Effect of transition metal doping under reducing calcination atmosphere on photocatalytic property of TiO2 immobilized on SiO2 beads.

TiO2 immobilized on SiO2 (TiO2/SiO2) have been prepared by sol-gel method and various ions of transition metals (Cr3+, Co2+ Ni2+, CU2+, and Zn2+) were doped on the photocatalyst using wet impregnation method under reducing calcination atmosphere. The photocatalytic activity of metal doped TiO2/SiO2 towards phenol degradation under black light irradiation were investigated and compared with undoped TiO2/SiO2. The results showed that the photoresponse of Cu2+ and Zn2+ doped TiO2/SiO2 were larger than undoped TiO2/SiO2, indicating that the photogenerated carriers were separated more efficiently in Cu2+ and Zn2+ doped TiO2/SiO2.

Saturated absorption spectroscopy of Xe using a GaAs semiconductor laser.

Doppler-free absorption spectrum from 5P(5)6S to 5P(5)6P transitions of Xe in a hollow cathode discharge was measured in the wavelength region from 810 to 910 mn. The saturated dip signals detected by a frequency modulated probe beam were doubly AM-modulated by a pump beam chopped using a conventional mechanical chopper. The Doppler background was greatly reduced by detection using a second lock in amplifier synchronous to the chopping signal.