Ammonium Hydroxide Concentration Research Articles

Synthesis of imidized nanoparticles containing soy oil under various reaction conditions

The imidization of poly(styrene-co-maleic anhydride) nanoparticles in presence of soy oil was studied, resulting in the formation of nanoparticles with 20–80nm diameter with a porous structure allowing to incorporate 50wt.% soy oil. The reaction efficiency strongly depends on the amount of ammonium hydroxide as imidizing agent, which ratio was varied between 1.01 and 1.60 relatively to the maleic anhydride moieties. Finally, stable aqueous dispersions are obtained with a higher solid content and somewhat higher Zetapotential compared to purely imidized nanoparticles. There are concurring reactions between imidization and coupling of the unsaturated double bonds in soy oil to the ammonolysed maleic anhydride. Therefore, a large amount of non-embedded oil was only observed when the imidization is favoured under high concentrations of ammonium hydroxide. Using spectroscopy and thermal analysis, it is concluded that a complex organized nanostructure is formed between the poly(styrene-co-maleimide) and soy oil, which results in a suppression of Tg evaluated by (temperature-modulated) differential scanning calorimetry.

Fast piezoresistive sensor and UV photodetector based on Mn-doped ZnO nanorods

A low cost hydrothermal synthesis method to synthesize Mn-doped ZnO nanorods (NRs) with controllable morphology and structure has been developed. Ammonia is used to tailor the ammonium hydroxide concentration, which provides a source of OH– for hydrolysis and precipitation during the growth instead of HMT. The morphological, chemical composition, structural, and electronic structure studies of the Mn-doped ZnO NRs show that the Mn-doped ZnO NRs have a hexagonal wurtzite ZnO structure along the c-axis and the Mn ions replace the Zn sites in the ZnO NRs matrix without any secondary phase of metallic manganese element and manganese oxides observed. The fabricated PEDOT:PSS/Zn0.85Mn0.15O Schottky diode based piezoresistive sensor and UV photodetector shows that the piezoresistive sensor has pressure sensitivity of 0.00617 kPa–1 for the pressure range from 1 kPa to 20 kP and 0.000180 kPa–1for the pressure range from 20 kPa to 320 kPa with relatively fast response time of 0.03 s and the UV photodetector has both relatively high responsivity and fast response time of 0.065 A/W and 2.75 s, respectively. The fabricated Schottky diode can be utilized as a very useful human-friendly interactive electronic device for mass/force sensor or UV photodetector in everyday living life. This developed device is very promising for small-size, low-cost and easy-to-customize application-specific requirements. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Synthesis of high capacity cathodes for lithium-ion batteries by morphology-tailored hydroxide co-precipitation

Nickel manganese hydroxide co-precipitation inside a continuous stirred tank reactor was studied with sodium hydroxide and ammonium hydroxide as the precipitation agents. The ammonium hydroxide concentration had an effect on the primary and secondary particle evolution. The two-step precipitation mechanism proposed earlier was experimentally confirmed. In cell tests, Li- and Mn-rich composite cathode materials based on the hydroxide precursors demonstrated good electrochemical performance in terms of cycle life over a wide range of lithium content.

Fast synthesis, morphology transformation, structural and optical properties of ZnO nanorods grown by seed-free hydrothermal method

A fast and low cost seed-free hydrothermal synthesis method to synthesize zinc oxide (ZnO) nanorods with controllable morphology, size and structure has been developed. Ammonia is used to react with water to tailor the ammonium hydroxide concentration, which provides a continuous source of OH− for hydrolysis and precipitation of the final products. Hence, allowing ZnO nanorods to growth on large areas of metal (Au and Ag coated glass), p-type Si and organic flexible (PEDOT: PSS) substrates. Increasing the growth time, the morphology transforms from pencil-like to hexagonal shape rod-like morphology. Within one hour the length of the ZnO nanorods has reached almost 1 µm. The optical characteristics has shown that the grown ZnO nanorods are dominated by two emission peaks, one is in the UV range centered at 381 nm and other one with relatively high intensity appears in the visible range and centered at 630 nm. While the growth duration was increased from 2 h to 6 h, the optical band gap was observed to increase from 2.8 eV to 3.24 eV, respectively. This fast and low cost method is suitable for LEDs, UV-photodetector, sensing, photocatalytic, multifunctional devices and other optoelectronic devices, which can be fabricated on any substrates, including flexible and foldable substrates.

