[en] Highlights: • Noble metal (Au, Ag, Pt) nanodots with a size of 1–6 nm are deposited onto TiO₂ nanoparticles by magnetron sputtering. • A frequency-varied generator in magnetron sputtering equipment is designed for nanoparticles' dispersity and movability. • Photocatalytic activity of Ag/TiO₂ nanocomposite is 2.7 times that of pure TiO₂. Magnetron-sputtering deposition of coatings onto a flat surface is well established, but coating metal on the curved surface of nanoparticles (NPs) is still challenging. Herein, by using a magnetron sputtering system in which a vibration generator with variable frequency is applied to the sample stage to maintain NPs' dispersity and movability, we successfully deposit noble metal (Au, Ag, Pt) nanodots onto the surface of TiO₂ NPs. It is found that the metal nanodots are of a size of 1–6 nm and they are firmly bonded to the TiO₂ NPs' surface. The photocatalytic activity of Ag/TiO₂ is demonstrated to be 2.7 times that of pure TiO₂ under simulated sunlight irradiation. This study creates new opportunities for fabricating excellent NP composite catalysts by liquid-free methods.