Presence Of NH4OH Research Articles

Low Temperature Processing of Iron Oxide Nanoflakes from Red Mud Extract toward Favorable De-arsenification of Water.

Iron oxide (α-Fe2O3) was synthesized from red mud extract followed by hydrothermal reaction at 150 °C/6-24 h in the presence of NH4OH. The crystallinity of α-Fe2O3 increased with reaction time as confirmed by X-ray Diffraction, while Fourier transform infrared spectroscopy and Raman illustrate the symmetric stretching vibration of the Fe-O bond in α-Fe2O3. The X-ray photoelectron spectroscopic analysis shows O 1s spectra at 530.6, 531.2, and 532 eV, signifying the lattice oxygen in Fe-O, surface oxygen defects, and oxygen in adsorbed hydroxyl groups, respectively. The morphology of α-Fe2O3 nanoflakes was noticed from field emission scanning electron microscopy and transmission electron microscopy. The developed particles reveal the BET surface area in the range of 136-347 m2/g. The maximum As(V) adsorption capacity of 32-41 mg/g was obtained for adsorbent dose of 0.25 g/L. The arsenic level could be lowered down to 2-3 μg/L (<10 μg/L as per WHO's limit) with contaminated real water (64 μg/L) using 0.25 g/L of sample dose within 5 min of adsorption.

Preparation of carbon dots-embedded fluorescent carboxymethyl cellulose hydrogel for anticounterfeiting applications

Fluorescent inks have been emerged as a desirable encoding technique to enhance anticounterfeiting printing of commercial goods. However, significant drawbacks with fluorescent inks, such as poor durability, low efficiency, and high cost. Herein, we describe the preparation of a self-healing authentication ink based on carboxymethyl cellulose (CMC) hydrogel immobilized with nitrogen-doped carbon dots (NCD) nanoparticles (NPs) for cutting-edge anticounterfeiting applications. Security inks that self-heal are very durable. Under ambient conditions, the prepared NCD@CMC hydrogel could self-heal with a high healing efficiency. It might stick to diverse surfaces such as plastic, glass and paper sheets. The self-healing composite ink demonstrated outstanding photostability under UV light. Straightforward and environmentally friendly method was applied on the agricultural waste of rice straw toward the production of NCD using hydrothermal carbonization in an aqueous medium, and in the presence of NH4OH as an inexpensive passivating agent. The quantum yield (QY) for NCD reached 24.09 %. Various concentrations of NCD NPs were employed to produce self-healable nanocomposite inks with a variety of emission properties. Stamping homogeneous films onto paper surfaces produced a transparent layer. The CIE Lab and emission spectra of prints independently verified the capability of NCD nanocomposite inks to vary their color to blue under UV illumination. To measure the particle diameter of the prepared NCD, their morphological characteristics were examined by transmission electron microscopy (TEM) to indicate diameters of 10–25 nm. Utilizing various analytical techniques, the morphology and chemical composition of the fluorescent prints were examined. We examined the mechanical qualities of the stamped papers as well as the rheological characteristics of the ink hydrogel. Due to their colorless appearance, the excitation band of the printed films was peaked at 364 nm, while their emission was peaked at 465 nm. The current smart ink holds high potential for numerous applications like smart packaging and authentication, and shows great promise as a practical and mass production approach for easily creating anticounterfeiting stamps.