Chemometric approach to optimize the operational parameters of ESI for the determination of contaminants of emerging concern in aqueous matrices by LC-IT-TOF-HRMS

Contaminants of emerging concern are organic compounds used in large quantities by the society for various purposes. They have shown biological activity at low concentrations, which gives great environmental relevance. The difficulty to detect and quantify contaminants of emerging concern in the environment stimulates the development of appropriate analytical methods. In this work a chemometric approach to positive and negative electrospray ionization (ESI) optimization for the simultaneous determination of contaminants of emerging concern in water samples by liquid chromatography-ion trap-time of flight-high resolution mass spectrometry (LC-IT-TOF-HRMS) was applied. Three types of phase modifiers were used: formic acid, ammonium hydroxide and formic acid/ammonium formate. The effects of operational parameters such as mobile phase modifier concentrations, mobile phase flow rate, heating block temperature and drying gas flow rate were evaluated by the 24−1 fractional factorial experimental design, resolution IV, in the screening phase and by Doehlert experimental design. Initial factorial experimental design studies indicated that the phase modifier ammonium hydroxide was more efficient compared to the other evaluated modifiers. It provided higher ion intensities to the majority of analytes. Doehlert experimental design allowed finding a region indicative of the optimum experimental conditions for most analytes. The best experimental condition observed was 3.5mM ammonium hydroxide concentration; 0.0917mL/min of mobile phase; 300°C heating block temperature; and drying gas at 200kPa. These optimized parameters resulted in decreased detection limits of the method. The optimized method was applied to the evaluation of water samples coming from the Rio Doce basin — Minas Gerais/Brazil utilizing multivariate exploratory techniques such as principal component analysis and Kohonen neural network. In this way, the use of chemometric approach showed to be a promising way to optimize the simultaneous determination of twenty-one contaminants of emerging concern in aqueous matrices by LC-IT-TOF-HRMS using ESI.

Preparation and catalytic property of modified multi-walled carbon nanotube-supported TiO2 for the transesterification of dimethyl carbonate with phenol

Modified multi-walled carbon nanotube-supported TiO2 samples were prepared and used as an efficient heterogeneous catalyst for the transesterification of dimethyl carbonate with phenol. The catalysts were characterized by X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption-desorption, and X-ray powder diffraction. The results showed that the catalyst, which was prepared using a low concentration (0.4%) of ammonium hydroxide as the precipitant instead of ionized water, had better catalytic activity, separability, and reusability properties. The effects of the TiO2 loading, amount of catalyst and reaction time on the performance of the transesterification reaction were also studied. Under the optimum reaction conditions, the conversion of phenol reached 42.5% with over 99.9% selectivity for methyl phenyl carbonate and diphenyl carbonate. The catalyst could be reused for the transesterification in four runs with only slight loss of its catalytic activity.

Effect of TS-1 treatment by tetrapropyl ammonium hydroxide on cyclohexanone ammoximation

TS-1 has been treated with different concentrations of tetrapropyl ammonium hydroxide (TPAOH), characterized by a series of techniques, and studied in cyclohexanone ammoximation. The results show that the MFI structure of TS-1 is not destroyed, while mesopores are formed in TS-1 crystals and the pore diameters increase with the TPAOH concentrations; the amount of the framework Ti species decreases slightly at low concentrations of TPAOH, but decreases appreciably at the concentrations of TPAOH above 0.0125mol/L; the activity and the selectivity of TS-1 are not affected by the treatment, but the catalyst stability is markedly increased after the TPAOH treatment. The increase of the stability is attributed to the mesopore formation. But when the pore diameters are larger than 6.51nm, the catalyst stability begins decreasing due to the appreciable damage of the framework titanium by TPAOH.

Surfactant-free synthesis of GeO(2) nanocrystals with controlled morphologies.

Germanium dioxide has many applications in the optoelectronics sector and is the subject of substantial research interest. In this contribution we report the preparation of germanium dioxide nanoparticles (NPs) of varied sizes and morphologies using a facile sol-gel methodology that requires no addition of templating agents (e.g., surfactants). Morphological control is achieved by tailoring the reaction mixture water/ethanol ratio, ammonium hydroxide concentration, time, and temperature.

