Hydroxyl radical generation through photocatalytic reaction of TiO2.
The modern chemical industry relies heavily on homogeneous and heterogeneous catalysts. Understanding the operational mode, or reactivity, of these catalysts is crucial for improved developments and enhanced performance. Where paramagnetic centers are involved, ranging from transition metal ions to defects and radicals, EPR spectroscopy is without doubt the technique of choice. For example, photocatalytic oxidation of organic pollutants is frequently carried out using semiconducting polycrystalline powders such as TiO2. A hydroxyl radical is easily formed by light irradiation of TiO2 and detected by EPR using spin traps.
EPR electrochemistry study of ruthenium complexes.
Electrochemical generation method combined with EPR has been used to identify and investigate free radicals derived from both organic and inorganic compounds. Inorganic dyes can be used to improve the efficiency of solar cells. In order to optimize the ligands, one must understand the electronic structure of the dye. Here the electrochemistry and EPR combined with DFT calculations and UV/Vis spectroscopy show the unpaired electron is delocalized between the metal and the ligand.
Enzymatic activity of SOD protein studied via Cu(II) reduction.
Enzymes in the human body regulate oxidation-reduction reactions. These complex proteins, of which several hundred are known, act as catalysts, speeding up chemical processes in the body. Oxidation-reduction reactions also take place in the metabolism of food for energy, with substances in the food broken down into components the body can use. For example, the dismutase activity of Cu,Zn-SOD protein involves reduction of Cu(II)-SOD to Cu(I)-SOD:
Detection of ascorbate radical upon oxidation of vitamin C.
The delicate balance between the advantageous and detrimental effects of free radicals is one of the important aspects of human (patho)physiology. Imbalanced generation of toxic radicals is highly correlated with the pathogenesis of many diseases which require the application of selected antioxidants to regain the homeostasis. EPR is used to determine the oxidative status of biological systems using endogenous long-lived free radicals (ascorbyl radical, tocopheroxyl radical, melanin) as markers.