Formation and Transformation of Cu 2- x Se 1- y Te y Nanoparticles Synthesized by Tellurium Anion Exchange of Copper Selenide

• Published in: Inorganic chemistry 2023-03, Vol.62 (11), p.4550-4557
• Main Authors: Thompson, Katherine L, Katzbaer, Rowan R, Terrones, Mauricio, Schaak, Raymond E
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c04467

Ion exchange reactions of colloidal nanoparticles post-synthetically modify the composition while maintaining the morphology and crystal structure and therefore are important for tuning properties and producing otherwise inaccessible and/or metastable materials. Reactions involving anion exchange of metal chalcogenides are particularly interesting, as they involve the replacement of the sublattice that defines the structure while also requiring high temperatures that can be disruptive. Here, we show that the tellurium anion exchange of weissite Cu Se nanoparticles using a trioctylphosphine-tellurium complex (TOP═Te) yields weissite Cu Se Te solid solutions, rather than complete exchange to weissite Cu Te, with compositions that are tunable based on the amount of TOP═Te used. Upon storage at room temperature in either solvent or air, tellurium-rich Cu Se Te solid solution nanoparticles transform, over the span of several days, to a selenium-rich Cu Se Te composition. The tellurium that is expelled from the solid solution during this process migrates to the surface and forms a tellurium oxide shell, which correlates with the onset of particle agglomeration due to the change in surface chemistry. Collectively, this study demonstrates tunable composition during tellurium anion exchange of copper selenide nanoparticles along with unusual post-exchange reactivity that transforms the composition, surface chemistry, and colloidal dispersibility due to the apparent metastable nature of the solid solution product.