Magnetic-property enhancement of sized controlled cobalt-gold core-shell nanocrystals

Cobalt nanoparticles and cobalt-gold core-shell nanoparticles were synthesized via reverse-micelle microemulsion method with emphasis on size control. Cobalt nanoparticles become easily oxidized therefore coating a gold shell on cobalt nanoparticles was necessary and can effectively reduce the oxidation of Co while maintaining most of its magnetic properties. Controlling the size of nanoparticles was performed by adjusting the water to surfactant ratio of reverse micelle solution during synthesis. X-ray diffraction data was used to calculate the crystallinity percentage and percentage of phases presented in Co-Au core-shell nanoparticles. The results from transmission electron microscopy, and field emission electron microscopy combined to energy dispersive x-ray spectroscopy provide direct evidence for shell growth. The average coating layer (shell thickness) in all cases observed to be 4-5 nm. Magnetic properties of samples were investigated using a vibrating sample magnetometer before and after annealing. Magnetic properties enhanced after annealing in all cases. An increase in saturation magnetization after annealing was due to increase in cystallinity percentage. A simple method was applied to measure a totally intrinsic blocking temperature in zero field cooled-warmed (ZFC-W) curves without employing an external magnetic field. The B-field dependence temperature data of Co-Au nanoparticles before and after annealing showed an intrinsic blocking temperature of 45 and 40 K respectively

High coercivity sized controlled cobalt–gold core–shell nano-crystals prepared by reverse microemulsion

Size-controlled cobalt–gold core–shell nanoparticles were synthesized via the reverse-micelle microemulsion method. In order to control the size of the nanoparticles, the nucleation and growth process were performed within a confined space by adjusting the water to surfactant ratio of reverse micelles solution during synthesis. The crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles were calculated using X-ray diffraction data. The results from transmission electron microscopy provide direct evidence for core–shell structure nanomaterials. Magnetic properties of the samples were investigated using a vibrating sample magnetometer. The as-prepared samples showed significant coercivity at room temperature. The intrinsic blocking temperature was experimentally deduced from zero-field-cooled warmed (ZFC-W) curves by a simple method without employing an external magnetic field. The B-field dependence temperature data of Co–Au nanoparticles exhibited an intrinsic blocking temperature at 45 K. Annealing these samples at 400 °C caused an increase in particle size, crystallinity percentage and further enhanced their magnetic properties

Recording-media-related morphology and magnetic properties of crystalline CoPt3 and CoPt3-Au core-shell nanoparticles synthesized via reverse microemulsion

A comparative experimental study of the magnetic properties of CoPt3 and CoPt3/Au nanoparticles as well as a detailed study of the structural properties of the samples by X-ray diffraction, Transmission electron microscopy, and vibrating sample magnetometer is presented in this work. In addition, the effect of particle size on the structure and magnetic properties of nanoparticles prepared by microemulsion is studied. The correlation between particle size, crystallinity, and magnetization was studied as well. CoPt nanoparticles have been studied intensively over the last decade because of their increased magnetic anisotropy in the ordered phase that can be interesting for high density magnetic recording. A significant high coercivity for as-prepared CoPt3 and CoPt3-Au nanoparticles was obtained at room temperature and enhanced after annealing. The focused aim of our study is to obtain high coercivity at room temperature that follows the Curie-Weiss law. This indicates an interacting system in which the nanoparticles behave like single domain ferromagnetic materials in the particle size range of 8 to 35 nm. In addition, the interaction increases by cooling the samples to low temperature around 15 K. Temperature dependence 1/M graph was obtained to investigate the behavior of nanoparticles at low temperature and shows the best fit with Curie-Weis mode

Thermal diffusivity measurement of Cadmium Sulphide nanoparticles prepared by gamma-irradiation technique.

In this study we applied thermal lens (TL) technique to study the effect of size on thermal diffusivity of cadmium sulphide (CdS) nanofluid prepared by using γ-radiation method containing particles with different sizes. In TL experimental set up a diode laser of wavelength 514 nm and intensity stabilized He-Ne laser were used as the excitation source and the probe beam respectively, respectively. The experimental results showed that the thermal diffusivity value of CdS nanofluid increases when the of particle size increased

A simple method for measuring intrinsic blocking temperature in superparamagnetic nanomaterials

Temperature-dependent magnetic flux density (B) data, clearly exhibiting a transition temperature called intrinsic blocking temperature for some metallic samples in zero field cooled-warmed (ZFC-W) curves without employing an external magnetic field, has been obtained by a simple method. The reasons of the increase and decrease in the measured B-field at low temperature in zero magnetic-field were discussed. Co, CoPt3 and Co/Au, CoPt 3/Au core-shell nanoparticles, prepared by the reverse-micelle microemulsion method, were used as test materials. The blocking temperature was measured at a cusp of the measured magnetic field, B (produced by the sample), versus the temperature curve during warming up of the sample from a very low temperature (≤15 K) to room temperature. All the samples showed a blocking temperature at 45, 50, 40, and 42 K, respectively, for Co, CoPt3, Co/Au, and CoPt3/Au nanoparticles. A completely intrinsic behavior of the sample's magnetic moment was revealed by our method since no applied external field was used, yielding a truly spontaneous magnetization behavior

Comparison of Honey versus Polylactide Anti-Adhesion Barrier on Peritoneal Adhesion and Healing of Colon Anastomosis in Rabbits

