Synthesis and characterization of PtNi dendrimer-encapsulated nanoparticles
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This thesis reports on the synthesis and characterization of PtNi dendrimer-encapsulated nanoparticles (DENs) containing on average 147 atoms. This is significant because PtNi DENs have not yet been reported. The DENs were prepared by first complexation of Pt²⁺ to the interior tertiary amines of a sixth-generation, hydroxyl-terminated (G6-OH) poly(amidoamine) (PAMAM) dendrimer template, followed by chemical reduction in the presence of free Ni²⁺ to yield PtNi DENs. UV-visible (UV-vis) absorbance measurements exhibit a broad, monotonically decreasing band characteristic of nanoparticle formation. Upon dialysis in both H₂ and O₂ this band is observed to decrease in absorbance. Transmission electron microscopy (TEM) studies indicate that particles have been synthesized and are 1.8 + 0.2 nm before dialysis and 1.9 + 0.2 nm after dialysis under H₂. Results obtained from X-ray photoelectron spectroscopy (XPS) show that Pt is present and the Pt(4f7/2) binding energy is observed at 72.0 eV before dialysis and 71.5 eV after dialysis under H₂. XPS shows that Ni is present and the Ni(2p3/2) binding energy is centered at 857.0 eV before dialysis and 856.6 eV after dialysis under H₂. Finally, oxidative electrochemical stripping is observed at 1.07 V (vs NHE) for PtNi DENs immobilized on glassy carbon electrodes (GCE) and is tentatively assigned to Ni.