Fabrication of SAPO-34 Crystals with Different Morphologies by Microwave Heating

The crystal size and shape of the silicoaluminophosphate molecular sieve SAPO-34 have been effectively controlled in the reaction system of Al₂O₃–P₂O₅–SiO₂–TEAOH–H₂O under microwave radiations. Nano sheet-like SAPO-34 crystals are obtained when using colloidal silica as the silica source. When TEOS is used as the source of silica, homogeneous SAPO-34 crystals with a particle size of about 100 nm are formed, and the morphology of the crystals changes from uniform nano particles (~100 nm) to microspheres (~1.5 μm) by varying the H₂O/Al₂O₃ molar ratio. To further investigate the morphology control of SAPO-34, the synthetic factors, such as the silica source, water content, crystallization time and aging time have been studied in detail.     

Effect of agglomeration during coprecipitation: Delayed spinellization of magnesium aluminate hydrate

Precipitation of magnesium aluminate hydrate with faster addition of ammonia at desired pH causes agglomeration. Agglomerated powder, without any further treatment, on calcination forms intermediate compounds at low temperatures (≤ 900°C). The intermediate compounds on further heat treatment (≥ 1000°C) decompose into MgO, MgAl₂O₄ and α-Al₂O₃. Effect of agglomeration and absorption of foreign ions such as Cl⁻, SO₄²⁻, and NH₄⁺ in complex compounds probably cause loss of Al³⁺ and Mg²⁺ ions during heat treatment, and stoichiometry changes. Powders prepared by continuous method with better control of process parameters than batch process yields better spinellization.     

Thermal stress fracture mode of CO2 laser cutting of aluminum nitride

A thermal stress fracture mode of material removal by laser cutting was conducted in 1-mm thick wafers of aluminum nitride (AlN) using a continuous wave CO₂ laser with a defocused beam. In this mode, a thin layer (10–20 μm) of AlN surface was melted in an oxygen environment to form aluminum oxide. Solidification of the melt layer coupled with thermal expansion mismatch generated thermal stresses that in turn created a crack along the middle path of the laser beam, resulting in material separation. Thermochemical modeling of laser heating, oxide forming, and subsequent cooling of AlN was performed to validate the formation of cracks as well as material separation through unstable crack propagation. A comparison with the conventional “evaporation/melt and blow” laser cutting method showed that the thermal stress method offers significant benefits such as improved precision, better cut quality, higher cutting speed, and lower energy losses.     

Effect of silver nanoelectrode ensembles on the electrocatalytic reduction of NO2 by zinc phthalocyanine

Ag nanoparticles anchored on mesoporous silica materials with and without zinc phthalocyanine (ZnPc) were prepared (Ag-MPS and Ag-MPS-ZnPc respectively). The morphology, structure and composition of the materials were characterized by transmission electron microscopy, X-ray diffraction, UV/vis diffuse reflectance spectra, and X-ray photoelectron spectroscopy techniques. The new materials were used for electrode modification and the nanoelectrode ensemble (NEE) behavior of Ag-MPS and Ag-MPS-ZnPc materials was semi-quantitatively evaluated by cyclic voltammetry. Further, electrocatalytic reduction of nitrite is demonstrated at these NEE.     

Obesity in prematurely born children and adolescents: follow up in pediatric clinic

