Tetraalkylammonium Hydroxide Research Articles

Systematic Study on Swelling/Delamination of Layered Metal Oxides with Quaternary Ammonium Ions: Production of Well-Shaped/Oversized Unilamellar Nanosheets.

Enormous swelling of layered host compounds in an aqueous solution of various amines has been investigated as an important step in the synthesis of molecularly thin 2D nanosheets. However, a complete understanding of the reaction process has not been attained, which is the barrier for producing high-quality unilamellar nanosheets. Here, the swelling and delamination behaviors of platelet single crystals of protonated layered metal oxides are systematically examined with a series of tetraalkylammonium (TAA) hydroxide solutions. Upon contact with the solutions, the crystals immediately underwent massive expansion by several tens to hundreds of times. The swollen crystals can be delaminated into elementary layers by the application of external shear force. The exfoliation behavior is dependent on TAA ions, especially in terms of yield and lateral size/shape of the delaminated nanosheets. The swollen crystals with TAA ions with longer alkyl chains are delaminated almost completely, but irregular and fractured small sheets are yielded. Such long alkyl chains become entangled on the oxide layer and resulting hydrophobic interactions may be responsible for the lateral fragmentation. It is found that replacement of aqueous solutions with organic solvents to suppress the hydrophobic interactions is effective to produce oversized nanosheets in rectangular shape with sharp edges.

Dissolution dynamics of poly(4-hydroxystyrene-co-methacrylic acid) in tetraalkylammonium hydroxide aqueous solutions

Resist materials and their lithography processes are essential for achieving further miniaturization in semiconductor microfabrication. In the sub-20 nm half-pitch region, the development process becomes particularly important due to the occurrence of stochastic defects (pinching and bridging). However, the details of dissolution dynamics are still unclear. In this study, we investigated the dissolution dynamics of poly(4-hydroxystyrene-co-methacrylic acid) (PHSMA) films in tetraalkylammonium hydroxide (TAAH) aqueous solutions using a quartz crystal microbalance method. PHSMA is a typical backbone polymer used in extreme UV lithography. For poly(4-hydroxystyrene) films, it has been reported that the dissolution mode changed when the alkyl chain length of TAAH increased. However, the mode change was not observed for PHSMA films. This difference is considered to be caused by the formation of thick transient swelling layers of PHSMA films owing to the fast water intake and the molecular interaction of the hydroxyl groups of hydroxystyrene units.

Generation of mesoporosity in H–Y zeolites by basic or acid/basic treatments: Towards a guideline of optimal Si/Al ratio and basic reagent

We elaborate a post-modification method for faujasite zeolite to introduce additional mesopore volume, by desilication (if necessary combined with prior dealumination). CBV712 (Si/Al = 6), CBV720 (15), and CBV760 (28) were used as starting materials. We employ tetraalkylammonium hydroxide (TAAOH) as desilicating agent, varying its alkyl chain from C1 to C4. The different sizes of TAAOH show different modulating capacities in pore generation. Short alkyl chains generate a lot of mesopores, but also lead to extended amorphization. The opposite holds true for long alkyl chains. The desilication treatment was unsuccessful for CBV712, because of its too high Al content. CBV712, was therefore dealuminated by oxalic acid, to different extents, before applying TAAOH. This allowed us to identify the optimal Si/Al range for the desilication treatment, i.e. between 15 and 28. We also examined the accessibility of active sites in mesoporous zeolites by the sterically hindered base 2,4,6-tri-tert-butylpyridine (TTBPy).

Classification of dissolution modes of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

The development of high-numerical aperture exposure tools for EUV lithography is in progress. The development process (the dissolution of resist films) is the key to fine patterning. The dissolution dynamics of acidic polymers (the backbone polymers of chemically amplified resists) depend on various parameters related to molecular structures. In this study, the dissolution dynamics in tetraalkylammonium hydroxide (TAAH) aqueous solutions were classified into six classes on the basis of the frequency and impedance changes observed during the development process by a quartz crystal microbalance method. The relationship between class and physical parameters of materials was analyzed by decision tree and support vector machine methods. The feature values used were the alkyl chain length, molecular weight, and concentration of TAAH; the viscosity of the developer; and the protection ratio, molecular weight, contact angle, surface free energies of polymers, and film thickness. The classification accuracy was 0.80 for the validation data.

