An Investigation of Two-Dimensional Arrays of Thiolized Pd Nanocrystals

Two-dimensional arrays of Pd nanocrystals of varying diameters (1.8−6.0 nm) have been obtained after thiolization with alkane thiols of different chain lengths (C 4 −C 16 ). The stability and structure of these arrays have been explained in terms of the ratio of the particle diameter ( d ) and the alkane chain length ( l ). The experimental d − l phase diagram finds support from model calculations, which treat the thiolized nanocrystals as soft spheres. Generally, a d / l value between 1.5 and 3.8 gives crystalline arrays extended over several microns. For d / l values smaller than 1.5 and greater than 4.0, the nanocrystal arrays are disordered or form low-order structures.