Controlling Phase in Colloidal Synthesis.

A fundamental precept of chemistry is that properties are manifestations of the elements present and their arrangement in space. Controlling the arrangement of atoms in nanocrystals is not well understood in nanocrystal synthesis, especially in the transition metal chalcogenides and pnictides, which have rich phase spaces. This Perspective will cover some of the recent advances and current challenges.

Dependence of Transition-Metal Telluride Phases on Metal Precursor Reactivity and Mechanistic Implications.

Modern bottom-up synthesis to nanocrystalline solid-state materials often lacks the reasoned product control that molecular chemistry boasts from having over a century of research and development. In this study, six transition metals including iron, cobalt, nickel, ruthenium, palladium, and platinum were reacted with the mild reagent didodecyl ditelluride in their acetylacetonate, chloride, bromide, iodide, and triflate salts. This systematic analysis demonstrates how rationally matching the reactivity of metal salts to the telluride precursor is necessary for the successful production of metal tellurides.

Molecular Decomposition Routes of Diaryl Diselenide Precursors in Relation to the Phase Determination of Copper Selenides.

H nuclear magnetic resonance (NMR), Se NMR, and powder X-ray diffraction (XRD) were used to monitor the thermal decomposition of diphenyl and dibenzyl diselenide precursors toward the synthesis of copper selenides. Copper was found to promote the decomposition of both precursors. The inorganic nanocrystals and organic byproducts were sensitive to the specific diaryl diselenides and the presence of oleylamine and copper.

Galvanic replacement of intermetallic nanocrystals as a route toward complex heterostructures.

Galvanic replacement reactions are a reliable method for transforming monometallic nanotemplates into bimetallic products with complex nanoscale architectures. When replacing bimetallic nanotemplates, even more complex multimetallic products can be made, with final nanocrystal shapes and architectures depending on multiple processes, including Ostwald ripening and the Kirkendall effect. Galvanic replacement, therefore, is a promising tool in increasing the architectural complexity of multimetallic templates, especially if we can identify and control the relevant processes in a given system and apply them more broadly.