Ammonium Hydroxide Solution Research Articles

Mechanism for formation of Hollow and Granular Silica Aerogel Microspheres from rice husk ash for drug delivery

The present work describes a method for preparation of Hollow Silica Aerogel Microspheres (HSAMs) and Granular Silica Aerogel Microparticles (GSAMs) for drug delivery, from rice husk ash (RHA), an inexpensive source of biocompatible silica. This method involves a two-step sol–gel process for preparation of wet gel microspheres using an improved sol–gel/mineral-oil emulsion (containing dual surfactants), followed by solvent exchange and aging in aqueous ethanol, to replace water in the microspheres with ethanol. It is shown that the amount and concentration of the ammonium hydroxide (NH4OH) solution added during gelation process determine if hollow or granular wet gel particles form. A mechanism for the formation of HSAMs or GSAMs is proposed and validated by experiments. The wet gel particles are subsequently dried with supercritical carbon dioxide at 150bar and 50°C to obtain HSAMs or GSAMs. HSAMs afford high loading of drugs as illustrated by loading of 0.47g ibuprofen per g of HSAM. Further, a fast release of ibuprofen from loaded HSAMs compared to pure crystalline ibuprofen and other loaded forms, indicates that HSAMs produced by the present method are good drug delivery vehicles.

Identification and functional analysis of the autofluorescent substance in Limonium bicolor salt glands

Limonium bicolor is a typical recretohalophyte with salt glands for the secretion of excess salts into the environment. We observed that L. bicolor salt glands showed obvious blue autofluorescence under UV excitation (330–380 nm). The aim of the present study was to identify and clarify a role for this autofluorescent substance in salt secretion. Sudan IV staining showed that the autofluorescent substance was localized in the cuticle of the salt glands. Moreover, the primary autofluorescent substance was identified as ferulic acid after treatment with 0.1 M ammonium hydroxide solution, alkaline and enzymatic hydrolysis. Additional experiments using two mutants exhibiting increased (fii) and decreased (fid) salt gland fluorescence indicated that the fluorescence intensity of salt glands under UV excitation was positively correlated with the content of ferulic acid in the cuticle, strongly suggesting that the primary autofluorescent substance in the salt glands was ferulic acid. Salt gland secretion was determined using leaf discs, and the results showed that the Na+ secretion rate per single salt gland was also positively correlated with the content of ferulic acid in the cuticle, suggesting that ferulic acid in the cuticle was directly involved in salt secretion of salt gland.

Silicon anisotropic etching in Triton‐mixed and isopropyl alcohol‐mixed tetramethyl ammonium hydroxide solution

The anisotropic silicon (Si) etching characteristics of Si (100) in 25 wt.% tetramethyl ammonium hydroxide (TMAH) solutions containing Triton X-100 and isopropyl alcohol (IPA) were studied. The etch rate, convex corners and roughness of the etched surface were investigated. In this reported work two central goals, a mirror-like surface finish and a high reduction of undercutting, have been achieved. The best etched result was obtained in 25 wt.% TMAH + 0.25%v/v Triton + 16%v/v IPA, which has minimum convex corner undercutting and a smooth etched surface (Ra = 1 nm). This study is useful for engineering applications where the fabrication of microstructures for high-quality devices should simultaneously contain smooth surfaces on a large area and less convex corner undercutting.

Effect of Carbon Nanotubes Surface Modification on Structure of Forcibly Ordered Films of Filled Polystyrene

The effect of surface modification of multi-walled carbon nanotubes (MWCNTs) with different modifiers on the filler dispersibility in polystyrene and the influence of the external magnetostatic field on the structure of obtained composites have been studied. The surface modification of assynthesised and oxidized carbon nanotubes was performed by treatment with hydrochloric acid or ammonia hydroxide solutions. The composite films were casted on glass plates with or without the influence of magnetostatic field at the desired directions of the magnetic lines. A combination of MWCNTs surface treatment and directed influence of the magnetostatic field was shown to be an effective route to change the structure of composites.