Friedel-Crafts acylation reaction over hierarchical Y zeolite modified through surfactant mediated technology

Friedel-Crafts acylation reaction was studied under mild conditions using hierarchical HY zeolite samples prepared through surfactant mediated technology, in the presence of NH4OH, using CTAB or DTAB as surfactants and changing the duration of treatment from 6 to 48 h. The materials were characterized by powder X-ray diffraction, low temperature N2 adsorption isotherms, SEM microscopy and pyridine adsorption followed by FTIR. The catalytic behaviour was studied in the acylation of furan by acetic anhydride. The catalytic results reflect the role of the duration of the treatment as well as the surfactant molecule used. As the time of treatment increases, the enlargement of the pores leads to an increase of the rate constant and turnover frequency (TOF), except for sample modified during longer time, 48 h, due to the occurrence of secondary reactions that produce larger products or reaction intermediates that become trapped inside the pores. The role of the surfactant molecule is also relevant since the sample modified in the presence of the larger surfactant molecule, CTAB, a significant increase in product yield and rate constant is obtained when compared with the sample prepared in the same conditions using DTAB. However, in that case, by prolonging the treatment a substantial decrease in the same parameters occurs due to the occurrence of deactivation phenomena, pointing out that the optimized modification of porosity needs to be customized according to the needs of each catalytic system.

Synthesis and characterization of ultrasmall Cu2O nanoparticles on silica nanoparticles surface

The hybrid structure of SiO2-Cu2O nanocomposite was prepared by synthesizing ultrasmall cuprous oxide nanoparticles on the surface of silica nanoparticles. The spherical shaped silica nanoparticles were acted as seeds for the continuous deposition of Cu2O NPs on the surface of SiO2. First, the well-known ammonia catalyzed Stober method was utilized for the synthesis of SiO2 NPs. Then the SiO2-Cu2O nanocomposite was synthesized by reacting SiO2 NPs with copper sulfate solution in the presence of NH4OH and hydrazine monohydrate. The structural, morphological, and elemental analyses have been carried out using XRD, FTIR, FESEM, UV–Vis Spectrometer, and XPS. The UV–Visible absorption peak was observed around 465 nm. XRD data revealed the formation of the FCC phase of Cu2O NPs on silica nanoparticles. The binding energies correspond to Cu2p3/2 and Cu2p1/2 were in good agreement with the reported data.

A Novel Poly(vinyl alcohol) Post-precipitation Template Synthesis and Property Tuning of Photoactive Mesoporous Nano-TiO2

For the first time, a facile method is introduced to obtain ultrathin, mesoporous TiO2 nanosheets by the alkali precipitation of aqueous TiCl3 in the presence of NH4OH, and in-situ templating with polyvinyl alcohol (PVA). The synthesized titania have been characterized by N2 adsorption-desorption measurements, x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and ultraviolet-visible (UV-vis) spectroscopy. The obtained titania were hexagonal-like, detached, non-agglomerated, polydispersed, sub-20 nm nanodiscs. Unlike in doping methods, their surface area and pore volumes of can easily be tailored devoid of any wavelength shift, by simply tuning the amount of the template. Accordingly, their aggregation as microspheres can successfully be controlled by the templating step. The remarkable photoactivity of these nanoscopic materials has been confirmed by the degradation of aqueous methyl orange.

Recyclable Aggregates of Mesoporous Titania Synthesized by Thermal Treatment of Amorphous or Peptized Precursors.

Recyclable aggregates of mesoporous titania with different anatase–rutile ratios have been prepared by thermal treatments of either amorphous or peptized precursors. These last two have been obtained by hydrolysis of either Ti(OC2H5)4 or of Ti(OC2H5)4 in mixture with 5 mol % Zr(OC3H7)4 at room temperature in the presence of NH4OH as a catalyzing agent. The anatase–rutile ratio, the recyclable aggregates of the nano-sized particles, the mesoporosity, the surface area and the crystallinity of the resulting crystallized products of titania can be controlled by the synthesis parameters including: concentration of ammonia catalyst, stirring time and concentration of the peptizing HNO3, drying method of peptized precursors, calcination temperature, and finally the ramp rate up to the titania crystallization temperature. A broad range of synthesis parameters control the crystal sizes of titania particles produced. This allows catalyst preparation with very different crystal size, surface area, anatase to rutile crystal ratio and various mesoporous structures. Drying by lyophilization of precursors reduce the aggregation of the primary particles giving micro-/macroporous structures.

