Anatase nano TiO2 powders were prepared by two different methods. One is the sol-microwave method and the other is oil-bath condition synthesis. A microwave oven (800W) was used as the microwave source. Under 2.45 GHz microwave irradiation, titanium tetra-isopropoxide (TIP) was quickly hydrolyzed and anatase TiO2 was formed in a short time (<4 min). In addition, a simple sol to gel conversion route has been followed for the preparation of anatase phase at 100 degrees C under oil-bath condition. The materials characterized by XRD, Raman, SEM-EDX, TEM, FT-IR and UV-vis techniques. XRD and Raman spectroscopy confirmed both pure and co-doped nano TiO2 have a high degree of crystallinity and existence of fully anatase phase at 500 degrees C. In the microwave method, XRD and TEM results revealed that the particle size of co-doped nano TiO2 is smaller than pure nano TiO2. The photocatalytic activity was tested on the degradation of 4-nitrophenol (4-NP). The nano TiO2 samples prepared by microwave method were more effective than oil-bath samples. (C) 2009 Elsevier B. V. All rights reserved.