UV-Light Absorption and Photocatalytic Properties of Zn-Doped CeO<sub>2</sub> Nanopowders Prepared by Ultrasound Irradiation

Ceria (CeO2) nanopowders doped with various Zinc (Zn) compositions were synthesized from solution by irradiating ultrasound waves. Ultrasound waves were irradiated to aqueous/isopropanol solution of cerium nitrate and zinc nitrate mixtures. Aqueous solution of ammonium hydroxide was droped into that solution until pH becomes 10. Dried precipitates were calcinated at 100°C to form CeO2 nanopowders. X-ray Diffraction (XRD) analysis shows the CeO2 nanopowder possess fluorite cubic structure. Ultrasound irradiation resulted in nanometric powder of CeO2 with spherical in shape. The addition of Zn into CeO2 reduces the particle size and shows strong absorbance in the ultra–violet (UV) region. Moreover, the addition of 20 mol% Zn is inhibiting photocatalytic activity of CeO2 under sunlight irradiation. These results suggest that Zn-doped CeO2 is more promising for UV radiation protection with no presence photocatalytic activity.

Optimization of microwave-assisted extraction for six inorganic and organic arsenic species in chicken tissues using response surface methodology.

Response surface methodology was applied to optimize the parameters for microwave-assisted extraction of six major inorganic and organic arsenic species (As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone) from chicken tissues, followed by detection using a high-performance liquid chromatography with inductively coupled mass spectrometry detection method, which allows the simultaneous analysis of both inorganic and organic arsenic species in the extract in a single run. Effects of extraction medium, solution pH, liquid-to-solid ratio, and the temperature and time of microwave-assisted extraction on the extraction of the targeted arsenic species were studied. The optimum microwave-assisted extraction conditions were: 100 mg of chicken tissue, extracted by 5 mL of 22% v/v methanol, 90 mmol/L (NH4 )2 HPO4 , and 0.07% v/v trifluoroacetic acid (with pH adjusted to 10.0 by ammonium hydroxide solution), ramping for 10 min to 71°C, and holding for 11 min. The method has good extraction performance for total arsenic in the spiked and nonspiked chicken tissues (104.0 ± 13.8% and 91.6 ± 7.8%, respectively), except for the ones with arsenic contents close to the quantitation limits. Limits of quantitation (S/N = 10) for As(III), As(V), dimethyl arsenic acid, monomethyl arsenic acid, p-arsanilic acid, and roxarsone in chicken tissues using this method were 0.012, 0.058, 0.039, 0.061, 0.102, and 0.240 mg/kg (dry weight), respectively.

Osage Orange (Maclura pomifera L.) Seed Oil Poly(α-hydroxydibutylamine) Triglycerides: Synthesis and Characterization.

Milled Osage orange seeds (Maclura pomifera (Raf.) Schneid) were Soxhlet extracted with hexane, and portions of the extract were treated with activated carbon before solvent removal. The crude oil was winterized and degummed by centrifugation at low temperature. Decantation of the centrifugate gave an admixture of the triglycerides and free fatty acids. The free fatty acid content of the oil was removed when portions of the admixture were diluted with hexane and shaken with cold aqueous ammonium hydroxide (0.1 M) solution. The desiccant-dried organic phase was concentrated under reduced pressure to give the cleaned Osage orange triglyceride after solvent removal by rotary evaporation at 67 °C. Epoxidation of the resulting cleaned triglyceride was effected by reaction with in situ generated peroxy performic acid in H2O2. The oxirane rings of the derivatized oil were then opened using N,N-dibutylamine catalyzed by anhydrous ZnCl2 to afford the poly(α-hydroxydibutylamine) triglyceride. The purpose of this work was to derivatize and thereby stabilize this highly unsaturated tree oil for its eventual use in lubrication applications.