Recovery of Sodium Bicarbonate from Textile Dye Bath Effluent Using Carbon Dioxide Gas

Water pollution from textile industries is caused by the disposal of brackish dye bath effluent, containing a high concentration of sodium chloride. The targeted removal of Na+ from the effluent using carbon dioxide would provide environmental benefits, both in reducing the environmental impact of disposal and in the production of valuable bicarbonate product. This paper describes a method based on the Solvay process for converting Na+ in the saline effluent to a useful product. The production of sodium bicarbonate from the effluent using carbon dioxide has been elucidated in a batch mode. The influence of various operating conditions including concentration of ammonium hydroxide, reaction temperature, carbonation time, and the flow rate of carbon dioxide gas on the bicarbonate yield was analyzed. Moreover, the efficiency of struvite precipitation in the removal of NH4+ from the resulting solution of the modified Solvay process was evaluated. The highest Na+ removal of 38% of the saline effluent and the b...

Studies on the Controlling of the Microstructural and Morphological Properties of Al Doped ZnO Thin Films Prepared by Hydrothermal Method

Al doped ZnO (AZO) thin films were prepared on ZnO coated glass substrates by hydrothermal synthesis technique using aqueous solutions containing zinc nitrate hexahydrate, ammonium hydroxide, and different sodium citrate concentrations at 60 °C for 6 h. The effects of different trisodium citrate concentrations on the microstructural, crystallinity, morphological, optical, and chemical properties of thin films were investigated. X-ray diffraction studies showed that the AZO thin films were grown as a polycrystalline wurtzite hexagonal phase with a c-axis preferred orientation and without an unwanted second phase regardless of trisodium citrate concentrations. The thickness and grain sizes of AZO thin films decreased with increasing trisodium citrate concentration. The microstructure of AZO thin films was changed from flat to needle shaped and the morphology was smoother with increasing trisodium citrate concentrations. The AZO thin films have a high transmittance in the visible region ranging from 75 to 85% and a sharp edge from 366 to 374 nm.

Influence of the reaction conditions on the thermal stability of mesoporous MCM-48 silica obtained at room temperature

The thermal stability of MCM-48 silicas synthesized at room temperature under basic conditions using cetyltrimethylammonium bromide (CTAB) as template was evaluated as a function of the reaction time, CTAB/TEOS and H2O/ethanol molar ratios and ammonium hydroxide (NH4OH) concentration in the initial gel composition. Samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analyses, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that synthesis conditions affect the structural and thermal properties of the MCM-48 silicas. These silicas exhibited a size from 200 to 500nm with spherical morphology.

Influence of variation in the concentration of ammonium hydroxide on the size of ZnO crystal obtained by Microwave Chemical Bath Deposition

Films of good crystalline quality of ZnO were successfully prepared using the microwave chemical bath deposition method at a temperature of 80 °C. Concentration of the basic precursor was varied systematically in order to obtain different degrees of acidity in the precursor solutions. Increasing the pH causes an increase in yield. This increase is reflected on the thickness of the deposit. The results of atomic force microscopy (AFM) show an increase in particle size with increasing pH in agreement with the results obtained by profilometry.

Chestnut Shell as Unexploited Source of Fermentable Sugars: Effect of Different Pretreatment Methods on Enzymatic Saccharification

Chestnut shell (CS) is an agronomic residue mainly used for extraction of antioxidants or as adsorbent of metal ions. It also contains some polysaccharide that has not been considered as potential source of fermentable sugars for biofuel production until now. In this study, the effect of different pretreatment methods on CS was evaluated in order to obtain the greatest conversion of cellulose and xylan into fermentable sugars. Hot acid impregnation, steam explosion (acid-catalysed or not), and aqueous ammonia soaking (AAS) were selected as pretreatments. The pretreated biomass was subjected to saccharification with two enzyme cocktails prepared from commercial preparations, and evaluation of the best pretreatment and enzyme cocktail was based on the yield of fermentable sugars produced. As AAS provided the best result after preliminary experiments, enhancement of sugar production was attempted by changing the concentrations of ammonium hydroxide, enzymes, and CS. The optimal pretreatment condition was 10 % ammonium hydroxide, 70 °C, 22 h with CS at 5 % solid loading. After saccharification of the pretreated CS for 72 h at 50 °C and pH 5.0 with a cocktail containing cellulase (Accellerase 1500), beta-glucosidase (Accellerase BG), and xylanase (Accellerase XY), glucose and xylose yields were 67.8 and 92.7 %, respectively.

