Versatile Colloidal Syntheses of Metal Chalcogenide Nanoparticles from Elemental Precursors Using Amine-Thiol Chemistry

Colloidal metal chalcogenide nanoparticles have emerged as a promising hydrazine-free route for the fabrication of solution processed electronic devices. While a wide variety of synthetic pathways have been developed for these nanomaterials, typical colloidal syntheses rely on the use of metal salts as precursors, which contain anionic impurities such as halides, nitrates, acetates, and so forth, that may incorporate and alter the electrical properties of the targeted nanoparticles. In this report, the recent advances in amine-thiol chemistry and its unique ability to dissolve pure metals, chalcogens, and metal chalcogenides is expanded upon for the fabrication of metal chalcogenide nanoparticles. Alkylammonium metal thiolate species are easily formed upon addition of monoamine and dithiol to elemental Cu, In, Ga, Sn, Zn, Se, or metal chalcogenides such as Cu2S and Ag2S. These species were then used directly for the synthesis of colloidal nanoparticles without the need for any additional purification. The thermal decomposition pathway of one such representative alkylammonium metal thiolate species was studied, verifying that only metal chalcogenides and volatile byproducts are formed, providing a flexible route to compositionally uniform, phase pure, and anionic impurity-free colloidal nanoparticles. Synthetic methods were developed from these precursors to yield pure phase colloidal nanoparticles of binary, ternary, and quaternary materials and their alloys including In2S3, (InxGa1–x)2S3, CuInS2, CuIn(SxSe1–x)2, Cu(InxGa1–x)S2, Cu2ZnSnS4, and AgInS2. Successful synthesis with various experimental methods such as heat up, hot injection, and microwave assisted solvothermal reactions were also demonstrated, showing the flexibility and greater scope for this new synthesis route.