Ammonium Hydroxide Solution Research Articles

Direct synthesis of zeolitic imidazolate framework-8/chitosan composites in chitosan hydrogels

Zeolitic imidazolate framework-8 (ZIF-8)/chitosan composites were prepared in the chitosan hydrogels. The concentrations of the chitosan and the alkaline solution were varied to the synthesis of the ZIF-8/chitosan composites. In the chitosan hydrogels with the addition of ammonium hydroxide solution, the resulting ZIF-8 crystals exhibited an unusual XRD structure that the XRD peak at about 18o (222) became the strongest. The XRD peak intensity ratio of (222)/(011) increased from 0.68 to 1.5–5.2 in the presence of chitosan hydrogels. ZIF-8/chitosan composites (FC2) were composed of aggregated nanosized particles, and exhibited a higher CO2 adsorption than normal ZIF-8 crystals. After removing chitosan from FC2, XRD pattern of the resulting ZIF-8 crystals returned to the normal state and the morphology kept the same as the composite.

Continuous precipitation of ceria nanoparticles from a continuous flow micromixer

Cerium oxide nanoparticles were continuously precipitated from a solution of cerium(III) nitrate and ammonium hydroxide using a static microchannel T-mixer. T-mixer synthesis results were compared with synthesis results from batch precipitation. Findings show that the method of mixing is important in the ceria precipitation process. Uniform porous film structures and nanorods were produced when the particle chemistry was synthesized using T-mixing followed by spin coating. Batch mixing, when using higher NH4OH feed concentrations followed by spin coating, was characterized by the heavy agglomeration of nanoparticles. Similar, high aspect ratio nanorods were produced when feed conditions in both batch mixing and T-mixing were identical demonstrating that the momentum effects of continuous microchannel T-mixing did not impact the synthesis process. In addition, it was found that the micromixing approach reduced the exposure of the Ce(OH)3 precipitates to oxygen, yielding hydroxide precipitates in place of CeO2 precipitates. The key advantage of the micro-scale T-mixing approach is higher throughput which is important for the scaling of ceria nanoparticle production.

Simplifying patterning process of ZnO nanowires by one step development and etching process

We present herein a simple protocol of growing a patterned ZnO nanowire by etching of ZnO seed layer in the tetramethyl ammonium hydroxide (TMAH) solution. The ZnO seed layer was fabricated by sol–gel method using zinc acetate solution and patterned by using photolithographic method. Patterned ZnO seed layer as etched in the TMAH solution, followed by growth of ZnO nanowires by hydrothermal method. Remarkable point of present ZnO seed layer patterning is that development of UV-exposed photoresist and etching of ZnO seed layer is subsequently processed in aqueous TMAH solution without interruption. The grown ZnO nanowires were analyzed using XRD patterns to exhibit high purity and degree of crystallinity, and showed very good pattern fidelity.

Fatty amides synthesized from vegetable oil as extractant of molybdenum(VI)

In this study, fatty amides (FAs) synthesized from palm olein were used to extract and separate Mo(VI) from acidic media. Effects of various parameters upon the separation of Mo(VI) from Co(II), Ni(II), Al(III) and Mn(II), including extractant concentration, metal ion concentration, contact time, diluent, and acidity, were investigated. It was found that Mo(VI) was successfully separated from the above commonly associated metal ions by stripping from the loaded organic phase. Different acidic and alkaline solutions were used. Ammonium hydroxide solution was an optimal. Extraction of Mo(VI) into the organic phase involved the formation of 1:3 complexes. This work presents the development of a low-cost and environmentally friendly extractant to recycle and recover molybdenum.

