Abstract: There is provided an energy storage device, comprising a first electrode having a plurality of electrons stored thereon, a second electrode having a plurality of holes stored thereon, the second electrode spaced from the first electrode to define a volume therebetween, a supporting medium disposed in the volume between the first electrode and the second electrode, the supporting medium comprising at least one counterion species, and a plurality of nanoparticle elements provided in the volume, adjacent at least one of the first electrode and the second electrode, the plurality of nanoparticle elements configured to store the electrons therein at different energy levels using quantized capacitance.