utilized in various biomedical applications. Alginate also possesses numerous hydroxyl and carboxylate functional groups that allow chemical modifications to introduce different functionalities. However, it is difficult to apply various chemical reactions to alginate due to limited solubility in organic solvents. Herein, functional moieties for radical polymerization and cell adhesion were separately conjugated to hydroxyl and carboxylate groups of alginate, respectively, in order to independently control the crosslinking density and cell adhesive properties of hydrogels. Sodium counterions of alginate are first substituted with tetrabutylammonium ions to facilitate the dissolution in an organic solvent, followed by in situ conjugations of (1) cell adhesion molecules (CAM) via carbodiimide-mediated amide formation and (2) methacrylate via ring-opening nucleophilic reaction. The resulting CAM-linked methacrylic alginate was able to not only crosslink different monomers to form hydrogels with varying mechanical properties, but also induce stable cell adhesion to the hydrogels.

Analytical methods for the determination of acifluorfen and bentazone residues in crops

Methods using high performance liquid chromatography (HPLC) were developed to determine acifluorfen and bentazone in crops. Twenty samples of dry bean crops and rice were purchased from traditional markets and analyzed. Acifluorfen and bentazone being weak acids, were selectively extracted as ion pair compounds formed with tetrabutylammonium ion into dichloromethane under basic conditions. This technique was used for cleanup prior to determination of acifluorfen and bentazone by reverse phase liquid chromatography with UV detector. A residue of aciflourfen was extracted from crops with acetonitrile and acetonitrile-H2O (9:1, v/v) and a residue of bentazone was extracted from crops with acetone. The extracts were evaporated to dryness, dissolved in pH 8.0 phosphate buffer, and washed with n-hexane and dichloromethane. Ion pair compounds were formed by adding tetrabutylammonium ion into an aqueous phase, and then extracted into dichloromethane. The dichloromethane phase was evaporated and the residues were dissolved in organic solvent and determined by HPLC. Recovery studies were carried out by spiking the standards of acifluorfen and bentazone at the levels of 0.05-0.15 and 0.25-0.75 ppm, respectively. The average recoveries were determined to be 91.6-97.6% and 88.6-91.7%, respectively. The detection limits in crops were 0.02 and 0.05 ppm for acifluorfen and bentazone, respectively. No residues of acifluorfen or bentazone were detected in dry bean crop samples, nor was bentazone residue found in rice samples.

Capillary Electrophoretic Characterization of Water-soluble Carbon Nanodots Formed from Glutamic Acid and Boric Acid under Microwave Irradiation.

Water-soluble carbon nanodots (CND) were synthesized under microwave irradiation from glutamic acid or glutamic acid-boric acid mixture. The CNDs were collected in an aqueous solution through size fractionation by centrifugal filtration. The CNDs thus prepared were subjected to characterization by capillary electrophoresis (CE). A peak signal of anionic substance was detected in the electropherogram, and it was found to be a major component of the CNDs. The effective electrophoretic mobility of the major component was almost identical over the pH range between 6.7 and 11.6, suggesting that the functional group of amine or boric acid moiety was not included in the CNDs. The effective electrophoretic mobility decreased at an acidic pH of less than 5, and it was suggested that carboxylate moiety was included in the CNDs. A signal of less-charged CNDs was also detected in the electropherogram, and the CNDs were characterized by a CE format of micellar electrokinetic chromatography. Two or four peaks were detected just after the electroosmotic flow; the less-charged CNDs were thus hydrophilic. The affinity interaction was also examined between the major anionic CNDs and a hydrophobic pairing cation. The peak signal of the major anionic CNDs broadened, and its theoretical number of plates decreased in the presence of tetrabutylammonium ion in the separation buffer. A small portion of the anionic CNDs were a little hydrophobic at different degrees, and their effective electrophoretic mobility decreased by the hydrophobic interaction, resulting in peak broadening of the anionic CNDs.

Voltammetry and Spectroelectrochemistry of TCNQ in Acetonitrile/RTIL Mixtures.

