Ternary ACd4P3 (A = Na, K) Nanostructures via a Hydride Solution-Phase Route

Complex pnictides such as I–II4–V3 compounds (I = alkali metal; II = divalent transition metal; V = pnictide element) display rich structural chemistry and interesting optoelectronic properties, but can be challenging to synthesize using traditional high-temperature solid-state synthesis. Soft chemistry methods can offer control over particle size, morphology, and properties. However, the synthesis of multinary pnictides from solution remains underdeveloped. Here, we report the colloidal hot-injection synthesis of ACd4P3 (A = Na, K) nanostructures from their alkali metal hydrides (AH). Control studies indicate that NaCd4P3 forms from monometallic Cd0 seeds and not from binary Cd3P2 nanocrystals. IR and ssNMR spectroscopy reveal tri-n-octylphosphine oxide (TOPO) and related ligands are coordinated to the ternary surface. Computational studies show that competing phases with space group symmetries R3̅m and Cm differ by only 30 meV/formula unit, indicating that synthetic access to either of these polymorphs is possible. Our synthesis unlocks a new family of nanoscale multinary pnictide materials that could find use in optoelectronic and energy conversion devices.This article is published as Medina-Gonzalez, Alan M., Philip Yox, Yunhua Chen, Marquix AS Adamson, Maranny Svay, Emily A. Smith, Richard D. Schaller, Aaron J. Rossini, and Javier Vela. "Ternary ACd4P3 (A= Na, K) Nanostructures via a Hydride Solution-Phase Route." ACS Materials Au 1, no. 2 (2021): 130-139. DOI: 10.1021/acsmaterialsau.1c00018. Copyright 2021 The Author(s). Attribution-NonCommercial-ShareAlike 4.0 (CC BY-NC-SA 4.0). DOE Contract Number(s): AC02-07CH11358; AC02-06CH11357. Posted with permission

Solution-Grown Ternary Semiconductors: Nanostructuring and Stereoelectronic Lone Pair Distortions in I–V–VI2 Materials

Alkali pnictogen dichalcogenides─I–V–VI2 or APnCh2─have been identified as promising semiconducting materials for energy conversion devices. However, the controlled nanoscale synthesis and our understanding of the effects of cation ordering and stereochemically active lone pairs on the structures of these ternary compounds remain underdeveloped. Here, we use solution-phase chemistry to synthesize a family of APnCh2 materials, including LiSbSe2, NaSbS2, NaSbSe2, NaBiS2, and NaBiSe2. Our approach utilizes alkali metal hydrides (AH) or carboxylates, A(O2CR), PnPh3, and elemental chalcogens as synthetic precursors and oleylamine or 1-octadecene as solvents. Synthetic manipulation via fine-tuning of reaction temperature enables control over the degree of ordering caused by the Sb 5s2 lone pair-induced distortions in NaSbS2. Pair distribution function analysis demonstrates that the structure of the Sb-containing phases deviates much more from a disordered rock salt structure than that of the Bi-containing phases. This local distortion, induced by the Sb lone pair, leads to a previously unreported noncentrosymmetric NaSbS2 crystal structure, which is additionally supported by second-harmonic generation measurements. Infrared and multinuclear solid-state NMR spectroscopies show that oleylamine or chelating carboxylates and, in some cases, unreacted precursors (LiH and PnPh3) remain bound to the nanocrystalline surfaces. A deeper understanding of the local atomic environment, long-range ordering, surface chemistry, and optoelectronic properties of these materials may speed up their fundamental study and application.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication as Medina-Gonzalez, Alan M., Philip Yox, Yunhua Chen, Marquix AS Adamson, Bryan A. Rosales, Maranny Svay, Emily A. Smith et al. "Solution-Grown Ternary Semiconductors: Nanostructuring and Stereoelectronic Lone Pair Distortions in I–V–VI2 Materials." Chemistry of Materials 34, no. 16 (2022): 7357-7368. Copyright 2022 American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acs.chemmater.2c01410. Posted with permission. DOE Contract Number(s): AC02-07CH11358; AC02-06CH11357; 1905066