BACKGROUND: Postoperative adhesion is still a consequence of intra-abdominal surgeries, which results in bowel obstruction and abdominopelvic pain. Bowel anastomosis as a common abdominal surgery has the incidence of leakage in up to 30% of patients that increase morbidity and mortality. Due to similar pathways of adhesion formation and wound healing, it is important to find a way to reduce adhesions and anastomosis leakage. AIM: This study was designed to compare antiadhesive as well as anastomosis healing improvement effect of honey and polylactide anti-adhesive barrier film. METHODS: Forty-five rabbits divided into three groups of honey, adhesion barrier film, and control group in an animal study. Under a similar condition, rabbits underwent resection and anastomosis of cecum under general anaesthesia. In the first group, honey was used at the anastomosis site, in the second one polylactide adhesion barrier film utilised, and the third one was the control group. Adhesion, as well as anastomosis leakage, was assessed after 21 days. Data were analysed using the Statistical Package for Social Scientists (SPSS) for Windows version 25. RESULTS: Three groups of 15 rabbits were studied. The results showed that mean peritoneal adhesion score (PAS) was lower in the honey group (1.67) in comparison to the adhesion barrier film group (3.40) and the control group (6.33). CONCLUSION: Bio-absorbable polylactide barrier has an anti-adhesion effect but is not suitable for intestinal anastomosis in rabbits. Further studies needed to evaluate these effects on human beings

Risk-taking behaviors of the Tehran city; Iranian college students in 2018

Background and aims: High-risk behaviors among different strata are one of the most severe health threats in recent years. This study aimed to investigate the frequency of high-risk behaviors among college students in Iran. Methods: This study was a cross-sectional study with 144 new students in Tehran City, Iran, performed in 2018 using random sampling. The data collection tools included questions on demographic variables and Youth Risk Behavior Survey (YRBS) questionnaire. Students completed the questionnaire. The data were analyzed using SPSS 24 and descriptive tests. Results: In this study, all students were in their first year of university. The results showed that 66% of students were girls and 34% were boys. 6.9% and 9% of students did not wear helmets when riding motorcycles or sitting in the driver’s seat, respectively. Also, threatened and beaten once with a weapon such as a knife or a stick and physically assaulted or beaten once were seen in 9% and 3.6% of students, respectively.9.7% had taken money from their parents or others once without permission. Conclusion: Based on the findings, many participants engage in high-risk behaviors that endanger their health; Therefore, designing and improving health programs and strategies is essential to reduce the risks and factors that cause high-risk behaviors

Cannabinoid receptor agonism suppresses tremor, cognition disturbances and anxiety-like behaviors in a rat model of essential tremor

Cognitive and motor disturbances are serious consequences of tremor induced by motor disorders. Despite a lack of effective clinical treatment, some potential therapeutic agents have been used to alleviate the cognitive symptoms in the animal models of tremor. In the current study, the effects of WIN55, 212-2 (WIN), a cannabinoid receptor (CBR) agonist, on harmaline-induced motor and cognitive impairments were studied. Adult rats were treated with WIN (0.5 mg/kg; i.p.) 15 min before harmaline administration (10 mg/kg; ip) after which exploratory and anxiety related behaviors, and cognitive function were assessed using open-field behavior and shuttle box tests. Rats that received harmaline only exhibited a markedly reduced number of central square entries when compared to harmaline vehicle-treated controls, whereas those treated with WIN and harmaline showed a significant increase in central square entries, compared to harmaline only treated. The passive avoidance memory impairments observed in harmaline treated rats, was reversed somewhat by administration of WIN. The neuroprotective and anxiolytic effects of WIN demonstrated in the current study can be offered cannabinoid receptor (CBR) agonism as a potential neuroprotective agent in the treatment of patients with tremor that manifest mental dysfunctions

Gamma Radiation Synthesis of Cadmium Sulfide Nanoparticles

Semiconductor Cadmium Sulfide nanocomposites capped with polyvinyl alcohol were synthesized using60Co gamma irradiation method as a reducing agent at different concentrations of cadmium and sulfur sources (1:1, 1.5:1.5, 2:2) and different doses of gamma radiation (0, 30, 60, 90, 120 KGy) at room temperature. When the solution was irradiated with γ-rays, the radiolysis of water produces many active species such as solvated electrons and they can reduce S2- ions from the sulphur source step by step which reacted with Cd2+ to generate CdS. The Formation of CdS nanoparticles can be primarily identified from the color change in the as prepared products and confirmed using X-ray powder diffraction. The optical properties of CdS nanoparticles were measured by UV- visible spectrophotometer and found that the absorbance for 1:1 concentration is at 426 nm at 30kGy, 425 nm at 60 kGy, 424nm at 90 kGy and 422 nm at 120 kGy radiation doses. The bandgap energy of CdS nanoparticles were calculated using Tauc formula.When the radiation dose increases from 30 to 120 kGy, the band gap energy increases from 2.64 to 2.71 eV for 1:1, from 2.56 to 2.64 eV for 1.5:1.5 and from 2.54 to 2.58 eV for 2:2 concentrations. The crystalline of nanoparticles were studied using XRD instrument, and found to be cubic CdS with lattice constant of a=5.8304 A°. An increase of the radiation dose improved the crystallization of CdS nanoparticles. The crystalline size of particles was estimated from the diffraction peak using Scherrer‟s equation and the size ofCdS nanocomposites exponentially decreased with the increase of the radiation dose and can be fitted with the expression of the form