Concentrated Aqueous Ammonia Research Articles

Vapor compression and energy dissipation in a collapsing laser-induced bubble

The composition of the gaseous phase of cavitation bubbles and its role on the collapse remains to date poorly understood. In this work, experiments of single cavitation bubbles in aqueous ammonia serve as a novel approach to investigate the effect of the vapor contained in a bubble on its collapse. We find that the higher vapor pressure of more concentrated aqueous ammonia acts as a resistance to the collapse, reducing the total energy dissipation. In line with visual observation, acoustic measurements, and luminescence recordings, it is also observed that higher vapor pressures contribute to a more spherical collapse, likely hindering the growth of interface instabilities by decreasing the collapse velocities and accelerations. Remarkably, we evidence a strong difference between the effective damping and the energy of the shock emission, suggesting that the latter is not the dominant dissipation mechanism at collapse as predicted from classical correction models accounting for slightly compressible liquids. Furthermore, our results suggest that the vapor inside collapsing bubbles gets compressed, consistently with previous studies performed in the context of single bubble sonoluminescence, addressing the question about the ability of vapors to readily condense during a bubble collapse in similar regimes. These findings provide insight into the identification of the influence of the bubble content and the energy exchanges of the bubble with its surrounding media, eventually paving the way to a more efficient use of cavitation in engineering and biomedical applications.

The influence of acidity of the film-forming solution on the structure and properties of thin SnO2 films

The paper considers the effect of acidity of film-forming solutions on the structure and optical properties of thin SnO2 films obtained by sol-gel method. For studying this, a series of solutions with a concentration of tin ions of 0.12 mol/l was prepared with the addition of a different amount of concentrated aqueous ammonia solution. An aqueous ammonia solution was used to regulate the pH level in the SnCl4/C2H5OH system. Solutions were applied to the substrate by a modified dipping method. The film was applied to one side of the substrate. The samples were dried in air for at least 30 minutes, then annealed in a muffle furnace at 400°C for 15 minutes. The structure of the films was studied using an optical microscope MPE-11. Transmission spectra were measured on a two-beam spectrophotometer SF-256 UVI (wavelength range 190-1200 nm.). During the experiment, a direct dependence of the formation of structures on the surface of the obtained films on the acidity of the initial solutions was revealed. With increasing pH, the growth of structures and a change in their shape were observed. The obtained results extend the fundamental knowledge in the field of development of methods for controlling the structure of thin SnO2 films, which is an important element in the creation of materials with improved functional properties.

New Oligodeoxynucleotide Derivatives Containing N-(Sulfonyl)-Phosphoramide Groups

New oligodeoxynucleotide derivatives containing N-(o-nitrobenzenesulfonyl)-phosphoramide (nosyl phosphoramide), N-(1-butanesulfonyl)-phosphoramide (busyl phosphoramide), or N-(1-hexanesulfonyl)-phosphoramide groups are described. These compounds were first obtained via solid-phase synthesis on an automatic DNA synthesizer according to the Staudinger reaction between the corresponding sulfonylazides (nosyl, busyl or hesyl azides) and the oligonucleotide containing 3',5'-dinucleoside-β-cyanoethyl phosphide—phosphitamide condensation product—immobilized onto a polymer carrier. In this case, the rate of the Staudinger reaction on the solid phase is higher for more electrophilic nosyl azide than those of less electrophilic busyl and hesyl azides. The nosyl, busyl, and hesyl phosphoramide groups are stable under oligonucleotide synthesis conditions, including acid detritylation and removal of protective groups to form oligonucleotide from a polymer carrier via treatment with concentrated aqueous ammonia at 55°C. The oligonucleotides modified with either nosyl or busyl phosphoramide groups at all internucleotide positions were first prepared. We showed that the stability of complementary duplexes of oligodeoxynucleotides containing busyl or hesyl phosphoramide groups with a single-stranded DNA is insignificantly lower than that of a native DNA:DNA duplex, whereas the destabilization of the duplex is clearer for a bulky hesyl phosphoramide group. The oligonucleotides bearing busyl phosphoramide group form complementary duplexes with a complementary RNA being less stable than native DNA:RNA duplex, but more stable than similar heteroduplexes formed from RNA oligonucleotides and the tosyl phosphoramide group. These DNA N-(sulfonyl)-phosphoramide derivatives are considered to be potential antisense oligonucleotides.

