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Although impurity doping of nanocrystals is essential in controlling their physical properties for various applications, the doping mechanism of ultrasmall, colloidal II–VI semiconductor nanocrystals, corresponding to the initial stages of growth, is not yet understood. In this study the concentrations of Mn2+ ions in the core, on the surface, and as an agglomerated separate phase in 2.9 nm cubic ZnS nanocrystals, prepared by a surfactant-assisted liquid–liquid synthesis within 20 to 20 000 ppm nominal impurity concentration range, have been determined by quantitative multifrequency electron paramagnetic resonance. The unexpected strong decrease in the core doping efficiency with the nominal concentration increase, in contrast to the small variation of the doping efficiency for the surface-bound Mn2+ ions, and the sizable core doping efficiency observed for 1.8 nm nanocrystals were explained with the extended lattice defect assisted mechanism of incorporation. According to this mechanism, which is not size or shape limited, being active from the initial growth stages, the incorporation of Mn2+ ions takes place at surface sites with high binding energy on dislocation steps formed by the emerging stacking defects. High resolution transmission electron microscopy confirms the presence of such stacking defects in a large proportion of the investigated cubic ZnS nanocrystals, ensuring the operation of the proposed doping mechanism.

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The results of experimental and theoretical ab initio study of structural and piezoelectric properties of (Ba,Sr)TiO3 perovskite solid solutions are discussed and compared. Experimentally, plate-like (Ba,Sr)TiO3 particles were synthesized by the topochemical conversion in the molten salt from Bi4Ti3O12 template plates. All dimensions (side length ≈ 1 µm, thickness ≈ 200-400 nm) were well above the critical size necessary for observation of piezo-and ferroelectricity. The first-principles computations of the structural and electromechanical properties of solid solutions were performed with CRYSTAL14 computer code within the linear combination of atomic orbitals (LCAO) approximation, using three advanced hybrid functionals of the densityfunctional-theory (DFT). Different chemical compositions are considered for the ferroelectric and paraelectric phases. Calculated structural properties of solid solutions in tetragonal and cubic phases are in a very good agreement with experimental data. Experimentally obtained and calculated band gaps are compared for cubic SrTiO3 and tetragonal BaTiO3. BaTiO3/SrTiO3 heterostructures were considered theoretically for different chemical compositions. The calculated piezoelectric properties of solid solutions and heterostructures in ferroelectric phase are compared. It is predicted that both solid solutions and heterostructures improve the piezoelectric properties of the bulk BaTiO3, but solid solutions are more preferable for equal Sr concentrations.

The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N2 adsorption–desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.