Correlation between anisotropy and lattice distortions in single crystal calcite nanowires grown in confinement

Reconstruction of three-dimensional strain field in an asymmetrical curved core-shell hetero-nanowire

Crystal orientation and strain mapping of an individual curved and asymmetrical core-shell hetero-nanowire (NW) is performed based on transmission electron microscopy. It relies on a comprehensive analysis of scanning nanobeam electron diffraction data obtained for 1.3 nm electron probe size. The proposed approach also handles the problem of appearing twinning defects on diffraction patterns and allows for the investigation of materials with high defect densities. Based on the experimental maps and their comparison with finite element simulations, the entire core-shell geometry including full three-dimensional strain distribution within the curved core-shell NW are obtained. Our approach represents, therefore, a low-dose quasi-tomography of the strain field within a nanoobject using only a single zone axis diffraction experiment. Our approach is applicable also for electron beam-sensitive materials for which performing conventional tomography is a difficult task.

Intrinsic helical twist and chirality in ultrathin tellurium nanowires

Robust atomic-to-meso-scale chirality is now observed in the one-dimensional form of tellurium. This enables a large and counter-intuitive circular-polarization dependent second harmonic generation response above 0.2 which is not present in two-dimensional tellurium. Orientation variations in 1D tellurium nanowires obtained by four-dimensional scanning transmission electron microscopy (4D-STEM) and their correlation with unconventional non-linear optical properties by second harmonic generation circular dichroism (SHG-CD) uncovers an unexpected circular-polarization dependent SHG response from 1D nanowire bundles - an order-of-magnitude higher than in single-crystal two-dimensional tellurium structures - suggesting the atomic- and meso-scale crystalline structure of the 1D material possesses an inherent chirality not present in its 2D form; and which is strong enough to manifest even in the aggregate non-linear optical (NLO) properties of aggregates.

Crystallization in Confinement

Many crystallization processes of great importance, including frost heave, biomineralization, the synthesis of nanomaterials, and scale formation, occur in small volumes rather than bulk solution. Here, the influence of confinement on crystallization processes is described, drawing together information from fields as diverse as bioinspired mineralization, templating, pharmaceuticals, colloidal crystallization, and geochemistry. Experiments are principally conducted within confining systems that offer well-defined environments, varying from droplets in microfluidic devices, to cylindrical pores in filtration membranes, to nanoporous glasses and carbon nanotubes. Dramatic effects are observed, including a stabilization of metastable polymorphs, a depression of freezing points, and the formation of crystals with preferred orientations, modified morphologies, and even structures not seen in bulk. Confinement is also shown to influence crystallization processes over length scales ranging from the atomic to hundreds of micrometers, and to originate from a wide range of mechanisms. The development of an enhanced understanding of the influence of confinement on crystal nucleation and growth will not only provide superior insight into crystallization processes in many real-world environments, but will also enable this phenomenon to be used to control crystallization in applications including nanomaterial synthesis, heavy metal remediation, and the prevention of weathering.

Eshelby Twist as a Possible Source of Lattice Rotation in a Perfectly Ordered Protein/Silica Structure Grown by a Simple Organism

The formation mechanism of a perfectly ordered protein/silica structure in the axial filament of the anchor spicule of the silica sponge Monorhaphis chuni is suggested. Experimental evidence shows that the growth of this architecture is realized by a thermodynamically driven dislocation-mediated spiral growth mechanism, resulting in a specific rotation of the mesoscopic crystal lattice (Eshelby twist).

Liquid-crystalline calcium carbonate: biomimetic synthesis and alignment of nanorod calcite

Liquid-crystalline CaCO₃ crystals were obtained by bio-inspired crystallization through amorphous CaCO₃. These calcite nanorods were macroscopically aligned by applying mechanical force to the liquid-crystalline phase.

Liquid-crystalline CaCO₃ has been prepared for the first time. The nanorods of CaCO₃ calcite are obtained by bio-inspired crystallization through aqueous colloidal precursors of amorphous CaCO₃ stabilized by poly(acrylic acid). The synthesized calcite nanocrystals have well-tuned morphologies that are preferable for formation of liquid-crystalline phases in concentrated aqueous colloidal solution. The one-dimensional alignment of calcite crystals is achieved by mechanical shearing of the aqueous colloidal solution showing liquid-crystalline phases. These CaCO₃-based liquid crystals formed by a self-organization process in mild conditions may have great potential for use as environmentally friendly materials.