A solvothermal process for making inorganic nanoparticles is described. Inorganic nanoparticles can be produced by forming a suspension or solution comprising at least one group II-IV and lanthanide metal inorganic salt in a first medium, disposing the suspension or solution in a sealed chamber having an interior pressure, elevating the interior pressure of the sealed chamber to an initial interior pressure prior to the heating, heating the suspension or solution to a peak temperature higher than the normal boiling point of the first medium, optionally adding a second medium to the suspension or solution after the heating.