Understanding the solvation and ion-pairing interactions of anionic substrates in room-temperature ionic liquids (RTIL) is key for the electrochemical applications of these new classes of solvents. In this work, cyclic voltammetry and visible and infrared spectroelectrochemistry of tetracyanoquinodimethane (TCNQ) was examined in molecular (acetonitrile) and RTIL solvents, as well as mixtures of these solvents. The overall results were consistent with the formation of RTIL/acetonitrile nanodomains. The voltammetry indicated that the first electrogenerated product, TCNQ−, was not incorporated into the RTIL nanodomain, while the second electrogenerated product, TCNQ2−, was strongly attracted to the RTIL nanodomain. The visible spectroelectrochemistry was also consistent with these observations. Infrared spectroelectrochemistry showed no discrete ion pairing between the cation and TCNQ− in either the acetonitrile or RTIL solutions. Discrete ion pairing was, however, observed in the acetonitrile domain between the tetrabutylammonium ion and TCNQ2−. On the other hand, no discrete ion pairing was observed in BMImPF6 or BMImBF4 solutions with TCNQ2−. In BMImNTf2, however, discrete ion pairs were formed with BMIm+ and TCNQ2−. Density function theory (DFT) calculations showed that the cations paired above and below the aromatic ring. The results of this work support the understanding of the redox chemistry in RTIL solutions.

Desensitization of NMDA channels requires ligand binding to both GluN1 and GluN2 subunits to constrict the pore beside the activation gate.

N-methyl-D-aspartate (NMDA) receptor channels are activated by glutamate (or NMDA) and glycine. The channels also undergo desensitization, which denotes decreased channel availability, after prolonged exposure to the activating ligands. Glycine apparently has a paradoxical negative effect on desensitization, as the increase in ambient glycine in concentrations required for channel activation would increase sustained NMDA receptor currents. We hypothesized that this classical"glycine-dependent desensitization" could be glycine-dependentactivation in essence. By performing electrophysiological recordings and biophysical analyses with rat brain NMDA receptors heterogeneously expressed in Xenopus laevis oocytes, we characterizedthat the channel opened by "only" NMDA (in nominally glycine-free condition probably with the inevitable nanomolar glycine) would undergo a novel form of deactivation rather than desensitization, and is thus fully available for subsequent activation. Moreover, external tetrapentylammonium ions (TPentA), tetrabutylammonium ions, and tetrapropylammonium ions (TPA, in higher concentrations) block the pore and prohibit channel desensitization with a simple "foot-in-the-door" hindrance effect. TpentA and TPA have the same voltage dependence but show different flow dependence in binding affinity, revealing a common binding site at an electrical distance of ~0.7 from the outside yet differential involvement of the flux-coupling region in the external pore mouth. The smaller tetraethylammonium ion and the larger tetrahexylammonium and tetraheptylammonium ions may block the channel but could not affect desensitization. We conclude that NMDA receptor desensitization requires concomitant binding of both glycine and glutamate, and thus movement of both GluN1 and GluN2 subunits. Desensitization gateitself embodies a highly restricted pore reduction with a physical distance of ~4Å from the charged nitrogen atom of bound tetraalkylammonium ions, and is located very close to the activation gate in the bundle-crossing region in the externalpore vestibule.

Function of Tetrabutylammonium on High-Efficiency Ruthenium Sensitizers for Both Outdoor and Indoor DSC Application.

The function of tetrabutyl ammonium ions (TBA+) in a sensitizer used in dye-sensitized solar cells (DSC) is contradictory. TBA+ can reduce unwanted charge-recombination by protecting the TiO2 surface and reduce dye aggregation, enhancing the photovoltaic performance. It will also compete with the dye-loading on the TiO2 film, decreasing the short-circuit current density of the cell. Three ruthenium sensitizers (DYE III, DUY11, and DUY12 containing two H+, one H+/one TBA+, and two TBA+, respectively) were prepared to systematically investigate the function of TBA+ in a dye for DSC under both standard sunlight and indoor illumination. The optical properties and frontier orbital energy level of the sensitizers are not influenced significantly by the number of TBA+. Under the standard 1 sun illumination, DSCs based on DUY11 (containing one H+ and one TBA+) achieved the highest power conversion efficiency (PCE) of 11.47%. Overall, optimized DSCs sensitized by the three ruthenium dyes all have the PCE over 10%, which is higher than that (9.95%) of N719-dyed cell fabricated at the same conditions. Under the illumination of a light emitting diode (LED), DSCs sensitized by DUY11 also have the highest efficiency of 19%. Furthermore, DUY12 with two TBA+ exhibits superior photovoltaic performance compared to a DYE III (containing two H+ in the anchoring ligands)-dyed cell; although these two dyes have similar photovoltaic performance under standard 1 sun lighting. The important function of TBA+ in reducing the charge recombination (by protecting TiO2 surface and avoiding dye aggregation) of a DSC under indoor lighting (when small number of electrons were excited by weak light) is also revealed.

