HotInjection

Hot injection is a chemical synthesis technique used to create colloidal nanocrystals with controlled size and narrow distribution. In this method, a precursor solution is rapidly injected into a hot coordinating solvent that contains surfactants or ligands. The sudden influx triggers a burst of nucleation, after which growth proceeds as remaining precursors are consumed, enabling size control by adjusting reaction time and temperature.

The approach gained prominence in the early 2000s with the development of high-quality semiconductor nanocrystals, notably by researchers including Murray and Bawendi. Typical systems employ high-boiling solvents such as octadecene and coordinating ligands like oleylamine or trioctylphosphine oxide. Metal precursors and chalcogen sources are dissolved separately and injected quickly to initiate nucleation. Temperature is kept high during nucleation and then moderated to control growth. Variations include two-step procedures that separate nucleation and growth phases, and seed-mediated growth where initial “seed” nanocrystals are used to guide subsequent enlargement.

Advantages of hot injection include rapid nucleation, precise size tunability, and the production of monodisperse nanocrystals suitable for optoelectronic applications. Limitations involve the need for fast, careful injection and strict temperature control, as well as sensitivity to impurities and air or moisture.

Applications span quantum dots for displays and lighting, photovoltaic materials, and various nanocrystal systems such as II–VI, III–V, and some perovskites. The method remains a foundational technique in colloidal nanocrystal synthesis.