Understanding associated risk for obesity is a prerequisite to develop early life interventions to arrest the increasing epidemic of metabolic syndrome and obesity among preterm born children and adolescents. A retrospective review of 160 charts was conducted to determine the associated risk of being obese during childhood and adolescent period in preterm children. Birth weight, gestational age, weight gain, demographics, maternal health, socioeconomics, and clinical factors during early neonatal life were evaluated. The number of obese children increased with age and was observed more in the adolescent population. Obese children were significantly heavier at age 24 months old compared to their peers (p = 0.001). Analysis of associated risk for maternal demographics, maternal age, maternal marital status or race, prenatal factors, maternal substance abuse or diabetes, neonatal factors, weight for gestational age or birth weight did not show any statistically significant risk for future obesity. Duration of gestational age (OR 1.6; p = 0.017) and heavier birth weight (OR 3.2; p = 0.001) were associated with risk of obesity. Among preterm born babies in the study, the highest risk of developing excessive weight during childhood and adolescent periods are babies born at more advanced gestational age. Strong positive association was found between birth weight and body weight in childhood. By 24 months old, there was a distinguished group of toddlers, who were heavier than their peers and remained with excessive weight as they got older. Primary care pediatricians should draw attention to premature babies, overweight infants and toddlers.     

Span-60-based organogels as probable matrices for transdermal/topical delivery systems

The current study describes the preparation and characterization of thermoreversible span-60 and sunflower oil (SO)-based organogels as a matrix for drug delivery. Effect of gelator concentration on the properties of the organogels was studied by physical property evaluation, stability, light microscopy, FTIR spectroscopy, XRD, thermal analysis, pH, and hemocompatibility studies. The drug release kinetics and antimicrobial efficacy of the salicylic acid loaded organogels were studied. The rate of gelation of the gels was found to be quicker in organogels with higher gelator proportions. The gels were inherently stable when stored below 25°C. The micrographs indicated the presence of needle-shaped crystals which formed aggregates resulting in the formation of three-dimensional networked structures. FTIR indicated intermolecular hydrogen bonding amongst SO and span-60 molecules responsible for the gelation. There was an increase in the crystallinity and the melting point of the organogels as the proportion of the organogelator was increased. The pH of the organogels indicated nonirritant nature of the gels, which were also found to be hemocompatible. The release of SA from organogels followed Higuchian kinetics and showed prolonged antimicrobial activity. The preliminary results indicated that the organogels may be tried as a matrix for controlled drug delivery. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Recent advancements in visible-light-assisted photocatalytic removal of aqueous pharmaceutical pollutants

Clean Technologies and Environmental Policy - Pharmaceuticals are one of the persistent emerging contaminants that are ubiquitous in the aquatic environment due to their extensive application as...     

Effect of chemical modification of a natural polysaccharide on its inhibitory action on mild steel in 15% HCl solution

Many of the synthetic corrosion inhibitors being used currently, are toxic and therefore research for developing environmentally benign corrosion inhibitors is of great importance. Inhibitors such as natural polysaccharides of plant origin are popular due to its non-toxic nature. Here, the toxicity of a natural polysaccharide, guar gum, and its modified form, cationic guar gum was studied and their inhibitory effects were investigated by gravimetric, electrochemical and surface morphology studies. Both the inhibitors are found to be effective and their adsorption on metal is in accordance with the Langmuir adsorption isotherm. Experimental results are in consonance with the results of quantum chemical calculations by density functional theory.     

Synthesis and characterization of indium phosphide films prepared by co-evaporation technique

Polycrystalline indium phosphide films were successfully deposited on glass and Si substrates by co-evaporating indium and phosphorus from appropriate crucibles. Microstructural studies indicated the average crystallite size to be ∼78 nm. X-ray diffraction pattern indicated reflections from (111), (220) and (311) planes only. The surface roughness of the films was estimated to be 30 nm and the band gap as determined from the transmittance versus wavelength traces was found to be ∼1.42 eV. The PL spectrum measured at 300 K was dominated by a strong peak located ∼1.41 eV. The intensity of this peak increased significantly when recorded at lower (10 K) temperatures and shifted towards higher energy (∼1.54 eV). XPS studies indicated two peaks ∼444.5 eV and ∼451.9 eV, corresponding to peaks of 3d_5/2 and 3d_3/2 of In 3d core while the P 2p peak at ∼128.8 eV was assigned to only P in InP. Characteristics Raman peaks for InP at ∼303 cm⁻¹ (TO) and ∼342 cm⁻¹ (LO) were observed.