Electronic Structure of 1D Lepidocrocite TiO2 as Revealed by Optical Absorption and Photoelectron Spectroscopy

We recently demonstrated scalable, one-pot syntheses of one-dimensional, titania lepidocrocite microfilaments by reacting Ti-containing water-insoluble, earth-abundant compounds such as TiC, TiB2, TiN, etc., with tetraalkylammonium hydroxide, TMAOH, for a few days at 85 °C under ambient pressure. The resulting one-dimensional lepidocrocite (1DL) titania-based nanofilaments, NFs, tend to self-align along the [100] growth direction to form microfilaments that sometimes self-align into pseudo-two-dimensional (2D) sheets. With sub-square-nanometer cross sections, the resulting band gap energy, Eg, at 4.0 eV is one of the highest ever reported for a titania material. Despite a large band gap, the nanofilaments exhibit significant absorbance throughout the visible spectrum ascribable to intra-gap defect states based on UV–Vis absorbance data and ultraviolet photoelectron spectroscopy (UPS). UP spectra demonstrate work functions of 4.0 ± 0.3 eV vs vacuum and Fermi energies of 3.8 ± 0.1 eV with respect to the valence band edge. Transient absorption (TA) spectroscopy of the 1DL nanofilament thin films with sub-band-gap, visible-light illumination reveals photoexcitations with lifetimes in excess of nanoseconds. In combination with the established oxidative stability, long-lived visible photoexcitations bring forward possible applications of 1DL nanofilaments in photocatalysis and optoelectronics.

Photoresist stochastic defect generation depending on alkyl chain length and concentration of tetraalkylammonium hydroxide in alkali aqueous developer

The effects of photoresist dissolution on randomly occurring (“stochastic”) pattern defects in extreme ultraviolet (EUV) lithography were investigated. Specifically, the effects of the alkali concentration of two developers of different alkyl chain lengths; tetramethylammonium hydroxide and tetrabutylammonium hydroxide (TBAH) on stochastic defect generation were investigated for two typical EUV photoresists. In the case of the PHS-type photoresist, results show that stochastic defect generation was almost the same regardless of developer type, given the same developer concentration. For the hybrid-type photoresist, a decrease in stochastic defects was found with the application of the longer alkyl chain length TBAH developer. Results also suggest the existence of an optimum developer concentration. Such optimum developer concentration is considered to be affected by the balance between polarity and non-polarity of the photoresist and developer components.

Effects of photoacid generator decomposition on dissolution kinetics of poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

For the advancement of lithography, the resist materials and processes are the most critical factors. In particular, the process of developing resist materials is important in reducing the line width roughness and stochastic defects. In this study, a quartz crystal microbalance method was used to investigate the dissolution dynamics of poly(4-hydroxystyrene) (PHS) films containing triphenylsulfonium nonaflate (TPS-nf) in tetraalkylammonium hydroxide (TAAH) aqueous solutions. The time required for dissolution increased with the alkyl chain length of TAAH. The dissolution rate of PHS films increased with UV irradiation dose for tetramethylammonium hydroxide and tetraethylammonium hydroxide developers, whereas the dissolution time increased for the tetrabutylammonium hydroxide developer. For the tetrapropylammonium hydroxide developer, the dissolution time of PHS films without postexposure baking (PEB) slightly decreased with UV irradiation, whereas that with PEB increased. Both the surface free energy of PHS films and the molecular size of TAAH are considered to affect dissolution kinetics.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solution

A 0.26 M tetramethylammonium hydroxide (TMAH) aqueous solution has been used as a standard developer for manufacturing semiconductor devices. Alternative developers have recently attracted much attention because the 0.26 M TMAH developer may be approaching its performance limit. In this study, we measured the dissolution and swelling behavior of resist polymers in tetraalkylammonium hydroxide (TAAH) aqueous solutions using a quartz crystal microbalance method to clarify the effects of the alkyl chain length of TAAH. The resist polymer was poly(4-hydroxystyrene), whose hydroxyl groups were partially protected with t-butoxycarbonyl groups. When the alkyl chain length of TAAH was increased from two (ethyl) to three (propyl), the dissolution mode markedly changed. The dissolution mode did not depend on the polymer polarity. The change in the dissolution mode is probably caused by the size effect of TAAH, considering the independence of polymer polarity and the discrete change in the dissolution mode.

