Due to the increase in environmental pollution, the monitoring of greenhouse gases became a topic of interest for the damage they cause to the ecosystems and human health. One such harmful gas is carbon monoxide which is highly toxic. In this present work, the sensing of to is done by using thin films of Sn02 and Sn02iAI doped nanoparticles synthetized by sol-gel method, to observe changes in response. The optical characterization was done using DLS and FTIR spectroscopy. For morphological characterization was done using SEM. The crystal structure characterization was done using DRX.