Electrodeposition of Indium on Glassy Carbon from Tetrabutylammonium Chloride Containing Solutions

The effectiveness of tetrabutylammonium chloride (TBACh) as inhibition additive of dendritic growth of indium has been investigated by means of cyclic voltammetry and chronoamperometry methods. The rotating disk electrode (RDE) method allowed the calculation of the diffusion coefficient of In3+ ions using the Levich equation, at 25 °C is 4.41 × 10–6 cm2/s. Diffusion coefficient of indium ions determined by chronoamperometry using the Cottrell law (6.63 × 10–6 cm2/s) is in consistent with the value calculated by the Levich equation. The addition of tetrabutylammonium ions to the electrolyte reduces the diffusion coefficient and inhibits the cathodic process by increasing the activation energy from 10.5 kJ/mol to 20.7 kJ/mol. The indium nucleation and growth on glassy carbon in chloride solutions was studied by single potentiostatic pulse techniques. The nucleation mechanism was evaluated by analyzing the influence of different TBACh ion concentration and applied potentials. The electrocrystallization mechanisms were determined by fitting the experimental non-dimensional current transients on the basis nucleation and growth model developed by Scharifker-Hills. The type of nucleation corresponding to the progressive three-dimensional nucleation with diffusion control is determined. Based on theoretical models of 3D multiple nucleation from the potentiostatic current transients were calculated nucleation characteristics, such as the stationary nucleation rate, saturation nucleus density and the average grains radius of indium deposits. The leveling action of TBACh on the electrodeposition of indium at concentration of 10-4 M was found.

Surface Modification of Layered Perovskite Nanosheets with a Phosphorus Coupling Reagent in a Biphasic System.

Oleyl phosphate-modified HLaNb2O7· xH2O nanosheets (OP_HLaNb nanosheets) were prepared via phase transfer from an aqueous phase, comprising a dispersion of HLaNb2O7· xH2O (HLaNb) nanosheets, formed through the intercalation of tetrabutylammonium ion (TBA+) in the interlayer space of HLaNb and subsequent delamination, to a cyclohexane phase containing oleyl phosphate (OP, a mixture of monoester and diester). The modification of HLaNb nanosheets with OP was essentially completed within 3 days at a pH value of 2 or 4. Both infrared and solid-state 13C cross-polarization and magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of the OP_HLaNb nanosheets showed the presence of OP and/or related species and TBA+ on the HLaNb nanosheet surface. The solid-state 31P MAS NMR spectra of OP_HLaNb nanosheets exhibited new signals at -2 and 0 ppm, the former of which indicates the formation of Nb-O-P bonds. These whole data set obtained by complementary techniques clearly point out the modification of the HLaNb nanosheet surface by OP moieties causing a phase transfer. OP_HLaNb nanosheets showed higher dispersibility in cyclohexane than the OP_HLaNb_interlayer nanosheets, which were prepared via stepwise substitution reactions in the interlayers of HLaNb to achieve surface modification with OP and subsequent exfoliation in cyclohexane. The presence of TBA+ on the HLaNb nanosheets and the use of a liquid-liquid biphasic system were likely to improve the dispersibility. These results show that the preparation of OP-modified HLaNb nanosheets which could be well-dispersed in the cyclohexane phase was successful because of the use of a liquid-liquid biphasic system.

Kinetics of Antimicrobial Drug Ion Transfer at a Water/Oil Interface Studied by Nanopipet Voltammetry.

