Alkanethiolate-Protected Palladium Nanoparticles

Abstract

The synthesis and characterization of stable nanometer-sized alkanethiolate-protected palladium particles are described. The particles were synthesized in a biphasic system, and the formation appeared to involve a dynamic process, where initially larger particles were quickly formed, followed by decomposition into smaller and more stable particles. The solution color was found to change concurrently. With varied synthetic conditions, the particle size was found to vary and fall mainly within the size range of 1−5 nm in diameter with modest dispersity as determined by transmission electron microscopy. UV−vis spectroscopic measurements showed a Mie scattering profile, but no well-defined surface−plasmon resonance. FTIR studies indicated that the monolayers became more ordered with longer chain lengths of the protecting alkanethiolates. Electrochemical studies exhibited the solution-phase Coulomb staircase charging of the particle double layers, analogous to the observations with gold particles, where the peak spacings corresponded to a (sub)attofarad capacitance for the palladium particles.