Development and Evaluation of a Novel Method for Determining Absorbent Composition in Aqueous Ammonia-Based CO2 and SO32– and SO42– Loaded Capture Process Solutions via FT-IR Spectroscopy

CO2 capture using aqueous ammonia is a potentially attractive option for emissions reductions from energy production and industrial processes. From an operational perspective, the capture absorbent must be monitored continuously to maintain the maximum efficiency of the capture process. In practice the composition of the absorbent is typically evaluated offline and retrospectively via wet chemistry methods, delaying any necessary variations to the process conditions to maintain maximum efficiency. Online absorbent monitoring methods incorporating spectroscopy via Raman or Fourier transform infrared (FT-IR) are attractive options due to their rapid response times and flexibility of the resulting output to be incorporated directly into process control packages. The present study outlines an evaluation of the FT-IR spectroscopic technique with analysis via partial least squares regression (PLSR) for a range of dilute to concentrated aqueous ammonia absorbents from ∼0.3–6.0 M and over a range of CO2 loadings ...

New oligodeoxynucleotide derivatives containing N-(methanesulfonyl)-phosphoramidate (mesyl phosphoramidate) internucleotide group

Novel oligonucleotide derivatives containing N-(methanesulfonyl)-phosphoramidate (mesyl phosphoramidate) group have been described. Solid-phase synthesis of these compounds using an automated DNA synthesizer has been performed for the first time, including the Staudinger reaction between methanesulfonyl azide (mesyl azide) and 3′,5′-dinucleoside 2-cyanoethyl phosphite within an oligonucleotide immobilized on the polymer support, which is a product of phosphoramidite coupling. The mesyl phosphoramidate group is stable to the conditions of oligonucleotide synthesis, in particular, during acidic detritylation and subsequent removal of protecting groups and cleavage of an oligonucleotide from the polymer support by concentrated aqueous ammonia or methylamine at 55°C. It has been shown that the stability of complementary duplexes of oligodeoxynucleotides containing the mesyl phosphoramidate group with a single-stranded DNA is not inferior to the stability of native DNA:DNA duplex. Furthermore, mesyl phosphoramidate oligonucleotides are able to form a complementary duplex with RNA, which is only slightly less stable than the equivalent DNA:RNA duplex. This raises the possibility of their application as potential antisense therapeutic agents.

New oligodeoxyribonucleotide derivatives bearing internucleotide N-tosyl phosphoramidate groups: Synthesis and complementary binding to DNA and RNA

N-Sulfonyl phosphoramidate derivatives of oligodeoxyribonucleotides containing N-tosyl phosphoramidate groups are first reported. The synthesis is based on Staudinger reaction between tosyl azide and 3′,5′-dinucleoside β-cyanoethyl phosphite comprising the immobilized oligonucleotide, which is obtained by the phosphoramidite coupling during the solid-phase oligonucleotide synthesis. The N-tosyl phosphoramidate group was stable under conditions of the oligonucleotide synthesis, in particular, upon acidic detritylation followed by the removal of protective groups and cleavage from the polymer support by the treatment with concentrated aqueous ammonia at 55°C. The stability of DNA and RNA duplexes of the model oligonucleotides containing N-tosyl phosphoramidate groups was only slightly lower than that of native DNA:DNA and DNA:RNA duplexes, respectively.

Controllable preparation of 2D and 3D ZnO micro-nanostructures and their photoelectric conversion efficiency

The different morphological ZnO micro-nanostructures were prepared by solvothermal method and their photoelectric conversion efficiency applied in dye-sensitised solar cells (DSSCs) were be analysed. The morphologies and crystalline structures of the ZnO nanocrystals grown under different driving forces, which were characterised by scanning electron microscopy, transmission electron microscopy and X-ray diffraction measurements. The results showed that different additives caused different growing directions for the crystal plane and then formed ZnO micro-nanostructures with different morphologies. The UV–visible diffuse reflectance spectra displayed that nanorod-assembled 3D urchin-like ZnO had the strongest absorbance intensity. When they were used as photo-anodes for DSSCs, the I–V curve showed their photoelectric conversion efficiency enhanced to different degrees. The highest was that of the nanorod-assembled 3D urchin-like ZnO micro-superstructures, which was synthesised under NaBH4 and 25 % concentrated aqueous ammonia reaction system. Its photoelectric conversion efficiency is 2.37 %. Other hand, this simple and controlled method is promising to prepare the low-cost, environmentally friendly and high performance innovative structural materials.

