  A brief review is given of recent positron studies of metal and semiconductor
nanocrystals. The prospects offered by positron annihilation as a sensitive
method to access nanocrystal (NC) properties are described and compared with
other experimental methods. The tunability of the electronic structure of
nanocrystals underlies their great potential for application in many areas.
Owing to their large surface-to-volume ratio, the surfaces and interfaces of
NCs play a crucial role in determining their properties. Here we focus on
positron 2D angular correlation of annihilation radiation (2D-ACAR) and
(two-detector) Doppler studies for investigating surfaces and electronic
properties of CdSe NCs.