Analysis of growth kinetics and impact of NH3 on the morphology evolution of hexagonal-prism shaped Y4O(OH)9NO3/Y2O3 single crystals

The effect of NH3 on the morphology evolution of single crystalline hexagonal-prism like Y4O(OH)9NO3 and Y2O3 has been systematically investigated, as a function of reaction time, by using a combination of powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rational control over the morphology has been achieved by the choice of suitable electrolytes like NaNO3, KNO3, NH4NO3, KCl and NH4Cl in the presence of NH4OH. We report that the cross-sectional geometry of hydrothermally grown one-dimensional Y4O(OH)9NO3 crystals can be tuned from spherical to hexagonal-prism like shape by introducing a particular reagent like NH4NO3 in the presence of NH4OH. An ‘oriented attachment’ mediated growth process takes place along with the ‘dissolution-recrystallization’ route which eventually resulted in the generation of the single crystals with hexagonal-prism like morphology.

Morphology control of silica/poly(methyl methacrylate-co-styrene) hybrid nanoparticles via multiple-miniemulsion approach

AbstractAn appropriate approach has been used for the preparation of silica/P(MMA-co-St) hybrid nanoparticles through converting previously prepared inverse miniemulsions into a direct miniemulsion and consequently, using the droplet nucleation polymerization technique. In the early stage of the procedure, silica particles were synthesized from TEOS in the presence of NH4OH or HCl as a catalyst through a base or acid-catalyzed sol-gel process. TEOS, ethanol and tirmethoxyvinylsilan were mixed in MMA:St (50:50) to create the inverse miniemulsion I, similarly CTAB, NH4OH/HCl and distilled water were dispersed into MMA:St (50:50) and called inverse miniemulsion II. Then, the two mentioned inverse miniemulsions were emulsified in water to achieve direct miniemulsion. The nature of the catalyst and TEOS concentration varied, for the aims of investigation, their effect on the morphology and size of hybrid nanoparticles. This route provided a unique process for silica/polymer hybrid nanoparticles production, avoiding organic solvents. Transmission electron microscopy micrographs revealed that, the morphology of the hybrid nanoparticles can be controlled by the nature of the catalyst.

ChemInform Abstract: Crystal Structure of NH4[La(SO4)2(H2O)

AbstractCrystals of the title compound are prepared by hydrothermal reaction of La2O3, 37 wt% H2SO4, and 3‐aminobenzoic acid in presence of NH4OH (autoclave, 433 K, 3 d) followed by slow solvent evaporation.

Selective band gap manipulation of graphene oxide by its reduction with mild reagents

Graphene oxide (GO) can be used as an electron acceptor for polymeric solar cells but still band gap matching for electron donor and acceptor demands more study. The generation of the exciton in such materials is intimately related to the optical band gap. However, exciton dissociation is related to transport band gap that controls the device performance, particularly the open circuit voltage and short circuit current. Therefore, the modulation of the optical gap is useful because it results into tuning of the transport gap. The interest of the present work is to study the reduction of graphene oxide (GO) at room temperature, using environmental friendly reagents like glucose, fructose and ascorbic acid for the modulation of a band gap. It has been found that glucose and fructose function effectively only in presence of NH4OH. Although ascorbic acid can reduce GO alone, NH4OH speeds up the reaction. The optical band gap of GO can be reduced and tuned effectively from 2.7eV to 1.15eV.

