Exploiting the Surface Properties of Graphene for Polymorph Selectivity

Producing crystals of the desired form (polymorph) is currently a challenge as nucleation is yet to be fully understood. Templated crystallisation is an efficient approach to achieve polymorphs selectivity; however, it is still unclear how to design the template to achieve selective crystallisation of specific polymorphs. More insights into the nanoscale interactions happening during nucleation are needed. In this work we investigate crystallisation of glycine using graphene, with different surface chemistry, as a template. We show that graphene induces the preferential crystallisation of the metastable α-polymorph, compared to the unstable β-form, at the contact region of an evaporating droplet. Computer modelling indicates the presence of a small amount of oxidised moieties on graphene to be responsible for the increased stabilisation of the α-form. In conclusion, our work shows that graphene could become an attractive material for polymorph selectivity and screening, by exploiting its tunable surface chemistry.