Figure 25. Mossbauer hyperfine parameters: (a) Hyperfine field Bhyp. (b) Quadrupole splitting (QS). (c) Isomer shift IS. (d) Linewidth T measured in heating and cooling cycles. The solid star-shaped symbols are check points from the repeated measurements.

The energy of sunlight, mainly the UV part of the spectrum (360-380 nm), excites titanium dioxide nanoparticles, creating a photogenerated electron and a highly oxidizing hole in the conduction and valence band of the semiconductor [449, 450]. The electron can be scavenged by oxygen, and the hole can react with surface-bound OH on the TiO2, creating a highly reactive OH* radical that can completely mineralize organic components [451, 452] (Scheme 15).

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