The authors carry out ligand exchange reaction replacing bulky insulating org. ligands with inorg. chalcogenidometallate clusters in nanocrystal assemblies floating at the gas-liq. interface. The mobility of the nanocrystals allows lattice contraction without significantly diminishing the ordering obsd. by grazing incidence X-ray scattering and transmission electron microscopy (TEM). This approach produces inorg. nanocomposite films one to a few nanocrystals in thickness with highly regular arrangements of nanocrystals. Anal. of free-standing nanocrystal membranes by low-dose, aberration-cor. TEM allows direct visualization of the nanocrystal-matrix interface.