Light-emitting devices are provided that incorporate one or more underlying LED chips or other light sources and a layer having one or more populations of nanoparticles disposed over the light source. The nanoparticles may absorb some light emitted by the underlying source, and re-emit light at a different level. By varying the type and relative concentration of nanoparticles, different emission spectra may be achieved. White light and specialty-color emission may be achieved. Devices also may include multiple LED chips, with nanoparticles disposed over one or more underlying chips in an array.