Nucleation and Growth of Colloidal Semiconductor Nanoparticles

Abstract

Solution‐phase syntheses of semiconductor nanoparticles provide a versatile and scalable approach to obtain nanomaterials with desirable structure and function. The most common mechanism invoked to explain the nucleation and growth of colloidal semiconductor nanocrystals is the LaMer model, an extension of classical nucleation theory. This model is widely used to conceptualize the conversion of molecular precursors into nanoparticles, and is characterized by three stages: monomer buildup, nucleation, and particle growth. Each of these stages represents a fundamental aspect of nanoparticle synthesis, and each has been widely studied over the past several decades. One of the core successes of this model has been the prediction of the “burst nucleation” method, which has enabled the synthesis of monodisperse nanoparticles in many material systems. Increasingly, however, it has become apparent that many chemical systems do not follow classical nucleation theory, but rather grow via nonclassical cluster‐mediated or aggregative growth processes. Regardless of the nucleation mechanism, highly monodisperse semiconductor nanoparticles can be obtained through kinetic size focusing or digestive ripening. Kinetic size focusing occurs during the nanoparticle growth phase when monomer concentration is high and smaller particles grow faster than their larger counterparts, enabling the smaller particles to “catch up” in size to give a more monodisperse ensemble. Digestive ripening, on the other hand, is a postsynthetic strategy where additional ligand is provided to the system to etch larger particles and redistribute monomer to smaller particles to get a more uniform sample. Beyond the synthesis of spherical colloidal nanoparticles, procedures can be modified to achieve a range of anisotropic structures including 1D nanorods and 2D nanosheets. Seeded and templated growth strategies can lend additional synthetic flexibility to more easily access a range of complex architectures. Continued innovation in synthetic methods and mechanistic understanding will pave the way for technological translation and lasting impact across applications from biological imaging to catalysis and many other next‐generation technologies.

Analysis of the atomic structure of CdS magic-size clusters by X-ray absorption spectroscopy

“…a system is not monodisperse). The latter is a consequence of the classical nucleation and growth process 14 .…”

“…The latter is a consequence of the classical nucleation and growth process. 14 However, it has recently been found that during the nucleation process, persistent optical absorption peaks appear and remain sharp. [15][16][17][18][19][20][21][22][23][24][25][26][27] Their peak position and width suggest that they originate from ultra-small particles of identical size (i.e.…”