Heterogeneous nucleants for crystallogenesis and bioseparation

• An insight into nucleation mechanism, with a brief review of current nucleation theories.
• Description of selective nucleant approaches for controlling crystallisation.
• Essential components for successful crystallisation — the Crystallisation Triangle concept.
• Outlook of crystallisation for biocrystallisation and bioseparation.
• Emerging approaches to include soft materials.

Crystallisation is a widely used separation step for both isolation and purification of products, for a wide range of chemical processes. Nevertheless, there remains a great challenge in controlling the onset of crystallisation — nucleation. Heterogeneous nucleation has been investigated over the last three decades to determine physico-chemical relationships between nucleant and solute properties, which may be key for controlling nucleation. This can lead to rational design of nucleants facilitating selective crystallisation of particles with desired properties. In this opinion, a review on recent advances in developing mechanistic understanding of the role of interfacial properties, mainly nano-scale surface topography, surface chemistry and the combination of both features, in controlling nucleation is presented. An outlook for the development of next generation nucleants and the potential application areas are presented.

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