Proton magnetization relaxation in aqueous suspensions of composite silicon-iron nanoparticles for biomedical applications

Silicon-iron composite nanoparticles produced by arc-discharge plasma ablation method were characterized by scanning electron microscopy, dynamic light scattering, X-ray fluorescence diffractometry, and the effect of iron content and size of the nanoparticles on hydrogen nuclei magnetization relaxation were investigated by nuclear magnetic resonance relaxometry. It was shown that increasing in iron content during the synthesis leads to distortion of the spherical shape of the nanoparticles and increasing of their mean sizes from 140 nm to 350 nm. Nonlinear dependence of the longitudinal and transverse relaxivities from iron content was demonstrated. Increase in the iron concentration above 2.5 at. % leads to reduction of the both relaxivities, which can be explained by nonuniform distribution of iron and formation of iron containing agglomerates. It was shown that transverse and longitudinal relaxivities of the nanoparticles in their aqueous solutions inversely proportional from their hydrodynamic diameters in the range of 100 – 300 nm. The possibilities of using composite silicon-iron nanoparticles for biomedical applications are discussed.

Study on the Flexoelectricity of BST Film Multilayer Structure

Single layer and bilayer Y3+-doped Ba0.65Sr0.35TiO3 (BST) thin-film cantilever beam, of which the single BST film thickness is 500 nm, was prepared on a composite silicon substrate. The flexoelectric coefficients of both types of BSTs were measured using a low frequency vibration method. The flexoelectric coefficient of the bilayer BST film multilayer structure is 1.66 μC/m, which doubles the effective flexoelectric coefficient comparing to the single layer BST. In addition, we discussed the effective piezoelectric coefficient of the BST film multilayer structure, which can reach as much as 2.08×10-10C/N due to the scaling effect.