Early stages of non-classic crystal growth

Investigation of early stages of crystal growth revealed that crystal growth in some systems may not follow the classic route. In the early stages of inorganic crystal growth, precursor molecules and/or nanocrystallites may aggregate into large and disordered particles with the assistance of some polymers or biomolecules. Surface crystallization of these aggregates would then take place to form shells with high crystallinity and density, followed by an extension of the crystallization from surface to core. This so-called reversed crystal growth mechanism has been found in crystallization of several inorganic compounds including zeolites, perovskites, metals and metal oxides, and will be identified in more material systems. The establishment of this new crystal growth route gave us more freedom to control the morphology of crystals and to understand the formation mechanism of many natural minerals. This article gives a brief review of the recent research in this field by featuring some typical examples of the reversed crystal growth.