Alexander N. Kulak

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Biominerals exhibit morphologies, hierarchical ordering and properties that invariably surpass those of their synthetic counterparts. A key feature of these materials, which sets them apart from synthetic crystals, is their nanocomposite structure, which derives from intimate association of organic molecules with the mineral host. We here demonstrate the(More)
The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by(More)
A simple synthetic method is presented for the precipitation of high purity, dry amorphous calcium carbonate (ACC) based on freeze-drying saturated, counter ion free CaCO3 solutions, where the ACC produced shows an extended atmospheric stability. Translation of the methodology to amorphous calcium phosphate demonstrates the generality of the approach.
Atomic-level defects such as dislocations play key roles in determining the macroscopic properties of crystalline materials. Their effects range from increased chemical reactivity to enhanced mechanical properties. Dislocations have been widely studied using traditional techniques such as X-ray diffraction and optical imaging. Recent advances have enabled(More)
Most of our knowledge of dislocation-mediated stress relaxation during epitaxial crystal growth comes from the study of inorganic heterostructures. Here we use Bragg coherent diffraction imaging to investigate a contrasting system, the epitaxial growth of calcite (CaCO3) crystals on organic self-assembled monolayers, where these are widely used as a model(More)
An ultraefficient cap-exchange protocol (UCEP) that can convert hydrophobic quantum dots (QDs) into stable, biocompatible, and aggregation-free water-dispersed ones at a ligand:QD molar ratio (LQMR) as low as 500, some 20-200-fold less than most literature methods, has been developed. The UCEP works conveniently with air-stable lipoic acid (LA)-based(More)
The adsorption of dye molecules from aqueous solution onto the surface of titanate nanotubes (which have been synthesized via an alkaline hydrothermal treatment) has been studied. The ionic charge on the dye molecules was found to affect their ability to adsorb onto the titanate nanotube surface. In the case of (cationic) methylene blue, the adsorption was(More)