Gold nanoparticles decorated onto titania (anatase) supports were produced through X-ray radiolysis, at ambient temperature and pressure in a method that departs from traditional routes, providing an outstanding control of Au nanoparticle size and dispersion. Au@TiO2 nanocomposites (NCs) were fabricated using different absorbed doses in the presence of NaOH, or urea, supported by 5-10 or 10-30 nm titania, to determine their effects on the Au particle size distribution and loading. Au@TiO2 NCs fabricated at high absorbed doses (> 7 kGy) had average Au NP size of 1.1 perpendicular to 0.1 nm. Large absorbed doses control Au NP size by generating an abundance of reducing species (e(-) (aq), H center dot) resulting in an increase of Au seeds. At a lower absorbed dose (0.72 kGy), the ligand affected the Au particle size distribution and a reduction in size by 20% of the Au was observed using NaOH. Au NPs were tethered to titania through oxygen as indicated by X-ray photoelectron spectroscopy analysis. The Au@TiO2 NCs were tested for their radiosensitizing effect by monitoring decomposition of methylene blue under X-ray irradiation where the decomposition was increased by a factor of 1.8 after 15 min compared with pristine TiO2. (C) 2017 Elsevier B.V. All rights reserved.