CHARACTERIZATION OF TiO2 NANOPARTICLES WITH HIGH-RESOLUTION FEG SCANNING ELECTRON MICROSCOPY

Ultrafine titanium dioxide powder (UF-TiO2) has many applications as a result of its nanometer particle size and semiconducting electric properties. An upgraded method for synthesis of UF-TiO2 was developed, with the ability to control the characteristics of the nanoparticles, i.e. their size, shape and crystal structure. In order to determine the correlation between the various synthesis parameters and the final form of the TiO2 nanoparticles, their size and morphology were analyzed using high-resolution field-emission-gun scanning electron microscopy (FEGSEM). The UF-TiO2 specimens for the FEGSEM high-magnification observations were prepared using three different routes. Micrographs were recorded with an inside-the-lens secondary electron detector and additionally using scanning transmission (STEM) mode. We found that coating the specimens with carbon or Au-Pd did not improve the image quality. Carbon coating was inappropriate because it filled the gaps between the nanoparticles giving the appearance of a smoothed, agglomerated surface. The TiO2 nanoparticles sputtered with Au-Pd were observed to have better contrast; however, they were falsely enlarged due to the Au-Pd nano-layer around them. The best results were obtained with the uncoated specimens, where TiO2 nanoparticles sized 5-10 nm were clearly visible at a magnification of 300 000-times. With STEM mode we were able to distinguish the TiO2 nanoparticles relatively easily; however with different image contrast than when using standard SEM mode.