New methods for utilization of waste polyethylene terephthalate

New promising methods for utilizing waste polyethylene terephthalate (PET) are presented. At the first stage, partial thermal destruction of PET in an enclosure resulting in the formation of a fragile material takes place. The obtained material may be ground to a fine powder for further use as a filler. In addition, the powder of partially destructed PET reacts with alkali and ammonium hydroxide solutions resulting in the formation of corresponding terephthalate solutions, from which it is possible to obtain solid terephthalates. These terephthalates may be valuable functional materials, as well as precursors for nanodispersed oxides.

Cadmium(II) transfer using (TiOAC) ionic liquid as carrier in a smart liquid membrane technology

The transfer of cadmium(II) from acidic chloride solutions through a smart liquid membrane technology was investigated in a microporous polypropylene hollow fiber membrane contactor. The organic solution of tri-isooactylammonium chloride (TiOAC) in Exxsol D100 was used as carrier. The acidic chloride feed solution containing the metal was passed through the tube side, and the pseudo-emulsion of the organic solution and NH4OH was passed through the shell side in counter-current mode, using a unique contactor in the process. In the pseudo-emulsion based hollow fiber membrane with strip dispersion (PEHFMSD) technology, the aqueous strip solutions of ammonium hydroxide are dispersed in the organic solutions in a tank with a mixing arrangement to provide a strip dispersion. This strip dispersion circulates from the tank to the membrane module to provide constant supply of the organic solution to the membrane pores. Different hydrodynamic and chemical variables, such as variation in feed acidity, metal concentration in the feed, carrier concentration in the organic phase, variation in feed, strip and organic phase volume ratios and variation in the feed and pseudo-emulsion flows, were investigated. Mass transfer coefficients were calculated from experimental data.

Exceptionally robust and conductive superhydrophobic free-standing films of mesoporous carbon nanocapsule/polymer composite for multifunctional applications

A novel mesoporous carbon nanocapsule (MCC)/polyvinylidene fluoride (PVDF) polymer composite based free-standing film with multifunctional properties is fabricated by a facile solution approach that is appropriate for dip coating, brush-on and spray applications. The MCC/PVDF composite film exhibits superhydrophobic properties with a water contact angle of approximately 160° and a sliding angle of 5°. The films have a high thermal stability (up to 350°C in oxidative atmosphere) and are also electrically conductive (tunable from ∼10−3Sm−1 to 10−2Sm−1). The superhydrophobicity is retained even in highly corrosive acidic and basic conditions (pH 1.29–13.54, concentrated HNO3 exposure and ammonium hydroxide solution), as well in a wide humidity range (35–83%). The mesoporous carbon containers (∼100nm–1μm size) also provide an interesting platform for encapsulating a variety of functional nanomaterials and activate release, thereby adding to the multi-functionality of the superhydrophobic conductive films of exceptional environmental stability, mechanical strength (∼0.1GPa) and flexibility.

Study of Cu Bimetallic Corrosion and Its Inhibition Strategy for Cu Interconnect Application Using Micro-Pattern Corrosion Screening