Effective delivery and accumulation of antimicrobial agents into the microbial organism is essential for the treatment of bacterial infections. Transports of hydrophilic drug molecules, however, encounter a robust barrier of hydrophobic double membrane cell envelope, thus, leading to drug-resistance in Gram-negative bacteria. Accordingly, a deeper understanding about a transit of charged molecules through a bacterial membrane is needed to remediate the antibacterial resistance. Herein, we apply a steady-state voltammetry using nanopipet-supported interfaces between two immiscible electrolyte solutions (ITIES) to quantitatively study transport-kinetics of antimicrobial drug ions (quinolones and sulfonamides) at a water/oil interface. Importantly, ITIES can mimic a cellular membrane system, thus, being employed as insightful surrogates for the kinetic study of drug entry through bacterial cytoplasmic membranes. This approach enables us to voltammetrically and amperometrically detect redox-inactive drug ions as pristine under physiological conditions. Considerably slow kinetics of drug-ion transports are successfully measured by nanopipet voltammetry and theoretically analyzed. This analysis reveals that the drug-ion transport is ∼3 orders of magnitude slower than tetrabutylammonium ion transport. In addition, the extreme hydrophilicity of drug ions in comparison to ClO4- is quantitatively assessed from half-wave potentials of obtained voltammograms. The high hydrophilicity exclusively attributed to localized negative charges on carboxylate or amide group of deprotonated quinolone or sulfonamide, respectively, may play a dominant role in sluggish kinetics due to the increase in energy barriers upon interfacial ion transfer. Notably, this study using nanopipet voltammetry provides physicochemical insights on the correlation between structural properties of pristine drug ions and their transfer kinetics at a water/oil interface in lieu of biological membranes.

Electrical conductivity, ion-molecular and interionic interactions in solutions of some tetraalkylammonium salts in acetonitrile: the influence of the ion and temperature

Conductance data for Et4NBr, Et4NBF4, Bu4NBr, Bu4NBF4 in acetonitrile for the molar concentration range of 2·10-4–1·10-2 mol·dm-3 over the temperature range from 5 to 55 °C are reported. Limiting molar conductivities and ion association constants were determined by using the Lee-Wheaton equation for the symmetrical electrolytes. On the basis of the preliminary conductometric data analysis it was established that the closest approach parameter is almost independent from the temperature for all studied acetonitrile solutions. Therefore, the closest approach parameter was adopted as a sum of cation and anion radii for further conductometric data treatment. The limiting conductivities of Br-, BF4-, Et4N+ and Bu4N+ ions and the structure-dynamic parameter of ion-molecular interaction obtained from the experimental data on limiting molar conductivities were evaluated in the framework of the approach proposed by authors [Kalugin O. N., Vjunnik I. N. Limiting ion conductance and dynamic structure of the solvent in electrolyte solution. Zh. Khim. Fiz. (Rus.) 1991, 10 708-714]. Elongation of the alkyl radical of the tetraalkylammonium cation from Et4N+ to Bu4N+ leads to a significant increase in the structure-dynamic parameter, which indicates the dynamic structuring of the solvent near the tetrabutylammonium ion and increased solvophobic solvation of the Bu4N+ compared to Et4N+. Ion association constants are discussed in terms of competition between Coulomb and non-Coulomb forces in terms of short-range square-mound potential. An increase in the ion association constants in the sequence Bu4NBF4<Et4NBF4<Bu4NBr<Et4NBr was explained by the increase in the contribution of short-range ion-molecular interactions to the interionic attraction in addition to the electrostatic component. An increase in temperature enhances the ionic association due to both the electrostatic and short-range components.

Vanillin production from native softwood lignin in the presence of tetrabutylammonium ion

Vanillin is one of the industrially important compounds that can be produced from lignin. This study presents production of vanillin and vanillic acid (oxidized form of vanillin) through aerobic oxidation of Japanese cedar (Cryptomeria japonica) at 120 °C for 72 h in aqueous alkali solutions with several Bu4N+ and OH− concentrations (1.25, 2.50, and 3.75 mol/L), where Bu4N+ is an enhancer of the vanillin formation reported in our previous study. The concentrations of Bu4N+ and OH− were adjusted by the additions of Bu4NCl and solid NaOH into the base medium Bu4NOH·30H2O, which forms 1.25 mol/L aqueous solution of Bu4NOH at the elevated temperature. Vanillin and vanillic acid were produced with the maximum yields of 21.0 and 1.7 wt% (lignin-base), respectively, at the 1.25 mol/L Bu4N+ and 3.75 mol/L OH− concentrations. This vanillin yield is close to that obtained by the alkaline nitrobenzene oxidation (26.5 wt%), indicating significantly high selectivity of our lignin degradation with Bu4N+ toward vanillin formation. We also proposed a novel Bu4NOH·30H2O-free reaction medium, where Bu4NOH·30H2O as the base medium were substituted with an aqueous solution of Bu4NCl and NaOH to avoid using expensive Bu4NOH·30H2O. The treatment of the Japanese cedar with this alternative medium exhibited the moderately decreased vanillin yield of 14.6 wt%, which is, however, much higher than the vanillin yield obtained with a simple 1.25 mol/L NaOH solution.

