  We study optical forces acting upon semiconductor quantum dots and the force
driven motion of the dots in a colloid. In the spectral range of exciton
transitions in uantum dots, when the photon energy is close to the exciton
energy, the polarizability of the dots is drastically increased. It leads to a
resonant increase of both the gradient and the scattering contributions to the
optical force, which enables the efficient manipulation with the dots. We
reveal that the optical grating of the colloid leads to the formation of a
fluid photonic crystal with spatially periodic circulating fluxes and density
of the dots. Pronounced resonant dielectric response of semiconductor quantum
dots enables a separation of the quantum dots with different exciton
frequencies.
