Temperature-Dependent Selection of Reaction Pathways, Reactive Species, and Products during Postsynthetic Selenization of Copper Sulfide Nanoparticles

Abstract

Rational design of elaborate, multicomponent nanomaterials is important for the development of many technologies such as optoelectronic devices, photocatalysts, and ion batteries. Combination of metal chalcogenides with different anions, such as in CdS/CdSe structures, is particularly effective for creating heterojunctions with valence band offsets. Seeded growth, often coupled with cation exchange, is commonly used to create various core/shell, dot-in-rod, or multipod geometries. To augment this library of multichalcogenide structures with new geometries, we have developed a method for postsynthetic transformation of copper sulfide nanorods into several different classes of nanoheterostructures containing both copper sulfide and copper selenide. Two distinct temperature-dependent pathways allow us to select from several outcomes�rectangular, faceted Cu 2−x S/Cu 2−x Se core/shell structures, nanorhombuses with a Cu 2−x S core, and triangular deposits of Cu 2−x Se or Cu 2−x (S,Se) solid solutions. These different outcomes arise due to the evolution of the molecular components in solution. At lower temperatures, slow Cu 2−x S dissolution leads to concerted morphology change and Cu 2−x Se deposition, while Se-anion exchange dominates at higher temperatures. We present detailed characterization of these Cu 2−x S−Cu 2−x Se nanoheterostructures by transmission electron microscopy (TEM), powder X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning TEM−energy-dispersive spectroscopy. Furthermore, we correlate the selenium species present in solution with the roles they play in the temperature dependence of nanoheterostructure formation by comparing the outcomes of the established reaction conditions to use of didecyl diselenide as a transformation precursor.

Controlling Phase in Colloidal Synthesis

“…These studies rely on more traditional organic chemistry techniques such as 1 H, 13 C, and 77 Se nuclear magnetic resonance (NMR), gas chromatography–mass spectroscopy (GC-MS), and even gas-phase infrared spectroscopy (IR) to track reaction progressions of the organic species. For the synthesis of metal selenides, 77 Se NMR can be particularly helpful in determining intermedaites. ,, The NMR solvent 1,2-dichlorobenzene- d 4 is readily available and allows for reactions up to 178 °C. Therefore, in situ studies with heated probes of nanocrystal synthesis that happen at moderate temperatures are possible.…”

Nanomaterials Research at a Primarily Undergraduate Institution: Transforming Nanorods, Undergraduate Research Communities, and Infrastructure

“…It can be even more challenging to design nonspherical multicomponent nanoparticles with specific placement of different chemical species, as can be required for advanced catalytic, optical, thermoelectric, magnetic, and active matter applications. Synthetic routes to multicomponent nanoparticles, which incorporate multiple materials into a single nanoparticle, include seeded growth and directed deposition. − Postsynthetic transformation of nanoparticles is an alternative route whereby synthon particles are first synthesized using direct methods and then in subsequent steps the sizes, shapes, compositions, and/or phases of the synthon particles are altered. − Copper sulfide nanoparticles have proven to be particularly amenable to PST with an increasingly large toolbox of PST reactions including cation exchange, − anion exchange, − ,, shape change, ,, and redox doping. ,,, …”

“…(b) Alteration with Se 2– is more complicated, with changes in shape, phase, and regioselectivity with reaction temperature due to different mechanisms. The transformation with Se 2– is simplified by use of a dialkyldiselenide reagent for anion exchange . Adapted from ref .…”

“…The transformation with Se 2– is simplified by use of a dialkyldiselenide reagent for anion exchange . Adapted from ref . Copyright 2023 American Chemical Society.…”

“…Our recent publication, “Temperature-Dependent Selection of Reaction Pathways, Reactive Species, and Products during Postsynthetic Selenization of Copper Sulfide Nanoparticles,″ demonstrates how a series of modular, low-entry barrier projects can be connected into a coherent story. In the summer of 2021, Brandon tested what happens when roxbyite rods were injected into a 1-dodecanethiol (DDT), selenium, 1-octadecene (ODE) solution at different temperatures, discovering an interesting transformation that only required two synthetic skill sets.…”