Stochastic defect generation depending on tetraalkylhydroxide aqueous developers in extreme ultraviolet lithography

Patterning targets in leading-edge technologies such as extreme ultraviolet lithography (EUVL) are starting to push present photoresist materials (e.g. chemical amplification resists) to their physical limits. The appearance of randomly occurring (stochastic) photoresist-based defects in these stringent patterning targets has become one of the main concerns in EUVL. To obtain possible clues to understanding these stochastic defects, the effect of developer solutions (alkyl chain length of tetraalkylammonium hydroxide) on stochastic defects was investigated. This paper was built on our previous work in which we investigated the dissolution dynamics of three types of typical EUV photoresist processed in developer solutions with different alkyl chain lengths. Using the same materials, we found from EUV patterning experiments focusing on contact hole (CH) patterns that the long-alkyl-chain developer solution, i.e. tetrabutylammonium hydroxide, was effective in mitigating stochastic defects in acryl-type and hybrid-type photoresists (the latter being more commonly utilized for EUVL). (147/150)

On Reuben G. Jones synthesis of 2-hydroxypyrazines.

In 1949, Reuben G. Jones disclosed an original synthesis of 2-hydroxypyrazines involving a double condensation between 1,2-dicarbonyls and α-aminoamides upon treatment with sodium hydroxide at low temperature. This discovery turned out to be of importance as even today there are no simple alternatives to this preparation. Across the years, it was employed to prepare 2-hydroxypyrazines but some of its limits, notably regioselectivity issues when starting from α-ketoaldehydes, certainly hampered a full-fledged generation of pyrazine-containing new chemical entities of potential interest in medicinal chemistry. The present text describes some insights and improvements, such as the unprecedented use of tetraalkylammonium hydroxide, in the reaction parameters affecting the regioselectivity and yield when starting from phenylglyoxal and two α-aminoamides. We also suggest a mechanism explaining the counterintuitive occurrence of 3,5-substituted-2-hydroxypyrazine as the major reaction product.

Well-Controlled Living Polymerization of Phenylacetylenes in Water: Synthesis of Water-Soluble Stereoregular Telechelic Poly(phenylacetylene)s.

Well-controlled living polymerization of water-soluble phenylacetylene derivatives in water was achieved for the first time using a multicomponent catalytic system consisting of [Rh(nbd)Cl]2 , an aryl boronic acid, diphenylacetylene having carboxy groups, a tetraalkylammonium hydroxide, and a water-soluble triphenylphosphine. This catalytic system enables a direct synthesis of various water-soluble cis-stereoregular poly(phenylacetylene)s having a narrow molecular weight distribution, the molecular weight of which can be controlled by the initial feed ratio of the monomer to the catalyst. Moreover, the syntheses of water-soluble telechelic poly(phenylacetylene)s having various functional groups at both chain ends as well as a water-soluble block copolymer were achieved.

Well‐Controlled Living Polymerization of Phenylacetylenes in Water: Synthesis of Water‐Soluble Stereoregular Telechelic Poly(phenylacetylene)s

AbstractWell‐controlled living polymerization of water‐soluble phenylacetylene derivatives in water was achieved for the first time using a multicomponent catalytic system consisting of [Rh(nbd)Cl]2, an aryl boronic acid, diphenylacetylene having carboxy groups, a tetraalkylammonium hydroxide, and a water‐soluble triphenylphosphine. This catalytic system enables a direct synthesis of various water‐soluble cis‐stereoregular poly(phenylacetylene)s having a narrow molecular weight distribution, the molecular weight of which can be controlled by the initial feed ratio of the monomer to the catalyst. Moreover, the syntheses of water‐soluble telechelic poly(phenylacetylene)s having various functional groups at both chain ends as well as a water‐soluble block copolymer were achieved.

A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones.

A simple and efficient method for α-brominating lactones that affords α-bromolactones under mild conditions using tetraalkylammonium hydroxide (R4N+OH−) as a base was developed. Lactones are ring-opened with Br2 and a substoichiometric amount of PBr3, leading to good yields of the corresponding α-bromocarboxylic acids. Subsequent intramolecular cyclization over 1 h using a two-phase system (H2O/CHCl3) containing R4N+OH− afforded α-bromo lactones in good yields. This method can be applied at the 10 mmol scale using simple operations. α-Bromo-δ-valerolactone, which is extremely reactive and difficult to isolate, could be isolated and stored in a freezer for about one week using the developed method. Optimizing the solvent for environmentally friendly large-scale syntheses revealed that methyl ethyl ketone (MEK) was as effective. In addition, in situ-generated α-bromo-δ-valerolactone was directly converted into a sulfur-substituted functional lactone without difficulty by reacting it with a sulfur nucleophile in one pot without isolation. This new bromination system is expected to facilitate the industrial use of α-bromolactones as important intermediates.