Ru and other noble metals have been actively investigated for use as seedless liner/barrier materials for advanced Cu interconnect applications. Due to the lack of volatile byproducts in the reactive ion etching of Cu, the Cu interconnects are fabricated by dual damascene patterning process that involves etching a trench/via pattern into a dielectric, the blanket deposition of a diffusion barrier followed by Cu electroplating, and finally removal of Cu overburden by chemical-mechanical planarization (CMP). Since the CMP process exposes the Cu interconnect and metal barrier to the continual presence of corrosive chemicals, the resulting bimetallic corrosion between Cu and diffusion barrier metal can be detrimental to the overall production yields of integrated circuit devices. In this paper, we will present findings from a new corrosion screening metrology utilizing micro-corrosion test patterns (Cu dots, D≈130µm) to provide rapid in-situ corrosion evaluations in manufacture relevant chemical environments used to produce Cu interconnect structure. The results from Cu micro-pattern corrosion screening corroborate well with XPS and electrochemical techniques to reveal the detailed bimetallic corrosion mechanisms in specific chemical environments. For most of the CMP solutions studied to date, the Cu corrosion was found to be accelerated through an oxygen reduction reaction catalyzed by Ru. The new insights obtained from mechanistic investigation on Cu/Ru bimetallic corrosion not only help to unveil the real functions of each chemical previously masked by the complex matrix of CMP formulation, it also significantly expands the chemistry tool set that enables better corrosion inhibition strategy to protect detrimental corrosion defects of Cu interconnect with minute nanometer dimension used in advanced IC device. For example, micro-pattern corrosion screening results and electrochemical analyses revealed that 1mM pyrazole in 8 wt.% tetramethyl ammonium hydroxide (TMAH) solution could inhibit Cu corrosion more effectively than 10mM benzotriazole (BTA) in the same solution. Overall Cu corrosion rate in TMAH based highly alkaline post CMP cleaning solution is shown to be considerably reduced to <1Å/min by addition of pyrazole as corrosion inhibitor.

Fischer–Tropsch synthesis: Effect of ammonia in syngas on the Fischer–Tropsch synthesis performance of a precipitated iron catalyst

The effect of ammonia in syngas on the Fischer–Tropsch synthesis (FTS) reaction over 100Fe/5.1Si/2.0Cu/3.0K catalyst was studied at 220–270°C and 1.3MPa using a 1-L slurry phase reactor. The ammonia added in syngas originated from adding ammonia gas, ammonium hydroxide solution, or ammonium nitrate (AN) solution. A wide range of ammonia concentrations (i.e., 0.1–400ppm) was examined for several hundred hours. The Fe catalysts withdrawn at different times (i.e., after activation by carburization in CO, before and after co-feeding contaminants, and at the end of run) were characterized by ICP-OES, XRD, Mössbauer spectroscopy, and synchrotron methods (e.g., XANES, EXAFS) in order to explore possible changes in the chemical structure and phases of the Fe catalyst with time; in this way, the deactivation mechanism of the Fe catalyst by poisoning could be assessed. Adding up to 200ppmw (wt. NH3/av. Wt. feed) ammonia in syngas did not significantly deactivate the Fe catalyst or alter selectivities toward CH4, C5+, CO2, C4-olefin, and 1-C4 olefin, but increasing the ammonia level (in the AN form) to 400ppm rapidly deactivated the Fe catalyst and simultaneously changed the product selectivities. The results of ICP-OES, XRD, and Mössbauer spectroscopy did not display any evidence for the retention of a nitrogen-containing compound on the used catalyst that could explain the deactivation (e.g., adsorption, site blocking). Instead, Mössbauer spectroscopy results revealed that a significant fraction of iron carbides transformed into iron magnetite during co-feeding high concentrations of AN, suggesting that oxidation of iron carbides occurred and served as a major deactivation path in that case. Oxidation of χ-Fe5C2 to magnetite during co-feeding high concentrations of AN was further confirmed by XRD analysis and by the application of synchrotron methods (e.g., XANES, EXAFS). It is postulated that AN oxidized χ-Fe5C2 during FTS via its thermal dissociation product, HNO3. This conclusion is further supported by reaction tests with co-feeding of similar concentrations of HNO3. Additional oxidation routes of iron carbide to magnetite by HNO3 and/or by its thermal decomposition products are also considered: Fe5C2+NOx (and/or HNO3)→Fe3O4. In this study, ion chromatography detected that 50–80% HNO3 directly added or dissociated from AN eventually converted to ammonia during or after its oxidation of iron carbide, resulting from the reduction of NOx (NOx+H2+CO→NH3+CO2+N2+H2O) by H2 and/or CO.

