The　behavior　of　water　molecules　on　the　surfaces　of　the　TiO2　nanowire　grown　in　[0 0 1]　direction　has　been　investigated　by　combining　theoretical　calculations　and　experiments.　Calculated　UV–visible　absorption　spectra　reproduce　the　main　features　of　the　experimental　spectra.　Computations　predict　that　a　photoexcitation　followed　by　a　sequence　of　relaxation　events　results　in　photoluminescence　across　the　gap.　TiO2　nanowires　in　vacuum　and　aqueous　environment　exhibit　different　dynamics　of　photo-excited　charge　carriers.　In　water,　computed　relaxation　of　electrons　(holes)　is　approximately　2　(4)　times　faster　compared　with　vacuum　environment.　Faster　relaxation　of　holes　vs.　electrons　and　specific　spatial　localization　of　holes　result　to　formation　of　long　lived　charge　transfer　excitation　with　positive　charge　at　the　surface　of　the　nanowire.　Comparison　of　relaxation　process　in　TiO2/water　interfaces　focusing　on　different　surfaces　and　nanostructures　has　potential　in　identifying　structural　characteristics　of　TiO2　materials　important　for　efficient　photo-electrochemical　water　splitting.　©　2016　Elsevier　B.V.