Low-Temperature Atomic Layer-Deposited TiO2 Films with Low Photoactivity

Atomic layer deposition (ALD) has been successfully utilized for the conformal and uniform deposition of ultrathin titanium dioxide (TiO2) films on high-density polyethylene (HDPE) particles. The deposition was carried out by alternating reactions of titanium tetraisopropoxide and H2O2 (50 wt% in H2O) at 77 degrees C in a fluidized bed reactor. X-ray photoelectron spectroscopy confirmed the deposition of TiO2 and scanning transmission electron microscopy showed the conformal TiO2 films deposited on polymer particle surfaces. The TiO2 ALD process yielded a growth rate of 0.15 nm/cycle at 77 degrees C. The results of inductively coupled plasma atomic emission spectroscopy suggested that there was a nucleation period, which showed the reaction mechanism of TiO2 ALD on HDPE particles without chemical functional groups. TiO2 ALD films deposited at such a low temperature had an amorphous structure and showed a much weaker photoactivity intensity than common pigment-grade anatase TiO2 particles.