Environmentally friendly electroless plating for Ag/TiO2-coated core–shell magnetic particles using ultrasonic treatment

In this work, high-reflectance brilliant white color magnetic microspheres comprising a Fe/TiO2/Ag core–shell structure with a continuous, uniform compact silver layer were successfully fabricated by TiO2-assisted electroless plating in a simple and eco-friendly method. The coating procedure for TiO2 and Ag involved a sol–gel reaction and electroless plating with ultrasound treatment. The electroless plating step was carried out in an eco-friendly manner in a single process without environmentally toxic additives. The TiO2 layer was used as a modification layer between the Fe microspheres and the silver layer to improve adhesion. A continuous and compact silver layer could be formed with a high degree of morphological control by introducing ultrasonication and adjusting the ammonium hydroxide concentration.

An improved Stöber method towards uniform and monodisperse Fe3O4@C nanospheres

Significant progress has recently been made in the synthesis of Fe3O4@C nanospheres with uniform, monodisperse and tunable carbon shells. Fe3O4@C nanospheres were obtained by directly carbonizing Fe3O4@polymer which was synthesized by a versatile and economical Stober method with resorcinol and formaldehyde as precursors. The synthesis conditions in the formation of Fe3O4@polymer were systematically investigated. It was found that the yield of the Fe3O4@polymer is highly influenced by the concentration of ammonium hydroxide, and the monodispersity is mainly affected by the concentration of ammonium hydroxide and the citrate group sites outside the surfaces of the Fe3O4 nanospheres. Interestingly, carbonization of Fe3O4@polymer at high temperature makes the grain sizes of Fe3O4 in Fe3O4@C samples larger than those in the Fe3O4 sample, which makes the saturation magnetization value for the Fe3O4@C samples higher than those of common obtained materials. The adsorption performance of Fe3O4@C for anthracene was tested both in water and in cyclohexane solution; it shows fast adsorption rates (about 1 h to reach equilibrium in water and 3 h in cyclohexane solution) and high adsorption capacities (31.5 mg g−1 in water and 2 mg g−1 in cyclohexane solution), which are ascribed to its high uniformity and monodispersity. These make Fe3O4@C an ideal adsorption and enrichment material, especially for polycyclic aromatic hydrocarbons in water and in organic solvents.

Polyester metallisation with electroless silver plating process

In this paper, electroless silver plating process for polyester was reported. The electroless silver plating is basically divided into four stages including pre-cleaning, sensitisation, electroless silver deposition and post-treatment. As the electroless silver plating stage is the key stage in affecting the brilliant appearance and various functional properties such as conductivity and ultra-violet protection, we will study the effect of process variables, i.e. amount of silver nitrate (AgNO3), concentration of ammonium hydroxide (NH4OH), concentration of sodium hydroxide (NaOH) and process temperature, using increased amount of silver in fabric surface as an indicator, for optimising the electroless silver plating process for possible industrial application. Experimental results revealed that amount of silver nitrate (AgNO3)=1.77×10−3 mole; concentration of ammonium hydroxide (NH4OH)=6.25 %; concentration of sodium hydroxide (NaOH)=0.008 g/ml and process temperature=25 °C can give the best electroless silver plating for polyester fabric. The surface characteristics of the electroless silver-plated polyester fabric were evaluated by scanning electron microscope, X-ray photoelectron spectroscopy and X-ray diffraction analysis. Meanwhile, the performance properties of the electroless silver-plated polyester fabric were measured by CIE L*, a* and b* values, conductivity as well as ultraviolet protection. The experimental results would be discussed thoroughly in this paper.

