The role of nanopore shape in surface-induced crystallization.

Crystallization of a molecular liquid from solution often initiates at solid-liquid interfaces, and nucleation rates are generally believed to be enhanced by surface roughness. Here we show that, on a rough surface, the shape of surface nanopores can also alter nucleation kinetics. Using lithographic methods, we patterned polymer films with nanopores of various shapes and found that spherical nanopores 15-120 nm in diameter hindered nucleation of aspirin crystals, whereas angular nanopores of the same size promoted it. We also show that favourable surface-solute interactions are required for angular nanopores to promote nucleation, and propose that pore shape affects nucleation kinetics through the alteration of the orientational order of the crystallizing molecule near the angles of the pores. Our findings have clear technological implications, for instance in the control of pharmaceutical polymorphism and in the design of 'seed' particles for the regulation of crystallization of fine chemicals.

[1]  S. Baxamusa,et al.  Grafted Functional Polymer Nanostructures Patterned Bottom-Up by Colloidal Lithography and Initiated Chemical Vapor Deposition (iCVD) , 2009 .

[2]  Deniz Erdemir,et al.  Nucleation of crystals from solution: classical and two-step models. , 2009, Accounts of chemical research.

[3]  E. Drioli,et al.  Energetics of protein nucleation on rough polymeric surfaces. , 2010, The journal of physical chemistry. B.

[4]  M. Ward Bulk crystals to surfaces: combining X-ray diffraction and atomic force microscopy to probe the structure and formation of crystal interfaces. , 2001, Chemical reviews.

[5]  P. Vekilov,et al.  Dense Liquid Precursor for the Nucleation of Ordered Solid Phases from Solution, Crystal Growth and Design , 2004 .

[6]  S. Sharma,et al.  Effect of Interfacial Hydrogen Bonding on the Freezing/Melting Behavior of Nanoconfined Liquids , 2010 .

[7]  Mark L. Schattenburg,et al.  Large‐area achromatic interferometric lithography for 100 nm period gratings and grids , 1996 .

[8]  M. Ward,et al.  Polymorph selectivity under nanoscopic confinement. , 2004, Journal of the American Chemical Society.

[9]  C. Grant Willson,et al.  Imprint Materials for Nanoscale Devices , 2005 .

[10]  C. Jackson,et al.  Vitrification and Crystallization of Organic Liquids Confined to Nanoscale Pores , 1996 .

[11]  N. Chayen,et al.  Experiment and theory for heterogeneous nucleation of protein crystals in a porous medium. , 2006, Proceedings of the National Academy of Sciences of the United States of America.

[12]  Erik E. Santiso,et al.  A general set of order parameters for molecular crystals. , 2011, The Journal of chemical physics.

[13]  D. Frenkel,et al.  Onset of heterogeneous crystal nucleation in colloidal suspensions , 2004, Nature.

[14]  D. Frenkel,et al.  Enhancement of protein crystal nucleation by critical density fluctuations. , 1997, Science.

[15]  F. Müller,et al.  The role of prenucleation clusters in surface-induced calcium phosphate crystallization. , 2010, Nature materials.

[16]  Yang Yang,et al.  Patterning organic single-crystal transistor arrays , 2006, Nature.

[17]  Younan Xia,et al.  Monodispersed Colloidal Spheres: Old Materials with New Applications , 2000 .

[18]  Pablo G. Debenedetti,et al.  Metastable Liquids: Concepts and Principles , 1996 .

[19]  D. Frenkel,et al.  Design principles for broad-spectrum protein-crystal nucleants with nanoscale pits. , 2010, Physical review letters.

[20]  T. A. Hatton,et al.  Controlled nucleation from solution using polymer microgels. , 2011, Journal of the American Chemical Society.

[21]  Bernhardt L Trout,et al.  Surface design for controlled crystallization: the role of surface chemistry and nanoscale pores in heterogeneous nucleation. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[22]  Benjamin D. Hamilton,et al.  Manipulating crystal orientation in nanoscale cylindrical pores by stereochemical inhibition. , 2009, Journal of the American Chemical Society.

[23]  David Turnbull,et al.  Kinetics of Heterogeneous Nucleation , 1950 .

[24]  R. Sear,et al.  Crystallization controlled by the geometry of a surface. , 2009, Journal of the American Chemical Society.