  We use an improved version of the standard effective mass approximation model
to describe quantum effects in nanometric semiconductor Quantum Dots (QDs).
This allows analytic computation of relevant quantities to a very large extent.
We obtain, as a function of the QD radius, in precise domains of validity, the
QD excitonic ground state energy and its Stark and Lamb shifts. Finally, the
Purcell effect in QDs is shown to lead to potential QD-LASER emitting in the
range of visible light.