Polyethyleneimine-mediated synthesis of superparamagnetic iron oxide nanoparticles with enhanced sensitivity in T2 magnetic resonance imaging

The development of iron oxide nanoparticles (IONPs) with enhanced r2 relaxivity is important for achieving greater sensitivity in in vivo magnetic resonance (MR) imaging. In this study, it was considered that polyethyleneimine (PEI) could play a role in varying the particle and cluster sizes in IONP synthesis, leading to different r2 relaxivities. To demonstrate this, superparamagnetic IONPs were synthesised in the presence of NH4OH and PEI using a co-precipitation method. PEI acted as an active stabiliser during IONP synthesis, and therefore the particle size, hydrodynamic cluster size, coating layer thickness, saturation magnetisation, and r2 relaxivity were all strongly influenced by the PEI concentration. Monodispersed IONPs with a mean hydrodynamic cluster size of 14.4nm were synthesised at a PEI concentration of 0.05wt% and in this case, the r2 relaxivity was increased up to 227.6mM−1s−1. This confirmed the viability of PEI-mediated synthesis as a means of controlling the particle/cluster size and enhancing the r2 relaxivity. The PEI–IONPs exhibited no significant cytotoxicity up to 132ppm. Rapid and strong uptake of PEI–IONPs was detected in rat liver by in vivo MR imaging. The superparamagnetic PEI–IONPs prepared in this study are considered to be sufficiently sensitive for use as MR imaging contrast agents, which can be used as parent particles for further functional modification.

Dithiocarbamates as Selective Ligands for Polarographic Study of Manganese(II) at DME

Two new ligands, ammonium 2,6-dimethyl morpholine dithiocarbamate (ADMM- DTC) and ammonium 3-methyl piperdine dithiocarbamate (AMP-DTC) were synthesized in the laboratory. The method was based on chelation of manganese(II) with ADMM-DTC/AMP-DTC in the presence of NH4OH at pH 6.2 and 6.8 to produce catalytic hydrogen currents at -0.72 V and -0.62 V vs. SCE respectively and prior detected by D.C poarography. Optimized polarographic conditions were established by studying effect of pH, supporting electrolyte (NH4Cl), ligand and metal ion concentrations and effect of adverse ions on peak height to improve the sensitivity, selectivity and detection limits of the present method. This technique is successfully applied for the analysis of manganese(II) in different matrices with recoveries ranging from 97 - 99% and the results obtained were comparable with the differential pulse polarography (DPP).

Self-assembly of nanostructures obtained in a microwave-assisted oxidative polymerization of aniline

For the first time, microwave assisted aniline oxidative polymerization is performed in the presence of acetic acid (CH3COOH) and ammonium hydroxide (NH4OH) at different microwave power levels. The reaction system is kept at constant temperature of 24±1°C. The products are investigated by Fourier Transform Infrared Spectroscopy (FTIR), Raman, solid-state Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies. EPR signals in polyaniline (PANI) originate from the polarons formed upon protonation and doping by acid. The microwave radiation causes an increase in the spin concentration which is slightly more evident for 8 W than for 93 W. The morphol- ogy is investigated by using scanning electron microscopy (SEM). SEM micrographs revealed the formation of nanorods (in the presence of CH3COOH) and nanospheres (in the presence of NH4OH). FTIR, Raman and solid-state NMR spectro- scopies indicate the presence of PANI and aniline oligomers. X-ray Diffraction (XRD) measurements showed the presence of well-ordered structures.

Sensitive Determination of Nickel (II) using Catalytic Hydrogen Wave in the Presence of Dithiocarbamates at DME

Two new ligands, ammonium 2,6-dimethylmorpholine dithiocarbamate and ammonium 3-methylpiperidine dithiocarbamate were synthesized for the determination of nickel (II) in various environmental samples. The method was based on chelation of nickel (II) with ADMM-DTC/AMP-DTC in presence of NH4OH at pH 6.4 to produce catalytic hydrogen currents at -1.30V and -1.41 V vs SCE respectively and prior detected by DC polarography at Dropping Mercury Electrode (DME). Optimized polarographic conditions were established by studying effect of pH, supporting electrolyte, ligand and metal ion concentrations and effect of adverse ions on peak height to improve the sensitivity, selectivity and detection limits of the present method. The present technique was successfully applied for the analysis of nickel (II) in different matrices with recoveries ranging from 97.00 - 99.00% and the results obtained were comparable with the differential pulse polarography.

