The surface properties of polystyrene (PS) films under carbon dioxide (CO2) were studied via a particle embedding technique at quite a low temperature range (308-323 K) in which polystyrene is typically considered to be in a glassy state without CO2. The atomic force microscope (AFM) technique with a tapping mode was used to get the height profiles of gold nanoparticles on the PS film surfaces and PS colloidal crystals for statistical analysis. The embedding of gold nanoparticles demonstrates that the surface mobility of polystyrene was greatly enhanced by exposing it to CO2, with further experimental confirmation by the study of welding polystyrene colloidal crystals under CO2 conditions. Surface mobility as well as embedding depths (from 2 to 17 nm) of nanoparticles is adjustable depending on the CO2 condition applied.