Effects of sidewall MOS channel on performance of AlGaN/GaN FinFET

AlGaN/GaN FinFETs with various fin widths (Wfin), which have both a 2DEG channel and two sidewall MOS channels, have been fabricated by using electron-beam lithography and subsequent sidewall wet etch in tetramethyl ammonium hydroxide (TMAH) solution. The devices with wide Wfin of 150nm showed normally-on operation with threshold voltage (Vth) of −2.5 and −5.0V, respectively. The devices also exhibited broad transconductance (gm), and excellent off-state performance with very low subthreshold swing (SS). On the other hand, narrow device with Wfin of 50nm exhibited normally-off operation with Vth of 3.0V, but degraded SS due to trapping effect at the sidewall of fin.

Fast synthesis of mesoporous silica materials via simple organic compounds templated sol–gel route in the absence of hydrogen bond

As simple organic compounds that contain no hydroxyl, amino or carboxyl groups cannot assemble with the siliceous species through hydrogen bond or electrostatic force, they have not been applied as templates to prepare mesoporous silica materials before. However, in this work it was found that only if the organic compound can form homogeneous solution with ethanol and water can it successfully lead the formation of mesopores under the catalysis of 5% ammonium hydroxide (NH4OH) solution. The effects of template type, template amount and NH4OH solution concentration on the pore structure of the prepared porous silica were comprehensively studied. The pore size had no direct correlation with the molecular size of the template, but it could be easily adjusted in the range of 2.4–6.6 nm through changing the template amount. When using 5% NH4OH solution as the catalyst, the gelation time of siliceous species was ultrashort and therefore the template aggregates could be trapped in the three-dimensional SiO2 matrixes to function as the pore-forming agents. However, when the concentration of NH4OH solution was excessive high, like 15%, the gelation reaction was over intense and mesopores cannot be formed in the prepared silica. The mesoporous silica materials prepared in this new sol–gel route can be used as good supports of CO2 adsorbents. Through loading PEI into the mesopores of the silica materials, the solid amine adsorbents could be easily prepared, and they can keep remarkable CO2 adsorption ability even after 10 adsorption–desorption cycles.

Chemical bath deposition growth and characterization of zinc oxide nanostructures on plain and platinum-coated glass substrates for hydrogen peroxide gas sensor application

Growth of zinc oxide on plain and Pt-coated glass substrate via chemical bath deposition technique (CBD) were studied. Aqueous solutions of ammonium hydroxide (NH4OH) and zinc sulfate (ZnSO4) were used as the precursor substances in the synthesis. Ultraviolet-visible spectroscopy (UV-Vis) was performed to determine the energy band gap and X-ray diffraction (XRD) to examine crystallinity. Sensitivity measurements were carried out in order to examine its potential to be fabricated as hydrogen peroxide (H2O2) gas sensor. Experimental results in the sensitivity experiment show that in the presence of H2O2 gas, the resistance of ZnOincrease which can be used as the basis for H2O-2 detection. UV-Vis showed variation of energy band gap values but were all near the generally accepted value. XRD spectra further verify that ZnOwere indeed synthesized.

Determination of surface energies and acidity‐basicity numbers of protonated and deprotonated forms of poly(sulfonic acid diphenyl aniline) by inverse gas chromatography

Protonated form of poly(sulfonic acid diphenyl aniline) (p‐PSDA) was synthesized through oxidative chemical polymerization of sodium salt of diphenylamino‐4‐sulfonic acid in hydrochloric acid and then, its deprotonated form (PSDA) was obtained by neutralization with aqueous ammonium hydroxide solution. The samples were characterized by thermal analysis and Fourier Transform Infrared, Ultraviolet‐visible, 1H‐NMR spectroscopy techniques. Their dispersive surface energies as well as surface acidity and basicity were determined by inverse gas chromatography at temperatures between 313 and 353 K. The dispersive surface energy of p‐PSDA was found to be considerably lower but it increased with temperature while that of PSDA was close to those of conventional polymers and decreased slightly with temperature. According to the Schreiber's procedure, the surfaces of p‐PSDA and PSDA were found to be acidic and amphoteric, respectively. It was observed from the electron microscope images p‐PSDA chains can form self‐organized circular polydisperse micro‐sized aggregates in aqueous solutions while PSDA cannot self‐organize to form individual aggregates. POLYM. ENG. SCI., 55:1246–1254, 2015. © 2015 Society of Plastics Engineers

