Ion reduction in iron oxide and oxyhydroxide nanoparticles during ultrasonic treatment

The effect of ultrasonic treatment of iron oxide and iron oxyhydroxide nanoparticles (ferrihydrite nanoparticles synthesized by Klebsiella oxytoca microorganisms, ferrihydrite nanoparticles synthesized by a chemical method and hematite nanoparticles) is studied. Samples of nanoparticles were investigated using transmission electron microscopy, Mössbauer spectroscopy and X-ray diffraction methods. The formation of the α-Fe metal phase from nanoparticles of iron oxides and iron oxyhydroxides was detected. The metal phase is formed as a result of the reduction of iron ions during cavitation treatment. According to the experimental results, the presence of a protein or a polysaccharide component is necessary for the course of this reaction.     

New versatile polydopamine coated functionalized magnetic nanoparticles

Polydopamine coated magnetite nanoparticles are functionalized with azido groups by reaction with 4-azidobutylamine. The resulting nanoparticles allow straight forward Cu-catalyzed “click”-reaction with alkynes. In this way practically interesting functions can be tethered to the nanoparticles as exemplified by introducing biotin, glucose, proline or dansyl. The nanoparticles exhibit superparamagnetic behavior.     

Biosynthesis of tin oxide (SnO2) nanoparticles using jujube fruit for photocatalytic degradation of organic dyes

In this study, tin oxide (SnO₂) nanoparticles were synthesized via a green route using jujube fruit as a non-toxic, renewable reducing agent, and excellent stabilizer. The biosynthesized SnO₂ nanoparticles were characterized by X-ray diffraction analysis (XRD), Fourier-Transform infrared (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Moreover, the photocatalytic activity of the novel SnO₂ nanoparticles was investigated for degradation of two organic dyes which were named methylene blue (MB) and eriochrome black-T (EBT) under direct sunlight. An excellent performance was observed and about 90% and 83% of degradation efficiencies were achieved for MB and EBT, respectively. The high stability of the photocatalyst also makes SnO₂ nanoparticles easily to reuse at least four times without any remarkable loss in activity.     

Investigation of the fabric evolution and the stress-transmission behaviour of sands based on X-ray μCT images

This paper presents the use of X-ray micro-tomography (X-ray $\mu$CT) and image processing and analysis techniques to investigate the stress transmission and buckling of inter-particle contacts within a granular material. A triaxial testing of a miniature Leighton Buzzard sand (LBS) sample was carried out with full-field in-situ X-ray $\mu$CT scanning. High-spatial-resolution CT images of the sample were acquired at several loading stages of the test. Image processing and analysis techniques were used to quantify the inter-particle contact evolution (contact gain, contact loss and contact movement), fabric, contact duration and buckling of stress-transmission contacts based on the CT images. The results indicated that contact gain and loss, and contact movement played two competing roles in determining the overall fabric evolution of the sample. Contacts with a longer duration were more likely to orient in the major principal stress direction and form a stress-transmission contact network. A gradual decrease in the buckling rate of the stress-transmission contacts was observed outside of the shear band, and a relatively stable buckling rate was observed within the shear band during the shear. The results suggested that jamming occurred outside of the shear band and that unjamming occurred within the shear band.