  We study the van der Waals interaction of a metallic or narrow-gap
semiconducting nanowire with a surface, in the regime of intermediate
wire-surface distances $(v_{F}/c)L \ll d \ll L $ or $L \ll d \ll (c/v_{F})L $,
where $L$ is the nanowire length, $d$ is the distance to the surface, and
$v_{F}$ is the characteristic velocity of nanowire electrons (for a metallic
wire, it is the Fermi velocity). Our approach, based on the Luttinger liquid
framework, allows one to analyze the dependence of the interaction on the
interplay between the nanowire length, wire-surface distance, and
characteristic length scales related to the spectral gap and temperature. We
show that this interplay leads to nontrivial modifications of the power law
that governs van der Waals forces, in particular to a non-monotonic dependence
of the power law exponent on the wire-surface separation.
