  We investigate the clustering and dynamics of nano-sized particles
(nano-dust) in high-resolution ($1024^3$) simulations of compressible
isothermal hydrodynamic turbulence. It is well-established that large grains
will decouple from a turbulent gas flow, while small grains will tend to trace
the motion of the gas. We demonstrate that nano-sized grains may cluster in a
turbulent flow (fractal small-scale clustering), which increases the local
grain density by at least a factor of a few. In combination with the fact that
nano-dust grains may be abundant in general, and the increased interaction rate
due to turbulent motions, aggregation involving nano dust may have a rather
high probability. Small-scale clustering will also affect extinction
properties. As an example we present an extinction model based on silicates,
graphite and metallic iron, assuming strong clustering of grain sizes in the
nanometre range, could explain the extreme and rapidly varying ultraviolet
extinction in the host of GRB 140506A.
