Disclosed are compositions including a film enriched with a radioisotope relative to its natural abundance, wherein the film has a thickness of one to ten atomic or molecular layers, decay of the radioisotope comprises emission of electrons, and a majority of the emitted electrons have an energy less than or equal to 700 electron volts (ev). Also disclosed are methods for making the compositions. The compositions can be used in microarrays, nanoarrays, microparticles, nanoparticles, power sources, sensing devices, and medical devices they may also be used in a method of delivering low-energy electrons to a liquid, solid, molecular layer, or cell.