Synthesis and X-ray absorption spectroscopic analysis of exfoliated perovskite oxynitride nanosheets obtained from LiLaTa2O6.15N0.57 precursor

Layered perovskite oxynitride LiLaTa2O6.15N0.57 with Dion-Jacobson phase was successfully exfoliated into colloidal suspension by using proton-exchange reaction and followed intercalation of ethylamine and tetrabutylammonium ion. According to the X-ray diffraction pattern, a basal spacing of the layered perovskite oxynitride concomitantly increased as the intercalation reaction with bulky cations proceeded. Transmission electron microscopy and atomic force microscopy analysis indicated that the exfoliated perovskite oxynitride was composed of single-layered and multi-stacked nanoplatelets. UV–vis diffuse reflectance showed that the self-reassembled perovskite oxynitride nanosheet also had characteristic absorption in a visible range, revealing that visible light harvesting property of the perovskite oxynitride maintained even after exfoliation and subsequent reassembling reaction. Extended X-ray absorption fine structure (EXAFS) analysis of samples clearly showed that structural disorder upon intercalation reaction resulted in damping of EXAFS oscillation, suggesting nanosized feature of the exfoliated nanosheet.

Controlling Selectivity in the Electrochemical Reduction of Acrylonitrile: Towards a Solar-Driven Nylon 6,6 Production Process

Fossil fuel derived carbon dioxide (CO2) emissions have continuously increased over the past century and their impact in climate change is self-evident. The chemical industry is a large contributor to this increase, accounting for more than 5.5% of the global CO2 emissions. Implementing electrochemical routes for the production of large volume chemicals can allow for the direct integration of renewable energy sources into chemical manufacturing. In this way, solar- or wind-powered electrochemical processes could greatly contribute to the reduction of the carbon footprint of the chemical industry. Although inorganic electrosynthetic processes have been successfully implemented in industry at scale (i.e. chloro-alkali and Aluminum production), the implementation of electrochemical methods for the production of organic chemicals has been limited. Adiponitrile (ADN) is the largest-volume organic chemical product currently produced electrochemically (>1.5 million tons/year). ADN is a precursor used in Nylon 6,6 manufacturing and it can be obtained via the electrohydrodimerization of acrylonitrile (AN). Although the electrosynthesis of ADN is considered the most successful organic electrochemical process in industry, it still faces many challenges owing to its energy conversion efficiency and selectivity. Optimizing the composition of the electrolyte can result in significant performance improvements. The implementation of tetraalkylammonium (TAA) ions has been shown to increase the reaction selectivity towards adiponitrile, but there is limited understanding on their role in the mass transport and kinetic aspects of the transformation. In this study, we provide experimental insights into the effects of TAA ions in the selectivity and efficiency of the AN electrohydrodimerization reaction. TAA ions can limit the hydrogen evolution reaction by sterically hindering water molecules from approaching the electrode surface and locally increasing the concentration of organic reactants. These effects are believed to be responsible for the increase in selectivity towards the reduction of AN. In our study, we explored electrolytes containing TAA ions with varying lengths of the alkyl substituents (i.e., methyl, ethyl, butyl and hexyl) and assessed the effects of their molecular size, affinity towards AN, and concentration on the electrolyte conductivity and selectivity. Using a combination of cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry at a cadmium electrode, we showed that optimal performance is achieved for electrolytes containing tetrabutylammonium (TBA) ions. A maximum selectivity towards ADN of 80% was demonstrated for TBA concentrations ranging between 0.04 to 0.5 mM. Furthermore, we studied the effects of TAA ions on the ohmic and mass transport limitations under varying current densities. Our results suggest that (i) the local concentration of AN in the electrical double layer strongly depends on the nature of the TAA and the applied current density and (ii) that this concentration is important in determining the predominant reaction pathways and thus the product distribution between ADN and other electrochemical side products (e.g., propionitrile and 1,3,6 tricyanohexane). The results obtained in this study can be used to derive electrolyte design guidelines which will improve the efficiency of the electrochemical adiponitrile production process. Furthermore, understanding the effects of current density in the selectivity of the reaction allows for the design of operating protocols to directly drive electrochemical transformations with intermittent sources of energy such as solar power. These design guidelines can lead to highly efficient solar-ADN reactors and enable the clean manufacture of precursors for the polymer industry. The performance of proof-of-concept prototypes solar-AND devices will be discussed. Figure 1

