ABSTRACT
This chapter provides electron paramagnetic resonance (EPR) spectroscopy with the spin-trap 5,5-dimethyl-l-pyrroline N-oxide (DMPO) to examine the nature of the photocatalytic process and, particularly, to examine whether or not the process is heterogeneous. It presents the initial growth rates of the DMPO-OH spin-adduct electron paramagnetic resonance (EPR) signal in systems with different scavengers within a competitive reaction scheme. The kinetic behavior of truly homogeneous systems was compared with that of the TiO2 systems to establish the photocatalytic pathway. Photodegradation, using small semiconductor particles as a photocatalyst, is an efficient and practical method to convert organic pollutants in water into harmless substances. Electron paramagnetic resonance spectroscopy is a technique that is sensitive to the presence of molecules with unpaired electrons. This problem can be solved by the use of the spin-trapping technique in which compounds called spin traps are used to convert reactive radicals into relatively stable radicals, which can be then detected by EPR.