Rapid determination of thiamine, riboflavin, niacinamide, pantothenic acid, pyridoxine, folic acid and ascorbic acid in Vitamins with Minerals Tablets by high-performance liquid chromatography with diode array detector

A simple, isocratic, and stability-indicating high-performance liquid chromatography (HPLC) method has been developed for the rapid determination of thiamine (VB(1)), niacinamide (VB(3)), pyridoxine (VB(6)), ascorbic acid (VC), pantothenic acid (VB(5)), riboflavin (VB(2)) and folic acid (VB(9)) in Vitamins with Minerals Tablets (VMT). An Alltima C(18) column (250 mm × 4.6 mm i.d., 5 μm) was used for the separation at ambient temperature, with 50mM ammonium dihydrogen phosphate (adjusting with phosphoric acid to pH 3.0) and acetonitrile as the mobile phase at the flow rate of 0.5 ml min(-1). VB(1), VB(3), VB(6), VC and VB(5) were extracted with a solution containing 0.05% phosphoric acid (v/v) and 0.3% sodium thiosulfate (w/v), and were then simultaneously analyzed by using the mobile phase of phosphate buffer-acetonitrile (95:5, v/v), while VB(2) and VB(9) were extracted with a solution containing 0.5% ammonium hydroxide solution (v/v), and were then simultaneously analyzed by using the mobile phase of phosphate buffer-acetonitrile (85:15, v/v). The detection wavelengths were 275 nm for VB(1), VB(3), VB(6), VC, 210 nm for VB(5), and 282 nm for VB(2) and VB(9). The method showed good system suitability, sensitivity, linearity, specificity, precision, stability and accuracy. All the seven water-soluble vitamins were well separated from other ingredients and degradation products. Method comparison indicated good concordance between the developed method and the USP method. The developed method was reliable and convenient for the rapid determination of VB(1), VB(3), VB(6), VC, VB(5), VB(2) and VB(9) in VMT.

Effects of surface chemical properties of activated carbon modified by amino-fluorination for electric double-layer capacitor

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1M H2SO4 electrolyte, in which it was observed that the specific capacitances increased from 215 to 389Fg−1 and 119 and 250Fg−1 with the current densities of 0.1 and 1.0Ag−1, respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43molL−1 ammonium hydroxide and 2.06molL−1 hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material.

Peptization technique in the synthesis of titania–silica composites and their photocatalytic properties

A comparative study of titania–silica composite (TSC) synthesized via peptization sol–gel method was conducted. Typically, titanium hydroxide gel (Ti(OH)4) was formed by condensation of titanium oxychloride solution using adequate amount of ammonium hydroxide solution. The preformed gel was peptized either in silicic acid (SA) or nitric acid (NA) to form a sol. The composite was characterized by XRD, FTIR, SEM, TEM, TGA, and N2 physisorption studies. The XRD patterns and the TEM micrographs confirmed that thermal-derived samples of the composite, formed using silicic acid as a silica source and peptizing agent (TSC–SA), yielded TiO2SiO2 composite with a single-phase (anatase phase); while a mixture of both anatase and rutile phases were observed in the composite (TSC–NA), where nitric acid was used as a peptizing agent. FTIR analysis showed the vibration band assignable to the TiOSi bond at 945cm−1, suggesting that titania was incorporated into silica to form a composite. Furthermore, a simple experiment of photodegradation of methyl orange in the presence of sunlight was performed to demonstrate the practical efficacy of the composites synthesized via this method. The results indicated that the calcined samples of TSC–NA-800 had the highest activity due to its superior properties.

Comparison of Gold Particle Removal from Fused Silica and Thermal Oxide Surfaces in Dilute Ammonium Hydroxide Solutions

Removal of gold particles (40 nm and 100 nm) from fused silica and thermal oxide surfaces in dilute ammonium hydroxide solutions has been investigated. The particle removal efficiency (PRE) from fused silica surface has been found to be a strong function of ammonium hydroxide concentration and bath temperature. PRE increases from 0 to 85 % with increase in bath temperature from 30 to 80 °C for ammonium hydroxide concentration of 1 %. Addition of megasonic energy to the ammonium hydroxide bath at 30 °C has also shown to improve the PRE significantly. In the case of thermal oxide, the removal of gold particles is much easier compared to that from fused silica. Even for cleaning at 30 °C, the PRE for oxide surface increases from 10 to 90 % with increase in ammonium hydroxide concentration from 0 % to 4 %. Atomic force microscopy measurements reveal that an adhesion force of 10 mN/m exists between fused silica and gold particles in 4 % ammonium hydroxide solution as opposed to only repulsive force in the case of thermal oxide.

