Embodiments relate to methods of manufacturing and operating nano-scale energy converters and electric power generators. The nano-scale energy converters include two electrodes separated a predetermined distance. The first electrode is manufactured to have a first work function value. The second electrode is manufactured to have a second work function value different from the first work function value. A cavity is formed between the first and second electrodes, and a nanofluid is disposed in the cavity. The nanofluid includes a plurality of nanoparticles, with the nanoparticles having a third work function value that is greater than the first and second work function values. The relationship of the work function values of the nanoparticles to the work function values of the electrodes optimizes transfer of electrons to the nanoparticles through Brownian motion and electron hopping.