Theoretical elucidation of tuning the transport properties of nitrogen and borondoped and co-doped single layer graphene quantum dots with adsorbed molecule by using non-equilibrium Green's function and ab initio method was investigated. The impacts of doping, co-doping of nitrogen, boron atoms on transport properties such as density of state (DOS), transmission coefficient (TE) and current voltage characteristics is demonstrated. Results showed that the adsorption of molecule on layer increases the conductivity of layer. Moreover, the conductance mechanism of the devices in case of doping of boron and co-doping of nitrogen, boron in layer with adsorbed molecule may initially at the same rate but slightly lesser than layer with adsorbed molecule. It may be noted, that doping of nitrogen in layer reduces the conductance drastically. Finally, we have concluded that adsorbed molecule interacts strongly with layer. Theoretical studies suggested that we can use these graphene quantum dots-based devices as a chemical sensor or as a switching device.