Fabrication of water-soluble nanocrystals using amphiphilic block copolymer patterned surfaces

We present a simple and generalized fabrication method for monodispersed stabilizer-free water-soluble nanocrystals by confined nanocrystallization. Nanocrystallization inside well-ordered three-dimensional nanostructures involves surface-induced nucleation and confined growth of crystals. A question remains, however, as to whether the surface of concave-pit patterned substrates can induce the same confined nanocrystallization. Herein, poly(styrene-b- ethylene oxide) (PS-b-PEO) patterned surfaces having 30 nm ordered concave PEO domains were utilized as templates for confined nanocrystallization and in situ patterning. The hydrophilic characteristics of the patterned PEO nanodomains successfully provided the driving force to selectively confine hydrophilic nanocrystals within the surfaces of the domains. Nanocrystals of NaCl, fructose, 5′-guanosine monophosphate, and glycine were successfully formed and confined in the PEO domains by a simple dipping and annealing process. The dipping time, solution concentration, annealing time after dipping, and environmental conditions were the principal parameters. It was found that partially crystalline states or unique polymorphic forms resulted from the nanoconfined crystallization. The patterned individual nanocrystals could be detached from the substrate surfaces by sonication.