Jem 2100plus instrument

Transmission electron microscopy (TEM) was carried out using a JEM-2100Plus instrument from JEOL operating at an accelerating voltage of 200 kV. The images were taken with a 4K CMOS camera from TVIPS. The TEM is equipped with a LaB₆ cathode and high-resolution pole piece to achieve a point resolution in the TEM mode of 0.23 nm. The sample preparation was performed by grinding the sample in a mortar and pestle in ethanol and the dispersed particles were supported on a TEM lacey carbon grid.

The obtained powders were characterized by XRD with Cu-Kα radiation (Smart Lab, Rigaku, Japan) and Raman spectroscopy with a 325 nm He–Cd laser (LabRAM HR800, Horiba Ltd., Japan).
The densities of the compact samples (d₁) were calculated from the weights and volumes of the pellets, and those of the powders (d₂) were measured using a gas pycnometer (AccuPyc II 1340, Shimadzu, Japan). The relative density was defined as d₁ / d₂.
The structure of the pellet cross-section was observed using scanning electron microscopy (SEM; JSM-6610A, JEOL, Japan).
A DTA curve was obtained for the powder sample in an Al pan under a N₂ atmosphere using a thermal analyzer (Thermo-plus 8110, Rigaku, Japan). The heating rate was 10 °C min⁻¹ from room temperature to 500 °C.
TEM was performed using a JEM-2100Plus instrument at an acceleration voltage of 200 kV (JEOL, Japan). High-resolution TEM (HR-TEM) images were obtained using a high-speed camera (OneView, Gatan) to minimize electron damage. The synthesized powders were dispersed on carbon grids in an Ar atmosphere in a glove box. The specimens were transferred without exposure to air using a vacuum transfer holder (Mel-Build Co.).

The following five commercially available metal oxide nanoparticles were tested:
Aeroxide^® TiO₂ P25 (Evonik Industries, Essen, Germany); Aerosil^® SiO₂ 200 Pharma, R805, R9200 (Evonik Industries, Essen, Germany) and NanoZnO (Bochemie, Bohumín, Czech Republic).
The morphological properties of the nanoparticles were determined by the analysis of adsorption isotherms of nitrogen or krypton at ca 77 K, using a Micrometrics 3Flex volumetric adsorption unit, by scanning electron microscopy (SEM),using JSM-6700F microscope (Jeol, Tokyo, Japan) and by high-resolution transmission electron microscopy (HRTEM) using JEM-2100Plus instrument (Jeol, Tokyo, Japan). The size distribution and zeta potential of the nanoparticles in dispersions (in water-bovine serum albumin (BSA) and cell culture medium) was measured by dynamic light scattering using ZetaSizer Nano ZS (Malvern Instruments Ltd., Malvern, UK). The structural properties of the nanoparticles were determined by Fourier transform infrared (FTIR) spectroscopy using a Nicolet 6700 apparatus (Madison, WI, USA).