Philip T. Dirlam

Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li–S batteries

High sulfur content copolymers were prepared via inverse vulcanization of sulfur with 1,4-diphenylbutadiyne (DiPhDY) for use as the active cathode material in lithium–sulfur batteries. These sulfur-rich polymers exhibited excellent capacity retention (800 mA h g−1 at 300 cycles) and extended battery lifetimes of over 850 cycles at C/5 rate.

Directing the Deposition of Ferromagnetic Cobalt onto Pt-tipped CdSe@CdS Nanorods: Synthetic and Mechanistic Insights

A methodology providing access to dumbbell-tipped, metal-semiconductor and metal oxide-semiconductor heterostructured nanorods has been developed. The synthesis and characterization of CdSe@CdS nanorods incorporating ferromagnetic cobalt nanoinclusions at both nanorod termini (i.e., dumbbell morphology) are presented. The key step in the synthesis of these heterostructured nanorods was the decoration of CdSe@CdS nanorods with platinum nanoparticle tips, which promoted the deposition of metallic CoNPs onto Pt-tipped CdSe@CdS nanorods. Cobalt nanoparticle tips were then selectively oxidized to afford CdSe@CdS nanorods with cobalt oxide domains at both termini. In the case of longer cobalt-tipped nanorods, heterostructured nanorods were observed to self-organize into complex dipolar assemblies, which formed as a consequence of magnetic associations of terminal CoNP tips. Colloidal polymerization of these cobalt-tipped nanorods afforded fused nanorod assemblies from the oxidation of cobalt nanoparticle tips at the ends of nanorods via the nanoscale Kirkendall effect. Wurtzite CdS nanorods survived both the deposition of metallic CoNP tips and conversion into cobalt oxide phases, as confirmed by both XRD and HRTEM analysis. A series of CdSe@CdS nanorods of four different lengths ranging from 40 to 174 nm and comparable diameters (6-7 nm) were prepared and modified with both cobalt and cobalt oxide tips. The total synthesis of these heterostructured nanorods required five steps from commercially available reagents. Key synthetic considerations are discussed, with particular emphasis on reporting isolated yields of all intermediates and products from scale up of intermediate precursors.

Synthesis of ferromagnetic cobalt nanoparticle tipped CdSe@CdS nanorods: critical role of Pt-activation

The synthesis of a ferromagnetic heterostructured material consisting of a CdSe@CdS nanorod attached to a single dipolar cobalt nanoparticle (CoNP) into a “matchstick” morphology is reported. CdSe@CdS nanorods were modified by an activation reaction with Pt(acac)2 which enabled selective one-sided deposition of a dipolar metallic CoNP-tip via the thermolysis of Co2(CO)8 in the presence of polystyrene ligands. Small (<2 nm) PtNP-tips on CdSe@CdS nanorods were found to be responsible for the selective deposition of CoNP-tips onto one terminus per nanorod. The influence of the Pt-activation step for cobalt tipping was investigated by examination of numerous conditions and characterization of intermediates and materials using transmission electron microscopy and synchrotron X-ray diffraction.