Photocatalytic degradation of phenol with sol-gel prepared rare earth doped tin dioxide(SnO_2) nanoparticles was reported.Gadolinium doped tin dioxide(SnO_2:Gd) nanoparticles were found to absorb higher visible light compared to lanthanum,neodymium and cerium doped materials that were studied in detail.Photocatalytic degradation of phenol under artificial white light and sunlight in the presence of SnO_2:Gd nanoparticles was studied with high performance liquid chromatography(HPLC),capillary electrophoresis(CE),total organic carbon(TOC) measurements and the determination of chemical oxygen demand(COD).Clear correlations between the results obtained from these multiple measurements were found,and a kinetic pathway for the degradation process was proposed.Within 150 min of solar irradiation,the TOC of a 10 ppm phenol solution in water was reduced by 95%-99%,thus demonstrating that SnO_2:Gd nanoparticles are efficient visible light photocatalysts. Photocatalytic degradation of phenol with sol-gel prepared rare earth doped tin dioxide (SnO_2) nanoparticles was reported to gadolinium doped tin dioxide (SnO_2: Gd) nanoparticles were found to absorb higher visible light compared to lanthanum, neodymium and cerium doped materials that were studied in detail. Photocatalytic degradation of phenol under artificial white light and sunlight in the presence of SnO 2: Gd nanoparticles was studied with high performance liquid chromatography (HPLC), capillary electrophoresis (CE), total organic carbon (TOC) measurements and the determination of chemical oxygen demand (COD). Clear correlations between the results obtained from these multiple measurements were found, and a kinetic pathway for the degradation process was proposed. Whith 150 min of solar irradiation, the TOC of a 10 ppm phenol solution in water was reduced by 95% -99%, thereby demonstrating that SnO 2: Gd nanoparticles are efficient visible light photocatalysts.