Disclosed herein is a method for synthesizing a nano-emulsion fuel composition. The method may include forming a water-in-fossil fuel emulsion by dispersing water into a fossil fuel in the presence of a surfactant, synthesizing carbon quantum dots with an average diameter between 0.5 nanometers to 20 nanometers, forming a mixture of the synthesized carbon quantum dots and the water-in-fossil fuel emulsion by dispersing the synthesized carbon quantum dots into the water-in-fossil fuel emulsion; the carbon quantum dots comprising 1 ppm to 10000 ppm of the mixture, and forming a nano-emulsion fuel composition by mixing a biofuel into the mixture of carbon quantum dots and the water-in-fossil fuel emulsion.