Selective Enrichment of Glycopeptides Using Aluminum Oxide

Protein glycosylation is significantly associated with cells cycle, immune regulation, cells recognition and cells adhesion. Aberrant glycosylation expression is involved in many diseases, such as rheumatoid arthritis, cancer, and chronic obstructive pulmonary disease. Thus, characterization of the protein glycosylation is very important to understand the life process. However, detection of glycopeptides is difficult by mass spectrometry because of the low concentration in complex sample and the suppressed signal by non-glycopeptides. Therefore, it is essential to explore an effective technique for glycopeptide enrichment. In this study, an alumina based-materials was used to selectively enrich glycopeptides. Firstly, we investigated the retention mechanism by changing the concentration of acetonitrile (ACN). With the decreased concentration of ACN, it was found that peptides were eluted according to their hydrophilicity. Moreover, most of the non-glycopeptides were eluted earlier than the glycopeptides in the high concentration of ACN fraction and the glycopeptides were found in the low concentration of ACN fraction. This result proved that hydrophilic interaction is one of the retention mechanisms for peptides retained by alumina. Secondly, we investigated the retention mechanism by changing the concentration of ammonium hydroxide. ACN were fixed at a high concentration and peptides were subsequently eluted with different concentration of ammonium hydroxide solution. At a low concentration of ammonium hydroxide solution, the peptides were no found. But at a high concentration of ammonium hydroxide solution, the glycopeptides and non-glycopeptides were eluted simultaneously. This proved that the ligand exchange is also one of the retention mechanisms, where the retention of the glycopeptides and non-glycopeptides showed no different under this mechanism. Based on the above mentioned results, the enrichment condition was optimized under the model of solid-phase extraction. High concentration of ACN mixed with a certain concentration of ammonium hydroxide solution as loading buffer and low concentration of ACN mixed with a certain concentration of ammonium hydroxide solution as elution buffer. The number of glycopeptides enriched by alumina were compared with glycopeptides before enrichment and enriched by Sepharose. In the tryptic HRP digest, 7 glycopeptides were found before enrichment, 16 glycopeptides were found by alumina and 14 glycopeptides were found by Sepharose. In the tryptic IgG digest, 2 glycopeptides were found before enrichment, 12 glycopeptides were found by alumina and 4 glycopeptides were found by Sepharose. In conclusion, alumina based-method used to enrich glycopeptides has high selection and wide coverage.

Facile, Green Synthesis of Large Single Crystal Copper Micro and Nanoparticles with Ascorbic Acid and Gum Arabic

Large single crystal colloidal copper particles with diameters between 0.5 - 2 μm were created using a green synthesis process. The process used ascorbic acid to reduce Schweizer’s reagent created in situ using copper salts in the presence of various concentrations of gum arabic. The Schweizer’s reagents were created by varying the concentrations of ammonium hydroxide and copper nitrate solutions, copper hydroxide, or copper sulfate. The pH of the solution was controlled by the addition of ascorbic acid. Particle formation was favored at high temperature using copper sulfate at pH values ranging from 7.5 to 9, while the optimal formation occurred at a pH value of 8.5. At high concentrations, copper particle formation was found to occur from the aggregation of smaller particles which continued to nucleate once aggregated, and this resulted in the creation of globular particles and large aggregates of micron-sized particles. The addition of gum arabic resulted in the creation of large single crystal particles that did not aggregate. SEM was used to observe the effect of increasing gum arabic concentrations and EDX was used to confirm the elemental purity of the particles.

Effects of aminated carbon molecular sieves on breakthrough curve behavior in CO2/CH4 separation

In this study, the breakthrough curve behaviors of aminated carbon molecular sieves (CMSs) were investigated for a CO2/CH4 mixed gas, and the selective separation of CO2 was demonstrated. Nitrogen functional groups were effectively introduced onto the surfaces of the a-CMSs, and they attached themselves to the pores of the CMSs as the ammonium hydroxide concentration was increased. Nitrogen functional groups on the surfaces of the aminated CMSs, such as NH2 and CN, played an important role in guiding CO2 into the micropores via the attractive forces felt by the electrons in the CO2 molecules.

Synthesis of hollow silica particles with tunable size, shell thickness, and morphology

We herein present a simple and effective method to control the particle size, shell thickness, and morphology of hollow silica particles (HSPs). To synthesize the HSPs, polystyrene (PS) particles were employed as a sacrificial template. Size tuning of the HSPs could therefore be achieved by using PS particles of varying sizes. The size of the PS particles was easily controlled by modulation of the monomer content used in the particle synthesis. Varying amounts of TEOS and ammonium hydroxide were systematically added to the system in order to modify the shell thickness and morphology of the desired HSPs. The results indicated that the effects of TEOS and ammonium hydroxide concentrations on the HSP shell thicknesses were similar whereas the effects on morphologies differed significantly.