Investigating the growth mechanism and optical properties of carbon-coated titanium dioxide nanoparticles

TiO2 nanoparticles (NPs) were prepared using flame synthesis and then characterized using transmission electron microscopy. We found that the flame method yields both crystalline TiO2 and amorphous TiO2 NPs. TEM analysis revealed that only the crystalline TiO2 NPs were coated with carbon. Based on this observation, we proposed a growth model for the diffusion and precipitation of carbon atoms in TiO2 NPs. The optical properties of TiO2 NPs were investigated by performing valence electron energy loss spectrometry analysis. We observed that carbon-coated TiO2 NPs have higher absorption in the visible range due to their lower band-gap energy.