Sol–gel synthesis of photoactive kaolinite-titania: Effect of the preparation method and their photocatalytic properties

Supporting TiO2 on different materials is a potential strategy to improve the photochemical properties of the resulting composites. Kaolinite (K) was used as a support to synthesize a series of kaolinite-titania (K-TiO2) photocatalysts with desirable properties for decolorization of organic contaminants. Initially, TiO2 sol was formed through gelation of titanium oxychloride using ammonium hydroxide solution and subsequent peptization of the preformed gel in a low concentration of nitric acid. The sol was reacted with different concentrations of kaolinite at different pH conditions to yield K-TiO2 composites with different TiO2 compositions. The physicochemical properties of the photocatalysts were examined by XRD, FTIR, TGA, SEM-EDAX, XRF, UV–visible DRS, TEM and nitrogen gas physisorption studies analyses. XRD results revealed that through varying pH of the reaction a mixture of TiO2 crystals can be attained in the sintered samples. A simple photocatalytic experiment of the calcined photocatalysts was carried out to evaluate the decolorization of methylene blue in the presence of an artificial UV source. The obtained results were exquisitely compared to those of the ZrO2-TiO2 based composites obtained in our previous study. It was revealed that the amount of TiO2 in the composites and the calcination temperature had a profound effect on the microstructure and photocatalytic performance of the samples. Thus, the KT34-600 sample exhibited the highest activity of all due to its superior properties. This study provides a criterion for selection of precursors, synthetic routes and support suitable for the formation of metal oxides composites with desirable properties for heterogeneous catalysis.

Fluorometric sensing of ultralow As(III) concentrations using Ag doped hollow CdS/ZnS bi-layer nanoparticles.

Arsenic poisoning from drinking water has been an important global issue in recent years. Because of the high level toxicity of arsenic to human health, an easy, inexpensive, low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for the easy fluorometric determination of As(iii) ions in the aqueous phase. The hollow bi-layer structures were synthesized by a sacrificial core method using AgBr as the sacrificial core and the core was removed by dissolution in an ammonium hydroxide solution. The synthesized nanoparticles were characterized using different instrumental techniques. A good linear relationship was obtained between fluorescence quenching intensity and As(iii) concentration in the range of 0.75-22.5 μg L(-1) at neutral pH with a limit of detection as low as 0.226 μg L(-1).

Effect of a dc magnetic field on the electrical conductivity of ammonia solutions containing tungsten(VI) and rhenium(VII) ions

The effect of a dc magnetic field (60–120 mT) on the electrical conductivities of ammonia solutions containing the W(VI) and Re(VII) ions in the course of magnetic processing for 24–48 h is studied. Magnetic processing is found to increase the electrical conductivities of 7 M ammonium hydroxide solutions containing 1 g/L tungsten or rhenium by 52–58%. The electrical conductivities of the solutions in a magnetic field are shown to depend linearly on the solution temperature and the tungsten or rhenium ion concentration in a solution. High electrical conductivities are retained for a log time (up to 2000 h) after the end of the action of a magnetic field. These investigations are carried out to solve the electrochemical problems of processing of the metallic wastes of the production of tungsten and rhenium.

Robust ultrasound assisted extraction approach using dilute TMAH solutions for the speciation of mercury in fish and plant materials by cold vapour atomic absorption spectrometry (CVAAS)

A simple and robust ultrasound assisted extraction (UAE) protocol with dilute solutions of tetramethyl ammonium hydroxide (TMAH) for the speciation of mercury in fish and plant tissues was developed by CVAAS as an alternative to conventional methods.