Water-soluble　anatase,　mixed-phase　(anatase　and　rutile)　and　rutile　TiO2　nanoparticles　(NPs)　or　nanorods　were　synthesized　under　mild　solution　conditions　using　polyethylene　glycol　400　(PEG　400)　as　a　stabilizer　and　HCl　as　a　phase　controlling　reagent.　The　photocatalytic　properties　of　these　NPs　with　different　crystal　phases　were　evaluated　by　photocatalytic　degradation　experiments　of　methyl　orange　(MO).　As-prepared　pure　anatase　TiO2　NPs　show　a　higher　photocatalytic　activity　than　other　samples　and　commercial　P25,　which　may　be　related　to　the　high　crystallinity,　the　pure　anatase　phase,　small　size　and　the　enhanced　absorbability　associated　with　the　existence　of　PEG　400　on　the　NP　surface.　(C)　2010　Elsevier　B.V.　All　rights　reserved.