Foaming of polysiloxane resins with ethanol: A new route to pyrolytic macrocellular SiOC foams

Polysiloxane foams as precursors to silicon oxycarbide (SiOC) foams were prepared via simultaneous cure and foaming of liquid methylsiloxane resins, using the relatively environment-friendly ethanol as blowing additive of the boiling-solvent-type, and concentrated aqueous ammonia as catalyst. In order to achieve foam regularity, siloxane-based surfactants were added, and bubble nucleation by mechanical stirring was performed. The precursor foams were subsequently pyrolysed in nitrogen at 1000°C, yielding SiOC foams as end products. The properties of the latter were fine-tuned during the foaming of the precursors, by the amount of added ethanol and by the time of mechanical stirring prior to foaming. The so-obtained SiOC foams displayed densities of 0.17–0.42g/cm−3, corresponding to macro-porosities of 91–79%, compressive strength of 1–6MPa, and elastic moduli of 0.2–1.6GPa.

Effective adsorption of phenols using nitrogen-containing porous activated carbon prepared from sunflower plates

Nitrogen-containing porous carbons, the 800SP-NH3, were synthesized using sunflower plates as the major carbon source carbonized at 800°C and activated with concentrated aqueous ammonia at the same temperature. The porous carbons were characterized by nitrogen physical adsorption-desorption, surface area analyzer, FT-IR, and SEM. The adsorption properties of the porous carbons towards phenols were also investigated by batch methods. The test results show that the average pore diameter of porous carbon is smaller than 2 nm, and nitrogen-containing chemical groups are formed on its surface. The adsorption capacity for phenol, 4-chlorophenol, and p-nitrophenol is 316.5mg/g, 330.24mg/g and 387.62mg/g due to its developed pore structure and nitrogen-containing chemical groups. The adsorption isotherm data greatly obey the Langmuir model.

High surface – Highly N-doped carbons from hydrothermally treated tannin

Nitrogen-doped carbon materials (NCMs) were obtained by amination of tannin by hydrothermal carbonisation (HTC). NCMs presented different morphologies depending on the amination method: (i) powders by HTC of tannin in a concentrated aqueous ammonia solution; (ii) gels without using any crosslinker by HTC in distilled water of tannin first dissolved in concentrated ammonia and then evaporated. Whatever the method, (i) or (ii), HTC was carried out at different temperatures: 180, 190, 200, 210 or 220°C, with further pyrolysis at 900°C under nitrogen. The morphology and chemical composition of the resultant materials were discussed. We compared our results with those reported in the open literature and we concluded that HTC of tannin in a concentrated aqueous ammonia solution allowed obtaining outstanding materials because they have both surface areas, higher than 500m2g−1, and high N content, around 8wt.%.

Synthesis of high-performance nitrogen-containing porous carbon and adsorption properties towards metal ions

Waste water containing metal ions is one of the main pollution sources of surface water and groundwater, and must be removed effectively. In this paper, nitrogen-containing porous carbons, the 800KH-H2O and the 800KH-NH3, were synthesized using sunflower plates as the major carbon source carbonized at 800°C and activated with distilled water and concentrated aqueous ammonia at the same temperature. The porous carbons were characterized by surface area analyzer, Fourier transform infrared, element analysis, and scanning electron microscopy. The adsorption properties of the porous carbons toward metal ions were studied by batch methods. The test results show that the average pore diameter of porous carbon is smaller than 2 nm, and nitrogen-containing chemical groups were formed on its surface. The adsorption capacities of the 800KH-NH3 toward Pb2+ are as high as 786 mg g−1 due to its developed pore structure and nitrogen-containing chemical groups. The adsorption process could be well described by the intraparticle mass transfer diffusion model and the Langmuir–Freundlich model.

