Abstract: Platinum nanoparticles prepared by the interaction of Chloroplatinic acid (H2PtCl6). H2O and hydrazine hydrate (N2H4.H2O) in water-in-oil microemulsion [Polyoxyethylene-4-dodecylether (C12E4) + Cyclohexane C6H12) + Water (H2O)] in the absence and presence of poly(N-vinylpyrrolidone) (PVP) and Polyethylene Glycol (PEG) have been characterized using X-Ray diffraction (XRD), electron diffraction and transmission Electron Microscopy (TEM) techniques. Platinum nanoparticles adsorbed on alumina converted CO to CO2 at much lower temperature (245°C) compared to 325°C when pure alumina was used as catalyst. The catalytic activity of the synthesized nanoparticles in microemulsion containing PVP, examined in terms of CO to CO2 conversion reaction as a function of temperature exhibit higher catalytic efficiency compared with those synthesized in the microemulsion without PVP and microemulsion-PEG systems.