Green Synthetic Route For The Size Controlled Synthesis Of Biocompatible gold Nanoparticles Using Aqueous Extract Of Garlic (Allium Sativum)

A green synthetic approach for the highly stable, size controlled synthesis of gold nanoparticles is being described. The study explores the use of aqueous extract of garlic cloves as reducing/stabilizing agent for the synthesis of gold nanoparticles. The synthesis is achieved by heating the mixture of aqueous garlic extract and HAuCl4 at 95oC in water bath at pH-10 for 2 hrs. The formation of gold nanoparticles was confirmed from the appearance of pink color and an absorption maximum at 530 nm. Further, extract concentration and type of alkali (NH4OH/NaOH) has been varied to tune the size of nanoparticles. The size of the synthesized gold nanoparticles was found to decrease (56.5 ± 13.6 to 24.7 ± 8.2) with increasing extract concentration (0.5%-1.0%) in the presence of NH4OH. In the presence of NaOH, the synthesis time was reduced to 20 min, with an average particle size of 5.5 ± 2.7. Transmission electron microscopy analysis indicated that non-aggregated gold nanoparticles of various sizes could be synthesized by simple change in reaction conditions. The synthesized gold nanoparticles were found to be pure face centered cubic crystals as suggested by selected area electron diffraction and X-ray diffraction patterns. Fourier transform infrared spectroscopy revealed possible role of S-allyl-cysteine as the major component responsible for reduction of Au to Au and protein/amino acids as stabilizing agents. The gold nanoparticles were found to have remarkable in vitro stability: showed no sign of aggregation at room temperature storage for a long time (more than 6 months), could resist aggregation in aqueous media with high concentrations of NaCl, in various buffers including: cysteine, histidine, bovine serum albumin and at host of pH ranges. Further, cytotoxicity evaluations on S. cerevisiae have shown non-toxic nature of the synthesized gold nanoparticles up to 100 μM of concentration as assessed by well diffusion and inhibition of colony forming efficiency assay. Ease in size control, high stability and biocompatible nature of garlic extract reduced, stabilized gold nanoparticles suggests that they could be potential candidates for drug delivery applications. Copyright © 2013 VBRI press.

Single-Layer Silica Anti-Reflective Films Modified with Polytetramethylene Glycol

Single-layer silica films modified with polytetramethylene glycol (PTMEG) were prepared via sol-gel process in the presence of NH4OH as catalyst. Compared with the pure SiO2 coating, the hybrid films possessed higher lased-induced damage threshold (LDT). The characterization results from AFM and TEM indicated that the introduction of PTMEG molecules changes the structure of the colloidal silica matrix, which directly resulted in the improvement of the transparency and LDT.

Microcapsules of alginate/chitosan containing magnetic nanoparticles for controlled release of insulin

The challenge of this work was to investigate the potential of alginate/chitosan beads containing magnetite nanoparticles as a drug delivery system. The insulin beads were prepared by dripping a solution of sodium alginate containing insulin into a CaCl 2 solution. Magnetite nanoparticles of 5 nm mean size were synthesized inside the alginate egg-box structure by co-precipitation of Fe(III) and Fe(II) in the presence of NH 4OH. Quantitative analysis revealed that insulin encapsulation depends on the initial protein content and 35% of insulin was entrapped by alginate beads for a protein concentration of 10 wt%. It was verified that approximately 50% of the insulin was released to Milli-Q water in 800 h release experiments. The application of oscillating magnetic field increased three fold the insulin release. The results suggest that the alginate/chitosan system containing magnetite nanoparticles is a promising system for clinical applications of controlled release of insulin in the presence of an oscillating magnetic field in a subcutaneous implant approach.

