Nanosized TiO2 powders for photocatalytic degradation of organic pollutants are prepared by sol-gel method. The -Ti-O-Ti- network is synthesized by hydrolysis and controlled condensation of titanium isopropoxide Ti(O-iC(3)H(7))(4). The resulting alcogels are dried under air to form xerogels or under supercritical CO2 to form aerogels. In both cases, drying is followed by thermal treatment under air and gives crystallized white and dry powders. These powders are characterized by XRD, SEM, and specific surface area measurements. Their electronic properties are determined through Time Resolved Microwave Conductivity. Their photocatalytic activities are tested in the photodegradation of phenol in water. # Results establish a strong correlation between synthesis, structure, charge-carrier lifetimes and photocatalytic activity. The influence of the supercritical drying on the final properties of materials is also evidenced. (C) 2004 Elsevier B.V. All rights reserved.