Exfoliation of α-Zirconium Phosphate Using Tetraalkylammonium Hydroxides.

α-Zirconium phosphate (α-ZrP), a classical layered compound, has found widespread application. Exfoliation of α-ZrP has been mainly achieved by propylamine (PA) or tetrabutylammonium hydroxide (TBAOH), but the exact mechanism of exfoliation has not been completely elucidated. We examined the feasibility of exfoliation utilizing tetraalkylammonium hydroxide (TXAOH) and investigated the stepwise intercalation/exfoliation mechanism of α-ZrP. All of the TXAOHs examined (carbon number of the branches: 1-4) were able to exfoliate α-ZrP in an aqueous dispersion under ultrasonication. Furthermore, exfoliation of α-ZrP by two different exfoliators (either a mixture of two or sequentially) was also investigated to pinpoint the exfoliation mechanism. Our results indicate that small TXA cations are kinetically preferred to diffuse into the galleries of α-ZrP, while large TXA cations can help open up the galleries and facilitate transport of the already intercalated cations. These findings should help fellow researchers to choose the most suitable exfoliators for their own projects and develop better intercalation/exfoliation systems.

Bottom-up synthesis of titanophosphate nanosheets by the aqueous solution process.

The synthesis of titanophosphate nanosheets in aqueous sols was examined by the bottom-up process. The nanosheets were formed by mixing titanium iso-propoxide, phosphoric acid, and tetraalkylammonium hydroxide (NR4OH) aqueous solutions, followed by diluting with water and heating at 80 °C, forming translucent aqueous sols of titanophosphate nanosheets with the same crystal structure as layered titanium phosphate Ti2O3(H2PO4)2·2H2O. Whether the nanosheets were crystallized depended on the reactions during the mixing of reagents before the water dilution. By controlling the acid–base reactions between the Ti species, phosphoric acid, and the hydroxides of bulky cations in the aqueous sols, the one-pot process yielded highly water-dispersible, flake-like titanophosphate nanosheets. Under some synthetic conditions, nanosheets formed even in weakly basic aqueous sols. These nanosheets can be coated on a substrate with low alkali-resistance, or used for the removal of metal ions from neutral aqueous solutions.

Heterogeneity in the microstructure and dynamics of tetraalkylammonium hydroxide ionic liquids: insight from classical molecular dynamics simulations and Voronoi tessellation analysis.

Microscopic structural and dynamic heterogeneities were investigated for three ionic liquids (ILs), namely tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH), by employing classical molecular dynamics (MD) simulations. Structural heterogeneity was explored through radial distribution functions, domain analysis from Voronoi tessellation, spatial distribution functions, combined distribution functions, and structure factors. Radial distribution functions reveal that TEAH has a slightly different structure than TPAH and TBAH. The domain analysis shows that the three ILs have structural heterogeneity. The cations form continuous domains and the anions form discreet domains. The anions are trapped in the voids formed by the cationic domains. When the cation has sufficiently longer alkyl chains, the polar domains become discontinuous. The total structure factor reveals that a pre-peak is absent in TEAH due to a short alkyl chain. The cation head-anion partial structure factor further confirms this phenomenon. Polar and non-polar domains can be better distinguished in the ILs with longer alkyl chains. This distinctive structural behaviour leads to dynamic heterogeneity, which plays an important role in the applications related to ion transportation. To shed light on dynamic heterogeneity, we have calculated the mean square displacements, vibrational density of states, van Hove correlation, and non-Gaussian parameter. The diffusion of ions is lowest in TPAH among all the ILs. The dynamics are highly sluggish in these ILs. The peaks in the low frequency vibrational density of states undergo redshift with an increase in the alkyl chain length. The van Hove correlation functions and non-Gaussian parameter suggest the presence of dynamic heterogeneity in all three ILs. Dynamic heterogeneity is discussed through van Hove correlation functions and the non-Gaussian (NG) parameter was calculated to account for the deviation from Gaussian behaviour. The NG parameter suggests that TEAH has different dynamics than TPAH and TBAH.

