Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile

Extended Huckel molecular orbital calculations on hydroxobridged heterotrinuclear cobalt(III) complexes

EHT calculations on heterotrinuclear cobalt(III) complexes of the type [Cu{(OH)(2)Co(L(4))}(2)](4+) where L(4) denotes (en)(2) or (NH3)(4), en = ethylenediamine and their component species have been carried out. The results regarding bonding and structure for the trinuclear complexes are compared with those for the monomer components such as [Co(en)(2)(OH)(2)](+), [Co(NH3)(4)(OH)(2)](+) and [Cu(OH)(4)](2-) are discussed

The Influence of Prenatal Yoga on Mental Health in Pregnancy During the COVID-19 Pandemic

The COVID-19 pandemic brought to light the need to monitor mental health of expecting mothers. Studies have demonstrated increased levels of stress and anxiety for new and expectant mothers during this uncertain time. Prenatal yoga has shown to be effective in improving mental health during pregnancy, but no research has evaluated the efficacy of prenatal yoga for mental health during a pandemic. The purpose of this randomized-control trial was to determine the influence of a 10-week prenatal yoga program on mental health in pregnancy during the COVID-19 pandemic. Women (n=21) were randomized to the yoga or control group. The yoga group participated in 10 weeks of prenatal yoga, while the control group maintained typical daily routines. Baseline surveys demonstrate high levels of anxiety and depression, with an average depression score of 8.33 ± 4.89 (score of 10 represents possible depression) and an average anxiety score of 39.04 ± 12.54 (score of 39 represents clinical significance). Same day surveys suggest that women feel less depressed (p=0.015) and tense (p=0.004) immediately after a yoga session. Self-esteem (p=0.016) and vigor (p=0.007) also improved after a single class. At posttest, the yoga group had lower anxiety (p=0.007) than the control group. Though not statistically significant, a similar trend was observed with depression; the control group increased (10.13 ± 3.52) and the yoga group decreased (6.00 ± 4.18). The findings of this study may provide clinicians with valuable information regarding exercise options for patients during this pandemic. Key words: Mental health, COVID-19, pregnancy, prenatal yoga, anxiety, depressio

Microwave sintering of nickel ferrite nanoparticles processed via sol-gel method

Magnetic nickel ferrite (NiFe2O4) was prepared by sol-gel process and calcined in the 2.45 GHz singlemode microwave furnace to synthesize nickel nanopowder. The sol-gel method was used for the processing of the NiFe2O4 powder because of its potential for making fine, pure and homogeneous powders. Sol-gel is a chemical method that has the possibility of synthesizing a reproducible material. Microwave energy is used for the calcining of this powder and the sintering of the NiFe2O 4 samples. Its use for calcination has the advantage of reducing the total processing time and the soak temperature. In addition to the above combination of sol-gel and microwave processing yields to nanoscale particles and a more uniform distribution of their sizes. X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and vibrating sample magnetometer were carried out to investigate structural, elemental, morphological and magnetic aspects of NiFe2O4. The results showed that the mean size and the saturation magnetization of the NiFe 2O4 nanoparticles are about 30 nm and 55.27 emu/g, respectively. This method could be used as an alternative to other chemical methods in order to obtain NiFe2O4 nanoparticles

Surface photovoltage properties and photocatalytic activities of nanocrystalline CoFe2O4 particles with porous superstructure fabricated by a modified chemical coprecipitation method

In this study, nanocrystalline CoFe2O4 particles with porous timber-like superstructure were synthesized by a modified chemical co-precipitation route with calcination temperatures of 573, 673, 773, 873, and 973 K, respectively. The structural properties of the samples were systematically investigated by X-ray powder diffraction, scanning electronic microscopy, energy-dispersive X-ray spectra, UV-Vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy techniques. The photo-induced charge separation in the samples was demonstrated by surface photovoltage (SPV) measurement. The photocatalytic performances of the CoFe 2O4 samples were comparatively studied by the degradation of 4-chlorophenol under Xe lamp irradiation. The results indicated that the sample calcined at 673 K exhibited the highest photocatalytic efficiency among the five samples. © Springer Science+Business Media B.V. 2010