The best way to measure nanoparticle size is to use HRTEM. The method my be not very cheap but it gives good result. For known materials such as Si for example physical parameters may help. Such as from the energy gap dependence on particle size since the energy gap in semiconductors has a direct dependence on nano particl size particularly for sizes less than 15nm
for particles in a liquid the liquid colour relates particle size
Dynamic Light Scattering (DLS) is a proven way to quicly characterize the native particle size distribution. Works down to about 20nm as I recall. Some commercially available units also perform zeta potential analysis.
The best way to analyze the particles morphology (i.e. shape, size and geometry) and particle size distribution is to carryout High resolution Transmission electron microscopy (HRTEM).