Nucleation and growth of inorganic crystals at the organic-inorganic interface

Surface-directed nucleation and oriented crystal growth have been addressed using Langmuir monolayers in contact with supersaturated mineralizing solutions. This model system has been designed to control the chemical composition, orientation, and spacing of the functional groups exposed to the mineralizing solution and to control the ionic composition, supersaturation and pH of the solution.; Light scattering microscopy (LSM) has been introduced as a novel technique to investigate early nucleation events in situ. Zwitterionic dipalmitoylphosphatidylcholine (DPPC) and negatively charged dimyristoylphosphatidylserine (DMPS) monolayers have been compared to study the role of surface chemistry on calcium oxalate crystal nucleation. A quantitative analysis of the number and apparent area of light scattering centers is presented for DPPC and DMPS monolayers. Although induction times could not be determined with LSM because of low nucleation densities, crystal growth could be directly monitored with LSM beneath DMPS monolayers.; Phospholipid monolayers in the phase coexistence region have been used to investigate the role of lattice matching on calcium oxalate crystal nucleation and growth. LSM has been combined with fluorescence microscopy to determine the location of crystals relative to the liquid-condensed (LC) and liquid-expanded (LE) phases. Light scattering centers are found at the LC domain edges for DPPC and DMPS monolayers, and the LC domains aggregate during calcium oxalate crystal growth. Boehmite crystals injected beneath DMPS monolayers migrate from the LE phase to the LC domain edges where they become trapped.; The phase, morphology, and orientation of mature calcium oxalate crystals grown beneath phospholipid monolayers have been investigated to obtain a better understanding of the molecular mechanisms controlling crystal nucleation and oriented growth. Mature calcium oxalate crystals grown beneath zwitterionic DPPC monolayers and negatively charged DMPS monolayers are oriented with respect to the monolayers but exhibit different crystal morphologies. Raman spectroscopy strongly suggests that crystals grown beneath either monolayer are calcium oxalate monohydrate (COM) crystals. Dimyristoyl-phosphatidylethanolamine, dimyristoylphosphatidic acid, eicosanoic acid, and eicosanol monolayers have also been studied to help elucidate the molecular mechanisms controlling the COM crystal orientation and morphology. The potential roles of lattice matching, hydrogen bonding, stereochemistry and electrostatics are discussed in detail.