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 (C4−C16). 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.