Methods of writing data to and reading data from memory devices and systems for writing and reading data are disclosed. The database management layer can receive an initial communication from the application layer and transmit a subsequent communication to a particular database based upon a rule. The coating material has chemical compounds or ligands with functional groups or moieties with conjugated electrons and moieties for imparting solubility to coated fluorescent nanocrystals in aqueous solutions. The invention applies to any light emitter, and therefore notably to lasers and more particularly still to QCLs. This allows the file to have any sufficient size and to display and synchronize all desired images with an audio presentation.