Synthesis of magnetic iron oxide particles: Development of an in situ coating procedure for fibrous materials

We report on the synthesis of magnetic iron oxide particles; study of the particles’ formation was undertaken to investigate conditions of precipitation in order to apply it efficiently to cellulose fibre coating procedures. Synthesis of magnetic particles was performed, comprised of variations of molar concentrations of precursor solutions as well as different addition protocols of reactants into the reaction system. This allowed us to investigate the formation of iron oxide particles from different starting points. Following the synthesis, an evaluation of particles’ formation in different stages of synthesis procedure i.e. at different pH values and analysis of particles’ properties was carried out. Structural properties (crystallinity, size of the single magnetite crystals), their magnetic and colloidal properties were correlated with the synthesis procedure used. Procedure with controlled addition of ammonium hydroxide solution into a solution of precursor iron salts results in magnetic particles with largest crystallite size and the most intense X-ray diffraction patterns. Size and crystallinity of formed particles are also dependent upon the molar concentrations of Fe2+ and Fe3+ ions. Highest values of saturation magnetization are again exhibited by particles, produced with controlled addition of catalyst into a solution of precursor, a consequence of their ordered structure, which also favourably influences their colloidal properties when dispersed in an aqueous-based ferrofluid. Gained insight of the presented synthesis study will prove useful when in situ precipitation of magnetic iron oxide particles will be used for the preparation of magnetic solid cellulose substrates, since it will allow for the optimal adjustment of process conditions.

The mechanism for hydrothermal growth of zinc oxide

The mechanism for hydrothermal growth of ZnO was studied in ammonium hydroxide solution at pH near 11 (0.3 M NH4OH). The products formed at 20–90 °C and ambient pressure were characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photon Spectroscopy (XPS), X-ray Diffraction (XRD) and Secondary Ion Mass Spectroscopy (SIMS). Under these conditions, the growth of ZnO occurs via the initial precipitation of e-Zn(OH)2 (Wulfingite), which subsequently dehydrates, to form Wurtzite ZnO. Isotope tracking experiments show that most of the oxygen atoms do not mix with water during the conversion from Wulfingite to ZnO, and thus that the reaction proceeds primarily in the solid phase rather than through dissolution then reprecipitation. XPS results show that the surface of hydrothermal ZnO consists primarily of zinc hydroxide at lower temperatures, and there is a significant fraction of zinc hydroxide persisting at higher temperatures. Together these results show that much of the solid-solution interface is mainly comprised of zinc hydroxide not ZnO. These findings may have implications for understanding how small organic molecules can be used to control the morphology of zinc oxide crystals grown under hydrothermal conditions.

Determination of Total Iodine in Infant Formula and Nutritional Products by Inductively Coupled Plasma/Mass Spectrometry: Single-Laboratory Validation

A single-laboratory validation by inductively coupled plasma-mass spectrometry was developed for the determination total iodine (m/z 127) in infant formula and adult nutritional products. All samples were digested in nitric acid using a closed vessel microwave oven system; Te (m/z 130) was used as an internal standard. To prevent loss of iodine, ammonium hydroxide solution was added to the samples immediately after digestion. The method quantitation limit for total iodine was 0.3 ng/mL, but a practical LOQ was used at 1.0 ng/mL, a concentration at which there was a negligible bias due to nonlinearity. The total iodine concentrations (112-1900 ng/g) in 14 out of 15 nutritional products were within specification limits. Within-day and day-to-day (6 independent days) precision values were < 10% RSD. The observed precision for the overall mean (18 independent days) of a control sample was approximately 4% RSD. In two National Institute of Standards and Technology standard reference materials, total iodine results were within certified limits. Sample spike recoveries for all 15 nutritional products were 92-105%. The data show that a conventional microwave oven digestion procedure can be used to prepare samples for iodine determination. Therefore, this technique is very compatible with other methods being proposed as modern official methods for the analysis of minerals in nutritional products.

