Paper Title
Enhanced Photocatalytic Properties of Pure and Ln (la3+, eu3+, ce3+) � Modified ZnO Powders Synthesized by Hydrothermal Method

Abstract
Simple and fast hydrothermal method is used to synthesize ZnO and Ln�doped (La3+, Eu3+, Ce3+) ZnO powders. Nanocrystalline photocatalysts with 2.0 mol% concentration are annealed at 100C for 1h. The pure and doped powders are characterized by X-ray diffraction, Scanning Electron Microscopy. The photocatalytic action of the mixtures is tested in photocatalytic oxidation of ethylene as model air pollutant (5000 ppm feed concentration) in gas-phase flat-plate continuous flow photocatalytic reactor at maximum ethylene contact time of 4 min and optimal relative humidity 30%. The powder-form samples were suspended in water and after sonication (24 kHz) to disintegrate agglomerates the slurry is deposited by the capillary method on TLC sheets to obtain 1 mg/cm2 loading. The photoactivity testing was carried out using UV-A and UV-C illumination (0.014 W/cm2). Eu3+-modified ZnO is superior to pure ZnO. It gave the highest conversion degrees both under UV-A and UV-C illumination, whereupon the latter yielded superior performance. There is no activity under visible light illumination due to the wide band gap. Keywords� ZnO, Rare Earths, Powders, photocatalysis.