  We quantify nonergodic and aging behaviors of nanocrystals (or quantum dots)
based on stochastic model. Ergodicity breaking is characterized based on time
average intensity and time average correlation function, which remain random
even in the limit of long measurement time. We argue that certain aspects of
nonergodicity can be explained based on a modification of Onsager's diffusion
model of an ion pair escaping neutralization. We explain how diffusion models
generate nonergodic behavior, namely a simple mechanism is responsible for the
breakdown of the standard assumption of statistical mechanics. Data analysis
shows that distributions of on and off intervals in the nanocrystal blinking
are almost identical, $\psi_{\pm}(\tau)\propto A_{\pm}\tau^{-(1+\alpha_{\pm})}$
with $A_{+}\approx A_{-}$ and $\alpha_{+}\approx\alpha_{-}=\alpha$ and
$\alpha\approx0.8$. The latter exponent indicates that a simple diffusion model
with $\alpha=0.5$ neglecting the electron-hole Coulomb interaction and/or
tunneling, is not sufficient.