HfSiON High-k Layer Compatibility Study with TetraMethyl Ammonium Hydroxide (TMAH) Solution

Compatibility of HfSiON high-k layer with wet etching using TMAH solution is studied for polycrystalline silicon dummy gate removal in high-k first gate-last process. The electrical and physical characterizations of the HfSiON layers after etching reveal that the HfSiON layer will be etched when exposed to the TMAH solution under certain conditions. No clear degradation, however, has been found after etching in a 10 vol% TMAH solution below 60◦C, suggesting a processing window for polycrystalline silicon dummy gate removal in the high-k first metal gate last process. © 2012 The Electrochemical Society. [DOI: 10.1149/2.008205esl] All rights reserved.

Realisation of silicon piezoresistive accelerometer with proof mass-edge-aligned-flexures using wet anisotropic etching

This Letter presents simulation, fabrication and testing of a high-performance quad-beam silicon piezoresistive accelerometer with very low cross-axis sensitivity. Cross-axis sensitivity in piezoresistive accelerometers is an important issue particularly for high-performance applications. In the present Letter, low cross-axis sensitivity is achieved by improving the device stability by placing four flexures in line with the proof mass edges. The accelerometer device is realised in a single-step double-sided bulk micromachining technique using a 5% dual-doped tetra methyl ammonium hydroxide solution as an anisotropic etchant. Test results of four fabricated devices show an average prime-axis sensitivity of 559.5 µV/g/5 V, a maximum cross-axis sensitivity of 0.62% full scale (FS acceleration=13 g) of the prime-axis sensitivity and nonlinearity at a level of 0.5% of FS which are comparatively better than already reported devices and commercially available piezoresistive sensors.

Wet ammonia Synthesis of Semiconducting N:Ta2O5, Ta3N5 and β-TaON Films for Photoanode Applications

Tantalum oxynitride (β-TaON) is a promising photoanode material for photoelectrochemical water splitting. However, the synthesis of phase-pure β-TaON films is a challenging task. This paper describes a novel approach to achieve this by the controlled nitridation of Ta2O5 films under a flow of ammonia gas (ammonolysis), which was obtained by bubbling argon through an aqueous ammonium hydroxide solution followed by a 5Å molecular sieve to remove the water. Depending on the nitridation conditions, either nitrogen-doped Ta2O5 or Ta3N5 was obtained as a thermodynamically stable phase. The evolution of the nitridation process was monitored in-situ using optical transmission spectroscopy, which revealed that the transformation of Ta2O5 to Ta3N5 occurred within minutes, through a series of intermediate oxynitride phases. This suggested the possibility of synthesizing the desired β-TaON phase by quenching the sample at the right time during the nitridation process. By choosing the right ammonolysis conditions (750°C, flow rate 50ml/min.), we were able to slow down the nitridation process and terminate it before the oxide was fully converted to Ta3N5. A post-nitridation heat treatment at 800°C indeed resulted in the formation of the desired β-TaON phase.

Simultaneous analysis of sildenafil, vardenafil, tadalafil, and their desalkyl metabolites in human whole blood and urine by isotope dilution LC–MS–MS

Given that there are many autopsy cases in which erectile dysfunction (ED) treatment drugs can be detected from elderly men who are diagnosed to have died of cardiovascular disorders, the degree of cardiovascular risk posed by ED treatment drugs is still controversial. Moreover, counterfeit ED drugs or illegal dietary supplements containing ED drugs are also threats to public health. In this study, we established a detailed procedure for simultaneous analysis of typical ED drugs (sildenafil, vardenafil, tadalafil) and their metabolites in human blood and urine by isotope dilution liquid chromatography-tandem mass spectrometry (LC–MS–MS). Each sample of whole blood and urine containing the three ED treatment drugs, their metabolites, and deuterated internal standards (ISs) was diluted with alkalinized water, loaded onto an Oasis HLB cartridge, washed with dilute ammonium hydroxide solution, and eluted with chloroform. The eluate was acidified with methanol and concentrated HCl and evaporated to dryness. The resulting residue was reconstituted with methanol and mobile phase solution, and 5 μl of the solution was injected into an LC–MS–MS instrument. The determinations were made by multiple reaction monitoring using each product ion. The recovery rates of the drugs, metabolites, and ISs from whole blood and urine ranged from 80.7 to 127%. Good linearity was obtained for all drugs and their metabolites in the range of 1–100 ng/ml in whole blood and urine with correlation coefficients greater than 0.99. The detection limits (signal-to-noise ratio = 3) for all compounds were not higher than 0.05 ng/ml. Intraday and interday accuracy and precision data were also satisfactory for all compounds in whole blood and urine. Actual measurements of sildenafil and N-desmethyl sildenafil were also demonstrated by analysis of whole blood and urine specimens from two male volunteers after ingestion of a 25-mg tablet of sildenafil.

