SURFACE OXYGEN RADICALS ORIGINATING VIA REDOX REACTIONS DURING THE MECHANICAL ACTIVATION OF CRYSTALLINE SIO2 IN HYDROGEN-PEROXIDE

Two surface dinuclear oxygen species simultaneously form when quartz is ground in a solution of hydrogen peroxide. They are the superoxide O-2 radical (gzz=2.044, gyy=2.010, gxx=2.002) and the peroxy SiOO· radical (gzz= 2.064, gyy= 2.007, gxx= 2.002). They are formed by contact of the freshly created surface, bearing reactive centres originated by cleavage of the SiOSi bonds, with H2O2. In parallel, OH· radicals are detected in the solution. A scheme involving the catalytic decomposition of hydrogen peroxide is proposed accounting for the radical species observed at the surface and in solution. © 1990.