An Optical Chemodosimeter Coumarin Nosylate for Probing Fluoride Ion: Synthesis, Crystal Structures, Photophysical and Theoretical Studies

AbstractTo achieve selectivity for fluoride recently researchers resorted on its nucleophilic characteristics rather than its basicity. The design strategy of this kind of probe involves masking of a fluorescent moiety with NBS/DNBS masking groups. Attack of fluoride over the same leads to release of fluorescent moiety in the solution. The prime concern of this family of probes is that no crystallographic evidence is available till date in the literature to the best of our knowledge. We are reporting herein a new chemodosimeter in the form of a coumarin nosylate (CMS) as a dual channel optical probe for the smart detection of fluoride. Interestingly, we not only isolated single crystals of CMS but also successfully isolated the fluoride (F−) induced cleaved product of CMS i. e. chromenolate counter balanced with tetrabutylammonium (TBA) ion.

The Effect of Cation Size on DNA Thermal Stability

Capillary electrophoresis has been used to examine the effect of cation size on DNA thermal stability, using hairpins with 6 base pair-stems and 4 nucleotide-loops as the reporter system. The midpoint melting temperatures observed in solutions containing the tetrabutylammonium ion (TBA+) are consistently 16°C lower than observed in solutions containing the same concentration of Na+, even though no preferential interaction with either cation is observed. The thermal melting temperatures decrease progressively with increasing cation size, due primarily to the effect of cation size on solution viscosity. We postulate that the viscosity of the solution affects the hairpin ↔ coil equilibrium because of through-solvent effects on hairpin renaturation, as observed in other studies. The mobilities of the various hairpins are independent of sequence in Na+ but depend on sequence in TBA+ solutions. In particular, the observed mobilities increase with the increasing number of thymine bases in the loop, possibly because of the partial ionization of thymine in TBA+ which would increase the effective net charge of the hairpin.

An economical process to recover sulfuric acid and tetrabutylammonium ions from acidic saline wastewater with organics

An economical process to recover sulfuric acid and tetrabutylammonium ions from acidic saline wastewater with organics

Synthesis of a hierarchical ZSM-11/5 composite zeolite of high SiO2/Al2O3 ratio and catalytic performance in the methanol-to-olefins reaction

A hierarchical ZSM-11/5 composite zeolite with a high SiO 2 /Al 2 O 3 ratio was successfully synthesized using a seed-induced method in the presence of cetyltrimethylammonium bromide, characterized by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, 27 Al NMR, 27 Si NMR, N 2 physical adsorption, and temperature-programmed desorption of ammonia, and studied in the frame of the methanol-to-olefins reaction. The results show that the amount of seed added plays a pivotal role in the formation of hierarchical ZSM-11/5 composite zeolite. With an increase in the amount of seed, the composite zeolite exhibits excellent catalytic performance in the methanol-to-olefins reaction, which can be attributed to the higher specific surface areas, higher external surface areas, more mesopore volumes, and more acid sites than ZSM-11 synthesized by the conventional method with tetrabutylammonium ions as a template. Contrary to the conventional point of view, the addition of too much seeds results in a dramatic decrease in the catalytic performance, which is ascribed to the higher proportion of ZSM-5 in the ZSM-11/5 composite zeolite.

Oxidation of Aniline to Nitrobenzene Catalysed by 1-Butyl-3-methyl imidazolium phosphotungstate Hybrid Material Using m-chloroperbenzoic Acid as an Oxidant

Keggin ion based hybrid materials, [BmIm]3[PW12O40], [TBA]3PW12O40 and [BuPy]3PW12O40, were prepared by proton exchange with organic cations, 1-butyl-3-methyl imidazolium ion, tetrabutylammonium ion and butylpyridinium ion, respectively. The formation of hybrid materials was confirmed by FTIR, PXRD, SEM, TG-DTA, DSC analysis. These hybrid compounds are active for oxidation of aniline using m-chloroperbenzoic acid as an oxidant. Among the three hybrid compounds, 1-butyl-3-methyl imidazolium phosphotungstate was found to be the best and efficient catalyst for selective aniline oxidation to nitrobenzene. It is a recoverable and reusable catalytic system. The redox property of the phosphotungstate cluster in the hybrid material is involved in the catalytic activity.