Enhanced enzyme-catalyzed synthesis of l-methionine with ionic liquid additives

Abstract The low solubility of l -methionine and low activity of enzyme are the major hurdles during l -methionine production by the enzymatic conversion approach. In this study, we investigated various ionic liquids (ILs) as additives for the enzyme-catalyzed production of l -methionine from O-acetyl L-homoserine and methyl mercaptan. Among the ILs evaluated, we found that tetraalkylammonium hydroxide ILs enhanced the solubility of l -methionine as well as the activity of the enzyme. Methionine solubility decreased with increasing alkyl chain length but increased with increasing IL concentration. l -methionine could be dissolved up to 232 g/L in 10% tetramethylammonium hydroxide solution. The enzyme O-acetylhomoserine aminocarboxypropyltransferase reached its maximum activity when the IL concentration was 2.5% (3 times higher than that without ILs) and significantly decreased with increasing IL concentration. The stability of the enzyme also decreased rapidly after 2 h of incubation regardless of the presence or absence of ILs. Nevertheless, 74 g/L of l -methionine could be produced in a reaction media containing 2.5% tetraethylammonium hydroxide compared to 35 g/L of l -methionine obtained in a reaction system without ILs.

Application of Heterogeneous Catalysts in the First Steps of the Oseltamivir Synthesis

The first steps of oseltamivir synthesis from quinic acid involve acetalization and ester formation. These reactions are catalyzed by either acids or bases, which may be accomplished by heterogeneous catalysts. Sulfonic solids are efficient acid catalysts for acetalization and esterification reactions. Supported tetraalkylammonium hydroxide or 1,5,7-triazabicyclo[4.4.0]dec-5-ene are also efficient base catalysts for lactone alcoholysis and in this work, these catalysts have been applied in two alternative synthetic routes that lead to oseltamivir. The classical route consists of an acetalization, followed by a lactonization, and then a lactone alcoholysis. This achieves a 66% isolated yield. The alternative route consists of esterification followed by acetalization and is only efficient when an acetone acetal is used.

Solubilization of Cs and K from Tetraphenylborate Precipitates in Highly Alkaline Environments

Precipitated Cs tetraphenylborate, along with K tetraphenylborate and aqueous alkaline supernate, is present in certain high-level waste tanks at the Savannah River Site. Two possible processes for transferring the Cs+ (and K+) into the aqueous phase are described. One consists of displacement of the heavy alkalis from the solid tetraphenylborate by adding a tetraalkylammonium hydroxide. Almost 100% solubilization is obtained at ambient temperature using tetra-n-butylammonium hydroxide. The other consists of oxidative decomposition of the tetraphenylborate using persulfate. The extent of solubilization is found to increase with increasing temperature and persulfate:tetraphenylborate ratio. High yields of tetraphenylborate decomposition are obtained at elevated temperatures (55–90°C), and these yields increase with rising persulfate:tetraphenylborate ratios. The decomposition yields are lowered in the presence of nitrite, which is a component of the alkaline supernate, but are still significant, especially at elevated temperatures and high persulfate:tetraphenylborate ratios. The adverse effect of nitrite can be greatly reduced by lowering the pH.

Effect of surfactants on the morphologies of TiO2 particles with high-performance scattering layer in dye-sensitized solar cells

A series of TiO2 powders with various morphologies were synthesized using surfactant-assisted hydrothermal method by hydrolyzing the titanium tetra-isopropoxide (TTIP) precursor. Four types of tetraalkylammonium hydroxide (TANH) surfactants such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammomium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH) were used before hydrothermal crystallization. The results showed that the surfactants with different alkyl chain length of tetraalkylammonium cations (TAN+) had a great influence on the morphology, particle size, and crystalline phase of TiO2 particles. Under the same experimental conditions, the surfactants of TMAH, TEAH, TPAH, and TBAH resulting in the star-, flower-, rod-, and scree-shaped TiO2 particles (TM-, TE-, TP-, and TB-TiO2), respectively. The particle sizes were decreased in the range from ∼3.6μm to ∼220nm while increasing the alkyl chain length of the surfactants. All the TiO2 powders showed an anatase phase besides the TiO2 prepared from TMAH surfactant. The photovoltaic investigations of these TiO2 samples as the scattering layer in DSSCs indicated that the TB-TiO2 based cell exhibited the excellent power conversion efficiency of 9.88%, which was also higher than that of a device which fabricated without a scattering layer (8.83%). Among these scattering layers, TB-TiO2 has the optimum particle size (∼220nm) with the highest surface area leading to the largest dye adsorption value and an excellent efficiency. In order to further increase the dye adsorption of the photoanodes, the scattering layer was prepared by mixing the large (TB-TiO2) and small sized (a-TiO2) particles as composites with different weight ratios, leading to the highest efficiency of 10.53% at TB-/a-TiO2 (2:3).