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 R3¯ m 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.