Ultrasonochemical-assisted fabrication and evaporation- induced self-assembly (EISA) of POSS-SiO2 @Ag core/ABA triblock copolymer nanocomposite film

Poly(ethylene glycol)-octafunctionalized polyhedral oligomeric silsesquioxane (POSS) (Mn = 5576.6 g/mol) alloying agent stabilized amphiphilic [email protected] metalloid nanocomposite blended with a triblock copolymer poly(p-dioxanone-co-caprolactone)-block-poly(ethylene oxide)-block-poly(p-dioxanone-co-caprolactone) (POSS-SiO2@Ag/PPDO-co-PCL-b-PEG-b-PPDO-co-PCL) has been synthesized in both water and in organic medium utilizing ultrasonochemical reaction. The POSS stabilized pre-made metalloid was successfully dispersed in amphiphilic PPDO-co-PCL-b-PEG-b-PPDO-co-PCL (ABA) triblock copolymer matrix of molecular weight 45.9 × 104 g/mol. The mechanism of synthesis of high concentration of SiO2@Ag nanocomposite from TEOS/AgNO3 (in the presence of NH4OH as catalyst/NaBH4 as reductant) nonmetal/metal precursors and the successful EISA of POSS-SiO2@Ag/ABA nanocomposite into films has been discussed. The successful synthesis of metalloid nanocomposite was morphologically accessed by field emission-scanning electron microscopy, transmission electron microscopy and atomic force microscopy. Surface plasmon resonance was ensured from UV–visible spectral analysis. Identity and the crystallinity of as prepared nanocomposite were studied by X-ray diffractometer. Structural and luminescence properties of the nanocomposite were examined by Fourier transform infrared spectroscopy and photoluminescence. Thermogravimetric analysis was carried out to study the thermal stability of the resulting hybrid nanocomposite. The resultant inorganic–organic nanocomposite can be easily suspended in water and would be useful in variety of applications. POLYM. COMPOS., 31:1620–1627, 2010. © 2009 Society of Plastics Engineers

Facile synthesis of PEG–silica hybrid particles using one-step sol–gel reaction in aqueous solution

A facile synthetic method for silica–PEG hybrid particles using one-step sol–gel reaction in aqueous solution is designed in this study. The preparation process of highly monodispersed hybrid silica spheres using organosilane molecules is applied to the synthetic method, which contains the self-hydrolysis step of poly(ethylene glycol) methyl ether-3-(triethoxysilyl)propyl isocyanate (PEGME-IPTES) monomers at high temperature of 80 °C for 2 days. Compared to the general sol–gel method and the sequential emulsion technique, our method is very facile and simple because (1) it just needs polymer–silane monomers without other silica sources and organic agents and (2) the reaction occurs in aqueous solutions. The size of particles is varied from 0.42 to 1.79 μm, depending on the concentration of PEGME-IPTES precursor in the presence of NH 4OH. Also, hybrid particles contain maximum 60 wt.% PEG polymer and have the surface area of 7.5 m 2 g −1. Thermal stability of PEG polymer in hybrid particles largely increases compared with free PEG polymer and PEG polymer in PEG-grafted silica particles.

Removal of organic pollutants from aqueous solutions by adsorbents prepared from an agroalimentary by-product

Two series of crosslinked starch polymers were tested for their ability to adsorb organic pollutants in aqueous solutions. The polymers were prepared by a crosslinking reaction of starch-enriched flour using epichlorohydrin as the crosslinking agent, without and in the presence of NH 4OH. These polymers were used as sorbent materials for the removal of phenolic derivatives from wastewater. The influence of several parameters (kinetics, pH and polymer structure) on the sorption capacity was evaluated using the batch and the open column methods. Results of adsorption experiments showed that the starch-based materials exhibited high sorption capacities toward phenolic derivatives. The study of the kinetics of pollutant uptake revealed that the adsorbents presented a relatively fast rate of adsorption. The experimental data were examined using the Langmuir and Freundlich models and it was found that the Freundlich model appeared to fit the isotherm data better than the Langmuir model.