Concise and Efficient Synthesis of 3′-O-Tetraphosphates of 2′-Deoxyadenosine and 2′-Deoxycytidine

We describe concise and efficient synthesis of biologically very important 3′-O-tetraphosphates namely 2′-deoxyadenosine-3′-O-tetraphosphate (2′-d-3′-A4P) and 2′-deoxycytidine-3′-O-tetra-phosphate (2′-d-3′-C4P). N6-benzoyl-5′-O-levulinoyl-2′-deoxyadenosine was converted into N6-benzoyl-5′-O-levulinoyl-2′-deoxyadenosine-3′-O-tetraphosphate in 87% yield using a one-pot synthetic methodology. One-step concurrent deprotection of N6-benzoyl and 5′-O-levulinoyl groups using concentrated aqueous ammonia resulted 2′-d-3′-A4P in 74% yield. The same synthetic strategy was successfully employed to convert N4-benzoyl-5′-O-levulinoyl-2′-deoxycytidine into 2′-d-3′-C4P in 68% yield.

Concise and efficient synthesis of 3′-O-triphosphates of 2′-deoxyadenosine and 2′-deoxycytidine

We describe concise and efficient synthesis of 2′-deoxyadenosine-3′-O-triphosphate (2′-d-3′-ATP) and 2′-deoxycytidine-3′-O-triphosphate (2′-d-3′-CTP) which are well known for their various biological applications. One-pot synthetic methodology was used to convert N6-Benzoyl-5′-O-levulinoyl-2′-deoxyadenosine into N6-Benzoyl-5′-O-levulinoyl-2′-deoxyadenosine-3′-O-triphosphate in 72% yield. One-step concurrent deprotection of N6-Benzoyl and 5′-O-levulinoyl groups using concentrated aqueous ammonia resulted in 2′-d-3′-ATP in 75% yield. The same synthetic strategy was successfully employed to convert N4-Benzoyl-5′-O-levulinoyl-2′-deoxycytidine into 2′-d-3′-CTP in 66% yield.

Orbital ordering of Cu2+ ions in concentrated aqueous ammonia solutions of copper chloride, sulfate, and acetate as probed by ESR

Orbital ordering of Cu2+ ions in concentrated aqueous ammonia solutions of copper chloride, sulfate, and acetate as probed by ESR

Unraveling the structure of sugarcane bagasse after soaking in concentrated aqueous ammonia (SCAA) and ethanol production by Scheffersomyces (Pichia) stipitis

BackgroundFuel ethanol production from sustainable and largely abundant agro-residues such as sugarcane bagasse (SB) provides long term, geopolitical and strategic benefits. Pretreatment of SB is an inevitable process for improved saccharification of cell wall carbohydrates. Recently, ammonium hydroxide-based pretreatment technologies have gained significance as an effective and economical pretreatment strategy. We hypothesized that soaking in concentrated aqueous ammonia-mediated thermochemical pretreatment (SCAA) would overcome the native recalcitrance of SB by enhancing cellulase accessibility of the embedded holocellulosic microfibrils.ResultsIn this study, we designed an experiment considering response surface methodology (Taguchi method, L8 orthogonal array) to optimize sugar recovery from ammonia pretreated sugarcane bagasse (SB) by using the method of soaking in concentrated aqueous ammonia (SCAA-SB). Three independent variables: ammonia concentration, temperature and time, were selected at two levels with center point. The ammonia pretreated bagasse (SCAA-SB) was enzymatically hydrolysed by commercial enzymes (Celluclast 1.5 L and Novozym 188) using 15 FPU/g dry biomass and 17.5 Units of β-glucosidase/g dry biomass at 50°C, 150 rpm for 96 h. A maximum of 28.43 g/l reducing sugars corresponding to 0.57 g sugars/g pretreated bagasse was obtained from the SCAA-SB derived using a 20% v/v ammonia solution, at 70°C for 24 h after enzymatic hydrolysis. Among the tested parameters, pretreatment time showed the maximum influence (p value, 0.053282) while ammonia concentration showed the least influence (p value, 0.612552) on sugar recovery. The changes in the ultra-structure and crystallinity of native SCAA-SB and enzymatically hydrolysed SB were observed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The enzymatic hydrolysates and solid SCAA-SB were subjected to ethanol fermentation under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Scheffersomyces (Pichia) stipitis NRRL Y-7124 respectively. Higher ethanol production (10.31 g/l and yield, 0.387 g/g) was obtained through SSF than SHF (3.83 g/l and yield, 0.289 g/g).ConclusionsSCAA treatment showed marked lignin removal from SB thus improving the accessibility of cellulases towards holocellulose substrate as evidenced by efficient sugar release. The ultrastructure of SB after SCAA and enzymatic hydrolysis of holocellulose provided insights of the degradation process at the molecular level.