Anionic iron(III) porphyrins immobilized on zinc hydroxide chloride as catalysts for heterogeneous oxidation reactions

This work describes the immobilization of an anionic iron(III) porphyrin (FePor) family on zinc hydroxide chloride (ZHC), a layered hydroxide salt prepared by reacting an aqueous zinc chloride solution with an ammonium hydroxide solution. The FePor immobilization was performed at room temperature under magnetic stirring, under air atmosphere, of each complex ethanol solution and the ZHC solid support suspension. The materials obtained were characterized by X-ray powder diffraction (XRPD), ultraviolet-visible spectroscopy (UV–vis) (solid samples), Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The catalytic activity of the solids was investigated in cyclooctene, cyclohexane and n-heptane heterogeneous catalytic oxidation reactions with iodosylbenzene as the oxygen donor. The solid catalyst's reutilization capacity was also investigated and the heterogeneous character of the catalytic process was confirmed. The compounds and the catalytic activity of FePor-ZHC were compared with the synthesis and catalytic activity of the same FePor immobilized on zinc hydroxide nitrate (ZHN). Though the matrixes are similar, the results obtained were exactly the opposite when the selectivity was analyzed.

Characterization and Scope of S-layer Protein O-Glycosylation in Tannerella forsythia

Cell surface glycosylation is an important element in defining the life of pathogenic bacteria. Tannerella forsythia is a Gram-negative, anaerobic periodontal pathogen inhabiting the subgingival plaque biofilms. It is completely covered by a two-dimensional crystalline surface layer (S-layer) composed of two glycoproteins. Although the S-layer has previously been shown to delay the bacterium's recognition by the innate immune system, we characterize here the S-layer protein O-glycosylation as a potential virulence factor. The T. forsythia S-layer glycan was elucidated by a combination of electrospray ionization-tandem mass spectrometry and nuclear magnetic resonance spectroscopy as an oligosaccharide with the structure 4-Me-β-ManpNAcCONH(2)-(1→3)-[Pse5Am7Gc-(2→4)-]-β-ManpNAcA-(1→4)-[4-Me-α-Galp-(1→2)-]-α-Fucp-(1→4)-[-α-Xylp-(1→3)-]-β-GlcpA-(1→3)-[-β-Digp-(1→2)-]-α-Galp, which is O-glycosidically linked to distinct serine and threonine residues within the three-amino acid motif (D)(S/T)(A/I/L/M/T/V) on either S-layer protein. This S-layer glycan obviously impacts the life style of T. forsythia because increased biofilm formation of an UDP-N-acetylmannosaminuronic acid dehydrogenase mutant can be correlated with the presence of truncated S-layer glycans. We found that several other proteins of T. forsythia are modified with that specific oligosaccharide. Proteomics identified two of them as being among previously classified antigenic outer membrane proteins that are up-regulated under biofilm conditions, in addition to two predicted antigenic lipoproteins. Theoretical analysis of the S-layer O-glycosylation of T. forsythia indicates the involvement of a 6.8-kb gene locus that is conserved among different bacteria from the Bacteroidetes phylum. Together, these findings reveal the presence of a protein O-glycosylation system in T. forsythia that is essential for creating a rich glycoproteome pinpointing a possible relevance for the virulence of this bacterium.

