Ubiquitous crystals play an important
role in our daily lives.
Recent studies on the properties and formation of crystals have proven
the attachment of particles ranging from ion pairs to well-crystallized
nanocrystals for crystallization. Compared with the monomer-by-monomer
(i.e., atoms, ions, or molecules) addition described in long-standing
classical theories, so-called nonclassical crystallization pathways
are more complex due to the influence of nonspecific interactions
influenced by the variation in system free energy and reaction kinetics.
In view of the fact that detailed insights into nonclassical crystallization
pathways have broadened the scope of research across various disciplines
such as geological events, biomineralization mechanisms, environmental
remediation, and the development of functional materials, this paper
reviews the current state of the art in nonclassical nucleation (the
prenucleation clusters pathway, aggregation pathway, etc.) and growth
pathways (oriented attachment and random attachment) based on several
highlights. In addition, the observed specific phenomena on crystallization
in the last 10 years as well as recent advancements and achievements
on the synthesis of mesocrystals are also elucidated. With implications
and perspectives of nonclassical crystallization research proposed
in this paper, this review aims to summarize research advancements
regarding crystallizing systems. Emphasis will be placed on novel
insights into nonclassical crystallization of materials, which are
expected to provide completely new perspectives on the underlying
crystallization mechanisms.