Reaction of condensed tannins with ammonia

Reaction of condensed (flavonoid) mimosa tannin extracts with concentrated aqueous ammonia has been investigated. For that purpose, catechin was also used as a flavonoid model compound and treated in similar conditions. Solid state CP-MAS 13C NMR and MALDI-ToF spectroscopy studies revealed that, unlike what was recently theorised, amination is not always regioselective and leading to the conversion of one single OH group in C4′ into NH2. In the present study, new reactions have been evidenced, clearly leading to multiamination of several phenolic hydroxyl groups, heterocycle opening, and oligomerisation and cross-linking through the formation of N bridges between flavonoid units.

The state of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate

Stabilization of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate in a wide range of ammonium ion concentrations has been studied by EPR and electronic absorption spectroscopy. Three types of Cu2+ associates with different types of orbital ordering have been identified. The ammonium ion concentration in a solution has a decisive effect on the type of orbital ordering of Cu2+ ions in associates. In all cases, Cu2+ ordering in associates is caused by the existence of bridging OH groups in the axial and equatorial positions of [Cu(NH3)n(H2O)6 − n]2+ complexes (n < 6). At a high concentration of ammonium ions, weakly bound associates of tetramminecopper with the \(d_{x^2 - y^2 }\) ground state are formed. In solutions with low ammonium concentrations, bulky associates with the \(d_{y^2 }\) and \(d_{x^2 - z^2 }\) ground states and associates of Cu2+ ions with the \(d_{x^2 - y^2 }\) ground state with hydroxyl groups in the equatorial plane and axial water molecules are formed.

A 1-D cyano-bridged coordination polymer, [Ni(NH3)6]2[{Ni(NH3)4}{Re12CS17(CN)6}] · 8H2O: reactivity studies of dodecanuclear rhenium cluster anion [Re12CS17(CN)6]6− in Ni(II)-ammonia system

A cyano-bridged coordination polymer, [Ni(NH3)6]2[{Ni(NH3)4}{Re12CS17(CN)6}] · 8H2O, has been synthesized by reaction between concentrated aqueous ammonia solution of NiCl2 and aqueous solution of K6[Re12CS17(CN)6]. The compound has been characterized by single crystal X-ray diffraction, IR-spectroscopy and EDS analysis. The compound adopts 1-D structure, which consists of anionic chains [{Ni(NH3)4}{Re12CS17(CN)6}], discrete cations [Ni(NH3)6]2+ and crystal waters bonded together by hydrogen bonds. The influence of reagent concentrations on composition and structure of the resultant product has also been studied and discussed.

Specific features of association of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate as probed by ESR

Specific features of association of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate as probed by ESR

Maleimide-Dimethylfuran exo Adducts: Effective Maleimide Protection in the Synthesis of Oligonucleotide Conjugates

The reaction of maleimide-containing compounds with 2,5-dimethylfuran gives a mixture of exo and endo isomers from which the exo cycloadduct can be easily isolated taking advantage of its stability in concentrated aqueous ammonia. Bifunctional compounds incorporating a dimethylfuran-protected maleimide (exo adduct) have been attached to resin-linked oligonucleotide chains. Removal of protecting groups masking oligonucleotide functionalities followed by retro-Diels-Alder maleimide deprotection affords maleimido-oligonucleotides suitable for conjugation, as assessed by their reaction with different thiols.