Solution-based synthesis of anisotropic metal chalcogenide nanocrystals and their applications

This article reviews recent advances in solution phase synthesis to generate 1-D and 2-D anisotropic metal chalcogenide (MC) nanostructures with a focus on using different growth mechanisms to control the shapes of the MCs. Four different synthetic approaches have been reviewed: naturally favoured growth due to its intrinsically anisotropic crystal structure, modified anisotropic growth by changing surface energies or utilizing organic templates, oriented attachment of small nanocrystal building blocks to form nanowires or nanosheets, and chemical transformation from existing nanostructures into new species. We discuss current understanding of the thermodynamic and kinetic aspects associated with the mechanisms of forming these anisotropic MC nanostructures. We provide examples of representative applications of anisotropic chalcogenide nanomaterials that are expected to be practically meaningful in the near future. The applications include electrodes for lithium ion batteries, photodetectors, thermoelectric devices, and solar cells. A brief review of other potential applications (oxygen reduction reaction, localized surface plasmon resonance, topological insulator, superconductor) is provided as well. This review ends with discussions on the challenges to be investigated thoroughly in the solution-based synthesis of anisotropic nanomaterials, which includes surface energy control, correcting the nucleation Er growth mechanism, removal of the organic surfactant, kinetic study on the chemical transformation, scale-up of production, and eco-friendly synthesis.