A parallel-plate, low-pressure plasma for fundamental nanodusty plasma research is used to grow hydrogenated amorphous carbon nanoparticles using an argon-acetylene gas mixture. The particles stay confined in the volume of the argon plasma after turning off the C H 2 2 gas flow and the effects of prolonged treatment with noble gas (Ar) and reactive gas mixtures (Ar/H 2 , Ar/D 2 , or Ar/O 2 ) are investigated using in situ infrared absorption spectroscopy.Additionally, ex situ scanning electron microscopy imaging of extracted nanoparticles is used to analyze their size and surface morphology. In 45 min of argon treatment, a size increase of about 50% is seen together with a decrease in sp CH x 2