NOVELTY - An exfoliated graphite nanoparticle (EGN) film (120) comprises monolayer EGN film comprising exfoliated graphite nanoparticles and first polyelectrolyte distributed throughout monolayer EGN film or multilayer EGN film comprising monolayer EGN films arranged in layered configuration; where monolayer EGN film has thickness of 0.2-20 nm, an electrical conductivity of 80 S/cm, and has a transparency in the visible electromagnetic spectrum of at least 25%. The EGN film is in the form of monolayer EGN film, multilayer EGN film or free-standing film.    USE - As exfoliated graphite nanoparticle film used in optoelectronics devices e.g. display devices (e.g. cathode ray, liquid crystal display, plasma televisions and display devices); for free-standing graphite sheets include structured carbon electrodes for fuel cells, batteries, and supercapacitors; highly electrically and thermally conductive non-transparent films for electronics; and for energy storage device.    ADVANTAGE - The compact and defect-free structure of the film insures high electrical conductivity with very high transparency in the visible spectrum. The method also allows the deposition of EGN particles of various thicknesses. Thus, with reduced EGN thickness, the formation of the compact monolayer and multilayer film structures can be developed to produce transparent and highly conductive films for field effect transistors or optoelectronic applications. The new method requires very small amounts of EGN in suspension to create the monolayer or multilayer film on macroscopic areas of a substrate; thus, the process in inexpensive and can be completed in much less time. This method allows rapid deposition of EGN particles over large macroscopic areas in a single step. No specialized equipment is required for implementation. The monolayer film formed with this method is much thinner and produces not only higher electrical conductivity but also much higher transparency both in the visible and the infrared spectrum of electromagnetic radiation. The method is very easy and quick; it can be scaled to producing films of very large lateral dimensions without any alteration of the process. The process is simple and non-hazardous.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for forming a nanoparticle film-coated substrate involving providing a substrate assembly comprising a first substrate and a second substrate at a preselected distance from the first substrate, where the first and second substrates define an interstitial space and the first substrate further comprises a first polyelectrolyte deposited on a surface of the first substrate facing the interstitial area; providing deposition dispersion comprising liquid medium, second polyelectrolyte oppositely charged to the first polyelectrolyte, and nanoparticles dispersed; filling the interstitial space with the deposition dispersion; and evaporating the liquid medium in the interstitial space, thus depositing the nanoparticles as a film on the surface of the first substrate having the first polyelectrolyte and forming nanoparticle film-coated substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of cross-sectional view of exfoliated graphite nanoparticle (EGN) film-coated substrate.    Exfoliated graphite nanoparticle film-coated substrate (100)    Substrate (110)    Exfoliated graphite nanoparticle film (120)