Abstract This work addresses the issue of radiation chemical synthesis of MnO 2 nanoparticles and also illustrates the ease of formation of nanorods and sheets by adroit manipulation of experimental conditions. The radiation chemical yield ( G-value) for reduction of Mn (VII) by the hydrated electron was found to be 0.27 μmol J −1 and 0.17 μmol J −1 respectively, when tert. butanol and isopropanol were used as scavengers in nitrogen-saturated solutions. The colloids formed upon irradiation of air-saturated solution and N 2-purged solution with tert. butanol as scavenger were found to be most stable. Irradiation of air-saturated solution containing 4×10 −4 M KMnO 4 at a dose of 1692 Gy resulted in the formation of nanorods of the dimension 100–150 nm and nanospheres in the range 10–20 nm. Irradiation of N 2-purged solution containing tert. butanol as scavenger for OH-produced reticulated structure of nanorods with length varying from 50 to 100 nm at a dose of 1692 Gy. Elemental analysis was performed using scanning electron microscope on MnO 2 formed by reduction and oxidation and the purity was found to be 98% of elemental Mn content.