Validated LC–MS/MS method for the quantitative determination of the glucosylceramide synthase inhibitor miglustat in mouse plasma and human plasma and its application to a pharmacokinetic study

A sensitive liquid chromatography–tandem mass spectrometry method has been developed to quantify miglustat in mouse plasma and in human plasma. The method involved simple protein precipitation with methanol. N-(n-nonyl)deoxynojirimycin was used as internal standard. Separation was performed on a Gemini C 18 column (2.1 mm × 50 mm, particle size 5 μm) with a binary gradient at a flow rate of 600 μl/min. The mobile phases were methanol and water both containing 0.01% of a 25% ammonium hydroxide solution. The triple stage quadrupole mass spectrometer was operated in APCI mode using the transitions m/ z 220.1 ≥ 158.0 for miglustat and m/ z 290.1 ≥ 228.0 for the internal standard. The method was linear over a range of 10–10,000 ng/ml. The intra-day coefficients of variation for mouse plasma were equal to or smaller than 14.1%. The intra- and inter-day accuracies were 84.5–107.2% and 90.9–104.0%, respectively. For human plasma the intra-day coefficients of variation were equal to or smaller than 13.5%, while accuracies ranged between 93.6% and 100.0%. The validated method offered increased sensitivity (10 times higher) and decreased cycle times compared to other methods. It was successfully applied to the pharmacokinetic assessment of miglustat during treatment of patients with cystic fibrosis.

Optimization of dynamic pH junction for the sensitive determination of amino acids in urine by capillary electrophoresis

A capillary electrophoresis method with UV-absorbance detection was studied and optimized for the determination of underivatized amino acids in urine. To improve concentration sensitivity the utility of in-capillary analyte stacking via dynamic pH junction was investigated with phenylalanine (Phe) and tyrosine (Tyr) as model amino acids. Before sample injection, a plug of ammonium hydroxide solution was injected to enable analyte concentration. Samples were 1:1 (v/v) mixed with background electrolyte (1 M formic acid) prior to injection. The effect of the injected sample volume, and the injected ammonium hydroxide volume and concentration on analyte stacking and separation performance was investigated. The optimal volume of ammonium hydroxide depended on the injected sample volume. Using a dynamic pH junction good resolution (1.4) was obtained for a sample injection volume of 10% of the capillary (196 nl) with Phe and Tyr dissolved in water. Limits of detection (LODs) were 0.036 and 0.049 μM for Phe and Tyr, respectively. For urine samples, the optimized procedure comprised a 1.7-nl injection of 12.5% ammonium hydroxide, followed by a 196-nl injection of urine spiked with Phe and Tyr. Satisfactory resolution was obtained and amino acid peak widths at half height were only 1.6 s indicating efficient stacking. Calibration plots for Phe and Tyr in urine showed good linearity (R(2) > 0.96) in the concentration range 10-175 μM, and LODs for Phe and Tyr were 0.054 and 0.019 μM, respectively. RSDs for peak area and migration time for Phe and Tyr were below 7.5% and 0.75%, respectively.

Peptide mapping using capillary electrophoresis offline coupled to matrix‐assisted laser desorption ionization time of flight mass spectrometry

This article reports the results of a study carried out to evaluate the offline hyphenation of capillary zone electrophoresis with matrix-assisted lased desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) for the analysis of low-abundant complex samples, represented by the tryptic phosphorylated peptides of phosphoproteins, such as α-casein, β-casein, and fetuin. The proposed method employs a latex-coated capillary and consists in the online preconcentration of the tryptic peptides by a pH-mediated stacking method, their separation by capillary zone electrophoresis, and subsequent deposition of the separated analytes onto a MALDI target for their MS analysis. The online preconcentration method allows loading a large sample volume (∼150 nL), which is introduced into the capillary after the hydrodynamic injection of a short plug of 1.0 M ammonium hydroxide solution and is sandwiched between two plugs of the acidic background electrolyte solution (BGE) filling the capillary. The sample spotting of the separated analytes onto the MALDI target is performed either during or postseparation using an automatic spotting device connected to the exit of the separation capillary. The proposed method allows the separation and identification of multiphosphorylated peptides from other peptides and enables their identification at femtomole level with improved efficiency compared with LC approaches hyphenated to MS.