Deciphering Concurrent Seed Growth and Cation Exchange Kinetics in the Transformation of Cu_2-xS Nanocrystals to CuGaS₂ Nanorods

Cation exchange offers a novel approach for synthesizing complex-structured nanocrystals. This process typically involves using easily synthesized and controllable nanoparticles as seed templates, with the subsequent partial or complete exchange of cations regulated by factors such as ligands, temperature, and time. Nanocrystals prepared through cation exchange can flexibly control crystal phase, stoichiometry, and morphology. Beyond cation exchange without altering shape and size, achieving anisotropic heterostructured nanorods through concurrent epitaxial growth has garnered significant attention. Here, we quantify the kinetics of the transformation from low-chalcocite Cu_2-xS to wurtzite CuGaS₂nanorods through concurrent epitaxial growth, cation exchange, and interfacial diffusion. We investigate the effects of growth temperature and seed size on the reaction kinetics and the resulting morphology. By precisely controlling temperature and time, a series of Janus particles with varying elemental ratios up to fully substituted CuGaS₂nanorods can be obtained. This provides a practical approach for the precise regulation of the competition between cation exchange process and solution epitaxial growth.